Digestion and Absorption Flashcards
1
Q
Define digestion.
A
When large biological molecules are hydrolysed into smaller molecules that can be absorbed across cell membranes.
2
Q
What is the function of the mouth in digestion?
A
- Teeth break food into smaller pieces so large SA:V ratio
- Starts carbohydrate digestion by amylase in saliva
3
Q
What is the function of the oesophagus?
A
- Muscular walls contract to pass food into stomach
4
Q
What is the function of the stomach?
A
- Protein digestion begins
- Produces enzymes and stomach acid
- Churns food, mixing it with enzymes and acid (which lowers pH, breaking bonds and killing microorganisms)
5
Q
What is the function of the small intestine?
A
- Carb, protein and lipid digestion
- Absorption of food molecules into blood
- Large surface area
6
Q
What is the function of the large intestine?
A
- Absorbs any extra water
- Absorbs minerals and vitamins
7
Q
Where are carbohydrates digested?
A
- Mouth
- Small intestine
8
Q
Where are lipids digested?
A
- Stomach
- Small intestine
9
Q
Where are proteins digested?
A
- Stomach
- Small intestine
10
Q
How are carbohydrates digested?
A
- Salivary amylase in the mouth hydrolyses starch into maltose.
- Pancreatic amylase hydrolyses starch into maltose in the small intestine.
- Maltase embedded on the epithelial lining of the small intestine hydrolyses maltose into glucose.
11
Q
Where are proteins digested?
A
- Endopeptidases in the stomach hydrolyse internal peptide bonds into shorter chains (more ends increase SA:V ratio)
- Exopeptidases secreted from the pancreas into the small intestine hydrolyse end bonds of polypeptide chains
- Dipeptidases in the epithelium of the small intestine hydrolyse dipeptides into amino acids
12
Q
Where are lipids digested?
A
- Bile emulsifies large fat droplets into smaller ones to increase SA:V ratio (it also neutralises stomach acid)
- Lipase, which is secreted from the pancreas, hydrolyses triglycerides into monoglycerides and fatty acids in the small intestine
- monoglycerides and lipids stick with bile salts to form micelles, which transport them to the membrane of the epithelial cells of the small intestine. They diffuse through as the membrane is lipid soluble.
13
Q
Describe the role of the enzymes of the digestive system in the complete breakdown of starch. (5)
A
- Amylase- salivary/pancreatic
- Starch to maltose
- Maltase- small intestine
- Maltose to glucose
- Hydrolysis of glycosidic bond
14
Q
Describe how proteins are digested in the human gut. (4)
A
- Hydrolysis of peptide bonds;
- Endopeptidases break polypeptides into smaller peptide chains;
- Exopeptidases remove terminal amino acids;
- Dipeptidases hydrolyse / break down dipeptides into amino acids.
15
Q
A
