Chapter 1: Themes and Methods in Biology

Major Themes of Life

Biology is the study of living organisms and their interactions with each other and their environments. Understanding the major themes of life helps organize biological knowledge.

• Organization: Life is structured in a hierarchy from biosphere → ecosystem → community → population → organism → organ system → organ → tissue → cell → organelle → molecule.

• Information: Living things store, transmit, and respond to information (e.g., DNA, gene expression).

• Energy and Matter: Life requires the transfer and transformation of energy and matter.

• Interactions: Organisms interact with each other and their environment.

• Evolution: The process by which populations change over time through natural selection.

Approaches in Biology

• Scientific Method: A systematic approach to understanding the natural world through observation, hypothesis formation, experimentation, and analysis.

• Controlled Experiment: An experiment in which only one variable is changed at a time, allowing for the isolation of cause and effect.

Chapter 2: Chemistry of Life

Atoms and Elements

All matter is composed of atoms, which are the smallest units of elements. The properties of elements are determined by the number of protons, neutrons, and electrons.

• Atomic Number: The number of protons in an atom, which defines the element.

• Mass Number: The sum of protons and neutrons in the nucleus.

• Electron Shells: Electrons are arranged in shells around the nucleus. The first shell holds up to 2 electrons, the second up to 8, etc.

• Valence Electrons: Electrons in the outermost shell, important for chemical bonding.

Types of Chemical Bonds

• Covalent Bonds: Atoms share electron pairs (e.g., H2, O2).

• Ionic Bonds: Atoms transfer electrons, resulting in charged ions that attract each other (e.g., NaCl).

• Hydrogen Bonds: Weak attractions between a hydrogen atom and an electronegative atom (e.g., between water molecules).

Properties of Water

• Polarity: Water is a polar molecule, with partial positive and negative charges.

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

• High Specific Heat: Water can absorb a lot of heat before changing temperature.

• Evaporative Cooling: As water evaporates, it removes heat from surfaces.

Acids, Bases, and pH

• pH Scale: Measures the concentration of hydrogen ions (H+) in a solution.

• Acid: Substance that increases H+ concentration (pH < 7).

• Base: Substance that decreases H+ concentration (pH > 7).

• Neutral: pH = 7 (pure water).

Chapter 3: Biological Molecules

Isomers

• Isomers: Molecules with the same chemical formula but different structures.

• Types: Structural isomers, cis-trans isomers, enantiomers.

Macromolecules

• Carbohydrates: Energy storage and structural molecules.

  • Monomer: Monosaccharide ("one sugar")

  • Polymer: Polysaccharide ("many sugars")

  • Disaccharide: Two sugars joined together

• Proteins: Diverse functions including catalysis, structure, and transport.

  • Monomer: Amino acid

  • Polymer: Polypeptide

• Nucleic Acids: Store and transmit genetic information.

  • Monomer: Nucleotide

  • Polymer: DNA/RNA polynucleotide

• Lipids: Nonpolar molecules, important for membranes and energy storage.

Linkages and Reactions

• Glycosidic Linkages: Join monosaccharides in carbohydrates.

• Peptide Bonds: Join amino acids in proteins.

• Phosphodiester Bonds: Join nucleotides in nucleic acids.

• Dehydration Reaction: Forms bonds by removing water.

• Hydrolysis: Breaks bonds by adding water.

Protein Structure

• Primary Structure: Sequence of amino acids.

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

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

• Quaternary Structure: Multiple polypeptide chains together.

ATP (Adenosine Triphosphate)

• ATP: Main energy currency of the cell, energy stored in phosphate bonds.

Chapter 4: Cell Structure and Function

Cell Membranes

• Phospholipid Bilayer: Main component of cell membranes, with hydrophilic heads and hydrophobic tails.

• Membrane Proteins: Embedded in the bilayer, involved in transport and signaling.

Cell Organelles and Their Functions

• Ribosomes: Protein synthesis; can be bound (to rough ER) or free (in cytosol).

• Vesicles: Membrane-bound sacs for transport and storage.

• Lysosomes: Contain digestive enzymes to break down waste.

• Peroxisomes: Break down fatty acids and detoxify harmful substances.

• Mitochondria: Site of cellular respiration and ATP production.

• Chloroplasts: Site of photosynthesis in plant cells.

• Nucleus: Contains DNA, controls gene expression.

• Endoplasmic Reticulum (ER):

  • Rough ER: Protein synthesis (with ribosomes attached).

  • Smooth ER: Lipid synthesis, detoxification, calcium storage.

• Golgi Apparatus: Modifies, sorts, and ships proteins and lipids.

• Cytoskeleton: Provides structure, support, and movement.

Protein Transport in Cells

• Proteins synthesized in the rough ER → transported to Golgi apparatus → sorted and shipped to their final destinations (e.g., cell membrane, lysosome, secretion).

• Proteins made by free ribosomes remain in the cytosol.

Endosymbiotic Theory

• Mitochondria and chloroplasts originated from free-living prokaryotes engulfed by ancestral eukaryotic cells.

• Evidence: Both have their own DNA, double membranes, and can reproduce independently within the cell.

Table: Comparison of Prokaryotic and Eukaryotic Cells

Additional info: Some explanations and examples were expanded for clarity and completeness based on standard General Biology curriculum.