LSU Bio 1201 Exam 2 Questions With Verified
Answers
why are membranes called phospholipid bilayers?
phospholipids have hydrophilic head and hydrophobic tail, hydrophobic face inside of cell making 2
layers
what is meant by fluid mosaic?
Mosaic of proteins drifting laterally in fluid bilayer of phospholipids
how are membranes adjusted for different temperatures?
membrane fluidity adjusted by changing the ratio of unsaturated to saturated fatty acids
how do the relative amounts of saturated and unsaturated fats change?
if you are in a cold environment you want more saturated fats for your membranes to be fluid; warm
environment you want more saturated fats to make your membranes more solid
what is meant by membrane fluidity?
not too solid, not too fluid
why is fluidity an important property?
preserves membrane function
Henrique and Hanson performed experiments with pigs and examined the effects on the relative
amounts of saturated and unsaturated fats. What did they find?
found that membrane fluidity can acclimate to temperature; pigs raised wearing underwear in a hot
room had subcutaneous fats with higher melting point
what types of molecules can move easily across the membrane?
small nonpolar molecules, gases, steroid hormones, and water
what is simple diffusion?
down the concentration gradient; does not require supplied energy; does not use a carrier molecule
what is facilitated diffusion?
down the concentration gradient; employs carrier molecule; does not require supplied energy
what is active transport?
work must me done; must use supplied energy; employs carrier molecule
for which transport processes are carrier molecules involved?
facilitated diffusion and active transport
which transport processes require the input of additional energy?
active transport
, what is a semi-permeable barrier?
only some types of molecules pass through
when equilibrium is reached in diffusion: does movement of molecules stop?
no
when equilibrium is reached in diffusion: does the net movement of molecules stop?
yes
what is meant by hypertonic?
lower water potential; more solutes dissolved; tend to gain water via osmosis
what is meant by hypertonic?
higher water potential; fewer solutes dissolved; will tend to lose water via osmosis
isotonic
equivalent water potential; equal number of solutes; no note movement of water
in which direction does water flow?
osmosis and the direction of net water movement
what are aquaporins?
channel proteins which facilitate water diffusion through the membrane
marine bony fish are...?
hypotonic to seawater
how do enzymes work?
they position the reactants in a conformation more favorable for the chemical reaction to occur
what aspects of the energetics do enzymes change?
enzymes lower activation energy barrier ΔG⧧
what aspects of energetics do enzymes not affect?
they do not reverse an energetically unfavorable reactions; they do not make a reaction go uphill
how are substrates lured into the active site?
positively charged arginine sidechain lures the negatively charged substrate into the active site
what are the analogs to these characters in the binding of substrates to enzymes?
Siren song= positively charged arginine sidechain
Negatively charged substrate= Odysseus' men
Answers
why are membranes called phospholipid bilayers?
phospholipids have hydrophilic head and hydrophobic tail, hydrophobic face inside of cell making 2
layers
what is meant by fluid mosaic?
Mosaic of proteins drifting laterally in fluid bilayer of phospholipids
how are membranes adjusted for different temperatures?
membrane fluidity adjusted by changing the ratio of unsaturated to saturated fatty acids
how do the relative amounts of saturated and unsaturated fats change?
if you are in a cold environment you want more saturated fats for your membranes to be fluid; warm
environment you want more saturated fats to make your membranes more solid
what is meant by membrane fluidity?
not too solid, not too fluid
why is fluidity an important property?
preserves membrane function
Henrique and Hanson performed experiments with pigs and examined the effects on the relative
amounts of saturated and unsaturated fats. What did they find?
found that membrane fluidity can acclimate to temperature; pigs raised wearing underwear in a hot
room had subcutaneous fats with higher melting point
what types of molecules can move easily across the membrane?
small nonpolar molecules, gases, steroid hormones, and water
what is simple diffusion?
down the concentration gradient; does not require supplied energy; does not use a carrier molecule
what is facilitated diffusion?
down the concentration gradient; employs carrier molecule; does not require supplied energy
what is active transport?
work must me done; must use supplied energy; employs carrier molecule
for which transport processes are carrier molecules involved?
facilitated diffusion and active transport
which transport processes require the input of additional energy?
active transport
, what is a semi-permeable barrier?
only some types of molecules pass through
when equilibrium is reached in diffusion: does movement of molecules stop?
no
when equilibrium is reached in diffusion: does the net movement of molecules stop?
yes
what is meant by hypertonic?
lower water potential; more solutes dissolved; tend to gain water via osmosis
what is meant by hypertonic?
higher water potential; fewer solutes dissolved; will tend to lose water via osmosis
isotonic
equivalent water potential; equal number of solutes; no note movement of water
in which direction does water flow?
osmosis and the direction of net water movement
what are aquaporins?
channel proteins which facilitate water diffusion through the membrane
marine bony fish are...?
hypotonic to seawater
how do enzymes work?
they position the reactants in a conformation more favorable for the chemical reaction to occur
what aspects of the energetics do enzymes change?
enzymes lower activation energy barrier ΔG⧧
what aspects of energetics do enzymes not affect?
they do not reverse an energetically unfavorable reactions; they do not make a reaction go uphill
how are substrates lured into the active site?
positively charged arginine sidechain lures the negatively charged substrate into the active site
what are the analogs to these characters in the binding of substrates to enzymes?
Siren song= positively charged arginine sidechain
Negatively charged substrate= Odysseus' men
