factors affecting membrane structure and permeability Flashcards
what is the plasma membrane made from ?
phospholipid bilayer
proteins (extrinsic + intrinsic)
glycoproteins
glycolipids
cholesterol
what is the purpose of cholesterol ?
maintain fluidity of the phospholipid bilayer
how do these molecules cross the membrane ?
a) O mols
b) NA+ ions
c) glucose
a) simple diffusion
b) facilitated diffusion through a channel proteins
c) facilitated diffusion using a carrier protein
what happens to the molecules as temperature increases and as a result … ?
gives all molecules more kinetic energy
–> as a result these molecules move faster
what happens to the molecules as temperature decreases and as a result …
decreases the temperature lowers the kinetic energy of the molecules
–> causes them to move more slowly
when the temperature drops what happens to saturated fatty acids ?
become compressed
how is the membranes fluidity maintained when temperature drops within the structure ?
- there are many unsaturated fatty acids making up the cell membrane phospholipid bilayer
- as they become compressed
–> kinks in their tails push adjacent phospholipid molecules away
what determines the membrane’s fluidity at cold temperatures ?
the proportions of unsaturated and saturated fatty acids within a cell membrane
what does cholesterol do when the temperature drops ?
- buffers the effect of lowered temperature
–> to prevent a reduction in the membrane’s fluidity
what does cholesterol do within it’s role when the temperature drops ?
- prevents the phospholipid molecules from packing together too closely
–> as cholesterol molecules are in between groups of phospholipid molecules
what can some organisms do ?
change the composition of the fatty acids in their cell membranes in response to lowered temperatures
what happens to the phospholipid bilayer when temperature increaeses and this also…
- acquire more kinetic energy and move around more in a random way
- this increases the membrane fluidity as well as the permeability
what does increasing the temperature do to proteins within the membrane ?
- affects the way membrane-embedded proteins are positioned and may function
what happens to the proteins that act as enzymes within a membrane ?
- it can drift sideways
–> which can alter the rate of reactions they catalyse
what can increasing the temperature membrane fluidity affect ?
- the infolding of the plasma membrane during phagocytosis
- may also change the ability of cells to signal to other cells by releasing chemicals - often by exocytosis
what does cholesterol do within it’s role when the temperature rises ?
- phospholipid drift as interactions between cholesterol and phospholipid tails are broken due to an increase in movement of molecules by kinetic energy
what happens when embedded membrane proteins drift or denature ?
leakage occurs
what does changing temperature do to lipids ?
alter their movement however they don’t alter their integral molecular structure
what happens to proteins during high temperatures ?
- causes the atoms within their large molecules to vibrate
–> causes the HB and IB to break which holds their structure together
they unfold
what happens to the tertiary structure and as a result ?
the tertiary structure changes shape and cannot change back again when they are cool
– DENATURED
what is under the plasma membrane ?
cytoskeleton which is made of protein
what happens to membrane-embedded enzymes ?
will cease to function if they become denatured
- if shape of active site changes slightly or the enzymes move within the membrane
–> the rate of reactions that they catalyse will be slowed
what is the effect of solvents and detergents of plasma membrane ?
the phospholipid membrane can be dissolved by organic solvents such as ethanol as well as detergents
what is used during DNA extraction ?
both ethanol and detergents
why are beetroot cores washed after cutting them ?
to get rid off any excess
why was a cork borer used to prepare the beetroot samples ?
ensures uniform sample preparation
–> crucial for reducing variability
why should one aim to use the same betroot to take samples from ?
ensures the consistency of the experimental conditions
what does beetroot cells contain ?
purple pigment –> anthocyanin within a vacuole in the plant cells
what is vacuole surrounded by ?
a membrane called tonoplast
what is the purpose of colorimeters ?
providing a quantitative way to assess changes in membrane permeability under various experimental conditions
–> helps to understand how factors such as temp or pH affect integrity of PM
what is units for absorption of light ?
AU
what does absorption of light show ?
how much light is absorbed by the solution
what complimentary colour would we use for a purple solution ?
a green filter
how does one set up a colorimeter ?
1) turn on colorimeter
2) choose absorbance or transmission
3) choose filter
4) calibrate colorimeter using a ‘blank’ a cuvette containing distilled water
5) take readings of sample
what happens once heating pieces of a beetroot tissue ?
the PM and tonoplast membrane will be distributed and the pigment will leak out
