well fed state ÎÎ insulin dec glucagon

fasting state dec insulin inc glucagon

44. Glycolysis Flashcards by iya gerzon

major pathway for glucose metabolism that converts glucose into 3 carbon compounds to provide energy

glycolysis

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where does glycolysis occur

cytosol of all mammalian cells

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what is the substrate of glycolysis?

glucose

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what are end products of glycolysis

2 molecules of either pyruvate or lactate

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rate limiting step of glycolysis

fructose-6-phosphate –> fructose-1,6- biphosphate

enz. Phosphofructokinase-1

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important steps of glycolysis

glucose -> glucose-6-phosphate

enz. hexokinase/ glucokinase

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fructose-6-phosphate

phosphorylation

fructose-6-phosphate –> fructose-1,6-biphosphate

PFK-1

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PFK-2 product

fructose-2,6- biphosphate

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PEP -> pyruvate

pyruvate kinase

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2 steps of glycolysis produce ATP via substrate level phosphorylation

(1) 1,3-biphosphoglycerate –> 3-phosphoglycerate
enz. phosphoglycerate kinase

(2) phosphoenolpyruvate –> pyruvate
enz. pyruvate kinase

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production of NADH in glycolysis

glyceraldehyde-3-phosphate –> 1,3 biphosphoglycerate

enz.glyceraldehyde-3-phosphate dehydrogenase

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this enzyme can phosphorylate glucose and other hexoses is present in most tissues

hexokinase

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glucokinase is present in

liver parenchymal cells

* islets of pancreas

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hexokinase is inhibited by

glucose-6-P

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glucokinase is inhibited by

fructose-6-P

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this enzyme can phosphorylate glucose and other hexoses
low Km,high affinity
low Vmax

hexokinase

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this enzyme can phosphorylate glucose and other hexoses

* induced by insulin

glucokinase

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•this enzyme can phosphorylate glucose and other hexoses

High km, low affinity
high Vmax

glucokinase

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activator of PFK-1

fructose-2,6-BP

* AMP

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activator of PFK-2

well fed state
ÎÎ insulin
dec glucagon

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inhibitor of PFK-1

citrate

* ATP

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inhibitor of PFK-2

fasting state
dec insulin
inc glucagon

how many ATP is yielded per molecule of PEP

1 ATP

PEP -> pyruvate
enz. pyruvate kinase

activated by?

fructose-1,6-BP

PEP -> pyruvate enz. pyruvate kinase inhibited by?

glucagon

type of glycolysis * cells without mitochondria * cells without sufficient O2

anaerobic glycolysis

type of glycolysis •cells with mitochondria •with adequate O2 supply

aerobic glycolysis

end product of anaerobic glycolysis

lactate

end product of | aerobic glycolysis

pyruvate

used to reduce pyruvate to lactate

NADH

major fate of pyruvate in lens, cornea, eye, kidney, medulla, testes, RBCs,WBCs

anaerobic glycolysis

lactic acidosis is seen in

* vigorous exercise * septic shock * cancer cachexia

NADH to pass through inner mitochondrial membrane requires

•glycerophosphate shuttle or •malate aspartate shuttle

ATP yield with glycerophosphate shuttle

1 NADH = 1.5 ATPs

ATP yield with | malate aspartate shuttle

1 NADH = 2.5 ATPs

this shuttle of NADH is found in | most tissues and heart muscle

malate aspartate shuttle

this shuttle of NADH is found in | brain and white muscle

glycerophosphate shuttle

net ATP yield | aerobic glycolysis

5 or 7

net ATP yield with anaerobic glycolysis

2 ATP

thhis is found in RBCs where rxn catalyzed by phosphoglycerate kinase is bypassed

2,3-biphosphoglycerate 1,3- BPG –> 2,3-BPG enz. biphosphoglycerate mutase

Fates of Pyruvate :

1. Anaerobic glycolysis •lactate (lactate dehydrogenase) 2. Gluconeogenesis •oxaloacetate (pyruvate carboxylase) 3. Citric acid cycle •acetyl coa (pyruvate dehydrogenase) 4. Fermentation •Ethanol (pyruvate decarboxylase)

pyruvate –> acetyl coa

pyruvate –> acetyl coa enzyme: pyruvate dehydrogenase complex co-enzymes: 1. thiamine pyrophosphate 2. FAD 3. NAD+ 4. coenzyme A (pantothenic acid) 5. lipoic acid

most common enzyme defect in glycolysis

pyruvate kinase deficiency

provide lipids as alternative fuel | in the muscle

muscle phosphofructokinase

most common cause of congenital lactic acidosis

pyruvate dehydrogenase deficiency

inheritance of pyruvate dehydrogenase deficiency

X-linked dominant

clinical manifestations of pyruvate dehydrogenase deficiency

* lactic acidosis | * brain : ÎÎ lactate , decrease acetyl COA -> brain deprivation of acetyl CoA -> psychomotor retardation and death

tx pyruvate dehydrogenase deficiency

ketogenic diet

aldolase A deficiency manifests as

hemolytic anemia

pyruvate kinase deficiency leads to

hemolytic anemia

mutations that dec activity of glucokinase leads to

Maturity onset diabetes of the young, type 2

Maturity onset diabetes of the young, type 2 due to glucokinase dec activity tx

majority no tx required | except during pregnancy

arsenic poisoning competes with

inorganic phosphate as a substrate | for glyceraldehyde-3-P dehydrogenase

chronic alcoholism effect on tiamine

inhibits absorption | cause fatal pyruvic and lactic acidosis