LSU BIO 1201 EXAM 2 QUESTIONS AND ANSWERS
Why are membranes called phospholipid bilayers? - answers :phospholipids have
hydrophilic head and hydrophobic tail, hydrophobic face inside of cell making 2 layers
What is meant by fluid mosaic? - answers :mosaic of proteins drifting laterally in fluid
bilayer of phospholipids
How are membranes adjusted for different temperatures? - answers :membrane fluidity
adjusted by changing the ratio of unsaturated to saturated fatty acids
How do the relative amounts of saturated and unsaturated fats change? - answers :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? - answers :not too solid, not too fluid
Why is fluidity an important property? - answers :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? - answers
:found that membrane fluidity can acclimate to temperature; pigs raised wearing
underwear in a hot room had subcutaneous fats with higher melting point
What is a semi-permeable barrier? - answers :only some types of molecules pass
through
When equilibrium is reached in diffusion: does movement of molecules stop? - answers
:no
When equilibrium is reached in diffusion: does the net movement of molecules stop? -
answers :yes
What is meant by hypertonic? - answers :lower water potential; more solutes dissolved;
tend to gain water via osmosis
What is meant by hypertonic? - answers :higher water potential; fewer solutes
dissolved; will tend to lose water via osmosis
Isotonic - answers :equivalent water potential; equal number of solutes; no note
movement of water
In which direction does water flow? - answers :osmosis and the direction of net water
movement
, What are aquaporins? - answers :channel proteins which facilitate water diffusion
through the membrane
Marine bony fish are...? - answers :hypotonic to seawater
How do enzymes work? - answers :they position the reactants in a conformation more
favorable for the chemical reaction to occur
What aspects of the energetics do enzymes change? - answers :enzymes lower
activation energy barrier δg⧧
What aspects of energetics do enzymes not affect? - answers :they do not reverse an
energetically unfavorable reactions; they do not make a reaction go uphill
What types of molecules can move easily across the membrane? - answers :small
nonpolar molecules, gases, steroid hormones, and water
What is simple diffusion? - answers :down the concentration gradient; does not require
supplied energy; does not use a carrier molecule
What is facilitated diffusion? - answers :down the concentration gradient; employs
carrier molecule; does not require supplied energy
What is active transport? - answers :work must me done; must use supplied energy;
employs carrier molecule
For which transport processes are carrier molecules involved? - answers :facilitated
diffusion and active transport
Which transport processes require the input of additional energy? - answers :active
transport
How are substrates lured into the active site? - answers :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? -
answers :siren song= positively charged arginine sidechain
Negatively charged substrate= odysseus' men
Circe= active site
How do temperature changes affect the rates of reactions catalyzed by enzymes? -
answers :temperature is a measure of how many molecules will have achieved
activation energy; low temp= low energy associated with molecule
What is meant bby the thermostability of an enzyme? - answers :able to remain stable
and function at high temperatures
Why are membranes called phospholipid bilayers? - answers :phospholipids have
hydrophilic head and hydrophobic tail, hydrophobic face inside of cell making 2 layers
What is meant by fluid mosaic? - answers :mosaic of proteins drifting laterally in fluid
bilayer of phospholipids
How are membranes adjusted for different temperatures? - answers :membrane fluidity
adjusted by changing the ratio of unsaturated to saturated fatty acids
How do the relative amounts of saturated and unsaturated fats change? - answers :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? - answers :not too solid, not too fluid
Why is fluidity an important property? - answers :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? - answers
:found that membrane fluidity can acclimate to temperature; pigs raised wearing
underwear in a hot room had subcutaneous fats with higher melting point
What is a semi-permeable barrier? - answers :only some types of molecules pass
through
When equilibrium is reached in diffusion: does movement of molecules stop? - answers
:no
When equilibrium is reached in diffusion: does the net movement of molecules stop? -
answers :yes
What is meant by hypertonic? - answers :lower water potential; more solutes dissolved;
tend to gain water via osmosis
What is meant by hypertonic? - answers :higher water potential; fewer solutes
dissolved; will tend to lose water via osmosis
Isotonic - answers :equivalent water potential; equal number of solutes; no note
movement of water
In which direction does water flow? - answers :osmosis and the direction of net water
movement
, What are aquaporins? - answers :channel proteins which facilitate water diffusion
through the membrane
Marine bony fish are...? - answers :hypotonic to seawater
How do enzymes work? - answers :they position the reactants in a conformation more
favorable for the chemical reaction to occur
What aspects of the energetics do enzymes change? - answers :enzymes lower
activation energy barrier δg⧧
What aspects of energetics do enzymes not affect? - answers :they do not reverse an
energetically unfavorable reactions; they do not make a reaction go uphill
What types of molecules can move easily across the membrane? - answers :small
nonpolar molecules, gases, steroid hormones, and water
What is simple diffusion? - answers :down the concentration gradient; does not require
supplied energy; does not use a carrier molecule
What is facilitated diffusion? - answers :down the concentration gradient; employs
carrier molecule; does not require supplied energy
What is active transport? - answers :work must me done; must use supplied energy;
employs carrier molecule
For which transport processes are carrier molecules involved? - answers :facilitated
diffusion and active transport
Which transport processes require the input of additional energy? - answers :active
transport
How are substrates lured into the active site? - answers :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? -
answers :siren song= positively charged arginine sidechain
Negatively charged substrate= odysseus' men
Circe= active site
How do temperature changes affect the rates of reactions catalyzed by enzymes? -
answers :temperature is a measure of how many molecules will have achieved
activation energy; low temp= low energy associated with molecule
What is meant bby the thermostability of an enzyme? - answers :able to remain stable
and function at high temperatures
