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MCAT Self Study > Biochemistry Metabolism > Flashcards

Biochemistry Metabolism Flashcards

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MCAT flashcards
1
Q

What are the important keys to glycolysis?

A
  1. Kinase transfers 2 ATP molecules to Glucose in order to enter the cell.
  2. Glucose is split into two, 3 carbon molecules, which will eventually become pyruvate.
  3. NADH is created from NAD +
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2
Q

What is substrate level phosphorylation?

A

Substrate-level phosphorylation reactions are characterized by the direct transfer of a phosphate group from a reactive intermediate onto an ADP or GDP molecule.

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3
Q

What is fermentation?

A

Fermentation occurs in anaerobic conditions. Glycolysis is still present. The two pyruvate molecules turn into either lactic acid or ethanol. NADH returns to NAD +. CO2 is released as a by product.

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4
Q

How are glycogen molecules linked?

A

Glycogen is a polymer of glucose molecules linked by alpha -1,4’ glycosidic bonds

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5
Q

What two processes help in fasting stages?

A

Gluconeogenesis: formation of glucose from non carbohydrate materials.

Glycogenolysis: breakdown of glycogen into glucose.

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6
Q

What is an MCAT tip for predicting reactions with high energy?

A

Look for the answer choice with ATP or NADH as these are needed for large delta g.

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7
Q

What requirement must a substrate have in order to participate in gluconeogenesis?

A

Must have a three carbon backbone.

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8
Q

Compare saturated and unsaturated fats in terms of energy storage.

A

Saturated fats have more hydrogens per carbon so they have more reducing potential. They have the ability to store more energy.

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9
Q

Describe beta oxidation and the steps.

A

BO is the process of taking fatty acids and converting them into Acetyl- COA for the Kerb’s Cycle.

  1. Fatty acids from adipose tissues enter the bloodstream via lipoproteins and go into the cell’s mitochondrium.
  2. Fatty acid is converted to acyl- coa with 1 atp.
  3. Goes into the matrix where it is cleaved TWO CARBONS AT A TIME to form Acetyl- COA.
  4. By product is NADH, FADH2.

This process works well with even numbered fatty acids.

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10
Q

Describe ketogenesis.

A

Occurs in the mitochondria of the liver. Fatty acid is converted ketone bodies for the brain to use during extreme starvation.

3 types of ketone bodies: acetone, acetoacetic acid, and beta-hydroxybutyrate.

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11
Q

Describe the formation of fatty acids from non lipid materials.

A

In the presence of insulin and excess acetyl- coa the acetyl coa can be converted into fatty acids to be stored as triglycerides.

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12
Q

What 3 processes occur in the “fed state”

A

Glycolysis, Glycogenesis, and triglyceride storage.

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13
Q

What 3 processes occur in the “fasting state”

A

beta oxidation, glycogenolysis, gluconeogenesis.

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14
Q

Does unsaturated fats or glucose produce more ATP per unit mass?

A

Unsaturated fats.

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15
Q

What are the two keys for metabolism?

A
  1. Brain and RBC ALWAYS require glucose

2. Glucose either comes from the liver or intestines.

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16
Q

Where does gluconeogenesis occur?

A

Liver

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17
Q

ATP -> ADG

A

Very spontaneous reaction

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18
Q

Describe Pyruvate Decarboxylation:

A

Pyruvate moves into the mitochondrial matrix via integral membrane proteins.

Pyruvate is turned into AcetylCoA, Co2, NADH, and H+.
2 pyruvate means 2 of each.

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19
Q

How does NADH control ETC and Kreb’s Cycle?

A

If there is a build up of NADH then it’ll slow down the cycle.

20
Q

ETC Keys:

A

O2 is the final electron acceptor, it becomes h2o.
Inner membrane space becomes acidic.
Co2 is released in krebs.
Reduction of complexes as electrons move.

21
Q

What are the products of PPP?

A

Ribose(pentose) sugar & NADPH.

22
Q

Contrast Hexokinase & Glucosekinase

A

Hexokinase is in all cells, it has a very high affinity to glucose molecules, and therefore will have a low Km value. It is inhibited by high levels of glucose-6-phosphate.

Glucokinase is only in liver and beta cells. It has a very low affinity to glucose and therefore will have a high Km value. Induced by insulin in hepatocytes.

23
Q

What is the rate limiting enzyme for glycolysis?

A

PFK1

24
Q

Examine Phosphfructokinase 1 in glycolysis.

A

Rate limiting step for glycolysis for proceed. It is inhibited by large amounts of ATP & citrate which means glycolysis isn’t needed. It is activated with high levels of AMP because energy is needed.

25
Q

Describe PFK2

A

In liver cells, insulin activates PFK1 while glucagon inhibits Pfk1. Insulin activates PFK2 which changes fructose 6 to fructose 2-6. The presence of fructose 2-6 allows for PFK1 to allow for glycolysis to proceed. This happens EVEN IF THERE ARE HIGH LEVELS OF ATP in the liver.

26
Q

Describe Glyceraldehyde-3- phosphate dehydrogenase

A

Converts Glyceraldehyde-3- phosphate into Glyceraldehyde-1,3-bisphosphate. Also, there is a reduction of NAD+ to NADH.

27
Q

Describe 3-Phosphoglycerate Kinase

A

Takes a phosphate group from Glyceraldehyde-1,3-bisphosphate to form 3-phosphoglycerate and ATP which is substrate level phosphorylation.

28
Q

Describe Pyruvate Kinase

A

Removes phosphate group from PEP to form Pyruvate and ATP.

29
Q

What is the rate limiting enzyme for fermentation?

A

Lactate dehydrogenase , which converts NADH back to NAD+

30
Q

Describe the use of dihydroxyaceton phosphate (DHAP).

A

It can’t be used by glycolysis so it is converted to glyceraldehyde 3 phosphate via an isomerase. DHAP however can be used by the live and adipose tissue. The backbone of DHAP can be used to synthesize gycerol which can be used to form triglycerides.

31
Q

What are the irreversible steps in glycolysis?

A
  1. Hexokinase/ Glucokinase.
  2. Phosphofructokinase -1
  3. Pyruvate Kinase
32
Q

What shifts the Bohr model to the right?

A

Exercise is the RIGHT thing to do.

  • increase 2-3 BPG
  • increased H
  • decreased pH
  • increase CO2
33
Q

What are the effects of 2-3 BPG

A

Decreases affinity for oxygen on the RBC

34
Q

What is the function of Pyruvate Dehydrogenase?

A

Convert Pyruvate into AcetylCOA by getting rid of CO2

35
Q

Where does glycogen synthesis and degradation occur?

A

Liver and skeletal muscle.

Liver glycogen is broken down to maintain proper blood sugar levels. Muscle glycogen is used for exercise.

36
Q

What 4 enzymes are different in gluconeogenesis than glycolysis?

A

Pyruvate to Oxaloacetate via Pyruvate Carboxylase.
Oxaloacetate to PEP via PEP Carboxylase.
Fructose 1-6 bisphosphate to fructose 6 phosphate via fructose 1-6 bisphosphatase.
Glucose 6 phosphate to glucose via glucose 6 phosphatase.

37
Q

Where does gluconeogenesis occur?

A

Liver

38
Q

What factors should stimulate gluconeogenesis?

A

Cortisol, Glucagon.

39
Q

What is the rate limiting step for gluconeogenesis?

A

Fructose-1,6- bisphosphatase

40
Q

Relate 1-6-bisphosphatase with ATP

A

High levels of ATP means glucose can be used by other parts of the body so gluconeogenesis can occur.

High levels of AMP mean energy is needed and gluconeogenesis is inhibited.

41
Q

Where is glucose-6- phosphatase located?

A

In the ER of the lumen.

42
Q

What is the rate limiting step for glycogenesis?

A

glycogen synthase

43
Q

What sort of bonds does glycogen have?

A

alpha 1, 4 linkages keeps it moving 4ward.

alpha 1, 6(six) linkages branches in the mix

44
Q

What is the rate limiting step of glycogenolysis?

A

glycogen phosphorylase

45
Q

What is the role of glycogen phosphorylase?

A

Breaks down the alpha 1,4 linkages breaking down glycogen.

46
Q

Describe the pentose phosphate pathway:

A

Occurs in the cytoplasm of all cells.

1. Production of ribose sugar and NADPH.

47
Q

What is the rate limiting step of PPP?

A

glucose-6-phosphate dehydrogenase

MCAT Self Study (53 decks)

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