Lecture 14

Question 1

Whats a signal transduction path

Answer 1

It converts a signal at a cells surface into a specific cellular response.
Or it is the process where one type f signal is converted to another
Eg - an extracellular signal converted to an intracellular signal through transmembrane receptors.

Question 2

Flight and fight signal is by which molecule

Answer 2

Epinephrine

Question 3

How can one signal create more than one response.

Answer 3

The signal can target a different target cell to produce different response

Question 4

What is the importance of signalling

Answer 4

Signals for cell division and differentiation help them stay alive and functioning.
Gene expression and protein activity in response to environmental signals.
Communication between cells of organism, single and multicelled
Allows cells to adapt to the environment

Question 5

Describe the communication in a yeast cell

Answer 5

The yeast has 2 mating factors a and ā
Mating occurs between a and ā
Each type secrete a specific type of mating factor that binds to the other types if mating factor
This help locate each other 
Mate

Question 6

What happens if yeast mates with a wrong mate

Answer 6

They are usually spherical but will extend a protrusion toward the source of the factor.

Question 7

State the general principles of cell signalling.

Answer 7

Signals can act over a long or short range
Limited set of extracellular signals can produce a huge variety of response
A cells response to a signal can be fast or slow
Cell - surface receptors relay extracellular signals via intracellular signalling pathways
Some intracellular signalling proteins act as molecular switches
Cell surface RECEPTORS fall into three main classes.

Question 8

Which type of signals do animals use to communicate mostly ? Extracellular or intracellular ?

Answer 8

Extracellular most of the time,

Question 9

What are the two types of signalling molecules

Answer 9

1- contact dependent signalling.

2- local cell signalling between nearby cells.

Question 10

Examples of Contact dependent signalling

Answer 10

A- cell junctions

B- cell cell recognition

Question 11

Examples of local cell signalling between nearby cells

Answer 11

A- paracrine signalling
B- endocrine signalling
C- neuronal/ synapting signalling

Question 12

Cell junctions

Answer 12

junctions btw adjacent cells that directly pas signalling molecules .
Animals- cell junction
Plants - plasmodesmata btw cell wall

Question 13

Cell cell recognition

Answer 13

Animal cells communicate via membrane bound cell surface proteins/ receptors
eg - immune response, embryonic development , blood groups antigens and antibodies.

Question 14

Difference between cell signalling and cell cell recognition

Answer 14

A- In cell signalling a signalling molecule is secreted however in the cell cell recognition signalling molecule is attached to the cell membrane.
B- signal molecule on one membrane and receptor on another.

Question 15

Similarities between cell cell recognition and cell signalling

Answer 15

Both
1- immediate neighbours /adjacent cells
2- direct contact

Question 16

Local signalling between nearby cells

Answer 16

A- paracrine signalling
B- endocrine signalling
C- neuronal signalling

Question 17

A- Paracrine signalling

Answer 17

Special cell- secreting cells
Secretes- local regulators
Via- extracellular
Distance- at short distances

Eg - growth factor

Question 18

B- endocrine signalling

Answer 18

Special cells- secretory glands
Secretes - hormones 
Via- blood and lymph
Distance- longer
Eg - plant growth regulator, insulin

Question 19

C- neuronal synaptic signalling

Answer 19

Special cells- neurone cells
Secrete - neurotransmitter 
Via - synapse 
Distance - longer 
Eg - nerve to nerve or nerve to muscLe cells

Question 20

Which of the signals are electric

Answer 20

Neuronal signalling

Question 21

Describe a bit about neuron signalling

Answer 21

Neuronal signal are transmitted electrically along an exon
When they reach the terminal they release a neurotransmitter in the synapse
That then binds to the receptor on the post neural cell

Question 22

List the 
Site of origin
Chemical nature 
Response 
Of epinephrine

Answer 22

Epinephrine
Site of origin - adrenal gland
Chemical nature- derivative of amino acid tyrosine
Response- increases blood pressure, heart rate and metabolism

Question 23

List the 
Site of origin
Chemical nature 
Response 
Of insulin

Answer 23

Site of origin - B cells of pancreas
Chemical nature- protein
Response- stimulates glucose uptake , protein synthesis, lipid synthesis in many cell types

Question 24

What type of signalling molecule binds to cell surface receptors

Answer 24

The signals molecules that bind to cell surface receptors are called extracellular signals
Hydrophilic and large Binds to the receptor
Stimulating 1 or 2 more intracellular signals

Question 25

What type of signalling molecule binds to the intracellular receptors?

Answer 25

Small and hydrophobic eg steroids- cytosol
They also acts as molecular switches to gene express
And the intracellular receptor acts as transcription reg

Question 26

Same signalling molecule can bring about different response if bound to different target molecules. Give an example of acetylcholine

Answer 26

Binds to pacemaker cells - dec rate of firing

Binds to salivary gland - secretion

Question 27

In animal cells , extracellular also work in comb to bring about some response ,briefly explain and give example

Answer 27

A cell may require more then one signal to survive( eg A,B,C)
Addition signals require to grow and divide (eg A,B,C,D, E)
Addition signals required to differentiate. ( eg A,B,C,D,E,F)

Question 28

Many responses can occur fast and many occur slow , give examples of fast and slow responses

Answer 28

It really depends on if the response requires a change in gene expression bcz requires
- activation of transcription factors
- binds to gene
- formation of protein
If yes eg cell growth, division or differentiation - slow
If no eg movement secretion , metabolism - fast