Membrane Structure and Transport

Question 1

solvent

Answer 1

water the universal solvent for biological solutions

Question 2

solutes

Answer 2

Sugars, proteins, electrolytes, and organic molecules like hormones are examples of the different biological solutes dissolved in water.

Hydrophobic nature is one of the factors that holds the plasma membrane together in this aqueous environment and allows the membrane to perform one of its primary functions—to be a selectively permeable barrier

Question 3

plasma membrane

Answer 3

primarily composed of lipids, making it hydrophobic.

Question 4

selectively permeable

Answer 4

• some substances may freely cross the membrane
• others require assistance to cross
• some substances are not able to cross at all

Question 5

cholesterol

Answer 5

• rigid ring lipid
• randomly distributed throughout hydrophobic region
• gives plasma membrane structural strength

Question 6

carbohydrate chains

Answer 6

• extend from outer surface
• attached to protein or phospholipid
• functions as a signal, coating, or receptor

Question 7

extracellular environment

Answer 7

• outside of cell
• aqueous

Question 8

lipid bilayer

Answer 8

• composed of two rows of phospholipid molecules
• phosphate group head faces outward
• fatty acid tails face inward

Question 9

phosphate group head

Answer 9

• part of phospholipid molecule
• contains a phosphate group
• makes this portion of molecule polar and hydrophilic

Question 10

fatty acid tails

Answer 10

• part of phospholipid molecule
• tails consist of two fatty acid chains
• makes this portion of molecule nonpolar and hyrophobic

Question 11

peripheral protein

Answer 11

• does not extend across lipid bilayer
• may server as an anchor point for cytoskeleton

Question 12

transmembrane proteins

Answer 12

• extends all the way through the lipid bilayer
• may serve as a transport protein or a channel across the bilayer

Question 13

cytoplasm

Answer 13

• inside of the cell
• aqueous
• contains organlelles

Question 14

passive transport

Answer 14

• occurs down the gradient and does not use ATP
• includes simple diffusion, osmosis, facilitated diffusion

Question 15

active transport

Answer 15

• occurs against gradient and requires ATP
• includes primary active transport, secondary active transport, receptor-mediated transport, phagocytosis, and pinocytosis

Question 16

simple diffusion

Answer 16

• driven by the concentration or pressure gradient
• may occur through different media
• may or may not include semipermeable membrane
• gas exchange in lungs or dye spreading through liquid

Question 17

facilitated diffusion

Answer 17

• solute particles move down the gradient
• involves carrier proteins (transporters) in the cell membrane
• glucose transporters across the membrane (GluT)

Question 18

osmosis

Answer 18

• solvent moves down the concentration
• involves semipermeable membrane
• movement of water from hypotonic to hypertonic compartment

Question 19

primary active transport

Answer 19

• moves the substance against the chemical/electrical gradient
• involves direct use of ATP
• Na+/K+ ATPase pump moves K+ into and Na+ out of the cell

Question 20

secondary active transport

Answer 20

• moves the substance against the gradient
• is driven by primary active transport
• no direct use of ATP
• sodium-dependent glucose transporter (SGLT) moves glucose into cell along with Na+

Question 21

receptor-mediated transport

Answer 21

involves membrane surface receptors to internalize the substance

Question 22

phagocytosis

Answer 22

cells ingulf solid particles or bacteria or etc

Question 23

pinocytosis

Answer 23

cells engulf liquid substance

Question 24

diffusion

Answer 24

• high concentration → low concentration
• passive
• driving force is random collision or kinetic energy

Question 25

simple diffusion

Answer 25

• water
• oxygen
• steroid hormones
  ^ all freely move across the cell membrane

Question 26

facilitated diffusion

Answer 26

• ions
• glucose
• amino acids
  ^ need assistance of a channel/transport protein to cross the cell membrane

Question 27

osmosis

Answer 27

• special case of diffusion
• needs selectively permeable membrane (passable to solvent but impassable to solute)

Question 28

hypotonic solution

Answer 28

• named for lower solute concentration
• hypo mess less than
• higher water (solvent) concentration
• net movement of water out of this side

Question 29

hypertonic solution

Answer 29

• higher solute concentration
• hyper means greater than
• lower water (solvent) concentration
• net movement of water towards this side

Question 30

selectively permeable membrane

Answer 30

• water (solvent) freely passes through
• solute molecules cannot pass through

Question 31

isotonic solution

Answer 31

• iso means the same
• equal solute and solvent concentration on both sides of the selectively permeable membrane
• water molecules continue to cross the membrane but no net movement

Question 32

with time, water moves down the gradient

Answer 32

• from hypotonic solution
• toward hypertonic solution
• goal is to reach equilibrium

Question 33

Osmotic pressure

Answer 33

the pressure generated within a cell as water presses against the plasma membrane

Question 34

isotonic solution for RBC

Answer 34

• equal solute concentration on both sides of the membrane’
• no concentration gradient
• no net movement of water
• no change in RBC shape

Question 35

hypotonic solution for RBC

Answer 35

• smaller solute concentration outside membrane
• concentration gradient exists
• net flow of water INTO the RBC
• RBC swells and may lyse (burst)

Question 36

hypertonic solution in RBC

Answer 36

• greater solute concentration outside membrane
• concentration gradient exists
• net flow of water OUT of RBC
• RBC crenates (shrink)