digestion and absorption (3.3)

Question 1

what is digestion

Answer 1

large insoluble molecules are hydrolysed into smaller molecules that can be absorbed across cell membranes

Question 2

what enzymes are used in carbohydrate digestion and where are they found

Answer 2

-amylase in the mouth/salivary glands
-maltase,sucrase,lactase in the small intestine

Question 3

what are the substrates and products of carbohydrate digestive enzymes

Answer 3

-amylase hydrolyses starch into smaller polysaccharides
-maltase hydrolyses maltose into 2 glucose molecules
-sucrase hydrolyses sucrose into glucose and fructose
-lactase hydrolyses lactose into galactose and glucose

Question 4

what are the 3 enzymes proteins can be hydrolysed by

Answer 4

-endopeptidases
-exopeptidases
-dipeptidases

Question 5

what do endopeptidases do

Answer 5

hydrolyse peptide bonds between amino acids in the middle of the polymer chain

Question 6

what do exopeptidases do

Answer 6

hydrolyse peptide bonds between amino acids at the end of the polymer chain

Question 7

what do dipeptidases do

Answer 7

hydrolyse peptide bonds between 2 amino acids

Question 8

where does protein digestion occur

Answer 8

stomach continues in duodenum finishes in ileum

Question 9

how are lipids digested

Answer 9

lipids are digested by lipase and the action of bile salts

Question 10

where is lipase produced and what does it do

Answer 10

-produced in pancreas
-hydrolyses ester bond in triglycerides to form monoglycerides and fatty acids

Question 11

where are bile salts produced and what do they do

Answer 11

-produced in liver
-emulsify lipids into many tiny droplets which creates a larger sa for lipase to work on , enabling faster hydrolysis of lipids
-also form micelles

Question 12

what are micelles

Answer 12

water soluble vesicles formed of fatty acids, monoglycerides and bile salts

Question 13

what is the purpose of micelles

Answer 13

-they deliver the fatty acids and monoglycerides to the epithelial cells of the ileum
-micelles make fatty acids more soluble in water so they break down when they reach the ileum

Question 14

where does absorption occur

Answer 14

occurs in cells lining the ileum

Question 15

how is the ileum wall adapted for absorption

Answer 15

-covered in villi which have microvilli
-villi surrounded by capillaries
-thin wall

Question 16

how are monosaccharides and amino acids absorbed

Answer 16

co transport

Question 17

describe co transport process

Answer 17

-active transport of sodium ions from epithelial cell into blood to lower sodium ion concentration inside of cell to generate a sodium ion concentration gradient between the ileum and epithelial cell
-sodium ions move into the cell from the ileum by faciliated diffusion carrying an amino acid or glucose molecule along with them via a co transporter protein
-glucose/amino acid concentration in the epithelial cell will then increase and glucose will enter the blood by faciliated diffusion.

Question 18

describe the first step of lipid absorption

Answer 18

-when micelles encounter the ileum epithelial cells they break down and due to the non polar nature of fatty acids and monoglycerides they simply diffuse across the cell surface membrane to enter the epithelial cells

Question 19

what happens once the fatty acids and monoglycerides are in the cell

Answer 19

the fatty acid chains and monoglycerides recombine to create triglycerides in the endoplasmic reticulum

Question 20

what is the golgi apparatus role in lipid absorption

Answer 20

-the triglycerides are modified by adding a protein to create chylomicrons
-the chylomicrons are then packaged into golgi vesicles
-these vesicles move to the cell membrane and fuse so they are extruded from cell by exocytosis

Question 21

howdo chylomicrons enter the bloodstream

Answer 21

enter a lacteal which will eventually lead to the chylomicrons entering the bloodstream