Lecture 8 Flashcards

1
Q

What is signalling transduction

A

Process in which binding of an extracellular messenger to the cell surface receptor is translated into changes in biochemistry, cell biology, and gene transcription that make it possible for the cell to respond to the information that was received

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2
Q

What is amplification

A

An increase in the number of copies of a gene or genome

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3
Q

Does signal transduction use hydrophobic or hydrophilic messangers

A

Hydrophilic (transported through water) messengers

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4
Q

What can the first messanger of signal transduction be

A

The first messenger can be hormones, neurotransmitters, ect

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5
Q

What type of proteins are found in receptors of signal transduction? Give an example of one

A

Several G-Proteins are associated with each receptor
— Ex. guanine nucleotide-binding proteins

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6
Q

What is the second messenger of signal transduction

A

cAMP (cyclic adenosine monophosphate)

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7
Q

What are the 2 roles of cAMP

A

1) Ensuring cascade activation of one protein (protein kinase A) activates another
2) In the cytoplasm, a “kinase” phosphorylates a target and usually uses ATP as a phosphate donor

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8
Q

What are the 2 parts of signalling systems

A

1) Channel-liked receptors (neurotransmitters)
2) Secondary messangers (Ca2+, cGMP)

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9
Q

What are the first 3 steps of hydrophilic messengers

A

1) One messenger binds to one receptor
2) Several G proteins are activated
3) Each G protein activates an adenylate cyclase

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10
Q

What are the last 3 steps of hydrophilic messengers

A

4) Each adenylate cyclase generates 100s of cAMP molecules
—– Phosphodiesterase is the degradation of cAMP very rapidly
—– Used when you need to turn a signal OFF
5) Each cAMP activates a protein kinase A
6) Each protein kinase A phosphorylates hundred of proteins

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11
Q

Signal transduction - explain signal cascading during exercise

A

1) Epinephrine (chemical messenger)
2) Increases cAMP formation
3) Activates Protein kinase A
4) Activates hormone sensitive lipase
5) Activates lipolysis and release of fatty acids to provide fuel during exercise

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12
Q

What are the properties of hydrophilic (or llipophobic) messengers

A

Chemical class: AAs, amines, peptides
Storage in secretory cell: Secretory vesicles
Mechanism of secretion: Exocytosis
Transportation of blood: Disolved
Location of receptor: plasma membrane

Signal transduction mechanism: Open/close ion channels, activate membrane-bound enzymes, G proteins and second messenger systems
Relative time to onset on response: fast
Relative duration of response: short
Relative half life: short

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13
Q

What are the properties of hydrophobic (or lipiphilic) messengers

A

Chemical class: Steroids, eicosanoids, thyroid hormones
Storage in secretory cell: None
Mechanism of secretion: Diffusion
Transportation of blood: Bound to carrier protein
Location of receptor: cytosol or nucleus

Signal transduction mechanism: After transcription of mRNA
Relative time to onset on response: Slow
Relative duration of response: Long
Relative half life: Long

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14
Q

What is neurocrine signalling

A

Chemical signalling facilitated in neurons or nerve cells

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15
Q

Characteristics of neurocrine signalling

A

Sensory cell: neuron
Messenger: neurotransmitter (neurohormone)
Pathway: bloodstream
Target cell: endocrine cells
Specificity: receptors on target endocrine cells
Time to onset: delayed
Direction of effect: longer

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16
Q

Examples of neurocrine signalling

A

1) Norepinephrine released from noradrenergic nerves
2) Antidiuretic hormone released from neurons in anterior pituitary

17
Q

Signalling Characteristics of Nervous System

A

Secretory cell: Neuron
Target cell: Neuron, muscle, gland
Messenger: Neurotransmitter
Pathway for communication : Across synapse

Basis of specificity: Receptors of postsynaptic target cells
Time to onset of effect: Immediate
Duration of affect: Brief

18
Q

Signalling Characteristics of Endocrine System

A

Secretory cell: Endocrine cell
Target cell: Most cell types in body
Messenger: Hormones
Pathway for communication : Via bloodstream

Basis of specificity: Receptors on target cells throughout body
Time to onset of effect: Delayed
Duration of affect: Long

19
Q

Examples of endocrine tissue in the body

A
  • Hypothalamus
  • Anterior pituitary
  • Adrenal glands
  • Pancreas
  • Thyroid
  • Sex organs (ovaries, testis)
  • Kidneys
20
Q

Fluid secretion into the intestinal lumen

A
  • Maintaining normal fluid levels in the lumen is a matter of chloride and sodium secretion
  • Too much loss of fluid can lead to diarrhea
  • Cl- (chloride) and Na+ (sodium) pumps are regulated by protein kinesis (and cAMP)
21
Q

Cholera Toxin and signalling transduction

A
  • Secreted by bacterium vibrio cholerae
  • Cholera grows under the mucus layer of the small intestine
  • The secreted cholera toxin activates G protein for a prolonged period
    —-Signal does not shut of
  • Causes a 20L efflux of Cl-, Na+ and water per day
  • Consequence is life threatening diarrhea
22
Q

What is CFTR

A
  • Cystic fibrosis transmembrane conductance regulator
  • A Cl- transporter
23
Q

How is CF characterized

A

CF is characterized by a homozygous mutation in the CFTR gene

24
Q

What does CF impair

A

—Impairs regulation of sweat, digestive juices and mucus
—— Ie. Leads to thicker secretions and less water loss

25
Q

Explain CF’s relation to Cholera Toxin

A

CF could protect against severe loss of fluid that occurs due to cholera toxin

26
Q

Careers related to biological concepts of health

A
  • Regulated healthcare professional
  • Unregulated healthcare professional
  • Public health
  • Industry
  • Research
  • Education