Lecture 26: Chemical Digestion Flashcards
(74 cards)
1
Q
What are the 3 main nutrients that undergo chemical digestion?
A
- Carbohydrates (Sugars)
- Proteins
- Lipids (Fats)
2
Q
Whare are carbohydrates an important source of?
A
Energy
3
Q
How are carbohydrates stored?
A
Polysaccharides
4
Q
What is a polysaccharide?
A
Large complex chain of monosaccharides
5
Q
What is glucose an example of?
A
A monosaccharide
6
Q
What is starch a long chains of?
A
Glucose
7
Q
What are the long chains of glucose connected by in starch and glycogen?
A
alpha 1-4 glycosidic bonds
8
Q
What are 3 examples of disaccharides?
A
- Sucrose
- Lactose
- Maltose
9
Q
What is Sucrose made of?
2
A
- Glucose
- Fructose
10
Q
What is Lactose made of?
2
A
- Glucose
- Galactose
11
Q
What is Maltose made of?
A
2 Glucose
12
Q
What do we ingest a limited amount of?
A
Monosaccharides e.g. glucose
13
Q
Proteins are not a source of what?
A
Energy
14
Q
What are proteins required for?
A
Amino acids
15
Q
How many amino acids do we have?
A
21
16
Q
How many amino acids can we synthesise?
A
12
17
Q
How do we acquire the amino acids that can’t be synthesised?
A
Through our diet
18
Q
What are 2 sources of protein?
A
- Diet
- Endogenous proteins
19
Q
What can proteins be secreted into the intestine as?
2
A
- Enzymes
- Immunoglobulins
20
Q
What is the structure of ingested amino acids?
A
Long chains of amino acids connected by peptide bonds
21
Q
Is fat essential to our diet?
A
No
22
Q
What is fat an important source of?
A
Energy
23
Q
What do lipids do to gastric emptying?
A
Slow it down
24
Q
What are triglycerides?
A
Glycerol back bone with 3 fatty acids attached
25
what is a short chain fatty acid?
< 6 carbons
26
what is a medium chain fatty acid?
6 to 12 carbons
27
what is a long chain fatty acid?
12 to 24 carbons
28
Why do we need chemical digestion?
Ingest nutrients in the form of large complex molecules
29
What can we only absorb nutrients as?
Small molecules
30
What does chemical digestion do to the size of nutrients?
Reduces their size to allow them to be absorbed
31
Where does chemical digestion occur?
On the surface of food particles
32
What does mechanical digestion do?
Breaks up food increasing its surface area available for chemical digestion
33
What does chemical digestion utilise?
digestive enzymes
34
What is the equation that shows digestive enzymes are organic catalysts?
E + S -> ES -> E + P
35
How are digestive enzymes very specific?
They have different enzymes for different substrates
36
Each enzyme has a particular what?
pH that it works optimally at
37
What type of pH do salivary enzymes like?
Alkaline
38
What type of pH do gastric enzymes like?
Acidic
39
What type of pH do small intestinal enzymes like?
Alkaline
40
What are the 2 stages of chemical digestion?
- Luminal digestion
| - Contact digestion
41
What does luminal digestion involve?
Enzymes being secreted into the lumen
42
What do the Salivary glands, Stomach and Small Intestine secret into the lumen respectively?
- Salivary amylase
- Pepsin
- Pancreatic enzymes
43
What are the pancreatic enzymes released by the small intestine during luminal digestion?
(5)
- Pancreatic amylase
- Trypsin
- Chymotrypsin
- Carboxypeptidase
- Lipase
44
Where does contact digestion occur?
In the small intestine
45
What does contact digestion do?
Completes digestion before absorption
46
What does contact digestion involve?
Enzymes produced by enterocytes which are attached to the brush border
47
What happens during the chemical digestion of carbohydrates in the luminal digestion phase?
Salivary and pancreatic amylase convert polysaccharides into oligosaccharides and down further into disaccharides
48
What happens during the chemical digestion of carbohydrates in the contact digestion phase?
Disaccharides are converted to monosaccharides
49
What are the enzymes involved in breaking down disaccharides to monosaccharides during contact digestion?
(3)
- Sucrase
- Lactase
- Maltase
50
What are the enzymes Sucrase, Lactase and Maltase attached to?
The brush border
51
What does pepsin in the stomach trypsin, chymotrypsin and carboxypeptidase in the small intestine secreted by the pancreas do during luminal digestion of proteins?
Converts proteins to polypeptides
52
What does contact digestion of proteins involve?
Peptidases
53
What do many types of peptidases for contact digestion of proteins attach to?
The brush border
54
What do peptidases of contact digestion of proteins do?
Convert polypeptides into individual amino acids
55
Where does chemical digestion of fats occur?
In the lumen of the small intestine
56
What is the main digestive enzyme involved with chemical digestion of fats?
Pancreatic lipase
57
What have minor roles in the chemical digestion of fats?
| 2
- Lingual lipase
| - Gastric lipase
58
What is the problem for lipid digestion?
Digestive enzymes dissolve in water but fats aren't water soluble
59
What are the 4 main stages of chemical digestion of fats?
- Emulsification
- Stabilisation
- Digestion (Hydrolysis)
- formation of micelles
60
What does motility of emulsification do?
breaks up lipid droplets into small droplets increasing surface area
61
Where does simple emulsification occur and what is performed?
Stomach and performs retropulsion
62
Where does more complex emulsification occur and what is performed?
Small intestine and performs segmentation
63
What do bile salts do?
Stabilise fat droplets which result from emulsification in the small intestine
64
Where does stabilisation of lipids occur?
Small intestine
65
What are bile salts secreted by?
Liver
66
Where are bile salts concentrated?
Gallbladder
67
When and where are bile salts releases?
With the arrival of food into the small intestine
68
How can the structure of bile salts be described?
Hydrophobic (water hating side) and a charged hydrophilic (water loving side)
69
Where does hydrolysis of lipids occur?
In the small intestine at the surface of the emulsion droplets
70
What does hydrolysis of lipids involve?
| 2
- Lipase
| - Cofactor colipase
71
What are lipase/cofactor colipase secreted by?
pancreas
72
What does colipase do?
Anchors lipase to the surface of droplets
73
What does lipase convert triglyceride to?
| 2
- Monoglyceride
| - Free fatty acids
74
What occurs during the formation of micelles in fat digestion?
The products of fat digestion are kept in solution through the formation of micelles
