cell biology 7

Question 1

what is signal transduction

Answer 1

process by which cells translate intracellular and extracellular signals to a cellular response

Question 2

what does signal transduction regulate

Answer 2

• growth
• division
• differentiation
• behaviour
• cell death - apoptosis

Question 3

what are the signalling pathways

Answer 3

• regulatory proteins
• chemical signals

Question 4

what are the major steps in cell signalling

Answer 4

1) reception - signal molecule binds to a receptor protein
2) transduction - receptor activates one or more intracellular signalling pathways
3) response - one or more intracellular signalling proteins alters the activity of effector proteins

Question 5

what is contact dependent signal transmission

Answer 5

• signalling cell has membrane bound signal molecule which attaches to attachment protein on target cell

Question 6

what is autocrine cell signalling

Answer 6

• signal produced in cell and signals cell by exocytosis

Question 7

what is paracrine cell signalling

Answer 7

• local mediator - short lived signals target cells from the signalling cell

Question 8

what is synaptic cell signalling

Answer 8

• neurotransmitters move across synapse and to target cell receptors on the cell surface membrane

Question 9

what is gap junction signalling

Answer 9

• small molecules move between gap junctions and passes on signals

Question 10

what is endocrine cell signalling

Answer 10

• endocrine cell secretes hormones into bloodstream and they bind to receptors on the target cell

Question 11

what are the types of signalling molecules

Answer 11

• Proteins
• Small peptides
• Amino acids
• Nucleotides
• Steroids
• Retinoids
• Fatty acid derivatives
• Dissolved gases; e.g. Nitric oxide and carbon monoxide

Question 12

what types of cell transduction receptors are there

Answer 12

• cell surface receptors
• intracelular receptors

Question 13

what are the 3 main classes of cell surface receptors in signal transduction

Answer 13

• ion channel receptors
• enzyme linked receptors
• G-protein coupled receptors

Question 14

what are the common water soluble intracellular signals

Answer 14

Cyclic AMP (cAMP)
Cyclic GMP (cGMP)
Calcium

Question 15

what are the common lipid intracellular signals

Answer 15

Diacylglycerol (DAG)
Phosphatidylinositol 4,5-bisphosphate (PIP2)
→ Released soluble Inositol 1,4,5-trisphosphate (IP3

Question 16

what are the common intracellular enzyme modification signals

Answer 16

Protein Phosphorylation
GTP binding

Question 17

what is protein phosphorylation regulated by

Answer 17

• kinase and phosphatases
• can lead to kinase cascades

Question 18

what is GTP binding regulated by

Answer 18

• Guanine nucleotide exchange factors (GEFs)
• GTPase-activating proteins (GAPs)

Question 19

what are the two main forms of GTP binding

Answer 19

• G proteins - Large, trimeric, relay signals from G-protein-coupled receptors
• Monomeric GTP-binding proteins - small, monomeric, relay signals from many cell-surface receptors

Question 20

describe the hyperbolic response curve

Answer 20

• responses increases gradually
• plateau as the pathway is saturated

Question 21

describe the sigmoidal response curve

Answer 21

• reduced response at low signal concentrations

Question 22

describe the all or none curve

Answer 22

• cell switches between a low and high response

Question 23

what is positive feedback

Answer 23

• activation of the signal causes an amplification of the signal

Question 24

what is negative feedback

Answer 24

• activation of the signal reduces the signal
• cells can become desensitised to signal

Question 25

how are G protein coupled receptors activated

Answer 25

• Guanine nucleotide exchange factor (GEF) to G-Proteins
• Remains active with bound signal → Multiple G-Protein activations

Question 26

what do trimeric GTP-binding proteins do

Answer 26

• Acts on ion channels or enzymes
  α Subunit - Binds GDP/GTP
  - Membrane anchored

β Subunit - Becomes activated with γ

γ Subunit - Becomes activated with β
- Membrane anchored

Question 27

what regulated the activity of G protein coupled receptors

Answer 27

• Activity of GPCRs are regulated by Phosphorylation by GRK and Arrestin binding
• Arrestin blocks G-Protein binding and promotes internalisation of GPCRs
• Some activated Arrestin molecules lead to separate signalling pathways

Question 28

what stimulates cAMP production

Answer 28

• Many GPCRs stimulate cAMP production in hormone signalling - via Adenylyl Cyclase