General Biology Exam 1 Review: Foundations, Chemistry of Life, and Cell Structure

Chapter 1: Themes and Methods in Biology

Major Themes of Life

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

• Five Categories of Life: Organization, Information, Energy and Matter, Interactions, Evolution.

• Levels of Biological Organization: Biosphere → Ecosystem → Community → Population → Organism → Organ System → Organ → Tissue → Cell → Organelle → Molecule.

Scientific Method

The scientific method is a systematic approach to understanding the natural world through observation, hypothesis formation, experimentation, and analysis.

• Observation: Gathering information about phenomena.

• Hypothesis: A testable explanation for an observation.

• Experiment: A controlled method to test hypotheses.

• Controlled Experiment: An experiment in which only one variable is changed at a time, while all others are kept constant.

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 their atomic structure.

• Atomic Number: Number of protons in an atom; defines the element.

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

• Electron Configuration: Electrons fill shells in a specific order (2 in the first shell, 8 in the second, etc.).

• Valence Electrons: Electrons in the outermost shell; determine chemical reactivity.

Types of Chemical Bonds

Atoms interact to form molecules through chemical bonds, which can be classified by how electrons are shared or transferred.

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

• Ionic Bonds: Electrons are transferred from one atom to another, creating charged ions (e.g., NaCl).

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

Properties of Water

Water's unique properties are essential for life and result from its polarity and ability to form hydrogen bonds.

• Cohesion: Water molecules stick together via hydrogen bonds.

• Adhesion: Water molecules stick to other substances.

• High Specific Heat: Water resists temperature changes.

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

Acids, Bases, and pH

The 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 (e.g., pure water).

Formula:

$\text{pH} = -\log_{10}[\text{H}^+]$

Chapter 3: Biological Molecules

Isomers

Isomers are molecules with the same molecular formula but different structures, resulting in different properties.

• Structural Isomers: Differ in covalent arrangement of atoms.

• Cis-Trans Isomers: Differ in spatial arrangement around double bonds.

• Enantiomers: Mirror images of each other; important in biological activity.

Macromolecules: Structure and Function

Living organisms are composed of four major classes of macromolecules: carbohydrates, proteins, nucleic acids, and lipids.

• Carbohydrates: Energy storage and structural support.

  • Monomer: Monosaccharides (e.g., glucose)

  • Polymer: Polysaccharides (e.g., starch, cellulose)

• Proteins: Catalyze reactions, structural support, transport, etc.

  • Monomer: Amino acids

  • Polymer: Polypeptides

• Nucleic Acids: Store and transmit genetic information.

  • Monomer: Nucleotides

  • Polymer: DNA/RNA polynucleotides

• Lipids: Energy storage, membrane structure, signaling (not true polymers).

Table: Macromolecule Monomers and Polymers

Macromolecule	Monomer	Polymer
Carbohydrates	Monosaccharide	Polysaccharide
Proteins	Amino Acid	Polypeptide
Nucleic Acids	Nucleotide	Polynucleotide (DNA/RNA)
Lipids	Glycerol, Fatty Acids	Triglyceride (not a true polymer)

Protein Structure

Proteins have four levels of structure that determine their function.

• 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.

ATP: The Energy Currency

ATP (adenosine triphosphate) stores and transfers energy within cells, primarily through the transfer of phosphate groups.

Chapter 4: Cell Structure and Function

Cell Membranes

Cell membranes are composed of a phospholipid bilayer with embedded proteins, providing a barrier and mediating transport.

• Phospholipids: Have hydrophilic heads and hydrophobic tails, forming bilayers in water.

• Membrane Proteins: Facilitate transport, signaling, and structural support.

Cell Organelles and Their Functions

Organelles are specialized structures within cells that perform distinct functions.

• Ribosomes: Protein synthesis (translation of mRNA to amino acids).

  • Bound Ribosomes: Attached to rough ER; synthesize proteins for export or membranes.

  • Free Ribosomes: Float in cytosol; synthesize proteins for use within the cell.

• Vacuoles: Storage and transport; larger in plant cells.

• Vesicles: Transport materials within the cell.

• Lysosomes: Contain digestive enzymes; break down waste and cellular debris.

• 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).

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

• Golgi Apparatus: Modifies, sorts, and packages proteins and lipids for transport.

• Cytoskeleton: Provides structural support and mediates cell movement.

Protein Synthesis and Trafficking

Proteins are synthesized in ribosomes and may be exported from the cell or used internally.

• Pathway for Exported Proteins: DNA → mRNA → Ribosome (on Rough ER) → Golgi Apparatus → Vesicle → Cell Membrane (exocytosis).

• Proteins for Cytosol: DNA → mRNA → Free Ribosome → Cytosol.

Endosymbiotic Theory

The endosymbiotic theory explains the origin of mitochondria and chloroplasts as formerly free-living prokaryotes that were engulfed by ancestral eukaryotic cells.

• Both organelles have their own DNA and ribosomes.

• They can grow and reproduce independently within the cell.