General Biology: Core Concepts and Cell Structure Study Guide

Biology: Core Concepts

Introduction to Biology

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

• Themes of Biology: Organization, information, energy and matter, interaction, evolution.

• Reductionism: The approach of reducing complex systems to simpler components for study.

• Emergent Properties: New properties that arise with each step upward in the hierarchy of life.

• Systems Biology: The study of biological systems as a whole, integrating interactions between components.

Scientific Method and Reasoning

The scientific method is a systematic approach to inquiry that involves observation, hypothesis formation, experimentation, and analysis.

• Inductive Reasoning: Drawing general conclusions from specific observations.

• Deductive Reasoning: Making predictions based on general principles or theories.

• Hypothesis: A testable explanation for an observation or scientific problem.

• Theory: A well-substantiated explanation of some aspect of the natural world.

The Chemistry of Life

Matter and Atomic Structure

All living and non-living things are composed of matter, which consists of atoms and molecules.

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

• Atom: The smallest unit of an element, consisting of protons, neutrons, and electrons.

• Subatomic Particles: Protons (positive), neutrons (neutral), electrons (negative).

• Atomic Number: Number of protons in an atom.

• Atomic Mass: Sum of protons and neutrons.

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

• Compound: A substance formed by the chemical combination of two or more elements.

Chemical Bonds and Interactions

Atoms interact to form molecules through various types of chemical bonds.

• Valence Electrons: Electrons in the outermost shell, important for bonding.

• Covalent Bond: Sharing of electron pairs between atoms (single, double, triple bonds).

• Ionic Bond: Transfer of electrons from one atom to another, resulting in charged ions.

• Hydrogen Bond: Weak attraction between a hydrogen atom and an electronegative atom.

• Chemical Reaction: Process that changes one set of chemicals into another.

• Chemical Equilibrium: State in which forward and reverse reactions occur at the same rate.

Properties of Water

Water is essential for life due to its unique chemical and physical properties.

• Cohesion: Attraction between molecules of the same substance.

• Adhesion: Attraction between molecules of different substances.

• Surface Tension: The measure of how difficult it is to stretch or break the surface of a liquid.

• Kinetic Energy: The energy of motion, important in temperature and heat transfer.

Solutions and pH

Solutions are mixtures where one substance is dissolved in another. The pH scale measures the concentration of hydrogen ions in a solution.

• Solution: Homogeneous mixture of solute and solvent.

• Acid: Substance that increases the hydrogen ion concentration of a solution.

• Base: Substance that reduces the hydrogen ion concentration.

• pH Scale: Measures acidity or basicity (0-14 scale).

• Buffer: Substance that minimizes changes in pH.

• Ocean Acidification: Decrease in ocean pH due to absorption of excess atmospheric CO2.

Organic Chemistry in Biology

Organic Molecules and Functional Groups

Organic chemistry focuses on carbon-based compounds, which are the foundation of biological molecules.

• Vitalism: The belief that organic compounds arise only in living organisms (now disproven).

• Mechanism: The view that physical and chemical laws govern all natural phenomena.

• Stanley Miller Experiment: Demonstrated the abiotic synthesis of organic compounds.

• Isomers: Compounds with the same molecular formula but different structures (structural, cis-trans, enantiomers).

• Functional Groups: Specific groups of atoms within molecules that determine chemical reactivity (hydroxyl, carbonyl, amino, sulfhydryl, phosphate, methyl).

Biological Molecules

Macromolecules and Polymers

Living organisms are composed of four major classes of macromolecules: carbohydrates, lipids, proteins, and nucleic acids.

• Macromolecule: Large, complex molecules (polymers) made from smaller subunits (monomers).

• Polymer: Long molecule consisting of many similar or identical building blocks.

• Monomer: The subunit that serves as the building block of a polymer.

Carbohydrates

• Dehydration Reaction: Chemical reaction that joins monomers by removing water.

• Hydrolysis Reaction: Breaking down polymers by adding water.

• Monosaccharides: Simple sugars (glucose, fructose).

• Disaccharides: Two monosaccharides joined by a glycosidic bond (sucrose, lactose).

• Polysaccharides: Large carbohydrates (starch, glycogen, cellulose, chitin).

Lipids

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

• Phospholipids: Major component of cell membranes.

• Steroids: Lipids with a carbon skeleton consisting of four fused rings (cholesterol, hormones).

Proteins

• Amino Acids: Building blocks of proteins.

• Polypeptide: Polymer of amino acids linked by peptide bonds.

• Protein Structure: Primary, secondary, tertiary, and quaternary levels of organization.

Nucleic Acids

• Nucleic Acid: DNA and RNA, polymers of nucleotides.

• Nucleotide: Monomer consisting of a sugar, phosphate group, and nitrogenous base.

A Tour of the Cell

Cell Types and Structures

Cells are the basic units of life. They can be classified as prokaryotic or eukaryotic.

• Bacteria, Archaea, Eukarya: The three domains of life.

• Prokaryotic Cell: Lacks a nucleus and membrane-bound organelles.

• Eukaryotic Cell: Contains a nucleus and membrane-bound organelles.

• Plasma Membrane: Selectively permeable barrier surrounding the cell.

• Cytoplasm and Cytosol: The interior of the cell and the fluid component, respectively.

Cellular Components

• Nucleus: Contains genetic material (DNA).

• Nucleoid: Region in prokaryotes where DNA is located.

• Chromosomes: Structures that carry genetic information.

• Ribosome: Site of protein synthesis.

• Endomembrane System: Includes nucleus, rough and smooth ER, Golgi apparatus, lysosomes, vacuoles, and plasma membrane.

• Mitochondria: Site of cellular respiration and ATP production.

• Chloroplasts: Site of photosynthesis in plant cells.

• Endosymbiont Theory: Explains the origin of mitochondria and chloroplasts as formerly free-living bacteria.

Cytoskeleton and Cell Surface

• Cytoskeleton: Network of microtubules, microfilaments, and intermediate filaments that provide structural support.

• Centrosome, Centrioles: Organize microtubules in animal cells.

• Cilia and Flagella: Structures for cell movement.

• Cell Wall: Rigid structure outside the plasma membrane in plants, fungi, and some protists.

• Capsule: Protective outer layer in some prokaryotes.

• ECM (Extracellular Matrix): Network of proteins and carbohydrates outside animal cells.

• Intercellular Junctions: Structures that connect cells (plasmodesmata in plants; tight junctions, desmosomes, gap junctions in animals).