Chapter 4: Sections 4.2, 4.3a, 4.3b: Structure of Plasma Membrane & Passive Transport

Question 1

List lipid components of the plasma membrane

Answer 1

Plasma membrane
Phospholipids
Cholesterol
Glycolipids

Question 2

Function of plasma membrane

Answer 2

Regulates the movements of most substances in and out of the cell.

Question 3

Function of phospholipids

Answer 3

Have polar “heads” and two hydrophobic “tails.” Prevents the plasma membrane from dissolving and allows small, nonpolar substances to penetrate w/o assistance

Question 4

Function of Cholesterol

Answer 4

Strengthens the membrane and stabilizes the membrane against temperature extremes

Question 5

Function of glycolipids

Answer 5

Help to form glcocalyx, the “coating of sugar” on the cell’s surface

Question 6

Function of phospholipid bilayer

Answer 6

Ensures that cytosol and fluid surrounding cells remain separate.

Question 7

Function of membrane proteins

Answer 7

Compose half of the plasma membrane by weight. Determine most of a membranes functions. Classified structurally as integral proteins or peripheral proteins.

Question 8

Structure of integral proteins

Answer 8

Embedded within and extend across lipid bilayer. Make good channel proteins for transportation of substances into an out of the cell

Question 9

Structure of peripheral proteins

Answer 9

Are not embedded in lipid bilayer.

Question 10

Function of transport proteins

Answer 10

Regulate movement of substances across cell membrane. Can be channel proteins, carrier proteins, pumps, symporters, and antiporters.

Question 11

Function of cell surface receptor

Answer 11

Bind ligand molecules, such as neurotransmitters and hormones, released from a specific cell.

Question 12

Function of identity markers

Answer 12

Communicate to other cells that they belong to the body. Immune system cells distinguishing healthy cells from foreign cells.

Question 13

Function of enzymes

Answer 13

Catalyze chemical reactions

Question 14

Function of anchoring sites

Answer 14

Secure cytoskeleton to plasma membrane

Question 15

Function of cell-adhesion proteins

Answer 15

Perform cell to cell attachements

Question 16

Two categories of membrane transport

Answer 16

Passive or active transport

Question 17

Characteristics of passive transport

Answer 17

Do not require energy
Depend on substances moving down with "[ ]" gradient
Includes two types: 
Diffusion (several types)
Osmosis

Question 18

Define diffusion

Answer 18

The movement of a dissolved substance (solute) from an area of greater concentration of that dissolved substance to are of lesser concentration of that dissolved substance.

Question 19

Two conditions that affect the rate of diffusion

Answer 19

Steepness and temperature

Question 20

Two types of diffusion

Answer 20

Simple and facilitated diffusion

Question 21

Define Simple Diffusion

Answer 21

Solutes that are small and nonpolar move down their concentration gradient passing between the phospholipid molecules. Movement is dependent on concentration gradient alone.

Question 22

Define facilitated diffusion

Answer 22

A transport process for small, charged and small, polar solutes. Requires assistance from plasma membrane proteins. Two subtypes:
Channel mediated
Carrier mediated

More transport proteins, faster diffusion

Question 23

Function of channel mediated diffusion

Answer 23

Movement of small ions through water-filled protein channels. Specific to one ion type. Involves either leak channels which are continuously open or gated channels which are usually closed (open to response of stimuli).

No energy required

Question 24

Function of carrier mediated diffusion

Answer 24

Small, polar molecules are assisted across the membrane by carrier proteins. Binding of a substance causes a change in the carrier protein shape. Substances are then released on other side of the cell membrane. Uniporter

Question 25

Define osmosis

Answer 25

Passive movement of water through a selectively permeable membrane from an are of low concentration of nonpenetrating solute particles to an area of high concentration of nonpenetrating solute particles.

Question 26

Two types of solutes

Answer 26

Penetrating ad nonpenetrating

Question 27

Define penetrating solutes

Answer 27

Pass through phospholipid bilayer

Small and nonpolar

Question 28

Define nonpenetrating solutes

Answer 28

Prevented from passing through bilayer

charged, polar, or large

Question 29

Define aquaporins

Answer 29

An integral protein water channel

Question 30

Define osmotic pressure

Answer 30

The pressure exerted by the movement of water across a semi-permeable membrane due to a difference in solution concentration

Question 31

Define tonicity

Answer 31

Ability of a solution to change the volume of the cell by osmosis