Biology 105 Exam 2 with 100%
correct answers (graded A+)
what is the structure of a membrane? - answer phospholipid bilayer:
hydrophilic heads & hydrophobic tails (hydrophobic interactions) + proteins
embedded in the protein
what are the features of membranes? - answer 1) barrier separating what's
inside & outside of the cell
2) serves as an anchor or a site where proteins can carry out functions
3) proteins are important for getting nutrients in & out (gates, pumps)
4) very few molecules can get in or out without assistance
what is the difference between diffusion & osmosis? - answer **DIFFUSION**
is the movement of molecules from a low concentration to a high
concentration until equilibrium
**OSMOSIS** is the diffusion of water across a membrane
how to figure osmosis: - answer solutes OUTSIDE the cell compared to INSIDE
the cell
isotonic: - answer normal: solute concentration is the same outside &
inside // water concentration is the same as well
hypertonic: - answer dehydration / shriveled cell: more solutes outside of the
cell than on the inside // water goes out
hypotonic: - answer hydration / cell swells: fewer solutes outside the cell than
inside // water goes in
, passive diffusion: - answer directly across the membrane if the concentration
gradient is high to low *no energy needed*
CAN PASS: gases, non-polar molecules (if small), polar (slowly)
CANNOT PASS: ions
facilitated diffusion: - answer the protein in membranes facilitate the
transport of molecules past the lipid part // use carrier proteins & ion
channels *no energy needed*
ion channels: - answer "hole" in membrane that is always gated, ions move
through if there is a high concentration until the gate closes // don't interact
with substance
carrier proteins: - answer very specific as they bind in different ways to
different molecules (act like enzymes), change shape & "dump" it into cell //
lock & key fit
active transport: - answer carrier proteins that require energy from an energy
source like ATP or electrical energy
how does ATP work as an energy source? - answer energy is in the phosphate
groups, one falls off to release a "flash of energy", turns into ADP +
phosphate group which is energy that a cell can use
electrical energy: - answer establish an ion gradient like a battery by using
ATP to pump ions across the membrane
equilibrium - answer equal amount of solutes & water - no net change (only
random movement: 1 in & 1 out)
endocytosis - answer "endo" means inward
moves materials into the cell through a membrane vesicle
correct answers (graded A+)
what is the structure of a membrane? - answer phospholipid bilayer:
hydrophilic heads & hydrophobic tails (hydrophobic interactions) + proteins
embedded in the protein
what are the features of membranes? - answer 1) barrier separating what's
inside & outside of the cell
2) serves as an anchor or a site where proteins can carry out functions
3) proteins are important for getting nutrients in & out (gates, pumps)
4) very few molecules can get in or out without assistance
what is the difference between diffusion & osmosis? - answer **DIFFUSION**
is the movement of molecules from a low concentration to a high
concentration until equilibrium
**OSMOSIS** is the diffusion of water across a membrane
how to figure osmosis: - answer solutes OUTSIDE the cell compared to INSIDE
the cell
isotonic: - answer normal: solute concentration is the same outside &
inside // water concentration is the same as well
hypertonic: - answer dehydration / shriveled cell: more solutes outside of the
cell than on the inside // water goes out
hypotonic: - answer hydration / cell swells: fewer solutes outside the cell than
inside // water goes in
, passive diffusion: - answer directly across the membrane if the concentration
gradient is high to low *no energy needed*
CAN PASS: gases, non-polar molecules (if small), polar (slowly)
CANNOT PASS: ions
facilitated diffusion: - answer the protein in membranes facilitate the
transport of molecules past the lipid part // use carrier proteins & ion
channels *no energy needed*
ion channels: - answer "hole" in membrane that is always gated, ions move
through if there is a high concentration until the gate closes // don't interact
with substance
carrier proteins: - answer very specific as they bind in different ways to
different molecules (act like enzymes), change shape & "dump" it into cell //
lock & key fit
active transport: - answer carrier proteins that require energy from an energy
source like ATP or electrical energy
how does ATP work as an energy source? - answer energy is in the phosphate
groups, one falls off to release a "flash of energy", turns into ADP +
phosphate group which is energy that a cell can use
electrical energy: - answer establish an ion gradient like a battery by using
ATP to pump ions across the membrane
equilibrium - answer equal amount of solutes & water - no net change (only
random movement: 1 in & 1 out)
endocytosis - answer "endo" means inward
moves materials into the cell through a membrane vesicle
