General Biology Unit 1: Foundations of Life, Chemistry, and Cell Structure

Biology and Life

What is Biology?

Biology is the scientific study of life and living organisms. It encompasses a wide range of topics, from the molecular mechanisms inside cells to the interactions of organisms with their environment.

• Definition: Biology is the study of life, including its structure, function, growth, origin, evolution, and distribution.

• Goals: To understand the characteristics that define living things and the processes that sustain life.

What Does It Mean to Say That Something Is Alive?

Living things share certain fundamental traits that distinguish them from non-living matter.

• Key Traits of Life:

  • Order and organization

  • Response to stimuli

  • Reproduction

  • Growth and development

  • Energy processing

  • Regulation (homeostasis)

  • Evolutionary adaptation

• Cell Theory: All living things are composed of cells, which are the basic units of life.

• Example: Pasteur’s experiment disproved spontaneous generation, supporting the idea that all cells come from pre-existing cells.

Life Processes: Information and Energy

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

• Central Dogma: The flow of genetic information is from DNA to RNA to protein.

• Energy Use: Living organisms require energy to maintain order and carry out life processes.

Life Evolves

• Evolution: Populations of organisms change over generations through the process of natural selection.

• Heritable Changes: Genetic variations that are beneficial may become more common in a population over time.

The Tree of Life

• Phylogeny: The evolutionary history and relationships among species.

• Domains of Life: Bacteria, Archaea, and Eukarya.

Doing Biology

• Scientific Method: Involves making observations, forming hypotheses, conducting experiments, and drawing conclusions.

• Hypothesis Testing: Example: "Why do giraffes have long necks?" involves proposing hypotheses and testing them with experiments.

Chemical Foundations of Life

Atoms, Ions, and Molecules

All matter is composed of atoms, which combine to form molecules essential for life.

• Atomic Structure: Atoms consist of protons, neutrons, and electrons.

• Elements: Defined by the number of protons (atomic number).

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

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

Water and Its Properties

• Polarity: Water is a polar molecule, with partial positive and negative charges.

• Hydrogen Bonding: Leads to unique properties such as cohesion, adhesion, high specific heat, and solvent abilities.

• Acids and Bases: Acids donate protons (H+), bases accept protons. pH measures the concentration of H+ ions.

Chemical Reactions, Energy, and Chemical Evolution

• Chemical Reactions: Involve the making and breaking of chemical bonds.

• Energy Transfer: Energy is transferred during chemical reactions, often as heat or work.

• Thermodynamics:

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

  • Second Law: Entropy (disorder) tends to increase in a closed system.

• Spontaneity: A reaction is spontaneous if it increases the overall entropy of the universe.

Macromolecules: Structure and Function

Proteins

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

• Peptide Bonds: Link amino acids together via condensation reactions.

• Protein 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

• Function: Enzymes, structural support, transport, signaling, etc.

• Folding: Protein folding is often spontaneous and essential for function.

Nucleic Acids

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

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

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

• Directionality: DNA and RNA strands have 5' to 3' directionality.

• Central Dogma: DNA → RNA → Protein

Carbohydrates

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

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

• Functions: Energy storage, structural support, cell recognition.

• Glycosidic Bonds: Link monosaccharides in polysaccharides.

Lipids

• Structure: Mostly hydrophobic molecules, including fats, phospholipids, and steroids.

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

• Phospholipids: Major component of cell membranes; have hydrophilic heads and hydrophobic tails.

• Steroids: Four fused carbon rings; include cholesterol and hormones.

Cell Structure and Membranes

Plasma Membrane

• Function: Separates the cell from its environment and regulates the movement of substances in and out.

• Structure: Phospholipid bilayer with embedded proteins.

• Selective Permeability: Allows some substances to cross more easily than others.

Transport Across Membranes

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

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

• Concentration Gradient: Difference in concentration of a substance across a space.

• Membrane Proteins: Facilitate transport (channels, carriers, pumps).

Key Tables

Comparison of Macromolecules

Macromolecule	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	Energy storage, membranes, signaling

Key Equations

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

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

Additional info:

• Some sections referenced in the images (e.g., chemical evolution, early Earth) are marked as 'skip' for this course.

• Students are encouraged to focus on understanding concepts and being able to apply them, rather than memorizing isolated facts.