Biochemical Pathways Flashcards by Zach Visinoni

What is the difference between hexokinase and glucokinase?

Hexokinase is used for baseline metabolism of glucose in all cells.

Glucokinase is low affinity and is only used in the liver and pancreatic beta cells.

How well did you know this?

Not at all

Perfectly

What is the RLS of glycolysis?

What can influence this reaction (+, -)?

PFK 1: catalyze F1P conversion to F1,6P.

+ AMP
- citrate, ATP

How well did you know this?

Not at all

Perfectly

What is PFK2?

What influences it (+, -)?

PFK2 catalyzes the F1,6P to F2,6P conversion. F2,6P is positively feeds back on PFK1 and increases the rate of glycolysis.

+ insulin
- glucagon

How well did you know this?

Not at all

Perfectly

What does pyruvate kinase catalyze?

How influences it (+, -)?

PEP to pyruvate.

+ AMP
- ATP, citrate

How well did you know this?

Not at all

Perfectly

What is the RLS of the Krebs cycle?

What is the yield of the Krebs cycle?

Isocitrate dehydrogenase.

3 NADH, 1 FADH2, 2 CO2.

How well did you know this?

Not at all

Perfectly

What in which reactions is NADH, FADH2 and CO2 formed in the Krebs cycle?

NADH:

isocitrate to a-KG (CO2 also)
a-KG to succinylcholine-CoA (CO2 also)
malate to OAA

FADH2:
-succinate to fumarate

How well did you know this?

Not at all

Perfectly

Which complexes do NADH and FADH2 bind in the ETC, respectively?

NADH: complex I

FADH2: complex II

How well did you know this?

Not at all

Perfectly

What is unique about coenzymeQ?

It is the only component in the ETC that accepts electrons from NADH and FADH2.

How well did you know this?

Not at all

Perfectly

What is the overall pathway of electrons in the ETC?

Complex I + II —> CoQ —> complex III —> cytochrome C —> complex IV —> ATP synthase

How well did you know this?

Not at all

Perfectly

Which complexes in the ETC pump H+ into the intermembrane space?

Complex I, III and IV

How well did you know this?

Not at all

Perfectly

What inhibits complex I?

Rotenone

How well did you know this?

Not at all

Perfectly

What inhibits complex II?

Antimycin

How well did you know this?

Not at all

Perfectly

What inhibits complex III?

CN, CO

How well did you know this?

Not at all

Perfectly

What inhibits ATP synthase?

Oligomycin, uncoupling agents

How well did you know this?

Not at all

Perfectly

What is the outcome of the HMG shunt (PPP)?

Production of NADPH from G6P

How well did you know this?

Not at all

Perfectly

What is the process of reducing glutathione?

NADPH produced in the PPP is used to reduce glutathione. That means that NADP+ is reduced to NADPH in the PPP, and is then oxidized to produce reduced glutathione.

What are oxidant stressors that may trigger a crisis in a patient with G6PD deficiency?

Sulfa drugs
Primaquine
Infection
Nitrofurantoin
Favs beans

“SPIN-F”

What are the histologic all hallmarks of G6PD deficiency?

Heinz bodies and “bite cells”

What is the major overview of the urea cycle?

Protein —> NH3 —> urea —> urinate it out

Where does the urea cycle occur? Which reactions occur there?

In the mitochondria and cytoplasm.

Mitochondria:
NH3 + ornithine —> carbamoyl phosphate (CPS1) —> citrulline

Cytosol:
Citrulline —> arginosuccinate —> arginine —> ornithine + urea

What is the main disease that can result from problems in the urea cycle?

Inheritance:
Lab changes: (5)
Symptoms:
Treatment:

Ornithine transcarbamoyltransferase deficiency

Inheritance: XLR

Lab changes: low ornithine transcarbomylase, low citrulline, high carbamoyl phosphate, high orotic acid, high ammonia.

Symptoms: asterixis, cerebral edema.

Treatment: decrease dietary protein intake.

Which FAs are essential?

PUFAs

Omega-6: linoleic acid
Omega-3: alpha-linoleic acid (1st), EPA (eico) and DHA (doco).

What is the RLS of the urea cycle?

CPS1

What is the problem in terns of location of FAs?

Acetyl-CoA is made in the mitochondria, but FA synthesis occurs in the cytosol. Thus, it must be converted to citrate first.

In FA synthesis, which molecule crosses the mitochondria into the cytosol?

Citrate

What is the RLS in FA synthesis? What is the reaction? What cofactor(s) is required?

Acetyl-CoA carboxylase; Acetyl-CoA —> Malonyl-CoA. CO2 and biotin.

What + FA synthesis? What - it?

+ insulin, citrate - glucagon, palmitoyl-CoA

Where does beta-oxidation occur?

Mitochondria, thus FAs must be moved from the cytosol back into the mitochondria via carnitine.

How many carbons are in short/mediumCFAs? LCFAs VLCFAs How do they get into the mitochondria?

S/MCFAs: 2-12; diffuse freely into the mitochondria. LCFAs: 12-20; carnitine shuttle. VLCFAs: >20; require peroxisime oxidation.

What is the pathway of beta-oxidation overall? Where does it occur?

Cytoplasm: FA —> FA CoA (via FA CoA synthase) —> Mitochondial membrane: FA CoA —> FA carnitine (via CAT1) Mitochondria: FA carnitine —> fatty acyl CoA (via CAT2) —> Acetyl CoA (via FA CoA dehydrogenase)

What is the RLS in beta oxidation?

CAT1

What inhibits beta oxidation? Where does it occur?

Malonyl CoA inhibits beta oxidation; CAT1 in the mitochondrial membrane.

What are the major features of Systemic Primary Carnitine Deficiency?

Hypoketotic hypoglycemia; patients cannot move fatty acyl CoA into the mitochondrial membrane.

What are the features of Myopathic CAT2 Deficiency?

Myoglobinuria, rhabdomyolysis (elevated CK), hypotonia, increased TAGs in muscle.

What are features of Medium Chain FA Dehydration Deficiency? What is the treatment?

Non-ketotic hypoglycemia, hepatic dysfunction, elevated ammonia. Avoid fasting and eat a carb-rich diet.