2.5- Factors affecting memrbrane strucutre and permebality

Question 1

What happens when you increase the temp?

Answer 1

Increasing the temp gives all molecules more kinetic energy and as a result these molecule’s move faster

Question 2

What happens when you decrease the temp?

Answer 2

Decreasing the temp lowers the kinetic energy of the molecules causing them to move more slowly

Question 3

What happens top the phospholipid when temp drops?

Answer 3

• Saturated fatty acids become compressed.
• However, there are many unsaturated fatty acids making up the cell membrane phospholipid bilayer, and as they become compressed, the kinks in their tails push adjacent phospholipid molecules away. This maintains the membrane fluidity.
• Therefore, the proportions of unsaturated and saturated fatty acids within a cell membrane determine the membrane’s fluidity at cold temperatures.

Question 4

What happens to the cholesterol in the phospholipids when the temp drops?

Answer 4

-Cholesterol in the membrane also buffers the effect of lowered temperature, to prevent a reduction in the membrane’s fluidity. It does this by preventing the phospholipid molecules from packing together too closely, because the cholesterol molecules are in between groups of phospholipid molecules.

Question 5

What can some organism such as fish and microorganism do?

Answer 5

They can change the composition of the fatty acids in their cell membranes in response to low temp. Some plants can do this.

Question 6

What happens top the phospholipid when temp increases?

Answer 6

• The phospholipids acquire more kinetic energy and move around more, in a random way. This increases the membrane’s fluidity.
• Permeability increases.
• It also affects the way membrane-embedded proteins are positioned and function. If some of the proteins that act as enzymes in a membrane drift sideways, this could alter the rate of the reactions that they catalyse.
• An increase in membrane fluidity may affect the infolding of the plasma membrane during phagocytosis.
• An increase in membrane fluidity may also change the ability of cells to signal to other cells by releasing chemicals, often by exocytosis.

Question 7

What happens to cholesterol when temp increase?

Answer 7

The presence of cholesterol molecules buffer to some extent, the effects of increasing hear as it reduces the increase in membrane fluidity.

Question 8

What affect does changing temp have on phospholipids?

Answer 8

Whereas changing temperature can alter the movement of phospholipids, it does not drastically alter their integral molecular structure

Question 9

What affect does changing temp have on protein?

Answer 9

Proteins not as stable as phospholipids.

Question 10

What does high temp do to protein?

Answer 10

• High temperatures cause the atoms within their large molecules to vibrate, and this breaks the hydrogen bonds and ionic bonds that hold their structure together; they unfold.
• Their tertiary structure changes and cannot change back again when they cool; they are denatured.

Question 11

What will happen to the cytoskeleton when temp increases?

Answer 11

Underneath the plasma membrane are cytoskeleton threads made of protein. If both membrane embedded proteins and the cytoskeleton thread become denatures, then the plasma membrane will begin to fall apart, it will become more permeable as holes will appear in it.

Question 12

What will happen to the membrane embedded enzymes when temp increases?

Answer 12

Membrane embedded enzymes will cease to function if they become denature. If the shape of their active site changes slightly or the enzymes move within the membrane the rate of the reaction that they catalyse will be slowed.

Question 13

What are the effects of solvents on phospholipids?

Answer 13

Organic solvents such as ethanol will damage cell membranes, as they dissolve lipids.`

Question 14

EXPERIMENT

Answer 14

LOOK IN LAB BOOK

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