Question

1.

A researcher is performing experiments on the synthesis of a membrane-bound protein (like a receptor protein). Where in the cell should he/she investigate?

	a.	The nucleus
	b.	The lysosome
	c.	The rough Endoplasmic reticulum
	d.	The smooth Endoplasmic reticulum 2. Amino acids contain 2 functional groups attached to the alpha carbon: amino (NH2) and ketone (C=O) groups. True False 3. During the rising phase of the action potential, gNa is lesser than gK, while in the falling phase gNa is greater than gK. True False

Answer 1

1. Synthesis of membrane bound proteins occurs in rough endoplasmic reticulum (RER).

Transcription of mRNA occurs in the nucleus from DNA in eukaryotes. This pre-mRNA undergoes post transcriptional processing to form mature mRNA. Translation of proteins takes place either in the ribosomes present in RER or in free ribosomes present in cytosol. Lysosomes contain enzymes that are involved in protein breakdown. Smooth endoplasmic reticulum is involved in synthesis of lipid and steroid hormones. It is also involved in detoxification of drugs.

Proteins that are synthesized on RER have an ER localization sequence. Membrane bound proteins are synthesized on ribosomes present on RER. These proteins are transported by vesicles to Golgi if they require Glycosylation. The proteins are transported to the membrane by membrane bound vesicle that fuses with the membrane to release these proteins.

Right answer is c. Rough endoplasmic reticulum.

2. Amino acids have two functional group- an amino group (NH2) and a carboxyl group (-COOH). The amino acid is an alpha amino acid if these group are attached to the alpha carbon atom, which the carbon next to the carboxyl group. If the amino group is attached to secondary carbon atom, then the amino acid is a beta amino acid. Similarly, there is gamma amino acid. All naturally occurring amino acid are alpha amino acid. The amino acids also have a functional R group. A keto group is also known as a carbonyl functional group where in carbon is double bonded to oxygen and two other R group. Carboxyl group are groups with carbon atom double bonded to oxygen and a hydroxyl group.

Hence, right answer is false.

3. At rest, the driving force is highest for sodium while in rising phase; driving force of K is highest. As K+ has higher driving force at rest that Na, gk (potassium conductance) is higher than gNa (sodium conductance). When there is rising phase of action potential (depolarization phase), there is opening of Na channels. This will lead to spiking of gNa. In falling phase (repolarization phase), there is a decrease in gNa and an increase in GK as K+ channels open due to repolarization of the membrane.

The right answer is false.