Synthesis and decomposition material

Overview of photosynthesisLight Chloroplast Light reactions Calvin cycle NADP++++ ADP + P • The light reactions convert solar energy to chemical energy – Produce ATP & NADPH • The Cal

1 Photosynthetic plants

2 Photosynthetic bacteria

3 Chemoautotrophic bacteria

Light Energy Harvested by Plants

6 CO 2 + 6 H 2 O + light energy → C 6 H 12 O 6 + 6 O 2

Photosynthesis takes place within leaf (or green stem) cells containing chloroplasts

• each cell contains 40 to 50 chloroplasts

• a chloroplast has dozens of the thylakoids and millions of pigment molecules

• each thylakoid contains thousands of photosystems

Where the Photosynthesis Occurs?

The thylakoid membrane of the chloroplast is impregnated with photosynthetic pigments

Thylakoid

There are three basic steps in photosynthesis:

(1) Light Reactions - energy capture

(2) Dark Reactions - fixation of carbon

Overview of photosynthesis

Light

Chloroplast

Light reactions

Calvin cycle

NADP++++

ADP + P

• The light reactions

convert solar

energy to chemical

energy

– Produce ATP & NADPH

• The Calvin cycle makes

sugar from carbon dioxide

– ATP generated by the light

reactions provides the energy for

sugar synthesis

– The NADPH produced by the

light reactions provides the

electrons for the reduction of

carbon dioxide to glucose

reactions cycle

• Chloroplasts contain several pigments

Chloroplast Pigments

– Chlorophyll a

– Chlorophyll b

– Carotenoids

Chlorophyll a & b

•Chl a has a methyl group

•Chl b has a carbonyl group

Porphyrin ringdelocalized e-

Phytol tail

Different pigments absorb light differently

What is the comparison between c3 plant and c4 plant also,c4 plant and

CAM?

C3 plants

• oldest form of carbon fixation

• 95% of current plants use c3 fixation

• carbon fixation and photosynthesis occurs exclusively in the mesophyll cells

• least efficient form of photosynthesis (more RUBISCO than RuBP favors oxygen rather than the uptake of CO2)

• the stomata of the plant are open all day to uptake CO2,

allowing release of H20, oxygen, etc

C4 plants

• later adaptation of carbon fixation

• carbon fixation takes place in the mesophyll cells and the

resulting oxyloacetate moves to the bundle sheath cells for

photosynthesis

• mesophyll cells are packed with PEP which favors CO2 uptake

so stomata need only be opened for part of the day

• more efficient method, even though it requires more energy

• both fixation and photosynthesis take place in mesophyll cells

• carbon fixation is temporally separated from photosynthesis and only takes place at night

• stomata open at night, oxyloacetate is kept until daytime when

it is used in the calvin cycle (photosynthesis)

• same equation as c4 plants, high energy expenditure, but

necessary for succulent plants in desert where risk of

transpiration of water is too high during day

Bacteria Photosynthesis

Thiorhodaceae Chlorobacteriaceae

Athiorhodaceae

Structure of Cyanobacteria

A is not O

Bacteria Photosynthesis

• Only one photosystem can not do photolysis of

H2O

• H22O not the source of electron donor

• O2 never formed as a product

• Bacterial chlorophyll absorb light at longer

• Similar CO2 fixation

• Only has cyclic photophosphorylation

• Some bacteria use O2 in the air to oxidize

inorganic compounds and produce ATP (energy)

material needed for cell growth.

Chemoautotrophic bacteria

Chemosynthesis near hydrothermal vents

Chemoautotrophic bacteria

Nitrifying bacteria in the soil under our feet!

Aerobic respiratory organisms

Aerobic respiration is the release of energy from food in cells using oxygen.

Aerobic Respiration

Glycolysis is the breakdown of glucose

resulting in the formation of pyruvic acid.

The three steps in aerobic respiration are glycolysis,

Kreb's cycle, and electron transport chain

Reaction of aerobic respiratory

C6H12O6 + O2 CO2 + H2O

ATP

pyruvic acid

glucose

series of enzyme-controlled reactions

Overview of Aerobic Respiration

pyruvic acid

series of enzyme-controlled reactions

requires oxygen

pyruvic acid

series of enzyme-controlled

requires oxygen

Breakdown of Pyruvic Acid

enzyme-controlled reactions

oxygen

pyruvic acid

36 ADP + 36 Pi

In the presence of

Production of ATP during breakdown of pyruvic acid

36 ATP

oxygen

Stages of aerobic

respiration

Number of ATP molecules

Anaerobic Respiration Organisms

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In the absence of oxygen, glucose cannot be

broken down into carbon dioxide and water.

Therefore, glucose is only partly broken down and only a few molecules of ATP are released

Anaerobic Respiration in Animals

only a few molecules of ATP are released

Anaerobic respiration is the breakdown of glucose

in cells in the absence of oxygen.

is converted

to lactic acid

pyruvic acid

lactic acid

No ATP molecules are

formed.

Stages of anaerobic

respiration

Number of ATP molecules

Anaerobic Respiration in Plants and Yeast

glucose

2 ADP + Pi

2 ATP pyruvic acid

ethanol

No ATP molecules are

formed.

carbon dioxide

+

Aerobic respiration

Anaerobic Animals

Anaerobic Plants/Yeast

Comparing Aerobic and Anaerobic Respiration

Lactic acid Ethanol and

carbon dioxide

Fermentation

Fermentation pathways

a Homolactic acid fermentation

Pyruvic axit -> Lactic Acid

eg Streptococci, Lactobacilli

b Alcoholic fermentation

Pyruvic axit -> Ethyl alcohol

eg yeast

Fermentation pathways

Fermentation Organisms

Roles of the decomposition process

Decomposition is a complex process involving a variety of

organisms

Decomposers are organisms that feed on dead organic

matter or detritus

Involves the release of energy and ultimately the

conversion of organic compounds into inorgarnic nutrients

Complex of many process: leaching, fragmentaion,

changes in physical and chemical structure, ingestion and excretion of waste products