2011 biochem

Question 1

Which of the following shows a variation in the level of its stores throughout the day and overnight and is responsible for supplying blood with glucose?

Answer 1

Liver

Question 2

Which amino acid deletion is responsible for cystic fibrosis?

Answer 2

Phenylalanine

Question 3

What is the most common sequence in the human genome?

Answer 3

Alu sequence

Question 4

Which of the following is the precursor for the amino acids aspartate and aspargine?

Answer 4

Oxaloacetate

Question 5

Which of the following processes will be inhibited if a drug that blocks sprecher’s shunt is administered?

Answer 5

Converting C24,6 to C22,6

Question 6

What is the product of the rate limiting step of cholesterol synthesis catalyzed by HMG-CoA reductase?

Answer 6

Mevalonate

Question 7

What is a consequence of a diet rich in trans fats?

Answer 7

Low LDL receptor function

Question 8

What stimulates gluconeogenesis?

Answer 8

Low levels of fructose-2,6-bisphosphate

Question 9

Which enzyme is responsible for extracting ammonia from glutamate in the liver?

Answer 9

Glutamate dehydrogenase

Question 10

What is an effect of the superoxide free radical?

Answer 10

Degrading the iron-sulfur centers

Question 11

Which enzyme catalyzes the rate limiting step of fatty acid synthesis?

Answer 11

Acetyl-CoA carboxylase

Question 12

A lysosomal enzyme lost its leader sequence as a result of a mutation that altered the sequence of its gene. Where will you find this enzyme after it is synthesized?

Answer 12

Cytoplasm

Question 13

What will contribute fluidity to the cytoplasmic membrane?

Answer 13

unsaturated fatty acids

Question 14

Which substrate’s usage for gluconeogenesis increases at first and then decreases during intermediate starvation?

Answer 14

Amino acids

Question 15

Which of the following vitamins is most likely to result in toxicity?

Answer 15

Vitamin A (any fat soluble vitamin)

Question 16

What is broken down in the intestine and then resynthesized following absorption?

Answer 16

Triglycerides

Question 17

Which of the following is essential for β-oxidation of odd-chain fatty acids?

Answer 17

Vitamin B12

Question 18

In which sub-cellular location are ketone bodies synthesized?

Answer 18

Mitochondria

Question 19

What molecule mediates the transfer of electrons from a 2 electron carrier to a 1 electron carrier?

Answer 19

FAD

Question 20

What are transcription factors?

Answer 20

Regulatory proteins

Question 21

A person has triacylglyceridemia but his apo-CII was normal. What should be investigated next?

Answer 21

Lipoprotein lipase

Question 22

What happens to the Ras protein in cancer?

Answer 22

It is permanently activated

Question 23

What is the objective of the non-oxidative stages of pentose phosphate pathway in rapidly proliferating cells?

Answer 23

The generation of ribose-5-phosphate

Question 24

What are enhancers and supressors?

Answer 24

DNA elements

Question 25

Which carbons in ddNTP don’t have hydroxyl groups?

Answer 25

2’,3’ deoxyribose

Question 26

What is the cause in HbS that leads to the sickle cell morphology in sickle-cell anemia?

Answer 26

Aggregation at Low oxygen tension

Question 27

Which amino acid is phosphorylated on proteins?

Answer 27

Serine

Question 28

Which of the following is inhibited upon administration of aa-tRNA analogs?

Answer 28

Elongation

Question 29

What leads to the formation of pyramidine dimers?

Answer 29

UV radiation

Question 30

Which amino acid is responsible for beta-turn in the structure of a protein?

Answer 30

Proline

Question 31

What is similar regarding isoenzymes?

Answer 31

They catalyze the same reaction

Question 32

Why does the liver express glucokinase?

Answer 32

To ensure rapid glucose uptake after a meal