Tut 15 Cell signaling True False

1. 1. The 3 basic stages of cell signalling includes: 1) Ligand-ligand interaction 2) signal transduction 3) cellular response, to relay signals to the cell interior.

• True

• False

Answer explanation

Explanation: 1) Ligand-receptor interaction 2) signal transduction 3) cellular response

1. 2. All receptors are embedded in the cell surface membrane of cells.

• True

• False

Answer explanation

Explanation: Some receptors are embedded in the plasma membrane, while some are found inside the cell (e.g. cytoplasm).

1. 3. Ligands which bind to receptors on the cell surface are hydrophilic / polar in nature and cannot pass through the cell surface membrane of cells.

• True

• False

1. 4. Ligands which bind to receptors in the cytoplasm are hydrophilic / polar in nature and cannot pass through the cell surface membrane of cells.

• True

• False

Answer explanation

Explanation: Ligands which bind to receptors in the cytoplasm are hydrophobic /        non-polar in nature and can pass through the cell surface membrane of cells

1. 5. The ligand enters the receptor as its shape is complementary in shape to that of the active site of the receptor.

• True

• False

Answer explanation

Explanation: The ligand enter the receptor as its shape is complementary in shape to that of the ligand binding site of the receptor. (note: not all receptors are enzymes. For receptors that are also enzymes e.g. receptor tyrosine kinases, they usually have an active site which is not the same as their ligand binding site)

1. 6. Phosphorylation cascades involve kinase enzymes which adds phosphate groups to other cell signalling proteins to activate them.

• True

• False

1. 7. In cell signalling pathways, signal amplification can be observed, where ligand molecules get increased.

• True

• False

Answer explanation

Explanation: signal amplification means the number of activated molecules at each consecutive step of the pathway increases. E.g. 1 ligand molecule, can lead to 10 molecules of activated protein kinase.

 

 

1. 8. Differentiation of cells after stem cell asymmetrical division; uncontrolled cell division, are examples of cellular responses.

• True

• False

1. 9. G protein linked receptors (GPLR) are made up of  7 separate polypeptide chains that spans the membrane 7 times.

• True

• False

Answer explanation

Explanation: GPLR consists of only 1 polypeptide chain which folds itself into 7 transmembrane domains.

1. 10. GPLR is a G protein.

• True

• False

Answer explanation

Explanation:

 

GPLR is a receptor that interacts with the G protein.