Cellular Respiration and Thermodynamics

• Energy the capacity to do work or to change matter.

Types of Energy

• Kinetic energy is the energy of motion.
• Mechanical energy involves moving matter like a car or your muscles.
• Electrical energy is the movement of charged particles, such as nerve impulses or electricity.
• Radiant energy is energy that moves in waves, like heat and microwaves.
• Potential energy is stored or inactive energy, exemplified by water behind a dam.
• Chemical energy is energy stored in chemical bonds; ATP is an example.

Thermodynamics

• Thermodynamics is the study of energy and its transformations.
• The first law of thermodynamics states that energy cannot be created or destroyed, only changed from one form to another.
• The second law of thermodynamics states that energy cannot be changed from one form to another without a loss of usable energy; in living systems, this energy is lost as heat.
• Entropy is the relative amount of disorder or disorganization.
• Each energy transformation increases entropy in the universe, and therefore, the entropy in the universe is continually increasing.

Metabolic Reactions

• Metabolic reactions are chemical reactions that involve energy transformations.
• Metabolic reactions are generally reversible.
• In the reaction A+B ⇌ AB, chemical equilibrium is where the concentrations of reactants (A and B) and product (AB) are constant.
• Reactants are the substances that participate in the reaction and what you begin the reaction with.
• Products are the substances produced by the reaction, or what the reaction ends with.
• Endergonic reactions require the input of energy.
• Exergonic reactions release energy.

ATP

• ATP, or adenosine triphosphate, releases energy when it releases one of its phosphate bonds.
• ATP provides whatever energy the cell needs, and is used for cellular processes.
• ATP breakdown is exergonic.
• When ATP releases energy, it can power endergonic reactions.
• ATP functions to store energy in the phosphate bonds.
• The energy in ATP is only released when a high-energy phosphate bond is broken.
• ATP energy is used for chemical work, transport work, and mechanical work.

Metabolic Pathways

• Biosynthetic pathways are metabolic pathways that build larger molecules from smaller molecules.
• Degradative pathways are metabolic pathways that break down molecules.
• In cells and multicellular organisms, each step in a metabolic pathway is catalyzed by an enzyme.

Enzymes

• Enzymes are proteins that act as biological catalysts.
• All enzymes are proteins and biological catalysts that speed up chemical reactions without causing a reaction that wouldn't occur naturally

Enzyme Characteristics

• Enzymes are specific for their substrate, which is the substance the enzyme acts upon.
• Enzymes help a chemical reaction to occur without becoming part of the product or being used up.
• Enzymes lower the energy of activation required for a chemical reaction to occur.
• A substrate is a substance that the enzyme acts upon.
• The active site is the place on the enzyme where the substrate binds.
• The enzyme-substrate complex is the combination of enzyme and substrate, where the substrate enters and binds to the active site on the enzyme.
• The lock and key model is a model with the enzyme and active site fitting exactly together.
• The induced fit model is a model is where the substrate moves into the active site of the enzyme, and the active site molds around the substrate.

Factors Affecting Enzyme Activity

• Substrate concentration: the more concentrated a substrate, the faster an enzyme will react, up to the saturation point of the enzyme.
• Temperature and pH: enzymes work better within certain temperature and pH ranges; high temperatures can denature the enzyme.
• Enzyme concentration: the more concentrated an enzyme, the faster the reaction will occur.
• Cells regulate enzyme concentration by regulating gene expression.
• Cofactors are "enzyme helpers"; these are molecules that are necessary for an enzyme to function and are either inorganic ions or organic molecules.
• Coenzymes: the term generally refers to organic cofactors.
• Enzyme inhibitors: these prevent the active enzyme from combining with its substrate.
• Competitive inhibitors: molecule that binds to the active site and prevents the substrate from binding.
• Non-competitive inhibitors: where a molecule binds to the enzyme and changes the shape of the active site, preventing the substrate from binding.
• Feedback inhibition: where the end product of a metabolic pathway binds to the enzyme and prevents it from binding with its substrate.
• During the enzyme cycle, the Enzyme + Substrate becomes an Enzyme substrate complex, which becomes Product + Enzyme, which makes the enzyme bind with another substrate

Metabolic and Oxidation-Reduction Reactions

• Oxidation is the loss of electrons from a molecule.
• Reduction is the the gain of electrons from a molecule.
• Oxidation-reduction reactions (redox reactions) occur when one molecule is oxidized and another molecule is reduced. These reactions occur during cellular respiration and photosynthesis.
• During photosynthesis, hydrogen ions (H+) often accompany electrons.
• Photosynthesis uses oxidation/reduction reactions to transfer electrons (and hydrogen ions) from water to carbon dioxide to make glucose.
• During cellular respiration glucose loses hydrogen ions (and electrons) and produces carbon dioxide and water and also make ATP.

Electron Transport Systems

• Electron Transport Systems also abbreviated as ETS are a series of membrane bound carriers that pass electrons from one carrier to another.
• ETSs are coupled with ATP synthase that will be used to produce ATP.
• ATP synthase complexes are enzymes and their carrier proteins that form a complex that is embedded in the membrane of mitochondria or chloroplasts.
• These complexes use the flow of hydrogen ions to generate ATP.
• Chemiosmosis : the term for the production of ATP using a hydrogen ion gradient across a membrane.

Questions cover glucose breakdown, electron transport systems, ATP synthase function, and chemiosmosis. Additional topics include redox reactions, chemical equilibrium, and the role of ATP. The quiz also explores metabolic pathways, potential energy, entropy, and energy transformation in thermodynamics.