Communication and Signalling

Question 1

What do multicellular organisms use to signal between cells?

Answer 1

Extracellular signalling molecules

Question 2

Examples of extracellular signalling molecules?

Answer 2

Steroid hormones, peptide hormones and neurotransmitters

Question 3

What are receptor molecules of target cells?

Answer 3

proteins with a binding site for a specific signal molecule

Question 4

What does binding to a receptor molecule do?

Answer 4

binding changes the conformation of the receptor, which initiates a response within the cell

Question 5

What do hydrophobic signalling molecules do?

Answer 5

diffuse directly through the phospholipid bilayer and bind to intracellular receptors

Question 6

What are the receptors for hydrophobic signalling molecules?

Answer 6

transcription factors

Question 7

What are transcription factors?

Answer 7

proteins that when bound to DNA can stimulate or inhibit initiation of transcription

Question 8

Examples of hydrophobic signalling molecules?

Answer 8

The steroid hormones oestrogen and testosterone

Question 9

Where do steroid hormones bind?

Answer 9

specific receptors in the cytosol or the nucleus

Question 10

What does the Hormone-Receptor complex do once in the nucleus?

Answer 10

it binds to specific sites on DNA and affects gene expression

Question 11

What does the hormone-receptor complex bind to?

Answer 11

specific DNA sequences called hormone response elements (HREs)

Question 12

What does binding at HRE’s influence?

Answer 12

Influences the rate of transcription

Question 13

What do hydrophillic signalling molecules do?

Answer 13

Bind to transmembrane receptors and do not enter the cytosol

Question 14

How do transmembrane receptors act as signal transducers?

Answer 14

by converting the extracellular ligand binding event into intracellular signals, which alters the behaviour of the cell

Question 15

Examples of hydrophillic extracellular signalling molecules?

Answer 15

Peptide hormones and neurotransmitters

Question 16

What are phosphorylation cascades?

Answer 16

Involve a series of events with one kinase activating the next in the sequence and so on

Question 17

What do phosphorylation cascades allow?

Answer 17

allow more than one intracellular signalling pathway to be activated

Question 18

What does the binding of the peptide hormone insulin to its receptor result in?

Answer 18

an intracellular signalling cascade that triggers recruitment of GLUT4 glucose transporter proteins to the cell membrane of fat and muscle cells

Question 19

What can diabetes mellitus be caused by?

Answer 19

failure to produce insulin (type 1) or loss of receptor function (type 2)

Question 20

Type 2 diabetes is generally associated with…

Answer 20

obesity

Question 21

What else triggers recruitment of GLUT 4?

Answer 21

Exercise

Question 22

What do G-proteins do?

Answer 22

G-proteins relay signals from activated receptors to target proteins such as enzymes and ion channels

Question 23

what does the binding of insulin to its receptor cause?

Answer 23

a conformational change that triggers phosphorylation of the receptor

Question 24

binding of insulin to its receptor causes a conformational change that triggers phosphorylation of the receptor. This starts _____

Answer 24

a phosphorylation cascade inside a cell, which eventually leads to GLUT4 containing vesicles being transported to the cell membrane

Question 25

What is resting membrane potential?

Answer 25

A state where there is no net flow of ions across the membrane

Question 26

What does the transmission of a nerve impulse require?

Answer 26

changes in the membrane potential of the neuron’s plasma membrane

Question 27

What is an action potential?

Answer 27

A wave of electrical excitation along a neuron’s plasma membrane

Question 28

How do neurotransmitters initiate a response?

Answer 28

by binding to their receptors at a synapse

Question 29

What are neurotransmitter receptors?

Answer 29

ligand-gated ion channels.

Question 30

What is depolarisation?

Answer 30

A change in the membrane
potential to a less negative value inside.

Question 31

What is the retina?

Answer 31

the area within the eye that detects light and contains two types of photoreceptor cells: rods and cones

Question 32

In animals the light-sensitive molecule retinal is combined with….

Answer 32

a membrane protein, opsin,
to form the photoreceptors of the eye

Question 33

Rods function in _____ _______ but do not allow _____ __________.

Answer 33

dim light, colour perception

Question 34

What are cones are responsible for?

Answer 34

colour vision and only function in bright light