Metabolism and Bioenergetics

Free Energy

The amount of energy available to do work after a chemical reaction has occurred, all living systems require a constant input of this

Things that require energy

Growth, reproduction, maintaining organization/homeostasis

Energy

The ability to do work

Metabolism

The sum of all chemical reactions that occur in a cell

Catabolic Pathways

Break down complex molecules into simpler ones, release energy as ATP (exergonic)

Anabolic Pathways

Build complex molecules from simpler ones, require energy like ATP and NADPH (endergonic),

Reactants

Substances that participate in a reaction

Products

Substances that form as a result of a reaction

Exergonic Reaction (ΔG<0)

Chemical reaction that releases energy, reaction is spontaneous, often used to drive other reactions

Endergonic Reaction (ΔG>0)

Chemical reaction that requires an input of energy to occur, reaction is not spontaneous

Metabolic Pathway

A series of linked enzyme-controlled reactions, each step converts a substrate in a product, the products of one reaction become the substrates for the next

Kinetic Energy

The energy of motion, released when chemical bonds are broken

Potential Energy

Stored energy, not being used at the moment, stored by chemical bonds

Glucose, fats, other organic molecules

Cells harvest energy from…

Chemical Energy

Form of potential energy associated with the interaction of atoms in a molecule

Mechanical Energy

Form of kinetic energy associated with the position, or motion of an organism

Chemical energy is converted into mechanical energy

What energy conversion occurs when organisms move?

Heat

Type of kinetic energy associated with random motion of molecules, released by plants from solar energy

1st Law of Thermodynamics

Energy cannot be created or destroyed, only transferred or transformed (converted)

2nd Law of Thermodynamics

Every energy transfer increases entropy, transferring it causes some to be lost as heat

Entropy

Measure of disorder or randomness in a system

Higher Entropy

Systems naturally move toward…

Low Entropy, require constant energy input

Living Systems

ΔG (Delta G)

Change in free energy, energy available to do work, tells us whether a reaction will happen

Purpose of Gibbs Free Energy

Used to predict whether a reaction will occur given certain circumstances

ΔG=ΔH-TΔS

Free Energy Formula (concept only)

ΔH

Change in enthalpy

Enthalpy

Heat

T

Temperature

ΔS

Change in entropy

ATP (adenosine triphosphate)

Nucleotide with 3 phosphate groups, “high energy” because phosphate group can be easily removed

ADP (adenosine diphosphate)

Nucleotide with 2 phosphate groups, can accept another phosphate group and become ATP

Mole

The molecular weight of a molecule in grams

Coupled Reactions

Reactions that occur simultaneously (ex. exergonic reaction releases energy and endergonic reaction requires an input of energy

System at Equilibrium (ΔG=0)

No net change in energy

Activation Energy (Ea)

The energy required to start a reaction, needed to reach the transition state, determines the rate of a reaction

Enzyme

A (usually) protein molecule that functions to speed up reactions by lowering activation energy

Substrate

Reactant in an enzyme-controlled reaction

Ribozyme

RNA molecule that functions as an enzyme that can catalyze chemical reactions, involved in synthesis of RNA and proteins at ribosomes

Induced Fit Model

Enzyme changes shape of active site when substrate binds to active site, this improves fit at the transition state and increases reaction rate

Active Site

Region of an enzyme where the substrate binds + chemical reaction occurs

Enzyme Specificity

Each enzyme binds specific substrate(s), shape and R-group interactions matter

Denature

Loss of an enzyme’s normal shape so that it no longer functions, sometimes reversible

Less than optimal pH or temperature, extreme conditions

Causes of denature

Substrate concentration, presence of inhibitors or activators

Factors Affecting Enzyme Activity

Cofactors

Non-protein assistant required by an enzyme in order to function (can be a metal ion [inorganic] or coenzyme [organic])

Coenzyme

Non-protein organic molecule that aids the action of the enzyme to which it is loosely bound

Vitamin

Organic nutrient that is required in small amounts for metabolic functions, often part of coenzymes

Enzyme Inhibition

Cell’s way of regulating enzyme activity, may be competitive or noncompetitive

Noncompetitive Inhibition

Form of enzyme inhibition where the inhibitor binds to an enzyme at a location that is not the active site

Allosteric Site

Site on an enzyme that binds to an effector molecule, allosteric activator can bind to this to promote enzyme activity

Competitive Inhibition

Form of enzyme inhibition where the substrate and inhibitor are both able to bind to the enzymes active site, product will only form when the substrate is at the active site

usually

Enzyme inhibition is… reversible

Feedback Inhibition

The end of a product inhibits an earlier enzyme, this prevents overproduction and maintains efficiency

Photosynthesis

Anabolic process, usually in chloroplast, that uses solar energy to reduce carbon dioxide to carbohydrate

Oxidation

Loss of one or more electrons from an atom or molecule

Reduction

Gain of electrons by an atom or molecule

Redox Reaction

A paired set of chemical reactions where one molecule gives up electrons (oxidized), while another accepts electrons (reduced) (also called an oxidation-reduction reaction)

NADPH+

Coenzyme in redox reactions that accepts electrons and hydrogen ions, helps reduce carbon dioxide to carbohydrate during photosynthesis

Cellular Respiration

Catabolic process, metabolic reactions that use the energy from carbohydrate, fatty acid, or amino acid breakdown to produce ATP molecules

NAD+

Coenzyme in redox reactions that accepts electrons and hydrogen ions to become NADH, which carries electrons during cellular respiration

Electron Transport Chain (ETC)

Process in a cell that involves the passage of electrons along a series of membrane-bound electron carrier molecules from high to low energy level, energy released is used for synthesis of ATP

ATP synthase

Enzyme that produces ATP from the diffusion of hydrogen ions across a membrane

Chemiosmosis

Process where mitochondria and chloroplasts use the energy off an electron transport chain to create a hydrogen ion gradient that drives ATP formation

Amylase

Digestive enzyme that breaks starch into sugars

Pepsin

Digestive enzyme that breaks proteins into peptides

Trypsin

Digestive enzyme that continues protein digestion in the small intestine

Lipase

Digestive enzyme that breaks fats into fatty acids and glycerol

Catalase

Enzyme that breaks hydrogen peroxide into water and oxygen

RuBisCO

Enzyme that fixes carbon dioxide in the Calvin Cycle

ATP synthase (chloroplast)

Enzyme that makes ATP in light reactions

DNA Polymerase

Enzyme that builds new DNA strands

RNA polymerase

Enzyme that makes RNA from DNA

Helicase

Enzyme that unwinds DNA

Ligase

Enzyme that joins DNA fragments

Restriction enzymes

Enzyme that cuts DNA at specific sequences

Carbonic anhydrase

Enzyme that helps regulate blood pH

Acetylcholinesterase

Enzyme that breaks down neurotransmitters at synapses

Protease

Protein digesting enzymes

Cellulase

Breaks down cellulose in plant cell walls