General Biology: Core Concepts, Macromolecules, and Experimental Design

Unit 1: Levels of Organization and Scientific Method

Levels of Organization in Biology

The biological world is organized into a hierarchy, from the smallest chemical units to the entire biosphere. Understanding these levels helps explain how life is structured and functions at different scales.

• Atom: The basic unit of matter, consisting of protons, neutrons, and electrons.

• Molecule: Two or more atoms bonded together (e.g., H2O).

• Organelle: Specialized structures within cells (e.g., mitochondria).

• Cell: The basic unit of life; can be prokaryotic or eukaryotic.

• Tissue: Groups of similar cells performing a specific function.

• Organ: Structures composed of different tissues working together (e.g., heart).

• Organ System: Groups of organs that perform related functions (e.g., digestive system).

• Organism: An individual living thing.

• Population: All individuals of a species in a given area.

• Community: All populations of different species in an area.

• Ecosystem: The community plus the nonliving environment.

• Biosphere: All ecosystems on Earth.

Example: A forest ecosystem includes trees (organisms), populations of deer, communities of plants and animals, and the soil and climate (ecosystem).

Scientific Method and Experimental Design

The scientific method is a systematic approach to investigating natural phenomena. It involves making observations, forming hypotheses, conducting experiments, and drawing conclusions.

• Observation: Gathering information about a phenomenon.

• Hypothesis: A testable explanation for an observation.

• Experiment: A controlled test to evaluate the hypothesis.

• Independent Variable: The factor that is changed or manipulated.

• Dependent Variable: The factor that is measured or observed.

• Control Group: The group that does not receive the experimental treatment.

• Statistical Significance: A measure of whether results are likely due to chance.

Example: Testing the effect of a new drug on blood pressure, with one group receiving the drug (experimental) and another receiving a placebo (control).

Unit 2: Basic Chemistry for Biology

Atoms, Ions, and Molecules

All matter is composed of atoms, which combine to form molecules. Understanding atomic structure is fundamental to biology.

• Atom: Consists of a nucleus (protons and neutrons) and electrons in orbitals.

• Isotope: Atoms of the same element with different numbers of neutrons.

• Ion: An atom or molecule with a net electric charge due to loss or gain of electrons.

• Molecule: Two or more atoms held together by covalent bonds.

Example: Sodium (Na) loses an electron to become Na+; chlorine (Cl) gains an electron to become Cl-.

Chemical Bonds

Chemical bonds hold atoms together in molecules and compounds. The main types are covalent, ionic, and hydrogen bonds.

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

• Ionic Bond: Transfer of electrons from one atom to another (e.g., NaCl).

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

Example: Water molecules are held together by hydrogen bonds, giving water its unique properties.

pH, Acids, and Bases

The pH scale measures the concentration of hydrogen ions (H+) in a solution, indicating its acidity or basicity.

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

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

• Buffer: Substance that minimizes changes in pH.

Equation:

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

Example: Stomach acid has a low pH (highly acidic), while blood is slightly basic (pH ~7.4).

Unit 3: Biological Macromolecules

Organic Molecules and Functional Groups

Organic molecules are carbon-based compounds found in living organisms. Functional groups are specific groups of atoms that confer particular properties to molecules.

• Hydroxyl Group (-OH): Found in alcohols.

• Carboxyl Group (-COOH): Found in acids.

• Amino Group (-NH2): Found in amino acids.

• Phosphate Group (-PO4): Found in nucleic acids.

Example: Glucose contains hydroxyl groups; amino acids contain both amino and carboxyl groups.

Macromolecules: Types and Functions

There are four major classes of biological macromolecules: carbohydrates, lipids, proteins, and nucleic acids. Each has distinct structures and functions.

• Carbohydrates: Sugars and starches; provide energy and structural support.

• Lipids: Fats, oils, and phospholipids; store energy and form cell membranes.

• Proteins: Polymers of amino acids; perform a wide range of functions including catalysis (enzymes), structure, and transport.

• Nucleic Acids: DNA and RNA; store and transmit genetic information.

Example: Starch (a carbohydrate) stores energy in plants; hemoglobin (a protein) transports oxygen in blood.

Carbohydrates

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

• Disaccharides: Two monosaccharides joined (e.g., sucrose).

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

Condensation (Dehydration) Reaction: Joins monomers by removing water.

Hydrolysis: Breaks polymers into monomers by adding water.

Equation:

$\text{Monomer}_1 + \text{Monomer}_2 \xrightarrow{\text{condensation}} \text{Polymer} + \text{H}_2\text{O}$

$\text{Polymer} + \text{H}_2\text{O} \xrightarrow{\text{hydrolysis}} \text{Monomer}_1 + \text{Monomer}_2$

Lipids

Lipids are hydrophobic molecules, including fats, oils, and phospholipids. They are important for energy storage, insulation, and membrane structure.

• Triglyceride: Composed of one glycerol and three fatty acids.

• Phospholipid: Composed of a glycerol, two fatty acids, and a phosphate group; forms cell membranes.

• Saturated Fatty Acid: No double bonds; solid at room temperature.

• Unsaturated Fatty Acid: One or more double bonds; liquid at room temperature.

Example: Butter contains saturated fats; olive oil contains unsaturated fats.

Triglyceride Structure

A triglyceride is formed by joining three fatty acids to a glycerol molecule via condensation reactions (also called dehydration synthesis).

Diagram: (See provided image for structure)

• Chemical Property: All lipids are hydrophobic (insoluble in water).

• Formation: Three fatty acids + one glycerol → triglyceride + 3 H2O (via condensation).

• Phospholipid Difference: Phospholipids have two fatty acids and a phosphate group, making them amphipathic (hydrophilic head, hydrophobic tails).

Proteins

Proteins are polymers of amino acids linked by peptide bonds. Their structure determines their function.

• Primary Structure: Sequence of amino acids.

• Secondary Structure: Local folding (α-helix, β-sheet).

• Tertiary Structure: Overall 3D shape.

• Quaternary Structure: Association of multiple polypeptide chains.

Example: Enzymes are proteins that catalyze biochemical reactions.

Nucleic Acids

Nucleic acids store and transmit genetic information. DNA and RNA are polymers of nucleotides.

• DNA: Double helix; stores genetic information.

• RNA: Single-stranded; involved in protein synthesis.

• Nucleotide: Monomer consisting of a sugar, phosphate, and nitrogenous base.

Example: ATP (adenosine triphosphate) is a nucleotide that stores energy.

Experimental Data and Analysis

Data Interpretation Example: Slug Distribution

Analyzing data involves identifying patterns, variables, and drawing conclusions based on evidence.

Time of Day	Average Distance Between Individuals (cm)
Midnight	8.0
4 A.M.	8.9
8 A.M.	44.8
NOON	174.0
4 P.M.	350.5
8 P.M.	60.5
Midnight	8.0

• Pattern: Slugs are closer together at night and farther apart during the day.

• Variables: Physiological (e.g., activity cycles) and environmental (e.g., temperature, humidity).

• Controlled Experiment: Manipulate one variable (e.g., light exposure) to test its effect on slug distribution.

Water: Structure and Properties

Structure of Water

Water (H2O) is a polar molecule with unique properties essential for life.

• Polarity: Oxygen is more electronegative, creating partial charges.

• Hydrogen Bonding: Water molecules form hydrogen bonds with each other.

Equation:

$\text{H}_2\text{O} + \text{H}_2\text{O} \rightarrow$ hydrogen bonding

• Cohesion: Water molecules stick together.

• Adhesion: Water molecules stick to other substances.

• High Specific Heat: Water resists temperature changes.

• Solvent Properties: Water dissolves many substances.

Example: Water's high heat capacity helps regulate Earth's climate.

Enzymes and Biological Catalysis

Enzyme Structure and Function

Enzymes are proteins that speed up chemical reactions by lowering activation energy. They are specific to substrates and can be affected by environmental conditions.

• Active Site: Region where substrate binds.

• Substrate: The molecule upon which an enzyme acts.

• Denaturation: Loss of enzyme structure and function due to extreme conditions (e.g., pH, temperature).

Example: Bromelain is an enzyme in pineapple that breaks down proteins, used to tenderize meat.

Enzyme Activity and pH

• Optimal pH: Each enzyme works best at a specific pH.

• Effect of pH: Extreme pH can denature enzymes, reducing activity.

Example: Bromelain is most active at pH 3.5–5.1; activity decreases at pH 11.

Summary Table: Macromolecules and Their Monomers

Macromolecule	Monomer	Function
Carbohydrate	Monosaccharide	Energy, structure
Lipid	Glycerol + Fatty Acids	Energy storage, membranes
Protein	Amino Acid	Catalysis, structure, transport
Nucleic Acid	Nucleotide	Genetic information

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