Digestion and Absorbtion

Question 1

Why is digestion needed?

Answer 1

• Large molecules in foods are too big to cross cell membranes meaning they can’t be absorbed into blood from gut
• Broken down into smaller molecules during digestion so they can move easily across meme ranges and b absorbed and transported

Question 2

Polymers are broken down into monomers, what are the monomers of carbohydrates, fats and proteins?

Answer 2

Carbohydrates - disaccharides then monosaccharides
Fats - fatty acids and monoglycerides
Proteins - amino acids

Question 3

How does amylase break down carbohydrates?

Answer 3

Catalysts the conversion of starch (polysaccharide) into maltose (disaccharide) through the hydrolysis of glycosidic bonds in starch.

Question 4

Where does amylase come from?

Answer 4

Produced in salivary glands (release it into mouth) and by pancreas (release it into small intestine).

Question 5

What are membrane bound disaccharides?

Answer 5

Enzymes attached to cell membranes of epithelial cells lining ileum.

Question 6

What do membrane bound monosaccharides do?

Answer 6

Break disaccharides down into monosaccharides through the hydrolysis of glycosidic bonds.

Question 7

Describe the disaccharidase and monosaccharide products for maltose.

Answer 7

Maltase

Glucose and glucose

Question 8

Describe the disaccharidase and monosaccharide products for sucrose.

Answer 8

Sucrase

Glucose and fructose

Question 9

Describe the disaccharidase and monosaccharide products for lactose.

Answer 9

Lactase

Glucose and galactose

Question 10

How does lipase and bile salts break down fats?

Answer 10

Lipase catalysts the breakdown of lipids into monoglycerides and fatty acids via the hydrolysis of ester bond. Bile salts emulsify lipids increasing the SA of lipid for lipase to work on. Monoglycerides and fatty acids stick to bile salts creating micelles.

Question 11

Where does lipase come from and where does it work?

Answer 11

Made in pancreas and work in small intestine.

Question 12

Where do bile salts come from?

Answer 12

Produced in liver.

Question 13

What are peptidases?

Answer 13

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

Question 14

What do endopeptidases?

Answer 14

Hydrolyse peptide bonds within protein.
Trypsin and chymotrypsin synthesised in pancreas and secreted in small intestine.
Pepsin released in stomach by cells in stomach lining - only works in acidic conditions.

Question 15

What do exopeptidases do?

Answer 15

Hydrolysis peptide bonds at the end of proton molecules.
Dipeptidases work specifically on dipeptides, separating the two amino acids by hydrolysing the peptide bond.
Located on cell surface membrane of epithelial in small intestine.

Question 16

How are monosaccharides absorbed across cell membranes?

Answer 16

Glucose and galactose absorbed by active transport with sodium ion via cotransport protein.
Fructose by facilitated diffusion.

Question 17

How are monoglycerides and fatty acids absorbed across cell membranes?

Answer 17

Micelles help move monoglycerides and fatty acids towards epithelium where they break up releasing monoglycerides and fatty acids which diffuse directly across the epithelial cell membrane as they are water soluble.

Question 18

How are amino acids absorbed across cell membranes?

Answer 18

Sodium ions active,y transported out of epithelium into ileum, they then diffuse back into epithelium cells through sodium dependent transport proteins in cell membranes carrying the amino acids with them.