Digestion and absorption Flashcards
1
Q
- What is digestion?
2. Why is digestion required?
A
- During digestion large molecules are broken down into smaller molecules, which can move across cell membranes . This means that they can be easily absorbed from the gut, into the blood to be transported around the body for use by the body cells.
- Large biological molecules in food are too big to cross cell membranes
2
Q
Amylase?
A
- Catalyses the breakdown of starch
- Amylase is produced by the salivary glands, which release amylase into the mouth
- It is also produced by the pancreas, which releases amylase into the small intestine
3
Q
Digestion of carbohydrates by amylase
A
Amylase works by catalysing hydrolysis reactions that break the glyosidic bonds in starch to produce maltose
4
Q
What are membrane bound disaccharidases?
A
- Membrane-bound disaccharidases are enzymes that are attached to the cell membranes of epithelial cells lining the ileum.
- They help to break down disaccharides into monosaccharides.
(involves the hydrolysis of glycosidic bonds) - The monosaccharides can be transported across the epithelial cell membranes in the ileum via specific carrier proteins
5
Q
How are carbohydrates digested?
A
- Breakdown of Large Insoluble Molecules into Small Soluble Molecules (so they can move into the blood and then into the body cells)
- Starch/Glycogen (Carbohydrates) into Glucose by Amylase (Salivary in mouth, Pancreatic in small intestine)
- Maltase/Lactase/Sucrase (on lining of small intestine)
(membrane bound disaccharidases)
6
Q
Which enzyme breaks down lipids?
A
- Lipase breaks down lipids into monoglycerides and fatty acids
7
Q
Where is lipase made?
A
- Lipase is made mainly in the pancreas, then secreted into the small intestine where they act
8
Q
Digestion of lipids?
A
- Lipids into monoglycerides and fatty acids by lipase (hydrolysis of ester bonds)
- Bile salts are produced by the liver and emulsify lipids
- cause lipids to form small droplets
- Several small lipid droplets have a larger surface area than a single large droplet (for the same volume of lipid)
- Formation of small droplets greatly increases the surface area of lipids that’s available for lipase to work on
- Once the lipid has been broken down by lipase, the monoglycerides and fatty acids stick together to form micelles
- Micelles help the product of lipid digestion to be absorbed
9
Q
Digestion of proteins?
A
- Endopeptidase (in stomach), hydrolyses peptide bonds within a protein
- Exopeptidase (in small intestine), hydrolyses peptide bonds at the end of protein molecules
- Dipeptidase (on lining of small intestine), hydrolyse dipeptides into amino acids (hydrolyse peptide bond between them)
10
Q
Endopeptidase?
A
- Endopeptidase (in stomach), hydrolyses peptide bonds within a protein (into smaller chains)
11
Q
Exopeptidase?
A
-Exopeptidase (in small intestine), hydrolyses peptide bonds at the end of protein molecules
12
Q
Dipeptidase?
A
-Dipeptidase (on lining of small intestine), hydrolyse dipeptides into amino acids (hydrolyse peptide bond between them)
13
Q
Absorption of monosaccharides?
A
- Glucose is absorbed by active transport with sodium ions via co-transporter protein
- Galactose is absorbed in the same way using the same co-transporter protein
14
Q
Absorption of monoglycerides and fatty acids?
A
- Micelles help to move monoglycerides and fatty acids towards the epithelium
- monoglycerides and fatty acids are lipid-soluble, so can diffuse directly across the epithelial cell membrane
15
Q
Absorption of amino acids?
A
- Sodium ions ae actively transported out of the epithelial cells into the ileum
- They then diffuse back into the cells through sodium-dependent transporter proteins in the epithelial cell membrane, carrying the amino acids with them
