Chapter 1: Cell Theory and Evolution

Cell Theory

The cell theory is a fundamental concept in biology, stating that all living organisms are composed of cells and that all cells arise from preexisting cells.

• Definition: The cell is the basic unit of life in all living things.

• Pattern: All organisms are made of cells.

• Process: All cells come from preexisting cells.

• Spontaneous Generation: An outdated theory that cells could arise from nonliving material; disproved by experiments such as the straight neck and swan neck flask experiments.

• Example: In the swan neck flask experiment, cells did not grow in the broth unless exposed to outside air, supporting the idea that cells arise from other cells.

Theory of Evolution by Natural Selection

Evolution explains the diversity of life through changes in species over time, driven by natural selection.

• Pattern: Species are related by common ancestry.

• Process: Natural selection causes characteristics of a population to be modified from generation to generation.

• Key Points:

  1. Individuals have differences that are heritable.

  2. Some differences make individuals more suitable for reproduction.

Chapter 2: Chemical Foundations of Biology

Atoms and Bonds

Atoms are the building blocks of matter, and their interactions form the basis of chemical bonds essential for biological molecules.

• Electron: Negatively charged particle; proton: positively charged; neutron: neutral.

• Atomic Number: Number of protons in an atom.

• Mass Number: Sum of protons and neutrons.

• Ionic Bonds: Attraction between oppositely charged ions (transfer of electrons).

• Covalent Bonds: Sharing of electrons between atoms.

• Nonpolar Covalent Bonds: Electrons are shared equally.

• Polar Covalent Bonds: Electrons are not shared equally; creates a dipole.

• Electronegativity: Tendency of an atom to attract electrons. Electronegativity scale: O > N > C ≈ H.

Additional info: Electronegativity differences determine bond polarity and molecular interactions.

Properties of Water

Hydrogen Bonding and Water's Unique Properties

Water's structure and hydrogen bonding give it unique properties essential for life.

• Hydrogen Bonds: Weak bonds between partially charged regions of water molecules.

• Versatility as a Solvent: Water dissolves many substances due to its polarity.

• Cohesion: Water molecules stick together, leading to surface tension.

• Expansion upon Freezing: Ice is less dense than liquid water due to hydrogen bond arrangement.

• Ability to Stabilize Heat: High specific heat and high heat of vaporization.

Biological Polymers

Polymerization and Hydrolysis

Biological macromolecules are formed by linking monomers through condensation reactions and broken down by hydrolysis.

• Condensation Reaction: Joins monomers, releases water.

• Hydrolysis: Breaks polymers into monomers, consumes water.

Chapter 6: Lipids and Membranes

Classes of Lipids

Lipids are hydrophobic molecules that form the basis of biological membranes.

• Types: Fat, Steroid, Phospholipid.

• Phospholipids: Amphipathic molecules with hydrophilic heads and hydrophobic tails.

• Lipid Bilayer: Forms the cell membrane, with tails facing inward and heads facing outward.

• Fluidity: Determined by lipid composition and temperature.

Membrane Structure and Permeability

Cell membranes are selectively permeable, allowing certain substances to pass while blocking others.

• Unsaturated vs. Saturated Lipids: Unsaturated increase permeability; saturated decrease it.

• Diffusion: Movement of solutes from high to low concentration.

• Osmosis: Movement of water across a membrane toward higher solute concentration.

• Isotonic: Equal solute concentration on both sides of membrane.

• Proteins in Membranes: Integral (embedded) and peripheral (attached to surface).

Transport Across Membranes

Transport proteins facilitate movement of molecules across membranes, either passively or actively.

• Channels: Allow specific molecules to move down their concentration gradient.

• Transporters: Move substances with or against gradients; can be very specific.

• Pumps: Use energy (ATP) to move substances against their gradient.

• Example: Sodium-potassium pump moves Na+ out and K+ in, using ATP.

Proteins: Structure and Function

Amino Acids and Protein Structure

Proteins are polymers of amino acids, which have a central carbon, amino group, carboxyl group, and a variable side chain.

• Primary Structure: Sequence of amino acids.

• Secondary Structure: Local folding (alpha helices, beta sheets) stabilized by hydrogen bonds.

• Tertiary Structure: Overall 3D shape, stabilized by various interactions.

• Quaternary Structure: Multiple polypeptide chains assembled together.

Additional info: Hemoglobin's function is affected by its structure; sickle cell disease results from a single amino acid change.

Enzymes and Metabolism

Enzyme Function and Regulation

Enzymes are biological catalysts that speed up chemical reactions by lowering activation energy.

• Activation Energy (): Energy required to start a reaction.

• Gibbs Free Energy (): Determines spontaneity of reactions.

• Enzyme Mechanism: Enzymes bind substrates, facilitate transition state, and release products.

• Cofactors and Coenzymes: Non-protein helpers (vitamins, minerals).

• Competitive Inhibitors: Block active site.

• Allosteric Regulators: Bind elsewhere, change enzyme shape.

• Denaturation: Extreme temperature or pH can disrupt enzyme structure and function.

Key Equations:

• Spontaneous Reaction:

• Nonspontaneous Reaction:

Additional info: Enzymes do not change but lower to increase reaction rate.