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Biochemistry > Chapter 16 > Flashcards

Chapter 16 Flashcards

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1
Q

What is the metabolite that links glycolysis and the citric acid cycle?

A

Pyruvate

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2
Q

Process in which cells consume O2 and produce CO2

A

cellular respiration

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3
Q

3 major stages of cellular respiration

A
  1. acetyl coA production
  2. acetyl coA oxidation
  3. electron transfer and oxidative phosphorylation
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4
Q

What molecule is required for the first step in the CAC?

A

acetyl coA

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5
Q

These types of molecules are not a permanent part of an enzyme’s structure, rather, they associate, fulfill a function and dissociate

A

Coenzymes aka cofactors

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6
Q

Advantages of multienzyme complexes

A
  • the short distance between catalytic sites allows the channeling of substrates from one catalytic site to another
  • this channeling minimizes side reactions
  • the regulation of activity of one subunit effects the entire complex
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7
Q

What is substrate channeling?

A

The passage of intermediates from one enzyme directly to another enzyme without release (no exposure to solvent)

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8
Q

Where do oxidative reactions occur in the cell?

A

In the mitochondria which contains all the enzymes, coenzyme and proteins needed to carry out oxidation

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9
Q

Citrate formed from acetyl-coA and oxaloacetate is oxidized to yield …?

A

CO2
NADH
FADH2
GTP or ATP

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10
Q

What step is the rate-limiting step of the CAC

A

Step one - citrate synthesis- acetyl coA and oxaloacetate to citrate. It is highly thermodynamically favorable - irreversible

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11
Q

What is the end goal of citrate synthesis?

A

to fully oxidize both carbons in citrate that came from pyruvate to CO2 and generate ATP and electrons (NADH and FADH2) to be used in oxidative phosphorylation

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12
Q

What are the two regulatory proteins in the PDH complex?

A

protein kinase
phosphoprotein phosphate

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13
Q

Pyruvate is oxidized into what by the PDH?

A

pyruvate gets oxidized into acetyl coA and CO2

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14
Q

where does CAC occur

A

mitochondrial matrix

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15
Q

What step in the CAC is a substrate-level phosphorylation

A

step 5. the conversion of succinyl coA to succinate, produces GTP

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16
Q

What step does the first oxidative decarboxylation occur?

A

Step 3. The redox reaction of isocitrate to alpha-ketoglutarate

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17
Q

Which enzyme in the CAC is directly associated with the ETC?

A

succinate dehydrogenase

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18
Q

What products of the CAC are fed into the ETC for the generation of ATP?

A

FADH and NADH

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19
Q

What is the coenzyme of E1 in PDH complex?

A

TPP (thiamine pyrophosphate)

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20
Q

What is the coenzyme of E2 in the PDH complex?

A

lipollysine

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21
Q

What is the coenzyme of E3 in the PDH complex?

22
Q

What two products are produced in the PDH complex?

Study These Flashcards
A

acetyl coA and NADH

23
Q

What steps are regulation points in the CAC?

Study These Flashcards
A

PDH, citrate synthase, isocitrate dehydrogenase, alpha-ketoglutarate dehydrogenase

  • regulated at highly thermodynamically favorable and irreversible steps
24
Q

What is the purpose of converting citrate to isocitrate?

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A

citrate (tertiary alc) is a poor substrate for oxidation but isocitrate (secondary alc) is a good substrate for oxidation

25
What enzyme converts pyruvate to acetyl coA
Pyruvate dehydrogenase complex
26
what enzyme converts acetylcoA and oxaloacetate to citrate
citrate synthase
27
what enzyme converts citrate to isocitrate
aconitase
28
what enzyme converts isocitrate to alpha-ketoglutarate
isocitrate dehydrogenase
29
what enzyme converts alpha-ketoglutarate to succinyl coA?
alpha-ketoglutarate dehydrogenase
30
what enzyme converts succinyl coA to succinate
succinyl coA synthetase
31
what enzyme converts succinate to fumarate
succinate dehydrogenase
32
what enzyme converts fumarate to malate
fumarase
33
what enzyme converts malate to oxaloacetate?
malate dehydrogenase
34
what is the purpose of converting alpha-ketoglutarate into succinyl-coA?
alpha-ketoglutarate lacks an alcohol for oxidation so a thioester is formed on coA that can be oxidized
35
All CO2 generated during the CAC is produced before _______ is made
succinyl-coA
36
What does it mean that citrate is "pro-chiral"
it is not chiral but has the potential to react to generate a chiral species can also react "stereospecifically" even though it is achiral
37
What is the purpose of converting succinyl coA to succinate?
This reaction produced GTP and creates succinate
38
What kinase converts GTP to ATP reversibly
Nucleoside Diphosphate kinase
39
What is the purpose of converting succinate to fumarate
succinate needs to be oxidized to an alkene (fumarate) since an alkene is needed to form malate in the correct stereochemistry in the next step
40
What molecule is a potent, competitive inhibitor of succinate dehydrogenase that blocks the CAC when added to mitochondria
Malonate, an analog of succinate
41
what is the purpose of converting fumarate to L-malate?
adding water across the pi bond of the alkene allows for oxidation to a ketone in the next step **addition of water is always ANTI and forms L-malate
42
Fumarate must be (cis/trans)? in order to be recognized by fumarase
fumarate must be in the TRANS configuration
43
What is the purpose of converting malate to oxaloacetate?
the oxidation regenerates oxaloacetate for citrate synthase
44
What are anaplerotic reactions?
chemical reactions that replenish intermediates
45
What is the most important anaplerotic reaction in mammalian liver, kidney and brown adipose tissue?
pyruvate carboxylase catalyzes the carboxylation of pyruvate by HCO3
46
Explain the induced fit of citrate synthase
two conformations conformational change occurs once oxaloacetate binds open conformation: no binding site for acetyl-coA closed conformation: binding of oxaloacetate creates a binding site for acetyl coA
47
What two molecules contain high-energy thioester bonds?
acetyl-coA and succinyl-coA
48
What coenzymes are used in all oxidative decarboxylation?
NAD+ and coA
49
What are the overall products of the CAC pathway?
NADH and ATP
50
How is the PDH complex regulated?
By phosphorylation of E1 and [ATP] when E1 is phosphorylated it is INactive when E1 is Dephosphorylated it is Active High [ATP] --> PDH phosphorylated (inactive) --> less acetyl coA Low [ATP] --> PDH DEphosphorylated (active) --> more acetyl-coA

Biochemistry (10 decks)

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