APK CH 3 (must finish adding)

Metabolism

The sum of all chemical reactions occurring inside cells.

Catabolic Reactions

Breakdown of larger molecules into smaller molecules.

Examples: Breaking proteins down into amino acids, breaking glycogen down into glucose.

Generally release energy (exergonic).

Anabolic Reactions

1. Synthesis (building) of larger molecules from smaller molecules.

2. Examples: Synthesizing proteins from amino acids, making glycogen from glucose.

3. Require energy input (endergonic).

Metabolic Pathways + Sequence/components

Sequences of interconnected chemical reactions where the product of one reaction serves as the reactant for the next.

Hydrolysis

Breaking a chemical bond using water ("splitting with water").

Condensation

Joining two molecules together, forming a water molecule as a byproduct.

• Reverse of hydrolysis

Phosphorylation

Addition of a phosphate group (P) to a molecule.

• A condensation type reaction (produces water)

Dephosphorylation

Removal of a phosphate group from a molecule.

• Example: Removal of phosphate from ATP to form ADP.

• ATP Hydrolysis

Oxidation

The removal of electrons or hydrogen atoms from a molecule.

Mnemonic: LEO (Loss Electrons = Oxidation)

Reduction

The addition/acceptance of electrons or hydrogen atoms by a molecule.

• Mnemonic: GER (Gain Electrons = Reduction

Oxidation and reduction always occur together as paired

redox reactions

Hydrogen atoms act as reducing equivalents because

they carry an electron

Energy

The capacity to do work

Work is driven by

metabolic reactions

Kinetic Energy

Energy associated with motion

Potential Energy

Stored energy

First Law of Thermodynamics

Energy cannot be created or destroyed, only transformed from one form to another (e.g., potential energy in chemical bonds converted into kinetic energy).

Second Law of Thermodynamics

Processes proceed spontaneously from states of higher order/concentration to lower order/concentration (spreading out).

• Aka proceed in the direction that spreads energy, orange scent example

All chemical reactions involve

energy exchange

If a reaction releases energy, it's because

the reactant molecules had more energy than the products. 

Energy Change Formula

Exergonic Reactions

Reactants have higher energy than products (Delta E < 0).

Release energy; proceed spontaneously.

Endergonic Reactions

Products have higher energy than reactants (Delta E > 0).

Require energy input; do not proceed spontaneously.

Energy Coupling

Exergonic reactions (such as catabolism of glucose) are coupled to endergonic reactions (such as synthesis of ATP or driving ion pumps) to fuel cellular work. Uncoupled energy is released as heat.

Calorie

amount of energy/heat necessary to raise the temp of 1g of water 1 degree C

Equilibrium

reactant is converted to product at the same rate product is converted to reactant

Delta E = 0

Chemical Equilibrium Defined: Chemical equilibrium occurs when the forward reaction rate equals the reverse reaction rate, meaning the net concentrations of reactants and products remain constant, and the total energy of reactants equals the total energy of products.

Concentrations Do Not Need to Be Equal: Equilibrium does not mean that concentrations of reactants and products must be equal—only that their concentrations are no longer changing over time. Thus, the second option ("No, the concentration is different...") is incorrect.

Despite being at equilibrium, the CONCENTRATION of products and reactants will not necessarily be equal.  (only same rate of energy)

Which necessarily means that if the energy of a reactant molecule is pretty close to the energy of a product molecule, there will be less of a difference in concentration between reactants and products

if the energy difference is large between the reactants and products, then the concentration difference at equilibrium will also be large.

When we look at the energy per mole of the reactants and products, that will give us the positive or negative change of energy needed to determine if the reaction is endergonic or exergonic.

The Law of Mass Action

An increase in [reactants] relative to [products] tends to push a reaction forward

An increase in [products] relative to [reactants] tends to push a reaction reverse

Enzymes act as biological catalysts that lower the

activation energy required to initiate a reaction without being consumed themselves.

Substrates bind to the enzyme’s active site forming an enzyme-substrate complex, inducing a conformational change that facilitates bond cleavage or formation.

Enzymes do not

change the nature of the reaction or the final product.

only increase reaction rate.

Factors Influencing Enzyme-Catalyzed Reaction Rates

1. Substrate Concentration

2. Enzyme Concentration

3. Affinity

4. Temperature

5. pH

6. Cofactors & Coenzymes

Substrate Concentration

Increasing substrate concentration increases reaction rate up to a saturation point (where all active sites are occupied).

Enzyme Concentration

Increasing enzyme concentration increases the maximum reaction rate.

Affinity

Higher binding affinity between enzyme and substrate increases reaction rate at lower substrate concentrations.

Temperature

Increases rate up to an optimal temperature; extreme heat denatures the enzyme.

pH

Optimal activity occurs within a narrow pH range; deviations reduce rate due to denaturation. Increasing acidity = decreasing ph = lowered enzyme activity. 

Vitamin and mineral cofactors make

enzymes work. Without the cofactor, the reaction can’t take place.

Many enzymes require a cofactor, which functions to

lock the reacting substance into its active site.

Important Metabolic Coenzymes

FAD, NAD, CoA

3 Ways to Regulate enzyme activity

1. Allosteric regulation

2. Covalent Regulation

3. Feedback Inhibition (end product inhibition)

Allosteric Regulation

Covalent Regulation

Feedback Inhibition

Adenosine Triphosphate (ATP)

serves as the primary temporary energy storage molecule in cells

ATP Hydrolysis (Exergonic)

$\text{ATP} + \text{H}_2\text{O} \rightarrow \text{ADP} + \text{P}_i + \text{Energy}$

• Breaking the high-energy phosphate bond releases energy directly used to perform cellular work.

ATP Synthesis (Endergonic)

$\text{ADP} + \text{P}_i + \text{Energy} \rightarrow \text{ATP} + \text{H}_2\text{O}$

Uses energy derived from nutrient breakdown (catabolism of glucose, fats, proteins) to rephosphorylate ADP back to ATP.

Glycolysis

Location? Event Summary? Products? Byproducts?

Cytosol

10-step anaerobic breakdown of 1 glucose molecule into 2 pyruvate molecules.

• 2 Pyruvate • 2 net ATP (substrate-level) • 2 NADH

Linking step

Location? Event Summary? Products? Byproducts?