Chapter 3 Flashcards
(50 cards)
State the three statements of the Cell Theory
- A cell is the smallest unit of life. 2. All living things are composed of one or more cells. 3. New cells arise only from pre-existing cells.
Prokaryotic vs. Eukaryotic cell – four key differences
Prokaryote: no nucleus, no membrane-bound organelles, 1–10 µm, circular DNA. Eukaryote: true nucleus, many membrane organelles, 10–100 µm, linear chromosomes.
Why does compartmentalization make eukaryotic cells more efficient?
Membrane-bound organelles isolate incompatible reactions, concentrate enzymes/substrates, shorten diffusion distances, and allow simultaneous, specialized processes.
Define surface-to-volume ratio and explain cell-size limits
S/V = cell surface area ÷ volume. As a cell grows, volume rises faster than surface, lowering S/V; this slows nutrient/waste exchange → cells remain small or become long/flat/microvilliated.
Structure of the plasma membrane (fluid mosaic model)
Phospholipid bilayer (hydrophilic heads, hydrophobic tails) + embedded proteins, cholesterol (fluidity), glycolipids & glycoproteins (‘sugar coating’). The mosaic is fluid because most components drift laterally.
Five functions of the plasma membrane
- Maintain structural integrity 2. Selectively regulate transport 3. Cell–cell recognition (glycoproteins) 4. Cell signaling (receptors) 5. Cell adhesion (CAMs, junctions).
Selective permeability definition & benefit
Membrane allows some substances (O₂, CO₂, small lipids) to cross freely, others via proteins, and blocks many toxins → protects internal composition/homeostasis.
Role of cholesterol in the bilayer
Inserts between phospholipids, preventing solidification at low T°, restraining excess fluidity at high T°, stabilizing membrane.
Cell Adhesion Molecules (CAMs)
Trans-membrane glycoproteins that ‘velcro’ neighboring cells, guide cells during embryonic development and healing, and form tissues/organs.
Simple diffusion vs. facilitated diffusion
Simple: movement of small non-polar molecules (O₂, CO₂) down gradient through lipid bilayer. Facilitated: polar/charged solutes move down gradient through channel or carrier protein; no ATP.
Active transport definition + example
Carrier protein uses ATP to pump solute against gradient (e.g., Na⁺/K⁺ pump exchanges 3 Na⁺ out / 2 K⁺ in).
Define osmosis
Net movement of water across a selectively permeable membrane from higher water potential (lower solute) to lower water potential (higher solute).
Hyper- vs. iso- vs. hypotonic external solutions & RBC outcome
Hypertonic: H₂O exits → crenation. Isotonic: no net change. Hypotonic: H₂O enters → hemolysis.
Endocytosis vs. exocytosis
Endo-: membrane engulfs material → vesicle inside. Exo-: vesicle fuses with membrane → releases contents outside. Both require ATP & cytoskeleton.
Phagocytosis vs. pinocytosis
Phago: ‘cell eating’ of large particles/bacteria by pseudopods. Pino: ‘cell drinking’ bulk uptake of extracellular fluid and solutes.
Nucleus – 3 key structures & functions
Nuclear envelope (double membrane w/ pores – traffic control); nucleolus (rRNA & ribosome assembly); chromatin/chromosomes (DNA + histone proteins – genetic blueprint).
Free vs. bound ribosomes – what do they make?
Free (cytosol): proteins for cytosol & nucleus. Bound (on RER): proteins for membranes, lysosomes, secretion.
Rough ER (RER) – structure & role
Flattened sacs studded w/ ribosomes; folds & modifies nascent polypeptides, begins glycosylation, produces membrane.
Smooth ER (SER) – 3 major functions
Lipid & steroid synthesis, detoxification (liver), Ca²⁺ storage (muscle). No ribosomes.
Golgi complex workflow
‘Receiving’ face accepts RER vesicles → enzymes modify (glycosylate, trim) proteins/lipids → ‘shipping’ face buds vesicles to plasma membrane, lysosomes, or secretion.
Lysosome structure & purpose
Single-membrane vesicle w/ ~40 acid hydrolases active at pH ≈ 5; digests phagocytosed particles & worn-out organelles (autophagy).
How lysosomal storage diseases arise
Inherited absence of a specific lysosomal enzyme → undegraded substrate accumulates → lysosome swells, cell function declines.
Tay-Sachs disease in one sentence
Absence of Hex-A enzyme → GM₂ ganglioside lipids accumulate in neurons → progressive neurodegeneration, death by ~age 4.
Mitochondrion anatomy
Outer membrane, highly folded inner membrane (cristae), inter-membrane space, matrix (enzymes, ribosomes, circular DNA). Site of most ATP production.
