Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

HUBS192 Missing Cards > Lecture 26: Digestion > Flashcards

Lecture 26: Digestion Flashcards

1
Q

What are the main nutrients that undergo chemical digestion?

A
  • carbohydrates (sugars)
  • proteins
  • lipids
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what are carbohydrates good for?

A
  • important source of energy
  • storage polysaccharides
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is the structure of carbohydrates?

A

large complex chains of monosaccharides
e.g. glucose is a monosaccharide

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what are most common of sources of carbohydrates?

A
  • starch
  • glycogen
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what is the composition of starch and glycogen?

A

long chains of glucose joined by alpha 1-4 glycosidic bonds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what are common forms of disaccharides? what are the composed of?

A

Sucrose
- glucose and fructose

Lactose
- glucose and galactose

Maltose
- Glucose and glucose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what do we ingest a limited amount of?

A

monosaccharides - glucose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what is protein like in food?

A
  • ingest 70-100g per day of proteins in food
  • not a major source of energy
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what are proteins needed for?

A

amino acids
- there are 20 amino acids
- 12 can be synthesised
- others essential, cannot be synthesised (e.g. histidine, leucine, lysine)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what are the sources of protein?

A
  • 50% diet
  • 50% endogenous proteins, enzymes and immunoglobulins secreted into small intestine
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what is the structure of ingested proteins?

A

long chains of amino acids linked by peptide bonds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what are lipids like in food?

A
  • 100-150g/day
  • not essential
  • important source of energy
  • has fat soluble vitamins A,D,E,K
  • slows gastric emptying
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what is the main structure of lipids?

A

Mainly triglycerides
- glycerol backbone with 3 fatty acids attached

Fatty acids variable chain length
- short chain (less than 6 carbons)
- medium chain (6-12 carbons)
- long chain (12-24 carbons)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

why do we need chemical digestion?

A
  • we ingest nutrients in the form of large complex molecules, but can only absorb nutrients as small molecules.
  • chemical digestion reduces the size of nutrients to allow them to be absorbed
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

where does chemical digestion occur?

A

at the surface of food particles
- mechanical digestions breaks up food to increase surface area available for chemical digestion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what does chemical digestion utilise to function?

A

digestive enzymes

17
Q

what are features of digestive enzymes?

A
  • extracellular
  • they are organic catalysts
  • they are very specific so different enzymes are needed for different substrates (e.g. amylase, protease, lipase)
  • have optimal pH
18
Q

what is the optimal pH of salivary, gastric and small intestinal enzymes?

A

salivary - alkaline
gastric - acidic’
small intestinal - alkaline

19
Q

what is cellulose and its structure?

A
  • structural polysaccharide of plants
  • large amount of cellulose in diet
  • long chains of beta 1-4 glycosidic bonds
20
Q

what are the 2 stages of chemical digestion?

A
  • luminal digestion
  • contact digestion
21
Q

what does luminal digestion involve?

A

initial digestion involving enzymes secreted into the lumen:
- salivary glands secrete salivary amylase
- stomach secretes pepsin
- small intestine has pancreatic enzymes (pancreatic amylase, trypsin, chymotrypsin, carboxypeptidase, lipase)

22
Q

what does contact digestion involve?

A
  • occurs in small intestine
  • completes digestion before absorption
  • involves enzymes produces by enterocytes and attached to brush border of enterocytes
23
Q

what happens in the luminal digestion of carbohydrates?

A
  • uses salivary and pancreatic amylase
  • polysaccharides converted into oligosaccharides and disaccharides
24
Q

what happens in the contact digestion of carbohydrates?

A
  • contact digestion of brush border disaccharidases
  • disaccharides are converted into monosaccharides
  • involved sucrase, lactase, maltase and others bound to brush border
25
Q
A

carbohydrate digestion summary

26
Q

what happens in the luminal digestion of proteins?

A
  • involves pepsin in stomach
  • involves trypsin and chymotrypsin in small intestine
  • involves carboxypeptidase in small intestine
  • convert proteins into polypeptides
27
Q

what happens into contact digestion of proteins?

A
  • involved peptidases
  • there are many different types attached to brush border
  • converts polypeptides into individual amino acids
28
Q
A

chemical digestion of proteins summary

29
Q

where does chemical digestion of lipids occur? what does it involve?

A
  • occurs in lumen of small intestine
  • No contact digestion!
  • pancreatic lipase is main digestive enzyme
  • lingual lipase and gastric lipase have minor role
30
Q

what is the problem with lipid digestion?

A
  • digestive enzymes are dissolved in aqueous luminal fluid
  • this is no problem for carbohydrates and proteins as they are soluble in water
  • lipids are insoluble in water so they need a more complex process
31
Q

what are the stages of lipid digestion?

A
  • emulsification
  • stabilisation
  • digestion (hydrolysis)
  • formation of micelles
32
Q

what happens in emulsification? where does it occur?

A

1st stage of fat digestion:

Motility breaks up lipid droplets into small droplets
- forms an emulsion that increases surface area for digestion

  • simple emulsion occurs in the stomach (retropulsion)
  • more complex emulsion occurs in small intestine (segmentation) and bile salts stabilise droplets
33
Q

what happens in stabilisation? where does it occur?

A

2nd stage of fat digestion:
- occurs in the small intestine

  • involves bile salts which are secreted by the liver and concentrated in the gallbladder
  • it is released into the small intestine with the arrival of food
  • has a hydrophobic and hydrophilic side
  • they stabilise the emulsion in the small intestine and reduce the size of the emulsion droplets to further increase surface area
34
Q

what happens in hydrolysis? where does it occur?

A

3rd stage of lipid digestion
- occurs in small intestine at surface of emulsion droplets

  • involves lipase and cofactor colipase
  • both are secreted by the pancreas
  • colipase anchors lipase to the surface droplet
  • lipase converts triglycerides to monoglycerides and free fatty acids
35
Q

what happens in formation of micelles? what are micelles?

A

4th stage of fat digestion

  • products of fat digestion are insoluble in water, especially monoglycerides and long chain fatty acids
  • so they are kept in solution through the formation of micelles
  • micelles are small droplets consisting of 20-30 molecules of bile salts, fatty acids and monoglycerides
36
Q

steps of fat digestion

A

HUBS192 Missing Cards (31 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions