Digestion and Absorption Flashcards
1
Q
What is digestion?
A
the hydrolysis of large biological molecules into smaller molecules which can be absorbed across cell membranes
2
Q
How are carbohydrates digested?
A
- amylase in saliva hydrolyses large carbohydrate polymers (starch)
- maltase in the ileum break down monosaccharides
- sucrase breaks down sucrose
- lactase breaks down lactose
3
Q
How are lipids digested?
A
- lipases hydrolyse the ester bond between the monoglycerides and fatty acid
- lipids are emulsified into micelles by bile salts released by the liver
4
Q
why does emulsification occur?
A
it increases the surface area and speeds up the chemical reaction
5
Q
How are proteins digested?
A
by enzymes called peptidases
6
Q
What are the types of peptidases?
A
- exo
- endo
- di
7
Q
what are the function of exopeptidase?
A
it hydrolyses bonds at ends of a polypeptides
8
Q
what are the function of endopeptidase?
A
it hydrolyses peptide bonds between specific amino acids in the middle of a polypeptide
9
Q
what are the function of dipeptidase?
A
break dipeptides into individual amino acids
10
Q
How are amino acids absorbed?
A
- co-transport
- facilitated diffusion through specific carrier molecule in the surface membrane of epithelial cells
- With each amino acid, one Na+ is also taken up via active transport through the base of epithelial cells (which maintains diffusion gradient)
11
Q
How are monoglycerides absorbed after digestion?
A
- Monoglycerides and fatty acids are polar so they can easily diffuse into the epithelial cells lining the epithelium.
- Once inside they are transported to the
endoplasmic reticulum where they are reformed into triglycerides again - After this they move out of the cells by vesicles into the lymph system
