FOM Flashcards
(35 cards)
1
Q
Examples of locations of receptors
A
- via plasma membrane (cell surface)
- via intracellular receptors
2
Q
What are parts that plasma membrane receptors commonly have?
A
- extracellular domain, transmembrane domain, intracellular domain
3
Q
Role of Nitric oxide in smooth muscle relaxation
A
- acts as primary messenger in pathway
- can act as second messenger within cells. Activates guanylyl cyclase which converts GTP to cGMP (vasodilation)
4
Q
Examples of enzymes used in signalling
A
- GTPases: bind to GTP to GDP
- phosphodiesterase: breaks phosphodiester bond
- kinase: transfer of phosphate group
- phosphatase: hydrolysis of organic phosphate in specific environment
5
Q
Structure of GPCRs
A
- 7 transmembrane alpha helices spanning domain
- specifically binds a G protein
6
Q
What is signal amplification?
A
- use chain of other protein messengers to amplify signal.
- complex can activate multiple AC - cascade effect
7
Q
Role of cAMP
A
- activated adenylyl cyclase converts ATP to cAMP
- transfers signals of hormones and can simulate different cell activities.
- elicits response via protein kinase A
8
Q
What are Tyrosine Kinase Receptors (RTK) activated by?
A
- growth and differentiation factors or metabolic regulators
9
Q
What occurs at RTKs at the point of ligand-binding?
A
- form dimer. Auto/cross-phosphorylation occurs at tyrosine residues at intracellular domain
10
Q
What does RTK autophosphorylation cause?
A
- receptor able to recognise and activate adaptor proteins
- activated relay proteins can then pass on signal within cell to elicit response
11
Q
Describe MAP kinase cascade
A
- GF binding and receptor dimerisation
- autophosphorylation allows Grb to dock
- binds to SOS. Complex activates RAS which activates MAPKKK- MAPKK-MAPK
- MAPK migrates to nucleus and phosphorylates target TFs
12
Q
Role of RAS
A
- small G protein functioning as monomer
- SOS transfers GTP to RAS causing activation
- length of RAS activation depends on rate of hydrolysis of GTP to GDP
- mutations locking RAS in active state cause many cancers
13
Q
What do anabolic enzymes do?
A
- building of molecules from smaller units into a larger one
14
Q
What do catabolic enzymes do?
A
- break down molecules into smaller units
15
Q
What does a Michaelis-Menten plot represent?
A
- relationship between the concentration of a substrate and the rate of the corresponding enzyme-controlled reaction
16
Q
What does Vmax mean?
A
- rate of reaction when enzyme is saturated with substrate
- maximum rate of reaction
17
Q
What does Km mean
A
- substrate conc. at which enzyme works at half its maximum rate.
- used to compare affinity of different enzymes for their substrates
18
Q
What is a line weaver-burke plot used for?
A
- determining Vmax and Vm of enzyme kinetics
19
Q
What comprises a nucleoside?
A
- nitrogenous base and sugar
20
Q
What comprises a nucleotide?
A
- nitrogenous base, sugar and phosphate
21
Q
What comprises a nucleic acid?
A
- nitrogenous base, sugar, phosphate and phosphodiester
22
Q
How do T and U bases differ?
A
- T on DNA, U on RNA
- T has a methyl group
23
Q
What are two ways bases in nucleotides can be synthesised?
A
- de novo
-salvage
24
Q
What is the start of purine formation?
A
- Ribose-5-phosphate which derives from pentose phosphate pathway
25
How is PRPP formed?
- Ribose-5-phosphate is converted into PRPP by PRPP synthesise
26
What happens in the reaction of PRPP with glutamine?
- glutamine donates one amide group to carbon 1 to form 5-phosphoribosylamine
27
What atoms are sequentially added to build the purine ring?
- glutamine
-aspartate
- CO2
28
What is the first fully formed purine nucleotide in the de novo pathway?
- IMP, inosine monophosphate
29
Describe feedback inhibition in purine formation
- ensures balance in purine synthesis
- AMP and GMP inhibit early steps of pathway.
-Cross-regulation
30
Describe the salvage pathway of purine formation
- recovers purine from normal cell turnover and converts to nucleoside triosphosphate
31
What enzymes are involved in the salvage pathway of purine formation?
- HGPRT: converts hypoxanthine to IMP and guanine to GMP
- APRT: converts adenine to AMP
32
What is the only purine nucleoside to be salvaged?
- Adenine
33
Importance of deoxyribonucletides in nucleotides synthesis
- ribonucleotide reductase converts ribonucleotides to deoxyribonucletides
- Feedback inhibition occurs when dATP is formed
34
How is orotate produced in pyrimidine formation?
1. glutamine, CO2, ATP, aspartate and tetrahydrofolate required in forming pyrimidine ring
2. carbamoyl aspartate is oxidised to form orotate
35
How does the attachment of pyrimidine ring to ribose-5-phosphate occur?
- PRPP provides ribose sugar
- reacts with orotate to form OMP
- enzyme PRPP synthetase converts ribose to PRPP
