Chapt 7

Question 1

Define selective permeability.

Answer 1

The plasma membrane will only allow certain substances to cross more easily than others.

Question 2

What are the two most important components of the membrane?

Answer 2

Lipids and proteins

Question 3

Which lipids are the most abundant?

Answer 3

Phospholipids

Question 4

What does amphipathic mean?

Answer 4

It’s a phospholipid that has both a hydrophilic region and a hydrophobic region.

Question 5

Describe fluid mosaic model of the membrane.

Answer 5

The membrane is a fluid structure with a mosaic of various proteins embedded in or attached to a double layer of phospholipids.

Question 6

The head of the phospholipid is hydrophilic. T or F.

Answer 6

True.

Question 7

The higher the number of phospholipids with unsaturated carbon tails, the longer it will remain fluid in colder temps. T or F.

Answer 7

True.

Question 8

When a membrane solidifies its _____ changes and enzymatic proteins in the membrane become___

Answer 8

permeability . inactive

Question 9

Name two major populations of membrane proteins.

Answer 9

Integral proteins and Peripheral proteins

Question 10

Within the integral proteins, which type of protein spans the membrane?

Answer 10

transmembrane proteins

Question 11

T or F. Peripheral proteins are embedded in the lipid bilayer.

Answer 11

False.

Question 12

List some functions for membrane proteins.

Answer 12

1. Transport 2. Enzymatic activity 3. Signal transduction 4. Cell-cell recognition 4. Intercellular joining 5. Attachment to the cytoskeleton and extracellular matrix.

Question 13

Give an example of cell-cell recognition.

Answer 13

The immune system can reject foreign cells which want to cause disease.

Question 14

The carbohydrates attached to some proteins and lipids of the plasma membrane are added as the membrane is made and refined in the ER and Golgi apparatus. The new membrane then forms transport vesicles that travel to the cell surface. On which side of the vesicle membrane are the carbohydrates?

Answer 14

The inner side of the transport vesicle.

Question 15

How would you expect the saturation levels of membrane phospholipids to differ in plants adapted to cold environments?

Answer 15

Plants adapted to cold environments have more unsaturated fatty acids in their membrane so they can stay fluid longer in colder weather.

Question 16

Nonpolar molecules are hydrophobic or hydrophilic?

Answer 16

Hydrophobic

Question 17

List some nonpolar molecules

Answer 17

hydrocarbons, carbon dioxide, oxygen

Question 18

If a molecule is nonpolar, or hydrophobic, can it dissolve in the lipid bilayer of the membrane?

Answer 18

Yes

Question 19

What are some polar molecules?

Answer 19

glucose and other sugars, water

Question 20

Do polar molecules pass quickly or slowly through the lipid bilayer of a membrane?

Answer 20

slowly

Question 21

Compared to polar molecules, how quickly can a charged atom or molecule move through the membrane?

Answer 21

They move even slower than the polar molecules

Question 22

In order to make it easier for polar molecules to pass through the lipid bilayer, what proteins can make the job easier?

Answer 22

transport proteins

Question 23

Are transport proteins specific for certain molecules?

Answer 23

Yes

Question 24

Two molecules that can cross a lipid bilayer without help from membrane proteins are oxygen and carbon dioxide. What properties allow this to occur?

Answer 24

They are nonpolar and thus can dissolve in the lipid bilayer of the membrane with transport proteins.

Question 25

Why would water need a transport protein to move rapidly through the membrane and in large quantities?

Answer 25

Water in polar and would move too slowly through the lipid bilayer so it needs a transport protein.

Question 26

Molecules have a type of energy called ___

Answer 26

thermal motion (heat)

Question 27

What is one result of thermal motion?

Answer 27

Diffusion

Question 28

Define diffusion.

Answer 28

The movement of molecules os any substance so they they spread out evenly into available space.

Question 29

Define concentration gradient

Answer 29

The movement of a substance from where it is more concentrated to where it is less concentrated.

Question 30

Does this concentration gradient process require energy

Answer 30

No it’s passive

Question 31

The concentration gradient itself represents ___ energy and drives diffusion.

Answer 31

potential energy

Question 32

The diffusion of water across a selectively permeable membrane is called ____

Answer 32

osmosis

Question 33

Define tonicity.

Answer 33

The ability of a solution to cause a cell to gain or lose water.

Question 34

Is there any movement in an isotonic solution?

Answer 34

No, no net movement.