Unit 1: Foundations of Biology

Levels of Organization

Biology studies life at multiple levels, from the smallest atoms to the largest biospheres. Understanding these levels helps explain how complex systems arise from simpler components.

• Atom: The basic unit of matter.

• Molecule: Two or more atoms bonded together.

• Organelle: Specialized structures within cells.

• Cell: The basic unit of life.

• Tissue: Groups of similar cells performing a function.

• Organ: Structures composed of tissues working together.

• Organ System: Groups of organs performing complex functions.

• Organism: An individual living thing.

• Population: Group of organisms of the same species.

• Community: Different populations living together.

• Ecosystem: Community plus its nonliving environment.

• Biosphere: All ecosystems on Earth.

Example: Humans are organisms made of organ systems, which are made of organs, tissues, and cells.

Energy Flow and Nutrient Cycling

Energy flows through ecosystems via food chains and food webs, while nutrients cycle through biotic and abiotic components.

• Producers (Autotrophs): Make their own food (e.g., plants).

• Consumers (Heterotrophs): Eat other organisms.

• Decomposers: Break down dead matter, recycling nutrients.

Example: Sunlight is captured by plants, transferred to herbivores, then to carnivores, and finally decomposed by fungi and bacteria.

Homeostasis

Homeostasis is the ability of organisms to maintain stable internal conditions despite external changes.

• Key Point: Homeostasis is essential for survival and function.

• Example: Human body temperature regulation.

Domains of Life

All living organisms are classified into three domains based on cellular characteristics.

• Bacteria: Prokaryotic, unicellular organisms.

• Archaea: Prokaryotic, often found in extreme environments.

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

Scientific Method and Experimental Design

The scientific method is a systematic approach to investigation. Experiments use variables to test hypotheses.

• Independent Variable: The factor changed by the experimenter.

• Dependent Variable: The factor measured in response.

• Control Group: The group not exposed to the independent variable.

• Statistical Significance: Indicates whether results are likely due to chance.

Example: Testing the effect of light on plant growth.

Unit 2: Basic Chemistry for Biology

Atoms, Ions, and Isotopes

Atoms are the building blocks of matter, composed of protons, neutrons, and electrons.

• Proton: Positively charged particle in the nucleus.

• Neutron: Neutral particle in the nucleus.

• Electron: Negatively charged particle orbiting the nucleus.

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

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

Example: Carbon-14 is an isotope of carbon used in radiometric dating.

Chemical Bonds

Atoms form bonds to achieve stability. The main types are ionic, covalent, and hydrogen bonds.

• Ionic Bond: Transfer of electrons from one atom to another.

• Covalent Bond: Sharing of electrons between atoms.

• Polar Covalent Bond: Unequal sharing of electrons, leading to partial charges.

• Hydrogen Bond: Weak attraction between a hydrogen atom and another electronegative atom.

Example: Water molecules are held together by hydrogen bonds.

Water: Properties and Importance

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

• Polarity: Water is a polar molecule, allowing it to dissolve many substances.

• Cohesion: Water molecules stick to each other.

• Adhesion: Water molecules stick to other surfaces.

• High Specific Heat: Water resists temperature changes.

• Solvent: Water dissolves ions and polar molecules.

• pH: Measure of hydrogen ion concentration; water is neutral at pH 7.

Equation:

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

Acids, Bases, and Buffers

Acids and bases affect pH, while buffers help maintain stable pH in biological systems.

• Acid: Substance that increases hydrogen ion concentration.

• Base: Substance that decreases hydrogen ion concentration.

• Buffer: Solution that resists changes in pH.

Example: Blood contains buffers to maintain pH around 7.4.

Unit 3: Biological Macromolecules

Organic Molecules and Functional Groups

Organic molecules contain carbon and are the basis of life. Functional groups determine their properties.

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

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

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

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

Macromolecules: Structure and Function

Macromolecules are large molecules essential for life, formed by polymerization of smaller units.

• Carbohydrates: Provide energy and structural support.

• Lipids: Store energy, form membranes, and act as signaling molecules.

• Proteins: Perform a wide range of functions, including catalysis, transport, and structure.

• Nucleic Acids: Store and transmit genetic information.

Carbohydrates

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

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

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

Equation:

Example: Glycogen stores energy in animals; starch stores energy in plants.

Lipids

• Triglycerides: Composed of glycerol and three fatty acids.

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

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

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

Example: Phospholipids form the bilayer of cell membranes.

Proteins

• Amino Acids: Building blocks of proteins; contain amino and carboxyl groups.

• Peptide Bond: Covalent bond between amino acids.

• Primary Structure: Sequence of amino acids.

• Secondary Structure: Alpha helices and beta sheets formed by hydrogen bonding.

• Tertiary Structure: Overall 3D shape of a polypeptide.

• Quaternary Structure: Association of multiple polypeptide chains.

Equation:

Example: Hemoglobin is a protein with quaternary structure.

Nucleic Acids

• DNA: Stores genetic information.

• RNA: Involved in protein synthesis.

• Nucleotide: Monomer of nucleic acids; consists of a sugar, phosphate, and nitrogenous base.

Example: ATP is a nucleotide that stores energy.

Experimental Design and Data Analysis

Variables and Controls

Experiments require careful control of variables to ensure valid results.

• Independent Variable: Manipulated by the experimenter.

• Dependent Variable: Measured outcome.

• Control Group: Used for comparison.

Statistical Significance

Statistical analysis determines whether observed differences are likely due to chance.

• Key Point: Results are statistically significant if the probability of them occurring by chance is low.

Example Table: Distribution of Slugs

The following table shows the average distance between slugs at different times of day, illustrating how environmental variables can affect animal behavior.

Additional info: This table can be used to discuss patterns, variables, and experimental design in ecology.

Enzymes and Biological Catalysts

Enzyme Structure and Function

Enzymes are proteins that speed up chemical reactions by lowering activation energy.

• Active Site: Region where substrate binds.

• Substrate: Molecule upon which an enzyme acts.

• Denaturation: Loss of enzyme structure and function due to changes in pH or temperature.

Example: Bromelain in pineapple breaks down proteins, affecting browning in fruits.

Effect of pH and Temperature on Enzymes

Enzyme activity is sensitive to environmental conditions.

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

• Optimal Temperature: Enzyme activity increases with temperature up to a point, then decreases due to denaturation.

Example: Bromelain is less effective at low pH (e.g., pH 1).

Macromolecule Structure: Lipids Example

Triglyceride Structure

Triglycerides are a type of lipid formed by condensation reactions between glycerol and three fatty acids.

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

• Formation: Triglyceride is formed from four molecules (one glycerol, three fatty acids).

• Phospholipids: Differ from triglycerides by having a phosphate group instead of a third fatty acid; form cell membranes.

Equation:

Example: Phospholipids are amphipathic, with hydrophilic heads and hydrophobic tails.

Protein Structure

Levels of Protein Structure

Proteins have four levels of structure that determine their function.

• Primary Structure: Sequence of amino acids.

• Secondary Structure: Alpha helices and beta sheets.

• Tertiary Structure: 3D folding due to interactions among R groups.

• Quaternary Structure: Multiple polypeptide chains assembled together.

Additional info: The function of a protein is determined by its shape, which is influenced by the sequence and chemical properties of its amino acids.