plasma membrane

Question 1

The function of plasma membrane

Answer 1

Controls what enters and exits the cell to maintain an internal balance called homeostasis.

Question 2

What does the cell membrane do?

Answer 2

The cell membrane senses the external environment. ( extracellular fluid)

It communicates with surrounding cells for responses.

It transmits signals inside the cell to trigger actions. (intracellular fluid)

Question 2

Structure of plasma membrane

Answer 2

1)Phospholipid Bilayer
- 2 layers of phospholipid molecules

2)Phospholipids contain :

• The phosphate head is polar (water-loving - hydrophilic)
• Two Fatty acid tails non-polar
  (water-fearing - hydrophobic)

3)Proteins are embedded throughout the membrane also

Question 2

1. The role of proteins in the plasma membrane

Answer 2

Provide SUPPORT (structural proteins).

Allow cells to RECOGNIZE (receptor proteins) other structures.

Allow cells to COMMUNICATE (secretory & receptor proteins).

Assist with the TRANSPORT (channel & carrier proteins) of substances across the membrane.

Question 2

Why is the structure a bilayer

Answer 2

Phospholipids have hydrophilic (water-loving) and hydrophobic (water-fearing) regions.

This makes them ideal for forming a boundary.

They separate extracellular (outside the cell) and intracellular (inside the cell) fluids.

Question 3

2nd role of proteins in the plasma membrane

Answer 3

Peripheral - Temporarily attached to the membrane

Integral - Permanently embedded in the membrane

Transmembrane- Integral proteins that cross/span the entire membrane

Question 4

What is The Fluid Mosaic Model of the cell membrane

Answer 4

1. It is fluid because phospholipids continually move from side to side
   ( laterally – side to side) in the membrane.
2. Mosaic refers to the proteins and carbohydrates embedded in
   the membrane - like mosaic that is made up of many parts.

Question 5

What makes the tails straight or bent

Answer 5

• Fatty acids can be saturated (with single bonds between C atoms). These form straight tails
• Fatty acids can be unsaturated with at least one double or triple bond between the carbon atoms. These show a kink that adds spaces between the phospholipids.

Question 6

How is membrane fluidity increased

Answer 6

when more unsaturated fatty acids are used in the cell membrane.

• Phospholipids can’t pack tightly, keeping the membrane fluid.
• Prevents the membrane from solidifying, ensuring function.
• Organisms in low temperatures regulate fluidity this way.

Question 7

What role does cholesterol play?

Answer 7

It provides the membrane with its flexible properties.

The more cholesterol in the cell membrane, the greater the fluidity of the membrane.

Cholesterol is HYDROPHOBIC and is spread between the hydrophobic fatty acid tails