General Biology: Unity, Diversity, Scientific Method, Chemistry of Life, and Macromolecules

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Chapter 1: Unity and Diversity of Life

What is Biology?

Biology is the scientific study of life and living organisms, encompassing their structure, function, growth, evolution, distribution, and taxonomy.

Key Point: Biology investigates the mechanisms underlying life processes and the interactions among organisms and their environments.
Example: Studying how plants convert sunlight into energy through photosynthesis.

Classification of Organisms and Taxonomy

Taxonomy is the science of naming, describing, and classifying organisms into groups based on shared characteristics.

Key Point: Organisms are classified using a hierarchical system: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.
Example: Homo sapiens is the binomial name for modern humans.

Binomial Classification

Binomial nomenclature assigns each species a two-part scientific name: genus and species.

Key Point: The correct binomial classification for humans is Homo sapiens.
Example: Canis lupus is the scientific name for the gray wolf.

Domains of Life: Prokaryotes vs. Eukaryotes

Life is divided into three domains: Bacteria, Archaea (both prokaryotic), and Eukarya (eukaryotic).

Key Point: Prokaryotes lack a nucleus and membrane-bound organelles; eukaryotes possess both.
Example: Bacteria are prokaryotes; plants and animals are eukaryotes.

Eukaryotic Kingdoms and Additional Group

The three eukaryotic kingdoms are Plantae, Animalia, and Fungi. Protists are an additional, diverse group.

Key Point: Each kingdom is defined by unique modes of nutrition and cellular organization.

Chapter 1: The Scientific Method

Steps of the Scientific Method

The scientific method is a systematic approach to investigation.

Step 1: Observation – Noticing phenomena.
Step 2: Question – Formulating a question about the observation.
Step 3: Hypothesis – Proposing a testable explanation.
Step 4: Experiment – Testing the hypothesis.
Step 5: Data Collection – Gathering and analyzing results.
Step 6: Conclusion – Interpreting data to support or refute the hypothesis.

Experimental Variables, Control Group, and Experimental Group

Variables are factors that can change in an experiment.

Independent Variable: The factor manipulated by the experimenter.
Dependent Variable: The factor measured in response.
Control Group: The group not exposed to the independent variable; used for comparison.
Experimental Group: The group exposed to the independent variable.

Hypothesis and Theory in Science

A hypothesis is a testable statement; a theory is a well-substantiated explanation based on evidence.

Key Point: Hypotheses are specific and testable; theories are broad and supported by multiple lines of evidence.

Chapter 2: Chemistry of Life

Periodic Table and Atomic Structure

The periodic table organizes elements by atomic number and properties.

Key Point: Atomic number equals the number of protons; mass number equals protons plus neutrons.
Example: Carbon has atomic number 6.

Electron Shells and Distribution

Electrons occupy energy levels (shells) around the nucleus.

Key Point: The first shell holds up to 2 electrons, the second and third up to 8 each.

Covalent Bonds: Polar vs. Nonpolar

Covalent bonds involve sharing electrons between atoms.

Polar Covalent Bond: Unequal sharing of electrons (e.g., in water).
Nonpolar Covalent Bond: Equal sharing of electrons (e.g., in oxygen gas).

Electronegativity

Electronegativity is an atom's ability to attract electrons in a bond.

Key Point: Differences in electronegativity determine bond polarity.

Ions, Cations, and Anions; Ionic Bonds

Ions are charged atoms or molecules; cations are positive, anions are negative.

Ionic Bond: Attraction between oppositely charged ions.
Example: Sodium chloride (NaCl).

Covalent vs. Ionic Bonds

Covalent bonds share electrons; ionic bonds transfer electrons.

Key Point: Covalent bonds are generally stronger and found in organic molecules.

Hydrogen Bonds

Hydrogen bonds are weak attractions between a hydrogen atom and an electronegative atom (e.g., oxygen or nitrogen).

Key Point: Hydrogen bonds are crucial for the structure of water and biological macromolecules.

Structure and Function in Molecules

The study of structure and function explains how molecular shape affects biological activity.

Example: Enzyme active sites are shaped to fit specific substrates.

Properties of Water

Water has four main properties essential for life:

Cohesion: Water molecules stick together.
Adhesion: Water molecules stick to other surfaces.
High Specific Heat: Water resists temperature change.
Solvent Ability: Water dissolves many substances.

Unique Characteristics of Water

Hydrogen bonding gives water its unique properties, such as high surface tension and the ability to moderate temperature.

pH and Measurement of Concentration

pH measures the concentration of hydrogen ions () in a solution.

Equation:
Key Point: Low pH = acidic; high pH = basic.

pH Scale and Solutions

The pH scale ranges from 0 (acidic) to 14 (basic).

Key Point: Each unit change in pH represents a tenfold change in .

Buffers

Buffers stabilize pH in biological systems by absorbing excess or ions.

Example: Bicarbonate buffer system in blood.

Chapter 3: Organic Chemistry and Macromolecules

Hydrocarbons and Bonds

Hydrocarbons are organic molecules consisting entirely of carbon and hydrogen, connected by covalent bonds.

Functional Groups

Functional groups are specific groups of atoms within molecules that confer particular chemical properties.

Examples: Hydroxyl (-OH), carboxyl (-COOH), amino (-NH2), phosphate (-PO4).

Isomers

Isomers are molecules with the same molecular formula but different structures.

Types: Structural, geometric, and enantiomers.

Assembly and Disassembly of Biological Polymers

Biological polymers are assembled by dehydration synthesis and disassembled by hydrolysis.

Dehydration Synthesis: Removes water to form bonds.
Hydrolysis: Adds water to break bonds.

Levels of Protein Structure

Proteins have four levels of structure:

Primary: Sequence of amino acids.
Secondary: Alpha helices and beta sheets (hydrogen bonding).
Tertiary: 3D folding due to side chain interactions.
Quaternary: Multiple polypeptide chains.

Denaturation of Proteins

Denaturation is the loss of a protein's three-dimensional structure, often caused by heat, pH changes, or chemicals.

Key Point: Denatured proteins lose their biological function.

Biological Macromolecules Table

The four categories of biological macromolecules are carbohydrates, proteins, nucleic acids, and lipids. Their monomer/polymer forms and covalent bonds are summarized below:

Macromolecule	Monomer form (and examples)	Polymer form (and examples)	Type of covalent bond in polymer
Carbohydrates	Monosaccharides (e.g., glucose)	Polysaccharides (e.g., starch, cellulose)	Glycosidic bond
Proteins	Amino acids	Polypeptides (e.g., enzymes)	Peptide bond
Nucleic acids	Nucleotides	DNA, RNA	Phosphodiester bond
Lipids	Fatty acids, glycerol	Triglycerides, phospholipids, steroids, waxes	Esther bond (in triglycerides); other bonds in complex lipids Additional info: Lipids do not form true polymers.

Main Types of Lipids

Fats (Triglycerides): Energy storage.
Phospholipids: Major component of cell membranes.
Steroids: Hormones and membrane structure (e.g., cholesterol).
Waxes: Waterproofing and protection.