Human Digestive System Flashcards
1
Q
Features of cells in villi
A
- Microvilli to increase SA for diffusion and uptake of digested molecules
- Mitochondria for synthesis of ATP for active transport
2
Q
Function of goblet cells
A
- Secrete/ make mucus
- Lubricates food and reduces friction for passage of food
- Prevents digestion of the gut wall by enzymes acting on it and effect of acid
3
Q
Features of villus
A
- Microvilli and folded epithelium: increase/ provides large SA for greater absorption and diffusion of digested products
- Dense capillary network: maintain a diffusion and concentration gradient and transports glucose and amino acids
- Lacteal: absorbs lipids and fats
- Thin epithelium: short diffusion pathway
4
Q
Fate of amino acids
A
- Undergo deamination in the liver (amino group removed)
- Amino groups converted to urea
- Remainder converted to carbohydrate/ glycogen and used for respiration
5
Q
Bile (bile salts and hydrogen carbonate ions)
A
- Bile salts emulsify lipids = break large lipid droplets into manny smaller lipid droplets or globules
- Increases total SA of lipids = increases the rate of digestion of lipids as broken down more quickly by lipase
- Hydrigen carbonation ions (alkaline) = optimum pH for enzymes and to neutralise stomach acid
6
Q
Smooth muscles in small intestine
A
- Circular and longitudinal muscles contract
- Forces food along so causes peristalsis
- Move villus to change materials in contact with it
7
Q
Bile experiment
A
- Add full cream milk (more fatty acids produced and quicker change)
- Add lipase and phenolphthalein
- Hydrolysis of lipids releases fatty acids reducing pH and colourless
- With bile- presence of bile salts causes emulsifying of lipids, increasing SA for action of lipase. pH becomes acidic more quickly as fatty acids released more quickly
8
Q
Why are enzymes released in inactivated form?
A
To prevent autolysis or self-digestion of tissue or gland that secreted it
9
Q
Absorption
A
Passage of digested food through the gut wall into bloodstream
10
Q
Exo and endopeptidases
A
Endopeptidases cut in middle of polypeptide chain into several smaller chains
Produces more free ends for exopeptidases to act on
11
Q
Coeliac Disease
A
- Loss of villus height and breakdown of microvilli
- Reduced SA
- Reduced absorption and uptake of materials
- Digestive enzymes absorbed or part of the membrane
- SA reduced for enzymic action = less efficiency of digestive enzymes
12
Q
Mechanical digestion
A
- Teeth chew and grind the food
- Contraction of stomach/ gut which mixes and churns food
13
Q
Effect of ammonia
A
- Ammonia is toxic to epithelial cells lining gastric glands
- Less mucus produced as cells killed
- More HCl produced to compensate for neutralisation of NH3
- HCl can damage and erode the lining of stomach wall
- Pepsin can cause autolysis or dself-digestion
