Ch 3 Cells, Membranes, and Homeostasis - Vocabulary Flashcards

Ch 3.1 Cell Theory

• 1665: Hooke observed cells via microscope; microscopy reveals cellular world.

• Cell Theory (three principles):

  • 1) All organisms are made up of cells

  • 2) The cell is the fundamental unit of life

  • 3) Cells come from preexisting cells

• Structure–Function examples:

  • Red blood cells: biconcave shape increases surface area for gas exchange and aids passage through capillaries

  • Neurons: long extensions enable cell-to-cell communication

  • Multinucleated muscle cells: specialized for contraction

  • Microvilli on intestinal cells: increase absorptive surface area

Ch 3.2 Structure of Cell Membranes

• Major lipids: phospholipids; amphipathic with hydrophilic heads and hydrophobic tails

• Lipid structures: micelle, bilayer, liposome; bilayer forms spontaneously in water

• Membranes = fluid mosaic of lipids and proteins; lateral movement; tail saturation and cholesterol affect fluidity

• Saturated vs unsaturated tails:

  • Saturated tails pack tightly; unsaturated tails with kinks reduce packing

  • Van der Waals interactions help stabilize membranes

• Cholesterol: modulates membrane fluidity; more cholesterol generally reduces fluidity (temperature dependent)

• Proteins:

  • Integral (transmembrane) proteins span the membrane

  • Peripheral proteins associate with membrane surfaces

• Fluid Mosaic evidence: FRAP shows proteins move laterally within the membrane

Ch 3.3 Membrane Transport

• Plasma membrane defines cell boundary and maintains homeostasis via selective permeability

• Membrane Transport Flowchart (summary):

  • Passive processes: no cellular energy required; substances move down their concentration gradient

  • Diffusion: small nonpolar molecules (simple diffusion)

  • Osmosis: movement of water across a semipermeable membrane

  • Facilitated diffusion: requires transport proteins (channel-mediated or carrier-mediated)

  • Active processes: require cellular energy; substances move up their gradient or via vesicles

  • Primary active transport: energy from ATP (e.g., Na+/K+ pump)

  • Secondary active transport: energy from movement of another substance (gradients)

  • Vesicular transport: exocytosis (secretion) and endocytosis (uptake)

• Na+/K+ pump (primary active transport): uses ATP to move ions against their gradients

  • Example: moves 3 Na+ out and 2 K+ in per ATP hydrolyzed

• Osmosis: water moves from low solute concentration to high solute concentration

• Simple diffusion: small nonpolar molecules diffuse without transport proteins

• Facilitated diffusion: ions or polar molecules diffuse via channels or carriers

  • Channel-mediated diffusion: ions move through channels

  • Carrier-mediated diffusion: polar molecules moved by carrier proteins

• Endocytosis types:

  • Phagocytosis (cellular eating)

  • Pinocytosis (cellular drinking)

  • Receptor-mediated endocytosis

Ch 3.4 The Endomembrane System

• The endomembrane system partitions the cell into functional spaces via interconnected membranes and vesicles

• Key components and roles:

  • Nuclear envelope: double membrane with nuclear pores; large molecules require active transport

  • Endoplasmic reticulum (ER): rough ER—protein synthesis; smooth ER—lipid synthesis

  • Golgi apparatus: modifies and sorts proteins and lipids for final destinations

  • Lysosomes: degrade damaged macromolecules

  • Peroxisomes: break down fatty acids and synthesize other molecules

  • Vesicles and plasma membrane: traffic between compartments and cell exterior

• Exocytosis and endocytosis: vesicles fuse with or bud from membranes to move materials

• Plant-specific features (context): cell wall; plasmodesmata; vacuoles contributing to turgor and structuring

Ch 3.5 Mitochondria and Chloroplasts

• Mitochondria:

  • Double membrane (outer and inner); inner membrane folds form cristae

  • Site of ATP production by harvesting energy from chemical compounds (e.g., sugars)

• Chloroplasts:

  • Double membrane with an inner thylakoid membrane system

  • Capture light energy to fix atmospheric carbon and synthesize simple sugars

• Key idea: organelles specialize in energy capture and conversion to power the cell

Plant vs. Animal Cells

• Shared features: nucleus; endomembrane system; ribosomes; mitochondria; cytoskeleton; plasma membrane; peroxisomes

• Plant cell features: cell wall; chloroplasts; large central vacuole; plasmodesmata

• Animal cell features: lysosomes common; lacks cell wall; different vacuolar systems