Communication and signalling

Question 1

Multicellular organisms signal between cells using what?

Answer 1

Multicellular organisms signal between cells using extracellular signalling molecules

Question 2

what are steroid hormones and neurotransmitters an example of

Answer 2

Steroid hormones, peptide hormones, and neurotransmitters are examples of extracellular signalling molecules.

Question 3

what are Receptor molecules of target cells

Answer 3

Receptor molecules of target cells are proteins with a binding site for a specific signal molecule

Question 4

Binding changes the conformation of the
receptor which initiates what

Answer 4

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

Question 5

Signalling molecules may have different effects on different target cell types due to what

Answer 5

Signalling molecules may have different effects on different target cell types due to differences in the intracellular signalling molecules and pathways that are involved.

Question 6

Different cell types produce specific signals that can only be detected and responded to by what type of cells

Answer 6

Different cell types produce specific signals that can only be detected and responded to by cells with the specific receptor

Question 7

In a multicellular organism, different cell types may show what

Answer 7

In a multicellular organism, different cell types may show a tissue-specific response to
the same signal

Question 8

what can hydrophobic signalling molecules do

Answer 8

Hydrophobic signalling molecules can diffuse
directly through the phospholipid bilayers of
membranes, and so bind to intracellular receptors

Question 9

The receptors for hydrophobic signalling molecules are what?

Answer 9

The receptors for hydrophobic signalling molecules are transcription factors

Question 10

what are transcription factors

Answer 10

Transcription factors are proteins that when
bound to DNA can either stimulate or inhibit
initiation of transcription.

Question 11

what are some examples of hydrophobic signalling molecules

Answer 11

The steroid hormones oestrogen and testosterone are examples of hydrophobic signalling molecules

Question 12

Steroid hormones bind to specific receptors in where?

Answer 12

Steroid hormones bind to specific receptors
in the cytosol or the nucleus

Question 13

The hormone-receptor complex moves to the
nucleus where it binds to what which does what?

Answer 13

The hormone-receptor complex moves to the
nucleus where it binds to specific sites on
DNA and affects gene expression

Question 14

The hormone-receptor complex binds to complex DNA sequences called what. what does this influence

Answer 14

The hormone-receptor complex binds to complex DNA sequences called hormone response elements (HREs). Binding at these
sites influences the rate of transcription, with
each steroid hormone affecting the gene
expression of many different genes.

Question 15

Binding of the peptide hormone insulin to its receptor results in an intracellular signalling cascade that triggers what?

Answer 15

Binding of the peptide hormone insulin to its receptor results in an intracellular signalling cascade that triggers recruitment of GLUT4 glucose transporter proteins to the cell membrane of fat and muscle cells

Question 16

Diabetes mellitus can be caused by what?

Answer 16

Diabetes mellitus can be caused by failure to
produce insulin (type 1) or loss of receptor
function (type 2)

Question 17

Exercise also triggers what, which can improve what

Answer 17

Exercise also triggers recruitment of GLUT4,
so can improve uptake of glucose to fat and muscle cells in subjects with type 2

Question 18

Binding of insulin to its receptor causes a conformational change that triggers phosphorylation of the receptor. what does this start

Answer 18

Binding of insulin to its receptor causes a conformational change that triggers phosphorylation of the receptor. This starts a
phosphorylation cascade inside the cell, which eventually leads to GLUT4-containing vesicles being transported to the cell
membrane.

Question 19

what is resting membrane potential

Answer 19

Resting membrane potential is a state where there is no net flow of ions across the membrane

Question 20

The transmission of a nerve impulse requires what?

Answer 20

The transmission of a nerve impulse requires changes in the membrane potential of the neuron’s plasma membrane

Question 21

What is an action potential

Answer 21

An action potential is a wave of electrical excitation along a neuron’s plasma membrane

Question 22

how do neurotransmitters initiate a response

Answer 22

Neurotransmitters initiate a response by binding to their receptors at a synapse

Question 23

what are Neurotransmitter receptors

Answer 23

Neurotransmitter receptors are ligand-gated ion channels.

Question 24

what is depolarisation

Answer 24

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

Question 25

Depolarisation of the plasma membrane as a result of the entry of positive ions triggers the what

Answer 25

Depolarisation of the plasma membrane as a result of the entry of positive ions triggers the opening of voltage-gated sodium channels, and further depolarisation occurs

Question 26

Inactivation of the sodium channels and the opening of potassium does what

Answer 26

Inactivation of the sodium channels and the opening of potassium channels restores the resting membrane potential

Question 27

Depolarisation of a patch of membrane causes neighbouring regions of membrane to do what

Answer 27

Depolarisation of a patch of membrane causes neighbouring regions of membrane to depolarise and go through the same cycle, as
adjacent voltage-gated sodium channels are
opened

Question 28

When the action potential reaches the end of
the neuron, what does it cause

Answer 28

When the action potential reaches the end of
the neuron it causes vesicles containing
neurotransmitter to fuse with the membrane
— this releases neurotransmitter, which
stimulates a response in a connecting cell

Question 29

Restoration of the resting membrane potential allows what

Answer 29

Restoration of the resting membrane potential allows the inactive voltage-gated sodium channels to return to a conformation that allows them to open again in response to depolarisation of the membrane Ion concentration gradients are reestablished by the sodium-potassium pump, which actively transports excess ions in and out of the cell

Question 30

Following repolarisation the sodium and potassium ion concentration gradients are reduced. what happens afterwards

Answer 30

Following repolarisation the sodium and potassium ion concentration gradients are reduced. The sodium-potassium pump restores the sodium and potassium ions back to resting potential levels.

Question 31

The retina is the area within the eye that detects light and contains two types of photoreceptor cells, which are what

Answer 31

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

Question 32

explain rods and cones

Answer 32

Rods function in dim light but do not allow colour perception. Cones are responsible for colour vision and only function in bright light.

Question 33

In animals the light-sensitive molecule retinal is combined with a membrane protein, opsin, to form what?

Answer 33

In animals the light-sensitive molecule retinal is combined with a membrane protein, opsin, to form the photoreceptors of the eye

Question 34

In rod cells the retinal-opsin complex is called what

Answer 34

In rod cells the retinal-opsin complex is called rhodopsin

Question 35

Retinal absorbs a photon of light and…

Answer 35

Retinal absorbs a photon of light and rhodopsin changes conformation to photoexcited rhodopsin. A cascade of proteins amplifies the signal

Question 36

Photoexcited rhodopsin activates what

Answer 36

Photoexcited rhodopsin activates a Gprotein, called transducin, which activates the enzyme phosphodiesterase (PDE)

Question 37

A single photoexcited rhodopsin activates what

Answer 37

A single photoexcited rhodopsin activates hundreds of molecules of G-protein. Each activated G-protein activates one molecule of
PDE

Question 38

Each active PDE molecule breaks down thousands of cGMP molecules per second. then what happens

Answer 38

Each active PDE molecule breaks down thousands of cGMP molecules per second. The reduction in cGMP concentration as a result of its hydrolysis affects the function of ion channels in the membrane of rod cells.

Question 39

PDE catalyses the hydrolysis of a molecule called what. and what does this cause

Answer 39

PDE catalyses the hydrolysis of a molecule called cyclic GMP (cGMP)This results in the closure of ion channels in the membrane of the rod cells, which triggers nerve impulses in neurons in the retina

Question 40

A very high degree of amplification results in what

Answer 40

A very high degree of amplification results in
rod cells being able to respond to low intensities of light

Question 41

In cone cells, different forms of opsin combine with what

Answer 41

In cone cells, different forms of opsin combine with retinal to give different photoreceptor proteins, each with a maximal
sensitivity to specific wavelengths: red,
green, blue or UV