WEEK 8 (Cell signalling)

Question 1

With respect to their surrounding membrane system, which is the odd one out?
a) Nucleus
b) Endoplasmic reticulum
c) Mitochondria
d) Chloroplasts

Answer 1

Endoplasmic Reticulum

Question 2

Which of the following proteins is a transmembrane protein responsible for anchoring the extracellular matrix (ECM)?
a) Laminin
b) Fibronectin
c) Integrins
d) Collagen

Answer 2

Integrins

Question 3

What is the key role of fibroblasts?

Answer 3

Producing extracellular matrix

Question 4

Which type of endomembrane secretion occurs in nerve cells?
a) constitutive
b) regulatory
c) non-continuous
d) intermittent

Answer 4

Regulatory

Question 5

Which of the following biomolecules are contained in the lysosomes?
a) nucleic acids
b) ribonucleic acids
c) proteins
d) polysaccharides

Answer 5

Proteins

Question 6

What happens in anaphase 1?

Answer 6

Each homolog reaches the opposite pole

Question 7

There exists attraction between the homologs in Metaphase 1? (TRUE/FALSE)

Answer 7

FALSE

EXPLANATION: The homolog’s centromeres repel each other which assist separation to opposite pole

Question 8

What is the function of axonemal dynein?

Answer 8

Responsible for the beating of flagella and cilia

Question 9

What can Ehlers-Danlos Syndrome affect?

Answer 9

The production or organisation of collagen which is a critical component of connective tissue

Question 10

What applies to both eukaryotic cell walls and animal cell extracellular matrices?

Answer 10

• They are built to a common overall structure that can be described as ‘fibres in a matrix’
• Their protein components are synthesised by ribosomes of the rough endoplasmic reticulum

Question 11

Bacterial and eukaryotic cell walls have the same general function (TRUE/FALSE)

Answer 11

TRUE

EXPLANATION: The cell walls of bacteria and eukaryotic cells have the same general function of preventing cell lysis in hypotonic environments

Question 12

What applies to fibronectins?

Answer 12

• They are disulphide linked dimers with each polypeptide composed of a number of binding domains joined together by short flexible segments
• They have an essential role in linking the extracellular matrix to its underlying cells

Question 13

Glycosaminoglycans contribute to two of the tissue properties: withstand mechanical pressures and favour the movement of cells and molecules through tissues (TRUE/FALSE)

Answer 13

TRUE

Question 14

The Elasticity of bones is partially provided by collagen fibers (TRUE/FALSE)

Answer 14

TRUE

Question 15

Chronic pain is usually localised to the hyper mobile joints is a symptom of which disease?

Answer 15

Ehlers Danlos Syndrome (EDS)

Question 16

What does cell signalling allow?

Answer 16

Cells to perceive and respond to extracellular environment allowing development, growth and immunity

Question 17

What are the three stages of cell signalling?

Answer 17

1) RECEPTION = signal molecule binds the receptor
2) SIGNAL TRANSDUCTION = chemical signal results in a series of enzyme activations
3) RESPONSE = resulting cellular responses

Question 18

How do cells usually communicate with each other?

Answer 18

Through extracellular messenger molecules

Question 19

How do cells usually communicate with each other?

Answer 19

Through extracellular messenger molecules

Question 20

How do extracellular messengers travel?

Answer 20

• SHORT DISTANCE and stimulate cells that are in close proximity to the origin of the message
• LONG DISTANCE stimulating cells that are far away from the source

Question 21

What are the four types of chemical signalling?

Answer 21

• Endocrine signalling
• Paracrine signalling
• Neuronal signalling
• Contact-dependent signalling

Question 22

What happens in Endocrine/Hormonal/Long-distance signalling?

Answer 22

Specialised cells release hormone molecules which travel to target cells elsewhere in the organism

Question 23

What happens in Paracrine/Short-distance signalling?

Answer 23

Rather than entering the bloodstream, the signal molecules diffuse locally through the extracellular fluid, remaining in the neighborhood of the cell that secretes them.

Question 24

What happens in Autocrine signalling?

Answer 24

The cell that is producing the messenger expresses receptors on its surface that can respond to the messenger that it itself produces -> Cells releasing the message stimulate or inhibit themselves

Question 25

What happens in neuronal signalling?

Answer 25

A message is delivered quickly and specifically to individual target cells -> A neuron is activated by signals from the environment or from other nerve cells -> A neuron sends electrical impulses along its axon -> Once reaching the exon terminal, the electrical signal are converted into a chemical form

Question 26

What happens in neuronal signalling?

Answer 26

A message is delivered quickly and specifically to individual target cells -> A neuron is activated by signals from the environment or from other nerve cells -> A neuron sends electrical impulses along its axon -> Once reaching the exon terminal, the electrical signal are converted into a chemical form

Question 27

What happens in Contact-dependent signalling?

Answer 27

A cell surface bound signal molecule binds to a receptor protein on an adjacent cell

Question 28

What is contact dependent signalling important in?

Answer 28

- Development - Immune responses

Question 29

What happens in Lateral inhibition?

Answer 29

Each future neuron delivers an inhibitory signal to the cells next to it deterring them from specialising as neurons too

Question 30

What are the different signalling components?

Answer 30

- Signalling molecules - Receptors - Signalling intermediates - Effector proteins

Question 31

What is the difference between First messengers and Second messengers?

Answer 31

- FIRST MESSENGERS = extracellular factors (often hormones/neurotransmitters) - SECOND MESSENGERS = intracellular signalling molecules released by the cell in response to exposure to extracellular signalling molecules

Question 32

What are signalling molecules?

Answer 32

Molecules that are responsible for transmitting information between cells in your body

Question 33

What are receptors?

Answer 33

- Proteins associated with cell membrane or located within the cell - Recognise signalling molecules by binding to them - Binding of receptors by signalling molecules causes cell behaviour changes

Question 34

Describe Myasthenia Gravis

Answer 34

Myasthenia gravis is a long-term neuromuscular disorder that's usually caused by an autoimmune problem which leads to varying degrees of skeletal muscle weakness. Most commonly affected muscles are eyes, face and swallowing. DEFICIENCY: acetylcholine SYMPTOMS: - difficulty breathing - difficulty swallowing/chewing - facial paralysis - problems walking up stairs/lifting objects -droopiing of eyelids [severity of symptoms increases over time if left untreated]

Question 35

How do signal molecules work to regulate the behaviour of the cell?

Answer 35

Every cell type displays a set of receptor proteins that enables it to respond to a specific set of extracellular signal molecules produced by other cells -> the signal molecules work I combinations to regulate the behaviour of the cell

Question 36

What are the two classes of Extracellular signal molecules?

Answer 36

- Molecules that are TOO LARGE or TOO HYDROPHILIC to cross the plasma membrane - Molecules that are SMALL ENOUGH or HYDROPHOBIC ENOUGH to pass through the plasma membrane

Question 37

Some small hydrophobic hormones binds to intracellular receptors that act as ______________________________

Answer 37

Transcription regulators

Question 38

Describe how Cortisol acts

Answer 38

1) Cortisol cross the plasma membrane and a conformational change activates the receptor protein 2) Activated receptor-cortisol complex moves into the nucleus 3) Activated receptor-cortisol complex binds to regulatory region of target gene and activates transcription

Question 39

Describe how acetylcholine causes the blood vessel to dilate

Answer 39

Acetylcholine binds to receptors on the surface of endothelial cells which stimulates cells to make and release NO -> NO is synthesised from the amino acid arginine and diffuses readily from its site of synthesis into adjacent smooth muscle cells -> NO regulates the activity of specific proteins causing the muscle cells to relax

Question 40

What does NO activate in smooth muscle cells

Answer 40

GUANYLYL CYCLASE [catalyses the production of cyclic GMP from GTP]

Question 41

What are the functions of intracellular signalling pathways?

Answer 41

- RELAY the signal onward and spread it through the cell - AMPLIFY the signal received making it stronger - can detect signals from more than one intracellular signalling pathway and INTEGRATE them before relaying a signal onward - DISTRIBUTE the signal to more than one effector protein

Question 42

What are the two classes that proteins that act as molecular switches fall into?

Answer 42

- Proteins that are activated or inactivated by phosphorylation - GTP-binding proteins

Question 43

What switches the GTP-binding protein on and off?

Answer 43

GUANINE NUCLEOTIDE EXCHANGE FACTORS (GEFs) promote the exchange of GDP or GTP switching the GTP-binding protein ON GTPASE-ACTIVATING PROTEINS (GAPs) stimulate the hydrolysis of GTP to GDP switching the GTP-binding protein OFF

Question 44

What are the three different classes of cell-surface receptors which differ in the transduction mechanism?

Answer 44

- Ion-channel-coupled receptors - G-protein-coupled receptors - Enzyme-coupled receptors

Question 45

What is the function of all cell-surface receptor proteins?

Answer 45

They bind to an extracellular signal molecule and transduce its message into one or more intracellular signalling molecules that alter the cell's behaviour

Question 46

Describe Ion-channel-coupled receptors

Answer 46

They change the permeability of the plasma membranes to selected ions such as Na+, K+ or Ca2+ altering the membrane potential and producing an electrical current

Question 47

What are transmitter-gated ion channels?

Answer 47

Ion-channel-coupled receptor that opens in response to binding an extracellular signal molecule

Question 48

What happens when a G-protein-coupled receptor binds its extracellular signal molecule?

Answer 48

The activated receptor signals to a G protein on the opposite side of the plasma membrane which turns on or off an enzyme in the same membrane