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Biochemistry > Midterm 2 study guide > Flashcards

Midterm 2 study guide Flashcards

1
Q

How is ATP used as a source of energy in cells

A

The hydrolysis of ATP to ADP and Phosphate releases energy, and this is a favorable reaction

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2
Q

What does “favorable” mean in terms of ΔG (aka: free energy)?

A

A reaction is favorable when ΔG is negative, meaning it is spontaneous

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3
Q

Explain the process of reaction coupling to ATP

A

The process where hydrolysis of ATP (A thermodynamically favorable, - ΔG, or spontaneous reaction) is coupled with a thermodynamically unfavorable reaction to lower ΔG

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4
Q

How does reaction coupling drive an unfavorable process or reaction?

A

Reaction coupling can make an overall process spontaneous by combining two reactions
As long as the products are more stable than the reactants overall

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5
Q

What are the 3 high energy phosphate compounds

A

ATP, 1,3 BPG and PEP

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6
Q

In general, what does it mean to have high “phosphotransfer” potential energy?

A

-Phosphotransfer potential energy is the standard free energy of hydrolysis

-It is a way to measure the tendency of an organic molecule to transfer a phosphoryl group to an acceptor molecule

-ATP > ADP > AMP

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7
Q

Name the two major electron carrier molecules in the cell

A

FAD and NAD+ = high reduction potential

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8
Q

The energy associated with electron carriers is reduction potential (ie: electron transfer potential). Explain how coupling to an electron carrier can drive an unfavorable reaction

A

Coupling with electron carriers like NAD⁺ and FAD enables energetically unfavorable reactions by providing a source of energy through electron transfer

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9
Q

How is glucose used as a fuel source in the body

A

Glucose is a vital fuel source for the body, providing quick and efficient energy. It can be broken down to produce ATP.
Complex carbs must be broken down to this monosaccharide to use as a fuel source

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10
Q
  • Where does Glycolysis occur in the cell?
A

The cytoplasm

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11
Q

Where is ATP consumed in glycolysis

A

Step 1, Step 3
Step 1: Glucose → G6P (Hexokinase)
Step 3: F6P → F 1,6 Bisphosphate (PFK)

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12
Q

Where is ATP synthesized in glycolysis

A

Step 7: BPG → 3PG (Phosphoglycerate kinase)
Step 10: Phosphoenolpyruvate (PEP)→ Pyruvate (Pyruvate kinase)

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13
Q
  • What are the options for pyruvate under anaerobic conditions?
A

If no O2 is present - glycolysis and anaerobic metabolism are the primary source of ATP

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14
Q

Which process provides the primary source of ATP if no oxygen is present?

A

Pyruvate is converted to lactate in the absence of O2
glycolysis

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15
Q

Where is the ATP produced in a cell if no oxygen is present?

A

ATP is produced in the cytosol

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16
Q

What metabolite (small molecule) is produced as a result of anaerobic metabolism?

A

Lactic acid

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17
Q
  • If oxygen is present, what does pyruvate do?
A

If oxygen is present, pyruvate is converted to acetyl CoA in the mitochondria → further oxidation

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18
Q
  • Where does pyruvate go when oxygen is present?
A

Mitochondria for the citric acid cycle

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19
Q
  • What molecule is pyruvate converted to when oxygen is present?
A

Acetyl CoA

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20
Q
  • Which tissues are likely to require aerobic metabolism on a regular basis?
A

All of them, but the brain and heart especially

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21
Q

Describe the Cori Cycle

A

Lactic acid is produced in the muscles during intense exercise/infection/disease (or under hypoxic/anaerobic conditions) and sent to the liver.
In the liver, that lactate is converted back to pyruvate and then to glucose (gluconeogenesis) which is sent back to the muscles or stored as glycogen.
Increase ATP or replenish glycogen stores in muscle

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22
Q

What is the purpose of the Cori Cycle?

A

Prevents lactic acidosis (excess accumulation of lactate) in muscle under anaerobic conditions
Reduce muscle fatigue and allow for sustained activity

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23
Q

Which tissues does the cori cycle involve?

A

Muscles
Liver tissue

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24
Q
  • What is the major regulatory enzyme in glycolysis?
A

PFK
Rate limiting

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25
Q

Which reaction does PFK catlyze

A

F6P–>FBP

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26
Q

In muscle, what activates PFK

A

Activated by AMP in the allosteric site. ATP low, AMP high, turns on glycolysis (hyperbolic curve)

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27
Q

In muscle, what inhibits PFK

A

ATP in allosteric site. ATP high shuts off glycolysis, AMP is low, sigmoidal curve.

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28
Q

In the liver, what activates PFK

A

F26BP in the allosteric site

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29
Q

In the liver, what inhibits PFK

A

ATP in the allosteric site

30
Q

What is the site of regulation in PFK

A

The allosteric site- ATP and AMP bind there. If ATP is high, AMP is low and glycolysis shuts down.
If ATP is low and AMP is high, glycolysis is on.

31
Q

What is the molecule that activates PFK in the liver

A

F26BP

32
Q

What is the enzyme that synthesizes F26BP and what does F26BP then go on to activat

A

PFK-2 (kinase) sinthasizes F26BP and F26BP goes on to activate PFK

33
Q

Why can’t the liver use AMP the way the muscles do to activate PFK?

A

Liver does not have AMP and ATP does not get low because it can combine 2 ADP to make more ATP so it needs a different mechanisms compared to muscles that are more sensitive to AMP/ATP levels

34
Q

How does phosphorylation impact activity of PFK2?

A

Phosphorylation inhibits the kinase domain and activates the phosphatase domain
converts F26BP back to F6P → shut down glycolysis

35
Q

What is the purpose of the pentose phosphate pathway

A

How organisms generate NADPH. NADPH is needed for maintain the structure of red blood cells, stroid synthesis, etc

36
Q

Where does the pentose phosphate pathway occur

A

the cytosol

37
Q

What molecules of glycolysis are made from ribose-5-phosphate

A

nucleotides needed for the reproductive system and mammary glands
- Part of the pentose phosphate pathway

38
Q

In gluconeogenesis, why can’t pyruvate be converted directly back to PEP

A

Irreversable step because of the difference in energy between PEP and pyruvate- pyruvate then goes on to the TCA cycle

39
Q

What molecule is made between pyruvate and PEP

A

ATP

40
Q

What is the relationship between glucose-6 phosphatase and glycogen levels?

A

Blood sugar low → glucose-6 phosphatase active & decrease glycogen levels

41
Q

What happens with gluconeogenesis when blood sugar levels are low

A

glucose 6 phosphatase activates and decreases glycogen levels, gucagon binds to GPCR and activates PKA.

42
Q

What is the role of glycogen phosphorylase? What state is it in when its on?

A

Glycogen phosphorylase breaks down glycogen.
When blood sugar is low, glycogen phosphorylase is active (R state)

43
Q

Describe glycogen phosphorylase when blood sugar is normal/high. What state is it in?

A

Glycogen phosphorylase is inactive (T state), not metabolizing glycogen

44
Q

What is the immediate product of glycogen metabolism

A

Glycogen–> G1P–> g6p

45
Q

Glycogen is converted to what molecule by Glycogen phosphorylase?

A

G1P

46
Q

While enzymes convert G1P to G6P?

A

Phosphoglucomutase

47
Q
  • How does Glycogen phosphorylase serve as a “glucose sensor” in the liver?
A

Low glucose levels = glucagon released = signals phosphorylase kinase to phosphorylate glycogen phosphorylase (GPb) = active state (GPa) converted glycogen to G1P

48
Q

What happens in the muscles when epinephrine is released?

A

epinephrine → bypass eating → breakdown glycogen into G6P by GP to start glycolysis and make ATP

49
Q

What happens in the liver when epinephrine is released?

A

glucagon release in response to low blood sugar → breakdown glycogen to G6P using GP → G6P converted to Glucose by G6P phosphatase → increase blood sugar

50
Q

General path of signal transduction

A

Hormone binds to GPCR→ triggers conformational change in G protein → alpha subunit binds to adenyl cyclase→ ATP converted to cAMP→ cAMP phosphorylates PKA→ PKA has many effects at a cellular level (altar metabolism, etc)

51
Q
  • Which protein is responsible for eliciting the cellular response at the end of signal transduction pathways?
A

PKA

52
Q

What are the 3 hormones discussed and their impacts

A

Epinephrine → flight or fight
Glucagon → low blood sugar
Insulin → high blood sugar (20 min after eating)

53
Q

What occurs in the liver as a result of glucagon release

A

Glycogen break down → Glycogen phosphorylase GPa
Gluconeogenesis → pyruvate to oxaloacetate
inhibit glycolysis

54
Q

What occurs in the muscle as a result of epinephrine release

A

epinephrine → bypass eating → breakdown glycogen into G6P by GP to start glycolysis and make ATP

55
Q

What occurs in the liver as a result of insulin release

A

Insulin → Liver → GLUTs to the surface of the membrane

56
Q

Where does the citric acid cycle occur

A

Mitochondiral matrix

57
Q

What does pyruvate dehydrogenase do

A

converte pyruvate to acetyl CoA

58
Q

What is the intermediate step between glycolysis and the citric acid cycl

A

pyruvate dehydrogenase

59
Q

What activates pyruvate dehydrogenase

A

ADP, pyruvate, CA, MG (Muscle contraction), Insulin (When blood glucose is high)

60
Q

What inhibits pyruvate dehydrogenase

A

ATP, ACOA, NADH, PDH kinase (Phosphorylates PDH)

61
Q

What does PDH kinase do to PDH

A

Photophosphoylation- turns it off

62
Q

What occurs when PDH kinase gets into the mitochondria?

A

It starts generation of ATP via interaction with oxaloacetate

63
Q

What activates PDH phosphate

A

Muscle contraction, insulin, ADP, pyruvate

64
Q

What occurs in the first step of CAC

A

Citrate synthase catalyzes the condensation of Acetyl CoA and oxaloacetate–>citrate

65
Q

How many NADH and FADH are produced per turn of the CAC

A

3 NADH 1 FADH2

66
Q

Where is FADH2 produced in the CAC

A

Step 6, succinate–> fumerate (succinate dehydrogenase)

67
Q

What does glucose need for transport

A

GLUT transport tunnels because it’s so large

68
Q

Where does the Majority of ATP synthesis occur

A

via oxidative phosphorylation in the mitochondria

69
Q
  • Trace the path of electrons from NADH through the chain to their end point in oxygen.
A

NADH→ complex 1→Coenzyme Q→Complex III→ Cytochrome C→Complex IV
Where oxygen is reduced to water (oxidative phosphorylation)

70
Q

*Which complexes in the chain are responsible for pumping protons/generating the gradient?

A

Complex I, III, and IV: pump protons from mitochondrial matrix → intermembrane space and generate and maintain H+ gradient

71
Q
  • Why is NADH a more valuable electron carrier for ATP synthesis?
A

Because it donates its electrons earlier in the ETC (complex I) → allows more protons to be pumped across membrane → more ATP molecules compared to FADH2
FADH2 starts in complex II which does not pump H+

72
Q

In ATP synthesis there are 3 steps (binding ADP/P, forming ATP and releasing ATP)
Which of these steps is dependent on the proton gradient?

A

The energy from the proton gradient drives the rotation of the enzymes rotor which facilitates the release of ATP.
Release of ATP = dependent on the proton gradient

Biochemistry (7 decks)

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