3.3 Digestion and absorption Flashcards
Define digestion
The hyrdolysis of large, insoluble molecules into smaller molecules that can be absorbed across cell membranes
Which enzymes are involved in carbohydrate digestion?
- Amylase
- Maltase
- Sucrase
- Lactase
Where are the enzymes involved in carbohydrate digestion found?
- Amylase in mouth
- Maltase, sucrase, lactase in the membrane of the small intestine
What are the substrates and products of the carbohydrate digestive enzymes?
- Amylase –> starch into smaller polysaccharides
- Maltase –> maltose into 2x glucose
- Sucrase –> sucrose into glucose and fructose
- Lactase –> lactose into glucose and galactose
Where are lipids digested?
The small intestine
What needs to happen before lipids can be digested?
They must be emulsifies by bile salts produced by the liver. This breaks down large fat molecules into smaller, soluble molecules called micelles, increasing surface area
How are lipids digested?
Lipase hydrolyses the ester bond between the monoglycerides and fatty acids
Which enzymes are involved in protein digestoin?
- Endopeptidases
- Exopeptidases
- Dipeptidases
What is an endopeptidases role?
Break between specific amino acids in the middle of a polypeptide
What is an exopeptidases role?
Break between specific amino acids at the end of a polypeptide
What is a dipeptidases role?
Break between dipeptides into amino acids
How are certain molecules absorbed into the ileum despite a negative concentration gradient?
Co-transport
Which molecules require co-transport?
Amino acids and monosaccharides
Explain how sodium ions are involved in co-transport
Sodium ions are actively transported out of the cell into the lumen, creating a diffusion gradient. Nutrients are then taken up into the cells along with sodium ions
Why do fatty acids and monoglycerides not require co-transport?
The molecules are non-polar, meaning they can easily diffuse across the membrane of the epithelial cells
