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Miller OnRamps Biology > Carbohydrates > Flashcards

Carbohydrates Flashcards

1
Q

Functions of carbohydrates

A
  • Supply of carbon for synthesis
  • Form structural components (in cells/ tissues)
  • Energy storage
    • Starch
    • Glycogen
  • Energy for:
    • DNA
    • RNA
    • ATP
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2
Q

Give the categories of carbohydrate

A
  • Monosaccharides
  • Disaccharides (2 monosaccharides)
  • Oligosaccharides (3-10 monosaccharides)
  • Polysaccharides (10+ monosaccharides)
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3
Q

Give the classifications of monosaccharide

A
  • Triose (3C)
  • Tetrose (4C)
  • Pentose (5C)
  • Hexose* (6C)

*Can form a 5-membered ring

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4
Q
A

Glyceraldehyde

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5
Q
A

Dihydroxyacetone

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6
Q
A
  • Ribose
  • Deoxyribose
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7
Q
A

Ribulose

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8
Q
A
  • Glucose
  • Galactose
  • Mannose
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9
Q
A

Fructose

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10
Q

Monosaccharide classification is based on…

A

Functional groups

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11
Q

The functional group of aldoses

A

Aldehyde group (CHO)

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12
Q

The functional group of ketoses

A

Ketone group (CO)

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13
Q

Optical rotation: Plane of polarised light rotation

A
  • Right: +
  • Left: -
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14
Q

Anomers

A
  • Epimers occurring after cyclization
  • Alpha-D-(+)-glucopyranose
  • Beta-D-(+)-glucopyranose
  • Reflect a change at the:
    • Hemiacetal carbon (C1)
    • Hemiketal carbon (C1)
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15
Q

Location of -OH group in alpha/beta-D-(+)-glucopyranose

A

At C1:

  • Alpha: Below the ring
  • Beta: Above the ring
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16
Q

Glucose structure

A
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17
Q

Galactose structure

A
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18
Q
A

Mannose structure

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19
Q

Sugar acids

A
  • Aldehyde at C1 is oxidised to a -COOH group

E.g:

  • Gluconic acid
  • Glucuronic acid
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20
Q

Aminosugars

A
  • Amino group substitutes for 1 or 2 of the -OH
  • The amino group may be acetylated
  • Example: Glucosamine
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21
Q

Sugar alcohols

A
  • Lack of an aldehyde/ketone group
  • Reduced to alcoholic groups
  • E.g:
    • Ribitol (by reducing ribose)
    • Sorbitol (by reducing glucose)
    • Mannitol (by reducing mannose)
    • Xylitol (by reducing xylose)
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22
Q

Monosaccharides are bound by a…

A

Glycosydic bond

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23
Q

Composites of maltose

A

α-D-glu + α-D-glu

(α-1,4 glycosidic bond)

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24
Q

Composites of Cellobiose

A

β-D-glu + β-D-glu

(β-1,4 glycosidic bond)

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25
Composites of Lactose
β-D-gal + β-D-glu ## Footnote *(β-1,4 glycosidic bond)*
26
Composites of sucrose
α-D-glu + β-D-fru ## Footnote *(α-1, β-2 glycosidic bonds)*
27
Examples of oligosaccharides
Dextrines: * Amylo- * Malto- * Erithro- * Acro-
28
Sources of sucrose
* Sugar beet * Sugar cane * Sugar maple
29
Oligosaccharides used in...
* Milk constituents * Prebiotics - digested by the microbial flora * Glycolipids/glycoproteins of membranes
30
Starch and glycogen are examples of...
Homopolysaccharide
31
Composite of starch
* 20% amylose * 80% amylopectin
32
Describe the branching of starch
Branching occurs on the 25th glucose monomer
33
Glycogen
* Animal storage product * Branching * Non-water soluble * Branching at 8-10th glucose monomer
34
Glycosidic bonds between monomers are degraded by...
Amylase
35
Cellulose
* Non water soluble * Found in plant walls
36
Describe the bonding of cellulose
* Beta-D-glucose bound by beta 1,4 glycosidic bond * Hydrogen bonding
37
How is cellulose degraded by herbivores?
Presence of bacterial cellulase in the rumen
38
Examples of heteropolysaccharides
* Hyaluronic acid * Chondroitin sulphate * Heparin ## Footnote *Contain beta 1,3 glycosidic bond*
39
Hyaluronic acid composition
Repeating monomers: * D-glucuronate * *N*-acetyl-D-glucosamine
40
Hyaluronic acid is degraded by...
Hyaluronidase
41
Where is hyaluronidase found?
In the coat of the ovum
42
Chondroitin sulphate composition
Alternating units: * D-glucuronate * *N*-acetyl-D-galactosamine *Vitamin A has a role in the binding of the sulphate group*
43
Where is chondroitin sulphate found?
* Cartilage * Bone
44
Heparin composition
Repeating units: * D-glucuronate * D-glucosamine * Has an extended helical conformation* * Known as a clearing factor*
45
The carbohydrate portion of glycoproteins differs from that of glycosaminoglycans in that it is...
* Shorter * Often branched
46
Cori cycle
* Synthesis of glucose-6-phosphate *via* gluconeogenesis * Glucose-6-phosphate → Glucose
47
Anaerobic substrate for gluconeogenesis
Lactate
48
Glycogenesis (GG)
* Synthesis of glycogen from glucose * Liver, muscle cytoplasm
49
Glycogenolysis (GGL)
* Degradation of glycogen to blood glucose * Liver cytoplasm
50
Aim of carbohydrate metabolism in the liver
Elevation of blood glucose (not storage)
51
Which process is shown?
Glycogenesis
52
Compare hexokinase and glucokinase activity
* Hexokinase: * Non-hepatic * Low Km * High activity * Glucokinase: * Hepatic * High Km * Low activity
53
Which enzyme catalyses branching of the glycogen chain (glucogenesis)
Transglucosidase
54
The branched structure of glycogen allows...
Rapid release of glucose simultaneously from every non-reducing end of every branch
55
Glucose produced from glycogenolysis is transported by...
GLUT2 transporter *into the circulation*
56
Glycogenolysis occurs in the...
* Liver * (Kidney)
57
Energy balance of glycogenesis
Loss of 2 ATP per glucose stored ## Footnote *Glucose storage needs energy*
58
Energy balance of glycogenolysis
No energy gain/utilisation
59
Regulation of glycogenesis + glycogenolysis
* 2 reactions with opposite directions → Cascade mechanism * 2 types of regulation: * Slow, hormonal * Fast, allosteric
60
Process of cascade mechanism
1. Messenger molecules (hormones) induce → 2. Cellular answer by second messenger molecules ## Footnote *Intensity of cellular reaction can be 1000-10000 times higher*
61
Steps of hormonal regulation
1. Glucagon/adrenalin-binding receptors bind hormones → First messengers 2. Inactive GDP → active *with hormone binding* 3. GTP bound to α-subunit​ 4. Activated α-subunit​ dissociates 5. _Adenylate cyclase_ activated 6. GTP → GDP 7. α-subunit​ inactivated
62
Adenylate cyclase catalyses which reaction?
ATP → PPin + AMP → cAMP
63
Which enzyme degrades cAMP to form AMP?
Phosphodiesterase
64
cAMP-dependent protein kinase A (PKA) is activated by...
Glucagon
65
Give the effects of cAMP during hormonal regulation of glycogenolysis
1. cAMP activates PKA 2. Active PKA activates GPK 3. Active GPK activates GP beginning glycogenolysis
66
Describe the structure of PKA
* 2 catalytic subunits * 2 regulatory subunits
67
If the regulatory subunits are bound to the catalytic subunits, the PKA enzyme is...
Inactive
68
Enzyme for phosphorylation
Protein kinase
69
Enzyme for dephosphorylation
Phosphoprotein phosphatase
70
Give the steps of glycogenesis-glycogenolysis
1. Glycogen phosphorylase active by phosphorylation 2. Glycogen synthase active by dephosphorylation
71
Title the figure
Regulation by phosphorylation
72
Compound A * Name
Glycogen
73
Process 1 * Enzyme * Reactions
* Glycogen phosphorylase * Pi →
74
Compound B * Name
Glucose-1-phosphate
75
Process 2 * The fate of the compound
Enters into _glycogenolysis_
76
Process 3 * Reactions
UTP → PPi
77
Compound C * Name
UDP-glucose
78
Process 4 * Enzyme * Reactions
* Glycogen-synthase * → UDP
79
Enzyme A1 * Name
Glycogen phosphorylase ## Footnote *Active, phosphorylated form*
80
Process 5 * Enzyme
Phosphoprotein-phosphatase ## Footnote *Dephosphorylated*
81
Enzyme A2 * Name
Glycogen phosphorylase ## Footnote *Inactive, dephosphorylated*
82
Process 6 * Enzyme
Protein kinase ## Footnote *Phosphorylated*
83
Which hormone can regulate glycogenesis/glycogenolysis?
Insulin
84
Hormonal regulation of glycogenesis by insulin
1. Insulin receptor → PIP3 2. PIP3 activates PKB 3. Active PKB activates phosphodiesterase 4. This degrades + decreases cAMP 5. Dephosphorylation 6. Activation of glycogen synthase 7. Glycogenesis
85
Insulin: * Stimulation of glycogen synthesis * Inhibition of glycogen degradation
1. Insulin bound to the receptor 2. PI3-K activated 3. PIP2 → PIP3 *second messenger* 4. PKB inactive → PKB active 5. Phosphodiesterase inactive → Active 6. cAMP → AMP 7. PKA active → Inactive 8. Glycogen synthase → Active 9. Glycogen phosphorylase → Inactive
86
Give the steps of parallel regulation of glycogenolysis and glycogenesis in the liver + muscle
1. Glycogen phosphorylase active → Inactive 2. Phosphodiesterase activated by insulin 3. Glycogen synthase active → inactive 4. Adenylate cyclase activated by glucagon + adrenalin 5. *Step 1 repeats*
87
Allosteric regulation of glycogenolysis + glycogenesis is present in which organs?
Liver + muslce
88
The allosteric inhibitor of glycogen phosphorylase in the liver
Glucose
89
During allosteric regulation, 2 P groups of GP enzyme favour binding of...
Phosphoprotein phosphatase
90
Allosteric activator of glycogen phosphorylase in the _muscle_.
Ca2+ Binds to glycogen phosphorylase kinase
91
Carbohydrates * Glucose * Fructose * Galactose
92
Glucose-6-phosphate
93
Glucose ## Footnote *To blood and brain*
94
Glycogen ## Footnote *Stored in liver cells*
95
Pyruvic Acid
96
Glycolysis
97
Gluconeogenesis
98
Glycogenesis
99
Glycogenolysis
100
Lactic acid
101
Glycolysis
Degradation of glucose to pyruvate ## Footnote *or anaerobically to lactate*
102
Gluconeogenesis
Production of glucose from non-carbohydrate sources ## Footnote *in the liver*
103
Give the parts of glycolysis
1. Preparatory part 2. Energy conserving part
104
Energy production + end product of _anaerobic_ glycolysis
* 2 ATP (starting with glucose) * 3 ATP (starting with glycogen) * Product = Lactate
105
Energy production + end product of aerobic glycolysis
* 6 ATP (Starting with glucose) * 7 ATP (Starting with glycogen) * End product = Pyruvate
106
Role of lactate in meat quality
1. PSE (Pale, soft, exudative) (Pork) 2. DFD (Dark, firm, dry) (Beef)
107
Pasteur effect
Pyruvic acid → Lactic acid * Aerobic environment: No lactate production
108
Energy from gluconeogenesis is used in...
* Brain * Testes * Erythrocytes * Adrenal medulla
109
In ruminants, gluconeogenesis takes place...
Continuously
110
Lactic acid
111
Pyruvic acid
112
* Glycerol * Amino acids
113
6 ATP → 6 ADP
114
Glucose-6-phosphate
115
Glycogen
116
Glycogenesis
117
Glucose
118
Name the pathway
Gluconeogenesis
119
Give the energy gain of oxidation from one glucose molecule in glycolysis/citrate cycle
36 ATP
120
During glycogenesis, glycogen synthase acts as a...
Regulatory enzyme

Miller OnRamps Biology (8 decks)

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