Module 5 PART B

Question 1

extracellular digestion

Answer 1

digestive enzymes secreted into cavity by gland cells

Question 2

why does extracellular digestion take a long time?

Answer 2

bc digestive enzymes are diluted in fluid

Question 3

intracellular digestion

Answer 3

endocytosis - cells lining gastrovascular cavity move partially digested food into cell

Membrane food vacuole fuses w/ lysosome to form digestive vacuole & waste is released by exocytosis

Question 4

crop (in more complex organisms than hydra or jellyfish which only have 1 gut cavity)

Answer 4

storage chamber where food is stored & digested slowly over time. Enlarged portion of the digestive system (in invertebrates & birds) – e.g. in a worm

Question 5

gizzard

Answer 5

a muscular part of the gut that has grits or stone in it that helps grind the food mechanically. Gizzards are found in birds, earthworms, some fish, & some reptiles

Question 6

how do lipids enter the cellular respiration pathway?

Answer 6

by first being broken down into glycerol & fatty acids and then entering through beta oxidation

Question 7

animals cant synthesize the acetyl group so where does it come from & what is it used to synthesize?

Answer 7

comes form food
Acetyl group used to synthesize steroid hormones + amino acids, heme, & other compounds; fatty acids, citrate, etc.

Question 8

amount of food needed depends on

Answer 8

• metabolic rate (varies w age, reproductive stage, activity)
• body mass & environmental conditions
• types of food

Question 9

per unit body mass SMALL animals need more/less than larger ones?

Answer 9

MORE as small animals have larger SA:V ratio

Question 10

carnivorous teeth

Answer 10

greatly enlarged canine teeth for gripping, killing, & tearing their prey - also have incisors

Question 11

herbivorous teeth

Answer 11

have incisors - mainly have premolars & molars

Question 12

omnivorous teeth

Answer 12

multipurpose set of teeth

Question 13

pyloric sphincter (constriction in tube in stomach)

Answer 13

determines how much chyme is allowed into the next section of the digestive system

Question 14

enzymatic digestion occurs where?

Answer 14

in duodenum

In the duodenum, large lipid droplets are emulsified into smaller micelles and this increases the SA for the lipases to work in an aqueous environment to break down the lipids into monoglycerides and fatty acids

Question 15

nutrient absorption occurs where?

Answer 15

in jejunum

Question 16

gallstones

Answer 16

solidification of bile salts + cholesterol

Question 17

pancreas secretes. . . ?

Answer 17

bicarbonate ions to neutralize acidity of chyme

Question 18

hepatopancreatic duct

Answer 18

the common duct that secretes fluids from both the liver and pancreas into the duodenum

Question 19

what do epithelial cells secrete?

Answer 19

peptidases & enzymes for breaking down oligosaccharides

Question 20

large intestine (colon)

Answer 20

Just at start of large intestine - caecum: blind ended sac; cellulose digestion (prominent in herbivores)

In large intestine - water absorption & formation of feces

Question 21

carnivorous digestive tract

Answer 21

short, simple digestive tracts; short intestine & small caecum

Question 22

herbivorous tracts

Answer 22

long, complex digestive tracts with a large caecum

Question 23

how do herbivores digest cellulose?

Answer 23

Since most herbivores don’t have the enzyme cellulase, they have symbiotic bacteria & protists (microbes) that live in their digestive tracts & digest cellulose

These symbiotic bacteria have cellulases which hydrolyze the cellulose to produce glucose

This glucose is then used as an energy source by microbes

The microbes produce short chain fatty acids which the host then absorbs & uses as a source of energy

The short chain fatty acids promote good gut health by maintaining the integrity of the intestinal barrier

Question 24

Foregut fermenters vs hindgut fermenters

Answer 24

–> digestion of cellulose by microbes occurs BEFORE the stomach

–> Digestion of cellulose occurs AFTER stomach (e.g. horse, koala, combat, pig, rabbit)

Question 25

e.g. of foregut fermenters

Answer 25

kangaroos

Question 26

e.g. of hindgut fermenters

Answer 26

horse, koala, pig, rabbit

Question 27

Foregut fermenters & how does it work

Answer 27

The microbes are present in the large forestomach - they produce short chain fatty acids which are then used as an energy source

The microbes wash through to the hind stomach & small intestine & provide the host with a source of protein - the microbes THEMSELVES are a rich source of protein

Question 28

hindstomach

Answer 28

• acidic & contains pepsin
• Ruminants - special case of foregut fermenters
• Regurgitate their food to reduce size of food particles

Ruminants have LARGE foreguts w/ four chambers:
Rumen
Reticulum
Omasum
True stomach

Question 29

Hindgut fermenters

Answer 29

Bacteria (only) present in the caecum & proximal colon

Microbes that wash through digestive tract cannot be used as protein source

This is because the microbes are living in the part of the gut that is after where the nutrients / proteins are absorbed in the small intestine

Caecum & proximal colon together are referred to as the HINDGUT

Question 30

caecotrophy

Answer 30

specialization of eating your own feces (ringtail possums)
- it is a rich source of protein w microbes
- formal fecal pellets (at night)

Question 31

Movement of water through roots

Answer 31

Water moves through the root via the apoplast and symplast until it reaches the Casparian
strip and is then forced to flow via the symplast to the central vasculature.