Chapter 7

Question 1

Plasma membrane

Answer 1

Exhibits selective permeability allowing some substances to cross easier than others

Question 2

What does plasma membrane consist of?

Answer 2

Phospholipid bilayer(most abundant component) ; Amphipathic (hydro philic and phobic)

Question 3

How is plasma membrane fluid mosaic

Answer 3

Lipids and proteins float and move within the membrane, embedded proteins are held by hydrogen regions, most lipids and proteins move move laterally, in animal cells the PM includes a ECM containing 25% cholesterol which regulates membrane fluidity

Question 4

PM fluidity is influenced by:

Answer 4

Temperature (hibernating animals, ectothermic animals, endothermic animals) ; Composition (unsaturated fatty acids, cholesterol)

Question 5

Types of membrane proteins

Answer 5

Peripheral proteins (bound to the surface of the membrane), integral proteins (penetrate the hydrophobic core), transmembrane proteins (integral proteins that span the membrane)

Question 6

Transmembrane proteins

Answer 6

R group can be nonpolar and hydrophobic or polar and hydrophilic ; characteristics determine if protein is inserted into nonpolar bilayer and how

Question 7

What are the functions of cell-surface membrane proteins?

Answer 7

Transport, enzymatic activity, signal transduction, cell-cell recognition, intercellular joining, attachment to the cytoskeleton and ECM

Question 8

Peripheral and transmembrane protein functions

Answer 8

Cell-cell recognition, transmembrane protein regulation of transport (passive vs active)

Question 9

Cell-cell recognition

Answer 9

Distinguish one type of neighboring cell from another, crucial to the functioning of an organism, cells recognize other cell by binding to surface molecules

Question 10

What are recognition sites?

Answer 10

Cell membrane carbohydrates ; glycolipid=carb+lipid, glycoproteins=carb+protein, proteoglycan=protein+longer carb chains

Question 11

Why is a cell’s surface proteins medically important?

Answer 11

HIV must bind to the immune cell-surface protein CD4 and a “co-receptor” CCR5 in order to infect

Question 12

What key roles do transmembrane proteins play in regulating transport?

Answer 12

Hydrophobic (nonpolar) molecules can dissolve in the lipid bilayer and pass through the he membrane rapidly ; Polar and hydrophilic molecules don’t cross the membrane easily

Question 13

Passive transport

Answer 13

Doesn’t require metabolic energy (substance moves down concentration gradient)

Question 14

Active transport

Answer 14

Does require input of metabolic energy (substance moves against its concentration gradient)

Question 15

Diffusion

Answer 15

Random movement toward equilibrium ; net movement from regions of greater concentrations to lesser concentrations

Question 16

Passive transport (more info)

Answer 16

Can occur by simple diffusion through the phospholipid bilayer ; speed of diffusion depends on: size of molecule, temperature of solution, concentration gradient

Question 17

Osmosis

Answer 17

Diffusion of water ; depends on the concentration of water molecules on either side of the membrane (water moves down its concentration gradient)

Question 18

Osmoregulation

Answer 18

The control of solute concentrations and water balance ; necessary adaptation for life in such environments ; hypertonic or hypotonic environments create osmotic problems for organisms that have cells without rigid walls

Question 19

Facilitated diffusion

Answer 19

Passive transport that requires channel proteins or carrier proteins ; considered passive b/c there is no ATP

Question 20

Channel protein

Answer 20

Form channels across the membrane through which some substances can pass ; high specificity

Question 21

Aquaporins

Answer 21

Channels that allow large amounts of water to move along its concentration gradient

Question 22

Active transportation

Answer 22

Uses energy to move solutes against their gradient ; requires ATP ; allows cells to maintain concentration gradients that differ form their surroundings

Question 23

How does ATP release energy?

Answer 23

It stores energy in the last phosphate bond ; when the last bond is broken (hydrolysis) the energy is released and ATP is converted into ADP

Question 24

Voltage across plasma membrane

Answer 24

Na+/K+ pumps create differences in ions across the membrane (voltage) ; voltage across membrane is called membrane potential ; inside of cell is negative compared to the outside

Question 25

Electrogenic pumps

Answer 25

Animal cells=sodium potassium pump, plant cells=proton pump ; electrogenic pumps help store energy that can be used for cellular work

Question 26

Bulk transport

Answer 26

Occurs by exocytosis and endocytosis across PM ; requires energy ; small molecule and water enter or leave through lipid bilayer via transport proteins, large molecule cross the membrane via vesicles

Question 27

Types of endocytosis

Answer 27

Phagocytosis (cellular eating), pinocytosis (cellular drinking), receptor-mediated endocytosis

Question 28

Phagocytosis

Answer 28

Specialized cell engulf large solid particle or another cell ; food vesicle (phagosome) forms and usually fuses w/ a lysosome where the contents are digested

Question 29

Pinocytosis

Answer 29

Molecules dissolved in droplets are taken up when extracellular fluid is “gulped” into tiny vesicles

Question 30

Receptor-medicated endocytosis

Answer 30

Binding of specific solves to receptors triggers vesicle formation ; receptor proteins, receptors, and other molecules form the extracellular fluid are transported in the vesicles ; emptied receptors are recycled to the plasma membrane