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Chapter 41 - Animal Nutrition
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I. Types of Digestion- mechanical &
chemical breakdown of food into
smaller molecules that can be absorbed
by the cells

A. intracellular◦ 1. digestion inside a cell
◦ 2. occurs when a lysosome w/digestive
enzymes merges w/ a food vacuole
◦ 3. ex: paramecium

B. extracellular digestion –
◦ 1. food digested in a gastrovascular cavity
◦ 2. then absorbed by individual cells
◦ 3. most animals use this process
II. Nutrition – determined food
need

A. Organic cmpds.
◦ 1. carbohydrates a. contain CHO
 b. broken down into glucose to be used as a
supply of energy
 c. ex: sugars, starches

2. lipids – fats
◦ a. saturated – all carbons bonded with single
bonds, mostly from animals, solid at room
temp
◦ b. unsaturated – some carbons have double
bonds, mostly from plants, liquid at room
temp
◦ c. used for energy storage, protection,
insulation, cell membrane
◦ d. broken down into glycerol & fatty acids

3. proteins
◦ a. made of amino acids – your body breaks
them down into these aa’s & makes new
proteins with them
◦ b. animal products provide all necessary aa’s
◦ c. plant products lack some…(vegans?)

4. nucleid acids – broken down into
nucleotides
◦ a. nucleotide = sugar, phosphate, &
nitrogenous base
◦ b. only 2 in the known universe – DNA & RNA
5. vitamins – organic cmpds needed in
minute amts to help body use other
nutrients appropriately
 *6. inorganic cmpds –

◦ a. minerals –
 1) don’t contain carbon
 2) needed in minute amts
B. Nutritional requirements





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1. Undernourishment: caloric deficiency
2. Overnourishment (obesity): excessive
food intake
3. Malnourishment: essential nutrient
deficiency
4. Essential nutrients: materials that
must be obtained in preassembled form
5. Essential amino acids: the 8 amino
acids that must be obtained in the diet
6. Essential fatty acids: unsaturated fatty
acids
Nutritional requirements
III. Feeding mechanisms

A. Opportunistic
◦ 1. Herbivore: eat autotrophs
◦ 2. Carnivore: eat other animals
◦ 3. Omnivore: both

B. Feeding Adaptations
◦ 1. Suspension-feeders: aka filter feeders - sift
food from water (baleen whale)
◦ 2. Substrate-feeders: live in or on their food
(leaf miner) (earthworm:
deposit-feeder)
◦ 3. Fluid-feeders: suck fluids from a host
(mosquito)
◦ 4. Bulk-feeders: eat large pieces of food (most
animals)
Suspension, substrate, fluid, or bulk????
IV. Food processing

A. overview
◦ 1-Ingestion: act of eating
◦ 2-Digestion: process of food break down
 a. enzymatic hydrolysis
◦ 1) intracellular: breakdown within cells
(sponges)
◦ 2) extracellular: breakdown outside cells (most
animals)
 b. alimentary canals (digestive tract)
◦ 3- Absorption: cells take up small molecules
◦ 4- Elimination: removal of undigested material
B. Mammalian Digestion (human)

1. Mouth--food is masticated in the mouth
◦ a. mixed with saliva which contains amylase
 1) enzyme that begins the chem breakdown of
starch into maltose (disaccharide)
 2) food is shaped into a ball or bolus swallowed

2. Pharynx – bolus passes through back
of mouth
◦ a. uvula raises up to cover opening to nose
◦ b. epiglottis drops down to cover top of
trachea

3. esophagus – bolus passes through
tube leading from mouth to stomach
◦ a. peristalsis – muscle action that pushes food
through digestive tract

4. stomach – functions
◦
◦
◦
◦
a. food is stored – can expand to store 2-4L
b. mixes food to produce a mixture called chyme
c. physical dig occurs
d. produces gastrin (sight, smell, food in stomach)
which stimulates cells to produce gastric juices

e. chem digestion occurs
◦ 1) HCl denatures/unfolds the proteins (& kills
bacteria)
◦ 2) secretes gastric juice – mix of enzymes & HCl
◦ 3) proteins broken down by pepsin
 a) pepsinogen (inactive form of pepsin)
produced by stomach cells
 b) pepsinogen activated by HCl
 c) stomach protected from HCl by mucus lining
 d) when mucus lining is “eaten” through –
peptic ulcers occur
◦ -caused by bacteria ---treated w/ antibiotics

5. small intestine – bulk of digestion
occurs here – 3 sections (duodenum,
jejunum, & ileum
◦ a. continues digestion of starch & protein
◦ b. starts digestion of fats & nucleic acids
◦ c. enzymes
 1) wall of SI secretes
◦ a) secretes secretin – stimulates the pancreas
to produce bicarbonate
◦ b) proteases – digest proteins (ex:
aminopeptidase)
◦ c) phosphatases – digests nucleic acids
◦ d) maltase & lactase – digests disaccharides
◦ e) cholecystokinin – stims gallbladder to
release bile & pancreas to release enzymes

2) pancreas – secretes enzymes in an
alkaline solution to neutralize HCl
◦
◦
◦
◦
a) trypsin – protease (break down proteins)
b) chymotrypsin – protease
c) lipase – fat break down
d) pancreatic amylase – starch breakdown

3) liver
◦ a) produces bile (alkaline – not an enzyme -stored in gall bladder)
◦ b) bile emulsifies fat – breaks it up into smaller
globules so enzymes have a greater surface area
to work on

4) villi & microvilli – finger-like projections
“fringe”
◦ a) increase surface area for absorption of
digested materials

4. Large Intestine – reabsorbs water
from what’s left over of the “food” to
form feces or solid wastes
◦ a. feces stored in end of LI, rectum, & pushed
out of the body (Valsalva muscle movement)
through the anus
V. Evolutionary adaptations
A. Dentition: an animal’s assortment of
teeth
 B. Digestive system length
 C. Symbiosis
 D. Ruminants
