Study Questions # 5 Flashcards
September 24-28
What is metabolism, and what is the difference between anabolism and catabolism?
chemical reactions that occur in living cells.
anabolism builds bigger molecules and catabolism breaks them down
Why do cells need energy and what is the difference between potential energy and kinetic energy?
They need energy to do work. Potential energy is stored energy waiting to be used and kinetic energy is the energy that is being used.
What are the first and second laws of thermodynamics?
- energy can only be transferred, not created or destroyed
2. entropy is always increasing
What is free energy?
energy available to do work
- includes enthalpy (H) energy in chemical bonds
- 2 disordering influences: T and entropy
- ordering influences-disordering influences
- ΔG=ΔH-TΔS
How can you predict in which direction a reaction will proceed?
use ΔG
- exergonic reaction: -ΔG, products have less energy than reactants
- endergonic reaction: +ΔG, reactants have less energy than products
What is an exergonic reaction and how does it differ from an exothermic reaction?
exergonic reaction- releases energy, products contain less free energy or more disorder than reactants
exothermic-releases heat
Why can’t thermodynamics tell you how fast a reaction will go?
need to know activation energy to determine this; first need to break existing bonds; reactions with high activation energies proceed more slowly
What is activation energy?
energy needed to start a reaction
What is a catalyst?
substance that speeds up the rate of a chemical reaction
What is an enzyme and why do cells need enzymes?
biological catalyst
increases rate of reaction by lowering activation energy
controls metabolism
How do enzymes work?
Lower activation energy needed to start a chemical reaction
Why can some RNA molecules catalyze reactions?
ribozymes can change shape and put pressure on existing bonds
What is an active site?
the position in an enzyme where substrates bind
What is the difference between the lock and key and induced fit models?
lock and key is when the active site is an exact shape and the substrate has to fit just right. The induced fit model is that the active site changes shape to mold to the substrate
Why is the induced fit model favored?
explains how enzyme stresses bonds of substrate
explains why enzyme releases products
What is the catalytic cycle of an enzyme?
- free substrate and enzyme
- substrate binds enzyme
- active site changes shape
- reaction occurs
- products released, restart
Why do we know that binding and catalysis are separate activities?
some drugs prevent binding, some prevent catalysis
Why can we measure an enzymes activity by measuring the rate at which its products accumulate?
if enzyme works, products will form
What factors affect how well enzymes work?
pH and temperature, concentration of the substrate, concentration of the enzyme, presence of inhibitors, presence of coenzymes, rate of enzyme production
How does temperature affect enzyme activity?
temperature increases enzyme activity to a point until the enzyme breaks down
What is the difference between competitive and non-competitive inhibitors?
competitive inhibitors bind to active site and block it
noncompetitive inhibitors bind at allosteric site and active site changes shape
How can we tell whether an inhibitor is competitive or non-competitive
if it’s competitive, it can overcome inhibition by adding more substrate and it will out-compete the inhibitor
What is the difference between an active site and an allosteric site?
an active site is where the substrate binds and the allosteric site is where noncompetitive inhibitors or activators bind
What is an activator?
bind enzyme at the allosteric site, keeping enzyme in active configuration to increase enzyme activity
