12.2 Flashcards
Does it take more than 1 enzyme to completely hydrolyse a large molecule? (1)
Yes
Describe the detailed process of starch digestion. (8)
(1) amylase is produced from the salivary glands and is released into the mouth with saliva
(2) This enzyme starts to hydrolyse starch into maltose (optimum pH = neutral) by breaking the alternate glycosidic bonds
(3) as the food enters the stomach, the acid denatures the amylase & prevents further hydrolysis of starch
(4) the food is passed into the small intestine, where it mixes with the secretions from the pancreas called the pancreatic juice
(5) This juice contains amylase, so it continues to hydrolyse the starch molecules
(6) muscles in the intestine wall push the food along the ileum
(7) Its epithelial lining produces maltase, which is a membrane-bound disaccharidase
(8) The maltase hydrolyses maltose into a-glucose molecules
Maltase is a membrane-bound disaccharidase. Define what that is. (2)
(1) enzymes attached to the cell-surface membranes
(2) of the epithelial cells lining the ileum
REMINDER: What is the process of testing for reducing sugars? (3)
Where is sucrose most likely found? (1)
Where is lactose most likely found? (1)
(1) sucrose = fruits
(2) lactose = milk products / cheese / yoghurt
Are sucrase and lactase also membrane-bound disaccharidases? (1)
Yes
Describe the function of sucrase (2)
(1) hydrolyses the single glycosidic bond in sucrose
(2) to produce glucose & fructose
Describe the function of lactase (2)
(1) hydrolyses the single glycosidic bond in lactose
(2) to produce glucose & galactose
Where are lipase enzymes produced? (1)
Pancreas
What is the function of lipases? (2)
(1) hydrolyses the ester bond in triglycerides
(2) to produce fatty acids & monoglycerides
What is a monoglyceride? (1)
a glycerol molecule with a single fatty acid attached
Before lipids are broken down by lipase, what is the first stage of the breakdown of lipids. (2)
Why do we need this stage? (2)
(1) lipids are split up into micelles by bile salts (produced in the liver)
(2) which is emulsification
(3) it increases the surface area of the lipids
(4) so lipase can act faster
Proteins are hydrolysed by peptidases. Describe the function of the ENDOPEPTIDASES (3)
(1) hydrolyse the peptide bonds
(2) in the CENTRAL REGION of a protein
(3) to produce peptide molecules
Proteins are hydrolysed by peptidases. Describe the function of the EXOPEPTIDASES (3)
(1) hydrolyse the peptide bonds
(2) on the TERMINAL amino acids of the peptide molecules
(3) to produce dipeptides & single amino acids
Proteins are hydrolysed by peptidases. Describe the function of DIPEPTIDASES (3)
(1) hydrolyses the peptide bond
(2) between the 2 amino acids in a dipeptide
(3) This enzyme type is membrane bound, so it is a part of the epithelial cells lining the ileum.
Suggest why the stomach doesn’t have villi or microvilli. (3)
(1) villi & microvilli inc the S.A. to speed up the absorption of soluble molecules
(2) the food in the stomach has not been hydrolysed into soluble molecules yet
(3) so the food can’t be absorbed so the villi is unnecessary
How does bile help in the activity of amylase in the small intestine? (2)
(1) it neutralises stomach acid
(2) which provides neutral pH conditions, which is the optimum pH for this enzyme
“Explain 2 ways in which bile helps the body to digest fat.” (4)
(1) it neutralises acid pH
(2) so lipase can work
(3) it emulsifies fats
(4) which provides a large S.A. for enzyme action
“The action of endopeptidases and exopeptidases can increase the rate of protein digestion. Explain how. (2)
(1) exopeptidases hydrolyse peptide bonds at the ends of a protein & endopeptidases hydrolyse internal peptide bonds in a protein
(2) more ‘ends’ / more S.A.
