Lecture 13: Receptors 1

Question 1

What leads to the activation or inhibition of proteins?

Answer 1

• Chemical substance travels from its source.
• Chemical substance interacts with its target protein – this is often called binding or reception.
  -The binding event affects the protein to either activate or inhibit it.
• This leads to functional consequences, that change the cellular response.

Question 2

Most receptors are found on the inside/outside of the cell where they act as sensors of the intracellular/extracellular environment. (Circle the correct words).

Answer 2

the outer cell membrane and detect signals from the extracellular environment

Question 3

What is an advantage of the receptor being located where it is?

Answer 3

On the outside of the cell thus the ligand does not have to pass through the cell membrane thus much more efficient signaling can take place via signal transduction

Question 4

Compare and contrast enzymes and receptors.

Answer 4

Enzymes
* Generally one active site.
* Bind substrates.
* Change substrate into product.
* Can be membrane bound or free in cytosol.

Receptors
* Can have several binding sites.
* Bind ligands.
* Release ligand unchanged.
* Can be membrane bound or free in cytosol.

Question 5

What are the three main classes of receptor?

Answer 5

1. Ligand-gated ion channel
2. G protein-coupled receptor (GPCR)
3. Receptor tyrosine kinase (RTK)

Question 6

Are ligand-receptor interactions specific or non-specific?

Answer 6

There is specificity between ligands and receptors

Question 7

What is a signal transduction pathway?

Answer 7

• Active receptor starts a chain of events where messages are passed on through the cell via a process called signal
  transduction.
• Different receptors use different types of relay molecule to pass on messages.

Question 8

What is the difference between an agonist and an antagonist?

Answer 8

Agonist - A chemical substance that binds to a receptor and activates it.

Antagonist - A chemical substance that binds to a receptor and prevents activation by an agonist.

Question 9

Are endogenous ligands more likely to be an agonist or antagonist?

Answer 9

They are more likely to be agonist as endogenous ligands are made within the body and predominantly have the function of receptor activation therefore agonist.

Question 10

Drugs and toxins are an example of what type of ligand?

Answer 10

Exogenous ligands

Question 11

What happens to the receptor when activated by a ligand?

Answer 11

Receptor undergoes a conformational (shape) change to become activated and begin signal transduction.