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MOLECULAR BIOLOGY > WEEK 11 (Cell Signaling) > Flashcards

WEEK 11 (Cell Signaling) Flashcards

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1
Q

What does Cell signalling allow cells to do?

A

Respond in an appropriate manner to a specific environmental stimulus by allowing development, growth and immunity

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2
Q

How do budding yeast cells respond to mating factor?

A
  • Cells are normally spherical
  • Put out a protrusion towards the source of the mating factor in preparation for mating
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3
Q

What are the three stages of Cell signalling?

A

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

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4
Q

Cells usually communicate with each other through which molecules?

A

Extracellular chemical messenger molecules

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5
Q

What are the properties of Extracellular messengers?

A
  • Can travel a SHORT DISTANCE and stimulate cells in CLOSE PROXIMITY to the origin of the message
  • Can travel THROUGHOUT THE BODY stimulating cells FAR AWAY from the source
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6
Q

What are the four categories of Chemical signalling in multicellular organisms?

A
  • Endocrine signalling
  • Paracrine signalling
  • Neuronal signalling
  • Contact-dependent signalling
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7
Q

What happens in Endocrine signalling?

A

Endocrine/Hormone signalling is when specialised cells release hormone molecules which travel, usually by diffusion/through the circulatory system, to target cells elsewhere in the organism

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8
Q

What happens in Paracrine signalling?

A

Signal molecules diffuse locally through the extracellular fluid, remaining in the neighbourhood of a cell that secretes them

[Important in REGULATING INFLAMMATION and controlling CELL PROLIFERATION]

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9
Q

How are Paracrine signals important during development?

A

They allow one group of cells to tell a neighbouring group of cells what cellular identity to take on

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10
Q

What happens in Autocrine signalling?

A

The cell that is producing the messenger expresses receptors on its surface that can respond to that messenger. This causes the cells releasing the message to stimulate/inhibit themselves

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11
Q

What happens in Neuronal signalling?

A

When activated by signals from the environment or from other nerve cells, a neuron sends electrical impulses along its AXON. Once reaching the AXON TERMINAL, the electrical signals are converted into chemical form; Each electrical impulse stimulus the nerve terminal to release a NEUROTRANSMITTER

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12
Q

What differentiates Neuronal signalling to Endocrine signalling?

A
  • Message is not broadcasted widely
  • Delivered quickly
  • Delivered specifically to individual target cells through private cells
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13
Q

What do Neurons and Hormones both have in common?

A

They can both deliver messages over long distances

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14
Q

What happens in Contact-dependent signalling?

A

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

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15
Q

What is distinguishable about Contact-dependent signalling?

A
  • Doesn’t require the release of a secreted molecule
  • Cells make direct physical contact through signal molecules lodges in the plasma membrane of the signalling cell and receptor proteins embedded in the plasma membrane of the target cell
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16
Q

When is Contact-dependent signalling important?

A

Development & Immune responses

17
Q

What is lateral inhibition?

A

When a specialised neuron delivers an inhibitory signal to the cells next to it, deterring them from specialising too

18
Q

What are the signalling components?

A
  • Signalling molecules
  • Receptors
  • Signalling intermediates
  • Effector proteins
19
Q

What is the difference between First messengers and Second messengers?

A

First messengers are Extracellular factors (hormones etc)

Second messengers are Intracellular signalling molecules released by the cell in response to exposure to extracellular signalling molecules (cAMP etc)

20
Q

What are Signalling molecules?

A

Molecules that are responsible for transmitting information between cells in your body. The size, shape and function vary.

21
Q

What are Receptors?

A

Receptors are proteins associated with cell membranes or located within the cell and recognise signalling molecules by binding to them. Binding of receptors by signalling molecules changes cell behaviour.

22
Q

What is an example of a single signal molecule inducing different responses in different target cells?

A

Acetylcholine

  • Decreases rate of firing in a heart pacemaker cell
  • Secretion in a salivary gland cell
  • Contraction in a skeletal muscle cell
23
Q

What is Myasthenia Gravis?

A

A long-term neuromuscular disorder that’s usually caused by an autoimmune problem which leads to varying degrees of skeletal muscle weakness
(mostly affects EYES, FACE and SWALLOWING)

SYMPTOMS:
- Facial paralysis
- Speech difficulties
- Difficulty breathing
- Fatigue
- Drooping eyelids
- Double vision

Severity of symptoms vary and increase over time if left untreated

24
Q

What happens when cells are deprived of survival signals?

A

Most cells undergo APOPTOSIS

25
Q

What are the two classes that Extracellular signal molecules fall into?

A
  • HYDROPHILIC SIGNAL MOLECULES - too large or too hydrophilic to cross the plasma membrane
  • HYDROPHOBIC SIGNAL MOLECULES - small enough or hydrophobic enough to pass through the plasma membrane
26
Q

What do small hydrophobic hormones bind to?

A

Intracellular receptors that act as transcription regulators

27
Q

What is Cortisol?

A
  • One of the hormones produced by the adrenal glands in response to stress
  • A steroid hormone that acts by activating a transcription regulator
28
Q

Describe how Cortisol works?

A

1) Cortisol diffuses across the plasma membrane and binds to a NUCLEAR RECEPTOR PROTEIN in the cytosol which causes a CONFORMATIONAL CHANGE which activates the receptor protein
2) Activated receptor-cortisol complex moves into nucleus
3) Activated receptor-cortisol complex binds to regulatory region of target gene and activates transcription

29
Q

Describe how Nitric Oxide (NO) triggers smooth muscle relaxation in a blood-vessel wall

A
  • Acetylcholine causes the blood vessel to dilate by binding to receptors on the surface of ENDOTHELIAL CELLS, stimulating the cells to make and release NO
  • NO is synthesised from ARGININE and diffuses readily from its site of synthesis into adjacent smooth muscle cells, where it regulates the activity of specific proteins, causing the muscle cells to relax
30
Q

What is one key target protein that can be activated by NO in smooth muscle cells?

A

GUANYLYL CYCLASE

It catalyses the production of cyclic GMP from GTP

31
Q

What are the three main classes of Cell-surface receptors?

A
  • Ion-channel coupled receptors
  • G-Protein-Coupled receptors
  • Enzyme-coupled receptors

MOLECULAR BIOLOGY (11 decks)

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