Chapter 11 Flashcards
what is a chemical reaction?
a process that either forms or breaks chemical bonds that hold atoms together.
dehydration synthesis vs hydrolysis?
in dehydration synthesis, two molecules combine to form a larger molecule with the removal of water.
in hydrolysis, larger molecule is broken down into smaller ones with the addition of water.
all chemical reactions either?
release energy or require an input of energy.
what is an exergonic reaction?
a reaction that releases energy. this means that the reactants contain more energy than the products.
what is an endergonic reaction?
a reaction that requires an input of energy. this means that the products contain more energy than the reactants.
EVERY chemical reaction requires what?
an initial investment of energy.
for every reaction, there is a specific activation energy EA that needs to be present. this refers to?
the amount of initial energy that is required in order for the reactant molecules to CONTORT so the bonds can break
EA is often supplied in the form of?
heat that reactants absorb from the environment, this heat causes the reactants to move more quickly, so they collide more often.
- collisions make the bonds break easily
- once enough energy is absorbed so the bonds can break, EA has been met
for some chemical reactions, the EA is low enough that? or high enough?
they can proceed at room temperature in a short time.
for others, the EA is very high, and at room temperature, the reaction may proceed at an unnoticeable rate.
sucrose = glucose + fructose reaction? fast or slow at room temp?
its very slow at room temperature
to increase the proportion of molecules with enough energy, it means?
- heating: raising the temperature increases collisions. BUT, the problem is heat can kill cells, and not all chemical reactions would speed up.
- decreasing the EA: decreasing EA ensures that a greater proportion of molecules will collide in order for the reaction to occur.
- EA can be decreased by the use of a catalyst, in biological systems a catalyst is called an enzyme, it is a protein.
enzymes dont change the reaction in any way, they?
just speed up the reaction: enable reactant to absorb enough energy to reach their transition state.
what is the effect of enzymes on reaction rate?
enzymes lower the EA: less collisions need to happen in order for the transition state to be reached
what is the substrate?
reactant an enzyme acts on. enzyme is specific based on active site shape.
what is the enzyme?
protein that binds to the substrate forming an enzyme substrate complex.
what is the active site?
region on the enzyme where the substrate binds.
induced fit enzyme?
the shape of an enzyme changes slightly when the substrate enters: due to the chemical groups of the substrate and the amino acids that make up the active site.
the active site can lower EA by?
- orienting the substrates correctly to help the reaction occur
- straining substrate bonds
- providing an environment that is favorable for the reaction to occur
an enzymes activity is affected by?
general environmental factors
each enzyme has an?
optimal temperature in which it functions, optimal pH in which it can function
what may happen to an enzyme if environmental conditions change?
protein becomes denatured
and becomes biologically inactive
many enzymes require?
cofactors for activity: not made of protein
what are some inorganic cofactors?
metal atoms such as zinc, copper, iron
what are some organic cofactors?
called coenzymes: most vitamins are coenzymes.
- may be bound permanently to the enzyme or bind loosely with the substrate.
