Digestion and absorption

Question 1

what is digestion?

Answer 1

process which large molecules are hydrolysed by enzymes into smaller molecules which can be absorbed and assimilated

Question 2

what is ingestion?

Answer 2

process by taking food into body through the mouth (eat)

Question 3

what is assimilation?

Answer 3

the conversion of absorbed food into a substance required for the body

Question 4

what is egestion?

Answer 4

final act of digestion which eliminates solid/liquid waste material from digestive tract via the anus

Question 5

what is another term for egestion?

Answer 5

defecation

Question 6

name the seven major parts of the digestive system

Answer 6

• salivary glands
• oesophagus
• stomach
• pancreas
• large intestine
• small intestine
• rectum

Question 7

mnemonic for major parts of digestive system

Answer 7

• So
• Ollie
• Stopped (eating)
• Pringles
• Like
• Some
• Rookie

Question 8

location/ function of salivary glands

Answer 8

• situated near mouth

- pass secretions via a duct in mouth which contains amylase

Question 9

function of oesophagus

Answer 9

carries food from mouth to stomach

Question 10

description/ function of stomach

Answer 10

• muscular sac with inner layer producing protease

- stores and digest food

Question 11

location/ function of pancreas

Answer 11

• situated below stomach

- produces secretion called pancreatic juice containing protease, lipase and amylase

Question 12

function of large intestine (colon)

Answer 12

• absorbs water from secretions of digestive glands

Question 13

function of small intestine (ileum)

Answer 13

• digests food by enzymes

- inner walls folded into villi to aid absorption of products into bloodstream

Question 14

functions of rectum

Answer 14

• temporary storage for faeces

- removed via anus in egestion

Question 15

what is the overall name for enzymes used in digestion and what process do they use to split molecules?

Answer 15

• hydrolases

- hydrolysis: split molecules by adding water

Question 16

what are the two stages to digestion?

Answer 16

• physical breakdown - churning

- chemical breakdown - digestion

Question 17

what are three types of molecules digested?

Answer 17

• carbohydrates
• lipids
• proteins

Question 18

which enzymes are involved in the digestion of carbohydrate?

Answer 18

• salivary amylase
• pancreatic amylase
• maltase (membrane-bound disaccharidase)

Question 19

what pH does amylase work best in and how does the body maintain the optimum pH?

Answer 19

• alkaline conditions
• salivary amylase: contains mineral salts to keep pH at neutral
• pancreatic amylase: alkaline salts produced by pancreas and intestinal wall to maintain pH

Question 20

explain the process of carbohydrate digestion

Answer 20

saliva enters mouth through glands

• mixes with food during chewing
• saliva contains salivary amylase which hydrolyses starch to maltose
• swallowed by stomach
• stomach acid denatures salivary amylase
• passed into small intestine
• mixes with pancreatic juice containing amylase which hydrolyses starch to maltose
• muscles in intestinal wall pushes food along ileum
• epithelial lining produced maltase (membrane-bound disaccharidase)
• hydrolyses maltose into alpha-glucose

Question 21

name two others disaccharides that are digested in diet

Answer 21

• sucrose

- lactose

Question 22

how is sucrose hydrolysed?

Answer 22

sucrase

- glucose + fructose

Question 23

how is lactose hydrolysed?

Answer 23

• lactase

- glucose +galactose

Question 24

what type of enzymes hydrolyse lipids?

Answer 24

• lipase

Question 25

where is lipase produced and what does it do?

Answer 25

produces in pancreas | - hydrolyses ester bond in triglycerides - fatty acid + monoglyceride

Question 26

how does lipase split the lipid up?

Answer 26

- split into micelles - emulsified by bile salts - surface area increased - increased enzyme reaction rate

Question 27

how are micelles (triglycerides) absorbed?

Answer 27

- micelles come into contact with epithelial cells - release monoglycerides and fatty acids - as they are non-polar, they diffuse across cell membrane - recombine on SER to form triglyceride - in Golgi triglycerides combines with cholesterol and lipoproteins to form chylomicrons - secreted out of cell by exocytosis - enter lacteals (lymphatic capillaries) - emptied into blood stream via thoracic duct - either used by blood or transported to liver and split into HDL and LDL -

Question 28

what enzymes are involved in protein digestion?

Answer 28

peptidases (proteases)

Question 29

what three peptidases are used?

Answer 29

- endopeptidase - exopeptidase - dipeptidase

Question 30

explain process of protein digestion

Answer 30

- endopeptidase hydrolyses peptide bonds between amino acids in central region to split into peptides - exopeptidase hydrolyses peptide bonds between terminal amino acids to release dipeptides and single amino acids - dipeptidase hydrolyses dipeptides into two monopeptide

Question 31

what is dipeptidase described as?

Answer 31

membrane bound