Introduction to Cell Signalling

Question 1

Signal transduction is the process…

Answer 1

By which one type of signal is converted into another

Question 2

Extracellular signal molecules bind to:

(2)

Answer 2

1. The cell-surface receptors
2. Intracellular receptors

Question 3

The cell-surface receptors

Answer 3

• Bind to large and hydrophilic molecules
• Generate molecules within the cell

Question 4

Intracellular receptors

Answer 4

• Bind to small hydrophobic signal molecules
• The molecule bonds in the cytosol or the nucleus
• Regulate gene transcription or other functions

Question 5

Large hydrophilic vs small hydrophobic

Answer 5

Small hydrophobic molecules can pass through the plasma membrane

Question 6

Every cell type displays a set of receptor proteins that enables it to…

Answer 6

…respond to a specific set of extracellular signal molecules produced by other cells.

Question 7

If deprived of the necessary survival signals most cells undergo…

Answer 7

… a form of cell suicide known as apoptosis.

Question 8

Cell-surface receptors relay extracellular signals via…

Answer 8

…intracellular signalling pathways

Question 9

Intracellular signalling pathways are mediated by…

Answer 9

… a series of intracellular signaling molecules.

Question 10

Intracellular signaling molecules

Answer 10

• Can be proteins or small messenger molecules
• Mediate intracellular signaling pathways
• Interact with specific effector proteins, altering them

Question 11

Feedback in intracellular signaling proteins modulate…

Answer 11

…many of the steps in the signalling process

Question 12

Why are some proteins held in close proximity by a scaffold protein?

Answer 12

Because it allows them to be activated at a specific location in the cell and with greater speed, efficiency and selectivity

Question 13

Which cell responses occur slowly?

Answer 13

Ones that require changes in gene expression and the synthesis of new proteins.

Such as cell differentiation or increased cell growth.

Question 14

Which cell responses occur more quickly?

Answer 14

Ones that do not involve gene expression.

Such as cell movement, secretion or metabolism.

Question 15

Types of extracellular signalling

(4)

Answer 15

1. Endocrine
2. Paracrine
   3.Neuronal
   4.Contact-dependent

Question 16

Endocrine signalling

Answer 16

Hormones produced in endocrine glands are secreted into the bloodstream and distributed throughout the body.

Question 17

Paracrine signalling

Answer 17

Paracrine signals are released by cells into the extracellular fluid in their neighbourhood and act locally.
Local mediators

Question 18

Neuronal Signalling

Answer 18

Neuronal signals are transmitted electrically along a nerve cell axon. When this electrical signal reaches the nerve terminal, it causes the release of neurotransmitters onto adjacent target cells.
Very small distance

Question 19

Contact-dependent signalling

Answer 19

A cell-surface-bound signal molecule binds to a receptor protein on an adjacent cell.
Must be in direct contact

Question 20

Many of the same types of signal molecules are used for endocrine, paracrine, and neuronal signaling. The crucial differences lie in …

Answer 20

…the speed and selectivity with which the signals are delivered to their targets—and the distance they must travel.