Chapter 5 Summary
Key Takeaways
- Energy and Its Role in Living Organisms: Living organisms rely on chemical energy, stored in molecules like glucose and ATP, to fuel cellular processes. Glucose is a stable form of stored energy, while ATP is the immediate energy currency, releasing energy when converted to ADP. Energy exists in two main forms: kinetic energy (movement) and potential energy (stored energy). The conservation of energy principle states that energy can change forms but cannot be created or destroyed, as seen in energy transformations in both physical and biological systems.
- Metabolism and Enzymes in Biochemical Reactions: Metabolism encompasses all biochemical reactions in living organisms, including catabolic reactions (which break down molecules and release energy, e.g., cellular respiration) and anabolic reactions (which build molecules and absorb energy, e.g., protein synthesis). Enzymes are biological catalysts that speed up these reactions by lowering activation energy, ensuring life-sustaining processes occur efficiently.
- Photosynthesis and Cellular Respiration: Autotrophs (producers), such as plants, algae, and some bacteria, capture sunlight and store energy in glucose through photosynthesis. Heterotrophs (consumers), including animals and fungi, rely on autotrophs for food. Energy is transferred as glucose is broken down through cellular respiration to produce ATP, the energy currency of life. This cycle sustains all living organisms, recycling carbon and oxygen while maintaining the energy balance in ecosystems.
- Light-Dependent Reactions: Photosynthesis converts light energy into chemical energy through light-dependent reactions, which occur in the thylakoid membrane. Pigments like chlorophyll absorb sunlight, exciting electrons that move through the electron transport chain, driving the production of ATP and NADPH. These energy carriers fuel the Calvin cycle, where sugar molecules are synthesized. This process enables autotrophs to produce food, supporting life and energy flow in ecosystems.
- The Calvin Cycle: The Calvin cycle uses ATP and NADPH from light-dependent reactions to fix CO₂ into organic molecules, ultimately forming glucose. This process occurs in the stroma and involves three stages: carbon fixation, reduction, and regeneration. Photosynthesis and cellular respiration form a biological energy cycle, where photosynthesis stores solar energy in carbohydrates, and respiration releases this energy for cellular functions. This cycle sustains life by continuously transforming and recycling energy and matter in ecosystems.
OpenAI. (2025). ChatGPT. [Large language model]. https://chat.openai.com/chat
Prompt: Summarize the following content into six key takeaways.
Flashcards
Text Description
- Biochemical reactions: Chemical reactions occurring within living organisms
- Metabolism: All chemical reactions in an organism; includes catabolism and anabolism
- Catabolic reactions: Processes that break down molecules into simpler ones; releases energy
- Anabolic reactions: Processes that build complex molecules from simpler ones; requires energy
- Activation energy: Minimum energy required to start a chemical reaction
- Enzyme: Protein that catalyzes (speeds up) a biochemical reaction by lowering activation energy
- Substrate: Specific substance that an enzyme binds with
- Active site: Region on an enzyme where the substrate binds and the chemical reaction occurs
- Induced fit: Model describing how an enzyme changes shape to better fit the substrate upon binding
- Enzyme inhibitor: Molecule that binds to an enzyme and blocks its function
- Competitive inhibition: Inhibitor binds to the active site and blocks the substrate from binding
- Allosteric inhibition: Inhibitor binds to site on the enzyme that is not the active site (allosteric site); causes change to enzyme shape so prevents substrate from binding
- Kinetic energy: Energy of motion (e.g. moving objects, molecules in motion)
- Potential energy: Stored energy based on position or structure (e.g. water behind a dam, ATP)
- Conservation of energy: The principle stating that energy cannot be created or destroyed, only transformed from one form to another
- Chemical Energy: Potential energy stored in chemical bonds (e.g. glucose)
- ATP (Adenosine Triphosphate): Primary energy carrier in cells, supplying energy for cellular processes
- Photosynthesis: Process where producers convert sunlight into chemical energy stored as glucose
- Cellular Respiration: Process by which organisms convert chemical energy (glucose) into usable ATP energy
- Autotroph: Organism that can produce its own food; producers
- Heterotrophs: Organisms that get their food by consuming other organisms; consumers
- Mesophyll: Leaf tissue containing chloroplasts, specialized for photosynthesis
- Stomata: Small pores on leaves allowing gas exchange (CO₂ and O₂) and water vapour release
- Chloroplast: Organelle within plant cells where photosynthesis takes place
- Thylakoids: Stacked, disc-shaped structures in chloroplasts; site of the light-dependent reactions of photosynthesis
- Chlorophyll: Green pigment in chloroplasts that absorbs sunlight
- Wavelength: the distance between consecutive points of a wave
- Visible light: portion of the electromagnetic spectrum that is detectable by the human eye,
- Pigment: A substance that absorbs light and gives colour to plants, animals, and other materials; reflects the colour that they cannot absorb
- Photosystem: clusters of pigments and proteins that absorb sunlight; studded in the thylakoid membrane and used in the light-dependent reactions
- Photon: a distinct quantity or “packet” of light energy
- Light-dependent reactions: First stage of photosynthesis; Light energy is converted into chemical energy in the form of ATP and NADPH
- ATP synthase: An enzyme that produces ATP from ADP and inorganic phosphate
- Electron carrier: Molecule that shuttles high-energy electrons between compounds in biochemical pathways
- Calvin cycle: Second stage of photosynthesis; Uses the energy stored by the light-dependent reactions and carbon dioxide to form glucose
- Carbon fixation: process of converting inorganic carbon dioxide into organic compounds during photosynthesis; first stage of the Calvin Cycle
- Reduction: A chemical reaction that involves the gain of electrons by an atom or molecule; 3-PGA is reduced to G3P during the second stage of the Calvin cycle
- Regeneration of RuBP: Final phase in the Calvin cycle; G3P is used to regenerate RuBP, enabling the cycle to continue
- 2 main categories of energy: kinetic energy and potential energy
- Most ecosystems get energy from: Photosynthesis
- Equation for photosynthesis: 6CO2 + 6H2O → C6H12O6 + 6O2
- How are photosynthesis and cellular respiration related? The products of one process are the reactants of the other
- 2 categories based on how organisms get their food: autotrophs (producers) and heterotrophs (consumers)
- 2 stages of photosynthesis: light-dependent reactions and the Calvin cycle
- Location of light-dependent reactions: Thylakoid membrane of chloroplasts
- How does PSII replenish donated electrons? Splits a molecule of water to access the electrons
- Explain the path of electrons through the light-dependent reactions: Water > PSII > ETC > PSI > NADPH
- What happens to energy in electrons as they pass through the ETC? Energy from the electron is used to pump H+ into thylakoid, producing potential energy
- What is the purpose of the light-dependent reactions: Convert light energy into chemical energy (ATP and NADPH)
- 2 types of energy-carrier molecules produced in light-dependent reactions: ATP and NADPH
- Location of Calvin cycle: the stroma of chloroplasts
- Stages of the Calvin cycle: carbon fixation, reduction, regeneration of RuBP
OpenAI. (2025). ChatGPT. [Large language model]. https://chat.openai.com/chat
Prompt: Can you give me brief summaries of these key terms.
