Chapter 2

Question 1

Selectively Permeable

Answer 1

feature/function of the plasma membrane that maintains homeostasis by regulating the passage of some substances while preventing others from entering the cell.

Question 2

Hydrophilic

Answer 2

water insoluble; “water-loving”

Question 3

Hydrophobic

Answer 3

water soluble; “water-fearing”

Question 4

Lipid bilayer

Answer 4

• composed of two layers of polar phospholipids **A phospholipid contains a polar hydrophillic head and two hydrophobic tails (tails on the inside of the layer and heads on the outside)
• membrane also contains proteins and cholesterol

Question 5

Amphipathic

Answer 5

containing both a polar and non-polar portion

**phospholipids are amphipathic

Question 6

Fluid-mosaic

Answer 6

Used to describe the feature of the plama membrane.

• Fluid: the phospholipid are constantly moving and rearranging.
• Mosaic: several different components of the membrane (different types of lipids, proteins, and carbohydrates).

Question 7

Brownian movement (Diffusion)

Answer 7

random moving of particles; dependent upon temperature and mass of the molecule.
-Does not require ATP

Question 8

Flux

Answer 8

quantity of molecules moving from one sector to another in a defined volume.
-dynamic equilibrium=flux is 0.

Question 9

Permeability coefficient

Answer 9

“Diffusion” coeffecient (P); volume that will flow in an amount of time.
-takes into account: solubility, pore size of the membrane,membrane thickness

Question 10

Osmotic pressure

Answer 10

the pressure that needs to be applied to a solution to prevent the inward flow of water across a semipermeable membrane

Question 11

Isotonic

Answer 11

equal osmotic pressure

Question 12

Hypertonic

Answer 12

having higher osmotic pressure than other solution

Question 13

Hypotonic

Answer 13

has lower osmotic pressure than other solution

Question 14

Crenate

Answer 14

Process in osmosis where red blood cells shrink; This happens if placed in a hypertonic solution

Question 15

Hemolyze

Answer 15

Process in osmosis where red blood cells swell and burst ; this can happen if placed in a hypotonic solution

Question 16

Electrogenic pump

Answer 16

pumps unequal numbers of like charges in opposite directions; some active pumps pump 3 Na+ out of the cell while only 2 K+ are moving into the cell.

Question 17

Electroneutral pump

Answer 17

pumps equal numbers of like charges in opposite directions

Question 18

Endocytosis

Answer 18

Cells absorb molecules by engulfing them;

• pinocytosis= “cell drinking”, fluid endocytosis
• receptor-mediated endocytosis= endocytosis mediated by recoptors on the surace of the membrane; ligand binds to a receptor protein; clathrin coated pit; membrane invaginates to form vesicle
• phagocytosis

Question 19

Exocytosis

Answer 19

mechanism where cell can release certain particles from the cell that are too large to pass the membrane.

Question 20

Tmax

Answer 20

Transport maximum; maximum amount of transported molecule. point at which increases in concentration do not result in an increase in movement of a substance across a membrane.

Question 21

Transduction

Answer 21

a major process of membranes that refers to the conversion of one form of energy to another.

Question 22

Translocation

Answer 22

a major process of membranes that refers to the selective movement of substances from one location to another.

Question 23

Phospholipids

Answer 23

• derived from either glycerol (phosphoglycerides) or sphingosine (sphingomyelin)
• hydrophobic fatty acid tails; probably what decreases the membrane’s permeability to polar molecules
• hydrophilic heads

Question 24

Glycolipids

Answer 24

sugar containing lipids found mostly in plasma membranes.

-derived from sphingosine (like sphingomyelin)

Question 25

Cholesterol

Answer 25

- Some plasma membranes contain one molecule of cholesterol for every molecule of phospholipid. - smaller cholesterol molecules serve to add stability to the membrane and tends to decrease its fluid nature and increase its viscosity. - Also prevents cystallization of fatty acyl chains by fitting between them. - Cholesterol is largely nonpolar, hydrophobic but when combined with protein, its solubility in water increases.

Question 26

Common activities of membranes

Answer 26

1. Receptor sites- for hormones and other chemical messengers 2. Energy Conversion- oxidative phosphorylation, which produces ATP, occurs on mitochondrial membranes 3. Transcellular Transport and Extracellular Communication- molecules are transported through the membrane by a variety of ways (active and passive) 4. Intracellular Compartmentalization- divides the cytoplasm into structures such as the nucleus, endoplasmic reticulum, and Golgi apparatus

Question 27

3 major classes of membrane lipids

Answer 27

1. phospholipids 2. glycolipids 3. cholesterol

Question 28

Integral vs peripheral

Answer 28

Membrane proteins are classified as either integral or peripheral on the basis of how well they can be dissociated from the membrane.

Question 29

Integral Proteins

Answer 29

- interact very extensively with the hydrocarbon chains; only be released by agents that can compete for these non-polar interactions (detergents); disruption of the bilayer is necessary to remove these. - membrane-spanning proteins man span the membrane once or a number of times. - have both hydrophobic and hydrophilic portions - provides a lot of the asymmetry of the membrane - some may serve as receptor sites; a class that serve as receptors for hormones, neurotransmitters, and some drugs are couple to G proteins and are termed G protein-coupled receptors; span membrane with 7 alpha-helical domains; outer portion contain ligand binding site, inner portion binds to G protein.

Question 30

Peripheral proteins

Answer 30

- bound to membranes by electrostatic and hydrogen bonds; more easily disrupted - Water-soluble - some bound to surface of integral proteins

Question 31

Functions of cell membrane proteins

Answer 31

1. structural elements- and within and between cells (tight junctions) 2. enzymes- surface or cytoplam 3. receptors- ligand will evoke intracellular changes 4. transporters- carriers or channels

Question 32

Aquaporins

Answer 32

water channels in membrane

Question 33

Carbohydrate of cell membranes

Answer 33

- cell membranes may contain 2-10% carbohydrate. - associated with either lipids or proteins on the outer surface of the cell - Function: interaction between cells, structural

Question 34

Osmosis

Answer 34

movement of water from an area of higher concentration to an area of lower concentration.

Question 35

Key determinants of Diffusion

Answer 35

lipid solubility, size, and charge

Question 36

Passive Transport

Answer 36

- Does not require an input of chemical energy - Simple Diffusion - Facilitated Diffusion

Question 37

Simple Diffusion

Answer 37

- type of passive transport - does not require an input of chemical energy - small, non-polar molecule passes through a membrane

Question 38

Facilitated Diffusion

Answer 38

- does not require an input of chemical energy - movement of molecules from a higher concentration to a lower concentration with the help of proteins found in the membrane. - gated channels allow ions and small polar molecules to pass through at certain times. - Protein carriers assist larger molecules; important characteristic: specificity, saturation, competition

Question 39

Symporters (sodium, potassium, and chloride)

Answer 39

name for transporters that transport ions in the same direction

Question 40

Antiporters (sodium and hydrogen)

Answer 40

transport ions in opposite directions

Question 41

Uniporters (glucose)

Answer 41

transport only single molecules

Question 42

Active Transport

Answer 42

- May also be called a pump - Movement of substances from an area of low concentration to an area of high concentration - ATP required

Question 43

ATPases

Answer 43

name for many of the active transporters

Question 44

Sodium/ Potassium pump

Answer 44

-one of the cell's most vital active pump mechanisms 50% of cell's energy supply -

Question 45

Secondary active transport

Answer 45

- takes advantage of the concentration gradient that exists for many ions - The downhill transport of one molecule provide the energy for the uphill transport of another molecule - countertransport= opposite direction - cotransport= same direction

Question 46

transcytosis

Answer 46

transport of substances across the cell; endocytosis and exocytosis