Characteristics of the Membrane

Question 1

Major functions of memebrane

Answer 1

1. Separates outside environment fro inside of the cell
2. allows certain things to cross into the cell
3. compartmentalizes cells

Question 2

Selective Permeability

Answer 2

makes sure that what goes into the cell is good

Question 3

Compartmentalization

Answer 3

keeps the cell organized

Question 4

Homeostasis

Answer 4

the way things are supposed to be, this is maintained by the membrane even if crazy stuff is happening outside the cell

Question 5

What is the biological membrane made up of?

Answer 5

phospholipid bilayer that has a hydrophobic head and hydrophilic tail…..the head and the membrane proteins interact to form a insoluble barrier

Question 6

What is carbohydrates role in the membrane?

Answer 6

cell recognition

Question 7

Integral membrane proteins

Answer 7

span or penetrate the cell, causing them to have transmembrane, cytoplasm and extracellular domains. Allow things to enter cell and determine functional properties of cell.

Question 8

Peripheral membrane proteins

Answer 8

proteins located outside of cell. Allow things to enter the cell and determine functional properties of cell.

Question 9

Glycoproteins

Answer 9

allow cells to recognize each other- transfers communication between the cell

Question 10

Glycolipids

Answer 10

determine person’s blood type

Question 11

Why is the phospholipid bilayer responsible for preventing the free passage of most materials across the membrane?

Answer 11

the bilayer has a hydrophobic head which DOES NOT allow hydrogen ions to cross of big molecules to cross unless proteins are involved.
-It has a hydrophobic tail which keeps ions and other molecules from entering the membrane

Question 12

Explain why membranes are described as fluid structures..

Answer 12

"Fluid Mosaics"
fluid
assume shape
easily moved
changing position

Question 13

Fluid Mosaic Model

Answer 13

“Proteins and substances such as cholesterol become embedded in the bilayer, giving the membrane the look of a mosaic. Because the plasma membrane has the consistency of vegetable oil at body temperature, the proteins and other substances are able to move across it. That’s why the plasma membrane is described using the fluid-mosaic model.”

Question 14

How do saturated vs unsaturated fatty acids differ structurally?

Answer 14

SATURATED: STRAIGHT. all carbons have single covalent bonds w/ other carbons and hydrogens.
UNSATURATED: KINKED. contain 1 or more double C-C bonds

Question 15

How does that (unsat. vs sat.) affect fluidity?

Answer 15

Fatty acid tails are very hydrophobic and interact tightly w/ each other to avoid water = saturated= membrane rigid and viscous

Double bonds in unsaturated fatty acid tails put kinks (can’t pack tightly) = unsaturated = membranes more fluid

Question 16

How does the ratios of different types of lipids effect the fluidity of the membrane?

Answer 16

• Some types of phospholipids make the membrane more fluid than others
• Cells can alter the rations quickly
• Different organelles have diff. ratios of lipids

Question 17

How does cholesterol have the ability to both increase and decrease membrane fluidity?

Answer 17

It inserts itself in between the fatty acid tails of the bilayer.

• At high concentrations, cholesterol blocks phospholipids from moving laterally (decreases fluidity)
• At low concentrations, prevents phospholipid tails from packing in tightly (increases fluidity)

Question 18

T/F: A increase in temp. would cause an increase in membrane fluidity

Answer 18

true

Question 19

T/F: An increase in saturation of the fatty acid chain would decrease the membrane fluidity

Answer 19

true

Question 20

T/F: An increase in the number of double bonds present in the phosolipid side chains would cause an increase in membrane fluidity

Answer 20

true

Question 21

T/F: An increase in the average length of the phospholipid fatty acid side chain would cause an increase in fluidity.

Answer 21

true