biochem b7 practice questions

Where does fatty acid activation occur?

Cytosol

Which enzyme activates fatty acids to form acyl-CoA?

Thiokinase / acyl-CoA synthetase

What molecule is required to activate a fatty acid?

ATP

What is the purpose of the carnitine shuttle?

Transport long-chain acyl-CoA into mitochondria

Which enzyme regulates entry of fatty acids into mitochondria?

CPT1

What is produced in the first oxidation step of β-oxidation?

FADH₂

Enoyl-CoA hydratase performs which reaction?

Adds water across the double bond

Second oxidation step of β-oxidation uses which cofactor?

NAD⁺

Thiolase cleaves β-ketoacyl-CoA to produce:

Acetyl-CoA + shortened acyl-CoA

End products of β-oxidation include:

Acetyl-CoA, NADH, FADH₂

β-oxidation occurs mainly in the:

Mitochondria

Tissues performing β-oxidation include:

Liver, muscle, heart

How many acetyl-CoA are produced from palmitate (16C)?

8

How many β-oxidation cycles occur for palmitate?

7

Odd-chain fatty acids ultimately produce which TCA intermediate?

Succinyl-CoA

Propionyl-CoA carboxylase requires which vitamin?

Biotin

Methylmalonyl-CoA mutase requires:

Vitamin B₁₂

Which enzyme is required for mono-unsaturated fatty acid oxidation?

Enoyl-CoA isomerase

Poly-unsaturated fatty acids require which additional enzyme?

2,4-dienoyl-CoA reductase

β-oxidation of C20–C26 fatty acids occurs mainly in:

Peroxisomes

Where does fatty acid synthesis occur?

Cytosol

Which tissues perform the majority of fatty acid synthesis?

Liver and adipose tissue

What is the precursor molecule required for fatty acid synthesis?

Acetyl-CoA

Which molecule provides reducing power for fatty acid synthesis?

NADPH

What enzyme performs the committed/regulated step in FA synthesis?

Acetyl-CoA Carboxylase (ACC)

Which cofactor is required by ACC?

Biotin

Which product is formed by ACC?

Malonyl-CoA

What activates ACC?

Insulin

What inhibits ACC?

Palmitoyl-CoA

Malonyl-CoA inhibits:

CPT-1

Fatty acid synthase requires which carrier protein?

ACP

Fatty acid synthesis elongates the chain by how many carbons per cycle?

2

What is the final product of standard FA synthesis?

Palmitate

The first step of elongation (condensation) releases:

CO₂

Which step uses NADPH in the FAS cycle?

Reduction steps

Which enzyme forms malonyl-ACP?

Malonyl transferase

Cytosolic acetyl-CoA is derived from:

Citrate shuttle

Animals lack desaturases that introduce double bonds beyond which carbon?

Δ9

Which fatty acids are essential because humans cannot synthesize them?

Omega-3 and Omega-6

Where does fatty acid elongation beyond 16 carbons primarily occur?

Smooth ER

what is cholesterol made of?

acetyl-coA

cholesterol synthesis step 1

HMG-CoA

cholesterol synthesis step 2

mevalonate

cholesterol synthesis step 3

isoprenoid precursor isopentenyl-pyrophosphae (IPP)

cholesterol synthesis step 4

condensation to squalene 

cholesterol synthesis step 5

cyclization of squalene 

cholesterol synthesis step 6

remodeling of lanosterol to make cholesterol

what is the precursor to all polyisoprenoid lipids?

IPP

where is LCAT found?

in the blood

where is ACAT found?

cellular areas

what is the function of bile?

fat digestion/absorption and excretes excess cholesterol

what is the rate limiting and committed step of cholesterol synthesis?

conversion of HMG-CoA to mevalonate by HMG-CoA reductase

what do the statin class of drugs target?

inhibits HMG-CoA reductase

function of SREP2?

regulates the transcription of HMG-CoA reductase

SREBPs overall function

maintains cholesterol homeostasis

SCAP

cleavage activating protein

SRE

serum response element

what is acetyl-coa made of?

pyruvate

cholesterol esterase function

breaks down cholesterol esters into free cholesterol and fatty acids

when intracellular cholesterol levels rise sreb2 activation—?

decreases

what is the function of N-acetylglutamate

it regulates the urea cycle and is neccesary for the urea cycle to begin

what are the pyruvate end products?

glycine, alanine, serine, cysteine, threonine, and tryptophan

what are the end products of oxaloacetate?

asparagine and aspartate

what are the end products of fumarate?

phenylalanine, aspartate, and tyrosine

what are the end products of succinyl-coA

valine, isoleucine, threonine, methionine

what are the end products of a-ketoglutarate?

histidine, arginine, proline, glutamate/glutamine

what are the branched amino acids?

leucine, isoleucine, and valine

LDL

cholesterol carrier