Chapter 1: Introduction to Biology

Characteristics of Life

Biology is the scientific study of life. All living organisms, despite their diversity, share several defining characteristics:

• Cellular Organization: Composed of one or more cells.

• Energy Utilization: Obtain and use energy.

• Response to Stimuli: React to environmental changes.

• Homeostasis: Maintain a relatively stable internal environment.

• Reproduction: Produce offspring.

• Growth and Development: Increase in size and complexity.

• Evolution: Populations change over generations.

Homeostasis is the regulation of internal conditions within certain limits, despite external changes. For example, humans sweat to cool down or shiver to warm up.

Levels of Biological Organization

Life is organized hierarchically from the simplest to the most complex structures:

• Molecule → Organelle → Cell → Tissue → Organ → Organ System → Organism → Population → Community → Ecosystem

Example: Muscle tissue (tissue) is made of muscle cells (cells), which contain mitochondria (organelles).

Scientific Method

The scientific method is a systematic approach to understanding natural phenomena:

1. Observation: Gathering information using senses.

2. Hypothesis: A testable, falsifiable explanation for observations.

3. Experiment: Testing the hypothesis with controlled variables.

4. Analysis and Conclusion: Interpreting results to support or refute the hypothesis.

Controlled Experiments involve an experimental group (receives treatment) and a control group (no treatment) to compare outcomes.

Evolution and Natural Selection

Evolution is the change in populations over time, explaining both the diversity and unity of life. Natural selection is the process where individuals with advantageous traits reproduce more successfully, leading to adaptation.

• Adaptation: Inherited trait that increases survival or reproduction.

• Example: Antibiotic resistance in bacteria arises as resistant individuals survive and reproduce.

Common Misconceptions: Individuals do not evolve; populations do. Evolution is not purposeful.

Ecosystems and Energy Flow

An ecosystem includes all living organisms and their nonliving environment. Energy flows one-way (sunlight → producers → consumers → heat), while matter cycles (e.g., carbon, nitrogen, water cycles).

• Producers: Convert sunlight to chemical energy (e.g., plants).

• Consumers: Obtain energy by eating other organisms (e.g., animals).

• Decomposers: Break down dead matter, recycling nutrients (e.g., fungi, bacteria).

Domains of Life

All life is classified into three domains:

• Bacteria: Prokaryotic, diverse environments.

• Archaea: Prokaryotic, often in extreme environments.

• Eukarya: Eukaryotic; includes animals, plants, fungi, protists.

Chapter 2: Chemistry of Life

Atoms and Elements

All matter is composed of atoms, which consist of:

• Protons: Positive charge, in nucleus.

• Neutrons: No charge, in nucleus.

• Electrons: Negative charge, orbit nucleus.

Atomic number = number of protons. CHNOPS (Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, Sulfur) are the main elements in living things. Trace elements (e.g., zinc, iron) are needed in small amounts.

Isotopes and Ions

• Isotopes: Atoms of the same element with different numbers of neutrons (e.g., Carbon-12 vs Carbon-14).

• Radioactive isotopes: Unstable, decay over time.

Electron Shells and Chemical Bonds

Electrons occupy shells; the outermost shell contains valence electrons that determine chemical reactivity.

• Covalent bonds: Atoms share electrons (e.g., H2O).

• Nonpolar covalent: Electrons shared equally (e.g., C-H bonds).

• Polar covalent: Electrons shared unequally (e.g., O-H in water).

• Hydrogen bonds: Weak attractions between polar molecules (e.g., between water molecules).

• Ionic bonds: Electrons transferred; forms ions (e.g., Na+ and Cl- in NaCl).

Compounds and Chemical Reactions

A compound contains two or more elements in fixed ratios (e.g., H2O, CO2). Chemical reactions rearrange atoms; reactants → products.

Acids, Bases, and Buffers

• Acids: Increase H+ concentration, lower pH.

• Bases: Increase OH- concentration, raise pH.

• Buffers: Resist pH changes, maintain homeostasis.

Ocean acidification occurs when CO2 dissolves in water, forming carbonic acid and lowering pH.

Chapter 3: Biomolecules

Major Classes of Biomolecules

All living things are composed of four main types of carbon-based biomolecules:

• Carbohydrates

• Lipids

• Proteins

• Nucleic Acids

Many biomolecules are polymers made from repeating monomers:

Carbohydrates

• Monosaccharides: Simple sugars (e.g., glucose, fructose).

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

• Functions: Energy source, storage, structural support.

Starch: Energy storage in plants; digestible by humans. Cellulose: Structural in plants; indigestible by most animals.

Lipids

• Functions: Long-term energy storage, insulation, hormones, cell membranes.

• Types: Fats, oils, phospholipids, steroids.

• Phospholipids: Main component of cell membranes; hydrophilic head, hydrophobic tails.

• Saturated fats: Solid at room temperature, animal sources.

• Unsaturated fats: Liquid at room temperature, plant sources.

• Trans fats: Artificial, increase heart disease risk.

Proteins

• Functions: Structure, transport, movement, signaling, enzymes.

• Monomer: Amino acid (contains amino group -NH2, carboxyl group -COOH, R-group).

• Peptide bonds: Link amino acids (amino group to carboxyl group).

• Enzymes: Proteins that catalyze reactions, lower activation energy, not consumed.

Dehydration and Hydrolysis Reactions

• Dehydration: Builds polymers by removing water.

• Hydrolysis: Breaks polymers by adding water.

Chapter 4: Cell Structure and Function

Cell Theory

1. All living things are composed of cells.

2. The cell is the basic unit of life.

3. All cells arise from preexisting cells.

Prokaryotic vs Eukaryotic Cells

Cellular Components and Functions

• Ribosomes: Protein synthesis (free or on rough ER).

• mRNA: Carries genetic code from DNA to ribosomes.

• Endomembrane system: Nuclear envelope, ER, Golgi, lysosomes, vesicles.

• Rough ER: Protein production and processing.

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

• Golgi apparatus: Modifies, sorts, packages proteins.

• Lysosomes: Digestive enzymes, breakdown/recycling.

• Peroxisomes: Breakdown of harmful substances.

• Mitochondria: Cellular respiration, ATP production.

• Chloroplasts: Photosynthesis (plants, algae).

• Cytoskeleton: Cell shape, movement, organelle transport.

• Intermediate filaments: Structural support.

Cell Junctions

• Tight junctions: Prevent leakage.

• Gap junctions: Allow communication.

• Anchoring junctions: Hold cells together (e.g., skin).

Chapter 5: Membrane Structure and Function

Plasma Membrane and Fluid Mosaic Model

The plasma membrane is a selectively permeable barrier composed of a phospholipid bilayer with embedded proteins, cholesterol, and carbohydrates. The Fluid Mosaic Model describes its dynamic and diverse structure.

• Functions: Controls entry/exit, communication, protection, homeostasis.

Membrane Proteins and Cell Signaling

• Transport proteins: Move substances across membrane.

• Receptor proteins: Receive signals and trigger responses.

• Enzymes: Catalyze reactions.

• Recognition proteins: Cell identity.

• Attachment proteins: Connect cells or cytoskeleton.

Transport Mechanisms

• Passive transport: No energy required; substances move down concentration gradient.

• Diffusion: Movement from high to low concentration.

• Osmosis: Diffusion of water across a membrane.

• Tonicity: Isotonic (no net water movement), hypotonic (cell swells), hypertonic (cell shrinks).

• Facilitated diffusion: Uses transport proteins; no energy required.

• Active transport: Requires energy (usually ATP); moves substances against gradient.

ATP and Enzymes

• ATP (Adenosine Triphosphate): Main energy currency; energy released when terminal phosphate is removed.

• Enzymes: Lower activation energy, speed up reactions, remain unchanged.

Aquaporins and Feedback Inhibition

• Aquaporins: Channel proteins for water transport; defects cause excessive urine production.

• Feedback inhibition: End product inhibits earlier pathway step to regulate processes.

Chapter 6: Cellular Respiration

Overview and Equation

Cellular respiration converts glucose and oxygen into ATP, carbon dioxide, and water:

Stages of Cellular Respiration

1. Glycolysis: In cytoplasm; splits glucose into pyruvate, produces ATP and NADH.

2. Pyruvate Oxidation: Converts pyruvate to acetyl-CoA.

3. Citric Acid Cycle (Krebs Cycle): In mitochondrial matrix; releases CO2, produces NADH, FADH2, ATP.

4. Electron Transport Chain: In inner mitochondrial membrane; uses NADH/FADH2 to produce most ATP; O2 is final electron acceptor, forms water.

Key Molecules and Structures

• NADH: Electron carrier; transports electrons to electron transport chain.

• ATP: Main energy product.

• Cristae: Folds in inner mitochondrial membrane; increase surface area for ATP production.

Aerobic vs Anaerobic Respiration

• Aerobic: Requires oxygen; high ATP yield.

• Anaerobic (Fermentation): No oxygen; low ATP yield; e.g., yeast produce ethanol and CO2.

Brown Fat and Thermogenesis

Brown fat contains many mitochondria with proteins that generate heat instead of ATP, aiding in temperature regulation.

Summary Pathway

Glucose → Glycolysis → Pyruvate → Acetyl-CoA → Citric Acid Cycle → NADH/FADH2 → Electron Transport Chain → ATP

Additional info:

• Be able to identify where each step of cellular respiration occurs within the cell.

• Understand the difference between oxidation (loss of electrons) and reduction (gain of electrons).