Signal Transduction

Question 1

What is a receptor?

Answer 1

A protein that recognises a hormone/neurotransmitter/ligand and binds to it - it allows signals to alter cellular metabolism

Question 2

What are the two types of receptors?

Answer 2

Intracellular and plasma membrane receptors

Question 3

Intracellular receptors are found in the cytoplasm or the nucleus. For those found in the cytoplasm, how do they get to the nucleus upon activation?

Answer 3

By translocation

Question 4

Where are plasma membrane receptors found?

Answer 4

Embedded in the cell membrane and are present outside of the cell

Question 5

Do plasma membrane receptors respond to hydrophobic or hydrophilic signals?

Answer 5

Hydrophilic signals

Question 6

A DNA binding domain (DBD) in a steroid hormone receptor contains two zinc fingers. How does this allow it to bind to the DNA?

Answer 6

The zinc fingers are positively charged and can electrostatic ally bind to the negatively charged phosphate backbone of the DNA

Question 7

What is the section called downstream of the zinc finger in the DNA binding domain (DBD)?

Answer 7

The recognition sequence

Question 8

Cell surface receptors bind to a ligand and send their signal inside of the cell. Through what molecule is the signal sent through the cell to where it needs to be?

Answer 8

By intracellular secondary messengers

Question 9

What is acetylcholine?

Answer 9

An important signalling molecule

Question 10

What is an example of a receptor that has intrinsic enzymatic activity?

Answer 10

Receptor tyrosine kinases

Question 11

What types of receptors activate intracellular secondary messengers?

Answer 11

G protein-coupled receptors and plasma membrane receptors

Question 12

What important signalling pathways are receptors that activate intracellular secondary messengers involved in?

Answer 12

1. Light detection pathways
2. Odorant detection pathways

Question 13

Ligand-gated ion channels contain both a ligand-binding site and an ion channel. It is normal closed - how does it open?

Answer 13

In response to ligand binding

Question 14

What enzyme removes phosphate groups from tyrosine?

Answer 14

Tyrosine phosphatase

Question 15

What four common structural features do all receptor tyrosine kinases have?

Answer 15

1. Extracellular ligand-binding domain
2. Single transmembrane domain
3. Cytoplasmic tyrosine kinase domains
4. Regulatory domains

Question 16

G proteins are trimers. What does this mean?

Answer 16

They have three parts to their protein structure (alpha, beta, and gamma subunits)

Question 17

In intracellular nuclear receptors, the highest homology is found in what part of the receptor?

Answer 17

DNA binding domain

Question 18

In relation to tyrosine kinase receptors, SH2 domains on proteins allow what?

Answer 18

Proteins to bind to the receptor

Question 19

In relation to G protein-coupled receptors, when activated, what subunit binds to GTP and dissociates from the complex?

Answer 19

The alpha subunit

Question 20

What subunits make up the complex of the G protein-coupled receptors?

Answer 20

The alpha, beta, and gamma subunits