General Biology Unit 1 Study Guide: The Chemistry and Biology of Life

Unit 1: Biology as a Process for Understanding Life

This unit introduces the foundational concepts of biology, focusing on the characteristics of life, the cell theory, the flow of genetic information, and the chemical basis of biological molecules. The study guide is structured to help students understand biology as an interconnected discipline, emphasizing both conceptual understanding and factual knowledge.

Topic 1: Biology and Life

This section explores what it means to be alive, the cell theory, and the flow of genetic information.

• What Does It Mean to Say That Something Is Alive?

  • Living things share five fundamental traits: organization, energy use, information, replication, and evolution.

  • These traits are used by scientists to define life and distinguish living from non-living things.

  • Example: A bacterium can grow, reproduce, respond to its environment, and evolve, meeting all five criteria.

• Life Is Cellular

  • The cell theory states that all living things are composed of cells, which are the basic units of life.

  • Cells arise from pre-existing cells, not from spontaneous generation.

  • Example: Pasteur’s experiment with straight-necked vs. swan-necked flasks demonstrated that cells do not arise spontaneously.

• Life Processes: Information and Requires Energy

  • Genetic information is stored in DNA, which is organized into genes.

  • The central dogma describes the flow of genetic information: DNA → RNA → Protein.

  • Energy is required for life processes, obtained from sunlight (photosynthesis) or chemical compounds (cellular respiration).

• Life Evolves

  • Populations of organisms change over time through heritable changes (evolution).

  • Natural selection drives adaptation and diversity.

• The Tree of Life

  • All life is related through common ancestry, depicted as a branching tree.

  • Major domains: Bacteria, Archaea, Eukarya.

• Doing Biology

  • Science is based on asking testable questions and using evidence to answer them.

  • The scientific method involves forming hypotheses, making predictions, conducting experiments, and drawing conclusions.

  • Example: The question "Why do giraffes have long necks?" can be tested by comparing hypotheses about feeding vs. mating advantages.

Topic 2: The Chemical Basis of Life

This section covers the atomic and molecular structure of matter, chemical reactions, and the properties of water that are essential for life.

• Atoms, Ions, and Molecules

  • Atoms consist of protons, neutrons, and electrons.

  • The number of protons (atomic number) defines the element.

  • Isotopes are atoms of the same element with different numbers of neutrons.

  • Electrons are arranged in shells; the outermost shell determines chemical reactivity.

• Properties of Water and the Early Oceans

  • Water is a polar molecule, forming hydrogen bonds that give it unique properties: cohesion, adhesion, high specific heat, and solvent abilities.

  • Water’s structure supports life by stabilizing temperature and facilitating chemical reactions.

  • Acids and Bases: Acids donate protons (H+), bases accept protons. The pH scale measures hydrogen ion concentration.

• Chemical Reactions, Energy, and Chemical Evolution

  • Chemical reactions involve the making and breaking of chemical bonds.

  • Energy is transferred during reactions; exergonic reactions release energy, endergonic reactions require energy.

  • First Law of Thermodynamics: Energy cannot be created or destroyed, only transformed.

  • Second Law of Thermodynamics: Entropy (disorder) increases in isolated systems.

  • Spontaneity: A reaction is spontaneous if it increases entropy and/or releases energy.

Topic 3: Biological Macromolecules

This section introduces the four major classes of biological macromolecules: proteins, nucleic acids, carbohydrates, and lipids.

3.1 Proteins and Their Polymerization

• Amino Acids: The monomers of proteins, each with a central carbon, amino group, carboxyl group, hydrogen atom, and R group (side chain).

• Peptide Bonds: Amino acids are linked by peptide bonds to form polypeptides.

• Protein Structure: Proteins have four levels of structure: primary (sequence), secondary (alpha helices and beta sheets), tertiary (3D folding), and quaternary (multiple polypeptides).

• Protein Function: Proteins serve as enzymes, structural components, transporters, and more.

3.2 Nucleic Acids

• Monomers: Nucleotides, each consisting of a sugar, phosphate group, and nitrogenous base.

• DNA and RNA: DNA is double-stranded and stores genetic information; RNA is single-stranded and involved in protein synthesis.

• Base Pairing: In DNA, A pairs with T, and G pairs with C.

• Central Dogma: Information flows from DNA to RNA to protein.

3.3 Carbohydrates

• Monosaccharides: Simple sugars (e.g., glucose) that serve as energy sources and building blocks.

• Polysaccharides: Long chains of monosaccharides (e.g., starch, glycogen, cellulose) with structural and storage roles.

• Glycosidic Bonds: Link monosaccharides in polysaccharides.

3.4 Lipids

• Structure: Hydrophobic molecules including fats, phospholipids, and steroids.

• Fats: Composed of glycerol and fatty acids; used for energy storage.

• Phospholipids: Major components of cell membranes, with hydrophilic heads and hydrophobic tails.

• Steroids: Lipids with four fused rings (e.g., cholesterol).

Topic 4: Cell Membranes and Transport

This section covers the structure and function of biological membranes, including the movement of substances across membranes.

• Plasma Membrane: Defines the boundary of the cell and regulates the movement of substances in and out.

• Phospholipid Bilayer: Forms the basic structure of membranes; selectively permeable to different substances.

• Diffusion: Movement of molecules from high to low concentration.

• Osmosis: Diffusion of water across a selectively permeable membrane.

• Membrane Proteins: Facilitate transport, act as receptors, and provide structural support.

Table: Comparison of Biological Macromolecules

Macromolecule	Monomer	Main Functions	Examples
Proteins	Amino acids	Enzymes, structure, transport, signaling	Hemoglobin, enzymes
Nucleic Acids	Nucleotides	Genetic information storage and transfer	DNA, RNA
Carbohydrates	Monosaccharides	Energy storage, structure	Glucose, starch, cellulose
Lipids	Fatty acids, glycerol	Energy storage, membranes, signaling	Fats, phospholipids, steroids

Key Equations

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

• First Law of Thermodynamics: $\Delta E = q + w$ Where $\Delta E$ is the change in internal energy, $q$ is heat, and $w$ is work.

• Second Law of Thermodynamics (Entropy): $\Delta S > 0$ (for spontaneous processes in isolated systems)

Additional info: Some details, such as the specific examples of macromolecules and the structure of the scientific method, have been expanded for clarity and completeness.