뒤로General Biology: Energy, Enzymes, Cellular Respiration, and Photosynthesis
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Kinetic energy is the energy associated with motion. Moving objects perform work by imparting motion to matter.
Only about 30–40% of the energy from a fuel molecule like glucose is captured in ATP or usable forms; the rest is lost as heat.
ATP consists of adenine, ribose sugar, and three phosphate groups. It is the key molecule for energy storage and transfer in cells.
A catabolic reaction releases energy by breaking down complex molecules into simpler ones, such as in cellular respiration.
An anabolic reaction requires energy to build large molecules from smaller ones, like in photosynthesis.
Enzymes catalyze reactions by lowering the activation energy barrier, allowing reactants to reach the transition state at moderate temperatures.
Competitive inhibitors block the active site, preventing substrate binding. Noncompetitive inhibitors bind elsewhere, changing enzyme shape and reducing activity.
An endergonic reaction absorbs free energy from the surroundings and is nonspontaneous, requiring energy input.
An exergonic reaction releases free energy to the surroundings and is spontaneous.
Feedback inhibition occurs when the end product of a metabolic pathway inhibits an earlier step to prevent overproduction, e.g., cholesterol synthesis regulation.
Cellular respiration: C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP. It is a catabolic reaction occurring in mitochondria.
Yes, plants perform cellular respiration. Without oxygen or sunlight, they ferment, producing ethanol.
Redox reactions transfer electrons between molecules; oxidation is loss of electrons, reduction is gain.
Glycolysis splits glucose into 2 pyruvate in the cytoplasm, producing a net of 2 ATP and 2 NADH.
The Krebs cycle oxidizes acetyl-CoA to CO2, producing 1 ATP, NADH, and FADH2 per turn; it runs twice per glucose.
ETC passes electrons from NADH and FADH2 through protein complexes, pumping H+ to create a gradient used by ATP synthase to make ~26-28 ATP; oxygen is final electron acceptor.
NAD and FAD transport electrons to the electron transport chain.
Oxygen acts as the final electron acceptor in the ETC, forming water.
In absence of oxygen, pyruvate is converted to lactic acid, regenerating NAD+ for glycolysis and producing 2 ATP.
Without oxygen, pyruvate converts to acetaldehyde and then ethanol, releasing CO2 and regenerating NAD+ for glycolysis.
Glycolysis (cytoplasm): glucose → 2 pyruvate + 2 ATP + 2 NADH. Krebs cycle (mitochondrial matrix): acetyl-CoA → CO2 + 2 ATP + NADH + FADH2. ETC (inner membrane): NADH/FADH2 donate electrons, H+ gradient drives ATP synthase, oxygen forms water.
6CO2 + 6H2O + light → C6H12O6 + 6O2. It is anabolic and occurs in chloroplasts.
Gases move through stomata, openings controlled by guard cells that regulate CO2 intake, O2 release, and water vapor loss.
Photosynthetic pigments like chlorophyll are in the thylakoid membranes of chloroplasts, organized in photosystems.
Light excites electrons, water is split, producing ATP, NADPH, and releasing oxygen.
Occurs in chloroplast stroma; uses ATP and NADPH to fix CO2 into glucose without direct light.
Electrons move through the thylakoid membrane photosystems, powering ATP and NADPH production for the Calvin cycle.
The Calvin cycle receives ATP and NADPH produced in light-dependent reactions.
Photosynthesis mainly uses red and blue light because chlorophyll absorbs these; leaves appear green because chlorophyll reflects green light.