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, emphasizing the scientific process, the chemical basis of life, and the structure and function of biological molecules. The following notes are organized by major topics and subtopics, providing definitions, explanations, and examples relevant to a college-level General Biology course.

Topic 1: Biology and Life

This section explores what it means to be alive, the characteristics of living things, and the cell theory.

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

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

  • Organization: Living things are made of cells.

  • Energy Use: Organisms acquire and use energy.

  • Information: Organisms process hereditary and environmental information.

  • Replication: Organisms are capable of reproduction.

  • Evolution: Populations of organisms evolve over time.

  • Example: A bacterium reproduces, uses nutrients for energy, and evolves resistance to antibiotics.

• Cell Theory

  • All living things are composed of cells, the basic unit of life.

  • Cells arise from pre-existing cells, not spontaneously.

  • Example: Pasteur’s experiment disproved spontaneous generation by showing that sterilized broth remained free of microorganisms unless exposed to pre-existing cells.

• Life Processes: Information and Energy

  • Genetic Information: DNA is the hereditary material; genes are segments of DNA that code for proteins.

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

  • Energy: Organisms obtain energy from sunlight (photosynthesis) or chemical compounds (cellular respiration).

• Life Evolves

  • Populations evolve through changes in heritable traits over generations.

  • Example: Antibiotic resistance in bacteria is an example of evolution by natural selection.

• The Tree of Life

  • All life is related through common ancestry; the tree of life shows evolutionary relationships.

  • Major branches: Bacteria, Archaea, Eukarya.

• Doing Biology

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

  • Scientific Method: Observation, hypothesis, prediction, experiment, analysis, conclusion.

  • Example: The question "Why do giraffes have long necks?" can be tested by comparing feeding behavior and reproductive success.

Chapter 2: Chemical Foundations of Life

This chapter covers the chemical basis of life, including atoms, molecules, water, and chemical reactions.

2.1 Atoms, Ions, and Molecules

• Atoms: The smallest units of matter, composed of protons, neutrons, and electrons.

• Atomic Number: Number of protons in the nucleus.

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

• Ions: Atoms that have gained or lost electrons, becoming charged.

• Covalent Bonds: Atoms share electron pairs.

• Ionic Bonds: Atoms transfer electrons, resulting in attraction between oppositely charged ions.

• Polar vs. Nonpolar Covalent Bonds: Polar bonds have unequal sharing of electrons, leading to partial charges.

• Example: Water (H2O) is a polar molecule due to unequal sharing of electrons between oxygen and hydrogen.

2.2 Properties of Water and the Early Oceans

• Cohesion: Water molecules stick together via hydrogen bonds.

• Adhesion: Water molecules stick to other substances.

• Surface Tension: Water has a high surface tension due to hydrogen bonding.

• Water as a Solvent: Water dissolves many substances, making it essential for life.

• Acids and Bases: Acids donate protons (H+), bases accept protons.

• pH Scale: Measures the concentration of H+ ions; $\text{pH} = -\log_{10}[\text{H}^+]$

2.3 Chemical Reactions, Energy, and Chemical Evolution

• Chemical Reactions: Rearrangement of atoms to form new substances.

• Energy: The capacity to do work; includes potential and kinetic energy.

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

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

• Spontaneous Reactions: Occur without input of energy if they increase entropy and/or release energy.

Chapter 3: Protein Structure and Function

This chapter discusses the structure, function, and diversity of proteins.

3.1 Amino Acids and Their Polymerization

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

• Peptide Bonds: Covalent bonds linking amino acids in proteins.

• Polymerization: Formation of polypeptides via condensation (dehydration) reactions.

• Functional Groups: Side chains determine properties and functions of amino acids.

• Example: Hemoglobin is a protein composed of four polypeptide chains, each with specific amino acid sequences.

3.2 What Do Proteins Look Like?

• Primary Structure: Sequence of amino acids.

• Secondary Structure: Local folding (alpha helices, beta sheets) stabilized by hydrogen bonds.

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

• Quaternary Structure: Association of multiple polypeptide chains.

3.3 Folding and Function

• Protein folding is critical for function; misfolded proteins can cause disease.

• Folding is often spontaneous but may be assisted by molecular chaperones.

3.4 Protein Functions

• Proteins serve as enzymes, structural components, transporters, signals, and more.

• Enzymes: Catalyze biochemical reactions by lowering activation energy.

Chapter 4: Nucleic Acids and the RNA World

This chapter covers the structure and function of nucleic acids (DNA and RNA).

4.1 What is a Nucleic Acid?

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

• Types: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).

• Phosphodiester Bond: Covalent bond linking nucleotides in a nucleic acid chain.

4.2 DNA Structure and Function

• DNA is a double helix with complementary base pairing (A-T, G-C).

• Base pairing allows DNA to be replicated and transcribed into RNA.

• DNA stores genetic information; RNA helps express it.

4.3 RNA Structure and Function

• RNA is usually single-stranded but can form complex structures.

• RNA can act as a catalyst (ribozyme) and as genetic material in some viruses.

Chapter 5: Carbohydrates

This chapter introduces the structure and function of carbohydrates.

5.1 Sugars as Monomers

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

• Disaccharides: Two monosaccharides linked by glycosidic bonds (e.g., sucrose).

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

• Small changes in sugar structure can have major effects on function.

5.2 The Structure of Polysaccharides

• Polysaccharides differ in branching and types of glycosidic bonds.

• Starch: Energy storage in plants.

• Glycogen: Energy storage in animals.

• Cellulose: Structural component in plant cell walls.

• Chitin: Structural component in fungi and arthropods.

• Peptidoglycan: Structural component in bacterial cell walls.

5.3 What Do Carbohydrates Do?

• Serve as energy sources and structural materials.

• Participate in cell recognition and signaling.

Chapter 6: Lipids, Membranes, and the First Cells

This chapter covers the structure and function of lipids and biological membranes.

6.1 Lipid Structure and Function

• Hydrocarbons: Chains of carbon and hydrogen; form the backbone of fatty acids.

• Fatty Acids: Can be saturated (no double bonds) or unsaturated (one or more double bonds).

• Triglycerides: Energy storage molecules composed of glycerol and three fatty acids.

• Phospholipids: Major component of cell membranes; amphipathic (hydrophilic head, hydrophobic tails).

6.2 Phospholipid Bilayers

• Phospholipids spontaneously form bilayers in water, creating a selectively permeable membrane.

• Membrane fluidity is affected by temperature, fatty acid composition, and cholesterol content.

6.3 How Substances Move Across Lipid Bilayers: Diffusion and Osmosis

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

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

• Concentration Gradient: Difference in concentration across a space or membrane.

6.4 Proteins Alter Membrane Structure and Function

• Membrane proteins facilitate the movement of substances across membranes (channels, carriers, pumps).

• Some proteins participate in active transport, requiring energy (usually ATP).

Summary Table: Major Biological Molecules

Molecule Type	Monomer	Bond Type	Main Functions
Proteins	Amino acids	Peptide bond	Enzymes, structure, transport, signaling
Nucleic Acids	Nucleotides	Phosphodiester bond	Genetic information storage and transfer
Carbohydrates	Monosaccharides	Glycosidic bond	Energy storage, structure, cell recognition
Lipids	Fatty acids, glycerol	Ester bond	Membranes, energy storage, signaling

Additional info: Some sections (e.g., chemical evolution, early Earth) are noted as "skip" or to be covered in later courses. The above guide focuses on the core concepts for introductory biology.