digestion + absorption

Question 1

what does the salivary glands produce

Answer 1

amylase

Question 2

what is the ilium

Answer 2

small intestine

Question 3

where is amylase produced

Answer 3

salivary glands or pancreas

Question 4

where does the pancreas secrete amylase

Answer 4

small intestine

Question 5

what is the role of amylase

Answer 5

hydrolyses starch (carb) / polysaccharide into maltose which is a disaccharide

Question 6

where are membrane-bound disaccharides found

Answer 6

they are present in the membrane of the small intestine

Question 7

what is the role of membrane-bound disaccharidases

Answer 7

to hydrolyse disaccharides eg maltose into monosaccharides eg glucose

Question 8

examples of membrane-bound

Answer 8

maltase, sucrase, lipase

Question 9

role of lipase

Answer 9

hydrolyse lipids to monoglycerides and fatty acids

Question 10

where is lipase present

Answer 10

in the small intestine

Question 11

adaptations of lipase

Answer 11

bile salts - made by liver - emulsify lipids, giving them a large SA, so they’re easily hydrolysed by lipases

produces can remain associated with bile salts to form micelles

Question 12

micelles travel

Answer 12

to ileum and are broken down when in contact with epithelium, products can then diffuse straight into epithelium

Question 13

proteases role

Answer 13

hydrolyse proteins (polypeptides) into amino acids

Question 14

three types of protease

Answer 14

endopeptidase, exopeptidase, and membrane-bound dipeptidases

Question 15

endopeptidases

Answer 15

eg trypsin, chymotrypsin and pepsin

hydrolyse peptide bonds in the middle region of the polypeptide chain

Question 16

exopeptidases

Answer 16

hydrolyse peptide bonds on terminal amino acids

Question 17

membrane-bound dipeptidases

Answer 17

hydrolyse dipeptides (2 amino acids condensed together) into 2 amino acids

Question 18

how are amino acids and monosaccharides absorbed into the blood

Answer 18

co-transport
there is a high concentration of glucose inside the epithelial cell than in the lumen
there is a lower concentration of Na+ inside the epithelial cell than in the lumen
the co-transport/carrier protein has two binding sites, one for glucose and one for Na+
when both glucose and Na+ bind to the carrier protein, the protein changes its tertiary structure to transport them into the cell

Question 19

what happens to food during digestion and why

Answer 19

the large biological molecules are too big to cross cell membranes - cannot be absorbed from the gut into blood

during digestion - large molecules broken down into smaller molecules which can be easily absorbed

polymers -> monomers by hydrolysis

Question 20

what are carbohydrates broken down into to

Answer 20

carbohydrates are broken down into disaccharides then monosaccharides

Question 21

what are fats broken down into

Answer 21

fatty acids and monoglycerides

Question 22

what are proteins broken down into

Answer 22

amino acids

Question 23

what does amylase do

Answer 23

convert starch (polysaccharide) into a smaller sugar maltose (disaccharide)

hydrolysis of glycosidic bonds in starch

Question 24

where is amylase produced

Answer 24

in the salivary glands and in the pancreas

Question 25

what do lipase do

Answer 25

lipase enzymes catalyse the breakdown of lipids into monoglycerides and fatty acids

hydrolysis of ester bonds

Question 26

where is lipase made

Answer 26

pancreas

Question 27

what are membrane-bound disaccharides

Answer 27

enzymes that are attached to the cell membranes of epithelial cells lining the ileum

help break down disaccharides (maltose, sucrose and lactose) into monosaccharides (glucose, fructose and galactose)

maltase, sucrase, lactase

Question 28

what do bile salts do and where are they made

Answer 28

produced by the liver, emulsify lipids - cause the lipids to form small droplets

Question 29

why are bile salts important

Answer 29

several small lipid droplets have a bigger surface area than a single large droplet, so increases the surface area that’s available for lipases to work on

once the lipid has been broken down - monoglycerides and fatty acids stick with the bile salts to form micelles

Question 30

what is endopeptidases

Answer 30

act the hydrolyse peptide bonds within a protein

trypsin and chymotrypsin are two examples
- synthesised in pancreas and secrete to small intestine

pepsin - released into the stomach by cells in the stomach lining - only works in acidic conditions

Question 31

what are exopeptidases

Answer 31

act to hydrolyse peptide bonds at the ends of the protein molecules - remove single amino acids from proteins

dipeptidases are example - work specifically on dipeptides to separate the amino acids that make up a dipeptide by hydrolysing the peptide bond between them
- located in the cell-surface membrane on epithelial cells

Question 32

how are monosaccharides absorbed

Answer 32

glucose is absorbed by active transport with sodium ions via a co-transporter protein

galactose is absorbed in the same way using the same co-transporter protein

fructose is absorbed via facilitated diffusion through a different transporter protein

Question 33

how are monoglycerides and fatty acids absorbed

Answer 33

micelles help to move monoglycerides and fatty acids towards the epithelium

micelles constantly break up and reform - they can ‘release’ monoglycerides and fatty acids allowing them to be absorbed

whole micelles cannot be taken up across the epithelium
monoglycerides and fatty acids are lipid-soluble so can diffuse directly across

Question 34

how are amino acids absorbed

Answer 34

via co-transport, in a similar way to glucose and galactose

sodium ions are actively transported out of the ileum epithelial cells into the blood

creates a sodium ion concentration gradient

sodium ions can then diffuse from the lumen of the ileum into the epithelial cells through sodium-dependent transporter proteins, carrying the amino acids with them