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Questions and Answers
What term describes pathways that use energy to construct complex molecules from simpler ones?
Which group of organisms primarily uses inorganic carbon dioxide as their carbon source?
What term is used for reactions that occur spontaneously and release energy?
Which electron carrier is specifically involved in both anabolic reactions and photosynthesis?
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What type of organism is classified as a chemoheterotroph?
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In metabolism, what is the main characteristic of oxidation reactions?
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Which of the following best describes ATP?
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Which type of electron carrier is NADH categorized as?
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What process releases energy in ATP?
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How do enzymes facilitate chemical reactions?
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What happens to enzymes under high temperatures?
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What best describes the role of cofactors and coenzymes?
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What characterizes competitive inhibitors?
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What is the effect of noncompetitive (allosteric) inhibitors?
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When does enzyme activity increase with substrate concentration?
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What term describes enzymes that are inactive without their necessary helpers?
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Study Notes
Metabolism Overview
- Metabolism encompasses all chemical reactions within a cell.
- Metabolic pathways consist of a series of interconnected reactions for molecule synthesis or breakdown.
- Exergonic reactions occur spontaneously and release energy, while endergonic reactions require energy to proceed.
Types of Metabolic Processes
- Anabolism refers to pathways that utilize energy to synthesize complex molecules from simpler ones.
- Catabolism involves pathways that decompose complex molecules into simpler ones, releasing stored energy.
- Energy derived from catabolic processes fuels anabolic metabolism, necessitating a constant balance between the two.
Organism Classification
- Classification is based on carbon and energy sources.
Carbon Source
- Autotrophs: Utilize inorganic CO2 to create organic carbon compounds; examples include plants and cyanobacteria.
- Heterotrophs: Depend on complex organic compounds for nutrients; examples include humans and E. coli.
Energy Source
- Phototrophs: Obtain energy from light.
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Chemotrophs: Acquire energy by breaking chemical bonds, with two subtypes:
- Organotrophs: Use organic compounds for energy (e.g., humans, fungi).
- Lithotrophs: Use inorganic compounds for energy (e.g., hydrogen sulfide, reduced iron), predominant in microbes.
Combined Classification
- Most organisms are classified as chemoheterotrophs, utilizing organic molecules for both energy and carbon sources.
Redox Reactions in Metabolism
- Electron transfer mechanisms are crucial for energy storage and utilization within cells.
- Small electron transfers protect cellular integrity from damage.
- Oxidation reactions remove electrons (oxidized state), while reduction reactions add electrons (reduced state).
- Redox reactions are interdependent, with oxidation and reduction occurring simultaneously.
Energy Carriers: NAD+, NADP+, FAD, and ATP
- Nutrient breakdown energy is stored within electron carriers and ATP.
- Main electron carriers include:
- NAD+/NADH: Functions in various metabolic reactions.
- NADP+/NADPH: Involved in anabolic processes and photosynthesis.
- FAD/FADH2: Engaged in sugar breakdown.
- Electron carriers provide reducing power by donating electrons.
ATP (Adenosine Triphosphate)
- ATP acts as the cell's primary energy currency, storing energy for future use.
- AMP serves as the foundational unit for ATP construction; two phosphates for ADP and three for ATP.
- Energy is released from ATP when phosphate bonds are broken, powering cellular processes.
- Energy requirement for adding phosphates (phosphorylation) contrasts with energy release upon their removal.
Enzymes and Catalysis
- Catalysts accelerate chemical reactions and are reusable; enzymes are biochemical catalysts controlling metabolism.
- Activation energy is the necessary energy to initiate reactions, which enzymes lower by binding substrates at their active sites.
- Enzymes exhibit specificity, fitting substrates uniquely, akin to a "jigsaw puzzle."
- Induced fit involves minor shape changes in the enzyme to optimize substrate binding.
Environmental Effects on Enzyme Activity
- Enzyme activity is influenced by temperature, pH, and substrate concentration; extreme conditions can denature enzymes.
- Increased substrate concentrations enhance enzyme activity until saturation occurs.
Cofactors and Coenzymes
- Cofactors (inorganic) and coenzymes (organic) assist enzyme functionality.
- Inactive enzymes without helpers are apoenzymes; active forms containing helpers are holoenzymes.
Enzyme Regulation
- Enzyme activity can be modulated positively or negatively.
Competitive Inhibitors
- Compete with substrates for the active site, blocking substrate access.
- Effective at equal concentrations to substrates; used in medications like sulfa drugs.
Noncompetitive (Allosteric) Inhibitors
- Attach to a site distinct from the active site, altering enzyme shape and reducing substrate affinity.
- Lower concentrations of inhibitors are required for effect compared to substrates.
Allosteric Activators
- Increase substrate binding ability by binding to sites other than the active site.
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Description
Test your understanding of metabolism and metabolic pathways with this engaging quiz. Covering concepts like exergonic and endergonic reactions, as well as anabolism and catabolism, this quiz will help reinforce your knowledge of how cells metabolize energy and molecules.
