Chemical Signaling Transduction

Question 0

Receptor specificity

Answer 0

Example neurotransmitter acetylcholine
There are two general classes of receptors

Muscarinie- in heart muscle increases potassium release and relaxation, agonist could be used to treat hypertension in COPD

Nictinic -in muscle induces sodium influx and contraction, antagonists can be used as muscle relaxants

Question 1

Response is based on receptor specificity

Answer 1

Cells express many different types of receptors
100s and 1000s given receptors on a cell surface
Amount of rector is controllable (regulated)

Question 2

Amplification in lipophillic messenger

Answer 2

One hormone/receptor can cause many mRNA, each mRNA can form many proteins

Question 3

Hydrophilic messenger

Answer 3

System can include channel linked receptors ans other second messengers (ca2+ , cGMP)

One messenger molecule leads to the phosphorylation of millions of proteins
Phenomenal amplification - need to turn a signal off
Phosphdiesterase- breaks down cAMP rapidly
Exercise breaks down and mobilizes fat cells

Question 4

During exercise

Answer 4

Multiple tissues numerous hormones

Several hormones use cAMP as a secon messenger - epinephrine, norepinephrine and glucagon increase cAMP
- insulin decreases so cAMP increases (only hormone to decrease durning exercise)

Consequences of cAMP in activation in various target issue

• heart muscle increase strength of contraction and heart rate
• Skeletal muscle facilitate glycogenolysis and lipolysis
• adipose stimulate lipolysis
• Liver stimulate glycogenolysis and gluconegenesis ( production of glucose by liver from non glucose sources)

Question 5

Signalling from a disease perspective

Answer 5

Maintaining normal fluid level in lumen is a mater of chloride and sodium secretion

Too much loss of fluid can be life threatening

Chloride and sodium pumps are regulated by a protein kinase and cAMP

Secreted Cholera toxin activating Gprotein for a prolonged period signalling doesn’t shut off. Cause cl- and Na+ and water to be released . Diarrhea.

Question 6

Cystic fibrosis transmembrane conductance regulator

Answer 6

Cystic fibrosis is homozygous mutation in CFTR gene (a cl- transporter) impairs regulation of sweat digestive juices and mucus could protect against cholera toxin