Here are the answers to your biology questions:
1. Definitions:
* Metabolism: The sum total of all chemical reactions that occur within a living organism.
* Catabolism: The breakdown of complex molecules into simpler ones, releasing energy.
* Anabolism: The synthesis of complex molecules from simpler ones, requiring energy input.
* Endergonic Reaction: A reaction that requires an input of energy to proceed.
* Exergonic Reaction: A reaction that releases energy.
2. Role of Enzymes in Metabolism:
Enzymes are biological catalysts that speed up chemical reactions by lowering the activation energy. They bind to specific substrates, forming an enzyme-substrate complex, and catalyze the reaction. This allows metabolic processes to occur at rates compatible with life.
3. Enzyme Activity:
* Activation Energy: The minimum amount of energy required for a reaction to occur.
* Catalyst: A substance that speeds up a chemical reaction without being consumed in the process.
* Active Site: The specific region on an enzyme where the substrate binds.
* Denaturation: The loss of an enzyme's shape and function, often due to extreme temperature or pH.
* Substrate: The molecule upon which an enzyme acts.
* Enzyme-Substrate Complex: A temporary complex formed when an enzyme binds to its substrate.
* Suffix -ase: Commonly used to denote enzymes, such as sucrase, protease, and lipase.
4. Oxidation-Reduction Reactions in Cellular Respiration:
In cellular respiration, oxidation-reduction reactions involve the transfer of electrons and hydrogen ions. Oxidation is the loss of electrons (and often hydrogen atoms), while reduction is the gain of electrons (and often hydrogen atoms). Energy is released during these reactions and is used to produce ATP.
5. Balanced Equation for Cellular Respiration:
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy (ATP)
6. Structure of a Mitochondrion:
* Outer Membrane: Encloses the mitochondrion.
* Inner Membrane: Folded into cristae, increasing surface area for ATP production.
* Intermembrane Space: The space between the outer and inner membranes.
* Matrix: The fluid-filled space inside the inner membrane, containing enzymes for the citric acid cycle.
7. Glycolysis:
Glycolysis is the breakdown of glucose into pyruvate. It occurs in the cytoplasm and produces 2 ATP, 2 NADH, and 2 pyruvate molecules.
8. Citric Acid Cycle:
The citric acid cycle, also known as the Krebs cycle, occurs in the mitochondrial matrix. It completely oxidizes pyruvate, producing 2 ATP, 6 NADH, and 2 FADH₂ molecules per glucose molecule.
9. Electron Transport Chain and Oxidative Phosphorylation:
The electron transport chain is a series of protein complexes embedded in the inner mitochondrial membrane. Electrons from NADH and FADH₂ are transferred through the chain, releasing energy that is used to pump protons into the intermembrane space. The resulting proton gradient drives ATP synthesis through ATP synthase.
10. ATP and NADH Production:
* Glycolysis: 2 ATP, 2 NADH
* Citric Acid Cycle: 2 ATP, 6 NADH, 2 FADH₂
* Electron Transport Chain: ~32 ATP (from NADH and FADH₂)
11. Structure and Function of a Dicot Leaf:
Dicot leaves are typically broad and flat, with a network of veins. They have a waxy cuticle to prevent water loss, stomata for gas exchange, and mesophyll cells containing chloroplasts for photosynthesis.
12. Structure of a Chloroplast:
* Thylakoid: A flattened, disc-shaped sac.
* Thylakoid Membrane: The membrane surrounding the thylakoid.
* Thylakoid Space: The interior of the thylakoid.
* Stroma: The fluid-filled space outside the thylakoids.
* Grana: Stacks of thylakoids.
13. Site of Light-Dependent and Light-Independent Reactions:
* Light-Dependent Reactions: Thylakoid membrane
* Light-Independent Reactions (Calvin Cycle): Stroma
14. Balanced Equation for Photosynthesis:
6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂
* Carbon (C) from CO₂ is incorporated into glucose.
* Hydrogen (H) from water (H₂O) is incorporated into glucose.
* Oxygen (O) from water is released as O₂.
15. Dual Nature of Light:
Light exhibits both wave-like and particle-like properties. As a wave, it has a wavelength and frequency. As a particle, it consists of photons, discrete packets of energy.
16. Light Reactions:
Light energy is absorbed by pigments in photosystems I and II, exciting electrons. These electrons are transferred through a series of electron carriers, generating ATP and NADPH. Water is split, releasing oxygen as a byproduct.
17. Calvin Cycle:
The Calvin cycle uses ATP and NADPH from the light reactions to fix CO₂ from the atmosphere. CO₂ is incorporated into RuBP, forming 3-PGA. 3-PGA is reduced to G3P, which can be used to synthesize glucose or regenerate RuBP.
18. Role of Photosynthetic Pigments:
Photosynthetic pigments, such as chlorophyll a, chlorophyll b, and carotenoids, absorb light energy and transfer it to the reaction center of photosystems.
19. Role of Photosystems:
Photosystems I and II are protein complexes containing pigments and electron carriers. They absorb light energy and use it to excite electrons, initiating the electron transport chain.
20. Phases of the Calvin Cycle:
* Carbon Fixation: CO₂ is fixed to RuBP, forming 3-PGA.
* Reduction: 3-PGA is reduced to G3P using ATP and NADPH.
* Regeneration of RuBP: G3P is used to regenerate RuBP, allowing the cycle to continue.
21. ATP, NADPH, and CO₂ Requirements:
* To produce 1 G3P molecule: 9 ATP, 6 NADPH, and 3 CO₂
* To produce 1 glucose molecule: 18 ATP, 12 NADPH, and 6 CO₂
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