General Biology Study Guide: Key Concepts and Principles

Chapter 1: Introduction to Biology

Hierarchy of Life and Levels of Organization

The hierarchy of life refers to the organization of living things from the simplest to the most complex levels. Understanding this hierarchy helps in studying biological systems and their interactions.

• Levels of Organization: Atoms → Molecules → Organelles → Cells → Tissues → Organs → Organ Systems → Organisms → Populations → Communities → Ecosystems → Biosphere.

• Example: Neuron (cell) → Brain (organ) → Nervous system (organ system) → Organism (human).

Genetic Code and Forms of Life

All living organisms share a common genetic code, which is the set of rules by which information encoded in genetic material (DNA or RNA) is translated into proteins.

• Universal Genetic Code: The genetic code is nearly universal among all organisms, supporting the idea of common ancestry.

Reductionism vs. Systems Biology

These are two approaches to studying biology:

• Reductionism: Breaking down complex systems into simpler components for study.

• Systems Biology: Studying the interactions and relationships between components of biological systems.

Prokaryotic vs. Eukaryotic Organisms

Cells are classified as prokaryotic or eukaryotic based on their structure.

• Prokaryotes: Lack a nucleus and membrane-bound organelles (e.g., Bacteria, Archaea).

• Eukaryotes: Have a nucleus and membrane-bound organelles (e.g., Plants, Animals, Fungi, Protists).

• Similarities: Both have a cell membrane, DNA, cytoplasm, and ribosomes.

Domains and Kingdoms of Life

Life is classified into three domains and several kingdoms based on genetic and cellular characteristics.

• Three Domains: Bacteria, Archaea, Eukarya.

• Kingdoms in Eukarya: Protista, Fungi, Plantae, Animalia.

Characteristics of Kingdoms

• Animals: Multicellular, ingest food.

• Plants: Multicellular, cell wall made of cellulose, photosynthetic.

• Fungi: Heterotrophs, absorb digested food using hair-like structures (hyphae).

• Protists: Diverse group, mostly unicellular.

Scientific Method and Experimental Design

The scientific method is a systematic approach to research and experimentation.

• Steps: Observation → Hypothesis → Experiment → Data Collection → Analysis → Conclusion.

• Control Group: Used for comparison; does not receive the experimental treatment.

• Variables: Independent variable (manipulated), Dependent variable (measured).

Qualitative vs. Quantitative Data

• Qualitative Data: Descriptive, non-numerical (e.g., color, texture).

• Quantitative Data: Numerical measurements (e.g., height, weight).

Chapter 2: Atomic Structure and Chemical Bonds

Atomic Structure

Atoms are the basic units of matter, composed of protons, neutrons, and electrons.

• Protons: Positively charged, found in the nucleus.

• Neutrons: Neutral, found in the nucleus.

• Electrons: Negatively charged, orbit the nucleus in shells.

• Electron Shells: 1st shell holds 2 electrons, 2nd and 3rd shells hold up to 8 electrons each.

• Atomic Number: Number of protons.

• Mass Number: Protons + Neutrons.

Electron Orbitals and Valence Electrons

• Orbitals: Regions where electrons are likely to be found; s, p, d, f shapes.

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

Isotopes

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

• Example: Carbon-12, Carbon-13, Carbon-14.

Periodic Table and Element Properties

• Elements in the same column (group) have similar chemical properties due to similar valence electron configurations.

• Example: Sodium and potassium are both alkali metals and react similarly with water.

Covalent and Ionic Bonds

• Covalent Bonds: Atoms share electrons; can be polar (unequal sharing) or non-polar (equal sharing).

• Ionic Bonds: Atoms transfer electrons, resulting in oppositely charged ions that attract each other.

Electronegativity

• Electronegativity: The ability of an atom to attract electrons in a bond.

• Differences in electronegativity determine bond polarity.

Common Elements in Living Cells

• Major Elements: Carbon, hydrogen, oxygen, nitrogen (CHON).

• Trace Elements: Required in small amounts (e.g., iron, zinc).

Bond Formation and Properties

• Bonding depends on the number of valence electrons and the tendency to achieve a full outer shell (octet rule).

Atomic Properties and Chemical Behavior

• Properties such as atomic number, electron configuration, and ionization energy influence how atoms interact.

Chapter 3: Water and Its Properties

Hydrophobic vs. Hydrophilic Compounds

• Hydrophobic: Repel water; nonpolar molecules (e.g., oils).

• Hydrophilic: Attract water; polar or charged molecules (e.g., salts, sugars).

Hydrogen Bonding and Water Properties

• Hydrogen bonds form between the slightly positive hydrogen atom of one water molecule and the slightly negative oxygen atom of another.

• Emergent Properties of Water:

  • Cohesion and adhesion

  • High specific heat

  • High heat of vaporization

  • Expansion upon freezing

  • Versatility as a solvent

Mole Concept

• 1 mole of a substance = molecular mass in grams = $6.02 \times 10^{23}$ molecules (Avogadro's number).

Making Solutions

• To make a solution, dissolve a known mass of solute in a specific volume of solvent.

Acids, Bases, and pH

• Acid: Substance that increases $[H^+]$ in solution.

• Base: Substance that decreases $[H^+]$ or increases $[OH^-]$.

• pH Scale: Measures hydrogen ion concentration; $pH = -\log[H^+]$.

Dissociation Constant and pH Calculations

• The dissociation constant ($K_w$) for water is $10^{-14}$ at 25°C.

• If $[OH^-]$ is known, $[H^+]$ can be calculated: $[H^+][OH^-] = 10^{-14}$.

• pH and pOH are related: $pH + pOH = 14$.

Comparing Solutions and Buffers

• Solutions with different pH values have different $[H^+]$ concentrations.

• Buffers: Substances that minimize changes in pH by accepting or donating H+ ions.

Chapter 4: Carbon and Organic Molecules

Importance of Carbon

• Carbon is the backbone of most biological molecules due to its ability to form four covalent bonds.

Electron Configuration of Carbon

• Carbon has 6 electrons: 2 in the first shell, 4 in the second shell (valence electrons).

Hydrocarbons and Hydrophobicity

• Hydrocarbons: Molecules consisting only of carbon and hydrogen; nonpolar and hydrophobic.

Isomers

• Isomers: Compounds with the same molecular formula but different structures.

• Types: Structural isomers, cis-trans isomers, enantiomers.

Functional Groups

• Functional groups are specific groups of atoms within molecules that determine the chemical properties of those molecules.

• Common Functional Groups:

  • Hydroxyl (-OH)

  • Carbonyl (C=O)

  • Carboxyl (-COOH)

  • Amino (-NH2)

  • Sulfhydryl (-SH)

  • Phosphate (-PO4)

  • Methyl (-CH3)

• Recognizing functional groups is essential for identifying organic molecules and predicting their reactivity.