3.3-Digestion and Absorption Flashcards
Define digestion.
The hydrolysis of large insoluble molecules into smaller, soluble molecules that can be absorbed across cell membranes.
Which enzymes are found in carbohydrate digestion and where are they found?
- Amylase in mouth.
- Maltase, sucrase and lactase in membrane of small intestine.
What are the substrates and products of the carbohydrate digestive enzymes?
- Amylase: starch into smaller polysaccharides.
- Maltase: Maltose into 2 glucose.
- Sucrase: Sucrose into glucose and fructose.
- Lactase: Lactose into glucose and galactose.
Where are lipid digested?
In 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 the fat molecules into smaller, soluble molecules called micelles, increasing surface area.
How are lipids digested?
Lipase hydrolyses the ester bonds between the monoglycerides and fatty acids.
Which enzymes are involved in protein digestion and what are their roles?
- 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 ilium 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 into cells along 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.
