Unit 1: Cells And Proteins KA 1.4: communication and signalling

Question 1

The three examples of extracellular signal molecules

Answer 1

steroid hormones, peptide hormones, and neurotransmitters

Question 2

what molecule are receptors made of?

Answer 2

Protein

Question 3

suggest why cell may not respond to a signalling molecule

Answer 3

They don’t have complementary receptors

Question 4

Describe how different tissues have tissue specific responses to the same signalling molecules

Answer 4

differences in the intracellular signalling molecules and pathways

Question 5

What are examples of hydrophobic signalling molecules?

Answer 5

Steroid hormones such as oestrogen and testosterone

Question 6

describe the term transcription factor

Answer 6

Transcription factors are proteins which can affect gene expression by binding to DNA and stimulating or inhibiting transcription of genes

Question 7

do hydrophobic molecules pass through the membrane?

Answer 7

Yes

Question 8

what does a hydrophobic signalling molecule binding to receptors make?

Answer 8

Hormone receptor complex

Question 9

what happens after the hormone receptor complex is made in the stages of steroid hormones influencing transcription

Answer 9

The hormone receptor complex moves to the nucleus where it points to specific section of DNA called hormone response element

Hormone receptor complexes are a transcription factor so it influences the transcription/expression of lots of changes in the DNA. It can stimulate or inhibit it

Question 10

example of hydrophilic molecules

Answer 10

Peptide hormones and neurotransmitters

Question 11

What does transduced mean?

Answer 11

converted

Question 12

explain G proteins in hydrophilic signalling

Answer 12

1) hydrophilic signalling molecules bind to the transmembrane extracellular receptor

2) this causes a conformational change in the receptor

3) the G protein is activated and relays the signal to a protein such as an ion channel or enzyme

Question 13

explain the phosphorylation cascade in hydrophilic signalling

Answer 13

1) hydrophobic signalling molecules bind to the transmembrane extracellular receptor

2) this causes a conformational change in the receptor

3) this causes a phosphorylation cascade where one kinese activates the next and so on

Question 14

Name an example of a peptide hormone

Answer 14

insulin

Question 15

The phosphorylation cascade started by the binding of the insulin to receptors causes the recruitment of GLUT4 glucose transporters in the plasma membrane of what cells

Answer 15

fat and muscle cells

Question 16

what does insulin binding to the extracellular receptor do in the recruitment of GLUT4 transporters?

Answer 16

causes a confirmational change and phosphorylation of the receptor which triggers an intracellular signalling Phosphorylation cascade

Question 17

what do vehicles do in the recruitment of GLUT4 transporters?

Answer 17

vehicles move GLUT4 transporters to the membrane after the phosphorylation cascade

Question 18

what is the purpose of GLUT4 transporters?

Answer 18

Glucose moves through the GLUT4 transporters down its concentration gradient into fat and muscle cells. This is an example of facilitated diffusion.

Question 19

cause of type one diabetes and what it causes

Answer 19

genetic, failure to produce insulin

Question 20

cause of type two diabetes and what it causes

Answer 20

Lifestyle choices, i.e. obesity and it causes loss to receptor function

Question 21

Treatment of type one diabetes

Answer 21

Insulin injections

Question 22

Treatment of type two diabetes

Answer 22

lifestyle changes, i.e. healthier diet and more exercise which triggers recruitment of GLUT4

Question 23

explain why hydrophilic signal molecules do not pass through the membrane

Answer 23

They cannot pass through the hydrophobic region

Question 24

Name two structures that can be activated by G proteins

Answer 24

enzymes and ion channels

Question 25

by which process does glucose move into fat and muscle cells?

Answer 25

Facilitated diffusion

Question 26

describe the meaning of the term resting membrane potential

Answer 26

when there is no net flow of ions across the membrane

Question 27

what is membrane potential?

Answer 27

The electrical potential difference or voltage across the membrane

Question 28

What maintains the electoral chemical gradient?

Answer 28

Sodium potassium pumps

Question 29

what is action potential?

Answer 29

A wave of electrical excitation along the neurons plasma membrane

Question 30

Explain depolarisation

Answer 30

when the cell becomes more positive due to the influx of positive sodium ions as a result of neurotransmitters binding at the synapse. The neurotransmitter receptors are Ligand gated sodium ion channels once a threshold is reached voltage gated sodium channels also open causing rapid further depolarisation, this triggers the adjacent voltage gated sodium channels depolarising the next section of membrane

Question 31

Explain repolarisation/hyperpolarisation

Answer 31

after the wave of depolarisation passes, there has to be a process to re-establish the resting potential ready for the next impulse Sodium channels close and voltage gated potassium channels open this makes the positive potassium ions diffuse out of the neuron cell down the electrochemical gradient. This makes the inside of the cell more negative. this can go too far in the cell becomes more negative than the resting membrane potential which is called hyperpolarisation

Question 32

explain the restoration of the resting membrane potential

Answer 32

following repolarisation the sodium and potassium ion concentration gradient are reduced The sodium potassium pump restores the sodium and potassium ions back to resting potential once resting potential has reached the potassium channel closes again restoration of the resting membrane potential allows the inactive voltage gated sodium channels to return to a confirmation allows them to open again in response to the depolarisation of the membrane

Question 33

what is the function of the photoreceptor **rods**?

Answer 33

functions in the dim light but does not allow colour perception

Question 34

what is the function of the photoreceptor **cones**?

Answer 34

responsible for colour vision and only function in bright light

Question 35

Where does light hit the eye and what are the structures of this area?

Answer 35

Retina made up a photoreceptors called Rod and corn cells

Question 36

What kind of signal is the light being converted into in the eye?

Answer 36

Electrical

Question 37

how many G proteins are activated by one photoexcited rhodopsin?

Answer 37

100s

Question 38

how many PDE does each G protein activate?

Answer 38

1

Question 39

how many cGMP molecules does each PDE breakdown?

Answer 39

1000s

Question 40

how does cGMP cause a nerve impulse in retinal neurons?

Answer 40

decrease in the cGMP concentration causes sodium channels to close triggering a nerve impulse

Question 41

Why can rod cells respond to a low light level?

Answer 41

an effect of a single photon is amplified many times

Question 42

what wavelength can cone cells be sensitive?

Answer 42

Red, green, blue and UV