CEP wk1 - CELL COMMUNICATION

Question 1

3 TYPES OF CELL SIGNALLING

Answer 1

AUTOCRINE (targets sites on same cell) PARACRINE (targets sites on adjacent target cell) ENDOCRINE (hormones used to reach target cells)

Question 2

1st vs 2nd messengers

Answer 2

first messengers go directly to receptor but secondary messengers are produced when a receptor is activated

Question 3

OTTO LOEWI EXPERIMENT (to prove receptors)

Answer 3

2 separate frog hearts (stimulation of first heart released something that stimulated second heart contraction)

Question 4

AGONIST V ANTAGONIST

Answer 4

agonist binds to a target & activates it but antagonist binds to target & prevents other molecules binding

Question 5

NICOTINIC ACETYLCHOLINE RECEPTOR (nAcHR)

Answer 5

• pentamer (2 of the 5 sub-units are AcH binding site)

- no AcH = gate is shut so NA+ can’t cross membrane

Question 6

HOW TO MEASURE LIGAND BINDING TO RECEPTOR

Answer 6

add radioactive ligand to sample containing receptor & allow to bind then wash away any excess ligand & measure radioactivity (proportional to ligand conc.)

Question 7

HOW GPCR’S WORK (have 7 helices to have 1 central unit)

Answer 7

1. agonist binds to receptor which stimulates heterotrimeric G protein (A,B,Y) to bind
2. GDP in G-protein replaced with GTP (activates protein)
3. activated G-protein A & B/Y sub-units split off & regulate effectors (B&Y anchored to membrane)
4. G-alpha protein inactivated as GDP reformed (hydrolysed) & inactivated heterotrimeric G-protein reformed

Question 8

ADENYL CYCLASE (ATP -> AMP)

Answer 8

• converts ATP to cAMP & then phosphodiesterase (PDE) converts cAMP -> AMP

Question 9

PHOSPHOLIPASE C

Answer 9

• agonist binds to receptor & PIP2 split into DAG (activates protein kinase C) & InsP3 (provides calcium which binds to ion channels on ER surface to release CA2+ into membrane to activate protein kinase C (leads to effector)
• receptor = protein kinase C active = calcium binds to channels to release Ca2+ to membrane to also activate protein kinase

Question 10

HORMONAL REGULATION OF GLYCOGEN

Answer 10

1. glucagon binds to G-protein = adenyl cyclase= cAMP = AMP (by phosphodiesterase) = protein kinase A
2. protein kinase A phosphorylates (activates) glycogen synthase (forms glycogen) & then forms p-glycogen synthase (inactive)
3. protein kinase A also phosphorylates kinase (inactive) to glycogen phosphorylase B (inactive) which is activated to glycogen phosphorylase A (active)
4. OVERALL glycogen + Pi = glucose

Question 11

PROTEIN PHOSPHATASES

Answer 11

removes phosphates (phosphorylated protein -> protein)

Question 12

TSH RECEPTOR ROLE IN THYROID

Answer 12

TSH released from pituitary = binds to GPCR = adenyl cyclase = cAMP = pKA (rep. of thyroid cells & induces release of thyroid hormones)

Question 13

AUTONOMOUS THYROID ADENOMA (ATA)

Answer 13

benign tumour in thyroid = hyperthyroidism (mutation in TSH receptor so active in absence of TSH (makes cAMP = hormone release))

Question 14

TSH RESISTANCE

Answer 14

mutation where TSH receptors resistant to TSH (hypothyroidism)

Question 15

LIPOPHILIC HORMONES (STEROIDS)

Answer 15

pass through membrane without need of channels

Question 16

WATER-SOLUBLE HORMONES (PEPTIDE)

Answer 16

bind to receptor on membrane so receptor changes to allow hormone through

Question 17

CORTISOL NEED

Answer 17

glucose regulation & inflammatory response

Question 18

ALDOSTERONE NEED

Answer 18

blood pressure & NA+ regulation

Question 19

IODINE DEFICIENCY

Answer 19

no iodine = t4 (needed for negative feedback) not made so we have excess TSH so tumour-like lump forms

Question 20

TREATMENT FOR THYROID ISSUES

Answer 20

surgical removal, antithyroid drugs, radioactive drugs

Question 21

ENDO VS EXO-CRINE GLANDS

Answer 21

endo release hormones directly into blood but exo release secretions to outside of body e.g. sweat

Question 22

NERVOUS VS ENDOCRINE SYSTEM

Answer 22

endocrine has more neurotransmitters (hormones), is slower, is longer lasting & transfers in blood not synapses

Question 23

INTRACRINE SIGNAL

Answer 23

signal generated by a hormone created in the same cell (cytoplasm makes & also has receptor for one hormone all in cytoplasm)

Question 24

AUTOCRINE SIGNAL

Answer 24

signal where cell has a receptor on the exterior for the hormone it creates within (makes hormone inside & receptor is on skin outside)

Question 25

PARACRINE SIGNAL

Answer 25

chemical communication between neighbouring cells (hormone released & receptor for it is on neighbouring cell)

Question 26

3 GROUPS OF HORMONES

Answer 26

• protein/peptide hormones
• steroid hormones (adrenal)
• amines (thyroid)

Question 27

PROTEIN/PEPTIDE HORMONES (e.g. insulin)

Answer 27

pre-formed in vesicles in ribosomes on RER in ready to be released by exocytosis when needed (pre-hormone goes to golgi to be made hormone & released in vesicle ready for lysosomes to break it down & release signal)

Question 28

STEROID HORMONES (e.g. cortisol)

Answer 28

• hydrophobic (need carrier proteins)
• ester hydrolysed to cholesterol & cholesterol converted to pregnenolone (diffuses out of cell)
• bind to nuclear receptors & also activate GPCR

Question 29

AMINES

Answer 29

• non polar & small so hydrophobic & need carrier protein
• synthesised from amino acids called tyrosines