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Exam 2 biol 1710 prep part 1

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Termini in questo insieme (25)

  • What is the fluid mosaic model of cellular membranes?
    Membranes are flexible phospholipid bilayers with proteins embedded that can move within the layer, forming specialized regions for transport, signaling, or recognition.
  • What are the main components of the cell membrane?
    Lipids (phospholipids, cholesterol, glycolipids), proteins (integral and peripheral), and carbohydrates (glycolipids and glycoproteins) arranged dynamically.
  • How does cholesterol affect membrane fluidity?
    Cholesterol stabilizes membrane fluidity by restraining phospholipid movement at warm temperatures and preventing tight packing at cool temperatures.
  • What is selective permeability in membranes?
    Membranes allow some substances to cross more easily than others based on size, charge, polarity, and presence of transport proteins.
  • Difference between integral and peripheral membrane proteins?
    Integral proteins span the lipid bilayer and interact with its hydrophobic core; peripheral proteins are loosely attached to the membrane surface.
  • Functions of membrane proteins?
    Transport, enzymatic activity, signal transduction, cell-cell recognition, intercellular joining, and attachment to cytoskeleton and ECM.
  • What role do membrane carbohydrates play?
    Carbohydrates attached to lipids or proteins serve as molecular identity tags for cell recognition and communication.
  • How does temperature affect membrane fluidity?
    Lower temperatures slow phospholipid movement, making membranes less fluid; unsaturated fatty acid tails help maintain fluidity by preventing tight packing.
  • What is passive transport?
    Movement of substances across membranes without energy input, down their concentration gradient.
  • What is osmosis?
    The net movement of water across a selectively permeable membrane toward the side with higher solute concentration.
  • Define tonicity and its types.
    Tonicity describes how a solution affects water movement into or out of a cell: isotonic (no net water movement), hypertonic (cell loses water), hypotonic (cell gains water).
  • What is facilitated diffusion?
    Passive transport aided by transport proteins like channel and carrier proteins that speed movement of specific molecules.
  • How does active transport differ from passive transport?
    Active transport moves substances against their concentration or electrochemical gradient using energy, often from ATP.
  • Describe the sodium-potassium pump.
    An active transport protein that moves 3 Na⁺ out and 2 K⁺ into animal cells per ATP hydrolyzed, maintaining essential ion gradients.
  • What is membrane potential?
    Voltage across a membrane caused by unequal distribution of ions, influencing movement of charged substances.
  • What are electrogenic pumps?
    Membrane proteins that generate voltage by moving ions, e.g., sodium-potassium pump in animals and proton pump in plants.
  • Explain cotransport.
    One substance moving down its gradient provides energy to move another substance against its gradient via linked transport proteins.
  • What is bulk transport?
    Active transport of large molecules or particles via vesicles, including exocytosis (out) and endocytosis (in).
  • What are the three stages of cell signaling?
    Reception (signal detection), transduction (signal conversion), and response (cellular activity triggered).
  • Describe G protein-coupled receptors (GPCRs).
    Membrane receptors that activate G proteins by exchanging GDP for GTP upon ligand binding, triggering cellular responses.
  • What is a ligand-gated ion channel?
    A receptor that opens an ion channel upon ligand binding, allowing ions to flow and rapidly change cell state.
  • Where are intracellular receptors found and what do they bind?
    Inside the cytoplasm or nucleus; they bind small hydrophobic ligands like steroid hormones to regulate gene expression.
  • What are second messengers?
    Small molecules or ions that relay signals inside the cell, amplifying the signal; examples include cAMP and Ca²⁺.
  • How does protein phosphorylation function in signaling?
    Kinases add phosphate groups to proteins in cascades, amplifying signals; phosphatases remove them to turn off signals.
  • What types of cellular responses can result from signaling?
    Changes in gene expression, enzyme activity, ion channel function, or cell movement.