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MCAT Miscellaneous > Review 8 > Flashcards

Review 8 Flashcards

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MCAT flashcards
1
Q

Metabolism Rate-Limiting Enzymes

A
  1. Glycolysis - Phosphofructokinase-1
  2. Fermentation - Lactate dehydrogenase
  3. Glycogenesis - Glycogen Synthase
  4. Glycogenolysis - Glycogen phosphorylase
  5. Gluconeogenesis - Fructose-1,6-bisphosphatase
  6. Pentose Phosphate Pathway - Glucose-6-phosphate dehydrogenase
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2
Q

Functions of Hexokinase

A
  1. Phosphorylates glucose preventing it from leaving the cell via transporters.
  2. Glucose 6 phosphate can be stored as glycogen.
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3
Q

Regulation inhibitor of Hexokinase

A

Glucose-6-phosphate

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4
Q

Regulation Inhibitor of Glucokinase

A

Insulin

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5
Q

Phosphofructokinase-1 Functions

A
  1. Phosphorylates Fructose 6 phosphate

2. Main control point for glycolysis, catalysis the rate-limiting irreversible step.

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6
Q

Phosphofructokinase-1 Inhibitor

A
  1. ATP

2. Citrate

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7
Q

Phosphofructokinase-1 Activator

A
  1. AMP
  2. Insulin
  3. Phosphofructokinase-2 activation even in the presence of sufficient ATP
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8
Q

Glyceraldehyde 3-phosphate dehydrogenase Function

A

Oxidation and addition of inorganic phosphate to glyceraldehyde-3-phosphate

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9
Q

Glyceraldehyde 3-phosphate dehydrogenase Important stuff

A

Substrate - Glyceraldehyde-3-phosphate

Products - NADH, 1,3-bisphosphoglycerate

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10
Q

3-Phosphoglycerate kinase

A
  1. Transfers phosphate from 1,3 bisphosphoglycerate to ADP producing ATP and 3-phosphoglycerate.
  2. Not dependent on oxygen
  3. Reversible
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11
Q

3-Phosphoglycerate kinase Important Stuff

A

Substrate Phosphorylation: ADP is directly phosphorylated to ATP using high energy intermediate.

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12
Q

Pyruvate Kinase function

A
  1. Substrate-level phosphorylation of ADP using the high-energy substrate phosphoenolpyruvate (PEP)
  2. Irreversible
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13
Q

Pyruvate Kinase Positive Regulator

A

Fructose 1,6 phosphate product of PFK-1

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14
Q

Dihydroxyacetone Phosphate function (DHAP)

A

It is used in hepatic and adipose tissue for glycerols.

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15
Q

1,3-Bisphosphoglycerate and PEP

A

Produce only ATP gained in

anaerobic respiration by substrate level phosphorylation

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16
Q

Glycogen storage

A
  1. Liver to maintain glucose levels in the blood

2. Skeletal muscle to provide energy for vigorous exercise

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17
Q

LEARN THE GRAPH FOR GLYCOGENESIS

A

Look at Al’s handout

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18
Q

Steps in Glycogenesis

A
  1. Glycogenin - Core protein
  2. Glucose: Glucose-6-phosphate is converted to glucose-1-phosphate
  3. Glycogen synthase integrates Glucose-1-phosphate into glycogen
  4. Branching adds the alpha 1,6 linked branch
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19
Q

Glycogen synthase function, inhibitor, and activator

A
  1. Integrates glucose-1-phosphate into glycogen
  2. Rate limiting enzyme for glycogen synthesis
  3. Stimulated by Glucose-6-phosphate and insulin
  4. Inhibited by Glucagon and epinephrine
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20
Q

Glycogenolysis DIAGRAM/GRAPH

A

Learn this STUFF

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21
Q

Glycogen Phosphorylase

A
  1. Rate limiting enzyme breaks down glycogen with inorganic phosphate not water.
  2. Breaks 1,4 glycosidic linkage NOT 1,6
22
Q

Glycogen Phosphorylase Inhibitor and Activator

A
  1. Activator - Glucagon, AMP, and Epinephrine

2. Inhibitor - ATP

23
Q

Debranching Enzyme

A
  1. Breaks 1, 6 linkage

2. Glucose-1-phosphate is then converted to glucose-6-phosphate to enter glycolysis.

24
Q

LOOK AT GLUCONEOGENESIS GRAPH

A

Look online or somewhere

25
Q

Gluconeogenesis Facts

A
  1. Activator - Glucagon, epinephrine, growth hormone
  2. Inhibitor - Insulin
  3. Glycogen stores last 12-24 hours.
26
Q

Gluconeogenesis Substrates and NOT USED

A
  1. Glycerol from fat
  2. Lactate from Anaerobic glycolysis
  3. Certain amino acids except for Leucine and Lysine
  4. DO NOT USE Fatty acids and acetyl-coA
27
Q

Ketogenic Amino acids

A
  1. Leucine

2. Lysine

28
Q

Gluconeogenic Amino acids

A

All except lysine and leucine

29
Q

Pyruvate Carboxylase

A
  1. Shifts pyruvate to gluconeogenesis
  2. Produces oxaloacetate(OAA) from pyruvate which can enter the citric acid cycle or produce glucose.
  3. Oxaloacetate is reduced to malate which can leave the mitochondria.
  4. fatty acids produce Acetyl-CoA which power the cell and INHIBIT PDH and ACTIVATES pyruvate carboxylase.
30
Q

PEP carboxykinase (PEPCK)

A
  1. Converts OAA to PEP and requires GTP.

2. Activators - glucagon and cortisol

31
Q

Fructo 1,6-biphosphotase

A
  1. The reverse of PFK1 by hydrolyzing phosphate to produce fructose 6-phosphate.
  2. Activators - ATP and glucagon
  3. Inhibitors - AMP, fructose2,6-bisphosphate, and Insulin
  4. Rate limiting enzyme in gluconeogenesis
32
Q

Gluco-6-phosphatase

A
  1. converts Glu-6-P to Glucose allowing Glucose to be transported out of the cell
  2. Located in the lumen of ER.
  3. Circumvent - hexokinase and glucokinase
  4. NOT present in skeletal muscles; skeletal muscles cannot release glucose into blood.
33
Q

Other important gluconeogenesis notes

A
  1. Dependent on fatty acid oxidation for energy which requires the breakdown of triglycerides by the liver.
  2. Lactic acid produced by aerobic respiration must be converted back to pyruvate by the liver and pyruvate can be converted back to glucose.
  3. Acetyl-CoA can be converted into ketones which can be used for energy and transported in the blood.
34
Q

LEARN THE PENTOSE PHOSPHATE PATHWAY

A

Look it up

35
Q

Pentose Phosphate Regulation

A
  1. Activator - NADP+ and Insulin

2. Inhibitor - NADPH

36
Q

Pentose Phosphate Pathway notes

A
  1. Occurs in the cytoplasm.
  2. Produced NADPH and creates ribose 5-phosphate
  3. Oxidation of Glucose 6-phosphate to 6-phosphogluconate is irreversible and rate-limiting.
  4. Intermediates can be exchanged between glycolysis and PPP.
37
Q

NADPH functions

A
  1. NADPH acts as electron donor in biochemical reactions (fatty acids, cholesterol).
  2. Production of bleach for immune functions.
  3. Protects against free radicals by producing glutathione.
  4. NADH feeds the electron transport chain.
38
Q

How do products of glycolysis pass to the mitochondria?

A
  1. Facilitated diffusion.
  2. NADH requires 1 ATP to be transported into the matrix.
  3. CoA-SH has a cysteine (thiol group) which forms a covalent bond with acetyl-group forming a thioester.
  4. Thioester contains an S instead of an O in the OR group of a typical ester.
39
Q

Kreb’s Cycle Caveat

A
  1. Oxygen is not directly required, the pathway will not occur anaerobically because of the accumulation of NADH and FADH2 which will inhibit the cycle.
  2. Each turn produces 1ATP, 3NADH and 1 FADH2
40
Q

Kreb’s Cycle Acronym

A

Please, Can I Keep Selling Seashells For Money, Officer

41
Q

Kreb’s Cycle

A

Pyruvate (Acetyl-coA) -> Citrate -> Isocitrate -> Alpha-ketoglutarate -> Succinyl-CoA -> Succinate -> Fumarate -> Malate -> Oxaloacetate

42
Q

Citrate formation

A
  1. Acetyl-CoA transfers two carbons from pyruvate to a 4-carbon.
  2. Citrate synthase catalyzed.
43
Q

Citrate isomerization to Isocitrate

A
  1. DEHYDRATION resulting in ELIMINATION followed by HYDROLYSIS causing ADDITION of water.
  2. Aconitase catalyzed
44
Q

Alpha Ketoglutarate formation

A
  1. Oxidation by Isocitrate Dehydrogenase followed by decarboxylation
  2. Rate limiting step of citric acid cycle
  3. First DECARBOXYLATION and then production of CO2.
45
Q

Succinyl-CoA Formation

A
  1. Catalyzed by Alpha-ketoglutarate dehydrogenase complex.

2. Decarboxylation resulting in the formation of CO2 and NADH.

46
Q

Succinate formation

A

1 . HYDROLYSIS of the thioester bond on succinyl-CoA yields succinate and CoA–SH.

  1. GTP is produced.
  2. Succinyl-CoA synthetase catalyzed.
47
Q

Fumarate Formation

A
  1. Doesn’t take place in Matrix, takes place on the inner membrane.
  2. Succinate is oxidized to yield fumarate by Succinate Dehydrogenase.
  3. FAD is reduced to FADH2
48
Q

Malate Formation

A

Fumarase causes HYDROLYSIS of alkene in fumarate.

49
Q

Oxaloacetate formation ANEW

A
  1. Malate dehydrogenase causes OXIDATION of malate to oxaloacetate.
  2. NAD+ is reduced to NADH.
50
Q

LOOK AT KREB’s CYCLE DIAGRAM

A

CONFIRM ALL OF THIS

51
Q

Electron Transport Chain Notes

A
  1. Electrons are passed from Complex 1 to Q to complex 2 to complex 3 to cytochrome C to Complex 4.
  2. Ultimately O2 accepts becoming substrate level and forms H2O.
  3. Complex 1 oxidizes NADH and becomes reduced. Complex 1 becomes oxidized by Q and passes 2 hydrogens into the IMS while Q becomes reduced.

MCAT Miscellaneous (17 decks)

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