1 L2 Intro to Cell Signalling and Cell Processes

Question 1

What are the 3 ways that specificity can be achieved in signalling pathways

Answer 1

• Direct contact
• Selective receptor expression
• Degradation/reuptake of signal molecule

Question 2

Name the 4 modes of signalling

Answer 2

Juxtacrine, Autocrine, Paracrine, Endocrine

Question 3

Describe juxtacrine signalling simply

Answer 3

next-to signal

Question 4

What is the alternative name for juxtacrine signalling

Answer 4

Notch pathway

Question 5

What can help to mediate juxtacrine signalling

Answer 5

Gap junctions

Question 6

Name the proteins that compose the gap junctions

Answer 6

Connexins

Question 7

Describe the method and purpose of juxtacrine signalling

Answer 7

It allow ions and small molecules to move between cells - Bidirectional - Provides electrical and chemical coupling between cells - Allows very rapid communication between groups of cells e.g. cardiac muscle cells

Question 8

How does juxtacrine ensure specificity

Answer 8

1. Direct contact
2. Selective receptor expression

Question 9

True or False- Juxtacrine can involve receptors

Answer 9

True

Question 10

What are the characteristics of the signal molecule in juxtacrine

Answer 10

It is not released
It is membrane bound

Question 11

Is juxtacrine more involved with simple or complex information

Answer 11

Complex information

Question 12

Simply describe Autocrine

Answer 12

Self signalling- nearby cells of same type or same cell that’s released it

Question 13

What is the mechanism that Autocrine uses

Answer 13

Release and Reception of signal molecule

Question 14

What function can autocrine signalling do

Answer 14

Can coordinate activity between a group
of similar cells

Question 15

How does autocrine ensure specificity

Answer 15

1. Selective receptor expression
2. Rapid degradation of signal molecule

Question 16

Simply describe Paracrine signalling

Answer 16

Cells closeby to each other (different cell types)

Question 17

What is the mechanism that Paracrine uses

Answer 17

Release and Reception of signal molecule

Question 18

How does paracrine ensure specificity

Answer 18

1. Selective receptor expression
2. Rapid degradation of signal molecule

Question 19

What are the signal molecules used in neuronal signalling

Answer 19

Neurotransmitters

Question 20

Where are neurotransmitters released from

Answer 20

Neurons- specialised
highly localized synaptic sites

Question 21

How does neuronal ensure specificity

Answer 21

1. Precise (direct) contact
2. Rapid removal of neurotransmitter to prevent diffusion

Question 22

Simply describe endocrine signalling

Answer 22

Hormone signalling between distant cells

Question 23

What are the signals in endocrine called and how do they move

Answer 23

Hormones- carried in the blood

Question 24

Where are hormones produced

Answer 24

Endocrine glands, Tissues, Isolated cells

Question 25

How does endocrine ensure specificity

Answer 25

1. Selective receptor expression

Question 26

What type(s) of signalling require selective receptor expression

Answer 26

All types- Juxtracrine, Autocrine, Paracrine, Endocrine

Question 27

What type(s) of signalling require Rapid uptake/degradation of signal

Answer 27

Autocrine, Paracrine, Neuronal

Question 28

What type(s) of signalling require Direct contact

Answer 28

Juxtacrine, Neuronal

Question 29

Ligand defintion

Answer 29

A molecule that binds specifically to another molecule

Question 30

Compare storage of water vs lipid soluble hormones

Answer 30

Water- Can be stored in vesicles within cell Lipid- Cannot be stored in vesicles within cells

Question 31

Compare speed of release and response of water vs lipid soluble hormones

Answer 31

Water- Rapid release (exocytosis) Lipid- Slow response (made on demand)

Question 32

Compare transport of of water vs lipid soluble hormones in blood

Answer 32

Water- Can travel in blood without a carrier Lipid- Travels in blood with carrier protein (may be longer lasting)

Question 33

Compare entry into target cell of water vs lipid soluble hormones

Answer 33

Water- Cannot enter target cell (message transducer via cell surface receptor) Lipid- Can enter target cells by crossing membrane (acts on intracellular receptors- often to directly regulate gene expression)

Question 34

Describe key features of intracellular receptors

Answer 34

Located in cell- Nucleus, Cytoplasm Need lipid soluble ligands Usually alter gene expression

Question 35

What are 3 common types of extracellular receptors

Answer 35

Ion channels GPCR (G protein coupled receptors) Enzyme-linked receptors (cytokines)

Question 36

How do extracellular receptors work

Answer 36

There is a change in membrane conductance which alters protein activity to regulate cellular events

Question 37

Define second messengers

Answer 37

Small molecules/ions that relay signal from receptor to effector protein. Often able to be synthesized/released, and degraded by enzymes

Question 38

Name 2 membrane associated second messengers

Answer 38

Diacylglycerol (DAG) Phosphatidylinositol (PI)

Question 39

Name 4 second messengers that are located in the cytosol

Answer 39

cAMP cGMP Inositol triphosphate (IP3) Ca2+

Question 40

What is the name of the pathway used to 'activate' proteins

Answer 40

Signalling cascade

Question 41

Describe the signalling cascade

Answer 41

Most commonly done through protein kinases. They selectively modify proteins by adding a phosphate to an amino acid on the protein. Requires ATP

Question 42

What is the name for changing a protein after it has been made

Answer 42

Post-translational modification

Question 43

What is the most common Post-translational modification

Answer 43

Phosphorylation- regulated addition of a phosphate which adds a large negative charge that 'activates' the folded protein by causing it to change shape

Question 44

Describe the process of phosphorylation

Answer 44

A phosphate is transferred from ATP to target protein. Phosphates added by protein kinases - Phosphates removed by protein phosphates

Question 45

How are protein kinases categorised

Answer 45

By the amino acid that they target e.g. tyrosine kinase

Question 46

How are protein kinases named

Answer 46

By what activates them e.g. Protein kinase A (PKA) requires cAMP

Question 47

Briefly describe what happens after the receptor receives a signal

Answer 47

Secondary messengers activated - Protein modification e.g. phosphorylation occurs - Cellular response - Signal is terminated

Question 48

What are some examples of cellular responses to protein modification

Answer 48

Change in gene expression, Enzyme activation

Question 49

What are 3 ways the signal can be terminated

Answer 49

Deactivation of pathway Degradation of signalling molecules Feedback sent to stop signal