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Bch 201 > Gluconeogenesis > Flashcards

Gluconeogenesis Flashcards

1
Q

GLUCONEOGENESIS

It is the process by which glucose molecules are produced from _______ precursors.

These include ____,___ amino acids, _____ part of fat and ______ derived from odd chain fatty acids

A

non-carbohydrate

lactate; glucogenic; glycerol

propionyl CoA

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2
Q

Gluconeogenesis occurs mainly in the _____, and to a lesser extent in the ______.

The pathway is partly _____ and partly _______.

A

liver

renal cortex

mitochondrial

cytoplasmic

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3
Q

Key Gluconeogenic Enzymes

  1. __________
  2. ___________
  3. ____________
  4. ________________
A

Pyruvate carboxylase

Phosphoenol pyruvate carboxy kinase

Fructose-1-6-bisphosphatase

Glucose-6-phosphatase

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4
Q

Gluconeogenesis is m a reversal of glycolysis.

A

F

Gluconeogenesis involves several enzymes of glycolysis, but it is not a reversal of glycolysis.

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5
Q

Pyruvate Carboxylase Reaction

Pyruvate in the _____ enters the _____.

Then, ________ of pyruvate to ______ is catalysed by a mitochondrial enzyme, pyruvate carboxylase . It needs the co-enzymes _____ and ____

A

cytoplasm

mitochondria

carboxylation; oxaloacetate

biotin and ATP.

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6
Q

Gluconeogenesis

The carboxylation of pyruvate takes place in mitochondria.
So, oxaloacetate is generated inside the mitochondria.

This oxaloacetate has to be transported from mitochondria to ______, because further reactions of gluconeogenesis are taking place in _____.

This is achieved by the ___________________.

A

cytosol

cytosol

malate aspartate shuttle

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7
Q

In malate aspartate shuttle

Oxaloacetate is first converted to ____, which traverses the membrane and reaches ____ where it is then re-converted to oxaloacetate.

Oxaloacetate may also be transported as aspartate formed by _____ of oxaloacetate.

A

malate ; cytoplasm

transamination

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8
Q

Malate dehydrogenase is present in both mitochondria and cytoplasm.

T/F

A

T

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9
Q

When alanine is the substrate for gluconeogenesis, the ____ shuttle predominantly operates, because ____ is also required in the cytoplasm for the gluconeogenesis to continue.

When lactate is the substrate for gluconeogenesis, the _____ shuttle operates, because sufficient _____ is available in the cytoplasm by the LDH reaction.

A

malate

NADH

aspartate

NADH

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10
Q

Phosphoenol Pyruvate Carboxy Kinase

In the cytoplasm, PEPCK enzyme then converts _______ to ______ by removing a molecule of ___.

____ donates the phosphate

A

oxaloacetate to phosphoenol pyruvate

CO2

GTP

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11
Q

Partial Reversal of Glycolysis

The phosphoenol pyruvate undergoes further reactions catalyzed by the glycolytic enzymes to form ______

A

fructose-1,6-bisphosphate

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12
Q

In gluconeogenesis

Fructose 1,6-bis-phosphate is then acted upon by _______ to form __________

A

fructose 1,6-bisphosphatase

fructose -6-phosphate.

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13
Q

Gluconeogenesis

The glucose 6-phosphate is hydrolysed to _______ by _________

A

free glucose

glucose-6-phosphatase.

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14
Q

Glucose-6-phosphatase is active in ______.

It is present in _____ and ______ to a lesser extent, but is absent in _____.

A

liver

kidney and intestinal mucosa

muscle

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15
Q

Energy Requirement of glyuconeogenesis

The reactions catalyzed by pyruvate carboxylase, phosphoenol pyruvate carboxy kinase and phospho glycerate kinase require ___ ATP each

so ___ ATPs are used by 1 pyruvate residue to produce ___ molecule of glucose; or ___ ATPs are required to generate ___ glucose molecule.

A

one

3

one-half

6

one

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16
Q

Lactate to glucose

The lactate formed in the muscle is transported to the _____ where _______ converts lactate to _______. The pyruvate enters the gluconeogenic pathway to form ____.

A

liver

lactate dehydrogenase

pyruvate

glucose

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17
Q

____________ Cycle aka Cahill Cycle

A

Glucose-Alanine

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18
Q

Glucose-Alanine Cycle (Cahill Cycle)

Alanine is transported to ____ where it is _____ to _____ and converted to glucose.

A

liver

transaminated

pyruvate

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19
Q

Glucose-alanine cycle is important in conditions of starvation

T/F

A

T

20
Q

Alanine cycle is intimately related with ____ cycle

A

Cori’s

21
Q

Propionyl CoA is formed from odd chain fatty acids and carbon skeleton of some amino acids. It is converted to _______.

It is a (minor or major?) source for glucose.

A

succinyl CoA

Minor

22
Q

Even chain fatty acids can be converted to glucose

T/F

A

F

Even chain fatty acids cannot be converted to glucose

23
Q

_______ is an activator of pyruvate carboxylase

_____ is an activator of Fructose-1,6-bisphosphatase

A

Acetyl CoA

Citrate

24
Q

Gluconeogenesis is (enhanced or hindered ?) by ATP.

A

Enhanced

25
Q

CORI’S CYCLE OR LACTIC ACID CYCLE

It is a process in which glucose is converted to lactate in the ____; and in the ____ this lactate is re-converted into glucose.

A

muscle

liver

26
Q

In an actively contracting muscle, pyruvate is reduced to ______ which may tend to ____ in the muscle.

A

lactic acid

accumulate

27
Q

The muscle cramps, often associated with strenuous muscular exercise, are thought to be due to ________

A

lactate accumulation

28
Q

To prevent the lactate accumulation, body utilises Cori’s cycle.

This lactic acid from muscle diffuses into the ______. Lactate then reaches ____, where it is ____ to ____.

Thus, it is channelled to ______ pathway .

A

blood

liver

oxidized

pyruvate

gluconeogenesis

29
Q

______ is the storage form of carbohydrates in the human body.

The major sites of storage are _____ and _____.

A

Glycogen

liver and muscle

30
Q

The glycogen content of liver is (more or less?) than in the skeletal muscle

But the total quantity of muscle glycogen is (more or less?) than liver glycogen because of the ________

A

More

Less

larger muscle mass

31
Q

When blood glucose level falls, (muscle or liver ?) glycogen is broken down and helps to maintain blood glucose level.

A

Liver

32
Q

The function of muscle glycogen is to act as ______ for ______.

A

reserve fuel

muscle contraction

33
Q

All the enzymes related to glycogen metabolism are located in the _______

A

cytoplasm

34
Q

In glycogenolysis

_______ removes glucose as _________ from glycogen (phosphorolysis)

The _____ linkages in the glycogen are cleaved.
It removes glucose units one at a time.

Enzyme sequentially hydrolyses alpha-1,4 glycosidic linkages, till it reaches a glucose residue, ____ glucose units away from a branch point .

A

Glycogen phosphorylase

glucose-1-phosphate

alpha-1,4

3-4

35
Q

Glycogen phosphorylase contains __________ as a prosthetic group.

A

pyridoxal phosphate (PLP)

36
Q

Glycogen phosphorylase

cannot attack the ____ linkage at _____ point.

A

1,6

branch

37
Q

If glycogen phosphorylase alone acts on a glycogen molecule, the final product is a highly branched molecule; it is called _____

A

limit dextrin.

38
Q

Regulation of Muscle Glycogen Phosphorylase

Skeletal muscle glycogen is degraded only when the demand for ATP is (high or low?) . The regulation of glycogenolysis in skeletal muscle is by ______ and ____ released from sarcoplasmic reticulum. _____ has no effect on muscle glycogenolysis.

A

High

epinephrine and calcium

Glucagon

39
Q

Debranching by bifunctional (two) Enzymes

Then a block of __ glucose residues ( ____ unit) are transferred from the branching point to another branch.

This enzyme is alpha-1,4 → _______.

Now the branch point is free.

Then __________ (debranching enzyme) can hydrolyse the remaining glucosyl unit held in alpha-1,6 linkage at the branch point

This glucose residue is released as free glucose.

At this stage, the ratio of glucose-1phosphate to free glucose is about __:__

The _______ and _______ will together convert the branch point to a linear one.

With the removal of the branch point, phosphorylase enzyme can proceed with its action.

A

3; trisaccharide

alpha-1,4 glucan transferase

alpha1,6- glucosidase

8:1.

transferase and alpha-1,6-glucosidase

40
Q

In glycogenolysis

Phosphogluco mutase

Phosphorylase reaction produces _______ while debranching enzyme releases _____.

The glucose-1-phosphate is converted to _________ by ________

A

glucose-1phosphate

glucose

glucose-6-phosphate

phosphoglucomutase

41
Q

In glycogenolysis

Next, hepatic _________ hydrolyses glucose-6-phosphate to glucose.

The free glucose is released to the ______

A

glucose-6-phosphatase

blood stream.

42
Q

——— Lacks Glucose-6-phosphatase

A

Muscle

43
Q

Muscle will release glucose to the blood stream

T/F

With reason

A

F

Muscle will not release glucose to the blood stream, because muscle tissue does not contain glucose-6-phosphatase.

44
Q

Fate of glucose-6-phosphate in muscle

A

Instead, in muscle, glucose-6-phosphate undergoes glycolysis to produce ATP for muscle contraction.

45
Q

In muscle, the energy yield from one glucose residue derived from glycogen is ____ ATP molecules

Why???

A

3

because no ATP is required for initial phosphorylation of glucose (step 1 of glycolysis).

Bch 201 (11 decks)

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