digestion and absorption

Question 1

What occurs during digestion

Answer 1

Large molecules are broken down into smaller ones which can move across cell membranes

Question 2

Why is the hydrolysis of large biological molecules important in digestion

Answer 2

Because they are broken down into monomers which are easily absorbed from the gut into the blood easily transported around the body for use by the body cells

Question 3

What is produced during the hydrolysis of carbohydrates?

Answer 3

Carbohydrates + water → disaccharides

Question 4

What is produced during hydrolysis of disaccharides?

Answer 4

Disaccharides + water → monosaccharides

Question 5

What is produced during the hydrolysis of fats?

Answer 5

Fats + water → fatty acids + monoglycerides

Question 6

What is produced during the hydrolysis of proteins?

Answer 6

Proteins + water → amino acids

Question 7

List the enzymes involved in digestion

Answer 7

1. Amylase
2. Lipase
3. Membrane-bound disaccharidases
4. Membrane-bound dipeptidases

Question 8

Describe the function of amylase

Answer 8

Amylase hydrolyses starch into maltose by hydrolysing glycosidic bonds in starch

Question 9

Where is amylase produced

Answer 9

Salivary glands and by the pancreas

Question 10

Where does amylase work in?

Answer 10

Small intestine

Question 11

Describe the function of membrane-bound disaccharidases

Answer 11

They help to hydrolyze disaccharides into monosaccharides by hydrolyzing glycosidic bonds

Question 12

Where are membrane-bound disaccharides found?

Answer 12

They are attatched to the cell membrane of epithelial cells lining the ileum

Question 13

Describe the function of lipase

Answer 13

Catalyses the hydrolysis of lipids into monoglycerides and fatty acids by hydrolysing the ester bonds in lipids

Question 14

Where is lipase made?

Answer 14

Pancreas

Question 15

Where does lipase work?

Answer 15

Small intestine

Question 16

What is the function of bile salts?

Answer 16

Emulsifying lipids to monoglycerides and fatty acids

Question 17

Where is bile salt produced?

Answer 17

Liver

Question 18

How are micelles formed?

Answer 18

When the lipid is hydrolysed by lipase, the monoglycerides and fatty acids stick with the bile salts to form micelles

Question 19

What are proteases?

Answer 19

Enzymes that catalyse the hydrolysis of proteins into amino acids by hydrolysing the peptide bonds between amino acids

Question 20

What are the types of proteases?

Answer 20

1. Endopeptidases
2. Exopeptidases
3. Dipeptidase

Question 21

What is the function of endopeptidases?

Answer 21

Hydrolyse peptide bonds in protein between amino acids in the central region into two or more smaller peptides

Question 22

What is the function of exopeptidases?

Answer 22

Hydrolyses peptide bonds at the ends of protein molecules removing a single amino acid

Question 23

What is the function of dipeptidases?

Answer 23

They act to separate the 2 amino acids that make up a dipeptide by hydrolyzing the peptide bond between them

Question 24

Where are dipeptidases found?

Answer 24

In the cell surface membrane of epithelial cells in the small intestine

Question 25

What happens to the products of digestion?

Answer 25

Products of digestion are absorbed across the ileum epithelium into the bloodstream

Question 26

Describe what happens to monosaccharides as products of digestion

Answer 26

• Glucose is absorbed by active transport with sodium ions via a co-transporter protein
• Galactose is absorbed by active transport with sodium ions via a co-transporter protein
• Fructose is absorbed via facilitated diffusion through a different transporter protein

Question 27

Describe what happens to monoglycerides and fatty acids as products of digestion

Answer 27

• Micelles help to move monoglycerides and fatty acids toward the epithelium.
• Because micelles constantly break up and reform they can release monoglycerides and fatty acids, allowing them to be absorbed
• Monoglycerides and fatty acids are lipid-soluble so they can diffuse directly across the epithelial cell membrane

Question 28

Describe what happens to amino acids as products of digestion

Answer 28

Sodium ions are actively transported out of the epithelial cells to the ileum, they diffuse back into cells through sodium-dependent transporter proteins in epithelial cell membranes carrying amino acids with them