M&R Quiz - Week3

What does the 'G' in GPCRs stand for?

• Gamma nucleotide-binding

• Guanine nucleotide-binding

• Gated

  nucleotide-binding

• Gas

  nucleotide-binding

Answer explanation

G protein‐coupled receptors comprise a large class of proteins that regulate many physiological functions such as sight, taste, smell, neurotransmission, cardiac output, and pain perception. In response to ligand binding, GPCRs activate heterotrimeric guanine nucleotide binding proteins (G proteins).

G proteins are 'heterotrimeric'

and consist of three distinct subunits

termed alpha, beta, and ________

• Gamma

• Theta

• Delta

• Omega

Answer explanation

Heterotrimeric G-proteins are composed of three distinct subunits (α, β, and γ).

There are many different α, β, and γ subunits, allowing a bewildering number of G-protein permutations.

Which two G protein subunits are said to

'bind tightly to each other and function as a single unit'?

(Choose two answers)

• Alpha

• Beta

• Gamma

• Delta

Answer explanation

The Beta and Gamma subunits are tightly associated and can be regarded as one functional unit.

Which of the following is an action of acetylcholine? (one answer)

• Increased

  blood pressure

• Decreased in salivary and gastric acid secretions

• Tachycardia

• Reduction in cardiac output

Answer explanation

Effects of ACo also known as cholinergic effects are: SLUD

Salivation = abnormally abundance flow of saliva

Lacrimation = increases secretion of tears

Urination = Inability to hold urine in the bladder due to loss of voluntary control over the urinary sphincters

Defecation = abnormal discharging of faeces

+ slow HR, flushing, Low BP, Breathing difficulty, sweating

TRUE about Monomeric G proteins:

(2 answers)

• Have 3 subunits: Alpha, Beta, Gamma

• Are NOT directly activated by GPCRs

• Are activated by G protein-coupled receptors

• Are small GTPases

Answer explanation

Monomeric G-proteins,

also referred to as small GTPases,

function as biological hubs being activated by extracellular stimuli and regulate downstream signalling events,

which results in different cellular responses.