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NBDE 1 > Metabolic Pathways > Flashcards

Metabolic Pathways Flashcards

1
Q

What is the rate limiting enzyme for glycolysis?

A

Phosphofructokinase

PFK

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2
Q

What is the rate limiting enzyme for gluconeogenesis?

A

fructose bisphosphatase-2

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3
Q

What is the rate limiting enzyme for TCA cycle

A

isocitrate dehydrogenase

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4
Q

What is the rate limiting enzyme for glycogen synthesis

A

glycogen synthase

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5
Q

What is the rate limiting enzyme for glycogenolysis

A

glycogen phosphorylase

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6
Q

What is the rate limiting enzyme for HMP shunt

A

glucose 6 phosphate dehydrogenase (G6PD)

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7
Q

What is the rate limiting enzyme for urea cycle

A

carbamoyl phosphate synthetase

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8
Q

What is the rate limiting enzyme for Fatty acid synthesis

A

Acetyl Co-A carboxylase

ACC

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9
Q

What is the rate limiting enzyme for fatty acid oxidation (Beta oxidation)

A

carnitine acetyltransferase

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10
Q

What is the rate limiting enzyme for ketogenesis

A

HMG Co-A synthase

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11
Q

What is the rate limiting enzyme for cholesterol synthesis

A

HMG CoA reductase

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12
Q

What is the embden meyerhof pathway?

A

glycolysis

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13
Q

Glycolysis

Location

Net ATP

A

cystol

2

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14
Q

TCA cycle

Location

Net ATP

A

mitochondrial matrix

2 GTP

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15
Q

ETC

Location

Net ATP

A

inner mitochondrial membrane

32 (G3P shuttle)

34 (malate aspartae shuttle)

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16
Q

What is the fate of pyruvate during oxidation

Enzyme

Product

Function

A

Enzyme: pyruvate dehydrogenase

Product: acetyl coa

Function: ATP production and FA synthesis

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17
Q

What is the fate of pyruvate during reduction

Enzyme

Product

Function

A

Enzyme: lactate dehydrogenase

Product: lactate

Function: anaerobic glycolysis

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18
Q

What is the fate of pyruvate during carboxylation

Enzyme

Product

Function

A

What is the fate of pyruvate during

Enzyme: pyruvate carboxylase

Product: oxaloacetate

Function: gluconeogenesis; replenishes TCA

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19
Q

What is the fate of pyruvate during transamination

Enzyme

Product

Function

A

What is the fate of pyruvate during

Enzyme: alanine transaminase

Product: alanine

Function: amino acid synthesis

20
Q

What are the four different steps of gulconeogenesis from glycolysis?

A
  1. Pyruvate –> oxaloacetate

E: pyruvate carboxylase; uses 2 ATP –> 2 ADP

  1. Oxaloacetate –> PEP

E: PEP carboxykinase; uses 2 GTP –> ADP

  1. Fructose 1,6 bisphosphate –> Fructose 6 phosphate

E: (FBPase) Fructose Bisphophatase-1; uses H2O –> Pi

  1. G6P –> glucose

E: (G6Pase) Glucose-6-Phosphatase-1; uses H2O –> Pi

21
Q

What are the 2 places for gluconeogenesis?

A

Liver (90%)

Kidney (10%)

22
Q

Why does gluconeogenesis not occur in the muscle?

A

The muscle lacks the glucose 6 phosphotase enzyme, the last step to convert G6P to glucose.

23
Q

When does gluconeogenesis occur?

A

Occurs when there is low blood glucose.

24
Q

What inhibits the PEP carboxykinase enzyme?

A

Insulin

remember that carboxykinase is used in glycogenolysis and the whole point of the cycle is to increase blood glucose levels.

25
Q

What is an allosteric inhibitor of PFK?

A

High [ATP]

High [Citrate] - krebs cycle

26
Q

What is an inhibitor of the enolase enzyme? Signficance in oral bacteria?

A

Fluoride

Fluoride inhibits glycolysis in oral bacteria thus kills bacteria no production of acid –> no caries!

27
Q

During the glycogenesis reaction, where do the reactions occur?

A

There are two locations:

Mitochondria: conversion of pyruvate to oxaloacetate

Cytoplasma: everything else (oxaloacetate –> glucose)

28
Q

What is the structure of glycogen?

A

a polysaccharide of glucose; storage form of glucose

made alpha 1,4 straight bond and alpha 1.6 branched bonds

alpha 1,4 (most common)

alpha 1,6 bonds (faster mobilization)

29
Q

Where are most carbs stored in the body?

What is the role of glycogen stored in liver? muscle?

A

Liver and muscle

Liver maintains blood glucose levels

Muscle provides quick energy, glucose during exerise

30
Q

What is the enzyme of glycogenolysis? Function? What intermediates activate the enzyme?

A

Glycogen phsophorylase

Phosphorylation to cut off end of glycogen branch to turn into active form

Intermediates: cAMP, epinephrine, glucagon

31
Q

Does glucagon activate the glycogen phosphrylase enzyme in both the liver and muscle?

A

No, glucagon cannot act on the muscle because it doesnt have a role in blood glucose regulation.

32
Q

Glucagon acts on the liver to start glycogenolysis, what other system does it work on?

A

It activates the adenyly cyclase in adipocyte plasma membrane to raise cAMP which turns other enzymes on to breakdown triglycerols to FAs to be used as fuel.

33
Q

What are the differnet numbers of carbons involved in CAC?

A

Oxaloacetate (4 C)

Citrate (6C)

isocitrate (6C)

alpha ketoglutarate (5C)

Succinyl CoA (4C) –> Oxaloacetate (4C)

34
Q

what is the most immediate available source of oxaloacetate?

A

aspartic acid

note: OOA is interconvertable with aspartic acid

35
Q

What is the only enzyme that is in both CAC and ETC?

A

succinate dehydrogenase

36
Q

What inhibits the TCA and ETC cycle?

A

malonate

the competitve inhibitor of succinate dehydrogenase.

37
Q

During ETC, NADH is fed to which enzyme? FADH2?

A

NADH- Cytochrome Complex 1- NADH dehydrogenase complex

FADH2- Cytochrome Complex 2 - succinate dehydrogenase complex

38
Q

What is another name for the pentose phosphate pathway?

A

hexose monophosphate shunt (HM-shunt)

39
Q

what is the stoichiochemistry of the pentose phosphate pathway?

A

glucose 6 phosphate + 2 NADP + H2O –> Ribose 5 phosphate + 2 NADPH + 2H + CO2

40
Q

What is the ultimate goal of PPP? Is ATP produced?

A

To produce ribose for nucleotide synthesis and NADPH for fatty acid and steroid synthesis.

NO

41
Q

NADPH produced from PPP can also help with what?

A

Helps rid of free radicals of erythrocytes and H2O2 (hydrogen peroxide).

42
Q

What is the rate limiting step of PPP? What does this enzyme catalyze?

A

Glucose 6 phosphate dehydrogenase

43
Q

What occurs when there’s a deficiency of glucose 6 phosphate dehydrogenase?

A

hemolytic anemia due to a decrease in NADPH production thus increase in oxidizing agents in RBCs

44
Q

What is the pathway of glycogenolysis? What is the pathway of glycogenolysis?

A

Gylocgenolysis

Glycogen —(glycogen phosphorylase)—-> glucose 1 phosphate –(phosphoglucomutase)—> glucose 6 phosphate –(glucose 6 phosphatase)—–> glucose

45
Q

What is the pathway of glycogenesis? What is the pathway of glycogenesis?

A

Glucose –(hexokinase)—-> glucose 6 phosphate —-(phosphoglucomutase)—-> glucose 1 phosphate –(glycogen synthase)—> glycogen

NBDE 1 (9 decks)

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