Foundations of Biology: Key Concepts and Cellular Structure

Chapter 1: Foundations of Biology

Key Properties and Themes of Life

• Biology is the scientific study of life, characterized by seven fundamental properties.

• Evolution serves as a unifying theme, explaining the relationships and diversity among living organisms.

• Biology relies on the scientific method, which involves forming and testing hypotheses through observation and experimentation.

The Seven Properties of Life

• Order: Living things exhibit complex but ordered organization.

• Regulation (Homeostasis): Organisms maintain stable internal conditions.

• Energy Processing: Organisms obtain and use energy to power activities.

• Growth and Development: Organisms grow and develop according to inherited instructions.

• Response to the Environment: Living things respond to environmental stimuli.

• Reproduction: Organisms reproduce their own kind.

• Evolutionary Adaptation: Populations evolve over generations through adaptations.

Hierarchy of Biological Organization

• Life is organized from the smallest to largest scale: molecule → organelle → cell → tissue → organ → organ system → organism → population → community → ecosystem → biosphere.

• Evolutionary relationships can be observed at each level.

The Cell: The Basic Unit of Life

• The cell is the smallest unit capable of all life functions.

• Cells contain specialized structures called organelles that perform specific functions.

• DNA is the universal genetic material, encoding instructions for life.

• Energy transfer is essential for life processes.

The Scientific Method

• Steps: Observation → Hypothesis Formation → Experimentation → Results → Interpretation.

• A hypothesis is a testable explanation for observations.

• Inductive reasoning is used to form hypotheses; deductive reasoning is used to test them.

Chapter 2: The Chemical Context of Life

Basic Chemistry for Biology

• Life depends on chemical principles; all living things are composed of matter and require energy.

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

Key Definitions

• Matter: Anything that has mass and occupies space.

• Element: A substance that cannot be broken down by chemical means.

• Compound: A substance consisting of two or more elements in a fixed ratio.

• Molecule: Two or more atoms held together by covalent bonds.

Elements Essential for Life

• Four elements make up most living matter: Carbon (C), Hydrogen (H), Oxygen (O), and Nitrogen (N).

Atomic Structure

• Atomic number: Number of protons in an atom; determines the element.

• Atomic mass: Sum of protons and neutrons.

Energy and Electrons

• Energy: The capacity to cause change.

• Potential energy: Stored energy due to position or structure.

• Kinetic energy: Energy of motion.

• Electrons have energy due to their position in electron shells.

• When electrons change shells, they absorb or release energy (important in processes like photosynthesis).

Chemical Bonds

• Covalent bond: Sharing of electron pairs between atoms (e.g., H2O).

• Ionic bond: Transfer of electrons from one atom to another (e.g., NaCl).

• Electronegativity: An atom's attraction for electrons in a bond.

• Polar covalent bond: Unequal sharing of electrons (e.g., water).

• Non-polar covalent bond: Equal sharing of electrons (e.g., O2).

• Hydrogen bond: Weak attraction between a hydrogen atom and an electronegative atom (important in water and DNA).

Chemical Reactions

• Chemical reactions involve the making and breaking of bonds.

• Parts of a chemical equation: Reactants (starting materials) and Products (ending materials).

• Five signs of a chemical reaction: color change, temperature change, gas production, precipitate formation, and light emission.

Chapters 3 & 4: Water and Carbon—The Molecules of Life

Properties of Water

• Water is a polar molecule due to polar covalent bonds, allowing it to form hydrogen bonds.

• Cohesion: Water molecules stick to each other.

• Adhesion: Water molecules stick to other substances.

• Water has a high heat capacity, absorbing and releasing heat slowly.

• Water is a universal solvent, dissolving many substances.

Solutions and Solubility

• Solvent: The dissolving agent (e.g., water).

• Solute: The substance dissolved (e.g., salt).

• Solution: A homogeneous mixture of solvent and solute.

• Hydrophilic: Water-loving substances (e.g., salts, sugars).

• Hydrophobic: Water-fearing substances (e.g., oils, fats).

Acids, Bases, and pH

• Acid: Substance that increases H+ concentration in solution.

• Base: Substance that decreases H+ concentration.

• pH scale: Ranges from 1 (acidic) to 14 (basic), with 7 as neutral.

• Buffer: Substance that minimizes changes in pH.

Carbon and Organic Molecules

• Organic compounds contain carbon and are found in living things.

• Carbon forms four covalent bonds, allowing for diverse molecules.

• Hydrocarbons: Molecules consisting only of carbon and hydrogen.

Macromolecules and Polymers

• Four main biomolecules: carbohydrates, proteins, lipids, nucleic acids.

• Monomer: Small building block molecule (e.g., glucose).

• Polymer: Large molecule made of repeating monomers (e.g., starch).

• Dehydration reaction: Joins monomers by removing water.

• Hydrolysis reaction: Breaks polymers into monomers by adding water.

Examples of Biomolecules

• Monosaccharide: Simple sugar (e.g., glucose).

• Oils vs. Fats: Oils are liquid at room temperature (unsaturated), fats are solid (saturated).

• Amino acids: Building blocks of proteins.

• Enzyme: Protein that speeds up chemical reactions (catalyst).

• DNA & RNA: Nucleic acids made of a nitrogenous base, five-carbon sugar, and phosphate group.

• DNA strands are held together by hydrogen bonds.

• ATP (Adenosine Triphosphate): Main energy currency of the cell.

Chapter 6: A Tour of the Cell

Cell Theory and Types of Cells

• Cell theory: All living things are made of one or more cells.

• Two main cell types: Prokaryotes (bacteria) and Eukaryotes (plants, animals, fungi, protists).

Prokaryotes vs. Eukaryotes

Feature	Prokaryotes	Eukaryotes
Nucleus	No	Yes
Organelles	No membrane-bound organelles	Membrane-bound organelles
Examples	Bacteria, Archaea	Plants, Animals, Fungi, Protists
Size	Generally smaller	Generally larger

Cell Membrane and Surface Area

• Cell membrane: Phospholipid bilayer that surrounds the cell, controlling entry and exit of substances.

• Surface area-to-volume ratio limits cell size; as cells grow, volume increases faster than surface area, limiting exchange with the environment.

Major Eukaryotic Organelles and Structures

• Nucleus: Contains genetic material (DNA).

• Nuclear membrane: Double membrane surrounding the nucleus.

• Nucleolus: Site of ribosome synthesis inside the nucleus.

• Ribosome: Site of protein synthesis; found free in cytoplasm or attached to rough ER.

• Endoplasmic Reticulum (ER):

  • Rough ER: Studded with ribosomes; synthesizes proteins.

  • Smooth ER: Lacks ribosomes; synthesizes lipids and detoxifies chemicals.

• Golgi apparatus: Modifies, sorts, and packages proteins and lipids for transport.

• Lysosome: Contains digestive enzymes to break down waste.

• Vacuole: Storage organelle; types include central vacuole (plants), contractile vacuole (protists), and food vacuole.

• Mitochondria: Site of cellular respiration; produces ATP; contains its own DNA.

• Chloroplast: Site of photosynthesis in plants and algae.

• Peroxisome: Breaks down fatty acids and detoxifies harmful substances.

• Cytoskeleton: Network of fibers supporting cell shape and movement; includes microtubules, microfilaments, and intermediate filaments.

• Microtubules: Hollow tubes; shape, support, and movement (cilia, flagella).

• Microfilaments: Thin rods; cell shape and movement.

• Intermediate filaments: Provide mechanical support.

• Cilia and Flagella: Structures for cell movement; cilia are short and numerous, flagella are long and few.

Cell Junctions

• Tight junctions: Seal cells together to prevent leakage.

• Gap junctions: Channels for communication between animal cells.

• Desmosomes: Anchor cells together.

• Plasmodesmata: Channels between plant cells for transport and communication.

Summary Table: Major Eukaryotic Organelles

Organelle	Main Function
Nucleus	Stores genetic information
Ribosome	Protein synthesis
Rough ER	Protein modification and transport
Smooth ER	Lipid synthesis, detoxification
Golgi apparatus	Sorting and packaging of proteins/lipids
Lysosome	Digestion of macromolecules
Vacuole	Storage and support
Mitochondria	ATP production
Chloroplast	Photosynthesis
Peroxisome	Breakdown of fatty acids, detoxification
Cytoskeleton	Cell shape, movement, division

Additional info:

• ATP (Adenosine Triphosphate) is the primary energy carrier in cells, produced mainly in mitochondria.

• DNA's double helix structure is stabilized by hydrogen bonds between complementary bases.