Transcript Essential Nutrients

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)
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
 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
 Leptin: hormone, suppresses appetite
Glucose Homeostasis