digestion and absorption

Question 1

what is starch digested by

Answer 1

amylase

membrane-bound disaccharides

Question 2

describe how starch is digested by amylase and membrane-bound disaccharides

Answer 2

• amylose hydrolyses starch to maltose
• membrane-bound maltase hydrolyses maltose to glucose
• glycosidic bond is hydrolysed

Question 3

where is amylase produced and what is it released into

Answer 3

• salivary glands, into mouth

- pancreas, into small intestine

Question 4

starch to maltose

maltose to glucose

Answer 4

polysaccharide to disaccharide

disaccharide to monosaccharide

Question 5

describe how disaccharides are digested

Answer 5

membrane-bound disaccharides hydrolyse disaccharide into 2 monosaccharides
hydrolysis of glycosidic bond

Question 6

what is galactose hydrolysed to

Answer 6

glucose

lactose

Question 7

what is sucrose hydrolysed to

Answer 7

glucose

fructose

Question 8

what is maltose hydrolysed to

Answer 8

glucose

glucose

Question 9

describe how lipids are digested

Answer 9

• bile salts produced in liver
• bile salts emulsify lipid to smaller lipid droplets
• lipase, made in pancreas, released to small intestine
• lipase hydrolysis lipids into monoglycerides + fatty acids
• breaking ester bond
• monoglycerides + fatty acids + biles salts stick together to form micelles

Question 10

why do bile salts emulsify lipids into smaller lipid droplets

Answer 10

to increase surface area of lipids

to speed up action of lipases

Question 11

where is lipase made and where is it released to

Answer 11

pancreas, into small intestine

Question 12

what 3 enzymes digest proteins

Answer 12

endopeptidases
exopeptidases
dipeptidases

Question 13

how do endopeptidases digest proteins

Answer 13

hydrolyse peptide bonds within protein

breaking protein into 2 or more smaller peptides

Question 14

how do exopeptidases digest proteins

Answer 14

hydrolyse peptide bonds at end of protein

removing a single amino acid

Question 15

how do dipeptidases digest proteins

Answer 15

often membrane-bound in ileum

hydrolyses peptide bond between dipeptide= 2 amino acids

Question 16

Describe the mechanism for absorption of monosaccharides and amino acids by the cells lining the ileum.

Answer 16

• Sodium ions actively transported out of epithelial cells lining the ileum, into the blood, by the sodium-potassium pump. Creating a concentration gradient of sodium (higher conc. of sodium in lumen than epithelial cell)
• Sodium ions and glucose move by facilitated diffusion into the epithelial cell from the lumen, via a co-transporter protein
• Creating a concentration gradient of glucose – higher conc. of glucose in epithelial cell than blood
• Glucose moves out

Question 17

Describe the mechanism for absorption of lipids by the cells lining the ileum.

Answer 17

-Monoglycerides and fatty acids diffuse out of micelles (in lumen) into epithelial cell
Because lipid soluble

• Monoglycerides and triglycerides recombine to triglycerides which aggregate into globules
• Globules coated with proteins to form chylomicrons
• Leave via exocytosis and enter lymphatic vessels
• Return to blood circulation