Digestion

Question 1

digestion

Answer 1

the mechanical and chemical break down of food so it can be absorbed into the blood

Question 2

mechanical digestion

Answer 2

breaking down large food by grinding and churning to increase SA available for chemical digestion

Question 3

chemical digestion

Answer 3

enzymes hydrolyse covalent bonds to break down large molecules into smaller soluble molecules that can be absorbed into te blood

Question 4

two types of chemical digestion

Answer 4

intracellular and extracellular

Question 5

intracellular digestion

Answer 5

occurs in epithelial cells of ileum

Question 6

extracellular digestion

Answer 6

enzymes are secreted out of cells ito the gut lumen

Question 7

4 examples of extracellular digestion organs and glands

Answer 7

• salivary glands –> mouth
• gastric glands –> stomach
• pancreas –> duodenum
• liver –> duodenum (bile)

Question 8

2 enzymes involved in intracellular digestion

Answer 8

disaccharidases and dipeptidases

Question 9

what is the benefit of requiring multiple enzymes to fully digest a food type

Answer 9

the action of the fist enzyme icreases the SA available for the second enzyme so increases rate of digestions

Question 10

why do different regions ofthe gut have different pHs?

Answer 10

enzymes have different optimum pHs

Question 11

3 roles of mucus

Answer 11

• important in maintaining correct pH of particular regions of the gut –> neutralise stomach acid in duodenum
• provides lubrication for food to move along gut
• protects gut lining from erosion (acid atack)

Question 12

what, how, where

2 steps of carbohydrate digestion

Answer 12

1. starch is broken down into maltose by salivary and pancreatic amylase in the stomach and duodenum
2. maltose is broken down into glucose by maltase in the epithelial cells of the ileum

Question 13

2 disaccharidases

Answer 13

sucrase and lactase

Question 14

what, how, where

3 steps of protein digestion

Answer 14

1. proteins are broken down into polypeptide chains by endopeptidases (pepsin) in the stomach
2. polypeptide chains broken down into shorter polypeptide chains by endopeptidases (trypsin) in the duodenum
3. shorter polypeptide chains are proken down into dipeptides and amino acids by exopeptidases in the duodenum
4. dipeptides are broken down into amino acids by dipeptidases (exopeptidases) inthe epithelial cells lineing the ileum

Question 15

peptidases

Answer 15

hydrolyse peptide bonds in a polypeptide chain

Question 16

endopeptidases

Answer 16

hydrolyse inner peptide bonds in a polypeptide chain

Question 17

exopeptidases

Answer 17

hydrolyse end (terminal) peptide bonds in a polypeptide

Question 18

3 types of exopeptidases

Answer 18

1. aminopeptidases = N-terminal (left end)
2. carboxypeptidases = C-terminal (right end)
3. dipeptidases = dipeptides

Question 19

2 steps of lipid digestion

Answer 19

1. mechanical brekadown of lipid droplets into micelles by bile salts in the duodenum
2. chemical digestion of micelles into monoglycerides and fatty acids by lipase in the duodenum

Question 20

what is the role of bile salts in digestion of lipids?

Answer 20

emulsify lipid droplets to increase SA available for action of lipase

Question 21

function of sodium hydrogencarbonate in lipid digestion

Answer 21

neutralise stomach acid in duodenum

Question 22

contents of bile

Answer 22

bile salts and sodium hydrogencarbonate

Question 23

where is bile produced, stored and released?

Answer 23

produced in liver
stored in gall bladder
released via bile duct into the duodenum

Question 24

advantage of micelles forming

Answer 24

micelles are water soluble so are more easily transported to the epithelial cells in the ileum

Question 25

pH of mouth

Answer 25

pH 6.5-7.5

Question 26

mechanical digestion in the mouth

Answer 26

teeth break up food to increase SA for chemical digestion

Question 27

chemical digestion in mouth

Answer 27

* salivary glands secrete saliva containing amylase, mucus and mineral ions * starch digested

Question 28

function of mucus and mineral ions in mouth

Answer 28

mucus = lubrication mineral ions = maintain neutral pH

Question 29

oesophagus in digestion

Answer 29

lined by epthelial tissue, containing goblet cells which secrete mucus for lubrication peristalsis occurs = coordinated contraction of circular and longitudinal muscle

Question 30

mechanical digestion in stomach

Answer 30

churn contents to form acidic chyme (has extra layer of muscle - oblique - to aid churning

Question 31

chemical digestion in stomach

Answer 31

gastric gland secrete gastric juice containing hydrochloric acid, endopeptidases (pepsin) and mucus digest proteins

Question 32

pH of stomach

Answer 32

2

Question 33

function of hydrochloric acid in stomach

Answer 33

decrease pH to activate enzyes and kill bacteria by denaturing their enzymes

Question 34

function of mucus in stomach

Answer 34

lubrication and protection from erosion

Question 35

two sphincters of the stomach

Answer 35

cardiac sphincter and pyloric sphincter

Question 36

pH of the duodenum

Answer 36

7-8

Question 37

where is the main sitee of chemical digestion?

Answer 37

duodenum

Question 38

what 3 glands secrete juices into the duodenum and what do they secrete??

Answer 38

* pancreas - pancreatic juice * liver - bile * Broner's gland - mucus

Question 39

what does pancreatic juice contain?

Answer 39

* endopeptidase and exopeptidases * lipase * amylase * hydrogen carbonate ions

Question 40

function of mucus in duodenum

Answer 40

neutralise stomach acid and protect wall from acid erosion

Question 41

2 steps of digestion in ileum

Answer 41

1. as molecules move across epithelial cell membrane, theyre hydrolysed by proteins in the cell into their monomers 2. taken away in blood so maintains concentration gradient from ileum lumen to epithelial cell

Question 42

what two molecules are digested in the ileum?

Answer 42

disaccharides and dipeptides?

Question 43

function of the colon

Answer 43

absorbs remaining waater and vitamins from bacteria absorbs water so we can produce solid faeces as this stimulates peristalsis

Question 44

contents of faeces

Answer 44

undigested material (cellulose) - fibre souughed cells bacteria

Question 45

function of the rectum

Answer 45

temporary store of faeces before egestion

Question 46

egestion

Answer 46

removal of undigested and waste material from the body

Question 47

what are sloughed cells

Answer 47

cells scraped off the gut wall

Question 48

site of action of amylase

Answer 48

mouth and duodenum

Question 49

site of action of endopeptidases

Answer 49

stomach and duodenum

Question 50

site of action of exopeptidases

Answer 50

duodenum and ileum

Question 51

site of action of lipase

Answer 51

duodenum

Question 52

site of action of disaccharidases

Answer 52

ileum