Biology Midterm

. Introduction to Biology

• Levels of Organization: Cell → Tissue → Organ → Organ System → Organism → Population → Community → Ecosystem → Biosphere

• Properties of Life: Order, Growth, Reproduction, Homeostasis, Response to Stimuli, Energy Processing, Evolution

• Prokaryotes vs. Eukaryotes:

  • Prokaryotes – No nucleus, simple, bacteria & archaea

  • Eukaryotes – Nucleus, organelles, plants, animals, fungi, protists

• Process of Science:

  • Experimental Design: Importance of a control group

  • Theory vs. Hypothesis: A theory is well-supported, a hypothesis is a testable prediction

• Taxonomy: Three domains of life:

  1. Bacteria – Prokaryotes (E. coli)

  2. Archaea – Prokaryotes (extremophiles)

  3. Eukarya – Eukaryotic cells (plants, animals, fungi, protists)

II. The Chemistry of Life

• Atoms & Subatomic Particles: Proton (+, nucleus), Neutron (0, nucleus), Electron (-, orbitals)

• Isotopes: Atoms with different neutron counts

• Chemical Bonds:

  • Covalent: Share electrons

  • Ionic: Transfer electrons

  • Hydrogen: Weak attraction between molecules

• Water Properties:

  • Hydrogen bonds hold water molecules together

  • Cohesion (water sticks to itself) vs. Adhesion (sticks to surfaces)

  • pH Scale: Acids = More H+ ions, Bases = Fewer H+ ions

• Macromolecules & Monomers:

  1. Carbohydrates → Monosaccharides (Glucose)

  2. Proteins → Amino Acids (20 types, differ by R-group)

  3. Lipids → Not polymers (Major lipid in membranes = phospholipids)

  4. Nucleic Acids → Nucleotides (DNA/RNA components)

• Stabilizing Bonds: Hydrogen bonds help form protein & DNA 3D structures

III. Cell Structure and Function

• Cell Theory:

  1. All living things are made of cells

  2. Cells are the basic unit of life

  3. Cells come from preexisting cells

• Microscopes:

  • Light Microscope: Less detail, live cells

  • Electron Microscope: High resolution, dead cells only

• Prokaryotes vs. Eukaryotes: Eukaryotes have organelles

• Animal vs. Plant Cells:

  • Plant Cells have chloroplasts, cell walls, central vacuole

• Organelle Functions:

  • Chloroplast: Photosynthesis

  • Mitochondria: ATP production

  • Golgi Apparatus: Protein modification/packaging

  • Nucleus: DNA storage

  • ER (Smooth & Rough): Protein/lipid synthesis

  • Peroxisome: Detoxification

• Membrane Structure:

  • Phospholipids: Hydrophilic head, hydrophobic tail → form bilayers in water

IV. How Cells Obtain Energy

• Energy Reactions:

  • Exergonic: Release energy

  • Endergonic: Require energy

• Pathways:

  • Anabolic: Build molecules

  • Catabolic: Break down molecules

• Enzymes & Inhibition:

  • Substrate binds to active site

  • Competitive inhibitor: Blocks active site

  • Non-competitive inhibitor: Binds allosteric site, changes shape

• Cellular Respiration (Aerobic - Requires Oxygen):

  1. Glycolysis (Cytoplasm) → Produces ATP & pyruvate

  2. Citric Acid Cycle (Mitochondria) → Produces NADH, FADH₂

  3. Electron Transport Chain (Mitochondrial membrane) → Uses H+ gradient for ATP production

• Anaerobic Respiration (No Oxygen):

  • Fermentation:

    • Alcoholic Fermentation: Produces ethanol (yeast)

    • Lactic Acid Fermentation: Produces lactate (muscles)

  • Obligate Anaerobes: Can’t survive in oxygen