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Human Physiology 1 > Lecture 5 & 6 Questions > Flashcards

Lecture 5 & 6 Questions Flashcards

1
Q

List & define the 4 basic mechanisms of cell to cell communication. Give examples.

A
  1. Gap junctions - which allow direct cytoplasmic transfer of electrical & chemical signals b/t adjacent cells
  2. Contact-dependent signals - which occur when surface molecules on one cell membrane bind to surface molecules on another cell’s membrane
  3. Chemicals that diffuse through the extracellular fluid to act on cells close by (paracrine & autocrine)

Long distance communication (4) uses a combo of chemical & electrical signals carried by nerve cells & chemical signals transported in the blood

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2
Q

If 2 cells are connected by gap junctions, what happens to the second if the first has many more NA+/K+/ATPase

A

i think both would result in having an influx of Na+ and K+ because the cells are connected ??

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3
Q

What’s the difference between paracrine and autocrine?

A

paracrine: signaling to cells in the immediate vicinity
autocrine: signaling to self

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4
Q

Differentiate between a hormone, neurohormone and neurotransmitter. Which ones require action potentials?

A

hormone: are secreted by endocrine glands or cells into the blood
- only target cells with receptors for the hormone respond to the signal

neurohormone: are chemicals released by neurons into the blood for action at distant targets
neurotransmitter: are chemicals secreted by neurons that diffuse across a small gap to the target cell

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5
Q

Why don’t hormones affect all cells once they are released?

A

hormones come in contact with most cells of the body, but ONLY those cells with receptors for the hormone are target cells

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6
Q

What features do all signal pathways have?

A
  1. The signal molecule is a LIGAND that binds to a protein receptor
    - the ligand is also known as a first messenger b/c it brings info to the target cell
  2. Ligand-RECEPTOR binding activated the receptor
  3. The receptor in turn activates one or more INTRACELLULAR signal molecules
  4. The last signal molecule in the pathway creates a response by modifying existing proteins or initiating the synthesis of new proteins
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7
Q

Where are receptors located?

A

receptor proteins are located inside the cell or on the cell membrane
- target cell receptor proteins may be found in the nucleus, in the cytosol, or on the cell membrane as integral proteins

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8
Q

What are major classes of membrane receptors? Give an example of each.

A
  1. Receptor-channel
    - allows Ca2+ into cells
  2. Receptor-enzyme
    ex: tyrosine kinase receptor (TKR or RTK)
  3. G-protein-coupled receptor (GPCR)
    ex: adenylyl cyclase or phospholipase C
  4. Integrin receptor
    ex: binds collagen
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9
Q

List them in order of fastest response to slowest response. Explain your choice.

A

fastest –> slowest

  1. receptor channel
  2. GPCR
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10
Q

What kind of receptors does testosterone bind to?

A

g

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11
Q

Can a receptor be an ion channel?

A

yes - receptor channels are ion channels too ?

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12
Q

What are the 2 main consequences of opening a receptor channel?

A

g

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13
Q

What are the main difference b/t a receptor enzyme & a G-protein coupled receptor? Which is more common. More complicated? Makes 2nd messengers? Shows more amplification?

A

receptor enzymes & GPCR both activate amplifier enzymes

results in signal amplification
- a small amount of ligand creates a large effect (the generation of a large # of intracellular molecules)

receptor enzyme:
- ligand binding to a receptor-enzyme activates an intracellular enzyme

G-protein couple receptors (GPCRs)
- activation of GPCR leads to generation/release of 2nd MESSENGERS
- sometimes the 2nd messengers are synthesized, sometimes they are released from a storage compartment
- small, diffusible (can be hydrophobic, hydrophilic, or a gas)
- stimulate a biological response
*- are a LARGE & COMPLEX family of membrane-spanning proteins that cross the phospholipid bilayer 7 times
*- G proteins linked to amplifier enzymes make up the bulk of all known signal transduction mechanisms
?

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14
Q

What’s an orphan receptor?

A

unknown functions

- b/c we simply don’t know what they do

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15
Q

Describe, in general terms, the process of g-protein coupled receptor signaling.

A

activation of GPCR leads to generation/release of 2nd messengers

  • a 2nd messenger is a signaling molecule synthesized or released by a cell in response to an extracellular signaling molecule (hormone, for ex)
  • -> sometimes they are synthesized, sometimes they are released from a storage compartment
  • small, diffusible (can be hydrophobic, hydrophilic, or a gas)
  • stimuluate a biological response
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16
Q

How many membrane spanning regions does a GPCR protein have?

A

7 MSR

  • very hydrophilic at one end & other end
  • but middle part has hydrophobic part (7 MSR that are hydrophobic)
  • snakes back & forth throughout the membrane
17
Q

Is the G-protein anchored by cytoskeleton? Explain why/why not.

A

the cytoplasmic tail of the receptor protein is linked to the 3-part membrane transducer molecule known as G-protein ?

18
Q

Is the G protein an integral protein?

A

no, it is an peripheral protein ?

19
Q

What is cAMP?

A

a second messenger molecule synthesized by adenylyl cyclase

  • cAMP is a small molecule that diffuses throughout the cell, & activates the PK-A protein kinase
  • some GPCR pathways activate adenylyl cyclase, some inhibit it (allowing the concentration of cAMP in a cell to decrease)
20
Q

Where does cAMP go once its synthesized?

A
  • cAMP is a small molecule that diffuses throughout the cell, & activates the PK-A protein kinase
  • some GPCR pathways activate adenylyl cyclase, some inhibit it (allowing the concentration of cAMP in a cell to decrease)
21
Q

What kinase is linked with cAMP pathway, PKA or PKC?

A

PKA (protein kinase A)

22
Q

Be able to draw the Adenylyl cyclase & PLC pathways, knowing the 2nd messengers & other molecules involved.

A

g

23
Q

Why is arachadonic acid involved in both intracellular & intercellular pathways.

A

dual function:

  1. Are themselves second messengers within a cell
  2. Diffuse out of the cell & act as a ligand for GPCR cell membrane & adjacent cells
24
Q

Imagine a cell is poisoned with a chemical that selectively binds calcium. What processes will a cell be unable to carry out?

A

g

25
Q

Of the 2nd messengers IP3, DAG, AA, which one diffuses throught the cytoplasm, which one diffuses throughout the cytoplasm & out of the cell, which one is associated with the cell membrane.

A

diffuses through(out) the cytoplasm = IP3 (b/c it is a small polar molecule)

diffuses throughout the cytoplasm & out of the cell = AA (are themselves 2nd messengers within a cell & diffuse out of the cell & act as a ligand for GPCR cell membrane & adjacent cels)

associated with the cell membrane = DAG (it’s a glyceride - has f.a. tails that is very lipophilic, likes to stick to the cell membrane so it stays associated, but it can diffuse around side to side but it sticks in the cell membrane)

26
Q

Explain the difference b/t downregulation & desensitization.

A

down-regulation is a decrease in receptor #
- the cell can physically remove receptors from the membrane through endocytosis

a quicker & more easily reversible way to decrease cell response is desensitization, which can be achieved by binding a chemical modulator to the receptor protein
- aka phosphorylation of alpha & beta2 receptors can cause them to have a lower affinity for ligands

27
Q

List the elements necessary for a “response & feedback loop”

A

stimulus –> sensor or receptor –> afferent pathway –> integrating center –> efferent pathway –> target or effector –> response

28
Q

Differentiate b/t positive feedback, negative feedback & feed forward control mechanisms. Give an example of each. Which are homeostatic?

A 
negative feedback:
1. Keeps system NEAR a setpoint
2. Response acts to NEGATE the stimulus
3. Response can RESTORE homeostasis, but cannot prevent the initial pertubation
Homeostatic

positive feedback:
1. Brings a system FURTHER from a setpoint
2. Response acts to REINFORCE the stimulus
3. Requires an outside factor to shut off
Non-homeostatic

feedforward control:

  • a small stimulus sets off a chain of events aimed at PREVENTING a perturbation (change is anticipated…)
  • requires a complex “program,” or a “reflex”
29
Q

Which of these 3 mechanisms is the basis for cruise control on a car? The turbocharger of a car? Maintaining balance & posture? Catching a Frisbee? Fight or Flight response? The neuronal action potential?

A

g

30
Q

Name 3 illnesses or medical conditions that are related to dysfunction of 2nd messenger pathways, or can be treated by manipulating 2nd messenger pathways?

A

g

31
Q

What does a kinase do? Why are they important?

A

kinases transfer a phosphate group from a substrate to an ADP molecule to create ATP, or from an ATP molecule to a substrate

Therefore, kinases are critical in metabolism, cell signalling, protein regulation, cellular transport, secretory processes and many other cellular pathways, which makes them very important to human physiology.

Human Physiology 1 (32 decks)

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