Bio Exam 3 Flash Cards

 Chapter 6 – Energy, Enzymes & Metabolism  

Energy – The ability to do work.  

Kinetic energy – Energy of motion.  

Potential energy – Stored energy.  

Entropy – Measure of disorder.  

Free energy – Usable energy for work.  

Electron transport chain – Series of proteins that transfer electrons to make ATP.  

ATP – Main energy molecule in cells.  

Enzyme – Protein that speeds up chemical reactions.  

Ribozymes – RNA molecules that act as enzymes.  

Substrate – The molecule an enzyme acts on.  

Active site – Part of an enzyme where the substrate binds.  

Activation energy – Energy needed to start a reaction.  

Cofactors – Helpers (ions or molecules) for enzymes.  

Half-life – Time for half of a substance to break down.  

Autophagy – Process where cells break down their own parts for recycling.  

 6.1 Energy and Chemical Reactions  

First law of thermodynamics – Energy cannot be created or destroyed, only transferred.  

Second law of thermodynamics – Energy transfer increases disorder (entropy).  

Endergonic vs. Exergonic reactions – Endergonic reactions absorb energy, exergonic reactions release energy.  

Oxidation-reduction (redox) reactions – Transfer of electrons; oxidation loses electrons, reduction gains electrons.  

Free energy equation (H = G + TS) – H = total energy, G = free energy, T = temperature, S = entropy.  

 6.2 Enzymes and Ribozymes  

Enzyme properties – Reusable; forms enzyme-substrate complex to speed up reactions.  

How enzymes lower activation energy – By stabilizing the transition state and making reactions easier.  

What affects enzyme activity – Temperature, pH, and chemicals can change enzyme function.  

Noncompetitive vs. Competitive inhibition – Competitive inhibitors block the active site; noncompetitive inhibitors bind elsewhere to change enzyme shape.  

 6.3 Overview of Metabolism  

Catabolic vs. Anabolic pathways – Catabolic breaks molecules down, anabolic builds them up.  

How to make ATP – Substrate-level phosphorylation (direct transfer of phosphate) and chemiosmosis (using a proton gradient).  

 Chapter 8 – Photosynthesis  

Photosynthesis – Process where plants make food using light.  

Biosphere – All living things on Earth.  

Heterotroph – Organism that eats others for food.  

Autotroph – Organism that makes its own food.  

Photoautotroph – Uses light to make food (plants, algae).  

Pigments – Molecules that absorb light.  

Accessory pigments – Extra pigments that help absorb more light.  

Stomata – Openings on leaves for gas exchange.  

Chloroplasts – Organelles where photosynthesis happens.  

Thylakoids – Flattened sacs in chloroplasts where light reactions occur.  

Granum – Stack of thylakoids.  

Stroma – Fluid in chloroplast where the Calvin cycle happens.  

Photons – Light particles.  

Ground state – Low-energy state of electrons.  

Excited state – High-energy state of electrons after absorbing light.  

Photosystem – Protein-pigment complex that captures light.  

Rubisco – Enzyme that fixes CO₂ in the Calvin cycle.  

Photorespiration – Wasteful process where rubisco binds oxygen instead of CO₂.  

 8.1 Overview of Photosynthesis  

Groups that carry out photosynthesis – Plants, algae, cyanobacteria.  

Chemical equation of photosynthesis –  

6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂  

Reactants and products – Reactants: CO₂, H₂O, light. Products: Glucose, O₂.  

Two stages of photosynthesis – Light reactions (make ATP & NADPH) and Calvin cycle (makes sugar).  

 8.2 Reactions That Harness Light Energy  

Main photosynthetic pigment – Chlorophyll a.  

Where photosynthesis occurs – In the chloroplasts.  

Where the light reactions occur – In the thylakoid membranes.  

What is produced & byproducts – ATP, NADPH (used in Calvin cycle), O₂ (waste).  

Steps of light reactions & photosystems –  

1. Photosystem II – Absorbs light, splits water, releases O₂, excites electrons.  

2. Electron Transport Chain – Electrons move, making ATP.  

3. Photosystem I – Absorbs light, re-energizes electrons, makes NADPH.  

Noncyclic vs. Cyclic electron flow – Noncyclic makes ATP & NADPH; cyclic makes only ATP.  

 8.4 Synthesizing Carbohydrates via the Calvin Cycle  

Where carbon reactions occur – In the stroma.  

What is produced & byproducts – Glucose (product), ADP & NADP⁺ (recycled).  

Steps of carbon reactions –  

1. Carbon fixation – Rubisco fixes CO₂.  

2. Reduction – ATP & NADPH convert molecules into sugars.  

3. Regeneration – RuBP is reformed to continue the cycle.  

 8.5 Variations in Photosynthesis  

C3 vs. C4 plants – C3 uses regular photosynthesis; C4 plants store carbon in a different way to reduce water loss.  

CAM plants – Open stomata at night to save water in dry environments.