[GR] Answers to End of Chapter Textbook Questions

So the corrected sentence could be: When a plant cell is placed in a concentrated sugar solution, water moves out of the cell by osmosis, through the partially permeable cell membrane..

Answers to end-of-chapter questions

All sample answers were written by the authors

3 a A chloroplast is an organelle that contains the

pigment chlorophyll (A chloroplast is surrounded

by two membranes Folded membranes inside

the chloroplast have molecules of chlorophyll

on them.) Photosynthesis takes place inside

chloroplasts, with the help of chlorophyll, which

absorbs energy from light

b All cells have a cell membrane, which is a thin layer

of protein and lipid that surrounds the cell and

controls what enters and leaves it Plant cells (and

bacterial cells) also have a thicker layer surrounding

them In plant cells, this is made of cellulose Cell

membranes are partially permeable Cell walls are

fully permeable

4 a

• be drawn with unbroken lines (no gaps in the line)

• have the correct proportions

• show each structure accurately and clearly [5]

b Measured diameter on diagram = 36.5 mm

actual size = image size ÷ magnification

= 60.8 mm (or 6.08 or 6.1 cm)

5 a A cell wall;

b they have cell walls;

c i Measured diameter on image = 20.5 mm [1]

(Note: the measurement depends on where the

outer limit of the cell is considered to be It should

be the middle point of the two cell walls around the adjacent cells If the measurement has been made from cell membrane to cell membrane,

it will be 19.1 mm If it has been made from the midpoints of the triangle of extracellular space at each corner, it will be 21.1 mm.)

ii actual size = image size ÷ magnification

Chapter B2 Movement in and out of cells

1 a Osmosis Water is at a high water potential (dilute

solution) in the soil and at a lower water potential (concentrated solution) inside the root cells It moves through the partially permeable cell membrane, down its water potential gradient

b Neither In this case, all the molecules in the saliva

move as one, like water flowing in a river Both diffusion and osmosis involve the random, individual movement of molecules or ions

c Diffusion The ink particles move randomly, bumping

into each other and into the water particles, gradually spreading throughout the water

d Diffusion The carbon dioxide particles move

randomly, and some will ‘bump into’ a stoma

in the underside of the plant leaf There is a low concentration of carbon dioxide inside the leaf, because the plant uses it up very quickly in photosynthesis The carbon dioxide diffuses down its concentration gradient, from the air into the leaf

2 a The sugar solution as a whole does not do anything

We need to think about the individual particles in the sugar solution – the water molecules and the sugar molecules Both of these move about randomly The water molecules can get through the tiny holes in the tubing, but the sugar molecules are too big What will happen is that the water molecules will move

randomly back and forth through the holes Because

there are more of them in the water than in the sugar

solution, their net movement will be into the tubing

So the corrected sentence could be:

If Visking tubing containing a sugar solution is put

into a beaker of water, water will move from the

water into the sugar solution, by osmosis

b It is true that plant cells do not burst in pure water,

but this is because the cell wall is strong enough

to prevent this happening The cell wall is fully

permeable, and cannot stop water molecules going

through it So the corrected sentence could be:

Plant cells do not burst in pure water because,

although water enters the cell by osmosis, the strong

wall prevents the cell from bursting

c It is true that water will move out of a plant cell

by osmosis, if the cell is placed in a concentrated

sugar solution However, the cell wall is not partially

permeable – it is fully permeable So the corrected

sentence could be: When a plant cell is placed in a

concentrated sugar solution, water moves out of

the cell by osmosis, through the partially permeable

cell membrane

d Plasmolysis is the result of placing a plant cell in

a concentrated sugar solution So much water

moves out of the cell by osmosis that the contents

shrink, and the cell membrane pulls away from

the cell wall As animal cells do not have a cell

wall, they cannot undergo plasmolysis So the

corrected sentence could be either:

Animal cells shrink when placed in a concentrated

sugar solution OR

Plant cells plasmolyse in a concentrated sugar solution

3 a Diffusion is a result of the random movement of

molecules or ions At higher temperatures, these

have more kinetic energy and move faster, so

diffusion happens faster

b During daylight, plants photosynthesise They

produce oxygen in their leaves, so the oxygen

concentration inside the leaf is higher than the

oxygen concentration in the air outside Oxygen

therefore diffuses down its concentration gradient,

from the leaf and into the air

c Visking tubing is a partially permeable membrane It

has tiny, molecule-sized holes in it Water molecules

are even smaller than the holes, so they can pass

through Sugar molecules are much bigger than the

holes, so they cannot pass through

d When it is placed in pure water, an animal cell

absorbs water by osmosis This is because there is a higher water potential outside the cell than inside it The extra water makes the cell swell, until it bursts

e Plant cells are held in shape by their full vacuoles,

which push outwards against the strong cell wall, producing a very firm structure A plant cell like this

is said to be turgid Turgid cells pressing against each other make plant tissues strong and firm When the cells are not full of water, they are no longer turgid, and their contents do not press outwards on the cell wall The cells, and the tissues in the leaves that they make

up, become soft and floppy This is why the plant wilts

4 a the movement of molecules / ions, down a

concentration gradient / from a high concentration

to a low concentration;

as a result of their random movement; [2]

60 50 40 30 20 10 0

iv C’s concentration was between A and B;

specific evidence quoted to support this statement, e.g it took less time for it to travel 10 cm than A and

b table is drawn with a ruler and has rows and columns

for dimensions of block and time taken to go colourless;headings for both quantities include correct units – including time / s;

times to go colourless are correctly recorded as 128

c i diffusion; [1]

ii hydrochloric acid neutralised the alkaline

substance in the agar / the pH became less

d block B had a greater surface area to volume ratio /

the distance for diffusion to the centre of the block

Chapter B3 Biological molecules

1 a monosaccharide, found in both plants and animals,

used as fuel in respiration

b polysaccharide, found in plants only, used as an

energy store in plant cells

c polysaccharide, found in plants only, used to make

cell walls

d polysaccharide, found in animals only, used as an

energy stores in (liver) cells

2 a nitrogen (or sulfur)

b amino acids

c Benedict’s

d lipid (fat) sucrose

e sucrose

f metabolism or metabolic reactions

3 Measure equal volumes of each solution into two

identical test tubes

Add equal volumes of Benedict’s solution to each one

Place both tubes into a water bath at about 80 °C Do this

at exactly the same time Watch carefully The one that

changes to green or orange first, or the one that is the

darkest orange after a set length of time, is the one that

has the most concentrated solution of reducing sugar

haemoglobin C, H, O, N protein biuret test carries

oxygen in the blood glucose C, H, O carbohydrate Benedict’s

test to provide energy starch C, H, O carbohydrate iodine test stores

energy in plant cells enzyme C, H, O, N protein biuret test speeds up

reactions

5 a a protein catalyst, which speeds up the rate at which

metabolic reactions take place

b a term used to describe the state of a protein

molecule that has lost its shape – often caused by high temperature or extremes of pH; a denatured enzyme molecule is unable to catalyse its reaction because the substrate no longer fits into its active site

c the substance that is changed into products by

an enzyme; the substrate fits into the enzyme’s active site

d a new substance formed in an enzyme-catalysed

reaction

e the part of an enzyme molecule into which a

substrate molecule fits

6 a About 37 °C – human body temperature.

b About 2 – hydrochloric acid has a very low pH.

c At low temperatures, molecules have low kinetic

energy and move slowly This means that the frequency of collisions between enzyme molecules and substrate molecules is also low

d Above the enzyme’s optimum temperature, the

enzyme molecule begins to lose its shape – it is denatured This means that the substrate molecule does not fit into the active site, so the enzyme cannot catalyse the change of the substrate into products

d orange-brown;

b the blue-black colour would have disappeared

c i Time /

had been a reaction

Total number of areas where there had been a reaction

time on x-axis and number of new areas on y-axis;

scales on both axes go up in even steps (e.g 1, 2,

3 etc on x-axis, 10, 20, 30 etc on y-axis); both axes

fully labelled including units; all points accurately

plotted with small, neat crosses or circles with a

ring around them; straight lines drawn between

the points / good best-fit line drawn; [5]

iii any two sensible suggestions about differences

between the goats, e.g different ages, different

genders, different breeds, different concentrations

of enzyme in their saliva, how hungry they were

when the saliva was collected; [2]

d continue for longer; take readings more often than

one minute intervals; include some discs that have

no enzyme in them / have boiled enzyme in them;

repeat the experiment two more times; [max 3]

9 a sucrose molecules and enzyme molecules move

randomly; sucrose molecule collides with enzyme’s

active site; enzyme causes sucrose molecule to split

into glucose and fructose; reference to involvement

of water in this reaction; products / glucose and

fructose, leave the active site; [max 3]

b i optimum temperature for enzymes; temperature

kept constant because, pH is the independent

variable / temperature is a control variable; [2]

ii no activity below pH 3; optimum / greatest

activity, is at pH 7; no activity above pH 11; [3]

Chapter B4 Plant nutrition

and proteins

maintaining turgor / supporting tissues, transporting substances

Carbon

2 a A chloroplast is an organelle that contains the

pigment chlorophyll Photosynthesis takes place inside chloroplasts, with the help of chlorophyll, which absorbs energy from light

b The palisade mesophyll is closer to the upper surface

of the leaf than the spongy mesophyll The cells in the palisade mesophyll are tall and thin, while the cells in the spongy mesophyll are more rounded The palisade cells contain more chloroplasts than the spongy cells More photosynthesis takes place in palisade cells than in spongy cells There are larger air spaces in the spongy mesophyll than in the palisade mesophyll

c Organic substances have been made by living

organisms, e.g carbohydrates, proteins, vitamins Inorganic substances have not been made by organisms, e.g magnesium ions, water

d Guard cells are pairs of sausage-shaped cells found in

the epidermis of leaves (usually in the lower epidermis) The hole in between the pair of guard cells is a stoma

3 a carbon dioxide + water → glucose + oxygen

b Carbon dioxide enters the leaf through stomata, by

diffusion from the air Water enters the root hairs, by osmosis from the soil and is then transported up the xylem to the leaf

c Glucose is used to make starch, or to provide energy

by respiration Oxygen diffuses out of the leaf into the air, through the stomata

4 a Carbon dioxide diffuses through the stoma and then

through the air spaces, allowing it to reach the cells

in the palisade layer Oxygen diffuses in the opposite direction when photosynthesis is taking place (When you have learnt about transport in plants, you will also find out that the air spaces are important for allowing the movement of water vapour out of the leaf.)

b This means that light can pass straight through

these cells, so little light is lost before it reaches the palisade cells, where it is used in photosynthesis

c The larger the surface area, the more sunlight will

hit the leaf This means that more energy can be absorbed by chlorophyll, so more photosynthesis can take place

d The veins bring water from the soil to the leaf cells

By branching, they can bring water close to every cell The cells need water for photosynthesis, and

to maintain their turgor, helping the leaf to be held out straight

5 a sucrose This is a soluble sugar, which can dissolve in

water for transport It is not too reactive

b starch This is an insoluble polysaccharide, which

can be stored as solid grains in cells and will not

interfere with the reactions that take place in the cell

(It also does not affect the water potential of the cell;

if sucrose was stored, this would tend to draw excess

water into the cell by osmosis.)

6 a Leaf from plant A: all orange-brown;

Leaf from plant B: uncovered part blue-black;

b i to break down the cell membranes so that iodine

solution and starch can come into contact; [1]

c i cover other areas with a simlar material that is

transparent (so that the only difference is whether

ii it controls a significant variable – having different

plants could affect the results / because one

plant might respond differently from another; [1]

d use a plant with variegated leaves;

destarch it;

then leave in the light long enough for it to make starch;

test a leaf for starch;

would expect green parts to go blue-black, white

b i little light is lost before it reaches the palisade

cells, where it is used in photosynthesis; [1]

ii the waxy cuticle prevents water loss through this

iii bring water to the leaf; take sucrose away from

the leaf; help to support the leaf [max 2]

ii some is used in respiration to release energy;

some is converted to starch for storage; some is

used to make cellulose cell walls for new cells;

some is converted to sucrose for transport to

other parts of the plant; some is converted, with

the addition of nitrogen, to amino acids; some is

converted to, fats / lipids [max 4]

Chapter B5 Animal nutrition

b There is a very wide range of possible answers

Images B5.02 to B5.04, and Tables B5.02 and B5.03, provide some examples Answers can also be checked against a table of nutrient values of foods Search on the internet for: 'food nutrient content table' and select one that covers foods commonly eaten in the relevant country

2 a Digestion is the breaking down of large food

molecules into small ones Absorption is the movement of these small molecules through the wall

of the small intestine and into the blood

b The small intestine is longer and narrower than the

large intestine It is made up of the duodenum and ileum, whereas the large intestine is made up of the colon and rectum Digestion and absorption of all types of food molecules – including water – takes place in the small intestine Only water absorption takes place in the large intestine

c Enamel is the exceptionally hard outer layer of a tooth

Dentine is a softer layer beneath the enamel. Dentine contains living cells, but enamel does not

d Bile is a greenish liquid made in the liver and stored

in the gall bladder, whereas pancreatic juice is made

in the pancreas Both liquids flow along ducts into the duodenum Bile contains bile salts, which are not enzymes but which help to emulsify fats (break large droplets into small ones) Pancreatic juice contains several different digestive enzymes that digest fats, proteins and carbohydrates Both bile and pancreatic juice also contain sodium hydrogencarbonate, which neutralises the acid from the stomach

b they all already are small molecules; which can

pass through the walls of the ileum; [2]

d helps calcium to be absorbed; needed for making,

e anaemia; lack of energy;

iron is needed to make haemoglobin;

which transports oxygen around the body;

lack of oxygen means less respiration; [max 3]

6 a A incisor;

B canine;

b tooth A: cut off pieces of food; to help with ingestion;

tooth C: crush / grind, food; to increase surface area

c

diagram shows a molar tooth;

correct labels to:

iii rows 2, 3 and 4 show sugar absent, starch absent

and sugar absent;

rows 5, 6, 7 and 8 show starch absent, sugar

present, starch absent, sugar present; [2]

ii results show there is sugar in the water in the

beaker;

so sugar molecules have moved through the

membrane;

sugar molecules are small enough to pass

through the holes in the membrane; [2]

c i small intestine / duodenum / ileum; [1]

ii blood / blood plasma / capillaries; [1]

d its molecules are too big to be absorbed / to pass

through the wall of the small intestine; [1]

8 a breakdown of large / insoluble molecules;

iii line is of similar shape;

d to produce molecules that are small enough to be

absorbed / because starch molecules are too large

2 a and b root hairs liquid

xylem liquid

leaf mesophyll cells liquid

air spaces in leaf gas

3 a a section cut across something

b, c and d

b as wind speed increases, water uptake increases;

any use of manipulated figures (e.g doubling of wind

speed from 2 to 4 metres per second results in 1.7

times the rate of water uptake); [2]

c light intensity; temperature; humidity; [max 2]

5 a i more root hairs;

ii both show same increase in number of root hairs

(per unit area);

decrease in length of root hairs is (much) greater

iii less surface area;

so less uptake of mineral ions / water;

so less photosynthesis;

less glucose / starch / carbohydrate synthesised;

so less fuel for respiration / less energy available;

less nitrate reduces protein synthesis; [max 3]

b so plants can make more amino acids / proteins;

Chapter B7 Transport in animals

1 a vena cava, right atrium, right ventricle, pulmonary

artery, lungs, pulmonary vein, left atrium, left ventricle, aorta

b vena cava, right atrium, right ventricle, pulmonary artery

2 a Arteries take blood away from the heart; veins take

blood towards the heart Arteries have thick, elastic walls; veins have thinner walls Arteries have a narrow lumen; veins have a wider lumen Arteries do not have valves; veins have valves

b Oxygenated blood contains a lot of oxygen

(combined with haemoglobin inside the red blood cells) and is bright red Deoxygenated blood contains less oxygen, and is a duller purplish-red

c An atrium is one of the upper chambers of the

heart, which receives blood and which has thin walls A ventricle is one of the lower chambers of the heart, which has thick walls that pump blood out of the heart

d A red blood cell is a small cell with no nucleus,

indented, and containing a large amount of haemoglobin Its function is to transport oxygen There are several types of white blood cells, but most are larger than red blood cells and they all have a nucleus They do not contain haemoglobin Their function is to fight pathogens

• Veins: valves to keep low-pressure blood moving in one direction; wide lumen to provide least resistance

to blood flow

• Capillaries: very narrow, so red blood cells have

to squeeze through and are brought close to cells that require oxygen; very thin walls with gaps, so substances can easily move between blood and tissue fluid

• Xylem vessels: dead and hollow so nothing in the way

of water movement; narrow, so a tall column of water

can be supported without breaking; lignin in walls to

make them waterproof and to provide strength; pits

in walls to allow water to move sideways

• Phloem tubes: living but with no nucleus and only

a small amount of cytoplasm, so sap can flow

through; perforated end walls to allow sap to flow

through

5 a contains haemoglobin that combines with oxygen;

collects oxygen in lungs, releases it in body tissues; [2]

b protects against, disease / pathogens;

takes in and kills micro-organisms / bacteria /

pathogens; [2]

c to deliver requirements to body cells; e.g oxygen /

glucose / other named nutrient; to remove waste

products from body cells; e.g carbon dioxide /

6 a Red cell in diagram measures 23 mm;

ii it contains haemoglobin; which combines

reversibly with oxygen; it has a large surface area

to volume ratio; which speeds up the movement

of oxygen into and out of the cell; it is small; which

allows it to squeeze through very small capillaries;

it has no nucleus; which makes more room for

d when the ventricle contracts, the valve shuts; because

of the pressure of the blood pushing upwards on it;

when ventricle relaxes, valve opens; [3]

e line follows the same pattern as the first, at the same

times, but does not rise to such a high volume; [2]

c coronary (arteries); plaques / cholesterol / fat

deposit, in artery wall; partly blocks artery; less blood can flow through; less oxygen carried to heart muscle; increased likelihood of blood

d to keep the blood moving; to keep the blood

oxygenated; to remove carbon dioxide from the

e has a septum dividing the two sides of the heart;

oxygenated blood on the left and deoxygenated on the right; both sides contract at the same time; more muscle on the left side; so more pressure produced

on the left side; high pressure to most of body; low

Chapter B8 Gas exchange and respiration

1 a protein synthesis, cell division, growth, movement,

passage of nerve impulses, maintaining a constant body temperature

b respiration

c glucose + oxygen → carbon dioxide + water

2 a inspired air has more oxygen; inspired air has less

carbon dioxide; inspired air usually has less water vapour

b Oxygen is used by body cells in respiration Carbon

dioxide is produced by body cells in respiration Water evaporates from the lining of the lungs into the air, so it is breathed out in expired air

3 a the movement of oxygen into the body and the loss

of carbon dioxide

b the alveoli in the lungs

b any three of: large surface area; thin; good supply of

air containing oxygen; good blood supply

4 a anaerobic

b both

c aerobic only in humans; both in yeast

d both

5 The following sequence should be shown, in a diagram or

words: down trachea, bronchus, bronchiole, into alveolus (by mass flow of air), across wall of alveolus into the blood,

by diffusion into a blood capillary into a red blood cell, combines with haemoglobin, carried along the pulmonary vein to the left atrium of the heart then to the left ventricle, pumped out of the heart into the aorta, then to a capillary

in the arm muscle, diffuses out of the red blood cell, diffuses out of the capillary, diffuses into the muscle cell

6 a i to make sure all the carbon dioxide had been

ii carbon dioxide present;

dissolves / reacts with water;

e more rapid breathing brings fresh air into the lungs

more often; deeper breathing brings a larger volume

of fresh air into the lungs; more oxygen can diffuse

into the blood more quickly; supplying more oxygen

to the muscles; so they can respire faster; releasing

f brain senses the pH of blood; pH decreases during

exercise; because more carbon dioxide is dissolved

in the blood plasma; brain responds by sending more

frequent impulses to the breathing muscles; so they

contract harder and more frequently; [max 4]

8 a 12.5 breaths per minute at start, 25 breaths per

minute during exercise; so increase is 12.5 breaths

b from just before 11 minutes to just before 16 minutes;

c during exercise not enough oxygen was supplied

to muscles; so they respired anaerobically (as well

as aerobically); producing lactic acid; which was

broken down by combining with oxygen (when

exercise finished); reference to paying back the

d would follow a pattern similar to that of breathing rate;

heart pumps oxygenated blood to the muscles; more

oxygen required by muscles as they exercise; so that

they can respire faster; more carbon dioxide needs to be

removed from the muscles; continuing need for more

oxygen after exercise to pay off oxygen debt; [max 4]

9 a axes correctly labelled; x-axis scale uses the ranges

from the table; good scale on both axes that uses

most of the graph paper provided; each bar drawn

b the more cigarettes smoked per day, the greater the

chance of dying between the ages of 40 and 60 years old;

the younger a person is when they start smoking, the

greater the chance of dying between the ages of 40 and 60 years old;

the number of cigarettes smoked per day seems

to increase the chance of dying between 40 and 60 more than the age at which smoking started; [3]

Chapter B9 Coordination and homeostasis

1 a a reflex action

b The stimulus from the sharp object is detected by

a receptor in the foot This sends an electrical impulse along a sensory neurone to the brain or

spinal cord The impulse is passed along a relay neurone and then to a motor neurone This

transmits the impulse to an effector, the muscles in

your leg, and makes them contract

2 a motor and relay

4 a Keeping the body temperature constant is just one

part of homeostasis, which is the maintenance of a constant internal environment Homeostasis also involves the regulation of blood glucose concentration,

as well as the water content of the body

b The hairs do stand on end when the body is too cold,

but in humans we do not have enough hair for this to help to keep us warm In other hairier mammals, the raised hairs trap a layer of insulating air next to the skin

c Air of any kind cannot get into the body through the

skin The fat layer prevents heat leaving the body by conduction, as it is an insulator

d The sweat glands do secrete sweat onto the surface

of the skin when we are too hot, but this liquid is not cold It cools the body because the water in the sweat evaporates, and this process takes heat energy from the skin

e The blood capillaries do not move at all The

arterioles that supply the blood capillaries near the

surface of the skin get wider (dilate) when you are too

hot This allows more blood to flow through these

capillaries, allowing heat to radiate from the blood

into the air

f Insulin is a hormone, not an enzyme Enzymes

catalyse reactions, but insulin is not a catalyst

Insulin causes enzymes in liver cells to convert

glucose to glycogen

5 a A 37.4 °C;

b homeostasis; humans are endothermic; body

produces more heat to maintain body temperature;

c air is more insulating than water; heat lost more

easily from the body in water than in air; by

d person A was moving but person B remained

still; idea that ‘new’ cold water was constantly

coming into contact with A’s skin; water around

B’s body warms up (as heat is lost from his body to

the water); heat transfers from hot object to cold

object; so more heat lost from A’s body than B’s

6 a for respiration; by combining it with oxygen to

provide energy; (not ‘produce’ energy) for named

function (e.g movement, active transport); [max 3]

c i starch digested to glucose; by enzymes / amylase

and maltase; absorbed into the blood from, the

ii insulin secreted; causes liver to take up glucose

from the blood; liver converts glucose to

glycogen; (also) glucose used by body cells in

d negative feedback is a process that brings

concentration back to normal when it gets too high

or too low; when blood glucose concentration rises

too high, insulin is secreted and reduces it to normal;

when blood glucose concentration drops too low,

glucagon is secreted and raises it to normal; [3]

7 a ability to detect changes in the environment;

ii better access to water;

leaves have more light;

iii builds up on the lower side;

causes cells in stem to elongate more;

causes cells in root to elongate less; [3]

Chapter B10 Reproduction in plants

2 Asexual reproduction Sexual reproduction

only one parent involved all offspring genetically identical

one or two parents involvedinvolves gametes

involves fertilisation zygote formed genetic variation among offspring

b i young plants will get light for photosynthesis; [1]

they have water;

they have a suitable temperature;

c i tropism;

ii better photosynthesis;

because leaves can get more light;

flowers held up higher;

5 a asexual; [1]

b produces new banana plants that are identical to

the parent (so the bananas will be exactly the same

variety); produces large new plants quickly; [2]

c all new plants will be genetically identical; if the

parent did not have resistance to the disease then

Chapter B11 Reproduction in humans

b It produces amniotic fluid, in which the fetus floats

This fluid protects it from bumps and knocks

c The placenta brings the mother’s and fetus’s blood

close together, but does not allow them to mix In

the placenta, useful substances such as oxygen and

glucose diffuse from the mother’s blood to the fetus’s

blood Wastes such as urea and carbon dioxide

diffuse from the fetus’s blood to the mother’s blood

3 a i they are haploid / they have only one set of

chromosomes; [1]

ii it contains food stores for the developing embryo;

[1]

iii the food stores will soon run out; (once attached)

it obtains nutrients; and oxygen; from the

mother’s blood; through the placenta; [max 4]

b i A umbilical cord;

B amnion;

ii the (beating of the) fetus’s heart; [1]

iv mother to fetus: any two of oxygen / glucose

/ amino acids / water / other named soluble

nucleus

all five labels correct three marks four labels correct two marks

two or three labels correct one mark [3]

b acrosome contains enzymes which digest through

the jelly surrounding the egg; mitochondria release energy by aerobic respiration (for swimming); flagellum propels the sperm forwards; nucleus contains the haploid number of chromosomes so the normal diploid number is restored at fertilisation; shape is streamlined to reduce energy needed

c nucleus contains the haploid number of

chromosomes so the normal diploid number is restored at fertilisation; it contains food stores to provide for the young fetus (until it is implanted); it is surrounded by a protective layer of jelly; [3]

5 a increased and then decreased; peaks in 2004 and

2007; any figure quote using both year and number of people infected read from the graph; [3]

b people recently infected with HIV show no symptoms;

may not have had their blood checked; [2]

c more awareness of AIDS; people with HIV/AIDS now

knew that they had it and avoided passing it on; people who were not HIV positive modified their behaviour to reduce the risk of becoming infected with HIV; example – avoided having multiple partners / used condoms / did not share contaminated needles; use of antiretroviral drugs to treat AIDS;

Chapter B12 Inheritance

1 a a large letter for the smooth fur allele and a matching

small letter for the rough fur allele, using letters that look different from each other, e.g A and a (not S and s)

b AA, Aa and aa

c AA smooth fur, Aa smooth fur, aa rough fur

2 a a large letter for the red colour allele and a matching

small letter for the white colour allele, using letters

that look different from each other, e.g R for the red

colour allele and r for the white colour allele

b R is dominant, because this is the allele that has

an effect in a heterozygous plant

c RR, red; Rr, red; rr, white

3 a A gene is a length of DNA that codes for a particular

protein; an allele is one of two or more forms of a gene

b A dominant allele shows its effect in a heterozygous

organism; a recessive allele only has an effect when

no dominant allele is present

c A homozygous organism has two identical alleles

of a gene, e.g AA; a heterozygous organism has two

different alleles of a gene, e.g Aa

d The genotype shows the alleles of a gene that an

organism possesses; the phenotype describes the

characteristics of the organism

e Mitosis is a type of nuclear division in which

genetically identical daughter cells are produced;

meiosis is a type of nuclear division that produces

daughter cells with only half the full number of

chromosomes, and that are genetically different from

one another Mitosis is used in growth, repair and

asexual reproduction; meiosis is used to produce

gametes

f A haploid cell has one full set of chromosomes; a

diploid cell has two full sets

4 a symbols should be the same letter, large and small,

and easily distinguishable, e.g

EE for indented edges;

b parents’ phenotypes indented smooth

parents’ genotypes EE ee

gametes E e

spring genotypes all Ee

and phenotypes indented

parents’ genotypes correct;

gametes correct and placed inside circles;

offspring genotype and phenotype correct;

entire genetic diagram laid out correctly with

all headings; [4]

spring genotypes and phenotypes

parents’ genotypes correct; all gametes correct

and shown inside circles; genotypes of offspring correct; phenotypes of offspring correctly associated with genotypes; 99 : 302 is approx 3 : 1 and genetic diagram shows 3 indented : 1 smooth; [5]

5 a i white is dominant and himalayan is recessive – no

ii parents’s genotypes shown as Aa and Aa (or

whatever letters have been chosen in part a);

gametes from both parents shown as A and a

with circles around them;

offspring genotypes shown as AA, Aa, Aa and aa;

AA and Aa offspring identified as white, and aa as

himalayan;

ratio stated as 3 : 1 white to himalayan and

matched to three quarters white and one quarter himalayan; [5]

b i respiration;

ii air trapped between hairs;

insulation;

iii extremities / ears/ paws / nose, colder than other

parts of the body;

enzyme active only in these parts so black

Chapter B13 Variation and natural selection

1 species, discontinuous, genes, continuous, mutation,

adapted

2 a In continuous variation, an individual can

fit anywhere within a range of a particular

characteristic, with no sharp dividing lines In

discontinuous variation, there are a small number of

distinct categories into which any individual fits

b Natural selection is the increased chances of

individual organisms with particular variations

surviving and reproducing in their environment,

because of selection pressures that act on them

Artificial selection is the choice, by humans, of

individuals with particular variations to be allowed to

breed together

3 a Sexual reproduction allows mixing of alleles from

different parents There is genetic variation in the

population Different combinations of alleles may

give different features that make some individuals

better able to survive and reproduce in the

changing environment than their parents Asexual

reproduction, however, produces offspring with

exactly the same combinations of alleles as their

parent; there is no genetic variation

(In both sexual and asexual reproduction, mutation

may occur, which could form new alleles that might

give an advantage to an organism and be selected

for This is no more likely in sexual than in asexual

reproduction.)

b Mutation may produce new alleles that were not present

before Although mutations usually produce new

characteristics that are less good than the normal ones,

just occasionally a new feature that gives an organism

a survival advantage may occur If so, then this will be

selected for (its owners will be more likely to survive and

reproduce) and passed on to the next generation

4 a correct answer given (you will need to get someone

b i shape of ear lobes shows discontinuous variation;

ii approximately 3 : 1; free : attached; [2]

iii allele for free ear lobes likely to be dominant;

and allele for attached ear lobes likely to be

recessive; [2]

5 a i There are no distinct categories; individuals

can have any wing length within the range from

63 mm or less to 70 mm or more; [2]

ii for example: body mass / body length / beak

length; [1]

b i the largest number of birds trapped has wing

lengths of 66 or 67 mm; suggesting that most birds had these wing lengths; comparative data quoted for birds with these wing lengths and others; birds with these wing lengths had greater mean ages when trapped; suggesting that they lived longer than others; comparative age data quoted for birds with these wing lengths and others; [max 4]

ii repeat measurements for a larger number of

birds; repeat in countries other than Sweden; check wing lengths of birds that are breeding; follow individual marked birds throughout their lives to measure wing length and length of life; measure the wing length of dead birds; [max 3]

c birds with this wing length survive for longer; more

likely to reproduce than birds with smaller wings; wing length determined by genes / alleles which are

Chapter B14 Organisms and their environment

1 a A producer is an organism that makes its own

organic food materials from inorganic ones; plants are producers, as they make organic nutrients by photosynthesis A consumer is an organism that depends on organic nutrients made by producers; animals and fungi are consumers

b A primary consumer obtains its energy by feeding

on plants; it is a herbivore A secondary consumer obtains its energy by feeding on primary consumers;

it is a carnivore

c A food chain shows how energy is transferred from

one organism to another, showing only one species

at each trophic level A food web shows many interlinking food chains, with more than one species shown at each trophic level

2 a to make carbohydrates, fats and proteins

b by photosynthesis; carbon dioxide from the air is

used to make carbohydrates

c They are given out from the plant as carbon dioxide.

d They break down carbohydrates, fats, proteins and

other carbon-containing materials in dead organisms

or waste products from them; they then respire, giving out carbon dioxide to the atmosphere

ii movement / muscle contraction; active transport;

generating heat to keep the body warm;

transmission of nerve impulses; building large molecules from small ones; [max 3]

c i the food web should show an arrow going from

the wildebeest to ticks, another arrow going from

the ticks to the oxpeckers; and an arrow going

from the wildebeest to the oxpeckers; [1]

ii energy is lost between trophic levels; 90% of

energy lost / only 10% of energy passed on; lost,

in respiration / as heat; so fewer organisms can

be supported at each trophic level; [max 3]

4 a photosynthesis by aquatic plants; dissolving from

b bacteria feed on the sewage; so their populations

increase; bacteria respire; aerobically; use up oxygen

c i increasing quantities of untreated sewage running

into the river; build-up of nutrients in the water;

so larger bacteria populations used up more

ii sewage treated before entering the river; fewer

nutrients for bacteria; so fewer bacteria / less use

e cause unpleasant smells; introduce pathogens

to the water that could cause disease in humans; e.g. cholera bacterium; e.g polio virus; other example

of water-borne disease-causing organism; [max 2]

ii that natural rain water is slightly acidic [1] /

from dissolved carbon dioxide [1] / after

thunderstorm more acidic because of

2 a use cobalt chloride paper – turns from blue to pink;

or use anhydrous copper sulfate powder – turns from

b as a coolant, or any other correct industrial use [1]

c a substance that dissolves another to form a

e 1: filtration to remove solid particles [2]

2: chlorination to kill bacteria/germs [2]

3 a lower proportions of oxygen and nitrogen; higher

b acid rainfall causing damage to trees [1] /

c add drops of the liquid to anhydrous copper(II)

sulfate powder (1); powder turns from white to

blue (1)

OR

add drops of the liquid to cobalt chloride paper (1);

colour change from blue to pink (1) [2]

Chapter C2 The nature of matter

1 a Both ways of categorising substances have their use

to a chemist

• Knowing whether a substance is a solid, liquid

or gas at room temperature – and how easily

a substance can change its state – helps us in handling the different substances and in separating them and purifying them from mixtures It is important to realise that any substance can exist in any of the three states, depending on the conditions of temperature and pressure

• Knowing whether a sample is an element, compound

or mixture helps us in knowing and predicting the chemical properties of a substance These distinctions are mutually exclusive and therefore are more fundamental to our understanding

b The word ‘particle’ is needed when talking in

generalisations about the structure and movement

of the constituents of matter The context should always be defined to distinguish this scientific use

of the word from the more everyday use when it can be a speck of dust, etc The one key experiment where the two uses interact is in the description of Brownian motion

Here the unseen motion of atoms and molecules in

a fluid is demonstrated by the jerky, random motion

of the dust particles as they are hit by the microscopic particles that make up matter

One aspect that can be discussed, and needs to

be referred to, is the key definition of the size of the ‘particles’ involved when the term is used Descriptions such as ‘sub-microscopic’ and

‘subatomic’ are useful

2 a i The particles are in fixed positions [1]; they vibrate

about their fixed position [1] [2]

ii Add water, stir to dissolve salt and filter to obtain

b distillation, lower, volatile, condenser, vapour [5]

d The particles are close together but irregular [1];

the molecules are able to move about with slow

e i The third statement is correct: its melting point is

different from pure stearic acid [1]

ii in testing medicines or food additives, or other

correct [1]

ii The third statement is correct: helium has a

complete outer shell of electrons [1]

b P has 2 protons and 2 neutrons (= 4 nucleons) [1]

c atoms are electrically neutral because they have

equal numbers [1] of protons

d R [1]

Chapter C3 Elements and compounds

the Group number is given by the number of

outer electrons in the atom [1] [2]

ii Q is the least reactive as it is a noble gas [1]

iii P is a good conductor of electricity as it is a

metal [1]

4 a i D

ii E iii F

iv B

v A [5]

b i Correct electron structure of the F ions (electrons

from outer orbit of C moved to the two F atoms,

one electron to each to give eight electrons in

Correct charges on each ion: – on F and

ii high melting point, soluble in water, conducts

when dissolved or molten, brittle (any two of

5 a i X conducts electricity, Z does not; or X reacts

ii An electron is transferred (donated) from a

sodium atom to a chlorine atom [1]; the sodium becomes a positive ion and the chlorine a

Chapter C4 Chemical reactions

1 a There is a colour change which shows that there

might be a reaction, and new substance(s) are formed / a gas is given off

b The most reliable evidence for a chemical reaction

is that a gas is given off which can be identified as carbon dioxide

c copper carbonate → copper oxide + carbon dioxide zinc carbonate → zinc oxide + carbon dioxide

d Zinc oxide is a white solid which turns yellow when

heated When cooled, the solid turns white again

e No, it is a physical change.

2 a black solid [1]

b magnesium + carbon dioxide

→ magnesium oxide + carbon [1]

ii Magnesium reduces zinc ions [1] by donating/

3 a sulfur + oxygen → sulfur dioxide [1 for reactants;

b SO2 is oxidised to SO3 and O3 is reduced to O2 [2]

4 a aqueous sodium chloride, copper, graphite

[deduct 1 for each incorrect answer] [3]

ii negative = zinc [1] ; positive = chlorine [1] [2]

5 a carbon/platinum [1] because unreactive [1] [2]

b bubbles [1] at both electrodes [1] [2]

c hydrogen at cathode [1], chlorine at anode [1] [2]

Chapter C5 Acids, bases and salts

c i to help plants grow better (or words to that

effect) [1]

ii sulfur dioxide [1] from power stations [1] or

nitrogen oxides [1] from car exhausts [1]; dissolves

ii Measure the calcium hydroxide/alkali with a

pipette [1], add indicator [1] and add acid from

burette until there is a colour change [1] [3]

2 a pH 3 [1]

b Add blue (or neutral) [1] litmus [1]; if it turns red, it is

c i calcium carbonate + hydrochloric acid → calcium

chloride + carbon dioxide + water [1 mark for each

ii in a blast furnace for producing iron [1]

iii lime/calcium oxide, or slaked lime/ calcium

3 Step 2: Filter to remove excess solid [1]

Step 3: Evaporate to crystallisation point [1]

Step 4: Leave solution to cool [1]; dry crystals on filter

4 a i ammonia gas is produced by the reaction [1];

ammonia turns moist red litmus blue [1] [2]

ii no reaction if solid is ammonium nitrate [1] white precipitate if solid is ammonium

b calcium carbonate reacts with acids [1]; calcium

carbonate will neutralise acidic soil [1] [2]

5 a acidic: < 7, any appropriate e.g SO2 basic: > 7, any appropriate e.g CaO neutral: 7, any appropriate

b i an oxide/substance that will react with/ dissolve

ii any strong acid (e.g HCl) + any strong alkali

Chapter C6 Quantitative chemistry

1 a ammonia + sulfuric acid → ammonium sulfate [1]

number of moles H2SO4 = 980 / 98 = 10 moles [3]

b i molar mass of CaO = 56 g/mol [1]

number of moles CaO = 168 / 56 = 3 moles [1] [2]

ii molar mass of H2O = 18 g/mol

Chapter C7 How far? How fast?

1 The methods used to prevent explosions from ‘runaway

reactions’ are precisely the opposite to those changes

that would speed up the rate of reaction The changes

used would need to have a ‘dampening’, or inhibitory,

effect The following changes would all result in a

slowing down of a reaction:

• lowering the temperature

• adding water to dilute the reactants (see Workbook

Exercise 7.6 for an example)

• lowering the pressure of a gas reaction

Other methods are also possible

2 a hydrated iron sulfate

→ anhydrous iron sulfate + water [1]

b endothermic [1]; heat has to be applied (or words

d It is a reversible reaction [1], hydrated iron sulfate

is formed [1] and heat is also generated (reaction

exothermic) which produces steam [1] [3]

f If water is added to anhydrous cobalt chloride [1], it

changes colour from blue to pink [1] [2]

ii X placed at the beginning of the curve (see graph

iii sketch graph to the right of the printed curve [1]

and levelling out above it [1] [2]

4 a amount of manganese(Iv) oxide and temperature [2]

b i the higher the concentration, the faster the

ii A lower concentration will produce less oxygen [1]

c magnesium oxide, copper(II) oxide, manganese(Iv)

5 a i fair test [1]; keep the amount of solution above

ii value for gap: between 120 and 150 [1]

iii speed decreases [1] because lower concentration

[1] means fewer collisions [1] [3]

b The reaction is faster [1] because higher temperature

makes particles move more rapidly [1]; this means more collisions [1] and harder/more energetic

ii (maximum volume of gas) 40 cm3 at reaction time

of 5 minutes / 300 s (1);

average rate = 40 ÷ 5 = 8 / 40 ÷ 300 = 0.13 (1); units: cm3 / minute or cm3 / s (1) [3]

c i in aqueous (solution) / dissolved in water / in

solution; [1]

ii same mass / length / size / amount of magnesium

used in both experiments (1);

acid in excess / all magnesium used up in both (1); gas volume produced depends on amount of

Chapter C8 Patterns and properties of metals

1 a Alloys are metals whose composition is designed

to suit the properties required by a particular use

or situation Properties which have been significant

in the development of alloys have included:

• tensile strength

• hardness

• resistance to corrosion

• electrical conductivity

• low melting point

• colour

b Brass is used in plugs and switches because, even

though it is not as good a conductor as copper, it is

cheaper and harder It is more resistant to hard wear

and regular use

2 a i copper, zinc, magnesium, calcium [1]

ii Iron does not react with cold water [1] but it does

react with steam when heated [1] [2]

b zinc + water → zinc oxide + hydrogen [1]

c high melting point/boiling point, malleable, conduct

heat, conduct electricity (any three) [3]

iii any sensible answer above 0.53 g/cm3 and below

1.0 g/cm3 (it floats on water) [1]

3 a i lithium + water → lithium hydroxide + hydrogen

[2]

b lithium reaction not exothermic enough to melt

the metal, sodium and potassium melt into a ball,

potassium ignites spontaneously order of increasing

reactivity Li<Na<K all float on water, all fizz and

produce hydrogen, all leave an alkaline solution

c i anode: E [1]; electrolyte: A [1] [2]

ii positive = chlorine; negative = sodium [2]

d low melting point, soft/can be cut with knife,

electrical conductivity, etc (any two) [2]

brown deposit (of copper) (on metal X) (1) [2]

ii X is less reactive than magnesium / magnesium

c i removal of oxygen / gain of electrons [1]

ii metal ions have a positive charge (1); cathode

has a negative charge and opposite charges

Chapter C9 Industrial inorganic chemistry

1 Although there are some cases where recycling has

significant economic advantages in terms of costs (for example, the recycling of aluminium), this is not always the case The most important argument for recycling is the conservation of natural resources, particularly non-renewable resources of minerals and fuels, for instance The impact of efficient recycling can be wide-ranging The demand for rare metals for the electronics and media industries puts great pressure on the need to find new mineral resources and the development of new mining ventures This can bring conflicts with environmental concerns in some of the most untouched areas of the world Efficient recycling could delay some

of these potential clashes of interest

c ammonium sulfate + calcium hydroxide → ammonia

+ water + calcium sulfate products or ‘double decomposition’ [2]

3 a A: yes will rust, has air and water [1];

B: no, has air but no water [1];

C: no, has air and water but protected/coated with

b carbon burned off by oxygen as carbon dioxide [1];

phosphorus, etc., react with calcium oxide/lime to

Carbon monoxide reduces hematite to iron

Limestone decomposes to calcium oxide and carbon dioxide

Calcium oxide (lime) reacts with silica to form slag.

(two equations plus three other points of description) [5]

ii They react together to form calcium phosphate,

which is a solid, and form slag, which floats on

b so that the ions are free to move [1]

c to lower the operating temperature by lowering the

melting point of the electrolyte [1]

b copper is less reactive than iron / bonding in copper

oxide is weaker (1); less energy needed to break

c limestone is added to the blast furnace (1); limestone

decomposes in the furnace to give calcium oxide /

lime (1); silicon dioxide reacts with calcium oxide to

produce slag / calcium silicate (1) [3]

Chapter C10 Organic chemistry

1 The versatility of carbon lies in its ability to form chain

and ring structures, and to form multiple bonds with

itself and other atoms The complexity that arises is

important to us in several different ways:

• the chemistry of life and the interactions between

carbon-containing molecules that generate the

energy for living cells and the way of passing genetic

information from one generation to the next

• the carbon-containing compounds – from fossil

fuels – that are the fuels of our modern transport and

energy-generating systems

• the synthetic and natural polymers that provide us with food, clothing and structural materials that support our living and the technologies we depend on

• the novel structures that provide the scope for developing nanotechnology

2 a i hydrogen and carbon contain just one type

of atom; compounds contain different atoms bonded together

elements are listed on the Periodic Table;

ii draw a central C with four hydrogens attached

b i Z [1]

ii X, Z unsaturated molecules contain double bonds [2] iii pass the gas through bromine water [1]; an

unsaturated hydrocarbon will decolorise the bromine water [1], a saturated hydrocarbon will

3 a a family of organic compounds with similar chemical

properties due to the presence of the same

b A = alkene; B = alkane; C = alcohol [3]

c test: bromine water; A: decolorises; B: no effect [3]

d heat it with steam [1] and a catalyst [1] [2]

c the boiling point of the alkanes increases with

the size of the molecule (1); the larger (longer) the molecule the greater the forces (interactions / inter-molecular forces) between the molecules (1); more energy is needed to disrupt/break/overcome

mass of methane burnt = 0.02 x 16 = 0.32 g (1) [3]

Chapter C11 Petrochemicals and polymers

1 The products of burning methane, ethanol and fuels

such as gasoline are the same – the question is more

one of the efficiency and our ability to use the fuels

cleanly Methane and ethanol are single compounds

but gasoline is a mixture of hydrocarbons and more

difficult to burn completely Incomplete combustion

gives rise to pollution with carbon monoxide, soot and

particulates

Ethanol is more environmentally friendly because it is/

can be a renewable fuel Any carbon dioxide released can

be at least partially removed from the atmosphere as (for

example) the sugar cane used in fermentation is grown

Methane is more environmentally friendly as it produces

less carbon dioxide for the amount of energy it releases

as it has the best/highest carbon : hydrogen ratio

2 a i hydrogen and carbon

(each) contains one type of atom / is found in

the Periodic Table / cannot be broken down into

simpler substances;

propane

contains different atoms (or elements) bonded

together / can be broken down into simpler

iv heating / lighting / burners / cooking / vehicle

fuel / refrigerant / feedstock [1]

ii only single bonds (in a molecule) / contains

maximum possible hydrogen atoms [1]

iv structure of ethene: draw two C linked by a

double bond, four H attached by single bonds

3 a i structure of ethene: draw two C linked by a

double bond, four H attached by single bonds

ii molecule contains at least one C=C double bond;

does not contain the maximum possible number

b i many ethene molecules join together to make a

long chain; draw a series of units joined together

[2]

b fuel oil – fuel for home heating; kerosene – jet fuel;

lubricating fraction – waxes and polishes; naphtha –

ii a substance that speeds up a reaction [1]

5 a i a group of hydrocarbons with boiling points

b heating and cooking; fuel for cars [2]

c molecules contain a double bond; a compound of

H

C H

(at least) three monomer units shown (1); correct

sequence (1); amide links shown (1) [3]