Energy and Enzymes
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All of the chemical reactions that occur within an organism that are necessary for the maintenance of life
Breakdown complex molecules and release energy
Use energy to build complex molecules
The capacity to do work
Energy of motion
Kinetic energy associated with random movement of molecules
Energy stored in position
Potential energy available for release in a chemical reaction (i.e. the breakdown of food)
The study of the energy transformations that occur in a collection of matter
1st Law of Thermodynamics
- Energy can be transferred/transformed but not destroyed
- Principle of conservation of energy
2nd Law of Thermodynamics
- Every energy transformation or transfer increases the entropy of the universe
- Entropy= measure of disorder/randomness
Does the increasing complexity seen in biological systems contradict the 2nd law?
We take energy from the environment, but we also release it back.
How do living organisms create macromolecules, cells, and tissues?
They create order locally, but energy transformations generate waste heat that increases the entropy of the universe
Portion of a system's energy that can perform work
What state is the reaction if delta G (free energy) is negative?
- The reaction is spontaneous (energetically favorable)
- Loss of free energy, final state is more stable
- Exergonic Reaction (Energy is Exiting)
What kind of a reaction is a catabolic reaction
What state is the reaction if delta G (free energy is positive?
- The reaction requires energy input
- Endergonic reaction (Energy is ENtering)
What kind of a reaction is an anabolic reaction?
-State of maximum stability
-Lowest possible G value
- Any change will require energy therefore systems are never spontaneously move away from equilibrium (can do no work)
Are most chemical reactions in cells at equilibrium?
How is work done in a cell?
- Energy Coupling
- Use of exergonic rxns to drive endergonic rxns
- The exergonic gives off energy
- Transfer of electrons releases energy stored in organic molecules
- Oxidation-reduction reaction
Loss of electrons (LEO)
- Gain electrons (GER)
- Adding electrons REDUCES the amount of positive charge of an atom
Adenosine triphosphate (ATP)
Bonds between phosphate groups can be broken by hydrolysis
How is ATP broken up
- It is an exergonic reaction
- ATP+H2O -> ADP + PideltaG= -7.3 kcal/mol
- The products have less potential energy than reactants
Regeneration of ATP
- The reverse reaction must be endergonic
- ADP + Pi -> ATP + H2O
- DeltaG= 7.3 kcal/mol
What provides necessary energy for cellular respiration and light energy
- Proteins (mostly) which act as catalysts and speed up reactions
- Not consumed by the reactions
- Act by lowering the activation energy (Ea)
Reactant acted on by the enzyme
Is the reaction catalyzed by a particular enzyme very specific
- Region that actually binds the substrate
- Only specific substrate can fit in active
- Binding of substrate causes the enzyme to slighly change shape
- Brings chemical groups of active site into optimal position to catalyze reactions
What do starting molecules have to be in order for a reaction to occur
They have to be contorted into an unstable form for reactions to occur
The energy that reactants absorb from their surroundings to reach a state where bonds can change
How do enzymes catalyze reactions
By lowering activation energy so it takes less to go through the reaction
How do enzymes lower activation energy?
- Act as a docking station to bring reactants together in proper orientation
- Stretch reactants toward transition-state form, stressing and bending chemical bonds
- By providing a microenvironment more favorable to a particular reaction
- Participate directly in the chemical rxn
Steps on how substrates are converted using enzymes
- Substrates enter active site
- They are held by weak interactions
- Active site can lower activation energy and speed up a reaction
- They are converted to products and then the products are released
- Active site is available for two new substrate molecules
What helps enzymes within the cell
- Cofactors: inorganic ions (i.e. Fe, Zn, Mg)
- Coenzymes: organic molecules (i.e. Nad, B vitamins, CoQ, folic acid)
- Prosthetic groups: molecules tightly bound to the enzyme (i.e retinal, metal ions, vitamins)
What factors affect enzyme activity
What happens when you increase the temperature with enzymes?
- It is more likely that molecules will collide with each other
- The optimal temperature depends on the enzyme, if you get too hot then the proteins will denature (lose it's shape)
What is the optimal pH for enzymes found in humans?
- Depends on where the enzyme is located
- Stomach enzymes need to be slightly acidic
- Enzyme function is tightly regulated
- Regulatory binding is usually reversible
How might an amino acid change at a site distant from the active site of the enzyme substrate specificity?
By changing the shape of the protein
- molecule resembles substrate and binds to active site
- It is competing for the active site
- Regulatory molecule binds away from active site and causes change in shape
- Can either activate or inhibit activity
- It can turn on and off
What to toxins and poisons often act as in regards to enzymes?
- End product of a pathway can bind to an enzyme that acts earlier in the pathway and inhibit it
- Prevents cell from wasting energy to make excess product
Phosphorylation and dephosphorylation can function as an on-off switch
Protein kinasws are enzymes that catalyze phosphorylation of target proteins at specific sites, whereas protein phosphatases catayze removal of phosphate(s) from phosphorylated proteins
Adenosine monophosphate (AMP) activates the enzyme phosphfructokinase (PFK) by binding @ a site distinct from substrate binding site. This is an example of?
Which of the following metabolic processes can occur without a net influx of energy from some other process?
ADP + Pi -> ATP + H2
C6H12O6 -> 6 CO2+ 6 H2O
Amino acids -> protein
Glucose + fructose -> sucrose
C6H12O6 -> 6 CO2+ 6 H2O
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