Question

1. How are the acetyl groups on acetyl CoA transported out of the mitochondria?

a. As HMG-CoA

b. As lactic acid

c. As citrate

d. As an acyl CoA

e. As oxaloacetate

2. Which is not a characteristic feature of LDL particles;

a. They contain cholesterol esters

b. They are coated with apoprotein B48

c. They contain less Triglycerides than VLDLs

d. They bind to receptors on liver cells

e. All of these are characteristics of LDL

3. Which 2 steps in the urea cycle require ATP

a. Arginase and ornithine transcarbamoylase

b. Ornithine transcarbamoylase and argininosuccinate synthase

c. Arginionsuccinate lyase and arginionsuccinate synthase

d. Carbamoyl phosphate synthetase and argininosuccinate synthase

e. Arginionsuccinate lyase and carbamoylphosphate synthetase

Answer 1

1.As citrate

In the mitochondria the citrate synthase combines with the Acetyl CoA with the support of oxaloacetate and result in citrate through the pathway called tricarboxylate transport system. Thus Acetyl CoA is transported out of mitochondria to cytosol in the form of citrate.

2. b. They are coated with apoprotein B48

LDL contain less triglycerides and higher cholesterol. LDL receptors are present on the liver cells

3. d. Carbamoyl phosphate synthetase and argininosuccinate synthase

Carbamoyl phosphate synthetase catalyses the condensation of NH4 ions with CO2 to form Carbomyl phosphate. This step consumes 2ATP.

Argininosuccinate synthase condenses citrulline with aspartate to result in argino succinate. This step requires one ATP