Chapter 7

Question 1

The boundary that separates the living cell from its surroundings

Answer 1

Plasma Membrane

Question 2

The plasma membrane exhibits __________, allowing some substances to cross it more easily than others

Answer 2

Selective Permeability

Question 3

Are fluid mosaics of lipids and proteins

Answer 3

Cellular Membranes

Question 4

The most important lipid in the plasma membrane

Answer 4

Phospholipids

Question 5

Phospholipids are ________ molecules, containing ________ and ________ regions

Answer 5

Amphipathic; Hydrophobic; Hydrophilic

Question 6

States that a membrane is a fluid structure with a “mosaic” of various proteins embedded in it

Answer 6

Fluid Mosaic Model

Question 7

______ have been chemically analyzed and found to be made of _____ and ______

Answer 7

Membranes; Proteins; Lipids

Question 8

Scientists studying the plasma membrane reasoned that it must be a ________

Answer 8

Phospholipid bilayer

Question 9

In 1935, _______ and _______ proposed a sandwich model in which the phospholipid bilayer lies between two layers of globular proteins

Answer 9

Hugh Davson; James Danielli

Question 10

In 1972, _______ proposed that the membrane is a mosaic of proteins dispersed within the bilayer, with only the hydrophilic regions exposed to water

Answer 10

S.J. Singer and G. Nicolson

Question 11

_______ in the plasma membrane can move within the bilayer

Answer 11

Phospholipids

Question 12

As temperatures cool, membranes switch from a _____ state to a ______ state

Answer 12

Fluid; Solid

Question 13

Membranes rich in unsaturated fatty acids are more ______ than those rich in saturated fatty acids

Answer 13

Fluid

Question 14

Membranes must be _____ to work properly; they are usually about as fluid as salad oil

Answer 14

Fluid

Question 15

The steroid, _______ has different effects on membrane fluidity at different temperatures

Answer 15

Steroid

Question 16

At _______ temperatures, cholesterol restrains movement of phospholipids

Answer 16

Warm

Question 17

At ________ temperatures, it maintains fluidity by preventing tight packaging

Answer 17

Cool

Question 18

Determine most of the membrane’s specific functions

Answer 18

Proteins

Question 19

Are bound to the surface of the membrane

Answer 19

Peripheral proteins

Question 20

Penetrate the hydrophobic core

Answer 20

Integral proteins

Question 21

Integral proteins that span the membrane are called

Answer 21

Transmembrane proteins

Question 22

6 major functions of membrane proteins

Answer 22

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

Question 23

Membrane carbohydrates may be covalently bonded to lipids forming

Answer 23

Glycolipids

Question 24

Membrane carbohydrates may be covalently bonded to proteins forming

Answer 24

Glycoproteins

Question 25

Plasma membranes are ___________, regulating the cell’s molecular traffic

Answer 25

Selectively permeable

Question 26

A cell must exchange materials with its surroundings, a process controlled by the ________

Answer 26

Plasma membrane

Question 27

Can dissolve in the lipid bilayer and pass through the membrane rapidly

Answer 27

Hydrophobic (nonpolar) molecules

Question 28

Do not cross the membrane easily, such as sugars

Answer 28

Polar molecules

Question 29

Allow passage of hydrophilic substances across the membrane

Answer 29

Transport proteins

Question 30

Some transport proteins, called ________, have a hydrophilic channel that certain molecules or ions can use as a tunnel

Answer 30

Channel proteins

Question 31

Channel proteins called ________ facilitate the passage of water

Answer 31

Aquaporins

Question 32

Other transport proteins, called _________, bind to molecules and change shape to shuttle them across the membrane

Answer 32

Carrier proteins

Question 33

Is specific for the substance it moves

Answer 33

Transport protein

Question 34

Diffusion of a substance across a membrane with no energy investment

Answer 34

Passive transport

Question 35

Is the tendency for molecules to spread out evenly into the available space

Answer 35

Diffusion

Question 36

At _________, as many molecules cross the membrane in one direction as in the other

Answer 36

Dynamic equilibrium

Question 37

Substances diffuse down their ________, the region along which the density of a chemical substance increases or decreases

Answer 37

Concentration Gradient