Cellular Respiration Flashcards
Metabolism
the sum of all chemical reactions in a cell or organism
Energy
The ability to do work
work: moving an object against an opposing force
Kinetic energy
the energy of motion, performs work by making objects move
Potential energy
Energy that is stored within an object and dependent on
-chemical structure
-location
To break a bond..
energy is absorbed since you need energy to pull reactants away
To form a bond..
energy is released
During a chemical reaction bonds ________ and bonds __________
Bonds break in reactant molecules and form in product molecules
Bond energy
Energy required to break bonds
Activation energy
The minimum amount of energy required to break bonds in reactants and start a reaction
Transition state
The intermediate state where bonds are breaking in reactants and forming in products
Exothermic
when there is a overall release of energy
-lower activation energy
-reactants have more energy than products
Endothermic
when there is an overall absorption of energy
-products have more energy than reactants
-more activation energy required
How do living organisms maintain their highly ordered structures?
Although the entropy of the universe is always increasing by expending energy, cells are able to maintain their highly ordered structures.
ATP composition
three (-) charged phosphate groups which give it its energy, adenine, and a ribose sugar
Adenosine triphosphate
What is ATP hydrolysis
water breaking apart atp molecules into adp and an inorganic phosphate and H+ ion
ATP cycle
ATP turns into ADP and Pi by releasing free energy and using water -> exergonic
ADP and Pi turns into ATP by absorbing energy and releasing water -> endergonic
Phosphorylation
the transfer of a phosphate group from ATP to another molecule to energize the reaction
Enzymes
enzymes are biological catalysts proteins that speed up a chemical reaction by lowering its activation energy without being consumed or changing products
Substrate
the molecule that binds onto the enzyme
What is the active site
The site where substrates bind onto the enzyme
How are enzymes usually named
-ase
What is the lock and key model of the enzyme. Why is it not accurate?
The model that specific substrates are keys and enzymes are locks. It was not accurate because it could not explain why certain substrates could not bind to certain enzymes since enzymes are very specific and won’t just bind to every substrate
Induced-fit hypothesis
The current model of the enzyme which shows that enzymes can undergo a conformational change where it changes shape so the active site can better fit the enzyme and then converts substrates into products
(still specific but after it binds it changes shape)
4 factors affecting enzyme activity
- Enzymes and substrate concentration
- Enzyme inhibitors
- pH
- Temperature
Explain enzyme and substrate concentration effect on enzyme activity
The rate of reaction is proportional to the enzyme concentration.
Increasing the rate of substrates will speed up the reaction up to a certain point, until it plateaus due to to availability of enzymes
Why can enzymes be used so rapidly?
Because they are not used up in a reaction and are able to be reused, also why substrate concentration is more important affecting rate than enzyme conc.
Coenzymes
an organic molecule that acts as a cofactor of an enzyme
What is “saturation level”
when all enzymes are bound to a substrate and the point plateaus
How do enzyme inhibitors affect the enzyme activity
Enzyme inhibitors lower the rate which enzymes catalyze reactions or they could stop them completely
There are two types of enzyme inhibition:
1. competitve
2. non competitiive
-can be done on purpose, or a poison
Competitive Inhibtion
A molecule very similar to the substrates binds to the active site of an enzyme and blocks activity
-decreases the rate of reaction
Noncompetitive Inhibition
When an inhibitor molecule binds to allosteric or non-active site of the enzyme to block activity
-changes shape of the active site
What happens when the concentration of inhibitors are too high?
The reaction will stop completely
pH and temperature affect on enzyme activity
Enzymes have an optimal temperature and pH which they peak at
Temperature=increases rate of reaction (too high can denature the enzyme)
-40C
What is the optimal pH and temperature range of enzymes
Optimal pH = 6-8
Temperature = 40C
What is the allosteric site
Binding site for regulatory molecules (which is not on the active site)
What are regulatory molecules
Molecules that naturally regulate enzyme activity
Allosteric regulation
Molecules bind to allosteric site and cause conformational change which may allow or prevent the substrate from binding
Factors that affect enzymes activity
- Enzymes and substrate concentration
- Enzyme inhibitors
- pH
- Temperature
What happens when products accumulate in excess for enzymes?
Then the regulatory molecules (molecules at end of biochemical pathway) bind to the allosteric site of an enzyme and change the shape.
What does an allosteric activator/inhibitor do?
Activator: Stabilizes the enzyme to a shape that causes its active site to have a high affinity for substrate
Inhibitor: creates an inactive form of the enzyme
The inhibitor molecule changes the shape of an enzyme in such a way that the substrate is released from the active site
What are allosteric inhibitors a product of?
Biochemical pathways
What is feedback inhibtion in enzymes?
When a product is in excess, one of the product molecules part of the biochemical pathway will go back and inhibit the first enzyme of the pathway.
When a product is scarce, the inhibition is reduced and rate of reaction increases.
Why is feedback inhibition so important?
It ensures cellular resources are not being wasted
What do enzymes do to a reaction?
It decreases the activation energy required to start the reaction and forms products quicker
What must happen in a reaction before products form?
Bonds must break in the reactant molecules
Explain a rock on a hill with activation energy
A rock on a hill possesses a lot of potential energy but it cannot move down a hill spontaneously without a push which is the activation energy
Why is increasing temperature not the best way to speed up a chemical reaction?
Although it does speed up the reaction, there are two reasons:
-too high temperature damages the DNA and the proteins
-it speeds up every single reaction occuring in a cell and not just a specific one
-> certain chemical reactions in a cell must be regulated independently and know when to stop/start
Enzymes DO…
Enzymes DO NOT…
Do:
-lower the activation energy of a reaction and make them reach transition state faster
-increases the rate of a spontaneous (exergonic reaction)
Do not:
-supply free energy to a reaction
-make an endergonic reaction proceed spontaneously
-alter products
-get consumed
What are the ways enzymes lower activation energy/bring reactants to transition state with enzymes?
- Bringing molecules together
-For reactions to occur, substrate molecules must collide with each other, when both bind to substrate its ideal for reaction to occur - Exposing reactants to a charged environment that promotes the reaction
-Active sites contain ionic groups that attract or repel some parts of the substrate - this helps position bonds in a favourable way - Changing shape of the substrate
-the active site can distort or strain the substrate to weaken bonds, this reduces amount of energy required to break the bonds
What is the rate of reaction dependent on?
Its proportional to the number of reactant molecules that can overcome the activation barrier to reach transition state
-when enzymes lower the activation barrier, it makes the reaction molecules overcome it more
What is controlled oxidation
Reactions that require small activation energies catalyzed by enzymes and smaller energy changes
-cellular respiration
Two types of redox reactions and explain what happens
Reduction (RIG)
-atom that gains electrons are “reduced”
Oxidation (OIL)
-atoms that lose electrons are “oxidized”