Membrane Structure and Function

Question 1

Selective Permeability

Answer 1

plasma membrane allows only some specific substances to pass into or out of the cell (small, hydrophobic molecules pass through the membrane better)

Question 2

Amphipathic

Answer 2

a molecule that has a hydrophilic and hydrophobic region (like phospholipids)

Question 3

Fluid Mosaic Model

Answer 3

plasma membrane is a mosaic of protein molecules in a fluid bilayer of phospholipids

Question 4

The Fluidity of Membranes

Answer 4

held together by hydrophobic interactions (weaker than other bonds)

Question 5

Unsaturated hydrocarbon tails (with kinks)

Answer 5

prevents phospholipids from packing together (more fluid) even when temperature decreases

Question 6

Saturated hydrocarbon tails (without kinks)

Answer 6

tails pack together (less fluid), increases membrane viscosity

Question 7

Cholesterol in cell membrane

Answer 7

reduces membrane fluidity at medium/high temperatures and hinders full solidification at lower temperatures

Question 8

Membrane proteins

Answer 8

different determine plasma membrane’s functions (include transports, enzymatic activity, signal transduction, cell-cell recognition, intercellular joining, attachment to cytoskeleton and extracellular matrix)

Question 9

Integral proteins

Answer 9

Penetrate hydrophobic region of lipid bilayer

Question 10

Transmembrane proteins

Answer 10

type of integral protein, span entire hydrophobic interior (span full membrane)

Question 11

Peripheral proteins

Answer 11

not embedded on lipid bilayer, loosely bond (often to parts of integral proteins)

Question 12

Transport proteins

Answer 12

proteins that help large/hydrophilic molecules pass through the membrane

Question 13

Channel proteins

Answer 13

a type of transport protein that has a channel which certain molecules can pass through (ex: aquaporins for water)

Question 14

Carrier proteins

Answer 14

a type of transport proteins which holds onto certain molecules and shuttles them across the membrane

Question 15

Diffusion

Answer 15

the movement of particles from a high concentration region to a low concentration region (down its concentration gradient)

Question 16

Passive transport

Answer 16

the diffusion of a substance across a biological membrane

Question 17

Osmosis

Answer 17

the diffusion of water across a selectively permeable membrane

Question 18

Tonicity

Answer 18

the ability of a solution surrounding the cell to cause a sell to gain or lose water

Question 19

Isotonic

Answer 19

the level of tonicity where there is no net movement of water across the plasma membrane

Question 20

Hypertonic

Answer 20

the level of tonicity where there is a higher net movement of water out of the plasma membrane (increase in salinity in surrounding solutions can cause this)

Question 21

Hypotonic

Answer 21

the level of tonicity where there is a higher net movement of water into the plasma membrane

Question 22

Level of Tonicity for Animal Cells vs Plant Cells

Answer 22

Animal Cells - isotonic solution (don’t have cell walls, central vacuole), Plant Cells - hypotonic solution (central vacuole can push excess water out of cell)

Question 23

Facilitated Diffusion

Answer 23

diffusion of polar molecules and ions with the help of transport proteins

Question 24

Ion Channels

Answer 24

channel proteins that transport ions through the plasma membrane

Question 25

Gated Channels

Answer 25

type of ion channel that open/closes in response to a stimulus (usually electrical)

Question 26

Active Transport

Answer 26

transporting a substance across a membrane against the concentration gradient (requires energy through ATP hydrolysis)

Question 27

Sodium-Potassium Pump

Answer 27

Na+ in cytoplasm binds to pump, stimulates phosphorylation, pump affinity to Na+ is reduces, released outside, same process repeats for K+ (3 sodium inside cell for 2 potassium outside cell)

Question 28

Cotransport

Answer 28

a transport protein that can diffuse a solute along with a second substance against the concentration gradient (ie: H+/sucrose pumps)

Question 29

Exocytosis

Answer 29

a transport vesicle from Golgi fuses with the plasma membrane and releases the contents of the vesicle outside the cell, then becomes part of the plasma membrane

Question 30

Endocytosis

Answer 30

part of the plasma membrane pinches off with materials outside the cell and then moves into the cell (the reverse of exocytosis)

Question 31

Phagocytosis

Answer 31

a type of endocytosis where the cell engulfs a particle into a membraneous sac (food vacuole)

Question 32

Pinocytosis

Answer 32

a type of endocytosis where the cell engulfs droplets of extracellular fluid within a vesicle formed by parts of the plasma membrane

Question 33

Receptor-Mediated Endocytosis

Answer 33

a type of pinocytosis where specific proteins are collected after they bind to solutes in the plasma membrane