Formative Questions

Question 1

The removal of a peptide sequence from a protein as a form of signal is called

Answer 1

Proteolytic Cleavage

Question 2

The three basic parts of an operon are the

Answer 2

Promoter, the operator, and two or more structural genes

Question 3

The following shows a partial sequence of events in the oxytocin signal signal transduction pathway in uterine smooth muscle cells:
Oxytocin > GPCR > G protein activation > … > … > increase in intracellular Ca2+ ion levels > Na+ ion channel opening.
How could this signal transduction pathway be switched off?

Answer 3

Degradation of Second Messengers: If second messengers (like inositol trisphosphate, IP3) are involved, enzymes can degrade these molecules, further diminishing the signal.

Question 4

Which superfamily does the nicotinic acetylcholine receptor belong to based on its structure?

Answer 4

Ligand-gated ion channel receptors

Question 5

Co-repressors are usually found in … systems, which tend to be found in … pathways

Answer 5

repressible; anabolic

Question 6

In which human tissues are beta-2 adrenoreceptors normally expressed in sufficient density to evoke a dilation in response to binding by adrenaline?

Answer 6

Smooth Muscle of Blood Vessels,
Bronchial Smooth Muscle,
Uterine Smooth Muscle,
Liver

Question 7

Which superfamily do the insulin receptors belong to based on their structure?

Answer 7

Kinase-linked receptors

Question 8

In bacterial cells, the concentration of cAMP is … correlated with the concentration of glucose, hence, glucose concentrations should … correlated with the amount of transcription in the lac operon (assuming that lactose is abundant)

Answer 8

inversely; be inversely

Question 9

How many peptide chains form a mature insulin

Answer 9

2

Question 10

What is an example of a steroidal hormone synthesised from cholesterol

Answer 10

Cortisol, sex hormones, vitamin D

Question 11

Which type of bond maintains the ring structure of hormones such as somastatin

Answer 11

Disulphide bond

Question 12

Signals that travel to distant cells through the circulatory system are

Answer 12

Hormones

Question 13

The presence of a stop signal on a protein usually means it is destined for

Answer 13

membrane of an organelle

Question 14

In comparison with structural genes in bacterial operons, genes that encode for stress responses in plants

Answer 14

are not coordinately regulated

Question 15

Which of the following enzymes converts cyclic adenosine monophosphate (cAMP) to adenosine monophosphate (AMP)

Answer 15

Phosphodieterase

Question 16

How many protein subunits compose nicotinic acetylcholine receptors

Answer 16

5

Question 17

Which would most likely be a gene under constitutive expression control

Answer 17

A gene that encodes for a portion of the ribosome

Question 18

What is the normal sequence for the release of insulin from pancreatic beta cells

Answer 18

• Increased blood glucose levels lead to glucose being taken up by pancreatic beta cells through the glucose transporter (GLUT2).
• Once inside the cell, glucose undergoes glycolysis and is metabolized, increasing ATP levels.
• Closure of K+ Channels, rise in ATP causes this.
  This leads to a decrease in potassium ion efflux, causing membrane depolarization.
• Calcium Influx: The depolarization of the membrane opens voltage-gated calcium channels (Ca2+ channels), allowing calcium ions to flow into the beta cells.
• Insulin Granule Exocytosis: The influx of calcium triggers the exocytosis of insulin-containing secretory granules, leading to the release of insulin into the bloodstream.
• Insulin Action: Once released, insulin travels through the bloodstream to target tissues, where it promotes glucose uptake and regulates metabolism.

Question 19

When proteins are modified after mRNA translation, this is called

Answer 19

Post-translation modification

Question 20

What is normally exchanged following G-protein coupled receptor activation

Answer 20

GDP for GTP

Question 21

What is the lac operon?

Answer 21

The lac operon of E. coli contains genes involved in lactose metabolism. It’s expressed only when lactose is present and glucose is absent.