Week 9 - Cell Signalling

Question 1

What is cell signaling

Answer 1

Process a cell uses to interact with itself, other cells and the environment

Cell signaling involves a signal, the receptor and the effector

Question 2

What are the key elements of cell signalling

Answer 2

• signal
  -receptor
• effector

Question 3

What is the signal in cell signaling

Answer 3

Any molecule, molecule complex or physical stimulus that conveys information from one cell to another to initiates a cellular response

Question 4

What is a receptor in cell signalling

Answer 4

A specialized protein molecule or complex located either on the cell surface, within the cytoplasm or in the nucleus that binds to specific signaling molecules (ligands) and initiates a cellular response
Receptors only connects to specific ligands to cause an effect.

Question 5

What is the effector in cell signaling

Answer 5

A molecule, protein or cellular component that executes or mediates the cellular response triggered by a signaling pathway.

Question 6

What are examples of signals that can activate a receptor

Answer 6

• low blood glucose
• increase in body temperature
• release of neurotransmitter
• detection of a microorganism in the body - pathogen
• lack of red blood cells

Question 7

How is maintaining homeostasis an example of cell signalling

Answer 7

Body temperature is normally 37 degrees and a negative feedback loop is initiated when the temperature changes.

Signal = temperature rising

Receptor = Hypothalamus

Effect = blood vessels dilating, sweating

This results in the heat being loss and body temperature returning to normal.

Question 8

What are ligands

Answer 8

molecule that binds to receptors , thee are the signals.

Question 9

What is signal transduction

Answer 9

Signal Transduction is the process that transmits a signal inside the cell through a series of events. Its a biochemical cascade of different molecules bringing signaled along a pathway.

Question 10

What is post translational modification

Answer 10

This is the covalent modification of proteins after they have been synthesized in translation. Post-translation modification plays a crucial role in regulating protein structure, function, localization and activity.

Question 11

What is a type of post translational modification

Answer 11

Phosphorylation and de-phosphorylation

Question 12

What are the 4 types of receptors

Answer 12

1. Ligand-gated Ion Channels
2. G protein-coupled receptors (metabotropic)
3. Kinase-linked receptors
4. Nuclear receptors

Question 13

What are ligand gated ion channels as a receptor

Answer 13

Ligand binding to ion channel receptors induce conformational changes that open or close the ion channel pore, leading to changes in ion flux across the membrane and alterations in cellular excitability and signaling

• ions will move down the concentration gradient
• they can also generate an action potential

e.g. sodium potassium pump

Question 14

What are G protein-coupled receptors as receptors

Answer 14

Consist of a cell surface receptor coupled to G proteins (guanine nucleotide-binding proteins), which has 7 transmembrane domains.

In the receptor when the ligand binds to the g protein it causes conformational changes which releases the g protein and the alpha and gamma subunits - which move away to activate other targets.

In the receptor the ligand binds to the GPCRs causing conformational changes that activate intracellular signaling pathways mediated by G proteins, leading to the modulation of second messengers (cAMP, calcium ions) and the activation of downstream effectors.

Question 15

What type of receptor can generate a second messenger

Answer 15

G protein coupled receptor

Question 16

Example of a second messenger

Answer 16

cAMP
cyclic AMP

Question 17

What are kinase linked receptors

Answer 17

Also known as enzyme linked-receptors, these receptors are a class of cell surface receptors that possess intrinsic kinase activity in their cytoplasmic domains. When the ligand binds these receptors undergo phosphorylation to other proteins, initiating a intracellular signaling cascade for other pathways.

Question 18

What are nuclear receptors

Answer 18

Receptors which regulate gene expression/translation, by ligand-activated transcription factors, modulating the transcription of target genes involved in various physiological processes.
The ligand acts as a transcription factor, interacting directly with DNA to stimulate transcription to produce mRNA.

Question 19

What are the types of nuclear receptors

Answer 19

Type 1

Receptor in cytoplasm and it undergoes translocation to enter the nucleus

Type 2

Receptor found in nucleus

Question 20

What are the 5 types of signaling

Answer 20

1. Direct signalling (contact dependent)
2. Autocrine Signalling
3. Paracrine Signalling
4. Neuronal Signalling
5. Endocrine signalling

Question 21

What is direct signaling

Answer 21

This signaling occurs when signaling molecules on the surface of one cell interacts directly with receptors on an adjacent cell through physical contact. this type of signaling relies on cell to cell contact and is mediated by membrane-bound ligands and receptors.

This types of signaling is required for coordinated signaling e.g. contraction of the heart - this occurs from molecules passing through gap junctions between heart cells

Question 22

What is autocrine signaling

Answer 22

Autocrine signaling is a type of cell signaling in which a cell secretes signaling molecules that binds to receptors on its own cell surface or neighboring cells of the same type.

Cell signals to itself which initiates changes within the cell (mostly immune responses as it shuts down processes).

Question 23

What is paracrine signaling

Answer 23

Paracrine signaling is a form of cell-cell communication in which a cell secretes signaling molecules (paracrine factors) into the extracellular space (not the blood stream), where they act locally on neighboring cells of a different type.

Signals:

• Cytokines and growth factors
• Neurotransmitters
• Nitric oxide
• Prostaglandins

Question 24

What is neuronal signaling

Answer 24

• Its the process by which neurons transmit electrical and chemical signals to communicate with each other and with target cells, such as other neurons, muscle cells or gland cells.
• The electrical signal travels along the axon which is an excitable cell.
• Releases neurotransmitters

This results in neurotransmitters to be released, which are usually stored in vesicles. These neurotransmitters then bind to the next neuron or target cell.

Neuronal signaling is essential for the functioning of the nervous system, including sensory perception, motor control, cognition, and behavior.

Question 25

Example of neural signaling

Answer 25

serotonin
- Serotonin (5-HT)is released
- Binds to 5-HT receptor (GPCR)
- Modulates mood, sleep, digestion, bone health, blood clotting

Question 26

What is released during neuronal signaling

Answer 26

neurotransmitters

Question 27

What is neuronal signaling an example of

Answer 27

paracrine signaling

Question 28

What is endocrine signaling

Answer 28

Endocrine signaling involves cells releasing signaling molecules called hormones into the bloodstream, which then travel to distant target cells or tissues to elicit a response. This form of signaling allows for long range communication and coordination of physiological processes throughout the body.

Question 29

Example of endocrine signaling

Answer 29

Insulin

1. Insulin binds to enzymatic receptor
2. Triggers movement of GLUT 4 to surface
3. Allows influx of glucose

Question 30

Will a chemical signal produce the same response in all cells that have a receptor for it?

Answer 30

No, it depends on the type of cell - different types of cells will induce different effects even if they bind to the same receptor

e.g. blood glucose. Insulin binding will allow uptake of glucose in all cells, liver cells will also make glycogen