Cell Theory & Cell Types
What are the three principles of the Cell Theory?
All organisms are made of cells, all cells come from pre-existing cells, and the cell is the basic unit of life.)
What is the main structural component of the plasma membrane?
Phospholipid bilayer.)
What organelle is known as the “powerhouse of the cell,” and why?
(Mitochondria; they generate ATP through cellular respiration.)
Which two organelles are involved in energy conversion?
(Mitochondria and chloroplasts.)
What are the three main components of the cytoskeleton?
(Microfilaments, intermediate filaments, microtubules.)
Which type of microscope is best for viewing detailed internal structures of cells?
Transmission Electron Microscope—TEM.)
How do prokaryotic and eukaryotic cells differ in structure?
(Prokaryotes lack a nucleus and membrane-bound organelles; eukaryotes have both.)
How do hydrophilic and hydrophobic regions of phospholipids affect membrane function?
Hydrophilic heads interact with water; hydrophobic tails create a selective barrier.)
What structure controls what enters and exits the nucleus?
Nuclear envelope with nuclear pores.
How does the endosymbiotic theory explain the origin of mitochondria and chloroplasts?
(They originated from prokaryotic cells that were engulfed by an ancestral eukaryotic cell.
What cytoskeletal structure helps move chromosomes during cell division?
Microtubules—form the spindle fibers
How can researchers use fluorescent markers in studying cell function?
They tag specific proteins or organelles to visualize their location and movement.)
Why are smaller cells more efficient than larger cells?
Higher surface area-to-volume ratio allows for more efficient exchange of materials.)
How do small, nonpolar molecules like oxygen and carbon dioxide cross the membrane?
(Simple diffusion.)
Why are ribosomes found both free in the cytoplasm and attached to the rough ER?
Free ribosomes make cytoplasmic proteins; ER-bound ribosomes make proteins for secretion or membranes
What evidence supports the endosymbiotic theory? Name two pieces of evidence
Both mitochondria and chloroplasts have their own DNA and ribosomes, similar to bacteria.)
How do motor proteins like dynein and kinesin contribute to intracellular transport?
(They “walk” along microtubules to move vesicles and organelles inside the cell.)
Why are HeLa cells significant in cell biology research?
(They were the first immortal human cell line used for medical and scientific discoveries.)
Some cells, like neurons, are long and thin instead of spherical. How does this help overcome size limitations?
(Increases surface area without significantly increasing volume, improving material exchange.)
How do facilitated diffusion and active transport differ?
Facilitated diffusion moves substances down their gradient with no energy; active transport moves them against their gradient using ATP.)
How does the Golgi apparatus function in protein processing?
Modifies, sorts, and packages proteins for transport inside or outside the cell.)
How does the structure of the inner mitochondrial membrane maximize ATP production?
(Folds (cristae) increase surface area for more ATP-generating reactions.)
Cilia and flagella are made of microtubules. How do they differ in function?
Cilia move substances across a cell’s surface; flagella move the entire cell.)
scientist uses centrifugation to separate organelles by density. In what order would they be isolated?
Nucleus → Mitochondria/Chloroplasts → Ribosomes/Microsomes.)
A scientist discovers a new cell with a cell wall, ribosomes, and circular DNA but no membrane-bound organelles. What type of cell is it?
Prokaryotic—likely a bacterium or archaean.)
Cholesterol is found in animal cell membranes. What role does it play?
Regulates membrane fluidity—prevents rigidity in cold temperatures and excessive fluidity in heat.)
A disease prevents the breakdown of cellular waste and leads to toxic accumulation inside cells. What organelle is most likely defective?
(Lysosomes.)
Some poisons block the electron transport chain in mitochondria. What effect would this have on a cell?
(ATP production would stop, leading to cell death due to lack of energy.)
How does the structure of actin filaments allow them to contribute to cell shape and movement?
They are dynamic—can polymerize and depolymerize to push or pull parts of the cell.)
CRISPR technology is used to modify genes in cells. What part of the cell does CRISPR directly interact with?
(DNA in the nucleus.)