Lecture 2

Question 1

individual ion and small molecules

Answer 1

• passive transport (concentration gradient)
• phospholipid
• transport proteins
• active transport (against concentration gradient; metabolic energy)
• carrier/transport proteins

Question 2

phospholipid bilayer

Answer 2

• passive diffusion
• movement of solute down its own conc. gradient
• osmosis
• water diffusion from hypotonic (lower solute conc.) to hypertonic (higher colute conc.)

Question 3

tansport proteins (facilitated diffusion)

Answer 3

• channel proteins
• provice hydrophilic passageways which water and small ions can pass
• carrier proteins
• bind with substance; change shape
• transport across membrane

Question 4

carrier/transport proteins

Answer 4

• pumps (primary active transport)
• same carrier proteins transports substance through membrane (hydrolyses ATP to power movement)
• coupled transport
• indirectly powered by ATP hydrolysis
• electrochemical gradient created by primary active transport

Question 5

substances in bulk

Answer 5

• endocytosis
• exocytosis

Question 6

endocytosis

Answer 6

• solids
• phagocytosis
• cell engulfs particle by wrappign pseudopodia around it and packaging in in a membrane-enclose sac
• liquids
• pinocytosis
• cell gulps droplets of extracellular fluid into tiny vesicles

-specific substances
- receptor-mediated
- coated pits form vesicles when specific substances (ligands) bind to receptors on cell surface

Question 7

exocytosis

Answer 7

• bulk import of materials out of cell
• materials packaged in cell inside vesicles and secreted/excreted into extracellular environment

Question 8

diffusion

Answer 8

• tendency for molecules to spread out evenly into available space
• random diffusion of population, molecules may exhibit net movement in one direction
• dynamic equilibrium = as many molecules cross one way as cross in other way
• substances diffuse down individual concentration gradients
• no work done (down)
• passive transport = diffusion across membrane; no energy required from cell

Question 9

water balance of cells

Answer 9

• regulating flow of water in/out
• osmosis = diffusion of water across selectively permeable membrane
• water diffuses across membrane from lower solute conc. to higher solute conc.
• tonicity = ability of solution to cause cell gain/loss

Question 10

tonicity

Answer 10

• isotonic = same conc.; no water flux
• hypotonic = lower conc.; into cell water flux
• hypertonic = higher conc.; out of cel

Question 11

osmoregulation

Answer 11

• control of water balance
• unicellular paramecium (hypertonic) to its pond water environment has contractile vacuole (acts as pump)
• cells maintain water balance
• plant cell in hypotonic solution swells until walls oppose uptake (turgid)
• isotonic = cell becomes flaccid
• hypertonic = membrane pulls away from wall (plasmolysis)

Question 12

facilitated diffusion

Answer 12

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