Lecture AP Biology Chapter 41 Animal nutrition

After studying this chapter you will be able to: Name the three nutritional needs that must be met by an animal’s diet; describe the four classes of essential nutrients; distinguish among undernourishment, overnourishment, and malnourishment; describe the four main stages of food processing.

1 (Ch 40) What is the principle of countercurrent

exchange?

2 (Review) What are the 4 classes of macromolecules?

3 (Ch 41) You eat a piece of candy List the structures

it passes through as it travels through your

alimentary canal.

4 Where does most of the digestion of the candy in #3

happen?

Chapter 41: Animal Nutrition

What you need to know:

 Major compartments of alimentary canal

(organs) – and their contributions to animal nutrition

 Digestive glands: salivary, pancreas, liver,

gall bladder – and their contributions to

animal nutrition

 Digestion of carbs, proteins, fats, nucleic

acids

Essential Nutrients : required by cells, obtained through food

 Four classes of essential nutrients:

Essential amino acids (8)

Essential fatty acids

Vitamins (13) - fat-soluble, water-soluble

Minerals

Dietary Deficiencies

 Undernourished: diet is deficient in calories,

not enough energy

 Malnourishment: missing 1+ essential nutrients

Herbivore licks exposed salts and minerals lacking in plants.

The main stages of food processing:

3. Absorption: cells take up nutrients

4. Elimination: pass undigested materials from

digestive system

Digestive Compartments

 Most animals process food in specialized compartments

 Intracellular: digestion of food inside cells by food

vacuoles

 Ex phagocytosis, pinocytosis, sponges

 Extracellular: food broken down outside of cells

 Gastrovascular cavity (simple) or alimentary canal (complex)

Intracellular Digestion: Sponges

Extracellular Digestion

 Compartments are outside of the animal’s body

 Gastrovascular cavity : simple animals;

single-opening, two-way digestion (food in, waste out)

Digestion in a hydra

 Alimentary canal: more complex, one-way tubes with mouth and anus

Specialized organs for digestion in Humans

 Digestive system = alimentary canal + glands

 Glands = salivary glands, pancreas, liver, and gallbladder

Q: Can you name the organs of the human

alimentary canal in order?

 Peristalsis: push food through rhythmic

contractions of muscles in the wall of the canal

 Sphincters : valves regulate the movement of

material between compartments

 Oral cavity: mechanical, chemical digestion

 Salivary glands: saliva lubricates food

 Teeth chew food into smaller particles

 Salivary amylase: breakdown glucose polymers

 Saliva contains mucus, a viscous mixture of

water, salts, cells, and glycoproteins

 Pharynx: back of throat

 Epiglottis: flap of cartilage, covers trachea when

swallowing

 Esophagus: food tube (pharynx  stomach)

Digestion in the Mouth

Digestion in the Stomach

 The stomach stores food and secretes gastric

juice, which converts a meal to acid chyme

 HCl: pH 2, kills bacteria & denatures proteins

 Pepsin: enzyme (protease) that hydrolyze

proteins into smaller peptides

 Pepsinogen (inactive)  pepsin (active) by HCl

 Mucus: protects lining of stomach

 Gastric ulcers: lesions in the lining, caused mainly

by bacterium Heliobacter pylori

 SI = major organ of digestion and absorption

 Duodenum: first section, digestive juices, major chemical digestion

 Digestive juices:

 Pancreas: bicarbonate (basic), trypsin &

chymotrypsin (proteases); lipase (fats);

amylase (carbs); nuclease (DNA, RNA)

 Bile: made in liver, stored in gall bladder

 Emulsify fats (make smaller droplets)

Digestion in the Small Intestine

Hormones that coordinate

digestion:

Gastrin: produced by stomach,

production of gastric juices

Entrogastrin: produced by SI (duodenum),

peristalsis to allow time for fat digestion

Secretin & CCK (cholesystokinin):

secreted by SI (duodenum), flow of

digestive juices from pancreas & gall bladder

Absorption in the Small Intestine

 Villi and microvilli increase surface area

 Villi  capillaries  hepatic portal vein  liver 

heart

 Liver: distribute nutrients, detox, glucose storage

(glycogen)

Absorption in the Large Intestine

 LI = colon

 Function = compact waste,

reabsorb water

 Cecum : pouch where SI & LI

meet, ferment plant material

 Appendix = extension of

cecum, role in immunity

 Rectum: end of LI, feces

stored until elimination

Evolutionary adaptations of vertebrate digestive

systems correlate with diet

 Dentition: teeth correlate with diet

 Herbivores: longer alimentary canal, longer

cecum

Mutualistic Adaptations

 Many herbivores have fermentation chambers,

where mutualistic microorganisms digest

cellulose (ruminants)

Homeostatic Mechanisms

 Vertebrates store excess calories as glycogen

in the liver and muscle cells, and as fat in

adipose tissue

 Overnourishment can lead to obesity

Glucose Homeostasis