Digestion

Question 1

Definition of digestion

Answer 1

Large insoluble biological molecules in food are hydrolysed into smaller, soluble molecules that can be absorbed across the cell membranes into the bloodstream and delivered to cells

Question 2

What do the small soluble molecules used for

Answer 2

provide cells with energy
build other molecules for cell growth, repair and function

Question 3

Process of digestion structures

Answer 3

1) Mouth
2) Salivary Glands
3) Oesophagus
4) Stomach
5) Small intestine
6) Large intestine
7) Rectum
8) Anus

Question 4

Two types of digestion

Answer 4

Physical breakdown
Chemical digestion

Question 5

Physical breakdown

Answer 5

Food churned by muscles in stomach wall and teeth in mouth
Provides surface for chemical digestion

Question 6

What is hydrolysis

Answer 6

Splitting up of molecules adding water to the chemical bonds that hold them together

Question 7

How do digestive enzymes function

Answer 7

Hydrolysis

Question 8

What enzymes digest carbohydrates, lipids, proteins

Answer 8

Carbohydrases
Lipases
Proteases

Question 9

Where is amylase produced

Answer 9

Mouth and pancrease

Question 10

What enzyme hydrolyses starch

Answer 10

amylase

Question 11

Process of the breakdown of starch

Answer 11

1) Amylase produced in mouth that pancreas
2) Amylase hydrolyses glycosidic bonds, producing maltose
3) Maltose is hydrolysed into a-glucose using maltase

Question 12

Where is maltase produced

Answer 12

Ileum

Question 13

Process of carbohydrate digestion

Answer 13

1) Saliva enters mouth from salivary gland mixed during chewing
2) Salivary amylase hydrolyses starch into maltose, containing mineral salts to maintain pH at neutral
3) Food swallowed and enters stomach. Acid denatures amylase preventing further hydrolyses of starch
4) Food enters small intestine and mixes with pancreatic juice
5) Containing pancreatic amylase that hydrolyses starch into maltose. Alkaline salts maintain pH so amylase can function
6) Muscles in intestine wall push food along ileum to produce maltase
7) Maltase hydrolysed to alpha glucose

Question 14

Where are alkaline salts produced

Answer 14

Intestinal wall and pancreas

Question 15

What hydrolyses sucrose

Answer 15

Sucrase
Hydrolyses glycosidic bond to produce glucose and fructose

Question 16

What hydrolyses lactose

Answer 16

Lactase
produce glucose and galactose

Question 17

Where are lipases produced

Answer 17

Pancreas

Question 18

What do lipases do

Answer 18

Hydrolyse ester bonds in triglycerides to form fatty acids and monoglycerides

Question 19

How are lipids digested

Answer 19

Emusification process where Lipids split into micelles by bile salts
Increasing SA of lipid for lipases to act on

Question 20

Where are bile salts produced

Answer 20

Liver

Question 21

What enzymes digest protein

Answer 21

Peptidases (proteases)

Question 22

3 types of peptidases

Answer 22

Endopeptidases
Exopeptidases
Dipeptidases

Question 23

Endopeptidases

Answer 23

Hydrolyse peptide bonds between amino acids and central region of a protein molecule forming series of peptide molecules

Question 24

Exopeptidases

Answer 24

After endopeptidases act, exo hydrolyse peptide bonds on terminal amino acids of peptide molecule
Releasing dipeptides and single amino acids

Question 25

Dipeptidases

Answer 25

After endo and exo Hydrolyse bond between two amino acids of a dipeptide Part of cell-surface membrane of epithelial cells lining in ileum

Question 26

What does the ileum have

Answer 26

Villi

Question 27

What do villi give an advantage to

Answer 27

Increased surface area, increasing rate of absorption

Question 28

What advantages do the villi give in digestion

Answer 28

- Increase SA for diffusion - Thin = reduced distance for diffusion - Contains muscle = maintain diffusion gradient because movement mixes contents of ileum, once absorbed new products replace old ones - Rich blood supply = carry away absorbed molecules, maintaining diffusion gradient - Villi have microvilli = increase SA further

Question 29

What are micelles

Answer 29

Monoglycerides and fatty acids (from a lipid droplet) with bile salts

Question 30

What happens to micelles

Answer 30

Monoglycerides and fatty acids are released (micelles just transport them to the small intestine)

Question 31

How can micelles be transported to the ileum

Answer 31

Micelles are non-polar and so can diffuse across cell surface membrane into epithelial cells

Question 32

What happens once the micelles break down into monoglycerides and fatty acids

Answer 32

Monoglycerides and fatty acids diffuse into epithelial cell and are transported to the endoplasmic reticulum They recombine to form triglycerides

Question 33

What do the newly formed triglycerides do

Answer 33

Form chylomicron when the triglycerides associate with cholesterol and lipoproteins

Question 34

What do chlymicrons do

Answer 34

Transport the lipids

Question 35

What do chylomicrons do

Answer 35

Move out of the epithelial cells by exocytosis Enter lacteals (lymphatic capillaries) found in the centre of the villus Chylomicrons pass via lymphatic vessels into the blood stream

Question 36

What happens to the triglycerides in the chylomicrons in the blood stream

Answer 36

Triglycerides are hydrolysed by enzymes in the endothelial cells of blood capillaries Where they can diffuse into cells

Question 37

Process of how triglycerides are absorbed

Answer 37

1) Micelles from a lipid droplet break down into monoglycerides and fatty acids 2) They transported to the endoplasmic reticulum and combined to form triglycerides 3) Triglycerides associate with cholesterol and lipoproteins to form chylomicrons 4) Chylomicrons move out of epithelial cells by exocytosis and enter lacteals 5) the chylomicrons pass through the blood system and are hydrolysed by enzymes in the endothelial cells where they diffuse into cells

Question 39

What is digestion

Answer 39

Large insoluble biological molecules in food are hydrolysed into smaller, soluble molecules that can be absorbed across the cell membranes into blood stream and delivered to cells

Question 40

What are the three main types of enzymes

Answer 40

Carbohydrases proteases and lipases

Question 41

How are carbohydrates digested (process) by amylase

Answer 41

1) Amylase hydrolyses starch into maltose in mouth and small intestine 2) Maltase hydrolyses maltose into glucose 3) Amylase in salivary glands, pancrease and small intestine 4) Maltase found in CSM of epithelial cells linign small intestine 5) Sucrase and lactase hydrolyse sucrose and lactose allowing absorption of monosaccharides into epithelial cells of small intestine which is passed into the blood stream

Question 42

Digestion of proteins by proteases

Answer 42

1) Protein digestion begins in stomach 2) Endopeptidase hydrolyses peptide bonds in proteins and HCl acid released so pH in stomach is low and acidic. 3) Fluid secreted by pancreas travels to small intestine and neutralises acid to increase pH. 4) Pancreatic juice contains endopeptidases (hydrolyse bonds in middle of polypeptide chains) producing dipeptides And exopeptidases hydrolyse at ends of polypeptide chains to produce dipeptides There are also dipeptidase enzymes in CSM that hydrolyse dipeptides into amino acids and released into cytoplasm of cell

Question 43

Summary of how proteins are digested

Answer 43

Protein + endopeptidase = polypeptides Polypeptides + exopeptidase = dipeptides Dipeptides + dipeptidase = amino acids

Question 44

Emulsification of lipids

Answer 44

1) Stomach turns fatty liquid into fat droplets 2) Fatty liquid arrives in small intestine, bile is secreted from gallblader 3) Bile salts + fatty liquid breaks fatty droplets into smaller ones by emulsification (Increases SA of fatty droplets for digestive enzymes)

Question 45

Digestion of lipids

Answer 45

Lumen of small intestine Lipase breaks fown lipids to glycerol and fatty acids Lipase produced in pancreas and secreted into small intestine by pancrease

Question 46

Summary of both lipid digestion

Answer 46

Lipids + bile salts -> emulsified lipids + lipase -> fatty acids and glycerol Large fat globule + emulsification -> small fat droplets + dugestion -> fatty acids and glycerol

Question 47

Factors affecting enzyme reaction rates practical

Answer 47

1) Add iodine to spotting tile 2) Add amylase and buffer to test tube, mux then add starch solution 3) start stopwatch 4) After 10 secs add a drop of solution to iodine in spotting tile 5) Repeat every 10 seconds until iodine doesnt change colour 6) Repeat steps 1-5 using buffer solutions of differen pH

Question 48

Absorption of amino acids

Answer 48

Facilitated diffusion: -Amino acid co-transport proteins in cell surface membrane of epithelial cells in ileum -1 Na+ enters cell, 1 amino acid transport out -Diffuse across epithelial cells and into capillaries -Conc gradient of Na maintained by active transport of Na+ out of cell and into blood via sodium potassium pumps

Question 49

Absorption of monosaccharides

Answer 49

1) Glucose carrier proteins co transport sodium ions and glucose by facilitated diffusion into epithelial cells 2) Glucose diffuse across apithelial cells and enter capillary 3) Conc of Na+ maintained by actively transporting sodium ions out of epithelial cells in blood

Question 50

What do micelles do to absorb lipids

Answer 50

Micelles are fatty acids and monoglycerides + phospholipids and bile salts Micelles break down and are added to fatty acids and monoglycerides to dissolve small intestine solution surrounding epithelial cells

Question 51

What do the short and long lipid chains do to be asborbed

Answer 51

Short = move directly into blood by diffusion Long = recombine with monoglycerides and glycerol forming triglycerides in endoplasmic reticulum

Question 52

How are triglycerides absorbed

Answer 52

Packed into chylomicrons Chylomicrons enter bloodstream via lacteals