Cytoskeleton & Cell Wall
Microfilaments are made of what protein?
Actin.
Which organelle makes ATP?
Mitochondria (“powerhouse”).
Diffusion moves molecules from ___ to ___.
High concentration → low concentration.
What do all cells have in common, regardless of type?
All cells share four features: (1) a plasma membrane to separate inside from outside, (2) cytoplasm where cell activities occur, (3) ribosomes to make proteins, and (4) genetic material (DNA or RNA) that carries instructions for life.
What is the main structure of the plasma membrane?
Phospholipid bilayer with hydrophilic heads facing out/in and hydrophobic tails inside.
Microtubules are made of what protein?
Tubulin.
Where are proteins made?
Ribosomes (cytoplasm or rough ER).
Define osmosis.
Diffusion of water across a selectively permeable membrane.
Give an example of a prokaryotic organism and a eukaryotic organism.
Prokaryote: Escherichia coli (bacterium). Eukaryote: Amoeba (protist) or Saccharomyces cerevisiae (yeast).
What does cholesterol do in the membrane?
Stabilizes fluidity: prevents too rigid (cold) or too fluid (hot).
What do intermediate filaments provide?
Mechanical strength & stability.
What organelle modifies and ships proteins?
Golgi apparatus.
What happens to a red blood cell in a hypertonic solution?
Water leaves → cell shrinks (crenation).
Name two main differences between prokaryotic and eukaryotic cells.
Prokaryotes lack a nucleus and membrane-bound organelles, while eukaryotes have both.
Difference between glycolipids and glycoproteins?
Glycolipids = sugar + lipid (cell recognition). Glycoproteins = sugar + protein (receptors, signaling).
Compare cilia vs. flagella.
Cilia = short, many, move fluid. Flagella = long, few, move whole cell.
Name 3 features unique to plant cells.
Chloroplasts, large central vacuole, cell wall.
Name the 3 types of endocytosis.
Phagocytosis (solids), Pinocytosis (liquids), Receptor-mediated (specific).
What is endosymbiosis theory?
Explains that mitochondria & chloroplasts were once free-living prokaryotes engulfed by early eukaryotes.
Why is the membrane selectively permeable?
Allows some molecules (O₂, CO₂, small nonpolar) while restricting others, requiring channels or energy.
Compare cell walls in plants, fungi, and bacteria.
Plants = cellulose; Fungi = chitin; Bacteria = peptidoglycan.
Trace the path of a secreted protein.
Ribosome (RER) → Golgi → vesicle → plasma membrane → exocytosis.
Compare passive vs. active transport.
Passive = no energy, down gradient (diffusion, osmosis). Active = requires ATP, against gradient (Na⁺/K⁺ pump, endocytosis).
Give one piece of evidence supporting endosymbiosis.
Mitochondria & chloroplasts have their own DNA and ribosomes.
What is the fluid mosaic model?
Describes the cell membrane as a flexible, dynamic structure with phospholipids, proteins, cholesterol, and carbohydrates moving within the bilayer.