L7: Cell Communication

Question 1

What is paracrine activation?

Answer 1

signalling cell releases hormone to activate neighbouring target cell

Question 2

What is autocrine activation?

Answer 2

same cell secretes hormone and has receptor
- usually for negative feedback loops

Question 3

What is endocrine activation?

Answer 3

• specific cells secrete their hormone into bloodstream, circulates around body
• acts on target cell when comes into contact

Question 4

What is contact dependent activation?

Answer 4

target and signalling cells are physically connected

Question 5

Describe the concept of synergy

Answer 5

maximum combined response > sum of individual responses

Question 6

What must happen for a hormone to have its effect? How does increasing hormone levels support this?

Answer 6

have to bang into binding site of receptor for effect, literally random chance
increasing circulating hormone levels → increases chance of receptor interaction

Question 7

How is the sensitivity of a target cell regulated?

Answer 7

by continuously making, degrading and moving receptors - allows body to regulate number of receptors expressed

Question 8

Describe upregulation of target cell sensitivity

Answer 8

synthesis > degradation
⇒ increased sensitivity

Question 9

What are the 3 types of hormones? What is each derived from?

Answer 9

peptides - from three amino acids to large proteins
amines – derivatives of tyrosine (amino acid)
steroids – synthesised from cholesterol

Question 10

Which hormones cannot cross cell membranes?

Answer 10

amines (except thyroid hormone) and peptides

Question 11

Which hormones use intracellular receptors? How are they transported?

Answer 11

steroids and thyroid hormone
- lipid soluble, need a carrier in plasma to help them dissolve in water
- released from carrier protein into cell

Question 12

How are amines transported?

Answer 12

packaged in vesicle, cannot cross membrane (except TH)

Question 13

Describe (briefly) where and how peptides are made and excreted.

Answer 13

• made in rER
• packaged in golgi apparatus
• stored in vesicles
• secreted by exocytosis

Question 14

Which type of hormones bind to receptors on the cell membrane? How do they produce a response inside the cell?

Answer 14

Amines & Peptides
- use second messengers to produce a response
- cAMP phosphorylates proteins/enzymes, which generally turns them on
- can also activate transcription factor proteins → turn on early genes → cell specific genes