Chapter 1: Evolution, Matter, and Energy in Biology

Transfer and Transformation of Matter and Energy

Biological systems rely on the transfer and transformation of matter and energy to sustain life. These processes are fundamental to metabolism, growth, and reproduction.

• Matter refers to anything that has mass and occupies space; in biology, it includes atoms and molecules that make up living organisms.

• Energy is the capacity to do work or cause change, such as chemical, thermal, or kinetic energy.

• Example: Photosynthesis transforms light energy into chemical energy stored in glucose.

Natural Selection and Evolution

Natural selection is a process by which populations adapt to their environment over generations, leading to evolution.

• For natural selection to occur, there must be variation in traits, heredity (traits passed to offspring), and differential survival/reproduction.

• Example: Peppered moths in industrial England—darker moths survived better in polluted areas, leading to an increase in dark-colored moths.

Hypotheses, Theories, and Scientific Experiments

• Hypothesis: A testable, falsifiable statement explaining an observation.

• Theory: A well-substantiated explanation of some aspect of the natural world, based on a body of evidence.

• Experiment: A controlled method to test hypotheses. Variables: Independent (manipulated), dependent (measured), and controlled (kept constant).

• Example: Testing the effect of sunlight on plant growth by varying light exposure (independent variable) and measuring plant height (dependent variable).

Chapter 2: The Chemical Context of Life

Elements, Atoms, and Compounds

All matter is composed of elements, which are substances that cannot be broken down by chemical means. Atoms are the smallest units of elements, and compounds are substances formed from two or more elements in fixed ratios.

• Major elements in biology: Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N), Phosphorus (P), Sulfur (S).

• Subatomic particles: Protons (positive charge), neutrons (neutral), electrons (negative charge).

• Valence electrons are electrons in the outermost shell, determining chemical reactivity.

Covalent and Ionic Bonds

• Covalent bonds: Atoms share electrons; can be polar (unequal sharing) or non-polar (equal sharing).

• Ionic bonds: Electrons are transferred from one atom to another, creating charged ions.

• Hydrogen bonds: Weak attractions between a hydrogen atom and an electronegative atom (e.g., O or N).

• Example: Water molecules are held together by hydrogen bonds.

Chemical Reactions and Equilibrium

• Chemical reaction: Process where reactants are transformed into products.

• Reactants are starting materials; products are the result.

• Chemical equilibrium: The point at which the rate of the forward reaction equals the rate of the reverse reaction.

• Example equation:

Chapter 3: Water and Life

Properties of Water

Water is essential for life due to its unique chemical and physical properties.

• Polarity: Water is a polar molecule, leading to hydrogen bonding.

• Cohesion and adhesion: Water molecules stick to each other (cohesion) and to other substances (adhesion).

• High specific heat: Water resists temperature changes.

• Solvent properties: Water dissolves many substances, making it the "universal solvent."

• Density: Ice is less dense than liquid water, so it floats.

pH and Acids/Bases

• pH scale: Measures hydrogen ion concentration; ranges from 0 (acidic) to 14 (basic), with 7 as neutral.

• Acid: Substance that increases H+ concentration.

• Base: Substance that decreases H+ concentration.

• Buffer: Substance that minimizes changes in pH.

• Example: Blood contains buffers to maintain pH near 7.4.

Chapter 4: Carbon and the Molecular Diversity of Life

Organic Molecules and Functional Groups

Organic molecules are carbon-based compounds that form the basis of life. Functional groups are specific groups of atoms within molecules that determine their chemical properties.

• Requirement for organic: Must contain carbon, often bonded to hydrogen, oxygen, or nitrogen.

• Functional groups: Hydroxyl (-OH), carboxyl (-COOH), amino (-NH2), phosphate (-PO4), methyl (-CH3), etc.

• Example: Amino acids contain both amino and carboxyl groups.

Macromolecules: Carbohydrates, Proteins, Nucleic Acids

Macromolecules are large, complex molecules essential for life. They are typically polymers made from repeating monomer units.

Carbohydrates

• Monomers: Monosaccharides (e.g., glucose, fructose).

• Dimers: Disaccharides (e.g., sucrose, lactose).

• Polymers: Polysaccharides (e.g., starch, glycogen, cellulose).

• Functions: Energy storage, structural support.

Proteins

• Monomers: Amino acids.

• Polymers: Polypeptides/proteins.

• Functions: Enzymes, structural support, transport, signaling, defense.

• Protein structure:

  • Primary: Sequence of amino acids.

  • Secondary: Alpha helices and beta sheets (hydrogen bonding).

  • Tertiary: 3D folding due to side chain interactions.

  • Quaternary: Association of multiple polypeptide chains.

Nucleic Acids

• Monomers: Nucleotides (adenine, thymine, cytosine, guanine, uracil).

• Polymers: DNA and RNA.

• Functions: Storage and transmission of genetic information.

• Differences between DNA and RNA:

  • DNA contains deoxyribose; RNA contains ribose.

  • DNA is double-stranded; RNA is single-stranded.

  • DNA uses thymine; RNA uses uracil.

Table: Monomers, Dimers, and Polymers of Biological Macromolecules

Additional info:

• Some context and definitions were expanded for clarity and completeness.

• Examples and explanations were added to ensure the notes are self-contained and suitable for exam preparation.