IB Exam Review Notes

Water and Life (Unit 1)

Water (A1.1)

• A1.1.1 – Water as the Medium for Life
  • First cells originated in water (oceans).
  • Most life processes occur in water as a solvent.
  • A membrane separates internal water (cytoplasm) from the external environment.

Hydrogen Bonding (A1.1.2)

• A1.1.2 – Hydrogen Bonds
  • Hydrogen bonds are a consequence of polar covalent bonds within water molecules.
  • Polar covalent bonds form due to unequal sharing of electrons.
  • Allows for hydrogen bonding between water molecules.

Cohesion (A1.1.3)

• A1.1.3 – Cohesion
  • Cohesion of water molecules is due to hydrogen bonding.
  • Consequences for organisms:
    • Transport of water under tension in the xylem (cohesion-tension theory).
    • Surface tension as habitats.

Adhesion (A1.1.4)

• A1.1.4 – Adhesion
  • Adhesion of water to polar or charged materials.
  • Impacts for organisms:
    • Capillary action (water flowing against gravity).
    • Xylem (transpiration stream).
    • Soil (from the deeper water table).

Solvent Properties (A1.1.5)

• A1.1.5 – Solvent Properties
  • Solvent properties of water are linked to its role as a medium for metabolism and transport in plants and animals.
  • Hydrophilic substances dissolve in water, allowing for transport (e.g., in blood or the xylem).
  • Enzymes catalyze reactions in aqueous solutions (metabolism).
  • Hydrophobic substances do not dissolve in water.

Physical Properties (A1.1.6)

• A1.1.6 – Physical Properties
  • Physical properties of water and consequences for aquatic animals:
    • Buoyancy (enables floating).
    • Viscosity (direct correlation with solute concentration).
    • Thermal conductivity (absorbing and transferring heat).
    • Specific heat capacity (absorbs/releases heat without changing temperatures).

Origin of Water on Earth (HL) (A1.1.7, A1.1.8)

• A1.1.7 – Origin of Water
  • Abundance of water on Earth has allowed life to evolve.
  • Extraplanetary origin: asteroids.
  • Retention due to gravity and temperatures low enough for water to be a liquid.
• A1.1.8 – Extraterrestrial Life
  • Relationship between the search for extraterrestrial life and the presence of water.
  • The position of Earth in relation to the Sun is in the Goldilocks zone (the habitable zone).
  • Allows water to exist in liquid form (and thus support life).

Origins of Cells (HL only) (A2.1)

Formation of Carbon Compounds (HL) (A2.1.1)

• A2.1.1 – Early Earth Conditions
  • Early Earth conditions:
    • Lack of free oxygen: no ozone.
    • Higher concentrations of carbon dioxide and methane: higher temperatures and UV light penetration.
  • Allowed carbon compounds to form spontaneously.

Functions of Life (HL) (A2.1.2)

• A2.1.2 – Cells as Self-Sustaining Units
  • Living organisms must carry out all the functions of life:
    • Metabolism (chemical reactions resulting in energy conversion).
    • Growth.
    • Reproduction (passing hereditary molecules on to offspring).
    • Response (to environmental stimuli).
    • Homeostasis (maintaining a constant internal environment).
    • Nutrition (breaking down compounds to obtain energy).
    • Excretion (release of waste products).
  • Cell theory: all organisms are composed of one or more cells; cells are the smallest unit of life; all cells come from pre-existing cells.

Evolution of the Cell (HL) (A2.1.3)

• A2.1.3 – Spontaneous Origin of Cells
  • The first cells appeared in a pre-biotic environment (abiogenesis).
  • Difficult to test: exact conditions of pre-biotic Earth cannot be replicated; protocells did not fossilize.
  • Requirements for the evolution of the first cells:
    • Catalysis (of simple organic molecules from inorganic molecules).
    • Primordial soup hypothesis and the Miller-Urey experiment.
    • Self-assembly (of simple organic molecules into more complex polymers).
    • Compartmentalization (via membranes).
    • Self-replication of molecules (enabling inheritance).

Catalysis – Origin of Carbon Compounds (HL) (A2.1.4)

• A2.1.4 – Evidence for Origin of Carbon Compounds
  • Miller-Urey experiment demonstrated the non-living synthesis of organic materials (carbon compounds) from inorganic compounds.
  • Produced:
    • Hydrocarbons and amino acids.
    • A reducing environment (oxidation prevented by the absence of oxygen).
    • Favorable for development of carbon compounds.

Compartmentalization – Formation of Vesicles (HL) (A2.1.5)

• A2.1.5 – Spontaneous Formation of Vesicles
  • Membrane-bound compartments are needed to allow the internal chemistry to become different from the outside.
  • Fatty acids spontaneously organize into double-layered bubbles (vesicles).
  • Provides a boundary between the internal and external environment (compartmentalization).

Self-Replication – RNA (HL) (A2.1.6)

• A2.1.6 – RNA as First Genetic Material
  • RNA is thought to be:
    • The first genetic material (because it can self-replicate).
    • Can assemble spontaneously into nucleotides.
    • The enzymes of the earliest cells (because it can act as a catalyst).

LUCA Evidence (HL) (A2.1.7, A2.1.8, A2.1.9)

• A2.1.7 – Last Universal Common Ancestor
  • Evidence of the last universal common ancestor (LUCA):
    • Universal genetic code (using transcription and translation).
    • Shared genes across organisms.
    • Other lifeforms probably coexisted with LUCA but became extinct.
• A2.1.8 – Estimating Dates
  • Approaches used to estimate dates of the first living cells and the last universal common ancestor:
    • Biochemical evidence (stromatolites formed by microbes).
    • Phylogenetic comparisons (comparing genomes).
    • Molecular clock (using the mutation rate of DNA, RNA, or proteins to determine when divergence occurred).
• A2.1.9 – Hydrothermal Vents
  • Evidence for evolution of the last universal common ancestor in the vicinity of hydrothermal vents:
    • Fossil evidence of life from ancient seafloor hydrothermal vent precipitates.
    • Conserved sequences from genomic analysis.

Cells (Unit 2)

Cell Structure (A2.2)

Organelles and Compartmentalization (B2.2)

Cell Specialization (B2.3)

Cells and Microscopes (A2.2.1, A2.2.2)

• A2.2.1 – Cells as Basic Unit
  • Cells are the basic structural unit of all living organisms.
• A2.2.2 – Microscopy Skills
  • Magnification = measured size of image / actual size of specimen.
  • Example:
    • Image length = 50 mm
    • Actual length = 5 µm
    • Magnification = \frac{50 \text{ mm}}{5 \mu \text{m}} = \frac{50,000 \mu \text{m}}{5 \mu \text{m}} = 10,000 \times

Advanced Microscopy (A2.2.3)

• A2.2.3 – Developments in Microscopy
  • Electron microscopy:
    • Scanning electron microscopes (SEM): surfaces.
    • Transmission electron microscopes (TEM): inner structures.
    • Freeze fracture (creates a plane through the sample).
    • Cryogenic electron microscopy (proteins).
  • Light microscopy:
    • Fluorescent stains (cellular components).
    • Immunofluorescence (using fluorescent antibodies to observe living tissue).

Cell Structures – All Cells (A2.2.4)

• A2.2.4 – Common Structures
  • Structures common to cells in all living organisms:
    • DNA (as genetic material).
    • Cytoplasm (composed mainly of water).
    • Plasma membrane (comprised of lipids).

Cell Structures – Prokaryotes (A2.2.5)

• A2.2.5 – Prokaryote Cell Structure
  • Cell wall.
  • Plasma membrane.
  • Cytoplasm.
  • Naked DNA in a loop.
  • 70S ribosomes.

Cell Structures – Eukaryotes (A2.2.6)

• A2.2.6 – Eukaryote Cell Structure
  • Plasma membrane (enclosing a compartmentalized cytoplasm with 80S ribosomes).
  • Nucleus (with chromosomes made of DNA and histones, contained in a double membrane with pores).
  • Membrane-bound cytoplasmic organelles:
    • Mitochondria.
    • Endoplasmic reticulum.
    • Golgi apparatus.
    • Vesicles/vacuoles (e.g., lysosomes).
    • Cytoskeleton (made of microtubules and microfilaments).

Unicellular Organisms (A2.2.7)

• A2.2.7 – Processes of Life
  • Homeostasis (using a cell membrane to control movement of materials in and out).
  • Nutrition (using vacuoles to carry out digestion).
  • Metabolism (using mitochondria or areas of enzymes).
  • Excretion (using vacuoles to store waste).
  • Movement (using cilia or flagella).
  • Response to stimuli (using cilia or flagella to move).
  • Growth (using ribosomes).
  • Reproduction.

Differences in Eukaryotes (A2.2.8)

• A2.2.8 – Animal, Fungi, and Plant structures
  • Cell Wall:
    • Plant Cells: Cellulose
    • Animal Cells: None
    • Fungal Cells: Chitin
  • Chloroplasts:
    • Plant Cells: Yes
    • Animal Cells: No
    • Fungal Cells: No
  • Vacuoles:
    • Plant Cells: Large and Central; Carbohydrate Storage
    • Animal Cells: Small and Numerous; Many functions
    • Fungal Cells: Small and Numerous; Many functions
  • Cilia or Flagella:
    • Plant Cells: Rare
    • Animal Cells: Sometimes
    • Fungal Cells: Sometimes
  • Centrosomes and/or Centrioles:
    • Plant Cells: Centrosomes only
    • Animal Cells: Both
    • Fungal Cells: Centrosomes only

Endosymbiosis (HL) (A2.2.12)

• A2.2.12 – Origin of Eukaryotic Cells
  • All eukaryotes evolved from a common unicellular ancestor that had a nucleus and reproduced sexually.
  • Mitochondria and chloroplasts evolved by endosymbiosis.
    • Symbiotic relationship: larger cell provided protection and carbon compounds; smaller cell (eventually) provided ATP.
    • Evidence: similarities with free-living bacteria (mitochondria and aerobic bacteria; chloroplasts and photosynthetic cyanobacteria).
    • Both contain 70S ribosomes, naked circular DNA, ability to replicate (via binary fission).

Biochemistry (Unit 3)

Carbohydrates and Lipids (B1.1)

Proteins (B1.2)

Condensation Reactions (B1.1.2)

• B1.1.2 – Production of Macromolecules
  • Monomers linked via covalent bonds to form polymers/macromolecules.
  • One water molecule formed per reaction.
  • Examples:
    • Monosaccharides form polysaccharides (glucoses form starch).
    • Amino acids form polypeptides.
    • Nucleotides form nucleic acids.

Hydrolysis Reactions (B1.1.3)

• B1.1.3 – Digestion of Polymers
  • Polymers broken down into monomers by hydrolyzing enzymes (digestion).
  • Each reaction requires one water molecule as a reactant (split to provide the –H and –OH groups).

Monosaccharides (B1.1.4)

• B1.1.4 – Form and Function
  • Ribose: pentose monosaccharide (5-carbon sugar).
  • Glucose: hexose monosaccharide (6-carbon sugar).
  • Molecular stability (due to having stable covalent bonds).
  • High solubility (due to being polar).
  • Easily transportable (due to solubility in water).
  • Yields a great deal of energy (from oxidation reactions that break its covalent bonds).

Polysaccharides – Energy Storage (B1.1.5)

• B1.1.5 – Energy Storage Compounds
  • Starch (amylose and amylopectin in plants) and glycogen (in animals) are compact due to coiling and branching during polymerization.
  • Relatively insoluble (due to large molecular size).
  • Relatively easy to:
    • Add α-glucose monomers to build energy stores.
    • Remove α-glucose monomers to mobilize energy stores.

Polysaccharides – Structural (B1.1.6)

• B1.1.6 – Structure of Cellulose
  • Cellulose is formed in straight chains (due to alternating orientation of β-glucose monomers).
  • Can be grouped in bundles and cross-linked with hydrogen bonds.
  • Insoluble in water.

Lipids (B1.1.8)

• B1.1.8 – Hydrophobic Properties
  • Lipids have non-polar covalent bonds between carbon and hydrogen.
  • Hydrophobic.
  • Dissolve in non-polar solvents (sparingly soluble in aqueous solutions).
  • Fats, oils, waxes, and steroids.

Triglycerides and Phospholipids (B1.1.9)

• B1.1.9 – Formation
  • One glycerol molecule can link:
    • Three fatty acid molecules (forming a triglyceride + 3 water molecules).
    • Two fatty acid molecules and one phosphate group (forming a phospholipid + 3 water molecules).

Fatty Acids (B1.1.10)

• B1.1.10 – Types of Fatty Acids
  • Saturated, Monounsaturated, Polyunsaturated
    | Characteristic | Saturated | Monounsaturated | Polyunsaturated |
    | :----------------------------- | :------------------------ | :------------------------ | :---------------------- |
    | Bonds between carbons | Single bonds only | One double bond | More than one double bond |
    | Melting point | Higher | Lower | Lower |
    | State at room temperature | Solid (fat) | Liquid (oil) | Liquid (oil) |
    | Used for energy storage in: | Animals (endotherms) | Plants and animals (endotherms) | Plants |

Adipose Tissue (B1.1.11)

• B1.1.11 – Triglycerides in Adipose Tissue
  • Adipose tissue stores fat (triglycerides).
  • Hydrolyzed and used in cell respiration in the absence of carbohydrates.
  • Long-term energy storage: insoluble in body fluid.
  • Provide more energy than carbohydrates (per gram).
  • Endotherms have a thick layer of adipose tissue (blubber) to provide thermal insulation.

Phospholipid Bilayers (B1.1.12)

• B1.1.12 – Formation of Bilayers
  • Phospholipids are amphipathic molecules (hydrophilic and hydrophobic regions).
  • Form a bilayer in aqueous solutions – the foundation of the plasma membrane.

Steroid Hormones (B1.1.13)

• B1.1.13 – Steroids Through Bilayers
  • Steroids are hydrophobic hormones and can pass through the fatty acid layers of cell/nuclear membranes.
  • Made from cholesterol.
  • Examples: estradiol and testosterone.

Amino Acids - Structure

Amino Acids - Structures -B1.2.1

• Generalized Structure of an Amino Acid

• Consisting of:

  • Amine Group (-NH_2)
  • Carboxyl Group (-COOH)
  • Variable Group (R-Group)

Amino Acids – Condensation Reactions (B1.2.2)

• B1.2.2 – Forming Dipeptides and Longer Chains
  • Amino acid 1 + amino acid 2 → dipeptide + water.

Essential Amino Acids (B1.2.3)

• B1.2.3 – Dietary Requirements
  • Essential amino acids (9 total) cannot be synthesized in human cells and must be obtained from food.
  • Non-essential amino acids (11 total) can be synthesized in our cells from other amino acids.

Variety in Polypeptides (B1.2.4)

• B1.2.4 – Infinite Variety
  • 20 different amino acids are coded for in the genetic code.
  • Peptide chains can have any number of amino acids.
  • Amino acids can be in any order.
  • Examples: hemoglobin, keratin, lipase, collagen, histones, insulin.

pH and Temperature (B1.2.5)

• B1.2.5 – Effect on Protein Structure
  • Protein function depends on having a precise three-dimensional shape.
  • Denaturation: loss of shape (and therefore, function).
  • Can be caused by:
    • Temperatures higher than the optimum.
    • Environmental pH that is not close to the optimum pH.

R-Groups (HL) (B1.2.6)

• B1.2.6 – Chemical Diversity
  • R-groups determine the properties of assembled polypeptides.
    • Hydrophobic
    • Hydrophilic (polar, acidic, or basic).

Primary Structure (HL) (B1.2.7)

• B1.2.7 – Impact on Conformation
  • Primary structure: the number and sequence of amino acids held together by peptide bonds.
  • Determines the three-dimensional shape of the protein.
  • Proteins have precise, predictable, and repeatable structures.

Secondary Structure (HL) (B1.2.8)

• B1.2.8 – Pleating and Coiling
  • Secondary structure: if primary structure contains only non-polar R-groups, they will form an alpha helix or a beta-pleated sheet.
  • Held together/stabilized by hydrogen bonds.

Tertiary Structure (HL) (B1.2.9)

• B1.2.9 – Dependence on Bonds and Interactions
  • Tertiary structure: overall three-dimensional structure of a protein.
  • Pairs of cysteines form very strong disulfide bonds.
  • Amine and carboxyl groups in R-groups can become:
    • Positively charged (by binding of hydrogen ions).
    • Negatively charged (by dissociation of hydrogen ions).
  • Two oppositely-charged R-groups form ionic bonds.
  • Non-polar amino acids form hydrophobic interactions (interior regions).
  • Polar amino acids form hydrogen bonds (exterior regions).

Proteins – Tertiary Structure (HL) (B1.2.10)

• B1.2.10 – Effect of Polar and Non-Polar Amino Acids
  • Water-soluble proteins: hydrophobic amino acids clustered in the core of globular proteins.
  • Example: hydrophobic regions help integral proteins embed in membranes.

Quaternary Structure (HL) (B1.2.11)

• B1.2.11 – Non-Conjugated and Conjugated Proteins
  • Quaternary structure: two or more polypeptide chains bonded together to make a single molecule.
  • Non-conjugated: only protein groups (e.g., insulin).
  • Conjugated: includes one or more non-protein groups (e.g., hemoglobin).

Form and Function (HL) (B1.2.12)

• B1.2.12 – Globular and Fibrous Proteins
  • Fibrous proteins have a regular and geometric shape.
    • Structural uniformity makes it good for building (e.g., collagen).
  • Globular proteins have a wide variety of amino acids.
    • Allows for specialization to a specific purpose (e.g., insulin).

Enzymes (Unit 4)

Enzymes and Metabolism (C1.1)

Enzymes and Metabolism (C1.1.1, C1.1.2)

• C1.1.1 – Enzymes as Catalysts
  • Enzymes: organic catalysts that increase the rates of reaction in cells.
• C1.1.2 – Role of Enzymes
  • Metabolism: all the chemical reactions that occur in an organism.
    • Each reaction controlled by a specific enzyme (enzymes control metabolism).

Metabolism (C1.1.3)

• C1.1.3 – Anabolic and Catabolic Reactions
  

• C1.1.4 – Globular Proteins with Active Site
  • Enzymes are globular proteins.
  • Enzymes have an active site with a shape complementary to their substrate.
    • Active sites are composed of only a few amino acids.
    • Other amino acids interact to give the active site its properties for catalysis.
    • Shape changes cause denaturation.

Induced-Fit Binding (C1.1.5)

• C1.1.5 – Substrate and Active Site Interactions
  • Induced-fit model: both substrate and enzyme change shape when binding occurs.
    • Shape changes of the substrate put stress on its bonds, causing it to become destabilized (more likely to react).

Molecular Motion (C1.1.6)

• C1.1.6 – Motion and Collisions
  • Movement is needed for a substrate molecule and an active site to come together.
  • Large substrate molecules and enzymes can be immobilized by being embedded in membranes (to increase the efficiency of collisions).

Enzyme Action (C1.1.7)

• C1.1.7 – Structure, Specificity, and Denaturation
  • Active site must be a specific shape to allow formation of the enzyme-substrate complex.
  • Denaturation changes the shape of the active site:
    • Substrate can’t bind.
    • Reaction can’t occur.

Factors Affecting Enzyme Activity (C1.1.8)

• C1.1.8 – Temperature, pH, and Substrate Concentration
  • Collision theory: reactants must collide with sufficient energy and correct orientation.
    • Temperature: molecules move faster in higher temperatures, allowing more collisions.
      • High temperatures can denature an enzyme.
    • pH: changes in pH can denature an enzyme.
    • Substrate concentration: more substrate allows more collisions.
      • Reaction rate plateaus at enzyme saturation.

Measuring Reaction Rates (C1.1.9)

• C1.1.9 – Measurements in Enzyme-Catalyzed Reactions
  • The rate of an enzyme-controlled reaction can be measured using:
    • Rate at which substrate is used.
    • Rate at which the product is produced.

Activation Energy (C1.1.10)

• C1.1.10 – Effect of Enzymes
  • Energy required to break bonds within the substrate.
    • Activation energy: amount of energy required for a reaction to occur.
    • Enzymes lower the activation energy of the reaction.
    • Energy is released when bonds are made to form the product.

Intracellular vs. Extracellular Reactions (HL) (C1.1.11)

• C1.1.11 – Reactions Location
  • Intracellular reactions occur within a cell.
    • Examples: glycolysis and the Krebs cycle.
  • Extracellular reactions occur outside a cell.
    • Example: chemical digestion in the gut.

Metabolic Efficiency (HL) (C1.1.12)

• C1.1.12 – Heat Energy
  • Metabolic reactions are not 100% efficient in energy transfer.
    • Heat generation is inevitable.
  • Endotherms depend on this heat production for maintenance of constant body temperature.

Metabolic Pathways (HL) (C1.1.13)

• C1.1.13 – Cyclical and Linear Pathways
  • Metabolic pathways (specific sequences of reactions) can be:
    • Linear (as in glycolysis).
    • Cyclical (as in the Krebs cycle and Calvin cycle).

Non-competitive Inhibition (HL) (C1.1.14)

• C1.1.14 – Allosteric Sites
  • Non-competitive inhibition (allosteric inhibition):
    • Specific substances (inhibitors) can bind to an allosteric site and cause a conformational change of the enzyme.
    • Active site changes shape, preventing the substrate from binding (preventing the reaction).
    • Binding is reversible and the enzyme can return to its normal shape.
    • Not affected by substrate concentration.

Competitive Inhibition (HL) (C1.1.15)

• C1.1.15 – Reversible Binding
  • Competitive inhibition: a competitive inhibitor competes with the substrate for the active site.
    • Overcome by increasing the substrate concentration.
    • Example: statins bind with the active site of an enzyme involved in the synthesis of cholesterol, reducing cholesterol production.

Feedback Inhibition (HL) (C1.1.16)

• C1.1.16 – Regulation
  • Feedback inhibition (or end product inhibition) prevents unnecessary reactions from occurring.
    • High concentrations of the end product result in inhibition of the first reaction in the pathway via non-competitive inhibition.
    • Example: isoleucine binds with the allosteric site of the first enzyme used in its production pathway, preventing the binding of the initial substrate (threonine).

Mechanism-Based Inhibition (HL) (C1.1.17)

• C1.1.17 – Irreversible Inhibitor
  • Transpeptidase catalyzes the last step in the formation of bacterial cell walls.
    • Mechanism-based inhibition: penicillin irreversibly binds to the active site of transpeptidase.
    • Bacterial resistance to penicillin occurs through:
      • Changing the shape of penicillin by penicillinase.
      • Mutations changing the shape of the active site of transpeptidase.

Energetics (Unit 5)

ATP – Structure and Function (C1.2.1)

• C1.2.1 – Energy Distribution
  • Adenosine triphosphate (ATP) is a nucleotide that functions as the energy currency of the cell.
    • The last two phosphate groups are attached to the main molecule by high-energy bonds (unstable covalent bonds with low activation energy that are easily broken by hydrolysis).
    • Hydrolysis of ATP releases free energy to perform cellular work.

ATP – Life Processes (C1.2.2)

• C1.2.2 – Activities using ATP
  • Active transport.
  • Synthesis of macromolecules (anabolism).
  • Movement of the whole cell (e.g., via flagella).
  • Movement of cell components (e.g., chromosomes).

ATP and ADP (C1.2.3)

• C1.2.3 – Energy Transfer
  • Hydrolysis of ATP to ADP + P: energy is released (exergonic).
  • Synthesis of ATP from ADP + P: energy is required (endergonic).
    • Energy is stored in the high-energy bond between the last two phosphate groups.

Respiration (C1.2.5)

• C1.2.5 – Anaerobic and Aerobic
  • Respiration: the synthesis of ATP using the energy released from the breakdown of carbon compounds.
  • Types of respiration:
    • Aerobic cell respiration (using an ETC with oxygen).
    • Anaerobic cell respiration (using an ETC without oxygen).
    • Fermentation (without using an ETC):
      • alcoholic fermentation
      • lactic acid fermentation.

Respiration in Humans (C1.2.5)

Differences in types of Human Respiration.

Cell Respiration (C1.2.4)

• C1.2.4 – ATP Production
  • Cell respiration: a type of respiration that uses an ETC.
    • Can be aerobic or anaerobic.
    • Principal substrates: glucose and fatty acids (other carbon compounds can be used).

Cell Respiration – Rates (C1.2.6)

• C1.2.6 – Variables Affecting Rate
  • Factors affecting the rate of cell respiration:
    • Temperature (optimum of 20-30°C; decreasing as it deviates).
    • Carbon dioxide concentration (inversely related).
    • Oxygen concentration (directly related in aerobic cell respiration; none used in anaerobic cell respiration).
    • Glucose concentration (directly related).
    • Type of cell (dependent on energy requirements).

Cell Respiration – Rates (C1.2.6)

• Respirometers can be used to calculate the rate of cell respiration by measuring the oxygen rate of exchange
  Aerobic cell respiration
  Anaerobic cell respiration

NAD+ (HL) (C1.2.7)

• C1.2.7 – Hydrogen Carrier
  • Oxidation: losing electrons/hydrogen; gaining oxygen.
    • Results in a compound with lower potential energy.
  • Reduction: gaining electrons/hydrogen; losing oxygen.
    • Results in a compound with higher potential energy.
  • Nicotinamide adenine dinucleotide (NAD+): a coenzyme that carries out oxidation and reduction in cell respiration.
    • Acts as a hydrogen carrier:
      • NAD+ + hydrogen = NADH (i.e., reduced NAD).
      • NADH – hydrogen = oxidized/dehydrogenated NAD+.

Glycolysis (HL) (C1.2.8)

• C1.2.8 – Glucose to Pyruvate
  • Glycolysis: the initial breakdown of glucose.
    • Phosphorylation: Two phosphates (from two ATP) are added to glucose
    • Lysis: Split into 2 3C molecules (TP/G3P)
    • Oxidation: Each is oxidized to tow NADH are formed - Another phosphate is added to each
    • ATP formation: The two phosphates are removed from each (added to ADP -> 4 ATP) - tow Pyruvate molecules are formed.

Fermentation (HL) (C1.2.9)

• C1.2.9 – Pyruvate to Lactate
  • If no oxygen is present, anaerobic respiration (fermentation) will occur.
    • Animals: pyruvate + NADH = lactate + NAD+.
    • Plants/yeast: pyruvate + NADH = ethanol + carbon dioxide + NAD+.
  • Regeneration of NAD+ allows glycolysis (and the production of