ch 6 - phospholipids and membranes

Question 1

What is the fluid mosaic model?

Question 2

What are membrane proteins like? How are they positioned in the membrane?

Answer 2

• Amphipathic
• Integral or transmembrane
  proteins with a
  a stretch of nonpolar amino acids in the
  the middle can integrate into the lipid bilayer

Question 3

What are the functions of membrane proteins?

Answer 3

1. Transport - help move substances
2. Enzymatic activity - Catalyze reactions
3. Signal transduction - Receive chemical
   messages
4. Intercellular joining - Glue cells together
5. Cell-cell recognition - ID tag, specific for each cell type
6. Attachment to the cytoskeleton and extracellular matrix (ECM) - linking proteins
   to the cytoskeleton

Question 4

What is diffusion?

Answer 4

A result of a random
a process that increases entropy

Question 5

What type of molecules can diffuse across membranes? Which ones cannot? Why?

Answer 5

Small, non-polar or uncharged molecules can diffuse across membranes; Large, polar, charged molecules cannot diffuse across water because they require an input of energy to be transported into the cell

Question 6

Why is diffusion spontaneous?

Answer 6

Because water moves toward the solution with the higher solute and
lower water concentration

Question 7

What is osmosis?

Answer 7

The passive transport of water (high concentration to low concentration)

Question 8

What is tonicity?

Answer 8

Determines which way the water moves
- Hypertonic: high
concentration of
solutes
- Hypotonic: lower
concentration of
solutes

Question 9

In which direction across the membrane does water move when cells are placed in an aqueous solution with different tonicity?

Answer 9

From the side of higher water concentration to the side of lower concentration