Chapter 3

Question 1

Describe the Plasma (cell) membrane

Answer 1

It surrounds the cell.

Made of proteins and lipids.

Composition and function can vary from one region of the cell to another.

Question 2

What is the Unit Membrane?

Answer 2

Forms the border of the cell and many of its organelles.

Appears as a pair of dark parallel lines around the cell (when viewed with an electron microscope)

Question 3

What is the function of the plasma membrane?

Answer 3

• Unit membrane at the cell surface.
• Defines cell boundaries
• Governs interactions with other cells.
• Controls passage of materials in and out of cell

Question 4

Describe the intracellular face and the Extracellular face in relation to Plasma Membrane.

Answer 4

Intracellular face - side that faces cytoplasm

Extracellular face - side that faces outward

Question 5

Describe Membrane Lipids

Answer 5

98% of molecules in plasma membrane are lipids

Question 6

How do Phospholipids play a role in the Plasma Membrane?

Answer 6

75% of membrane lipids are phospholipids.

Amphiphilic molecules arranged in bilayer

Hydrophilic phosphate heads face water on each side of membrane

Hydrophobic tails - directed toward the center, avoiding water drift laterally from place to place.

Movement keeps membrane fluid

Question 7

How does Cholesterol play a role in the Plasma Membrane?

Answer 7

20% of the membrane lipids

holds phospholipids still and can stiffen membrane

Question 8

How do Glycolipids play a role in the Plasma Membrane?

Answer 8

5% of the membrane lipids

Phospholipids with short carbohydrate chains on extracellular face

Contributes to Glycoalyx - carbohydrate coating on the cells surface