Cell Bio: Organelles (Week 1)

Question 1

What must be present on a protein in order to gain entry into the nucleus?

Answer 1

Nuclear localization signal

• is 4-8 a.a. long; contains arginine, lysine, proline

Question 2

What two CDK/cyclin pairs are responsible for G1–> S?

Answer 2

1. Cyclin D + CDK4 (phosphorylates RB–> frees E2F, allowing transcription of elements needed for synthesis)
2. Cyclin E + CDK2 (allows progression through G1/S checkpoint)

Question 3

What two CDK/cyclin pairs are needed for progression from G2–> M?

Answer 3

1. Cyclin A + CDK2 –> mitotic prophase

2. Cyclin B + CDK1–> breakdown of the nuclear envelope

Question 4

What molecule added to golgi directs proteins to the lysosomes?

Answer 4

Mannose-6-phosphate

Question 5

What dz results from deficiency of mannose-6 phosphate?

Answer 5

I-cell disease–> corneal clouding, coarse facies, restricted joint movmement; death by age 8
*lysosomes swell with undigested materials, b/c lysosomal enzymes cant make in into the lysosomes

Question 6

What residues are N-oligosaccharides added to in the golgi?

Answer 6

Asparagine

Question 7

What residues are O-oligosaccharides added to in the golgi?

Answer 7

Serine and threonine

Question 8

Other than beta oxidation of long chain fatty acids and brached amino acids, what other two important things occur in peroxisomes?

Answer 8

1. Synthesis of plasmalogens–> important phospholipids found in myelin
2. Oxidases and catalase for metabolizing ethanol and other toxic substances.

Question 9

What enzyme deficiency leads to inability to make mannose-6 phosphate in I-cell disease?

Answer 9

Phosphotranseferase–> required for mannose-6 phosphate production