2.5.5- Factors Affecting Membrane Structure And Permeability

Question 1

What are the effects of lowered temperature on molecules?

Answer 1

They have lower kinetic energy, causing them to move slower.

Question 2

Most organisms don’t generate heat to maintain body temperature, hence;

Answer 2

Their temperature varies with their environment.

Question 3

When temperature drops, what happens to saturated fatty acids?

Answer 3

They become compressed

Question 4

Explain what happens to unsaturated fatty acids when the temperature drops.

Answer 4

They get compresses, but their kinks in their tails push the molecules away.

Question 5

Molecules being pushed away by unsaturated fatty acids’ kinks when temperature drops helps to maintain what?

Answer 5

Membranes fluidity

Question 6

At cold temperatures, what heavily influenced the fluidity of the membrane?

Answer 6

The ratio of sat:unsat fatty acids in the membrane.

Question 7

Explain how cholesterol molecules can buffer the effect of lowered temperature on membranes.

Answer 7

The cholesterol prevents the phospholipids from packing in too closely together by going in between groups of phospholipid molecules to prevent a reduction in fluidity.

Question 8

Explain how some fish, plants and microorganisms can respond to lower temperatures in relation to membranes.

Answer 8

They can change the composition of the fatty acids in their membrane to buffer the effects of he temperature.

Question 9

When temperature increases, so does membrane _______ and ________.

Answer 9

Permeability

Fluidity

Question 10

Why does the fluidity of the membrane increase with heightened temperature?

Answer 10

The plipids get more kinetic energy, hence move around more

Question 11

A rain see temperature can have what effect on the membrane during phagocytosis?

Answer 11

It can effect the unfolding of the plasma membrane.

Question 12

An increase in membrane fluidity can cause a change in the ability of cells to…

Answer 12

Signal to other cells by releasing chemicals (often done by exocytosis).

Question 13

How does the presence of cholesterol in membranes help, to some extent, buffer the effects of increased temperature on the membrane.

Answer 13

It reduces the increase in membrane fluidity

Question 14

An increase in temperature can effect the way membrane embedded proteins are ________ and ________

Answer 14

Positioned

Function

Question 15

Give an example of how membrane embedded proteins can be effected by an increase in temperature.

Answer 15

If some of the proteins that act as enzymes drift sideways, it can alter the rate f reactions they catalyse

Question 16

Changing temperature alters the movement of plipids but not their _______ _________ __________

Answer 16

Integral molecular structure.

Question 17

Explain how PROTEINS are effected by high temperatures.

Answer 17

It causes the atoms to vibrate, breaking the hydrogen and ionic bonds in the structure- causing the tertiary structure (shape) of the structure to be denatured

Question 18

Just underneath the plasma membranes, there are…

Answer 18

Cytoskeleton threads made of protein.

Question 19

What will happen if the cytoskeleton threads and membrane embedded proteins get denatured?

Answer 19

The plasma membrane will begin to fall apart- becoming more permeable due to the holes in it

Question 20

Membrane embedded enzymes will slow their rate of reaction if what two things happen?

Answer 20

The shape of the active site slightly changes.

The enzymes move slightly within the membrane.

Question 21

What effect does organic solvents have on membranes and why.

Answer 21

Organic solvents (e.g. acetone/ ethanol) will damage cellular membranes as they dissolve lipids.

Question 22

Explain the effects of increasing temperature on molecules.

Answer 22

They get more kinetic energy, causing them too be faster.