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biochemistry > Carbohydrates > Flashcards

Carbohydrates Flashcards

1
Q

Most abundant organic molecules in nature

A

Carbohydrates

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2
Q

Functions of Carbohydrates

A

1) Energy source2) Storage form of energy3) Part of cell membranes4) Structural components

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3
Q

Classification of Carbohydrates

A

1) Monosaccharide - 1 sugar unit2) Disaccharide - 2 sugar unit3) Oligosaccharide - 3-10 sugar unit4) Polysaccharide - >10 sugar unit

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4
Q

Simplest carbohydrates; Cannot be hydrolyzed further

A

Monosaccharide

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5
Q

Condensation products of 2 monosaccharide units; Sugar units are linked by Glycosidic Bonds

A

Disaccharide

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6
Q

Glucose + Glucose

A

Maltose

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7
Q

Glucose + Galactose

A

Lactose

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8
Q

Glucose + Fructose

A

Sucrose

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9
Q

Condensation products of 3-10 monosaccharides; Most are not digested by human enzymes

A

Oligosaccharide

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10
Q

Condensation product of >10 monosaccharide units; May be linear or branched polymers

A

Polysaccharide

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11
Q

Homopolymer of glucose forming an alpha-glucosidic chain, called a Glucosan or Glucan; Most important dietary source of Carbohydrate in cereals, potatoes, legumes and other vegetables

A

Starch

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12
Q

Storage polysaccharide in animals; More highly branched structure than amylopectin with chains of 12-14 alpha-D-glucopyranose residues with branching by means of alpha1-6 glucosidic bonds

A

Glycogen

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13
Q

Polysaccharide of Fructose used to determine the glomerular filtration rate

A

Inulin

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14
Q

Chief constituent of plant cell walls; Insoluble and consists of beta-D-glucopyranose units linked beta1-4 bonds to form long, straight chains strengthened by cross-linking hydrogen bonds; cannot be digested by mammals

A

Cellulose

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15
Q

Structural polysaccharide in the exoskeleton of crustaceans and insects

A

Chitin

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16
Q

Complex carbohydrates containing amino sugars and uronic acids; They may be attached to a protein molecule to form a proteoglycan

A

Glycosaminoglycans or Mucopolysaccharides

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17
Q

Proteins containing branched or unbranched oligosaccharide chains; Occur in cell membranes and many other situations

A

Glycoproteins or Mucoproteins

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18
Q

Compounds that have the same chemical formula but different structures

A

Isomers

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19
Q

Compounds that differ in configuration around only one specific carbon atom, with the exception of the carbonyl carbon

A

Epimers

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20
Q

Pairs of structures that are mirror images of each other

A

Enantiomers

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21
Q

Sugars are convertible between a linear form and a ring form; Most are in the cyclic or ring form

A

Anomers

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22
Q

Can spontaneously interconvert through a process called

A

Mutarotation

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23
Q

Principal sites of Carbohydrate Digestion

A

MouthIntestinal lumen

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24
Q

Physical Digestion; Carbohydrate digestion begins during

A

Mastication

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25
Q

Chemical digestion of Carbohydrates in mouth

A

Salivary amylase

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26
Q

Amylase can only digest ?

A

Alpha1-4 glycosidic bonds

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27
Q

Hydrolyzes complex carbohydrates to disaccharides and trisaccharides, but not directly to monosaccharides

A

Pancreatic amylase

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28
Q

Disaccharides in the _______ complete the digestive process

A

Brush border

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29
Q

Facilitated diffusion; For all sugars

A

GLUT-1 Transporter

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30
Q

Facilitated diffusion; For glucose, galactose, and fructose

A

GLUT-5 Transporter

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31
Q

Secondary active transport; Na/hexose symporter; For glucose and galactose

A

SGLT-1 Transporter

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32
Q

Absorption of sugar requires passage through two membranes:

A

1) Between lumen and enterocyte2) Between enterocyte and capillary

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33
Q

Increase in blood glucose after a test dose of a carbohydrate compared with that after an equivalent amount of glucose; Tells how fast a carbohydrate is absorbed references are glucose and galactose

A

Glycemic Index

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34
Q

Glycemic Index >1

A

Fast absorption

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35
Q

Glycemic Index

A

Slow absorption

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36
Q

Glycemic Index = 1

A

Normal absorption

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37
Q

Sum of ALL the chemical reactions in a cell, tissue, or the whole body; Can either be catabolic or anabolic

A

Metabolism

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38
Q

Synthesis of compounds from smaller raw materials; Endergonic and divergent process

A

Anabolic

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39
Q

Breakdown of larger molecules; Usually oxidative reactions; Exergonic and convergent process

A

Catabolic

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40
Q

Crossroads of metabolism, the link between anabolic and catabolic pathways

A

Amphibolic

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41
Q

Regulators of Metabolism: Signals from within the cell

A

Substrate availability Product inhibitionAllosteric activators/inhibitors

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42
Q

Regulators of Metabolism: Communication between cells

A

Direct contactSynaptic signalingEndocrine signalingGap junctionsNeurotransmittersHormones

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43
Q

Regulators of Metabolism: Second messenger systems

A

Calcium/inositol triphosphate (ITP)Adenylyl cyclase system (cAMP)Guanylate cyclase system (cGMP)

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44
Q

Inositol Triphosphate System: G protein used

A

Gq

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45
Q

Inositol Triphosphate System: Substrate used

A

Phosphatidylinositol - found in the cell membrane acted on by phospholipase C

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46
Q

Inositol Triphosphate System: 2nd Messengers

A

Diacyl glycerol (DAG) - activate protein kinase CInositol triphosphate (ITP) - release intracellular Ca

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47
Q

Membrane-bound enzyme that converts ATP to cyclic AMP or cAMP; cAMP hydrolyzed to 5’-AMP by cAMP phosphodiesterase

A

Adenylyl Cyclase System

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48
Q

Adenylyl Cyclase System: G protein used

A

Gs - Stimulates adenylate cyclase, increase cAMPGi - Inhibits adenylate cyclase, decrease cAMP

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49
Q

Adenylyl Cyclase System: Substrate used

A

ATP

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50
Q

Adenylyl Cyclase System: 2nd Messengers

A

cAMP - activate protein kinase A

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51
Q

GLUT Transporter: GLUT - 1

A

Found in: erythrocytes, brain, kidney, colon, placentaFunction: uptake of Glucose

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52
Q

GLUT Transporter: GLUT - 2

A

Found in: liver, pancreatic B cell, small intestine, kidneyFunction: rapid uptake and release of Glucose

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53
Q

GLUT Transporter: GLUT - 3

A

Found in: brain, kidney, placentaFunction: uptake of Glucose

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54
Q

GLUT Transporter: GLUT - 4

A

Found in: heart, skeletal muscle, adipose tissueFunction: insulin-stimulated uptake of Glucose

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55
Q

GLUT Transporter: GLUT - 5

A

Found in: small intestineFunction: absorption of Glucose

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56
Q

Glycolysis: What is it for?

A

Major pathway for Glucose Metabolism that converts glucose into 3 carbon compounds to provide energy

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57
Q

Glycolysis: Where does it occur?

A

In the cytoplasm, in ALL cells

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58
Q

Glycolysis: Substrate

A

Glucose

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59
Q

Glycolysis: End-product

A

Pyruvate or lactate, depending on the presence of mitochondria and availability of oxygen

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60
Q

Glycolysis: Rate limiting Step

A

Reaction: fructose-6-phosphate ➡️ fructose 1,6-biphosphateEnzyme: phosphofructokimase (PFK-1)

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61
Q

Cells with mitochondria; Cells with adequate O2 supply; End product: Pyruvate

A

Aerobic Glycolysis

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62
Q

Cells without mitochondria; Cells without sufficient O2; End product: Lactate

A

Anaerobic Glycolysis

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63
Q

ATP used up to produce phosphorylated intermediates

A

Energy Investment

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64
Q

ATP produced through substrate-level phosphorylation

A

Energy Generation

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65
Q

Irreversible and Regulated steps in Glycolysis

A

Step 1: Phosphorylation of GlucoseStep 3: Phosphorylation of Fructose-6-phosphateStep 10: Formation of Pyruvate

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66
Q

Glycolysis: Step 1

A

Glucose➡️Glucose-6-phosphateEnzyme: Hexokinase or Glucokinase

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67
Q

Has a high affinity (low Km) for glucose, and in the liver it is saturated under normal conditions, so acts at a constant rate to provide glucose-6-phosphate to meet the cell’s need

A

Hexokinase

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68
Q

Has a Km very much higher than the normal intracellular concentration of glucose; Removes glucose from the blood following a meal, providing glucose 6-phosphate in excess of requirements for glycolysis, which is used for glycogen synthesis and lipogenesis

A

Glucokinase

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69
Q

Glycolysis: Step 3 - Rate limiting step of Glycolysis

A

Fructose-6-phosphate➡️Fructose-1,6-biphosphateEnzyme: Phosphofructokinase-1

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70
Q

Converts fructose-6-phosphate to fructose-1,6-biphosphate; Activator: fructose-2,6-biphosphate and AMP; Inhibitor: ATP and Citrate

A

Phosphofructokinase-1 (PFK-1)

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71
Q

Converts fructose-6-phosphate to fructose-2,6-biphosphate; Activator: well fed state - increase insulin, decrease glucagon Inhibitor: starved state - decrease insulin, increase glucagon

A

Phosphofructokinase-2 (PFK-2)

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72
Q

Glycolysis: Step 10 - Substrate level phosphorylation that yields 1 ATP per molecule of phosphoenolpyruvate

A

Phosphoenolpyruvate (PEP)➡️PyruvateEnzyme: pyruvate kinase

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73
Q

Activator of pyruvate kinase

A

Fructose-1,6-biphosphate (feedforward mechanism)

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74
Q

Inhibitor of pyruvate kinase

A

Increase glucagon + Increase cAMP➡️phosphorylation

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75
Q

ATP Production in Glycolysis

A

1) 1,3-biphosphoglycerate➡️3-phosphoglycerateEnzyme: phosphoglycerate kinase2) phosphoenolpyruvate➡️pyruvateEnzyme: pyruvate kinase

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76
Q

How many net molecules of ATP can be produced from 1 glucose molecule via substrate-level phosphorylation?

A

2 ATP molecules

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77
Q

Production of NADH

A

Step 1: glyceraldehyde-3-phosphate➡️1,3-biphosphoglycerateEnzyme: glyceraldehyde-3-phosphate dehydrogenase

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78
Q

What happens to pyruvate?

A

1) pyruvate enters the citric acid cycle (aerobic glycolysis)2) pyruvate reduced to lactate (anaerobic)

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79
Q

In Aerobic Glycolysis: NADH

A

Proceeds to Electron Transport Chain

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80
Q

NADH CANNOT pass through mitochondrial membrane and so needs shuttles

A

1) Malate-Aspartate Shuttle2) Glycerol Phosphate Shuttle

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81
Q

In liver, kidney and heart1 NADH = 3 ATP

A

Malate-Aspartate Shuttle

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82
Q

In skeletal muscle and brain1 NADH = 2 ATP

A

Glycerol Phosphate Shuttle

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83
Q

In what part of the cell can you find the electron transport chain?

A

Inner mitochondrial membrane

84
Q

In Anaerobic Glycolysis, NADH used to

A

Reduce pyruvate to lactate

85
Q

Strictly Glycolytic Organs

A

RBCsLensCornea of eyeKidney medullaTestesWBCs

86
Q

ATP yield of Glycolysis

A

Anaerobic: 2 ATP Aerobic: 6 (or 8) ATP

87
Q

Found in RBCs where phosphoglycerate kinase is bypassed; Reduces hemoglobin affinity for O2

A

2,3-Bisphosphoglycerate

88
Q

Inhibits pyruvate dehydrogenase by binding to lipoic acid; Competes with inorganic phosphate as a substrate for glyceraldehyde-3-phosphate dehydrogenase

A

Arsenic poisoning (Pentavalent Arsenic)

89
Q

Most common enzyme defect in glycolysis; Manifests as chronic hemolytic anemia

A

Pyruvate Kinase Deficiency

90
Q

Low exercise capacity, particularly on high carbohydrate diets

A

Muscle Phosphofructokinase Deficiency

91
Q

Pyruvate kinase deficiency and G6PD deficiency both present with intravascular hemolytic anemia. Important differences are:

A

1) G6PD has HEINZ BODIES in the peripheral smear2) G6PD often has a precipitating history of oxidative stress

92
Q

Alternate Fates of Pyruvate

A

Pyruvate➡️Acetyl CoAEnzyme: Pyruvate dehydrogenase complex

93
Q

Co-enzymes of Pyruvate dehydrogenase complex

A

1) Lipoic Acid2) NAD3) FAD4) Thiamine pyrophosphate5) Coenzyme A

94
Q

Pyruvate➡️Acetyl CoASubstrate?Product?Activator?Inhibitor?

A

Substrate: PyruvateProduct: Acetyl CoA, NADH, and CO2Activator: NAD+, CoA and pyruvateInhibitor: NADH, acetyl CoA, ATP

95
Q

Most common biochemical cause of congenital lactic acidosis; X-linked dominant condition; Increase lactate + Decreased acetyl CoA leads to deprivation of Acetyl CoA in the brain causing psychomotor retardation and death

A

Pyruvate Dehydrogenase Deficiency

96
Q

Treatment of Pyruvate Dehydrogenase Deficiency

A

Ketogenic Diet

97
Q

Alcohol + Nutritional deprivation = Thiamine DeficiencyAn acquired pyruvate dehydrogenase deficiency➡️fatal pyruvic and lactic acidosis

A

Chronic Alcoholism

98
Q

Final common pathway for aerobic oxidation of ALL nutrients; Provides majority of ATP for energy

A

Tricarboxylic Acid Pathway (TCA) aka Kreb’s Cycle or Citric Acid Cycle

99
Q

TCA: Where does it occur?

A

In ALL cells with mitochondria

100
Q

TCA: What is the substrate?

A

Acetyl Coa

101
Q

TCA: What are the products?

A

CO2, GTP, NADH and FADH2

102
Q

TCA: Rate limiting step

A

Reaction: isocitrate➡️alpha-ketoglutarateEnzyme: isocitrate dehydrogenase

103
Q

MNEMONIC: Officer Can I Keep Selling Sex For Money

A

OxaloacetateCitrateIsocitrateKetoglutarateSuccinyl CoASuccinateFumateMalate

104
Q

Acetyl CoA + Oxaloacetate ➡️Citrate

A

Enzyme: Citrate synthase

105
Q

Citrate➡️Isocitrate (isomerization)

A

Enzyme: AconitaseInhibitor: Fluoroacetate (rat poison)

106
Q

Isocitrate➡️alpha-ketoglutarate

A

Rate limiting stepEnzyme: Isocitrate dehydrogenaseProducts: CO2 and NADH

107
Q

Alpha-ketoglutarate➡️Succinyl-CoA

A

Enzyme: alpha-ketoglutarate dehydrogenaseCo-enzyme: similar to pyruvate dehydrogenaseProducts: CO2 and NADHInhibitor: arsenite

108
Q

Succinyl-CoA➡️Succinate

A

Enzyme: succinate thiokinaseProducts: GTP by substrate level phosphorylation

109
Q

Succinate➡️fumarate

A

Enzyme: succinate dehydrogenaseProducts: FADH2

110
Q

Fumarate➡️Malate

A

Enzyme: Fumarase (Fumarate hydratase)

111
Q

Malate➡️Oxaloacetate

A

Enzyme: Malate dehydrogenaseProducts: NADH

112
Q

TCA Intermediates: Delivers acetyl CoA to the cytoplasm for fatty acid synthesis via citrate shuttle

A

Citrate

113
Q

TCA Intermediates: Heme synthesis and activation of ketone bodies in extrahepatic tissues

A

Succinyl CoA

114
Q

TCA Intermediates: May be used for gluconeogenesis

A

Malate

115
Q

ATP yield for TCA

A

Acetyl CoA: 12 ATPPyruvate: 15 ATP (extra 3 ATP - from NADH)

116
Q

Production of New glucose

A

Gluconeogenesis

117
Q

Gluconeogenesis from the following intermediates:

A

1) intermediates of glycolysis and the TCA2) glycerol from triacylglycerols3) lactate through the Cori Cycle4) carbon skeletons (alpha-ketoacids) of glucogenic amino acids

118
Q

Gluconeogenesis: Where does it occur?

A

Liver 90%Kidney 10%Prolonged fasting: Kidney 40%(In both mitochondria and cytoplasm)

119
Q

Gluconeogenesis: Substrate

A

Pyruvate

120
Q

Gluconeogenesis: Product

A

Glucose

121
Q

Gluconeogenesis: Rate limiting step

A

Reaction: Fructose-1,6-biphosphate➡️Fructose-6-phosphateEnzyme: Fructose-1,6-biphosphataseActivator: ATPInhibitor: Fructose-2,6-biphosphate and AMP

122
Q

Conversion of lactate to glucose

A

Cori Cycle

123
Q

Cori Cycle: Energy Expense

A

4 ATP molecules

124
Q

True or False: Muscle cannot reconvert lactate to glucose. Lactate must first be transported to the liver for gluconeogenesis.

A

True

125
Q

Important steps in Gluconeogenesis

A

Step 10: Pyruvate➡️OAA➡️PEPStep 3: Fructose-1,6-biphosphate➡️Fructose-6-phosphateStep 1: Glucose-6-phosphate➡️Glucose

126
Q

Requires biotin and ATP; Allosterically activated by Acetyl CoA

A

Pyruvate carboxylase

127
Q

Requires GTP

A

PEP Carboxykinase

128
Q

ALL Carboxylases require ____ as a Co-factor

A

Biotin

129
Q

Promotes Glycolysis and Inhibits Gluconeogenesis

A

Fructose-2,6-biphosphateActivates: Phosphofructokinase-1➡️favors GlycolysisInhibits: Fructose-1,6-biphosphatase➡️inhibits Gluconeogenesis

130
Q

Final step of Gluconeogenesis which is shared with Glycogen degradation

A

Glucose-6-phosphate➡️Glucose

131
Q

End goal of Glucose-6-phosphate➡️Glucose

A

Releases free Glucose into the circulation

132
Q

Enzyme of Glucose-6-phosphate➡️Glucose

A

Glucose-6-phosphatase

133
Q

Glucose-6-phosphate➡️Glucose: Where does it occur?

A

Liver and Kidneys only

134
Q

Regulation of Gluconeogenesis

A

1) Circulating levels of Glucagon2) Availability of Glucogenic substrates3) Allosteric activation by Acetyl CoA4) Allosteric inhibition by AMP

135
Q

Energy expenditure of Gluconeogenesis

A

Use of 4 ATPsUse of 2 GTPsOxidizes 2 NADH back to NAD+

136
Q

In hyperglycemia, the glomerular filtrate may contain more glucose than can be reabsorbed; Occurs when the venous blood glucose concentration exceeds 9.5-10.0mmol/L (renal threshold)

A

Glucosuria

137
Q

Alcoholism: High amounts of cytoplasmic NADH is formed by:

A

Alcohol dehydrogenaseAcetaldehyde dehydrogenase

138
Q

Hypoglycemia: High amounts of NADH favors the ff reactions:

A

Pyruvate➡️LactateOAA➡️MalateDHAP➡️Glycerol-3-phosphate

139
Q

High fetal glucose consumption; Risk of maternal and fetal hypoglycemia especially during fasting

A

Hypoglycemia during Pregnancy

140
Q

Due to increase estrogen; Fasting Hypoglycemia

A

Hyperinsulinemia

141
Q

Due to increase HPL; Post-prandial hyperglycemia

A

Insulin resistance

142
Q

Premature and LBW babies have little adipose tissue; Enzymes of Gluconeogenesis are not yet completely functional

A

Hypoglycemia in the Neonate

143
Q

Major storage carbohydrate in animals; Branched polymer of alpha-D-glucose

A

Glycogen

144
Q

Glycogen: Where’s it stored?

A

Liver and Muscle onlyLiver: 100g = 6% of liverMuscle: 400g =

145
Q

Synthesis of new glycogen molecules from alpha-D-glucose

A

Glycogenesis

146
Q

Glycogenesis: Where does it occur?

A

Liver Muscle(Occurs in cytosol)

147
Q

Glycogenesis: Substrates

A

UDP-glucoseATP and UTPGlycogenin - a core, primer protein

148
Q

Glycogenesis: Product

A

Glycogen

149
Q

Glycogenesis: Rate limiting step

A

Reaction: Elongation of glycogenEnzyme: Glycogen synthase

150
Q

Important Steps in Glycogenesis

A

Glucose-6-phosphate➡️Glucose-1-phosphateSynthesis of UDP-GlucoseElongation of Glycogen chainsFormation of branches in glycogen

151
Q

Enzyme of Glucose-6-phosphate➡️Glucose-1-phosphate

A

Enzyme: Phosphoglucomutase(Reversible - Not a rate limiting step)

152
Q

Synthesis of UDP-Glucose: Activated form

A

Glucose

153
Q

Synthesis of UDP-Glucose: Enzyme

A

UDP-glucose phosphorylase

154
Q

Synthesis of UDP-Glucose: Substrates

A

Glucose-1-phosphateUTP

155
Q

Rate limiting step of Glycogenesis

A

Elongation of Glycogen chainsEnzyme: Glycogen synthase

156
Q

Formation of branches in glycogen: Enzyme

A

Branching enzyme composed of amylo alpha(1-4)➡️alpha(1-6) transglucosidase

157
Q

Shortening of glycogen chains to produce molecules of a-D-glucose

A

Glycogenolysis

158
Q

Glycogenolysis: Where does it occur?

A

Liver Muscle(In the cytosol)

159
Q

Glycogenolysis: Substrate

A

Glycogen

160
Q

Leaves about 4 glucose residues before a branch point

A

Limit dextrin

161
Q

Glycogenolysis: Products

A

Glucose-1-phosphateFree glucose - produced during the debranching processLiver: can release free glucose to circulationMuscle: limited to glucose-6-phosphate within muscle only

162
Q

Glycogenolysis: Rate limiting step

A

Reaction: Removal of glucose Enzyme: glycogen phosphorylase

163
Q

Glycogenolysis: Removal of branches

A

Enzyme: debranching enzymeBonds cleave: alpha(1-4) and alpha(1-6)Products: Free Glucose

164
Q

Conversion of Glucose-1-phosphate to Glucose-6-phosphate

A

Enzyme: phosphoglucomutaseLiver: Glucose-6-phosphate further converted to glucoseMuscle: Glucose-6-phosphate is the final product

165
Q

Lysosomal degradation of Glycogen

A

Enzyme: alpha(1-4) glucosidase aka Acid maltase - an enzyme that is different from glycogen phosphorylase

166
Q

Glycogen Storage Disease: Type I

A

Von Gierke’sGlucose-6-phosphatase deficiencyHypoglycemia + Lactic Acidosis/Ketosis

167
Q

Glycogen Storage Disease: Type II

A

Pompe’sAcid maltase deficiencyCardiomegaly and heart failure

168
Q

Glycogen Storage Disease: Type III

A

Cori’sDebranching enzyme deficiencyMilder form of Type I

169
Q

Glycogen Storage Disease: Type IV

A

Andersen’sBranching enzyme deficiencySevere form of Type I (early death from heart and liver failure)

170
Q

Glycogen Storage Disease: Type V

A

McArdle’sSkeletal Muscle glycogen phosphorylase deficiencyGlycogen in muscle: Muscle cramps + myoglobinuria but NO lactic acidosis

171
Q

Glycogen Storage Disease: Type VI

A

Hers’Hepatic Glycogen phosphorylase deficiencyGlycogen in liver cells: hypoglycemia

172
Q

Glycogen Storage Disease: Type VII

A

Tarui’sPFK deficiencyLike Type V + hemolytic anemia

173
Q

Glycogen Storage Disease: Type VIII

A

Hepatic phosphylase kinase deficiencyLike Type VI

174
Q

Important source of Galactose

A

Disaccharide lactose in milk

175
Q

Phosphorylation of galactose

A

Galactose➡️Galactose-1-phosphateEnzyme: Galactokinase or Hexokinase

176
Q

Formation of UDP-galactose

A

Galactose-1-phosphate + UDP-glucose➡️UDP-galactose + glucose-1-phosphateEnzyme: galactose -1-phosphate uridyl transferase

177
Q

Use of galactose as carbon source

A

UDP-galactose➡️UDP-glucoseEnzyme: UDP-hexose-4-epimerase

178
Q

Causes Galactosemia and Galactosuria

A

Galactokinase Deficiency

179
Q

Absence of galactose-1-phosphate uridyltransferase; Autosomal recessive; Galactitol accumulation - causes Cataracts + Hepatosplenomegaly + mental retardation; Absolute contraindication to breastfeeding

A

Classic Galactosemia

180
Q

Galactosemia, Galactosuria, cataracts within a few days of birth, vomiting and diarrhea after milk ingestion, hypoglycemia, liver disease and cirrhosis, lethargy and hypotonia, mental retardation; eliminate sources of galactose from the diet

A

Gal-1-Phosphate Uridyltransferase Deficiency

181
Q

Important source of fructose

A

Disaccharide sucrose found in honey and fruits

182
Q

Phosphorylation of fructose

A

Fructose➡️Fructose-1-phosphateEnzyme: Fructokinase or hexokinase

183
Q

Formation of DHAP an Glyceraldehyde

A

Fructose-1- phosphate➡️dihydroxyacetone phosphate (DHAP) + GlyceraldehydeEnzyme: Aldolase B

184
Q

For Glycolysis; Fructose-1,6-biphosphate➡️DHAP+glycerol-3-phosphate

A

Aldolase A

185
Q

For Fructose metabolism; Fructose-1-phosphate➡️DHAP+glyceraldehyde

A

Aldolase B

186
Q

Defect in Fructokinase; Benign and asymptomatic whose only symptom is the appearance of fructose in blood and urine

A

Essential Fructosuria

187
Q

Deficiency of Aldolase B; Autosomal recessive; Fructose-1-phosphate accumulates leading to decrease phosphate, decrease glycogenolysis, decrease gluconeogenesis; hypoglycemia, jaindice, cirrhosis, vomiting

A

Fructose Intolerance

188
Q

Important component of Glycoprotein

A

Mannose Metabolism

189
Q

Isomerization between mannose and fructose

A

Mannose-6-phosphate➡️fructose-6-phosphateEnzyme: phosphomannose isomerase

190
Q

Glucose➡️Sorbitol

A

Enzyme: Aldose reductaseFound in lens, retina, Schwann cells, liver, kidney, placenta, RBC, ovaries, seminal vesicles

191
Q

Sorbitol➡️Fructose

A

Enzyme: Sorbitol dehydrogenaseFound in the seminal vesicles only since Fructose is the fuel of sperm

192
Q

Pentose Phosphate Pathway: What is it for?

A

1) Produces NADPHFA and Steroid biosynthesisReduction of GlutathioneCytochrome p450WBC respiratory burstNitric oxide synthesis2) Produces Ribose-5-phosphate for nucleotide synthesis3) Metabolic use of 5-carbon sugars

193
Q

Pentose Phosphate Pathway: Where does it occur?

A

In the cytoplasmActive in: Liver, Adipose tissue, Adrenals, Thyroid, Testes, RBC, Lactating membranesLow in: skeletal muscle, non-lactating mammaries

194
Q

Pentose Phosphate Pathway: Substrate

A

Glucose-6-phosphate(No consumption or production of ATP)

195
Q

Pentose Phosphate Pathway: Products

A

Ribose-5-phosphateFructose-6-phosphateGlyceraldehyde-3-phosphateNADPH

196
Q

Pentose Phosphate Pathway: Rate limiting step

A

Reaction: glucose-6-phosphate➡️6-phosphogluconateEnzyme: glucose-6-phosphate dehydrogenase

197
Q

Pentose Phosphate Pathway: Phase 1

A

OxidativeIrreversibleEnzyme: glucose-6-phosphate dehydrogenaseProduct: NADPH ribulose-5-phosphate

198
Q

Pentose Phosphate Pathway: Phase 2

A

Non-oxidativeReversibleEnzyme: Transketolase (requires Thiamine)Product: ribose-5-phosphate, glyceraldehyde-3-phosphate, fructose-6-phosphate

199
Q

Removes H2O2 in reaction catalyzed by glutathione peroxidase; very important in RBCs

A

Glutathione

200
Q

Reduced glutathione sequester harmful H2O2

A

Enzyme: glutathione peroxidase

201
Q

Reduced glutathione recreated using NADPH

A

Enzyme: glutathione reductase

202
Q

Most common disease producing enzyme abnormality in humans; Involves decrease NADPH in RBCs and decrease activity of glutathione reductase causing free radicals and peroxides to accumulate

A

Glucose-6-phosphate Dehydrogenase Deficiency

203
Q

Precipitating factors of Glucose-6-phosphate Dehydrogenase Deficiency

A

Infection - most commonDrugs - antibiotics (sulfonamides, chloramphenicol), antimalarials (primaquine), antipyretics (except ASA and paracetamol)Fava beans

204
Q

Altered RBCs due to phagocytic removal of Heinz bodies in spleen

A

Bite cells in Heinz Bodies

205
Q

Deficiency in NADPH oxidase; severe, persistent and chronic pyogenic infections

A

Chronic Granulomatous Disease

biochemistry (7 decks)

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