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BIO 110 LAB > Cell Membrane Permeability (lab 3) > Flashcards

Cell Membrane Permeability (lab 3) Flashcards

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Biology 101 flashcards
1
Q

Fundamentally what is a cell membrane composed of?

A
  • 2 lipid layers
  • AKA phospholipids (the lipids contain phosphorous)
  • Associated w/ the bilayer are proteins
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2
Q

What is the job of the Lipid Bilayer?

A
  • Forms boundary between contents of a cell & its external environment
  • Controls what molecules pass through
  • Must remain intact so that cell lives
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3
Q

What is Permeable?

A

-Molecule can pass through the membrane

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4
Q

What is Impermeable?

A

-Molecule cannot pass through membrane

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5
Q

Why does this lab use Red Blood cells?

A

-Plasma membrane of a RBC is simple bc its mostly phospholipids w/ very few proteins

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6
Q

What is the goal for this lab?

A

-Investigate 3 factors that influence cell membrane permeability

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7
Q

What is the role of diffusion?

A
  • One factor that governs the fate of the solute (X)
  • Moves from high concentration to low concentration
  • So the tendency is to enter the cells
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8
Q

What must we understand first?

A
  • Diffusion
  • Membrane permeability
  • Water potential
  • Fragility of animal membranes
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9
Q

What is the role of Membrane Permeability?

A
  • If membrane is permeable to solute then the substance will enter cell & increase the solute concentration inside the cell
  • If high permeability= fast
  • If low permeability= slow
  • Impermeable= solute won’t enter at all
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10
Q

What role does Water Potential play?

A
  • As solute concentration increases within cell, it’s water potential goes down
  • RBC are highly permeable to water
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11
Q

What role does the Fragility of Animal Membranes play?

A
  • As water enter RBC they swell causing the cells to lyse (burst)
  • It is during this time where the mixture containing them turns clear
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12
Q

What does the time to Lysis represent?

A
  • Indirect measurement of membrane permeability

- The shorter the time, the higher the permeability

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13
Q

What did we use to measure the time for Lysis?

A
  • Spectrometer (Spec 20)

- Operates on the wavelength of 400-700 nm

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14
Q

How does the Spec 20 work?

A
  • White light from lamp enters monochromator & split into component wavelengths (colors!) by prism
  • Mech in the Spec 20 selects desired wavelength & passes it through the tube containing the mixture
  • Light that is NOT absorbed by tube falls on detector & gets converted to electrical signal
  • Electrial signal is then amplified & its magnitude is displayed by needle on readout scale
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15
Q

What does the Spec 20 read at first before the cells start to lyse? What about after they lyse?

A
  • It will read it as low transmittance because the mixture is turbid
  • After the cells lyse the transmittance value will be higher bc the mixture is now clear
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16
Q

What does the value H50 represent?

A
  • Hemolysis 50
  • Time required to reach half the max value indicated by the plot on the computer
  • So its our measure of the time to lysis
  • The smaller the H50, the greater the permeability is & vise versa
17
Q

What is the Purpose of the lab?

A

-How the size of the solute molecule, the net charge of the solute particle & the lipid solubility affect cell membrane permeability

18
Q

What are the Independent Variables?

A
  • Size of molecule
  • The net charge of the solute particle
  • Lipid solubility of the solute molecule
19
Q

What is the Dependent Variable?

A

-Cell membrane permeability

20
Q

What is important to note about the weight of a molecule?

A
  • Size of a molecule is generally proportional to its weight

- The higher the molecular weight, the harder it is for it to pass through the cell membrane

21
Q

What 6 liquids did use to illustrate the size on permeability?

A
  • Water
  • Urea
  • Glycerol
  • Glucose
  • Sucrose
22
Q

What is important to note about the charge of a molecule?

A
  • Uncharged molecules pass through cell membranes more easily than charges ones
  • Small uncharged water soluble molecules diffuse between lipid molecules of cell membrane in an uncontrolled fashion
  • Larger water soluble molecules & small charged molecules must have specific channel to diffuse
23
Q

Which molecules would easily pass through cell membrane?

A
  • Lipophillic or non polar
  • Since they easily dissolve in the lipids of the cell membrane, the cell membrane cannot control which lipid soluable molecules enter
24
Q

How can we determine lipid solubility by looking at the chemical structure of a molecule?

A

-The more CH3, CH2, or CH groups a molecule has the more lipid soluble it will be

25
Q

How can we determine water soluablity by looking at the chemical structure of a molecule?

A

-The more OH- (Hydroxyl) groups it has, the more water soluble/ polar it will be

26
Q

What ratio was used to keep track of soluability?

A
  • CHn/ OH

- Meaning that the higher the ratio, the more lipid soluble a molecule will be

27
Q

What did we use to determine lipid solubility?

A
  • Methanol
  • Propanol
  • Butanol
  • Pentanol
28
Q

What else did we use to illustrate the effect of lipid solubility?

A
  • Propanol
  • 1,2 Propanediol
  • 1,2,3 Peopanetriol (glycerol)
  • Since these have more OH- groups they’ll become more water soluable as they increase in weight
29
Q

How do you callibrate the Spec 20?

A
  • Turn on the knob on it’s left end of the top scale so that it reads 0% transmittance. If you don’t then the Spec 20 won’t be able to the test tube due a shutter speed
  • Turn the knob at the right end of the top scale with a blank test tube in place so that it actually reads 100% transmittance
  • Make sure the wavelenght is at 620 nm
30
Q

How do you make a blank test tube?

A
  • Place 3 drops of animal blood in a clean & dry test tube
  • Then inject 5ml of distilled water
  • wait 1 minute
  • Then place it in the Spec 20 after you calibrate the left knob at 0%
31
Q

How do you calculate H50 on the computer graph?

A
  • Move the horizontal line of the blue cursor at the max value that the plot appears to be approaching
  • Move red cursor to lowest value of the plot
  • Calculate; Blue cursor TV- Red Cursor Divided by 2 & then add Red cursor TV

BIO 110 LAB (14 decks)

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