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MCAT Biochem > TCA > Flashcards

TCA Flashcards

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MCAT flashcards
1
Q

H2O moves out of what part of the loop of henel

A

descending, as go deeper into the medulla osmolarity gets greater so water leaves to dilute

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2
Q

what hormone do alcohol and caffeine affect?

A

inhibit ADH —> aquaporin in collecting duct

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3
Q

why does glucokinase have a higher km than hexokinase

A

want to ensure that other parts of the body gets the first crack at the glucose

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4
Q

what differences are there in the feedback mechanisms of glucokinase and hexokinase

A
  • glucokinase is indices by insulin, hexokinase is not

- hexokinase is inhibited by excess G6P, glucokinase is not

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5
Q

the rate-limiting step of glycolysis

A

PFK1. ( catalyze fructose 6-p —-> fructose 1,6 bisp)

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6
Q

PCT vs DCT

A

PCT- right after the Bowen capsule where aa, glucose, vitamins, salts, h2o are reabsorbed
- concentration and ph of filtrate through the kidney

DCT- after the loop of henel, this is where aldosterone can have an impact- reabsorb sodium and water
- concentration and ph of urine

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7
Q

pyruvate has 3 fates

A

Oxaloacetate, lactic acid, acetyl CoA

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8
Q

fermentation

A

reduce pyruvate to lactic acid in order to oxidize NADH —> NAD+

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9
Q

pyruvate decarboxylation

A

right after glycolysis, in mito matrix

- pyruvate is oxidized to CO2, NAD+ is reduced and acetyl-CoA is produced

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10
Q

what enzyme pyruvate —-> acetyl-CoA

A

pyruvate dehydrogenase complex (PDH)

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11
Q

what activates PDH

A

insulin

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12
Q

what inhibits PDH

A

NADH and its product acetyl CoA

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13
Q

what’s important in PDH complex

A

B1, lipoic acid, Mg2+, pyrophosphate, FAD, NAD+

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14
Q

the main goal of TCA

A

to oxidize acetyl CoA to Co2 and H2O while reducing NAD+ and FAD

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15
Q

is PDH rxn spontaneous

A

yes very

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16
Q

how is CoA bonded to the acetyl group

A

thioester bond - creates a huge amount of energy when broken

17
Q

can alcohol get converted to acetyl CoA?

A

yes, by alcohol dehydrogenase BUT NADH build-ups up which inhibits TCA, therefore, a lot of the acetyl coa made from alcohol gets converted to FA

18
Q

synthases vs synthetases

A

with “e” needs energy input

  • both form new covalent bonds
19
Q

rate limiting step of TCA

A

isocitrate dehydrogenase

  • and first step when NADH is produced and CO2 is lost
20
Q

what steps reduce NAD+ and lose CO2

A

step 3 and 4

  • iso–> keto (rate lim)
  • keto- succinyl-coA
21
Q

what step reduces FAD

A

step 6 (succinate to fumigate) y succinate dehydrogenase

22
Q

what step generates ATP and why/how?

A

succinyl-CoA—> succinate + CoA-SH

bc the high energy thioester bond is hydrolyzed -RELEASES a shit ton of energy - enough to couple with GDP–> GTP

23
Q

whats the last step that reduces another NAD but no Co2 is produced?

A

step 8 (malate –> oxaloacetate + NADH)

  • enzyme is malate dehydrogenase ( the same as the aspartate-malate shuttle= 2.5 ATP)
24
Q

how to remember the order of TCA

A

Please Can I….. keep selling seashell for money, officer?

25
Q

how is the PDH regulated?

A

gets phosphorylated (kinase) to inactive PDH (too much energy- please stop) P in Please for Phosphorylate

gets dephosphorylated to reactive PDH

26
Q

3 control points of TCA

A
  1. citrate synthase - ATP, succinyl-coa and isocitrate, and NADH inhibit
  2. isocitrate dehydrogenase- ATP, NADH inhibit
  3. a-ketoglutarate dehydrogenase–> ATP, NADH and succinyl-Coa inhibit

these are steps 1, 3, 4

step 2 is just the isomerization of citrate to isocitrate

27
Q

what kind of reduction potencial does oxygen have at the end of the ETC

A

the highest

28
Q

how many H+ gets pumped by each complex in ETC

A

4, 0, 4, 2 - total of 10

29
Q

the glycerol from FA can get converted to what?

A

DHAP as seen in the glycerol 3-p shuttle system

  • this shuttle system produced only 1.5 ATP bc NADH turns into FADH2
30
Q

Fo vs F1 portion of ATP synthase

A

F0= ion channel ( as H+ flow down their gradient -chemical energy is harness and used to make ATP)

F1= utilizes this energy to create ATP

31
Q

where does high ADP activate ATP production

A

only one step!! isocitrate dehydrogenase (rate-limiting step)

MCAT Biochem (1 decks)

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