Carbohydrates Flashcards
(205 cards)
1
Q
Most abundant organic molecules in nature
A
Carbohydrates
2
Q
Functions of Carbohydrates
A
1) Energy source2) Storage form of energy3) Part of cell membranes4) Structural components
3
Q
Classification of Carbohydrates
A
1) Monosaccharide - 1 sugar unit2) Disaccharide - 2 sugar unit3) Oligosaccharide - 3-10 sugar unit4) Polysaccharide - >10 sugar unit
4
Q
Simplest carbohydrates; Cannot be hydrolyzed further
A
Monosaccharide
5
Q
Condensation products of 2 monosaccharide units; Sugar units are linked by Glycosidic Bonds
A
Disaccharide
6
Q
Glucose + Glucose
A
Maltose
7
Q
Glucose + Galactose
A
Lactose
8
Q
Glucose + Fructose
A
Sucrose
9
Q
Condensation products of 3-10 monosaccharides; Most are not digested by human enzymes
A
Oligosaccharide
10
Q
Condensation product of >10 monosaccharide units; May be linear or branched polymers
A
Polysaccharide
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
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
13
Q
Polysaccharide of Fructose used to determine the glomerular filtration rate
A
Inulin
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
15
Q
Structural polysaccharide in the exoskeleton of crustaceans and insects
A
Chitin
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
17
Q
Proteins containing branched or unbranched oligosaccharide chains; Occur in cell membranes and many other situations
A
Glycoproteins or Mucoproteins
18
Q
Compounds that have the same chemical formula but different structures
A
Isomers
19
Q
Compounds that differ in configuration around only one specific carbon atom, with the exception of the carbonyl carbon
A
Epimers
20
Q
Pairs of structures that are mirror images of each other
A
Enantiomers
21
Q
Sugars are convertible between a linear form and a ring form; Most are in the cyclic or ring form
A
Anomers
22
Q
Can spontaneously interconvert through a process called
A
Mutarotation
23
Q
Principal sites of Carbohydrate Digestion
A
MouthIntestinal lumen
24
Q
Physical Digestion; Carbohydrate digestion begins during
A
Mastication
25
Chemical digestion of Carbohydrates in mouth
Salivary amylase
26
Amylase can only digest ?
Alpha1-4 glycosidic bonds
27
Hydrolyzes complex carbohydrates to disaccharides and trisaccharides, but not directly to monosaccharides
Pancreatic amylase
28
Disaccharides in the _______ complete the digestive process
Brush border
29
Facilitated diffusion; For all sugars
GLUT-1 Transporter
30
Facilitated diffusion; For glucose, galactose, and fructose
GLUT-5 Transporter
31
Secondary active transport; Na/hexose symporter; For glucose and galactose
SGLT-1 Transporter
32
Absorption of sugar requires passage through two membranes:
1) Between lumen and enterocyte2) Between enterocyte and capillary
33
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
Glycemic Index
34
Glycemic Index >1
Fast absorption
35
Glycemic Index
Slow absorption
36
Glycemic Index = 1
Normal absorption
37
Sum of ALL the chemical reactions in a cell, tissue, or the whole body; Can either be catabolic or anabolic
Metabolism
38
Synthesis of compounds from smaller raw materials; Endergonic and divergent process
Anabolic
39
Breakdown of larger molecules; Usually oxidative reactions; Exergonic and convergent process
Catabolic
40
Crossroads of metabolism, the link between anabolic and catabolic pathways
Amphibolic
41
Regulators of Metabolism: Signals from within the cell
Substrate availability Product inhibitionAllosteric activators/inhibitors
42
Regulators of Metabolism: Communication between cells
Direct contactSynaptic signalingEndocrine signalingGap junctionsNeurotransmittersHormones
43
Regulators of Metabolism: Second messenger systems
Calcium/inositol triphosphate (ITP)Adenylyl cyclase system (cAMP)Guanylate cyclase system (cGMP)
44
Inositol Triphosphate System: G protein used
Gq
45
Inositol Triphosphate System: Substrate used
Phosphatidylinositol - found in the cell membrane acted on by phospholipase C
46
Inositol Triphosphate System: 2nd Messengers
Diacyl glycerol (DAG) - activate protein kinase CInositol triphosphate (ITP) - release intracellular Ca
47
Membrane-bound enzyme that converts ATP to cyclic AMP or cAMP; cAMP hydrolyzed to 5'-AMP by cAMP phosphodiesterase
Adenylyl Cyclase System
48
Adenylyl Cyclase System: G protein used
Gs - Stimulates adenylate cyclase, increase cAMPGi - Inhibits adenylate cyclase, decrease cAMP
49
Adenylyl Cyclase System: Substrate used
ATP
50
Adenylyl Cyclase System: 2nd Messengers
cAMP - activate protein kinase A
51
GLUT Transporter: GLUT - 1
Found in: erythrocytes, brain, kidney, colon, placentaFunction: uptake of Glucose
52
GLUT Transporter: GLUT - 2
Found in: liver, pancreatic B cell, small intestine, kidneyFunction: rapid uptake and release of Glucose
53
GLUT Transporter: GLUT - 3
Found in: brain, kidney, placentaFunction: uptake of Glucose
54
GLUT Transporter: GLUT - 4
Found in: heart, skeletal muscle, adipose tissueFunction: insulin-stimulated uptake of Glucose
55
GLUT Transporter: GLUT - 5
Found in: small intestineFunction: absorption of Glucose
56
Glycolysis: What is it for?
Major pathway for Glucose Metabolism that converts glucose into 3 carbon compounds to provide energy
57
Glycolysis: Where does it occur?
In the cytoplasm, in ALL cells
58
Glycolysis: Substrate
Glucose
59
Glycolysis: End-product
Pyruvate or lactate, depending on the presence of mitochondria and availability of oxygen
60
Glycolysis: Rate limiting Step
Reaction: fructose-6-phosphate ➡️ fructose 1,6-biphosphateEnzyme: phosphofructokimase (PFK-1)
61
Cells with mitochondria; Cells with adequate O2 supply; End product: Pyruvate
Aerobic Glycolysis
62
Cells without mitochondria; Cells without sufficient O2; End product: Lactate
Anaerobic Glycolysis
63
ATP used up to produce phosphorylated intermediates
Energy Investment
64
ATP produced through substrate-level phosphorylation
Energy Generation
65
Irreversible and Regulated steps in Glycolysis
Step 1: Phosphorylation of GlucoseStep 3: Phosphorylation of Fructose-6-phosphateStep 10: Formation of Pyruvate
66
Glycolysis: Step 1
Glucose➡️Glucose-6-phosphateEnzyme: Hexokinase or Glucokinase
67
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
Hexokinase
68
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
Glucokinase
69
Glycolysis: Step 3 - Rate limiting step of Glycolysis
Fructose-6-phosphate➡️Fructose-1,6-biphosphateEnzyme: Phosphofructokinase-1
70
Converts fructose-6-phosphate to fructose-1,6-biphosphate; Activator: fructose-2,6-biphosphate and AMP; Inhibitor: ATP and Citrate
Phosphofructokinase-1 (PFK-1)
71
Converts fructose-6-phosphate to fructose-2,6-biphosphate; Activator: well fed state - increase insulin, decrease glucagon Inhibitor: starved state - decrease insulin, increase glucagon
Phosphofructokinase-2 (PFK-2)
72
Glycolysis: Step 10 - Substrate level phosphorylation that yields 1 ATP per molecule of phosphoenolpyruvate
Phosphoenolpyruvate (PEP)➡️PyruvateEnzyme: pyruvate kinase
73
Activator of pyruvate kinase
Fructose-1,6-biphosphate (feedforward mechanism)
74
Inhibitor of pyruvate kinase
Increase glucagon + Increase cAMP➡️phosphorylation
75
ATP Production in Glycolysis
1) 1,3-biphosphoglycerate➡️3-phosphoglycerateEnzyme: phosphoglycerate kinase2) phosphoenolpyruvate➡️pyruvateEnzyme: pyruvate kinase
76
How many net molecules of ATP can be produced from 1 glucose molecule via substrate-level phosphorylation?
2 ATP molecules
77
Production of NADH
Step 1: glyceraldehyde-3-phosphate➡️1,3-biphosphoglycerateEnzyme: glyceraldehyde-3-phosphate dehydrogenase
78
What happens to pyruvate?
1) pyruvate enters the citric acid cycle (aerobic glycolysis)2) pyruvate reduced to lactate (anaerobic)
79
In Aerobic Glycolysis: NADH
Proceeds to Electron Transport Chain
80
NADH CANNOT pass through mitochondrial membrane and so needs shuttles
1) Malate-Aspartate Shuttle2) Glycerol Phosphate Shuttle
81
In liver, kidney and heart1 NADH = 3 ATP
Malate-Aspartate Shuttle
82
In skeletal muscle and brain1 NADH = 2 ATP
Glycerol Phosphate Shuttle
83
In what part of the cell can you find the electron transport chain?
Inner mitochondrial membrane
84
In Anaerobic Glycolysis, NADH used to
Reduce pyruvate to lactate
85
Strictly Glycolytic Organs
RBCsLensCornea of eyeKidney medullaTestesWBCs
86
ATP yield of Glycolysis
Anaerobic: 2 ATP Aerobic: 6 (or 8) ATP
87
Found in RBCs where phosphoglycerate kinase is bypassed; Reduces hemoglobin affinity for O2
2,3-Bisphosphoglycerate
88
Inhibits pyruvate dehydrogenase by binding to lipoic acid; Competes with inorganic phosphate as a substrate for glyceraldehyde-3-phosphate dehydrogenase
Arsenic poisoning (Pentavalent Arsenic)
89
Most common enzyme defect in glycolysis; Manifests as chronic hemolytic anemia
Pyruvate Kinase Deficiency
90
Low exercise capacity, particularly on high carbohydrate diets
Muscle Phosphofructokinase Deficiency
91
Pyruvate kinase deficiency and G6PD deficiency both present with intravascular hemolytic anemia. Important differences are:
1) G6PD has HEINZ BODIES in the peripheral smear2) G6PD often has a precipitating history of oxidative stress
92
Alternate Fates of Pyruvate
Pyruvate➡️Acetyl CoAEnzyme: Pyruvate dehydrogenase complex
93
Co-enzymes of Pyruvate dehydrogenase complex
1) Lipoic Acid2) NAD3) FAD4) Thiamine pyrophosphate5) Coenzyme A
94
Pyruvate➡️Acetyl CoASubstrate?Product?Activator?Inhibitor?
Substrate: PyruvateProduct: Acetyl CoA, NADH, and CO2Activator: NAD+, CoA and pyruvateInhibitor: NADH, acetyl CoA, ATP
95
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
Pyruvate Dehydrogenase Deficiency
96
Treatment of Pyruvate Dehydrogenase Deficiency
Ketogenic Diet
97
Alcohol + Nutritional deprivation = Thiamine DeficiencyAn acquired pyruvate dehydrogenase deficiency➡️fatal pyruvic and lactic acidosis
Chronic Alcoholism
98
Final common pathway for aerobic oxidation of ALL nutrients; Provides majority of ATP for energy
Tricarboxylic Acid Pathway (TCA) aka Kreb's Cycle or Citric Acid Cycle
99
TCA: Where does it occur?
In ALL cells with mitochondria
100
TCA: What is the substrate?
Acetyl Coa
101
TCA: What are the products?
CO2, GTP, NADH and FADH2
102
TCA: Rate limiting step
Reaction: isocitrate➡️alpha-ketoglutarateEnzyme: isocitrate dehydrogenase
103
MNEMONIC: Officer Can I Keep Selling Sex For Money
OxaloacetateCitrateIsocitrateKetoglutarateSuccinyl CoASuccinateFumateMalate
104
Acetyl CoA + Oxaloacetate ➡️Citrate
Enzyme: Citrate synthase
105
Citrate➡️Isocitrate (isomerization)
Enzyme: AconitaseInhibitor: Fluoroacetate (rat poison)
106
Isocitrate➡️alpha-ketoglutarate
Rate limiting stepEnzyme: Isocitrate dehydrogenaseProducts: CO2 and NADH
107
Alpha-ketoglutarate➡️Succinyl-CoA
Enzyme: alpha-ketoglutarate dehydrogenaseCo-enzyme: similar to pyruvate dehydrogenaseProducts: CO2 and NADHInhibitor: arsenite
108
Succinyl-CoA➡️Succinate
Enzyme: succinate thiokinaseProducts: GTP by substrate level phosphorylation
109
Succinate➡️fumarate
Enzyme: succinate dehydrogenaseProducts: FADH2
110
Fumarate➡️Malate
Enzyme: Fumarase (Fumarate hydratase)
111
Malate➡️Oxaloacetate
Enzyme: Malate dehydrogenaseProducts: NADH
112
TCA Intermediates: Delivers acetyl CoA to the cytoplasm for fatty acid synthesis via citrate shuttle
Citrate
113
TCA Intermediates: Heme synthesis and activation of ketone bodies in extrahepatic tissues
Succinyl CoA
114
TCA Intermediates: May be used for gluconeogenesis
Malate
115
ATP yield for TCA
Acetyl CoA: 12 ATPPyruvate: 15 ATP (extra 3 ATP - from NADH)
116
Production of New glucose
Gluconeogenesis
117
Gluconeogenesis from the following intermediates:
1) intermediates of glycolysis and the TCA2) glycerol from triacylglycerols3) lactate through the Cori Cycle4) carbon skeletons (alpha-ketoacids) of glucogenic amino acids
118
Gluconeogenesis: Where does it occur?
Liver 90%Kidney 10%Prolonged fasting: Kidney 40%(In both mitochondria and cytoplasm)
119
Gluconeogenesis: Substrate
Pyruvate
120
Gluconeogenesis: Product
Glucose
121
Gluconeogenesis: Rate limiting step
Reaction: Fructose-1,6-biphosphate➡️Fructose-6-phosphateEnzyme: Fructose-1,6-biphosphataseActivator: ATPInhibitor: Fructose-2,6-biphosphate and AMP
122
Conversion of lactate to glucose
Cori Cycle
123
Cori Cycle: Energy Expense
4 ATP molecules
124
True or False: Muscle cannot reconvert lactate to glucose. Lactate must first be transported to the liver for gluconeogenesis.
True
125
Important steps in Gluconeogenesis
Step 10: Pyruvate➡️OAA➡️PEPStep 3: Fructose-1,6-biphosphate➡️Fructose-6-phosphateStep 1: Glucose-6-phosphate➡️Glucose
126
Requires biotin and ATP; Allosterically activated by Acetyl CoA
Pyruvate carboxylase
127
Requires GTP
PEP Carboxykinase
128
ALL Carboxylases require ____ as a Co-factor
Biotin
129
Promotes Glycolysis and Inhibits Gluconeogenesis
Fructose-2,6-biphosphateActivates: Phosphofructokinase-1➡️favors GlycolysisInhibits: Fructose-1,6-biphosphatase➡️inhibits Gluconeogenesis
130
Final step of Gluconeogenesis which is shared with Glycogen degradation
Glucose-6-phosphate➡️Glucose
131
End goal of Glucose-6-phosphate➡️Glucose
Releases free Glucose into the circulation
132
Enzyme of Glucose-6-phosphate➡️Glucose
Glucose-6-phosphatase
133
Glucose-6-phosphate➡️Glucose: Where does it occur?
Liver and Kidneys only
134
Regulation of Gluconeogenesis
1) Circulating levels of Glucagon2) Availability of Glucogenic substrates3) Allosteric activation by Acetyl CoA4) Allosteric inhibition by AMP
135
Energy expenditure of Gluconeogenesis
Use of 4 ATPsUse of 2 GTPsOxidizes 2 NADH back to NAD+
136
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)
Glucosuria
137
Alcoholism: High amounts of cytoplasmic NADH is formed by:
Alcohol dehydrogenaseAcetaldehyde dehydrogenase
138
Hypoglycemia: High amounts of NADH favors the ff reactions:
Pyruvate➡️LactateOAA➡️MalateDHAP➡️Glycerol-3-phosphate
139
High fetal glucose consumption; Risk of maternal and fetal hypoglycemia especially during fasting
Hypoglycemia during Pregnancy
140
Due to increase estrogen; Fasting Hypoglycemia
Hyperinsulinemia
141
Due to increase HPL; Post-prandial hyperglycemia
Insulin resistance
142
Premature and LBW babies have little adipose tissue; Enzymes of Gluconeogenesis are not yet completely functional
Hypoglycemia in the Neonate
143
Major storage carbohydrate in animals; Branched polymer of alpha-D-glucose
Glycogen
144
Glycogen: Where's it stored?
Liver and Muscle onlyLiver: 100g = 6% of liverMuscle: 400g =
145
Synthesis of new glycogen molecules from alpha-D-glucose
Glycogenesis
146
Glycogenesis: Where does it occur?
Liver Muscle(Occurs in cytosol)
147
Glycogenesis: Substrates
UDP-glucoseATP and UTPGlycogenin - a core, primer protein
148
Glycogenesis: Product
Glycogen
149
Glycogenesis: Rate limiting step
Reaction: Elongation of glycogenEnzyme: Glycogen synthase
150
Important Steps in Glycogenesis
Glucose-6-phosphate➡️Glucose-1-phosphateSynthesis of UDP-GlucoseElongation of Glycogen chainsFormation of branches in glycogen
151
Enzyme of Glucose-6-phosphate➡️Glucose-1-phosphate
Enzyme: Phosphoglucomutase(Reversible - Not a rate limiting step)
152
Synthesis of UDP-Glucose: Activated form
Glucose
153
Synthesis of UDP-Glucose: Enzyme
UDP-glucose phosphorylase
154
Synthesis of UDP-Glucose: Substrates
Glucose-1-phosphateUTP
155
Rate limiting step of Glycogenesis
Elongation of Glycogen chainsEnzyme: Glycogen synthase
156
Formation of branches in glycogen: Enzyme
Branching enzyme composed of amylo alpha(1-4)➡️alpha(1-6) transglucosidase
157
Shortening of glycogen chains to produce molecules of a-D-glucose
Glycogenolysis
158
Glycogenolysis: Where does it occur?
Liver Muscle(In the cytosol)
159
Glycogenolysis: Substrate
Glycogen
160
Leaves about 4 glucose residues before a branch point
Limit dextrin
161
Glycogenolysis: Products
Glucose-1-phosphateFree glucose - produced during the debranching processLiver: can release free glucose to circulationMuscle: limited to glucose-6-phosphate within muscle only
162
Glycogenolysis: Rate limiting step
Reaction: Removal of glucose Enzyme: glycogen phosphorylase
163
Glycogenolysis: Removal of branches
Enzyme: debranching enzymeBonds cleave: alpha(1-4) and alpha(1-6)Products: Free Glucose
164
Conversion of Glucose-1-phosphate to Glucose-6-phosphate
Enzyme: phosphoglucomutaseLiver: Glucose-6-phosphate further converted to glucoseMuscle: Glucose-6-phosphate is the final product
165
Lysosomal degradation of Glycogen
Enzyme: alpha(1-4) glucosidase aka Acid maltase - an enzyme that is different from glycogen phosphorylase
166
Glycogen Storage Disease: Type I
Von Gierke'sGlucose-6-phosphatase deficiencyHypoglycemia + Lactic Acidosis/Ketosis
167
Glycogen Storage Disease: Type II
Pompe'sAcid maltase deficiencyCardiomegaly and heart failure
168
Glycogen Storage Disease: Type III
Cori'sDebranching enzyme deficiencyMilder form of Type I
169
Glycogen Storage Disease: Type IV
Andersen'sBranching enzyme deficiencySevere form of Type I (early death from heart and liver failure)
170
Glycogen Storage Disease: Type V
McArdle'sSkeletal Muscle glycogen phosphorylase deficiencyGlycogen in muscle: Muscle cramps + myoglobinuria but NO lactic acidosis
171
Glycogen Storage Disease: Type VI
Hers'Hepatic Glycogen phosphorylase deficiencyGlycogen in liver cells: hypoglycemia
172
Glycogen Storage Disease: Type VII
Tarui'sPFK deficiencyLike Type V + hemolytic anemia
173
Glycogen Storage Disease: Type VIII
Hepatic phosphylase kinase deficiencyLike Type VI
174
Important source of Galactose
Disaccharide lactose in milk
175
Phosphorylation of galactose
Galactose➡️Galactose-1-phosphateEnzyme: Galactokinase or Hexokinase
176
Formation of UDP-galactose
Galactose-1-phosphate + UDP-glucose➡️UDP-galactose + glucose-1-phosphateEnzyme: galactose -1-phosphate uridyl transferase
177
Use of galactose as carbon source
UDP-galactose➡️UDP-glucoseEnzyme: UDP-hexose-4-epimerase
178
Causes Galactosemia and Galactosuria
Galactokinase Deficiency
179
Absence of galactose-1-phosphate uridyltransferase; Autosomal recessive; Galactitol accumulation - causes Cataracts + Hepatosplenomegaly + mental retardation; Absolute contraindication to breastfeeding
Classic Galactosemia
180
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
Gal-1-Phosphate Uridyltransferase Deficiency
181
Important source of fructose
Disaccharide sucrose found in honey and fruits
182
Phosphorylation of fructose
Fructose➡️Fructose-1-phosphateEnzyme: Fructokinase or hexokinase
183
Formation of DHAP an Glyceraldehyde
Fructose-1- phosphate➡️dihydroxyacetone phosphate (DHAP) + GlyceraldehydeEnzyme: Aldolase B
184
For Glycolysis; Fructose-1,6-biphosphate➡️DHAP+glycerol-3-phosphate
Aldolase A
185
For Fructose metabolism; Fructose-1-phosphate➡️DHAP+glyceraldehyde
Aldolase B
186
Defect in Fructokinase; Benign and asymptomatic whose only symptom is the appearance of fructose in blood and urine
Essential Fructosuria
187
Deficiency of Aldolase B; Autosomal recessive; Fructose-1-phosphate accumulates leading to decrease phosphate, decrease glycogenolysis, decrease gluconeogenesis; hypoglycemia, jaindice, cirrhosis, vomiting
Fructose Intolerance
188
Important component of Glycoprotein
Mannose Metabolism
189
Isomerization between mannose and fructose
Mannose-6-phosphate➡️fructose-6-phosphateEnzyme: phosphomannose isomerase
190
Glucose➡️Sorbitol
Enzyme: Aldose reductaseFound in lens, retina, Schwann cells, liver, kidney, placenta, RBC, ovaries, seminal vesicles
191
Sorbitol➡️Fructose
Enzyme: Sorbitol dehydrogenaseFound in the seminal vesicles only since Fructose is the fuel of sperm
192
Pentose Phosphate Pathway: What is it for?
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
Pentose Phosphate Pathway: Where does it occur?
In the cytoplasmActive in: Liver, Adipose tissue, Adrenals, Thyroid, Testes, RBC, Lactating membranesLow in: skeletal muscle, non-lactating mammaries
194
Pentose Phosphate Pathway: Substrate
Glucose-6-phosphate(No consumption or production of ATP)
195
Pentose Phosphate Pathway: Products
Ribose-5-phosphateFructose-6-phosphateGlyceraldehyde-3-phosphateNADPH
196
Pentose Phosphate Pathway: Rate limiting step
Reaction: glucose-6-phosphate➡️6-phosphogluconateEnzyme: glucose-6-phosphate dehydrogenase
197
Pentose Phosphate Pathway: Phase 1
OxidativeIrreversibleEnzyme: glucose-6-phosphate dehydrogenaseProduct: NADPH ribulose-5-phosphate
198
Pentose Phosphate Pathway: Phase 2
Non-oxidativeReversibleEnzyme: Transketolase (requires Thiamine)Product: ribose-5-phosphate, glyceraldehyde-3-phosphate, fructose-6-phosphate
199
Removes H2O2 in reaction catalyzed by glutathione peroxidase; very important in RBCs
Glutathione
200
Reduced glutathione sequester harmful H2O2
Enzyme: glutathione peroxidase
201
Reduced glutathione recreated using NADPH
Enzyme: glutathione reductase
202
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
Glucose-6-phosphate Dehydrogenase Deficiency
203
Precipitating factors of Glucose-6-phosphate Dehydrogenase Deficiency
Infection - most commonDrugs - antibiotics (sulfonamides, chloramphenicol), antimalarials (primaquine), antipyretics (except ASA and paracetamol)Fava beans
204
Altered RBCs due to phagocytic removal of Heinz bodies in spleen
Bite cells in Heinz Bodies
205
Deficiency in NADPH oxidase; severe, persistent and chronic pyogenic infections
Chronic Granulomatous Disease
