An Introduction to Energy, Enzymes, and Metabolism

Energy

The capacity to do work, Can be used and converted from one form to another

Potential Energy

Stored energy that is usually associated with location

Kinetic Energy

Active energy that is usually associated with movement

Chemical Potential Energy

Energy present in organic molecules within the bonds between atoms which can be released during chemical reactions

First Law of Thermodynamics

The law of conservation of energy, States that energy cannot be created or destroyed, but only transformed from one form to another, The total quantity of energy in the universe is constant

Second Law of Thermodynamics

The entropy (disorder) of the universe is continuously decreasing, States that energy transformations proceed spontaneously to convert matter from a more ordered/less stable form to a less ordered/more stable form (Energy from within the less ordered form is unstable)

Gibb’s Free Energy Equation

Total energy of a system = usable energy + unusable energy or deltaG = deltaH - TdeltaS

Enthalpy (H)

The total energy of Gibb’s Free Energy

Entropy (S)

The unusable energy (disorder usually in the form of heat) found in Gibb’s Free Energy

Gibb’s Free Energy (G)

Usable energy of Gibb’s Free Energy

deltaG > 0

Reaction occurs spontaneously, exergonic

deltaG < 0

Reaction is not spontaneous, endergonic

Adenosine Triphosphate (ATP)

Energy currency of cells, Consists of adenosine and three phosphate groups

Coupled Reactions

Reactions that occur in the same place at the same time

Exergonic

An energy-releasing reaction

Endergonic

An energy-requiring reaction

1. ATP is used to energize a reactant

2. ATP is used to change the shape of a reactant

Two main ways for a cell to couple ATP hydrolysis into an endergonic reaction

Transferring the phosphate group to the reactant

The cell’s way of achieving both methods of coupling ATP hydrolysis at once

[Substrate], Velocity, Vmax, Km/Michaelis Constant

Important values in determining enzymatic reaction rates (4)

[Substrate]

Value in enzymatic reaction rates that identifies the concentration of a substrate (mol/L)

Velocity

Value in enzymatic reaction rates that identifies the speed at which the reaction occurs (product/second)

Vmax

Value in enzymatic reaction rates that identifies the maximum velocity the exymatic reaction can achieve (limited by how quickly the enzyme can work)

Km/Michaelis Constant

Value in enzymatic reaction rates that identifies the concentration of a substrate at half Vmax (Vmax/2), Refers to the enzyme’s affinity for its substrate

Competitive Inhibitors

Bind to the active site and “compete” with the substrate

Vmax stays the same

Km increases

Observations of Vmax and Km when competitive inhibitors are introduced

Noncompetitive Inhibitors

Bind to the allosteric site, “shut off” enzymatic activity

Vmax increases

Km stays the same

Observations of Vmax and Km when noncompetitive inhibitors are introduced

Metabolism

The sum total of all chemical reactions that occur within a single organism. via the synthesis and breakdown of molecules

Metabolic Pathway

Series of linked metabolic reactions

Catabolism

Breakdown of molecules

Anabolism

Synthesis of molecules

Recycling organic molecules to be used in other reactions

To obtain energy for other reactions

Uses for catabolic reactions (2)

Gene Regulation

Genes that encode for certain enzymes are turned on or off, dependent on the needs of the cell (i.e. If no sugar is present, the production for the enzyme that breaks down sugar is turned off)

Cellular Regulation

Metabolism is altered depending on cell signals from environmental sources that will trigger a response of a catabolic or anabolic pathway (i.e. Hormones will send signals to the cell to undergo various metabolic changes)

Biochemical Regulation

The activity of certain enzymes can be regulated by inhibitors (or activators) as products of reactions are formed (i.e. Feedback Inhibition: The end product of a metabolic pathway inhibits the enzyme from an earlier step within the pathway)

Proteasome

Small protein complexes that break down proteins to be recycled to be used in the synthesis of other polymers

Proteases

Enzymes within the proteasome that degrate any proteins by cleaving peptide bonds

Autophagy

The process of digesting intracellular materials suh as organelles via lysosomes