Unit 1-Communication And Signalling

Question 1

Why is it essential that cells communicate within multicellular organisms?

Answer 1

In order to get required integration and co-ordination for cellular activities

Question 2

What are the two principle forms of communication?

Answer 2

HormonalNervous

Question 3

Where are the receptor proteins for hydrophobic signals?

Answer 3

Within the cell/nucleus

Question 4

Why do hydrophyllic signals require cell surface receptor proteins?

Answer 4

Cannot pass through the membrane

Question 5

What are hormones?

Answer 5

Extracellular signalling molecules that are secreted by one tissue into the blood

Question 6

What are the two types of hormones?

Answer 6

Hydrophobic and Peptide

Question 7

Give examples of hydrophobic hormones?

Answer 7

Steroid HormonesThryoxine

Question 8

Give examples of hydrophyllic hormones

Answer 8

Peptide Hormones

Question 9

What are neurotransmitters?

Answer 9

Signals that are released into the synaptic gap between a nerve cell and its neighbour

Question 10

What are the receptor proteins for steroid hormones?

Answer 10

Transcription factors

Question 11

What is a transcription factor?

Answer 11

Protein that binds to DNA and controls the rate of transcription

Question 12

Give an example of a steroid hormone

Answer 12

Testosterone, Oestrogen

Question 13

What happens to the metabolism of a cell in the absence of thyroxine?

Answer 13

Metabolic rate is lower

Question 14

What happens when thyroxine binds to its receptor protein?

Answer 14

Receptor undergoes conformational changeCan no longer bind to DNAGene for sodium potassium pump is transcribed

Question 15

What are the two ways a cascade is activated once a hydropyllic signalling molecule binds to a receptor protein?

Answer 15

G proteinsPhosphorylation by Kinase Enzymes

Question 16

Give examples of peptide hormones

Answer 16

InsulinGlucagon

Question 17

What are G protein coupled receptors linked to?

Answer 17

A G protein

Question 18

What is the difference between a G protein being on or off?

Answer 18

Whether GTP or GDP is attached

Question 19

What happens when a hydrophyllic signalling molecule binds to the extracellular side of GPCR?

Answer 19

GTP replaces GDP and the G protein becomes active

Question 20

What happens when a G protein is active?

Answer 20

G protein stimulates enzymes leading to a response in the cell

Question 21

Why is the response only temporary if the G protein triggers the response?

Answer 21

G protein is a GTPase and hydrolyses the GTP into GDP making the G protein inactive again

Question 22

What is the insulin receptor?

Answer 22

Kinase linked receptor

Question 23

Where is the insulin receptor found?

Answer 23

Cell membrane of fat and muscle cells

Question 24

What happens once insulin binds its receptor?

Answer 24

Signal is transduced and a series of phosphorlyation events trigger the recruitment of GLUT4 to the cell membrane

Question 25

What does GLUT4 allow?

Answer 25

Allows glucose to enter the cell

Question 26

What is Diabetes Mellitus?

Answer 26

Medical Condition caused by a failure at some stage of insulin signalling pathway

Question 27

What is the difference between Type 1 and Type 2 diabetes?

Answer 27

Type 1 - Failure to produce insulin Type 2 - Loss of receptor function

Question 28

How is type 1 diabetes treated?

Answer 28

Injections of Insulin

Question 29

How does exercise improve type 2 diabetes?

Answer 29

Triggers recruitment of GLUT4

Question 30

What do organisms use light energy for?

Answer 30

Generating ATPDetect changes in their enviroment

Question 31

What prosthetic group is present in rhodopsin?

Answer 31

Retinal

Question 32

Where does retinal absorb energy from?

Answer 32

Photons

Question 33

Where do the hydrogen ions diffuse back through?

Answer 33

ATP Synthase

Question 34

What is retinal?

Answer 34

Prosthetic group covalently bonded to polypeptide called opsin

Question 35

What are the two classes of photoreceptor cells found in the retina of vertebrates?

Answer 35

Cone and Rod cells

Question 36

What do cone cells contain?

Answer 36

Photopsins

Question 37

Which class of photoreceptor cells is responsible for colour vision?

Answer 37

Cone cells

Question 38

Why are cone cells less sensitive than rod cells?

Answer 38

They have about 1000x less photoreceptor molecules

Question 39

How many types of photopsins are found in human cells?

Answer 39

3

Question 40

What are the colours each type of photopsin have maximal sensitivity to?

Answer 40

Red, blue and green

Question 41

How are different photopsins formed?

Answer 41

Combining retinal with different forms of opsins

Question 42

What do Rod cells produce when no light has been absorbed?

Answer 42

Cylic GMP

Question 43

Where does cGMP bind to?

Answer 43

Ligand gated Na+ channels

Question 44

What happens when a photon of light is absorbed by a retinal molecule?

Answer 44

Conformational change in rhodopsinActivates hundreds of G proteins which activates hundred of enzymes

Question 45

What do the enzymes do when activated by G proteins?

Answer 45

Catalyse breakdown of cGMP

Question 46

What does the breakdown of cGMP cause?

Answer 46

Na channels closeMembrane will become hyperpolarizedNerve impulse is generated

Question 47

What provides a high degree of amplification?

Answer 47

Protein cascade

Question 48

What are the steps in the protein cascade?

Answer 48

RhodopsinG proteinsEnzymes Channels

Question 49

What is a photoreceptor?

Answer 49

Name given to proteins which are capable of sensing and responding to light