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General Biology Key Concepts

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  • Biological organization levels

    Order from largest to smallest: biosphere, ecosystem, community, population, organism, organ system, organ, tissue, cell, organelle, molecule.

  • Difference between eukaryotic and prokaryotic cells

    Eukaryotic cells have a nucleus and membrane-bound organelles; prokaryotic cells lack a nucleus and membrane-bound organelles.

  • Basic structure of DNA

    DNA is a double helix composed of nucleotides with a sugar-phosphate backbone and nitrogenous bases (A, T, C, G).

  • Steps to make a protein from DNA

    DNA is transcribed into mRNA, which is then translated by ribosomes to form a protein.

  • Energy and matter transfer in ecosystems

    Energy flows through ecosystems (usually entering as light and exiting as heat), while matter cycles between organisms and the environment.

  • Definition of evolution

    Evolution is the change in the genetic composition of a population over successive generations.

  • The three domains of life

    Bacteria, Archaea, and Eukarya are the three domains of life.

  • Darwin’s two main points about evolution

    1) Species change over time; 2) Natural selection is the mechanism driving adaptation.

  • Scientific method steps

    Observation, question, hypothesis, prediction, experiment, analysis, conclusion.

  • Hypothesis vs prediction

    A hypothesis is a testable explanation; a prediction is a specific expected outcome derived from the hypothesis.

  • Independent and dependent variables in controlled experiments

    Independent variable is manipulated; dependent variable is measured.

  • Atomic structure basics

    Atoms consist of protons and neutrons in the nucleus, with electrons in shells around it.

  • Ionic vs covalent bonds

    Ionic bonds form by electron transfer; covalent bonds form by electron sharing.

  • Nonpolar vs polar covalent bonds

    Nonpolar covalent bonds share electrons equally; polar covalent bonds share electrons unequally.

  • Properties of water

    Water is polar, forms hydrogen bonds, has high specific heat, cohesion, adhesion, and is a good solvent.

  • Four classes of macromolecules

    Carbohydrates, lipids, proteins, and nucleic acids.

  • Monomers vs polymers

    Monomers are single units; polymers are chains of monomers linked together.

  • Polymer formation and breakdown

    Polymers are formed by dehydration synthesis and broken down by hydrolysis.

  • Endomembrane system organelles

    Includes nuclear envelope, ER, Golgi apparatus, lysosomes, vacuoles, and plasma membrane.

  • Selective permeability of plasma membrane

    Membrane allows some substances to pass while blocking others, maintaining cellular environment.

  • Fluid mosaic model

    Describes the plasma membrane as a fluid lipid bilayer with embedded proteins forming a mosaic.

  • Passive vs active transport

    Passive transport requires no energy and moves substances down their concentration gradient; active transport requires energy to move substances against the gradient.

  • First law of thermodynamics

    Energy cannot be created or destroyed, only transformed.

  • Second law of thermodynamics

    Entropy (disorder) of the universe increases over time.

  • Free energy

    Energy available to do work in a system, denoted as \(\Delta G\).

  • Exergonic vs endergonic reactions

    Exergonic reactions release energy; endergonic reactions require energy input.

  • Enzymes and activation energy

    Enzymes are biological catalysts that lower activation energy to speed up reactions.

  • Aerobic vs anaerobic respiration

    Aerobic uses oxygen; anaerobic does not use oxygen for energy production.

  • Photosynthesis main pigment

    Chlorophyll a is the primary photosynthetic pigment.