-
All of the chemical reactions that occur within an organism that are necessary for the maintenance of life
Metabolism
-
Catabolic reactions
Breakdown complex molecules and release energy
-
Anabolic reactions
Use energy to build complex molecules
-
The capacity to do work
Energy
-
Energy of motion
Kinetic Energy
-
Kinetic energy associated with random movement of molecules
Heat
-
Energy stored in position
Potential energy
-
Potential energy available for release in a chemical reaction (i.e. the breakdown of food)
Chemical Energy
-
The study of the energy transformations that occur in a collection of matter
Thermodynamics
-
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
Free energy
-
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
Exergonic
-
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?
Endergonic
-
-State of maximum stability
-Lowest possible G value
- Equilibrium
- 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?
No
-
How is work done in a cell?
- Energy Coupling
- Use of exergonic rxns to drive endergonic rxns
- The exergonic gives off energy
-
Redox Reactions
- Transfer of electrons releases energy stored in organic molecules
- Oxidation-reduction reaction
-
Oxidation
Loss of electrons (LEO)
-
Reduction
- 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 + Pi
- deltaG= -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
Exergonic reactions
-
Enzymes
- Proteins (mostly) which act as catalysts and speed up reactions
- Not consumed by the reactions
- Act by lowering the activation energy (Ea)
-
Substrate
Reactant acted on by the enzyme
-
Is the reaction catalyzed by a particular enzyme very specific
Yes
-
Active site
- Region that actually binds the substrate
- Only specific substrate can fit in active
-
Induced Fit
- 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
-
Activation energy
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 regulation
- 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
-
Competitive Inhibition
- molecule resembles substrate and binds to active site
- It is competing for the active site
-
Allosteric regulation
- 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?
Enzyme inhibitors
-
Feedback inhibition
- 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?
Allosteric activation
-
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
|
|