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Chapter 41.

Animal Nutrition

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Nutritional requirements

� Animals are heterotrophs

� need to take in food

� Why? fulfills 3 needs…� fuel = chemical energy for production of ATP

� raw materials = carbon sources for biosynthesis

� essential nutrients = substances animals cannot make themselves� elements (N, P, K, Fe, Na, K, Ca, etc.), NAD, FAD, etc.

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Energy budget

food intake

ATPproduction

biosynthesis

• basal (resting) metabolism

• activity• temperature

regulation

• growth• reproduction

{{

storage• glycogen• fat{

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Energy budget

� The flow of food energy into & out of an animal can be viewed as a “budget”

� if animal takes in more calories than it needs to produce ATP, “bank” the rest

� excess used for biosynthesis & storage� growth in size

� reproduction

� stored in energy deposits

This obese mouse (L) has

defect in gene which normally produces an

appetite-regulating protein

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Energy storage

� In humans

� store as glycogen� glucose polymer

� storage in liver & muscle cells

� If glycogen stores are full & caloric intake still exceeds caloric expenditure

� excess stored as fat

Why isglycogen highlybranched?

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Managing caloric intake

� When fewer calories are taken in than are expended, fuel is taken out of

storage deposits & oxidized (digested)

� breakdown glycogen from liver & muscle cells

� metabolize (digest) fatJust do it!

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Regulation: Maintaining Homeostasis

� Balancing glucose levels in blood

pancreas

pancreas

insulin

glucose storage

glucose uptake

glucose release

depress appetite

stimulatehungerglucagon

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Managing glucose levels� Human body regulates the use & storage of

glucose, a major cellular fuel

� insulin reduces blood glucose levels� when glucose levels rise above set point,

pancreas secretes insulin

� promotes transport of glucose into cells & storage of glucose as glycogen in liver & muscle cells

� dropping blood glucose levels

� glucagon increases blood glucose levels� when glucose levels drop below set point,

pancreas secretes glucagon

� promotes breakdown of glycogen & release of glucose into the blood

� increasing blood glucose levels

Whoa! Didn’t realizeI was sobusy!

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Nutritional requirements

� Fuel for ATP production

� Raw materials for biosynthesis

� source of N & P

� to make complex molecules = proteins, nucleic acids

� need complex molecules animals cannot synthesize

� amino acids, vitamins

� need minerals

� iron, calcium, etc.

Many herbivores have diets

deficient in mineral salts. Must find other sources =

salt licks, chewing on bones

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Vegetarian diets

� 8 essential amino acids

� what about the other 12? we can synthesize them!

� Possible amino acid deficiency can be avoided by eating foods with complementary amino acids

� beans & grains

PB&J anyone?rice & beans?pasta & beans?tofu & rice?

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Essential Nutrients

� What happens if an animal’s diet is missing an essential nutrient?

� deficiency diseases

� scurvy — vitamin C (collagen production)

� rickets — vitamin D (calcium absorption)

� blindness — vitamin A (retinol production)

� anemia — vitamin B12 (coenzyme function)

� kwashiorkor — protein

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Essential vitamins (coenzymes)

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Essential vitamins (coezymes)

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Essential minerals (cofactors)

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Dietary regimes

� All animals eat other organisms

� Herbivores� eat mainly autotrophs (plants, algae)

� gorillas, cows, hares, snails

� Carnivores� eat other animals

� sharks, hawks, spiders, snakes

� Omnivores� consume animals & plants or algae

� cockroaches, bears, raccoons, humans

� humans evolved as hunters, scavengers & gatherers

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Feeding adaptations

suspension feeding substrate feeding

fluid feeding bulk feeding

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Food processing� Ingestion

� eating

� Digestion

� breaking food down into molecules small enough for the

body to absorb

� enzymatic hydrolysis

� Absorption

� animal cells take up small

molecules

� Elimination

� undigested material passes of

digestive system

intracellulardigestion

extracellulardigestion

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Digestive systems

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Mammalian digestive system

� Alimentary canal

� peristalsis

� push food along by rhythmic waves of smooth muscle contraction in walls of digestive canal

� sphincters

� muscular ring-like valves, regulate the passage of material between specialized chambers of digestive canal

� Accessory glands

� salivary glands, pancreas, liver & gall bladder

� secrete digestive juices (enzymes & fluid)2005-2006AP Biology

Human digestive system

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Swallowing

� Mouth ingests

� mechanical digestion & chemical digestion of starch

� Epiglottis

� closes trachea when swallowing

� problem: breathe & swallow through same orifice

� Esophagus

� moves food to stomach by peristalsis2005-2006AP Biology

Ingestion

� Mouth, pharynx & esophagus

� physical & chemical digestion of food

� trigger reflexive release of saliva from salivary glands, containing:

� mucin

� slippery glycoprotein

� protects soft lining of mouth from abrasion &

lubricates food for easier swallowing

� buffers

� help prevent tooth decay by neutralizing acid in mouth

� antibacterial agents

� kill bacteria that enter mouth with food

� amylase

� digests starch & glycogen

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Throat

� Pharynx

� junction that opens to both esophagus &

trachea (windpipe)

� swallowing

� top of windpipe moves up so opening = glottis blocked by cartilaginous flap = epiglottis

� ensures that food will be guided into entrance of esophagus & not directed down windpipe

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Stomach� Food storage

� can stretch to fit ~2L food & fluid

� Digestion

� gastric juice

� digestive fluid secreted by epithelial lining

� HCl

� pH 2

� breaks down matrix binding cells

� kills bacteria

� pepsin

� breaks down proteins

� secreted as pepsinogen

� mucus

� protects stomach lining

What stopsthe stomachfrom digesting

itself?

Oooooooh…zymogen!

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�Bacteria-stomach feedback interactions

� H. pylori bacteria colonize stomach

� bacterial infection

� causes damaging

inflammation

� increases stomach

acidity

� high rate of ulcer &

stomach cancer

� control with

antibiotics

Helicobacter pylori

inflammation of stomach

inflammation of esophagus

Colonized byH. pylori

Free of H. pylori

white blood cells

cytokines

inflammatory proteins(CagA)

cell damaging proteins(VacA)

helper T cells

neutrophil cells

H. pylori

Coevolution of parasite & host

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Revolutionizing healthcare"for their discovery of the bacterium Helicobacter pylori and its role

in gastritis and peptic ulcer disease"

J. Robin Warren

Barry Marshall

1982 | 2005

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Small intestine

� Major organ of digestion & absorption

� over 6 meters!

� 3 sections

� duodenum = most of digestion

� jejunum = absorption of nutrients & water

� ileum = absorption of nutrients & water

� absorption throughlining of intestines

� small intestine has hugesurface area = 300 m2

(roughly size of tennis court)

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Duodenum

� Acid material from stomach mixes with digestive juices from glands:

� pancreas, liver, gall bladder & glandular cells of intestinal wall

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Pancreas � Digestive enzymes

� peptidases� trypsin

� trypsinogen

� chymotrypsin

� chimotrypsinogen

� carboxypeptidase

� procarboxypeptidase

� amylase

� Buffers

� lowers pH� alkaline solution rich in

bicarbonate (HCO3-)

� buffers acidity of material from stomach

Explain how this is a

molecular example of structure-function theme.

What stopsthe pancreasfrom digesting

itself?

Ooooooh…zymogens!

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Digestive enzymes

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Liver

� Many functions in body

� digestive system

� production of bile� stored in gallbladder until needed

� act as “detergent” to help digest & absorb fats

� circulatory system

� toxin & damaged red blood cell removal

� bile contains pigment by-products of RBC

� bile pigments eliminated from body with feces

� brown feces = rusty iron from hemoglobin!

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Absorption

� Villi

� increase surface area

Explain how this is a structural example of

structure-function theme

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Absorption of Nutrients

� Passive

� fructose

� Active (protein pumps)

� pump amino acids, vitamins & glucose

� against concentration gradients across intestinal cell membranes

� allows intestine to absorb much higher proportion of nutrients in the intestine than would be possible with passive diffusion

� worth the cost of ATP!

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Large intestines (colon)

� Reclaiming water

� used as solvent for various digestive juices

� ~7L of fluid secreted intodigestive tract daily

� > 90% of water reabsorbed

� diarrhea = insufficient

water absorbed

� constipation = too much

water absorbed

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Flora of large intestines

� Living in the large intestine is a rich flora of mostly harmless bacteria

� Escherichia coli

� a favorite research organism

� bacteria produce vitamins

� vitamin K; biotin, folic acid & other B vitamins

� generate gases

� by-product of bacterialmetabolism

� methane, hydrogen sulfide2005-2006AP Biology

Rectum

� Terminal portion of colon

� Feces contain

� masses of bacteria

� undigested materials, mainly cellulose

� roughage or fiber

� salts

appendix

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Structural adaptations

� Structural variations reflecting diet have made mammals very successful

� differences in teeth

� length of digestive system

� number & size of stomachs

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Teeth

� evolutionary adaptation

of teeth for processing

different kinds of food

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Length of digestive system

� Herbivores & omnivores

� long digestive systems

� harder to digest cellulose (cell walls)

� Carnivores

� short digestive systems

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Digesting cellulose

� How well you digest cellulose governs life strategy of herbivores

starch vs. cellulose

position of glycosidic linkage governs digestibility

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Cow

can digest cellulose well; no need to eat supplemental sugars

Gorilla

can’t digest cellulose well; must supplement with sugar source, like fruit

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Symbiotic organisms

� How can cows digest cellulose efficiently?

� symbiotic bacteria & protists help digest cellulose-rich meals of herbivores

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Any Questions??