G Proteins and Signal Transduction

What is the primary function of G proteins in cells?

• To act as molecular switches and transmit signals inside cells

• To synthesize proteins from amino acids

• To store genetic information

• To break down glucose for energy

Which nucleotide is bound to G proteins when they are in the 'on' state?

• ATP

• GTP

• GDP

• CTP

What happens to G proteins when they are bound to GDP?

• They are 'on'

• They are 'off'

• They are degraded

• They are phosphorylated

Which of the following is NOT a subunit of heteromeric G-protein complexes?

• Alpha (Gα)

• Beta (Gβ)

• Gamma (Gγ)

• Delta (Gδ)

What is the main difference between the two classes of G proteins?

• One class is found only in plants, the other in animals

• One class functions as monomeric small GTPases, the other as heteromeric complexes

• One class binds DNA, the other binds RNA

• One class is always active, the other is always inactive

Which type of receptor activates heterotrimeric G proteins within the cell?

• Ion channel receptors

• G-protein coupled receptors (GPCRs)

• Enzyme-linked receptors

• Nuclear receptors

What is the role of the beta and gamma subunits in heteromeric G-protein complexes?

• They form a stable dimeric complex known as the beta-gamma complex

• They hydrolyze ATP

• They bind to DNA

• They act as receptors for hormones

Why are G proteins classified as GTPases?

• Because they synthesize GTP

• Because they hydrolyze GTP to GDP

• Because they transport GTP across membranes

• Because they are only active in the presence of calcium

Which of the following best describes the primary function of G protein-coupled receptors (GPCRs) in cell signaling?

• They directly synthesize proteins.

• They transmit signals from hormones and neurotransmitters to trigger cellular responses.

• They store genetic information.

• They break down metabolic enzymes.

What is the main role of small GTPases in the cell?

• To act as large structural proteins

• To function as small molecular switches regulating various cellular processes

• To store energy in the form of ATP

• To degrade ribosomes