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General Biology: Cell Structure, Membranes, and Energy

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  • Cell theory main points
    1. The basic unit of life is the cell.
    2. All living things are composed of cells.
    3. All cells come from other cells.
  • Phospholipid bilayer structure
    Composed of hydrophilic heads facing outward and hydrophobic tails facing inward, forming a selective barrier in cell membranes.
  • Role of cholesterol in plasma membrane
    Cholesterol provides rigidity and stability to the membrane by preventing phospholipids from packing too closely.
  • Difference between prokaryotic and eukaryotic cells
    Prokaryotes lack a nucleus and membrane-bound organelles; eukaryotes have a nucleus and complex organelles.
  • Function of ribosomes
    Sites of protein synthesis, translating mRNA into polypeptides.
  • Nucleus components and function
    Contains chromatin (DNA + proteins), nucleolus (makes ribosomal RNA), and is enclosed by a double membrane called the nuclear envelope with pores for molecule transport.
  • Endomembrane system components
    Includes the nuclear envelope, rough and smooth ER, Golgi apparatus, lysosomes, vacuoles, and plasma membrane; involved in synthesis, modification, and transport of molecules.
  • Rough vs Smooth Endoplasmic Reticulum
    Rough ER has ribosomes and assembles membrane proteins.
    Smooth ER synthesizes lipids and stores calcium ions.
  • Golgi apparatus function
    Modifies, sorts, and packages proteins and lipids received from the ER for secretion or use in the cell.
  • Lysosome role
    Contains digestive enzymes to break down macromolecules and worn-out organelles.
  • Mitochondria function and structure
    Site of cellular respiration and ATP production; has outer and inner membranes with folds called cristae to increase surface area.
  • Chloroplast function
    Site of photosynthesis in plants; contains DNA, ribosomes, thylakoids, and stroma where sugars are synthesized.
  • Cytoskeleton components and roles
    Microfilaments support membrane and cell movement.
    Intermediate filaments anchor organelles.
    Microtubules provide cell shape and intracellular transport.
  • Types of cell junctions in animal cells
    Tight junctions prevent fluid leakage.
    Desmosomes anchor cells.
    Gap junctions allow communication via cytoplasmic channels.
  • Plasmodesmata in plant cells
    Membrane-lined channels that connect cytoplasm of adjacent plant cells for transport and communication.
  • Passive vs active transport
    Passive transport moves substances down their concentration gradient without energy.
    Active transport moves substances against the gradient using ATP.
  • Osmosis and tonicity
    Osmosis is water diffusion across a membrane.
    Hypotonic: water enters cell.
    Isotonic: no net water movement.
    Hypertonic: water leaves cell.
  • Facilitated diffusion
    Passive transport of molecules across membranes via specific transport proteins.
  • ATP structure and role
    Composed of adenine, ribose, and three phosphate groups; stores and transfers energy for cellular work.
  • Phosphorylation in energy coupling
    Attachment of a phosphate group to a molecule, often transferring energy from ATP to drive endergonic reactions.
  • Exergonic vs endergonic reactions
    Exergonic: release energy, spontaneous.
    Endergonic: require energy input, non-spontaneous.
  • Enzyme function
    Catalysts that lower activation energy to speed up reactions without being consumed.
  • ATP cycle
    ATP is hydrolyzed to ADP + phosphate releasing energy; ADP is recycled to ATP using energy from cellular respiration.