factors affecting membrane's structure and permeability Flashcards

1
Q

what are the three factors that effect membrane’s permeability

A

-temperature
-ph
-solvent concentration

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2
Q

explain what happens to the permeability of a membrane as temperature increases?

A

-at higher temperature the phospholipids have more kinetic energy so move around more within the bilayer
-this results in a increased number of gaps present between the phospholipids which in turn increases the fluidity of the bilayer
-the structure of the membrane is now disrupted
-eventually the membrane proteins denature which increases the permeability of membranes to water -soluble/polar substances

-the structure of the membrane is even further disrupted and it can no longer be restored,the effects are now irreversible

-as the membrane no longer acts as an effective barrier to polar substances,allowing them to pass though the membrane

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3
Q

what happens to the permeability of a membrane with lower temperature

A

at lower temperature the phospholipids have less kinetic energy so move around the bilayer less,this decreases the number of gaps present between phospholipids and thus also decreases the fluidity ,but increases the rigidity of the membrane.

Meas that the permeability of the membrane also decreases and the membrane acts as a effective barrier to polar substances so that they cannot pass through the membrane

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4
Q

is the changes in the membrane reversible after the membrane proteins denature

A

no they are not,the membrane structure is permanently disrupted

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5
Q

before the membrane proteins denature are the changes to the structure of the membrane reversible?

A

yes they are reversible,as the temperature lowers the fluidity of the membrane will decrease and the membrane will restore its structure thus decreasing its permeability to polar substances

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6
Q

between 0 ad 40 the membrane is described as partially permeable.True or false

A

true

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7
Q

how does a low ph effect the membrane’s permeability

A

a low/high ph will change the tertiary structure of the membrane proteins causing them to denature,and thus increasing the permeability of the membrane to polar substances

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8
Q

what is the general pattern between temperature and permeability of a membrane

A

when temperature increases so does the permeability of a membrane

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8
Q

general pattern for solvent concentration and permeability of a membrane

A

increasing the solvent concentration increases the permeability of the membrane

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9
Q

what happens to membrane protein below 0 degrees and how does that effect the permeability of a membrane

A

they deform ,disrupting the structure of the membrane and increasing its permeability

-below 0 degrees ice crystals can pierce the membrane making it highly permeable

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10
Q

describe what happens to the permeability of a cell membrane with the increase of solvent concentration

A

-increasing the solvent concentration also increases the permeability of a cells membranes.

-the non-polar solvent molecules enter and stick between phospholipids, disrupting the structure of the membrane.

-This causes the membrane to become more fluid and thus permeable

-increasing the solvent concentration further will result in the non-polar solvent dissolving the phosholipids causing the membrane to lose its structure and disintigrate, killing the cell

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11
Q

what happens when the neural membrane are disrupted

A

nerve impulses are no longer transmitted normally

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12
Q

describe the permeability of membrane between 0-40 degrees
then after 40 degrees

and then below 0 degrees

A

0-40-partually permeable as temp increases so does the permeability of the membrane ,but permeability increases steadily

-after 40-protein denature,membrane becomes highly permeable,rapidly

-below 0 -the proteins deform ,membrane structure is disrupted so permeability increases also ice crystals may pierce the membrane

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12
Q

what does the experiment on factors effecting the structure and permeability of membranes involve

A

-involves beetroot, beetroot contain a purple pigment within them

-the higher the permeability of the beetroot membrane ,the more of the pigment leaks out of the cell
-thus the higher the permeability of the beetroot’s membrane the more purple the solution will be and so will have a lower light absorbance value

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13
Q

describe a method you will use to investigate the effects of temperature on the permeability of a beetroot membrane

A

-cut 5 equal sized beetroot using a scalpel,
why is that important?

ensures they are the same length and have the same dimensions so that they dont have a different SA and Volume which are factors that can affect the rate at which pigment leaks out so final results can be altered

  • rinse the beetroot to remove any pigment released during the cutting
  • add the beetroot pieces to 5 separate test tubes, each must contain the same volume of water

-put each test tube in a water bath set at a different temperature ,for example 10,20,20,20,50

-allow them to sit for a specific period of time-long enough to allow the pigment to diffuse out the beetroot and into the water-e,g 30 min

-Remove the beetroot from each test tube so you are left with the coloured solution

-calibrate the colourimeter and pour the leftover mixtures into 5 separate cuvettes

-insert the cuvette, ensure to recalibrate between readings

-then use the colourimeter with a blue filter to measure the light absorbance of each coloured solution

-the higher the light absorbance,the more pigment there is present in the solution so the more permeable the beetroot’s membrane is

-as temp increases the membrane permeability also increases so the light absorbance value also increases with temperature

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14
Q

how can we find the light absorbance of unknown pigment concentration solution

A

have solutions of known concentration, measure their values and plot a calibration curve

-do the same for the unknown solution and draw intercept to find the light absorbance of it

14
Q

how can we investigate how solvent concentration affects the permeability of a membrane

A

-do the same experiment like for temperature,but instead placing the beetroot pieces in water baths at different temperature

-we will place them in 5 test tubes,each with an increasing concentration of solvent for a set amount of time

-the rest of the experiment is the same

15
Q

what are some limitations of the experiment and how do you solve them

A

-beetroot pieces may not be the same size so some test tubes may contain more beetroot tissue than others

solution: cut them as accurately as possible using a scalpel and a ruler, and repeat each investigation at least 3 times and find a mean

  • some parts of the beetroot tissue have more pigment in their cells than others

Solution: conduct repeats using different parts of the beetroot and find a mean

16
Q

why do the beetroot pieces get washed in running water

A

to remove all surface pigment released from damaged cells

17
Q

suggest why samples of water containing the beetroot were taken five minutes after each temperature was reached

A

b to allow the mixture to equilibrate

18
Q

suggest why the experiment was repeated 3 times

A

allows for reliability

19
Q

suggest why the absorbance of the samples was measured using a colorimeter with a blue filter

A

because the pigment released is red/purple

20
Q

suggest how and explain why the absorbance would change as the amount of pigment increases

A

higher concentration means there are more pigment molecules. They can absorb more light so light transmitted decreases

21
Q

explain why solvents like water do not disrupt cell membranes

A

water is a polar solvent (1); phospholipids will not dissolve in water (1)

22
Q

describe how the absorbance of light could be measured as the pigment released increases with temperature

A

use of colorimeter (1); detail (e.g., use of filter) (1); range of readings taken (at different
temperatures) (1); draw a graph (1)

23
Q

Suggest how an excessive consumption of alcohol lead to liver cell death and ultimately be fatal

A
  • Alcohol is lipid soluble
    -it dissolves in the membrane bilayer
    -this disrupts the bilayer

-and reduces transport of material

-prevents normal functioning and may lead to cell death
- The liver is particularly affected due to its role in filtering substances from the blood

24
Q

what happens to channel and carrier proteins in cell membranes below 0 degrees

A

they deform increasing the permeability of the membrane

25
Q

explain why a specific hormone only has an effect on specific cells,not the entire body

A

-hormones bind to receptors that have a complementary shape to theirs.
-Only target cells have the right receptors whereas other body cells do not

25
Q

example of a messenger molecule in the body

A

-any hormones ,they bind to complementary receptors causing a reaction