5.2 Factors Affecting Membrane Structure

Question 1

What do membranes control? What happens if this control is lost?

Answer 1

1. Passage of different substances into + out of cells and organelles.
2. If a membrane loses its structure, cell processes will be disrupted.

Question 2

What are phospholipids in plasma membranes constantly doing?

Answer 2

Moving

Question 3

What happens to phospholipids when temperature is increased?

Answer 3

They gain kinetic energy and move more.
This increases membrane’s fluidity and begins to lose its structure.
If temperature continues to increase, the cell will eventually break down.
This loss of structure increases membrane permeability, making it easier for particles to move through it.

Question 4

What is the effect of carrier and channel proteins being exposed to high temperatures?

Answer 4

They denature.
Carrier + channel proteins aid transport across the membrane so as they denature, membrane permeability will be affected.

Question 5

What polar solvent is essential in the formation of the phospholipid bilayer?

Answer 5

Water

Question 6

What is the relationship between water and the phospolipid bilayer?

Answer 6

Non-polar tails of phospholipids are oriented away from water, forming a bilayer with a hydrophobic core.
The charged phosphate heads interact with water, helping the bilayer stay intact.

Question 7

What are the characteristics of polar solvents in terms of polarity?

Answer 7

Organic solvents are less polar than water (ex. alcohol) or non-polar like benzene

Question 8

How do organic solvents affect membranes?

Answer 8

Organic solvents dissolve membranes, disrupting cells.

Question 9

Why are alcohols used as anti-septic wipes?

Answer 9

The alcohols dissolve the bacteria’s membranes, killing them and reducing risk of infection in the wound

Question 10

What do pure/very strong alcohols do?

Answer 10

Pure alcohols are toxic - they destroy cells in the body.

Question 11

Why are less concentrated alcohols safer? What happens with the non-polar alcohol molecules?

Answer 11

1. They don’t dissolve membranes, but still cause damage.
2. The non-polar alcohol molecules enter the plasma membrane and their presence between the phospholipids disrupts the membrane.

Question 12

What happens to a membrane’s structure when the membrane is disrupted?

Answer 12

The membrane becomes more fluid and permeable.

Question 13

Why could the disruption of membranes be a problem?

Answer 13

Some cells need intact membranes for specific functions.

For example: When neuronal membranes are disrupted, nerve impulses are no longer transmitted as normal.