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TRANSCRIPT
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AP Biology
2005-2006AP Biology
Chapter 41.
Animal Nutrition
2005-2006AP Biology
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??