B Tutorials #2 and #3

B.1 Tutorial #2

B.1.1 Question 1

Which of the following organelles has / have a double-layer membrane?

1. Nuclear envelope
2. ER sheet
3. Plasma membrane
4. Mitochondrion

B.1.1.1 Answer

The answer should be 1., 2., and 4. The answer can be found in the lecture slides!

B.1.2 Question 2

Where is the proton gradient established in the mitochondrion and the chloroplast?

B.1.2.1 Answer

In the mitochondrion, the proton gradient is established in the inter-membrane space of the mitochondrio (across the inner membrane of the mitochondrionn. This proton gradient is generated via the free energy from electrons (carried by NAD⁺ and FADH⁺).

In the chloroplast, the proton gradient is generated in the inter-thylakoid membrane space.

B.1.3 Question 3

Which of the four protein sequences is the best candidate for a transmembrane domain?

1. NRRRVCKCPRPVVKSGDKP
2. LSQNKPKAAEGLDTQRFSG
3. IWAPLAGTCGVLLLSLVI
4. SIMYFSHFVPVFLPAKPTT

B.1.3.1 Answer

The answer should be 3. it has positively-charged sequences at the beginning (i.e., signal sequence) followed by non-polar amino acids and negatively-charged amino acids in the end.

B.1.4 Question 4

Is the nucleoplasm (the interior of the nucleus or the space where the chromatin occupies) considered the lumen of the nucleus?

B.1.4.1 Answer

No. Refer to the lecture notes!

In the lecture slides, there is a region of white that surrounds the DNA. Hence, we can say that the topology of the nucleus is the same as the topology of the cytoplasm.

B.2 Tutorial #3