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Chapter 8 An Introduction to Metabolism - 9 Cellular Respiration and…
Chapter 8 An Introduction to Metabolism - 9 Cellular Respiration and Fermentation
CONCEPT 8.1 An organisms metabolism transforms matter and energy, subject to the laws of thermodynamics
Metabolism- Totality of an organism's chemical reactions.
Organization of the Chemistry of Life into Metabolic Pathways
Metabolic Pathway- Begins with a specific molecule, which is then altered in a series of defined steps, resulting in a certain product.
Catabolic Pathways- degradative process of breaking down complex molecules to simpler compounds.
Anabolic Pathways- consume energy to build complicated molecules from simpler ones; sometimes called biosynthetic pathways.
Bioenergetics- Study of how energy flows through living organisms.
Forms of Energy
Energy- The capacity to cause change.
Kinetic Energy- Can be associated with the relative motion of objects.
Thermal Energy- Kinetic energy associated with the random movement of atoms or molecules.
Heat- Thermal energy in transfer from one object to another.
Potential Energy- not kinetic energy, it is energy that matter possesses because of its location or structure.
Chemical Energy- Term used by biologists to refer to the potential energy available for release in a chemical reaction.
Laws of Energy Transformation
Thermodynamics- Study of the energy transformations that occur in a collection of matter.
First Law of thermodynamics or the principle of conservation of energy- Energy can be transferred and transformed, but it cannot be created or destroyed.
Entropy- As a measure of molecular disorder or randomness.
Second Law of Thermodynamics- Every energy transfer or transformation increases the entropy of the universe
Spontaneous Process- Given process, by itself, leads to an increase in entropy, that process can proceed without requiring an input of energy
CONCEPT 8.2 The free-energy change of a reaction tells us whether or not the reaction occurs spontaneously
Free Energy- the portion of a system's energy that can perform work when temperature and pressure are uniform throughout the system, as in a living cell.
Free Energy and Metabolism
Exergonic Reaction- Proceeds with a net release of free energy.
Endergonic Reaction- One that absorbs free energy from its surroundings.
CONCEPT 8.3 ATP powers cellular work by coupling exergonic reactions to endergonic reactions.
Energy Coupling- Key feature in the way cells manage their energy resources.
Phosphorylated Intermediate- The recipient molecule with the phosphate group covalently bonded.
CONCEPT 8.4 Enzymes speed up metabolic reactions by lowering energy barriers
Enzyme- is a macromole that acts as a catalyst.
Catalyst- Chemical agent that speeds up a reaction without being consumed by the reaction.
Activation Energy or Free Energy of Activation- Energy required to contort the reactant molecules so that the bond can break.
Substrate Specificity of Enzymes
Substrate- Reactant an enzyme acts on.
Enzyme-Substrate Complex- When the enzyme binds to its substrate (or substrates, when there are two or more reactants).
Activate Site- Only restricted region of the enzyme molecule actually binds to the substrate.
Induced Fit- The tightening of the binding after initial contact.
Cofactors- adjuncts, may be bound tightly to the enzyme as permanent residents, or they may bind loosley and reversibly along with the substrate.
Coenzyme- If the cofactor is an organic molecule.
Enzyme Inhibitors
Competitive Inhibitors- Reduce the productivity of enzymes by blocking substrates from entering active sites.
Noncompetitive Inhibitors- Do not directly compete with the substrate to bind to the enzyme at the active site.
CONCEPT 8.5 Regulation of enzyme activity helps control metabolism
Allosteric Regulation- The term used to describe any cause in which a protein's function at one site is affected by the binding of a regulatory molecule to a separate site.
Cooperativity- This mechanism amplifies the response of enzymes to substrate.
Feedback Inhibition- Which a metabolic pathway is halted by the inhibitory binding of its end product to an enzyme that acts early in the pathway.
CONCEPT 9.1 Catabolic pathways yeild energy by oxidizing organic fuels
Catabolic Pathways and Production of ATP
Fermentation- A partial degradation of sugars or other organic fuel that occurs without the use of oxygen.
Aeorbic Respiration- Which oxygen is consumed as a reactant along with the organic fuel.
Cellular Respiration- Includes both anaerobic and aerobic process, but it originated as a synonym for aerobic respiration because of the relationship of that process to organismal respiration, in which and animal breathes in oxygen.
The Principle of Redox
Redox Reactions- Electron transfers are called oxidation-reduction reactions.
Oxidation- The loss of electrons from one substance.
Reduction- The addition of electrons to another substance.
Reducing Agent- The electron donor, reduces "Y", which accepts the donated electron.
Oxidizing Agent- Substances "Y", the electron acceptor, it oxidizes X
e
by removing its electron.
Electron Transport Chain- consists of a number of molecules, mostly proteins, built into the inner membrane of the mitochondria of eukaryotic cells.
The Stages of Cellular Respiration: A Preview
Glycolysis- Which occurs in the cytosol, begins the degradation process by breaking glucose into two molecules of a compound called pryuvate.
Citric Acid Cycle- The breakdown of glucose to carbon dioxide is completed.
Oxidative Phosphorylation- It is powered by the redox reactions of the electron transport chain.
Substrate-level Phosphorylation- Smaller amount of ATP is formed directly in a few reactions of glycolysis and the citric acid cycle by a mechanism.
CONCEPT 9.3 After pryuvate is oxidized, the citric acid cycle completes the energy-yielding oxidation of organic molecules
Acetyl CoA- Linking glycolysis and the citric acid cycle.
CONCEPT 9.4 During oxidative phosphorylation, chemiosmosis couples electron transport to ATP synthesis
Cytochromes- Most of the remaining electron carriers between ubiquinone and oxygen are proteins.
Chemiosmosis: The energy-Coupling Mechanism
ATP Synthase- Enzyme that makes ATP from ADP and inorganic phosphate.
Chemiosmosis- Process in which energy stored in the form of a hydrogen ion gradient across a membrane is used to drive cellular work as the synthesis of ATP.
Proton-Motive Force- Emphasizing the capacity of the gradient to perform work.
CONCEPT 9.5 Fermentation and anaerobic respiration enable cells to produce ATP without the use of oxygen
Types of Fermentation
Alcohol Fermentation- Pryuvate is converted to ethanol.
Lactic Acid Fermentation- Pyruvate is reduced directly by NADH to form lactate as an end product, regenerating NAD with no release of CO2 .
Comparing Fermentation with Anaerobic and Aerobic Respiration
Obligate Anaerobics- Carry out only fermentation or anaerobic respiration.
Facultative Anaerobes- Some organisms, like yeast and many bacteria, can make enough ATP to survive using either fermentation or respiration.
CONCEPT 9.6 Glycolysis and the citric acid cycle connect to many other metabolic pathways.
The versatility of Catabolism
Beta Oxidation- breaks the fatty acids down to two-carbon fragments, which enter the citric acid cycle as acetyl CoA.