L39

Question 1

What are the type of signals?

Answer 1

Paracrine
Autocrine
Hormones
Neural

Question 2

Why do cells need to communicate?

Answer 2

To respond to the environment

Question 3

Identify and explain the action distance of cell signalling

Answer 3

Very short distance :
- autocrine : cells act upon themselves by having the ligand receptor
Short distance :
- contact-dependent : depends on close-contact between cells (gap junction)
- paracrine : cells act upon neighbouring cells
Long distance :
- synaptic : secrete neurotransmitters along the synapse
- endocrine : secrete hormones to bloodstream
And it acts on the whole body

Question 4

What are the functions of gap junction?

Answer 4

• allow direct communication between cytoplasm of adjacent cells
• allow to receive same stimulus for neighbouring cells

Question 5

Identify the types of cell receptors

Answer 5

Cell surface :
- hydrophilic : can’t cross membrane
Intracellular :
- hydrophobic or lipohilic : cross membranes

Question 6

Explain how ephexin is activated

Answer 6

• clustering of receptors
• dimerisation of receptors : trans-phosphorylation on tyrosine
• kinase domain binds : phosphorylation of ephexin
• active ephexin kicks out GDP on RhoA and exchange it to GTP : activation of RhoA
• RhoA : actin-myosin interaction