Calcium and signalling

Question 1

What is cell signalling?

Answer 1

Communication for cells to respond

Question 2

What is chemotaxis?

Answer 2

Neutrophils responding to bacterial signal

Question 3

What is necrosis?

Answer 3

Disorganised cell death

Question 4

What is apoptosis?

Answer 4

Organised cell death

Question 5

What is endocrine signalling?

Answer 5

Hormone is secreted into blood which travels to the target cells

Question 6

What is paracrine signalling?

Answer 6

Cells communicate with adjacent cells, e.g. by cytokines

Question 7

What is direct contact signalling?

Answer 7

Some cells pack closely together to inhibit proliferation, e.g. pores in a cell membrane

Question 8

What is synaptic signalling?

Answer 8

Neurotransmitter released from one neutron and binds to receptors on another

Question 9

What is the suffix for a steroid?

Answer 9

-one

Question 10

What are the four types of receptors?

Answer 10

Steroid, G-protein, ligand gated ion channels, enzyme

Question 11

What is signal transduction?

Answer 11

Steps that occur once a receptor has received its signal that leads to changes in a cell

Question 12

How is a resting membrane potential maintained?

Answer 12

Calcium moves from a higher concentration outside cell to a lower concentration inside cell
Sodium moves from a higher concentration outside cell to a lower concentration inside cell
Potassium moves from a lower concentration outside cell to a higher concentration inside cell

Question 13

How many sodium move out for potassium moving in?

Answer 13

3 sodium out for every 2 potassium in
Calcium ATPase
Electrochemical gradient

Question 14

What kind of receptor is found at neuromuscular joint?

Answer 14

Ligand gated ion channels - nicotinic ACh

Question 15

What chemical binds to the ligand gated ion channels in neuromuscular junctions?

Answer 15

Nicotinic ACh

Question 16

Process of synaptic transmission at neuromuscular junction

Answer 16

Action potential travels down neuron
Sodium enters membrane which opens calcium channels
Synaptic trafficking of vesicles
Releases acetylcholine into cleft to bind with nicotinic ACh receptor to open pore
Sodium enters the muscle fibres

Question 17

How does a steroid receptor work?

Answer 17

Receptors found within the cytoplasm of cells
When steroid added, steroid receptors translocate to nucleus
Steroids are lipids - can diffuse across membrane
They bind to cytoplasmic receptors and move to nucleus
This causes gene and protein expression
In the nucleus, they bind to the enhancer region of DNA
(each steroid binds to a particular region of DNA)
Proteins (transcription factors) form a transcription imitation complex in promoter region
Causes transcription and translation of proteins
Many cells have many different receptors for steroids (SPECIFICITY)

Question 18

How do steroids work?

Answer 18

Bind to elements within DNA and can switch genes on and off and regulate transcription factors

Question 19

What are all steroids derived from?

Answer 19

Cholesterol

Question 20

Characteristics of G-protein coupled receptors

Answer 20

Involved in fight or flight
800 receptors
Mediate variety of signals, e.g. adrenaline
Lots of alpha helices spanning membranes 7 times

Question 21

What are G-protein couples receptors?

Answer 21

Membrane spanning receptors occurring on cell membranes

Question 22

Flow chart of response

Answer 22

Signal - receptor - transduction - response

Question 23

On what cells can direct signalling occur?

Answer 23

On cells next to each other

Question 24

On what cells can paracrine signalling occur?

Answer 24

On cells near each other

Question 25

On what cells can endocrine signalling occur?

Answer 25

Travels in bloodstream to target cells

Question 26

On what cells can synaptic signalling occur?

Answer 26

Neurones release neurotransmitters

Question 27

On what cells can autocrine signalling occur?

Answer 27

Bind to receptors on own membrane

Question 28

How long does it take for ligand-gated ions channels to work?

Answer 28

Milliseconds

Question 29

How long does it take for G-protein coupled receptors to work?

Answer 29

Seconds

Question 30

How long does it take for kinase linked receptors to work?

Answer 30

Hours - the kinase cascade takes time

Question 31

How long does it take for steroid receptors to work?

Answer 31

Hours (kinase cascade)

Question 32

How do enzyme linked receptors work?

Answer 32

Chemical binds to receptor - leads to two ligand monomers joining together Kinase domain of receptor phosphorylates other monomer of receptor Activates Ras - a GTPase Activates kinase cascade - phosphorylates the transcription factor Translocates to nucleus and switches on genes involved in growth, proliferation and cell division Herceptin blocks receptor and stops cascade - stops cell growth

Question 33

What do tyrosine kinase inhibitors do?

Answer 33

Stops phosphorylation between two domains

Question 34

What do MAP kinase inhibitors do?

Answer 34

Stop kinase cascade

Question 35

What do enzyme linked receptors do?

Answer 35

Target systems involved in cell death/survival Activate kinase cascade - proteins get phosphorylated and change shape, activating transcription factors to turn other genes off

Question 36

What impact does adrenaline have on skeletal and cardiac muscle?

Answer 36

More energy Increased vasodilation Weaker contraction of smooth muscle Stronger contraction of cardiac muscle

Question 37

What impact does adrenaline have on gut/skin?

Answer 37

Less energy Vasoconstriction Stronger contraction of smooth muscle

Question 38

What are the two types of adrenaline receptor?

Answer 38

Alpha and beta

Question 39

Where is adrenaline receptor beta I?

Answer 39

Heart

Question 40

Where is adrenaline receptor beta ii?

Answer 40

Lungs

Question 41

What doe kinases do?

Answer 41

Add phosphate to things

Question 42

How do beta receptors work?

Answer 42

Adrenaline binds to receptors and leads to G-protein receptor signalling pathway (or G-alpha-S) G proteins are receptors - GTPase Hydrolyse GTP bound to them into GDP Switched on by GTP and off by GDP Bound to two sub-units (heterotrimeric) G-alpha-S produces cAMP, which activates adenyl cyclase to convert ATP to cAMP cAMP is the second messenger and goes to activate kinases Activates kinase A which adds phosphate to proteins

Question 43

What does the S in G-alpha-S stand for?

Answer 43

Stimulatory

Question 44

How do alpha receptors work?

Answer 44

Ligand binding site GTP binding site on cytoplasmic domain G-alpha-q leads to IP3, which is a ligand IP3 binds to receptors found on stores (ER/SR) IP3 receptor is ligand gated calcium channel Activates protein kinase C IP3 increases calcium levels in cell G proteins switch off signal by converting GTP to GDP

Question 45

What kind of molecule is IP3?

Answer 45

A lipid

Question 46

What are beta-blockers?

Answer 46

Drugs that block beta adrenaline receptors on heart | Very similar structure to adrenaline

Question 47

What does protein kinase A do?

Answer 47

When activated by cAMP, it activates glycogen phosphorylase | Breaks down glycogen to glucose for energy

Question 48

What impact does protein kinase A have on cardiac muscle?

Answer 48

Can also phosphorylate L-type calcium channel to increase its likelihood of opening Calcium floods into cardiomyocytes more frequent Increases heart rate and muscle contraction

Question 49

How does PDE switch off a signal in a cell?

Answer 49

Breaks down cAMP into AMP Switches signal off cAMP leaves PKA Can inhibit PDE - signal continues for longer

Question 50

What does PDE stand for?

Answer 50

Phosphodiesterase