Chapter 2: Carbohydrates Flashcards
(100 cards)
1
Q
What do disaccharides consist of?
A
Two monosaccharides united by a glycosidic linkage.
2
Q
How are disaccharides classified?
A
They are classified according to their reducing power ( Fehling or Benedict).
3
Q
What are the types of disaccharides?
A
Reducing and non reducing.
4
Q
What are the differences between reducing and non reducing?
A
Reducing:
1. Free anomeric carbons.
2. Contains alpha and beta forms.
None reducing:
1. No free anomeric carbons. Both are involved in glycosidic linkage.
2. Does not have alpha and beta forms.
5
Q
What are reducing disaccharides?
A
Maltose, isomaltose, and lactose.
6
Q
What are none reducing disaccharides?
A
Sucrose
7
Q
Maltose Other name.
A
Malt sugar.
8
Q
Maltose structure
A
2 molecules of D-glucose.
9
Q
Maltose obtained by?
A
Action of amylase enzyme on starch.
10
Q
Maltose hydrolyzing enzyme
A
Maltase.
11
Q
Maltose hydrolysis product
A
2 molecules of D-glucose.
12
Q
Maltose linkage.
A
a1-4 glucosidic linkage
13
Q
Why are reducing disaccharides reducing?
A
Because they have a free anomeric carbon at the 2nd sugar unit. They are also present in alpha and beta forms.
14
Q
Isomaltose structure
A
2 molecules D-glucose.
15
Q
Isomaltose linkage
A
a1-6 glucosidic linkage.
16
Q
Isomaltose obtained by?
A
Action of amylase enzyme on starch at branching points.
17
Q
Isomaltose Hydrolyzing enzyme
A
Isomaltase.
18
Q
Isomaltose hydrolysis product
A
2 molecules of D-glucose.
19
Q
Isomaltose hydrolysis product
A
2 molecules of D-glucose.
20
Q
Lactose other name
A
Milk sugar.
21
Q
Lactose structure
A
B. D-galactose
And D-glucose
22
Q
Lactose linkage
A
B1- 4 galactosidic linkage
23
Q
Lactose obtained by:
A
Present in milk.
24
Q
Lactose hydrolyzing enzyme
A
Lactase.
25
Lactose Hydrolysis product
D-Galactose
And D-Glucose
26
Sucrose other names
Cane sugar/ table sugar.
27
Sucrose structure
a. D-glucopyranose, B. D- fructofuranose.
28
Sucrose linkage
a1-2 glucosidic linkage
B2-1 fructosidic linkage.
29
Sucrose present in?
Cane and beets
30
Sucrose Hydrolyzing enzyme
Sucrase.
31
Sucrose hydrolyzing product
D-glucose and D-Fructose.
32
Why are some disaccharides non reducing?
Because they have no free anomeric carbons. They are all involved in the glycosidic linkage, thus they have no a or B forms.
33
Polysaccharides are divided into two types.
Homopolysaccharides and heteropolysaccharides.
34
Homopolysaccharides
Contain only one type of monosaccharides.
35
Heteropolysaccharides
Contain more than 1 type of monosaccharides.
36
How are Homopolysaccharides named?
According to their building unit.
37
What are homopolysaccharides divided into?
Glucans and Fructans.
38
Glucans building unit is?
D-Glucose units.
39
Glucans include?
1. Starch
2. Dextrin
3. Glycogen
4. Cellulose
40
Fructans building unit is?
D-Fructose units.
41
Fructans include?
Inulin
42
Where is inulin found?
In plants.
43
What is starch?
Storage form of carbohydrates in plants.
44
What are sources of starch?
1. Plants
2. Cereals (rice and wheats)
3. Legumes (beans)
4. Tubers (potatoes)
45
What are types of starch granules?
Amylose and amylopectin.
46
Amylose percentage
15%
47
Amylopectin percentage
85%
48
Amylose location
Inner part of starch granules.
49
Amylopectin location
Outer part of starch granules.
50
Amylose structure
Linear.
51
Amylopectin structure
Branched
52
Amylose linkage
United by a1-4 D- Glucosidic linkage
53
Amylopectin linkage
United by a1-4 glucosidic linkage and a1-6 glucosidic linkage at branching points.
54
Amylose hydrolysis product
Hydrolyzed by a-amylase to maltose then to D-glucose.
55
Amylopectin hydrolysis product
Hydrolyzed by a-amylase into maltose and isomaltose to D-Glucose
56
Dextrins
Produced during partial hydrolysis of starch by salivary or pancreatic amylase.
57
Glycogen
The storage form of carbohydrates in animals.
58
Glycogens structure
Similar to amylopectin but more branched.
59
How much of the wet weight of the liver does glycogen form?
10%.
60
How much weight does glycogen form in the muscles?
1-2%.
61
Glycogen molecular weight.
Higher molecular weight.
62
Glycogen; hydrolysis products.
Hydrolyzed by a-amylase to maltose and isomaltose into D-Glucose.
63
Cellulose
Linear polymer of B, D-Glucose.
64
Cellulose linkage
B1-4glucosidic linkage.
65
Cellulose Site
Plants: Eg. Vegetables and cotton
66
Cellulose structure
Parallel chains helped by hydrogen bonds between OH of glucose units.
67
Cellulose and water
Insoluble
68
Cellulose hydrolysis
Hydrolyzed by strong acids or cellulose enzyme in bacteria.
69
Cellulose hydrolysis products:
Full hydrolysis by acids: D-Glucose
Partial hydrolysis by cellulose enzyme: celloboise (reducing disaccharide).
70
Why is cellulose no digested?
Because it can’t be Hydrolyzed by amylase enzyme as amylase is specific only to a-glucosidic linkage and the linkage in cellulose is B1-4 glucosidic linkage.
71
Why is cellulose important in diet?
It helps prevent constipation.
As it is not digested, it increases the bulk of food which in return stimulates intestinal contractions. This results in the prevention of constipation.
72
What are the most important members of heteropolysaccharides?
Gylocosaminoglycans (GAGs) and Proteoglycans.
73
GAGS
Composed of more than 50 units of unbranched long chain heteropolysaccharides.
74
GAGs Composition
Usually formed of Uronic acid and amino sugar.
75
What are two types of GAGs?
Sulfate free and sulfate containing GAGs.
76
Sulfate free GAGs
Hyaluronic acid
77
Sulfate containing GAGs
1. Chondroitin sulfate
2. Heparin
3. Heparan sulfate
4. Dermatan sulfate
5. Keratan sulfate
78
What are proteoglycan?
GAGs that are covalently linked to a protein core.
79
Proteoglycans structure
95% carbohydrates and 5% proteins.
80
Importance of GAGS.
CALLCA
81
C
Components of extracellular matrix.
82
A
Attract water by osmotic pressure into the extracellular matrix which causes swelling as GAGs ( present in Proteoglycans) are polyanions, they bind with cations like Na+ and K+ which attracts water and from hydrogen bonds with water molecules.
83
L
Lubricants in synovial fluid.
84
L
Limit the passage of large molecules into the extracellular matrix allowing passage of smaller molecules as Ca and H2O, which form gels at low concentrations. This provides flexible mechanical support. ( GAGs act as filters).
85
C
Compressibility of cartilage and resilience of the eyeball as cartilage is rich in Proteoglycans which contain GAGs (polyanionic) which contain water.when exposed to pressure, water is squeezed out and when compression is released, it regains hydrated size.
86
A2
Aggrecan formation.
87
What is Aggrecan?
A major proteoglycan present in cartilage.
88
What do Aggrecan contain?
KCH
Keratan sulfate, Chondroitin sulfate, and hyaluronic acid.
89
The three GAGs are attached to?
A protein core.
90
What is the structure of Aggrecan?
Brush bottle appearance.
91
GAGs binding.
Their side chains bind electrostatically to collagen.
92
How do GAGs help in compressibility of cartilage.
GAGs are negatively charged and repel eachother but attract water and forms a gel which helps the compressibility of the cartilage.
93
What happens to the structure of GAGs with age?
It changes.
94
Hyaluronic acid proteoglycan
1. Lubricant and shock absorbent.
2. Important for cell migration and morphogenesis.
3. Concentration is increased in cases of wound healing. Repair.
4. Hyaluronidase enzyme (spreading factor).
95
Age related spread in old people due to?
Due to the replacement of Hyaluronic acid in synovial fluid ,which is a good lubricant, by dermatan sulfate, a bad lubricant.
96
Hyaluronidase enzyme (spreading factor).
1. Caps of sperms: helps fertilization.
2. Some types of bacteria: Hydrolyzed Hyaluronic acid present in the ground substance of connective tissue so it can help spread infection.
97
Dermatan sulfate
1. Important for maintenance of structure.
2. Shape of sclera of the eye.
98
Keratan Sulfate proteoglycan
Important for corneal transparency.
99
Heparin proteoglycan functions
- Anticoagulant:
1. Binds factors IX and XI.
2. Activates antithrombin.
- Releases the enzyme lipoprotein Lipase (LPL) from the capillary wall to the plasma.
This enzyme helps in the removal of lipids from blood, which is why heparin is a clearing factor).
100
Heparan sulfate proteoglycan
1. Associated with plasma membrane.
2. Cell-cell interaction
3. Cell membrane receptor.
