3.3 Digestion and absorption Flashcards
Define digestion
The hydrolysis of large, insoluble molecules into smaller molecules that can be absorbed across cell membrane.
Which enzyme are involved in carbohydrates digestion? Where are they found?
- Amylase in mouth
- Maltase, sucrase, lactase in membrane of small intestine
What are the substrates and products of the carbohydrates 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 emulsified 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.
What enzymes are involved in protein digestion?
What is their role?
Endopeptidases = break between specific amino acids in the middle of a polypeptide
Exopeptidases = break between specific amino acids at the end of a polypeptide.
Dipeptidases = break dipeptides into amino acids.
How are certain molecules absorbed into the ileum despite a negative concentration gradient?
Through 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.
