Membranes

Question 1

selective permeability

Answer 1

an important porperty of biological membranes; some substances can cross more easily than others

Question 2

amphipathic

Answer 2

having both a hydrophilic region and a hydrophobic region; like a phospholipid

Question 3

fluid mosaic model

Answer 3

the membrane is a fluid structure with a “mosaic” of various proteins embedded in or attached to the phospholipid bilayer; parts can fluctuate around laterally

Question 4

what effect does cholesterol have on membrane fluidity?

Answer 4

cholesterol acts as a “fluidity buffer” by reducing fluidity at high temps and reducing rigidity at low temps

Question 5

normal fluidity of membranes?

Answer 5

like salad oil

Question 6

integral proteins

Answer 6

membrane proteins that penetrate into the hydrophobic interior of the lipid bilayer and are bound by hydrophobic interactoins; transmembrane proteins span the membrane

Question 7

peripheral proteins

Answer 7

membrane proteins that are loosely/reversibly bound to the inside surface of the membrane, often exposed to parts of integral proteins

Question 8

some functions of membrane proteins

Answer 8

transport; enzymatic activity; signal transduction; cell-cell recognition; intercellular joining; attachment to the cytoskeleton and extracellular matrix (ECM)

Question 9

glycolipids

Answer 9

carbohydrates covalently bonded to lipids; ex: some membrane carbohydrates are attached to lipids in the plasma membrane; plays a role in cell-cell recognition

Question 10

glycoproteins

Answer 10

carbohydrates covalently bonded to proteins; ex: some membrane carbohydrates are attached to proteins in the plasma membrane; plays a role in cell-cell recognition

Question 11

where are membrane proteins and lipids synthesized?

Answer 11

the ER

Question 12

where are carbohydrates added to transmembrane proteins? where are they modified?

Answer 12

the ER (making glycoproteins); can be modified in the Golgi apparatus

Question 13

where are carbohydrates added to transmembrane lipids?

Answer 13

the Golgi apparaus (making glycolipids)

Question 14

what transports glycoproteins, glycolipids, and secretory proteins to the plasma membrane?

Answer 14

vesicles

Question 15

what things can/cannot easily pass directly through the lipid bilayer?

Answer 15

can pass: small non-polar molecules (hydrocarbons, carbon dioxide, oxygen); can’t pass: large, or polar molecules (ions, sugars, proteins, water)

Question 16

transport proteins

Answer 16

transmembrane proteins that allow specific things to move in or out of the cell; can be passive (uses diffusion) or active (requires energy)

Question 17

channel proteins

Answer 17

a kind of passive transport protein that makes a channel that certain molecules or ions can travel through; facilitated diffusion

Question 18

aquaporins

Answer 18

a kind of channel protein that transports water

Question 19

carrier proteins

Answer 19

a kind of passive transport protein that holds onto its passengers and change shape in a way that shuttles them across the membrane; facilitated diffusion

Question 20

diffusion

Answer 20

the natural movement of things so that they spread out evenly into the available space, equalizing the concentration

Question 21

concentration gradient

Answer 21

a difference in concentrations of a solute, solutes diffuse into areas of lower concentration, down the gradient

Question 22

osmosis

Answer 22

the diffusion of water

Question 23

tonicity

Answer 23

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

Question 24

isotonic

Answer 24

same concentration (a cell in an isotonic solution stays the same)

Question 25

hypertonic

Answer 25

higher concentration (a cell in a hypertonic solution shrivels)

Question 26

hypotonic

Answer 26

lower concentration (a cell in a hypotonic solution swells)

Question 27

osmoregulation

Answer 27

the control of solute concentration and water balance; needed for cells that are exposed to non-isotonic environments, ex: paramecium

Question 28

facilitated diffusion

Answer 28

passive transport aided by proteins; ex: channel and carrier proteins

Question 29

ion channels

Answer 29

channel proteins that transport ions, many are gated channels

Question 30

gated channels

Answer 30

channel proteins which open or close in response to stimulus (electrical, when other things bind to it)

Question 31

active transport

Answer 31

transport across the plasma membrane that uses energy to move solutes against their electrochemical gradients

Question 32

passive transport

Answer 32

transport across the plasma membrane that uses does not use energy to move solutes; solues move down their electrochemical gradient

Question 33

sodium-potassium pump

Answer 33

an active transport system that exchanges 2 Na+ (inside the cell) for 3 K+ (outside the cell) across the plasma membrane of animals

Question 34

membrane potential

Answer 34

the voltage across the membrane; about -100mV; favorable for cations in and anions out

Question 35

electrochemical gradient

Answer 35

the combination of the chemical (from concentration gradient) and electrical (from potential) forces acting on ions

Question 36

electrogenic pump

Answer 36

a transport protein that generates voltage across a membrane, stores energy; ex: sodium-potassium pump in animals, proton pump in plants

Question 37

proton pump

Answer 37

actively transports protons, H+, out of the cell

Question 38

cotransport

Answer 38

when an electrogenic pump indirectly drives some other active transport

Question 39

exocytosis

Answer 39

when a cell secretes stuff via the fusion of vesicles with the plasma membrane

Question 40

endocytosis

Answer 40

when a cell takes in stuff by forming new vesicles from the plasma membrane

Question 41

types of endocytosis

Answer 41

phagocytosis, pinocytosis, receptor-mediated endocytosis

Question 42

phagocytosis

Answer 42

the cell engulfs a particle by extending pseudopodia, creates a food vacuole, lysosome digests it

Question 43

pinocytosis

Answer 43

cell gulps drops of extracellular fluid, makes tiny vesicles, non-specific

Question 44

receptor-mediated endocytosis

Answer 44

ligands bind to receptors, makes vesicle covered in coat proteins, a way of getting specific things into the cell