Essential Concepts in Biology: A Comprehensive Review

Posted on Mar 6, 2025 in Biology

Essential Concepts in Biology

• What is Science?

  Science is a body of knowledge and a process for generating that knowledge.

• The Scientific Method

  The steps include:
  • Observations
  • Hypothesis: “If… then…”
  • Predictions
  • Test (Observations and Experiments)

• Observation Defined

  A description, measurement, or record of any object or scientific phenomenon.

• Hypothesis: Definition and Testing

  An informed, logical, and plausible explanation for observations of the natural world. It should be possible to show that a scientific hypothesis is false. Tested through observational studies, experiments, or both.

• Independent vs. Dependent Variables

  • Independent variable: cause.
  • Dependent variable: effect.

• Scientific Fact vs. Scientific Theory

  • Scientific Fact: A direct and repeatable observation of the natural world.
  • Scientific Theory: A major explanation about the natural world that has been confirmed through extensive testing in diverse ways by independent researchers.

• Characteristics of Living Organisms

  • Composed of one or more cells
  • Reproduce using DNA
  • Obtain energy from the environment to support metabolism
  • Sense their environment and respond to it
  • Maintain a constant internal environment (homeostasis)
  • Can evolve as groups

• Cell Defined

  Smallest and most basic unit of life.

• Biological Evolution Defined

  Genetic change in a population that is inherited over several generations.

• Biological Hierarchy

  Atoms → Molecules → Cells → Tissues → Organs → Organ Systems → Organisms → Population → Community → Ecosystem → Biome → Biosphere

• Element Defined

  A pure substance that has distinctive physical and chemical properties and cannot be broken down to other substances by ordinary chemical methods.

• Atom Defined

  Smallest unit of an element that still has the distinctive chemical properties of that element.

• Matter Defined

  Anything that has mass and takes up space (stuff).

• Components of an Atom

  • Proton: + charge
  • Neutron: neutral charge
  • Electron: – charge

• Calculating Atomic Mass

  Protons + neutrons = atomic mass.

• Elements in Living Things

  Carbon, Hydrogen, Oxygen, Nitrogen

• Unique Properties of Water

  See slides 25-30 (chemistry of life part 1).

• Types of Chemical Bonds

  Covalent, Ionic, Hydrogen.

• Parts of a Chemical Equation

  Elements/Reactants/Products

• Calculating Product Molecules

  Use a chemical equation to calculate the number of molecules of product created by a given number of molecules of reactant. See slide 6 in chemistry of life part 2.

• pH Scale: Acids and Bases

  See slide 11 & 12 in chemistry of life part 2.

• H+ and OH- Ions

  Base: A compound that releases OH- ions

• H+ Ion Concentration and pH

  For every level, add a 0.

• Macromolecules: Monomers, Polymers, and Function

  • Carbohydrates

    Sugar, Monosaccharides (monomers) → (Glucose, Fructose, Galactose). Disaccharide → Two monosaccharides joined by a covalent bond – Ex: Glucose + Fructose → Sucrose (table sugar). Polysaccharide (Polymer) Cellulose, Starch, Glycogen.

  • Lipids

    Fats & Oils – Fatty Acid (monomer) saturated & unsaturated → Triglycerides, Phospholipids, Sterols (Steroids)

  • Proteins

    Amino Acid (monomer) 20 different types, Amino group (-NH2), Carboxyl group (-COOH), R Group, Polypeptide (Polymer)

  • Nucleic Acids

    (polymer), DNA and RNA, Nucleotide (Monomer)

• Structure of Monomers

  • Monosaccharide: Glucose (C₆H₁₂O₆), Fructose (C₆H₁₂O₆), Galactose (C₆H₁₂O₆)
  • Fatty Acid: Long chain of Carbon with all other available bonding sites being occupied by Hydrogen.
  • Amino Acid: Central Carbon covalently bonded to a Hydrogen atom
  • Nucleotide: Five-carbon sugar

• Levels of Protein Structure

  Primary structure, Secondary structure, Tertiary structure, and Quaternary structure.

• Denaturation Defined

  When the proteins 3D structure is altered by heat, the protein is no longer functional (e.g., cooking an egg).

• Dehydration vs. Hydrolysis Reactions

  • Dehydration reaction: A water molecule is removed from the combination of two monosaccharides.
  • Hydrolysis reaction: A water molecule is added to the two monosaccharides. One gets an H+, the other gets an OH-.

• Saturated vs. Unsaturated Fatty Acids

  Saturated fatty acid: Saturated with Hydrogen, No double bond, Straight chain. Unsaturated Fatty Acid: Double bond, Fewer Hydrogen atoms, Bent chain.

• Nitrogenous Bases of DNA and RNA

  Guanine, Cytosine, Adenine, Thymine (DNA only), Uracil (RNA only).

• Plasma Membrane and its Functions

  Separates the cell from the surrounding environment. Determines what can enter and leave the cell. Sends and receives chemical signals with the environment.

• Types of Membrane Proteins

  • Transport proteins: Carry specific materials into or out of the cell. Different protein for each type of material.
  • Receptor proteins: Send and receive chemical signals from outside the cell.
  • Adhesion proteins: Attach the cell to other cells or to the Extracellular Matrix – A dense mat of biomolecules that forms between cells.

• Multicellular vs. Single-Celled Organisms

• Components Found in All Cells

  Identify components found in all cells and describe their function

• Components of Eukaryotic Cells

  Nucleus, Endoplasmic Reticulum (ER), Transport Vesicles, Golgi apparatus, Lysosomes and Vacuoles, Mitochondria, Chloroplasts, The Cytoskeleton.

• Diffusion Defined

  Diffusion is the action of molecules moving from an area of high concentration to an area of lower concentration.

• Water and Cells in Different Solutions

  • Hypertonic solution

    – Higher concentration of solutes outside the cell than inside – Water will flow out of the cell – Cell will shrivel up (bad news!)

  • Isotonic solution

    – Same concentration of solutes inside the cell as outside – Water will flow equally into and out of the cell – Human cells are happy in this solution – Plant cells are still a little unhappy

  • Hypotonic solution

    – Lower concentration of solutes outside of the cell than inside – Water will flow into the cell – Animal cells will burst! – Plant cells are very happy

• Osmosis Defined

  Water will move from an area with a low concentration of solutes to an area with a high concentration of solutes.

• Active vs. Passive Transport

  • Passive Transport: Does not require energy to move materials across the membrane.
  • Active Transport: Requires energy to move materials across the membrane.

• Types of Transport

  Identify different types of transport by their description – see ch.4 The Cell Membrane and Membrane Transport PowerPoint.