1.4

Question 1

How do multicellular organisms signal between cells?

Answer 1

Using extracellular signalling molecules

Question 2

What are receptor molecules of target cells

Answer 2

Proteins with a binding site for a specific signalling molecule

Question 3

What initiates a response in a cell

Answer 3

Binding causes a change in conformation of the receptor

Question 4

Cells produce specific what?

Answer 4

Signals

Question 5

When a cell produces a specific signal, how can it be detected and responded?

Answer 5

By a specific receptor

Question 6

In a multicellular organism, different cell types show a what to the same signal?

Answer 6

Tissue specific response

Question 7

What can hydrophobic signalling molecules do that allow them to bind to intracellular receptors?

Answer 7

They can diffuse straight through the phospholipid bilayer

Question 8

Receptors for hydrophobic signally molecules are described to be what?

Answer 8

Transcription factors

Question 9

What are examples of hydrophobic signally molecules?

Answer 9

Steroid hormones that are oestrogen and testosterone

Question 10

Steroid hormones bind to receptors in the what?

Answer 10

Cytosol or nucleus

Question 11

Whereas the hormone receptor complex moves to the nucleus what happens?

Answer 11

It binds to specific sites on DNA and affect gene expression

Question 12

What do hydrophilic signally molecules bind to

Answer 12

Transmembrane receptors and DO NOT ENTER THE CTYOSOL

Question 13

When do transmembrane receptors change conformation

Answer 13

When a ligand binds to extracellular face

Question 14

What happens to the signal, when the ligand binds to the transmembrane receptors making a change in conformation, as it can not enter the cell?

Answer 14

Signal is Transduced across plasma membrane

Question 15

What do transmembrane receptors act as?

Answer 15

Signal transducers

Question 16

What do transduced hydrophilic signals involve?

Answer 16

G proteins or cascades of phosphorylation by kinase enzyme

Question 17

What does phosphorylation cascades do ?

Answer 17

Allows more than one intracellular signalling pathway to be activated

Question 18

Explain the insulin binding

Answer 18

Peptide hormone insulin binds to the receptor which makes a intracellular signalling cascade that triggers recruitment GLUT 4 glucose transporter to the membrane of fat and muscle cells

Question 19

Describe type 1 diabetes

Answer 19

Diabetes mellitus can be caused by a failure to produce insulin

Question 20

Describe type 2 diabetes

Answer 20

Loss of receptor function

Question 21

What can exercise do to people with type 2 diabetes

Answer 21

Allow recruitment of GLUT 4 and improve uptake of glucose to fat and muscle cells

Question 22

State the term for when there’s no net flow of ions across the membrane?

Answer 22

Resting

Question 23

What does the transmission of a nerve impulse require?

Answer 23

A change in membrane potential of neurons plasma membrane

Question 24

What is a action wave

Answer 24

A wave of electrical excitation along a neurons plasma membrane

Question 25

How do neurotransmitters initiate a response

Answer 25

By binding to their receptors at the synapse

Question 26

What causes a depolarisation of the plasma membrane

Answer 26

A entry of positive ions trigger a opening of voltage gated sodium channels and further depolarisation occurs

Question 27

What restores the membrane potential?

Answer 27

The inactivation of sodium channels and opening of potassium channels

Question 28

What makes a depolarisation of a patch of neighbouring regions of membrane to depolarise and go through the same cycle?

Answer 28

Opening of sodium channels

Question 29

What happens when the action potential reaches the end of the neuron?

Answer 29

Vesicles containing nuerotransmitter fuse with the membrane and stimulates a reactors in the cell as it is released

Question 30

What does the restoration of the resting membrane allow?

Answer 30

Allows inactive voltage gated sodium channels to return to a conformation which allows them to open again in response to a depolarisation

Question 31

What does the sodium potassium pump do for nerve transmission

Answer 31

Re-establishes ion concentration gradients by actively transports excess ions in and out of cell

Question 32

Where’s the bit in the eye that detects light

Answer 32

Retina

Question 33

What type of photoreceptor cells does the retina contain

Answer 33

Rods and cones

Question 34

What type of molecule is the retinal

Answer 34

Animal Light sensitive

Question 35

What type of molecule is opsin

Answer 35

Membrane protein

Question 36

What’s the rod cell molecule called when retinal and opsin combines

Answer 36

Rhodopsin

Question 37

What happens when retinal absorbs a photon

Answer 37

Rhodopsin changes conformation to photo-excited rhodopsin

Question 38

A cascade of protein does what

Answer 38

Amplifies the signal

Question 39

What does photoexcited rhodopsin activate

Answer 39

G protein (transducin)

Question 40

What does G protein (transducin) activate

Answer 40

PDE (phosphodiesterase)

Question 41

PDE catalyses the hydrolysis of what molecule?

Answer 41

cGmp

Question 42

What triggers a nerve impulse in neurons in the retina

Answer 42

Closure of ion channels in the membrane of rod cells

Question 43

How can rod cells respond to low intensities to light

Answer 43

Very High degree of amplification

Question 44

How are different photoreceptor proteins with maximal sensitivity to specific wavelengths created

Answer 44

In cone cells, different forms of opsin combine with retinal