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Phisiology Hope > Cell Transport and Signalling > Flashcards

Cell Transport and Signalling Flashcards

1
Q

♣ Also called plasma membrane
♣ 8 to 10 nm thick
♣ a phospholipid bilayer
♣ barrier against movement of water molecules and water-soluble substances

A

Cell Membrane

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2
Q

♣ Cell membrane is composed of phospholipid bilayer

♣ It is fluid-like

A

Fluid Mosaic Model

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3
Q

♣ Lipid-soluble substances diffuse easily

♣ Water and water-soluble substances passes through transport proteins

A

Membrane Transport

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4
Q

allow free movement of water and selected ions

A

Channel Proteins

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5
Q

conformational change to transport molecules

A

Carrier Proteins

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6
Q
  • random movement of substance through intermolecular spaces or in combination with a carrier
  • Normal kinetic motion of matter
  • “downhill”
A

Passive Transport

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7
Q
  • Movement across the membrane in combination with a carrier protein
  • against the concentration gradient
  • Requires additional energy
  • “Uphill”
A

Active Transport

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8
Q

♣ simple movement though the membrane
♣ caused by the random motion or kinetic movement of the molecules
♣ cell membrane pores
♣ lipid matrix of the membrane (for lipid soluble substances)

A

Diffusion

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9
Q

♣ Occurs downhill from an electrochemical gradient
♣ Via membrane opening or intermolecular spaces
♣ No interaction with carrier proteins
♣ Governed by Fick’s Law of Diffusion

A

Simple Diffusion

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10
Q

The rate of diffusion is determined by

A
  • the amount of substance
  • velocity of kinetic motion
  • number and sizes of openings
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11
Q

Predicts the rate of diffusion of molecules across a biological membrane

A

Fick’s Law of Diffusion

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12
Q

According to Fick’s Law, diffusion is_________ at higher concentration gradients

A

Fast

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13
Q

According to Fick’s Law, diffusion is _______ at higher permeability

A

Fast

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14
Q

According to Fick’s Law,diffusion is _______ at higher areas for diffusion

A

Fast

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15
Q

According to Fick’s Law, diffusion is ______ when diffusing membrane is thicker

A

Slow

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16
Q

2 important characteristics of Simple Diffusion

A
  1. selectively permeable

2. Voltage or ligand -gated channels

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17
Q

♣ molecular conformation of the gate or of its chemical bonds responds to the electrical potential across the cell membrane; Eg Na and K Pump

A

Voltage-Gated Channels

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18
Q

♣ Also called chemical gating
♣ Channels are opened by a chemical substance with the protein
♣ Causes conformational/structural change in the channel
♣ Example: Acetylcholine Channel

A

Ligand-Gated Channels

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19
Q

♣ Also called uniport
♣ Occurs downhill from an electrochemical gradient
♣ Does not require metabolic energy (passive)
♣ More rapid than simple diffusion
♣ carrier-mediated process
♣ NOT governed by Fick’s law of diffusion

A

Facilitated Diffusion

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20
Q

♣ Net movement of water through a semipermeable membrane caused by a concentration

A

Osmosis

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21
Q

homogeneous mixture composed of two or more substances

A

Solution

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22
Q

undergoes diffusion from an area of high solute concentration to an area of low solute concentration.

A

Solute

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23
Q

undergoes osmosis from an area of low solute concentration to an area of high solute concentration.

A

Solvent

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24
Q
  • concentration of all osmotically active
    particles (osmoles) per liter of solution (osmol/L)
  • colligative property that can be measured by freezing point depression
A

Osmolarity

25
Q
  • concentration of all osmotically active particles (osmoles) per kg of solvent (osmol/kg)
  • determines osmotic pressure between solutions
A

Osmolality

26
Q

Two solutions that have the same osmolarity

A

Isosmotic

27
Q

Solution with the higher osmolarity

A

Hyperosmotic

28
Q

Solution with the lower osmolarity

A

Hyposmotic

29
Q
  • The exact amount of pressure required to stop osmosis
  • pressure which needs to be applied to a solution to prevent the inward flow of water across a semipermeable membrane
  • calculated using Van’t Hoff’s Law
A

Osmotic Pressure

30
Q

Van’t Hoff’s Law physiologic implications

A

♣ osmotic pressure is HIGHER with higher osmolality
♣ osmotic pressure is HIGHER with higher temperature
♣ the higher the osmotic pressure of a solution, the greater the tendency for water to flow into the solution

31
Q
  • measure of the osmotic pressure of two solutions separated by a semipermeable membrane
  • influenced only by solutes that cannot cross the membrane
A

Tonicity

32
Q

OSMOLARITY vs TONICITY

A

OSMOLARITY accounts for all solutes.

TONICITY accounts for only non-permeating solutes

33
Q

♣ Transport of glucose, amino acids, and other polar molecules through the cell membrane
♣ Mediated by carrier proteins in cell membrane

A

Carrier-Mediated Transport

34
Q

Characteristics of Carrier-Mediated Transport

A

♣ Stereospecificity
♣ Saturation
♣ Competition

35
Q

Each carrier protein is specialized to transport a specific substance

A

Stereospecificity

36
Q

Transport rate increases as solute concentration increases until all carriers are saturated (transport maxima, Tmax)

A

Saturation

37
Q

Structurally related solutes compete for transport sites on carrier molecules

A

Competition

38
Q

♣ Occurs uphill against an electrochemical gradient
♣ Requires direct input of metabolic energy (active)
♣ Carrier-mediated transport that exhibits stereospecificity, saturation and competition

A

Primary Active Transport

39
Q

♣ Transport Na+ from ICF to ECF and K+ from ECF to ICF -against electrochemical gradients
♣ Energy provided from terminal bonds of ATP
♣ Usual stoichiometry is 3NA+/2K+

A

Na+/K+-ATPase

40
Q

Functions of Na+/K+-ATPase

A

♣ CONTROL OF CELL VOLUME - large numbers of proteins and other osmotically active particles are present inside the cell
♣ ELECTROGENIC NATURE - net of one positive charge is moved from the interior of the cell to the exterior for each cycle of the pump; creates an electrical potential across the cell membrane

41
Q

♣ Transport of two or more solutes is coupled
♣ One of the solutes (usually Na+) is transported downhill and provides energy for the uphill transport of other solute(s)
♣ Metabolic energy is provided indirectly from the Na+ gradient
♣ inhibition of Na+/K+-ATPase inhibits secondary active transport

A

Secondary Active Transport

42
Q

Types of Secondary Active Transport

A
  1. Co-Transport

2. Countertransport

43
Q
  • also called symport

- occurs if the solutes move in the same direction across the cell membrane

A

Co-Transport

44
Q
  • called exchange transport or antiport

- occurs if the solutes move in opposite directions across the cell membrane

A

Countertransport

45
Q

Transport of hormones along the blood stream to a distant target organ

A

Endocrine Signaling

46
Q

♣ Also called synaptic transmission

♣ Transport of neurotransmitter from a presynaptic cell to a postsynaptic cell

A

Neurocrine Signaling

47
Q

♣ Release and diffusion of local hormones with regulatory action on neighboring target cells

A

Paracrine Signaling

48
Q

♣ A cell secretes hormones or chemical messengers that binds to the same cell

A

Autocrine Signaling

49
Q

♣ Also called contact-dependent signaling
♣ transmitted via oligosaccharide, lipid or protein components of a cell membrane
♣ occurs between adjacent cells linked by gap junctions

A

Juxtacrine Signaling

50
Q

2 Basic Classes of Receptor

A

Plasma Membrane receptors

Nuclear receptors

51
Q

♣ Ion-channel linked
♣ G-protein coupled receptors
♣ Catalytic receptors
♣ Transmembrane receptors

A

Plasma Membrane receptors

52
Q

♣ hormone-receptor complex binds to DNA and regulates the transcription of specific genes
♣ Early primary response –>gene activation to stimulate other genes –> biological effect

A

Nuclear receptors

53
Q

♣ Process by which an extracellular signal activates a membrane receptor
♣ second messengers
♣ Involves small molecules in complicated networks within the cell
♣ Results to single amplification
♣ Alteration of intracellular molecules creating a response

A

Signal Transduction

54
Q

♣ Family of integral transmembrane proteins that possess seven transmembrane domains
♣ Heterotimeric complexes - α, β, and γ subunits
♣ Linked with more than 1000 different receptors

A

G Protein-Coupled Signal Transduction Pathways

55
Q

♣ Mediate direct and rapid synaptic signaling between electrically excitable cells
♣ neurotransmitters bind to the receptors and either open or close the ion channel
♣ Chemical electrical signal response
♣ Examples: Voltage gated-channels in NMJ, ryanodine receptor, Arachidonic acid, caffeine

A

Ion Channel Linked Signal Transduction Pathway

56
Q

♣ Kinase is an enzyme that modifies other proteins by phosphorylation
♣ Phosphorylation usually results in a functional change of the target protein

A

Protein Kinases

57
Q

♣ calcium (Ca2+) binding causes conformational alterations in calmodulin; Eg. Muscle cells

A

Calmodulin-dependent Protein Kinases

58
Q

♣ Adenylyl cyclase facilitates the conversion of ATP to cAMP
♣ Increased cAMP activates protein kinase A

A

cAMP-dependent Protein Kinases

59
Q

♣ Binding of ANP causes dimerization and activation of guanylyl cyclase, which metabolizes GTP to cGMP
♣ cGMP activates cGMP-dependent protein kinases; phosphorylates proteins on specific serine and threonine residues

A

cGMP-dependent Kinases

Phisiology Hope (7 decks)

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