Bio Unit 2: CH: 6,7,8,9,10
CHAPTER 6 — A TOUR OF THE CELL
Cell The fundamental unit of life and the simplest collection of matter that can be alive.
Cell theory All organisms are made of cells; the cell is the basic unit of life; cells come from preexisting cells.
Why can't cell components work alone? Cellular structures depend on one another and work together to keep the cell alive.
Prokaryotic cell A cell without a membrane-bound nucleus; includes Bacteria and Archaea.
Eukaryotic cell A cell with a membrane-bound nucleus; includes protists, fungi, plants, and animals.
Bacteria Prokaryotic organisms without a membrane-bound nucleus.
Archaea Prokaryotic organisms distinct from bacteria and lacking a membrane-bound nucleus.
Eukaryotes include what groups? Protists, fungi, plants, and animals.
Prokaryotes include what groups? Bacteria and Archaea.
Nucleoid The region of a prokaryotic cell where its DNA is located.
Cytoplasm The region between the plasma membrane and the nucleus in eukaryotic cells.
Cytosol The semifluid portion of the cytoplasm in which organelles are suspended.
Plasma membrane A selective barrier surrounding the cell that controls movement of substances.
Ribosome A cellular structure that makes proteins.
Organelle A membrane-bound or specialized structure that performs a specific cellular function.
Why are eukaryotic cells generally larger? They contain membrane-bound organelles that compartmentalize cellular functions.
Microscopy The use of microscopes to visualize structures too small to see with the unaided eye.
Magnification How much larger an image appears compared with the actual object.
Resolution The ability to distinguish two objects as separate.
Contrast The difference in brightness or color that makes structures distinguishable.
Light microscope (LM) Uses visible light and glass lenses to magnify specimens.
What is a limitation of a light microscope? Its resolution is too low to clearly study many small eukaryotic organelles.
SEM Scanning electron microscope that focuses electrons on a specimen's surface and produces a 3-D-looking image.
TEM Transmission electron microscope that passes electrons through a specimen to study internal structures.
Cryo-EM Electron microscopy using very low temperatures to preserve and visualize biological structures.
SEM vs. TEM SEM shows surface features; TEM is mainly used to examine internal structures.
Why is surface area-to-volume ratio important? It limits cell size because volume increases faster than surface area as a cell grows.
What happens to SA:V as a cell gets larger? The surface-area-to-volume ratio decreases.
Why can't cells become indefinitely large? A lower SA:V makes exchange of nutrients, gases, and wastes less efficient.
Basic features shared by all cells Plasma membrane, cytosol, DNA/chromosomes, and ribosomes.
What does the plasma membrane do? Acts as a selective barrier controlling movement into and out of the cell.
What does a ribosome do? Uses genetic information to build proteins.
What does DNA do? Stores genetic information needed for cellular structure and function.
Eukaryotic cell compartmentalization Membrane-bound organelles separate incompatible processes and organize cellular activities.
Biochemistry Study of the chemical processes occurring in living organisms.
Cytology The study of cells and their structures.
Why is compartmentalization useful? It allows different cellular processes to occur under specialized conditions.
Biological membrane A double layer of phospholipids and other lipids containing proteins and carbohydrates.
Phospholipid bilayer The basic structure of a cell membrane made of two layers of phospholipids.
Hydrophilic Water-attracting; the phosphate heads of phospholipids are hydrophilic.
Hydrophobic Water-repelling; the fatty acid tails of phospholipids are hydrophobic.
Membrane proteins Proteins embedded in or associated with the membrane that perform various functions.
Membrane carbohydrates Carbohydrate chains attached to lipids or proteins that project from the cell surface.
Fluid mosaic model Model describing the membrane as a fluid phospholipid bilayer with proteins embedded within it.
Nucleus The organelle that houses most of the cell's DNA.
Nuclear envelope A double membrane surrounding the nucleus.
Nuclear pore A protein-lined opening that regulates movement between the nucleus and cytoplasm.
Nuclear pore complex Protein structure that controls movement of molecules through nuclear pores.
Nuclear lamina A protein fiber layer lining the inside of the nuclear envelope that helps maintain nuclear shape.
Nucleolus The region of the nucleus where ribosomal RNA is synthesized and ribosome components begin assembling.
Chromatin DNA associated with proteins in the nucleus.
Chromosome A structure consisting of DNA and associated proteins; condensed chromatin during cell division.
Ribosome structure Ribosomes are made of ribosomal RNA and proteins.
Free ribosome A ribosome suspended in the cytosol that generally makes proteins used inside the cell.
Bound ribosome A ribosome attached to the rough ER or nuclear envelope that generally makes proteins for membranes or secretion.
Endomembrane system A group of membranes and organelles involved in protein/lipid synthesis, modification, and transport.
Endomembrane system components Nuclear envelope, ER, Golgi apparatus, lysosomes, vesicles, vacuoles, and plasma membrane.
Endoplasmic reticulum (ER) A membrane network continuous with the nuclear envelope that makes and processes cellular products.
Rough ER ER covered with ribosomes; synthesizes and begins processing proteins.
Smooth ER ER without ribosomes; synthesizes lipids, detoxifies substances, and stores calcium.
Why is rough ER called rough? Ribosomes are attached to its cytoplasmic surface.
Smooth ER functions Synthesizes lipids, detoxifies drugs/poisons, and stores calcium ions.
Rough ER functions Makes proteins and contributes to membrane production.
Golgi apparatus Modifies, sorts, and packages proteins and other products.
Cis face of Golgi The receiving side of the Golgi that receives vesicles from the ER.
Trans face of Golgi The shipping side of the Golgi that sends vesicles to other locations.
Cisternae Flattened membrane-bound sacs that make up the Golgi apparatus.
Vesicle A small membrane-bound sac that transports materials within or out of a cell.
Transport vesicle A vesicle that carries materials from one organelle or membrane to another.
Lysosome A membrane-bound compartment containing hydrolytic enzymes that digest macromolecules.
Lysosomal enzymes Enzymes that break down macromolecules inside lysosomes.
Why do lysosomal enzymes work well inside lysosomes? Lysosomes maintain an acidic environment favorable for their enzymes.
Autophagy The lysosome-mediated digestion and recycling of damaged cell components.
Food vacuole A vesicle formed during phagocytosis that contains engulfed material.
Vacuole A membrane-bound compartment with various storage and maintenance functions.
Contractile vacuole A vacuole that pumps excess water from freshwater protists.
Central vacuole A large plant-cell vacuole involved in storage, water balance, and cell growth.
What does the central vacuole contain? Cell sap containing water and dissolved substances including ions.
Peroxisome An organelle involved in metabolic processes that produce or break down hydrogen peroxide.
Cytoskeleton A network of protein fibers that supports cell shape, movement, and organelle positioning.
Microfilaments The thinnest cytoskeletal fibers, made primarily of actin.
Microtubules The thickest cytoskeletal fibers, made of tubulin; important in transport and cell division.
Intermediate filaments Cytoskeletal fibers that provide strength and help stabilize cell structures.
Centrosome A region where microtubules are organized in animal cells.
Flagellum A cellular appendage used for movement.
Microfilaments are made of Actin.
Microtubules are made of Tubulin.
Cytoskeleton functions Maintains cell shape, positions organelles, enables movement, and helps transport materials.
Plant vs. animal cells Both are eukaryotic and share many organelles, but plants have structures such as a cell wall and central vacuole.
Picture: Prokaryotic cell Know: plasma membrane, cytoplasm, nucleoid, ribosomes, and absence of a membrane-bound nucleus.
Picture: Animal cell Know: nucleus, nucleolus, ER, Golgi, lysosome, mitochondria, ribosomes, cytoskeleton, plasma membrane.
Picture: Plant cell Know: nucleus, chloroplasts, central vacuole, cell wall, plasma membrane, ER, Golgi, mitochondria, ribosomes.
Picture: Endomembrane system Know the pathway: nucleus/rough ER → transport vesicle → cis Golgi → trans Golgi → destination.
Protein secretion pathway Ribosome → rough ER → transport vesicle → cis Golgi → trans Golgi → secretory vesicle → plasma membrane.
Why do cells have organelles? Organelles compartmentalize functions and create specialized environments for cellular processes.
CHAPTER 7 — MEMBRANE STRUCTURE AND FUNCTION
Selective permeability The property of a membrane that allows some substances to cross more easily than others.
Passive transport Movement across a membrane without cellular energy input.
Active transport Movement across a membrane that requires energy.
Concentration gradient A region of space where the concentration of a substance changes.
Diffusion The spontaneous movement of a substance from higher concentration to lower concentration.
Equilibrium A condition in which concentrations are balanced and there is no net movement.
Facilitated diffusion Passive transport through a membrane protein.
Transport protein A membrane protein that helps a substance cross the membrane.
Channel protein A membrane protein forming a hydrophilic passageway for specific substances.
Aquaporin A channel protein that facilitates rapid movement of water across membranes.
Carrier protein A membrane protein that changes shape to transport a substance across a membrane.
Osmosis The diffusion of water across a selectively permeable membrane.
Tonicity The ability of a solution to cause a cell to gain or lose water.
Isotonic solution A solution with equal effective solute concentration inside and outside the cell.
Hypertonic solution A solution with greater effective solute concentration than the cell.
Hypotonic solution A solution with lower effective solute concentration than the cell.
What happens to an animal cell in a hypertonic solution? It loses water and may shrivel.
What happens to an animal cell in a hypotonic solution? It gains water and may lyse.
What happens to an animal cell in an isotonic solution? There is no net water movement and the cell maintains its size.
What happens to a plant cell in a hypotonic solution? It gains water and becomes turgid.
What happens to a plant cell in a hypertonic solution? It loses water and may undergo plasmolysis.
Turgid Firm plant cell caused by water entering the cell.
Plasmolysis A plant cell's plasma membrane pulls away from the cell wall after water loss.
Water potential A measure predicting the direction water will move; water moves toward lower water potential.
Solute potential The effect of dissolved solutes on water potential.
Pressure potential The physical pressure component of water potential.
Electrogenic pump A transport protein that generates a voltage across a membrane.
Sodium-potassium pump A major animal-cell electrogenic pump that actively transports Na+ and K+.
What does the sodium-potassium pump do? It uses ATP to pump Na+ out and K+ into the cell.
Proton pump A membrane protein that actively transports H+ across a membrane.
Why do plants use proton pumps? They generate an H+ gradient used for transport and cellular work.
Electrochemical gradient A gradient combining concentration differences and electrical differences across a membrane.
Membrane potential The electrical voltage difference across a membrane.
Cotransporter A membrane protein that couples movement of one substance to movement of another.
Active transport against a gradient Movement of a substance from lower concentration toward higher concentration using energy.
ATP-powered pump An active transport protein that uses ATP directly to move substances across a membrane.
Bulk transport Movement of large amounts of material using vesicles.
Exocytosis The movement of materials out of a cell when a vesicle fuses with the plasma membrane.
Endocytosis The movement of materials into a cell by formation of vesicles from the plasma membrane.
Phagocytosis "Cellular eating"; engulfment of large particles or cells.
Pinocytosis "Cellular drinking"; nonspecific uptake of extracellular fluid.
Receptor-mediated endocytosis Specific uptake of substances after they bind to membrane receptors.
Pseudopodia Extensions of the plasma membrane used to engulf particles during phagocytosis.
Coated pit A region of the membrane containing receptors and coat proteins that forms a vesicle.
Why is receptor-mediated endocytosis specific? Only substances that bind to the appropriate membrane receptors are concentrated for uptake.
Why is pinocytosis nonspecific? It takes in extracellular fluid and dissolved substances without selecting specific molecules.
Exocytosis sequence Vesicle moves to membrane → membranes fuse → contents released outside.
Endocytosis sequence Membrane folds inward → pocket forms → vesicle pinches off into the cell.
Passive vs. active transport Passive transport requires no cellular energy; active transport requires energy.
Simple diffusion vs. facilitated diffusion Both move down a gradient; facilitated diffusion requires a membrane protein.
Picture: Osmosis Know water moves across the membrane toward the side with greater effective solute concentration.
Picture: Sodium-potassium pump Know ATP drives movement of Na+ out and K+ into the cell.
Picture: Endocytosis Know plasma membrane folds inward and pinches off to form a vesicle.
Picture: Exocytosis Know a vesicle fuses with the plasma membrane and releases contents outside.
CHAPTER 8 — AN INTRODUCTION TO METABOLISM
Metabolism The totality of an organism's chemical reactions.
Metabolic pathway A series of chemical reactions in which the product of one reaction becomes the substrate for the next.
Catabolic pathway A metabolic pathway that breaks down molecules and generally releases energy.
Anabolic pathway A metabolic pathway that builds complex molecules and generally requires energy.
Bioenergetics The study of how energy flows through living organisms.
Energy The capacity to cause change or perform work.
Kinetic energy The energy associated with motion.
Potential energy Stored energy based on an object's location or structure.
Chemical energy Potential energy stored in chemical bonds.
Thermodynamics The study of energy transformations.
First law of thermodynamics Energy cannot be created or destroyed, only transferred or transformed.
Second law of thermodynamics Every energy transfer increases the entropy of the universe.
Entropy A measure of disorder or randomness.
Free energy Gibbs free energy; the portion of a system's energy available to perform work.
Gibbs free energy The energy available to do work in a system at constant temperature and pressure.
Exergonic reaction A reaction that releases free energy and has a negative ΔG.
Endergonic reaction A reaction that requires an input of free energy and has a positive ΔG.
Equilibrium A state in which forward and reverse reactions occur at equal rates.
What does ΔG tell you? Whether a reaction releases or requires free energy under specified conditions.
Spontaneous reaction A reaction that can occur without an input of free energy; it may still be slow.
Activation energy The energy barrier that must be overcome for a reaction to begin.
Enzyme A biological catalyst that speeds up a reaction by lowering activation energy.
Catalyst A substance that speeds a reaction without being consumed.
Substrate The reactant that an enzyme acts on.
Active site The region of an enzyme where the substrate binds and the reaction occurs.
Enzyme-substrate complex The temporary complex formed when a substrate binds to an enzyme.
Induced fit The enzyme changes shape slightly when the substrate binds, improving catalysis.
Cofactor A nonprotein helper required for some enzyme activity.
Inorganic cofactor An inorganic enzyme helper such as Zn2+, Fe2+, or Cu2+.
Coenzyme An organic cofactor; many are derived from vitamins.
Competitive inhibitor A molecule that resembles the substrate and competes for the active site.
Noncompetitive inhibitor An inhibitor that binds away from the active site and changes enzyme shape.
Allosteric regulation Regulation of an enzyme by a molecule binding at a site other than the active site.
Allosteric site A regulatory site separate from an enzyme's active site.
Activator A molecule that binds to a regulatory site and stabilizes an active enzyme form.
Inhibitor A molecule that binds to an enzyme and decreases its activity.
Cooperativity When binding of one substrate molecule affects binding of additional substrate molecules.
Feedback inhibition The end product of a metabolic pathway inhibits an earlier step in the pathway.
Why is feedback inhibition useful? It prevents unnecessary production and conserves cellular resources.
How can competitive inhibition be overcome? Increasing substrate concentration can reduce the inhibitor's effect.
How does noncompetitive inhibition work? The inhibitor binds away from the active site and changes the enzyme's shape.
Enzyme regulation methods Gene regulation and enzyme regulation.
Compartmentalization Separating metabolic processes into different cellular compartments.
Why does compartmentalization help metabolism? It organizes pathways and keeps incompatible reactions separated.
Multienzyme complex A group of enzymes in a metabolic pathway organized together.
What affects enzyme activity? Temperature, pH, substrate concentration, inhibitors, and regulatory molecules.
ATP Adenosine triphosphate; a major cellular energy-carrying molecule.
ATP structure Adenine, ribose, and three phosphate groups.
ATP hydrolysis The reaction that removes a phosphate from ATP and releases free energy.
ATP → ADP + Pi ATP hydrolysis releases energy that can be coupled to cellular work.
Phosphorylation The transfer of a phosphate group to another molecule.
Energy coupling Using energy released by an exergonic reaction to drive an endergonic reaction.
How does ATP perform cellular work? ATP hydrolysis can drive phosphorylation and other energy-requiring processes.
Picture: Enzyme reaction Know enzyme + substrate → enzyme-substrate complex → products + unchanged enzyme.
Picture: Competitive inhibition Know inhibitor occupies the active site and prevents substrate binding.
Picture: Allosteric inhibition Know inhibitor binds a regulatory site and changes enzyme shape.
Picture: Feedback inhibition Know the final product of a pathway inhibits an earlier enzyme.
CHAPTER 9 — CELLULAR RESPIRATION AND FERMENTATION
Cellular respiration The process cells use to extract energy from organic molecules and produce ATP.
Overall cellular respiration equation C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + energy.
Oxidation The loss of electrons or hydrogen; often associated with loss of energy.
Reduction The gain of electrons or hydrogen; often associated with gaining energy.
Redox reaction A chemical reaction involving the transfer of electrons between substances.
Reducing agent The substance that donates electrons and becomes oxidized.
Oxidizing agent The substance that accepts electrons and becomes reduced.
NAD+ An electron carrier that accepts electrons and hydrogen to become NADH.
NADH The reduced form of NAD+ that carries high-energy electrons.
FAD An electron carrier that can accept electrons and hydrogen.
FADH2 The reduced form of FAD that carries high-energy electrons.
Glycolysis The pathway that splits glucose into two pyruvate molecules.
Where does glycolysis occur? In the cytosol.
Does glycolysis require oxygen? No; glycolysis itself does not require oxygen.
Glycolysis starting molecule Glucose.
Glycolysis end product Two pyruvate molecules.
Glycolysis ATP production Produces a net gain of 2 ATP per glucose.
Glycolysis NADH production Produces 2 NADH per glucose.
Substrate-level phosphorylation ATP production by directly transferring a phosphate to ADP from a substrate.
Preparatory reaction The stage that converts pyruvate to acetyl CoA before the citric acid cycle.
Pyruvate oxidation location In eukaryotes, the mitochondrial matrix.
Acetyl CoA The two-carbon molecule that enters the citric acid cycle.
Citric acid cycle Series of reactions that oxidize acetyl CoA and produce electron carriers.
Krebs cycle Another name for the citric acid cycle.
Citric acid cycle location In the mitochondrial matrix of eukaryotic cells.
What enters the citric acid cycle? Acetyl CoA.
What does the citric acid cycle produce? CO2, ATP, NADH, and FADH2.
Electron transport chain (ETC) A series of protein complexes that transfer electrons and pump H+ across a membrane.
Where is the ETC located in mitochondria? The inner mitochondrial membrane.
Chemiosmosis The use of an H+ gradient to drive ATP synthesis.
Proton-motive force The energy stored in an H+ electrochemical gradient.
ATP synthase A protein complex that uses the H+ gradient to synthesize ATP.
Oxidative phosphorylation ATP production using the ETC and chemiosmosis.
Where does oxidative phosphorylation occur? At the inner mitochondrial membrane.
Final electron acceptor in aerobic respiration Oxygen.
What happens to oxygen during respiration? Oxygen accepts electrons and H+ to form water.
Why is oxygen important in aerobic respiration? It is the final electron acceptor of the ETC.
What happens if oxygen is unavailable? The mitochondrial ETC cannot continue operating normally.
Mitochondrial matrix The innermost compartment of the mitochondrion where pyruvate oxidation and the citric acid cycle occur.
Intermembrane space The region between mitochondrial membranes where H+ accumulates during ETC activity.
Inner mitochondrial membrane The membrane containing the ETC and ATP synthase.
Outer mitochondrial membrane The outer membrane surrounding the mitochondrion.
Aerobic respiration Cellular respiration using oxygen as the final electron acceptor.
Anaerobic respiration Respiration using a final electron acceptor other than oxygen.
Fermentation A pathway that regenerates NAD+ so glycolysis can continue without oxygen.
Why is fermentation necessary? It regenerates NAD+ needed for glycolysis when the ETC cannot oxidize NADH.
Alcohol fermentation Pyruvate is converted to ethanol while NADH is oxidized to NAD+.
Lactic acid fermentation Pyruvate is converted to lactate while NADH is oxidized to NAD+.
Alcohol fermentation uses Fungi and some microorganisms; important in brewing, winemaking, and baking.
Lactic acid fermentation uses Fungi and bacteria are used in producing foods such as cheese and yogurt.
Does fermentation produce much ATP? No; ATP comes mainly from glycolysis.
Substrate-level vs. oxidative phosphorylation Substrate-level directly transfers phosphate to ADP; oxidative phosphorylation uses ETC and chemiosmosis.
Why is the exact ATP yield variable? Electron carrier pathways and proton-motive force can vary, so ATP yield is not always identical.
Approximate ATP yield from one glucose About 30–32 ATP is commonly estimated for eukaryotic aerobic respiration.
Where does most ATP come from? Oxidative phosphorylation.
Where does most CO2 come from? Pyruvate oxidation and the citric acid cycle.
Where are most NADH molecules produced? Pyruvate oxidation, citric acid cycle, and glycolysis.
Where is FADH2 produced? The citric acid cycle.
ATP concentration and respiration Low ATP tends to stimulate respiration; high ATP tends to slow respiration.
How does feedback regulation control respiration? High ATP can inhibit enzymes at strategic points, reducing unnecessary ATP production.
Protein catabolism Proteins are broken down into amino acids that can enter metabolic pathways.
Deamination The removal of an amino group's nitrogen from an amino acid.
Nitrogen waste Can be excreted as ammonia, urea, or other nitrogen-containing products.
Fat catabolism Fats are broken down into glycerol and fatty acids.
Beta oxidation The breakdown of fatty acids into acetyl CoA while producing NADH and FADH2.
Why do fats yield lots of ATP? Fatty acids contain many energy-rich electrons and produce many reduced electron carriers.
Metabolic pathway intersection Glycolysis and the citric acid cycle connect carbohydrate, protein, and fat metabolism.
Picture: Cellular respiration Know the sequence: glycolysis → pyruvate oxidation → citric acid cycle → ETC/chemiosmosis.
Picture: Mitochondrion Know outer membrane, intermembrane space, inner membrane, cristae, and matrix.
Picture: ETC Know electrons move through complexes, H+ is pumped, and H+ flows through ATP synthase.
Picture: Fermentation Know glycolysis produces pyruvate and NADH; fermentation regenerates NAD+.
Picture: Beta oxidation Know fatty acids are broken into acetyl CoA and generate NADH/FADH2.
CHAPTER 10 — PHOTOSYNTHESIS
Photosynthesis The process by which plants and other organisms use light energy to make chemical energy.
Overall photosynthesis equation 6 CO2 + 6 H2O + light → C6H12O6 + 6 O2.
Autotroph An organism that produces its own organic molecules from inorganic sources.
Photoautotroph An organism that uses light energy to produce organic molecules.
Chloroplast The organelle where photosynthesis occurs in plants and algae.
Chlorophyll A pigment that absorbs light energy for photosynthesis.
Thylakoid A flattened membrane sac inside a chloroplast containing photosystems and electron transport proteins.
Granum A stack of thylakoids.
Stroma The fluid-filled region surrounding thylakoids in a chloroplast.
Light reactions The photosynthetic reactions that capture light energy and produce ATP and NADPH.
Calvin cycle The set of reactions that uses ATP and NADPH to convert CO2 into carbohydrate.
Photophosphorylation Production of ATP using light energy.
Photosystem A complex of pigments and proteins that captures light energy.
Photosystem II (PSII) The photosystem that absorbs light and provides electrons from water to the ETC.
Photosystem I (PSI) The photosystem that re-energizes electrons and helps produce NADPH.
Reaction center The chlorophyll-containing center of a photosystem where light energy drives electron transfer.
P680 The reaction-center chlorophyll of Photosystem II.
P700 The reaction-center chlorophyll of Photosystem I.
What happens to water in the light reactions? Water is split, providing electrons and H+ and releasing O2.
Where does oxygen from photosynthesis come from? Water.
Linear electron flow Electron flow from water through PSII and PSI that produces ATP, NADPH, and O2.
NADPH A high-energy electron carrier produced during the light reactions.
How is ATP produced in the light reactions? H+ accumulates in the thylakoid space and flows through ATP synthase into the stroma.
Where are ATP and NADPH produced? On the stroma side of the thylakoid membrane.
Where does the Calvin cycle occur? In the chloroplast stroma.
Carbon fixation The incorporation of CO2 into an organic molecule.
Rubisco The enzyme that catalyzes the fixation of CO2 to RuBP.
RuBP Ribulose bisphosphate; the five-carbon CO2 acceptor in the Calvin cycle.
Calvin cycle phase 1 Carbon fixation.
Calvin cycle phase 2 Reduction.
Calvin cycle phase 3 Regeneration of the CO2 acceptor RuBP.
Carbon fixation reaction CO2 combines with RuBP and forms molecules of 3-phosphoglycerate.
3-phosphoglycerate (3-PGA) The three-carbon product formed after CO2 is fixed in the Calvin cycle.
Calvin cycle reduction phase ATP and NADPH are used to convert 3-PGA into G3P.
G3P Glyceraldehyde-3-phosphate; a three-carbon sugar produced by the Calvin cycle.
Calvin cycle regeneration phase ATP is used to rearrange G3P molecules to regenerate RuBP.
How many CO2 are needed for one net G3P? Three CO2 molecules must enter the cycle.
How many turns produce one net G3P? Three turns of the Calvin cycle.
How many G3P are initially produced from 3 CO2? Six G3P molecules are produced, but only one is a net gain.
What happens to the other five G3P? They are rearranged to regenerate three RuBP molecules.
What powers the Calvin cycle? ATP and NADPH from the light reactions.
Is the Calvin cycle directly powered by sunlight? No; it uses ATP and NADPH produced by the light reactions.
Anabolic nature of the Calvin cycle It uses energy to build carbohydrate from smaller molecules including CO2.
Cyclic electron flow Electron flow involving only PSI that produces ATP but not NADPH or O2.
What does cyclic electron flow produce? ATP but no NADPH and no O2.
Why is cyclic electron flow useful? It can provide additional ATP when more ATP is needed relative to NADPH.
Cyclic electron flow electrons Excited electrons from PSI cycle back through an electron transport pathway.
Chemiosmosis in chloroplasts H+ flows through ATP synthase from the thylakoid space into the stroma to make ATP.
Chemiosmosis in mitochondria H+ flows from the intermembrane space into the mitochondrial matrix through ATP synthase.
Similarity of mitochondrial and chloroplast chemiosmosis Both use an ETC, proton gradient, ATP synthase, and chemiosmosis to make ATP.
Major difference between the two Chloroplasts use light energy; mitochondria use energy from oxidation of food.
Photorespiration A process in which rubisco binds O2 instead of CO2, consuming energy without producing sugar.
Why does photorespiration happen? When stomata close, CO2 falls and O2 rises, increasing rubisco's oxygenase activity.
Rubisco's problem Rubisco can act as either a carboxylase or oxygenase depending on CO2 and O2 conditions.
Why is photorespiration considered wasteful? It consumes O2 and organic fuel without producing ATP or sugar.
Stomata Pores in plant leaves that regulate gas exchange and water loss.
Why do plants close stomata? To reduce water loss during hot or dry conditions.
Trade-off of closing stomata Closing stomata conserves water but reduces CO2 entry and can increase photorespiration.
C3 plant A plant that initially fixes CO2 into a three-carbon compound during the Calvin cycle.
C4 plant A plant that first fixes CO2 into a four-carbon compound to reduce photorespiration.
C4 photosynthesis Uses spatial separation of initial carbon fixation and the Calvin cycle.
PEP carboxylase Enzyme that fixes CO2 into a four-carbon compound in C4 plants.
Mesophyll cells Cells where initial CO2 fixation occurs in C4 plants.
Bundle-sheath cells Cells where the Calvin cycle occurs in C4 plants.
How does C4 photosynthesis reduce photorespiration? It concentrates CO2 around rubisco in bundle-sheath cells.
C4 pathway sequence CO2 fixed in mesophyll → four-carbon compound → bundle-sheath cell → CO2 released → Calvin cycle.
Plasmodesmata Channels connecting adjacent plant cells and allowing substances to pass between them.
CAM photosynthesis A photosynthetic adaptation that separates CO2 fixation and the Calvin cycle by time.
CAM stomata Open at night to take in CO2 and close during the day to conserve water.
C4 vs. CAM C4 separates processes spatially; CAM separates them temporally.
Why are C4 and CAM adaptations useful? They help plants conserve water and reduce photorespiration.
Picture: Chloroplast Know outer/inner membranes, stroma, thylakoids, grana, and thylakoid space.
Picture: Thylakoid membrane Know photosystems, ETC, H+ gradient, ATP synthase, and NADPH production.
Picture: Linear electron flow Know H2O → PSII → ETC → PSI → NADPH, with ATP made through chemiosmosis.
Picture: Cyclic electron flow Know PSI electrons cycle through the ETC and return to PSI; ATP is produced.
Picture: Calvin cycle Know carbon fixation → reduction → regeneration.
Picture: C4 pathway Know mesophyll cells initially fix CO2 and bundle-sheath cells perform the Calvin cycle.
Photosynthesis vs. cellular respiration Photosynthesis stores energy in carbohydrates; cellular respiration releases energy from carbohydrates.
Photosynthesis location Chloroplasts.
Cellular respiration location Cytosol and mitochondria in eukaryotic cells.
Photosynthesis energy source Light energy.
Cellular respiration energy source Chemical energy stored in organic molecules.
Photosynthesis electron source Water.
Cellular respiration final electron acceptor Oxygen during aerobic respiration.
Photosynthesis produces O2, ATP, NADPH, and carbohydrates.
Cellular respiration produces ATP, CO2, and H2O.
Light reactions vs. Calvin cycle Light reactions make ATP/NADPH; Calvin cycle uses ATP/NADPH to make carbohydrate.
What molecule enters the Calvin cycle? CO2.
What molecule leaves the Calvin cycle? G3P.
What molecule is regenerated in the Calvin cycle? RuBP.
What enzyme fixes CO2? Rubisco.
What does ATP do in the Calvin cycle? Provides energy for phosphorylation and regeneration steps.
What does NADPH do in the Calvin cycle? Provides high-energy electrons for reduction.