Basic cell Signaling 1-16

Question 1

Example of a fight or flight response:

Answer 1

Pancreatic cells release insulin to tell muscle cells to take up sugar from the blood for energy

Question 2

What is cell signaling?

Answer 2

cell signalling is part of a complex system of communication to control and maintain normal physiological balance within the body and coordinates cell actions

Question 3

What is the importance of cell signalling?

Answer 3

control and maintain normal physiological balance within the body and coordinates cell actions

Question 4

Activation of different signalling pathways leads to diverse physiological responses such as….

Answer 4

1. Cell proliferation
2. Cell death
3. Cell differentiation
4. Tissue repair
5. Immunity
6. Metabolism

Question 5

Explain the process of Cell Signalling:

Answer 5

1. Signal (stimulus)
2. Receptor
3. Transduction
4. Response
5. Cell proteins called receptors detect the stimulus or signal
6. Once a receptor protein receives a signal, it undergoes a conformational change, which in turn launches a series of biochemical reactions within the cell
7. These intracellular signalling pathways, called signal transduction cascades, typically amplify the message
8. The final effect is to trigger a cell’s response, such as the activation of gene expression

Question 6

What is the purpose of the intracellular signalling?

Answer 6

Amplify the message

Question 7

List the 4 types of cell signalling:

Answer 7

1. Endocrine signalling
2. Autocrine signalling
3. Paracrine signalling
4. Direct cell-cell contact

Question 8

Explain the characteristics of endocrine signalling:

Answer 8

Long-distance endocrine signalling,
signals (hormones) produced by endocrine glands are released in the bloodstream which carries them to target cells in distant parts of the body

Types of hormones:
-Peptide hormones, steroid hormones

Question 9

Explain the characteristics of Paracrine signalling:

Answer 9

(Neighboring signalling)
Signal molecule only affects target cells in the proximity of the signalling cell

A unique example is the conduction of an electric signal from one nerve cell to another nerve cell or to a muscle cell. (Synapse communication) In this case the signalling molecule is a neurotransmitter

Question 10

Explain the characteristics of Autocrine signalling:

Answer 10

(Self signalling)

A cell signals itself, releasing a ligand that binds to receptors on its own surface

Question 11

Explain the characteristics of Direct cell-cell signalling:

Answer 11

Tiny channels that directly connect neighbouring cells.

These water filled channels allow small signalling molecules, called intracellular mediators to diffuse between the 2 cells

Small molecules such as electrolytes (Ca2+, K+, Na+), are able to move between cells, but large molecules like proteins cannot fit through the channels without special assistance

Question 12

Give an example of an intracellular mediator:

What can pass through and what cannot?

Answer 12

Small molecules such as electrolytes (Ca2+, K+, Na+), are able to move between cells, but large molecules like proteins cannot fit through the channels without special assistance

Question 13

Define receptor and ligand:

Answer 13

Receptor-protein molecule that receives chemical signals from outside a cell

Ligand: Signal molecule that binds to a receptor

Question 14

What happens when a ligand binds to a receptor?

Answer 14

Results in a conformational change

Binding of a ligand to a receptor changes the shape or activity of a receptor, allowing it to transmit a signal or directly produce a change inside of the cell

Question 15

What are the 2 types of receptors?

Answer 15

1. Intracellular receptor- found inside of the cell (in the cytoplasm or nucleus)
2. Cell surface receptors, which are found in the cell membrane

Question 16

Describe the characteristics of ligands of intracellular receptors:

Give an example of one

Answer 16

Small and hydrophobic molecules

Primary receptors for hydrophobic steroid hormones, such as the sex hormones estradiol (an estrogen)

Question 17

Name the 3 main kinds of cell surface receptors:

Answer 17

1. Channel linked receptors
2. Enzyme linked receptors
3. G protein-coupled receptors

Question 18

What is the function of membrane anchored proteins?

Answer 18

Bind to ligands outside the cell

Ligand does not need to cross the cell membrane. So, the chemical structure of ligands are more diverse

Question 19

What is Signal transduction?

Answer 19

Describes the process of converting external signals (e.g hormones, growth factors, neurotransmitters) to a specific internal cellular response (gene expression, cell division, cell death)

The receptors trigger a biochemical chain of events (signalling cascade) inside the cell eventually lead to a response

Question 20

Common goal of signalling pathways

Answer 20

To produce a cellular response

Question 21

Give examples of a cell response:

Answer 21

1. Control of gene expression

2. Changes in cell metabolism

Question 22

Cellular response types
At the molecular level
At the macroscopic level

Answer 22

Molecular level-changes such as an increase in specific gene (transcription), changes in activity of particular enzymes

Macroscopic level- changes in outward behaviour or appearance of the cell, such as cell growth or cell death, that are caused by the molecular changes

Question 23

What is gene expression?

Answer 23

process in which information from a gene is used to produce a functional product, typically a protein
Only a fraction of the genes in a cell are expressed at any one time

Question 24

To live, cells must be able to respond to changes in their environment. Regulation of the two main steps…

Answer 24

Transcription and translation is critical to this adaptability

Question 25

Example of cell response to growth factors:

Answer 25

control of gene expression

changes in cell metabolism

Question 26

How does the cell know what gene to express, which gene to turn on and off ?

Answer 26

Precise signalling and cell communication is crucial in order to express which genes to turn on and off

So our body can coordinate to benefit the organism as a whole

Question 27

What is cellular metabolism?

Answer 27

Some signalling pathways produce a metabolic response

Metabolic enzymes in the cell become more or less active

Question 28

Give an example of cellular metabolism:

Answer 28

Epinephrine binds to its receptor on a muscle cell-> triggers a signal transduction cascade involving production of cyclic AMP (cAMP)

This cascade leads to phosphorylation of two metabolic enzymes that is, addition of a phosphate group causing a change in the enzymes’ activities

Question 29

Summary of basic cell signalling:

Answer 29

1. Reception: the signal molecule is detected when the ligand binds to the receptor
2. Transduction: Receptor protein changed which initiates a series of biochemical events involving many intracellular signalling proteins
3. Response: the stage where the signal finally triggers a specific cellular response