Enzymes And Digestion

Question 1

Enzyme action

Answer 1

Tertiary structure of enzyme
Shape of active site changes as substrate enters
Active site complementary to substrate
Enzyme lowers activation energy for reaction
By forming enzyme-substrate complex

Question 2

Competitive inhibitor

Answer 2

Inhibitor similar shape to substrate
Binds in to active site
As complementary to active site
Prevents substrate binding to active site
Prevents formation of ES complex
Inhibition can be overcome by more substrate;

Question 3

Non-competitive inhibition

Answer 3

nhibitor binds to site on enzyme other than active site (allosteric site) Changes the shape of the active site
Prevents substrate binding to active site
Prevents formation of ES complex
Cannot be overcome by adding more substrate;

Question 4

Denaturing

Answer 4

Caused by pH or high temperature
Hydrogen bonds broken
Changes tertiary structure of protein
Changes shape of active site
Prevents substrate binding to active site
Prevents formation of ES complexes

Question 5

Digestion of starch

Answer 5

Amylase
Hydrolyses alternate glyosidic bonds
Starch to maltose
In mouth and small intestine
Maltase
Membrane bound disaccharidase on small intestine
Hydrolyses maltose to glucose

Question 6

Digestion of protein

Answer 6

Endopeptidase
In stomach
Hydrolyses internal peptide bonds
Proteins to peptides

Exopeptidases
Hydrolyse terminal peptide bonds
Peptides to dipeptides

Dipeptidases
Membrane bound on small intestine
Dipeptides to amino acids

Question 7

Digestion of lipid

Answer 7

Bile salts
From liver/gall bladder
Emulsifies lipid into micelles
Increase surface area for lipase to work on
Lipase
From pancreas
Hydrolyses ester bonds
Lipid to fatty acids and monoglycerides

Question 8

Absorption of glucose or amino acids

Answer 8

Glucose or amino acid moves into epithelium cell with sodium ion
Using a carrier protein
Sodium ions moves down concentration gradient
Sodium ions actively transported out of epithelium cell into blood
Potassium ions move in opposite direction
Maintaining low concentration of sodium ions in epithelial cell
Glucose/amino acids diffuse into blood using a protein

Question 9

Absorption of triglycerides

Answer 9

Fatty acids and monoglycerides diffuse across phospholipid membrane
Transported to ER
Triglycerides reformed
Transferred to Golgi apparatus
Combined with cholesterol and lipoprotein
To form chylomicrons
Move out of epithelial cells
By exocytosis
Into lacteals in centre of villus