Lecture AP Biology Chapter 41 Animal nutrition

WARM-UP
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:
1. Ingestion: eating
2. Digestion: breakdown of food into small

molecules
 Mechanical (chewing, grinding)
 Chemical (enzymes)

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
Digestion of Macromolecules:
 Mouth = carbs
 Stomach = proteins
 Small Intestine = carbs, proteins, fats, nucleic
acids

Digestion in the Mouth
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)
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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



Digestion in the Small Intestine
 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)



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