Question

1. The insulin receptor is:

A. a metabolite receptor

B. a receptor tyrosine kinase.

C. a GPCR

D. a gasotransmitter

E. a second messenger

2. Which of the following reactions requires a Vitamin B12 cofactor?

A. beta-oxidation of 18:0

B. beta-oxidation of (18:1 delta 9)

C. beta-oxidation of (16:2 delta 9 delta 12)

D. complete oxidation of (19:0)

E. all of these require Vitamin B12

3. Metabolite receptors bind to ___________________.

A. second messengers

B. DNA

C. GPCRs

D. Protein Kinase A

E. All of the above is true.

4. For every starting molecule of glucose, how many NTPs are made directly in the Citric Acid Cycle (not including any ATP made in the ETC)?

Answer 1

(CORRECT ANSWER) (OPTION B)

(EXPLANATION) Insulin receptor (IR) belongs to the class of tyrosine kinase receptors. It is a transmembrane receptor. It has a major role to play in the regulation of glucose levels in the body, any perturbation in this may lead to diabetes, cancer.

(EXPLANATION FOR INCORRECT ANSWER) (OPTION A) Metabolite receptors response to the metabolic demands of cells. They are in charge of the release of metabolic hormones.

(EXPLANATION FOR INCORRECT ANSWER) (OPTION C) G protein-coupled receptors (GPCRs) are heptahelical receptors that are found only in eukaryotes. As the name suggest, they interact with the G-proteins embedded in the plasma membrane which leads to a conformation change thereby activating other downstream molecules.

(EXPLANATION FOR INCORRECT ANSWER) (OPTION D) Gastrotransmitters include signalling molecules that are gasous in nature. The molecules could be endogenous or exogenous to the body of the organism and leads to the induction of physiological or biochemical changes . Many but not all gaseous signalling molecules are included in this.

Example of gaseous signalling molecules - Oxygen, carbon-dioxide, carbon-monoxide, etc.

(EXPLANATION FOR INCORRECT ANSWER) (OPTION E) Second messengers are signalling molecules that are released as response to the extracellular signalling molecules. They are intracellular in nature and function to accelerate physiological changes such as proliferation, differentiation, apoptosis, etc at cellular level. They can be of three types - hydrophobic, hydrophilic and gaseous.

Examples of Second messengers - cyclic AMP, cyclic GMP, Calcium, etc.

Examples of First messengers - epinephrine, serotonin, etc.