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AP Biology: Cell Structure & Function
20 AP Biology flashcards on Cell Structure and Function: prokaryotic and eukaryotic cells, organelles, membrane transport, tonicity, water potential and compartmentalization.
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Where is the DNA in a prokaryotic cell?
In the nucleoid region — usually one circular chromosome, with no nuclear membrane.
Where is the DNA in a eukaryotic cell?
Mostly in a nucleus enclosed by a nuclear envelope, as linear chromosomes.
What does it mean that the plasma membrane is selectively permeable?
It lets some substances cross freely while restricting or controlling others.
What do ribosomes do?
Build proteins by translating mRNA; they sit free in the cytoplasm or on the rough ER.
What does the rough ER do?
Makes proteins for secretion, membranes and lysosomes, using its bound ribosomes.
What does the smooth ER do?
Makes lipids, detoxifies drugs and poisons, and stores calcium ions.
What does the Golgi apparatus do?
Modifies, sorts and packages proteins and lipids from the ER and ships them on.
What happens in mitochondria?
Aerobic cellular respiration, which makes most of the cell's ATP; the folded inner membrane forms cristae.
What evidence supports the endosymbiotic origin of mitochondria and chloroplasts?
Their own circular DNA, bacteria-like ribosomes, double membranes and division by fission.
What do lysosomes do?
Digest macromolecules, worn-out organelles and engulfed material with hydrolytic enzymes.
What is osmosis?
Diffusion of water across a membrane from lower to higher solute concentration, often through aquaporins.
What is facilitated diffusion?
Passive transport of ions or polar molecules down their gradient through specific membrane proteins.
What is active transport?
Moving substances against their concentration gradient using energy, usually ATP, and a transport protein.
What does the plant cell wall do?
Supports the cell and resists bursting from water uptake; it is made mainly of cellulose.
Why does surface-area-to-volume ratio limit cell size?
Volume grows faster than surface area, so a large cell cannot exchange materials fast enough.
What are plasmodesmata?
Channels through plant cell walls that connect the cytoplasm of neighboring cells.
What are the three parts of the cytoskeleton?
Microtubules, microfilaments (actin) and intermediate filaments.
What happens to an animal cell placed in a hypotonic solution?
Water moves in by osmosis, so the cell swells and may burst; a plant cell becomes turgid instead because its wall resists.
What does water potential predict?
The direction water moves: from higher (less negative) water potential to lower (more negative) water potential.
Why does compartmentalization benefit eukaryotic cells?
Internal membranes separate incompatible reactions and concentrate enzymes and substrates, which makes processes more efficient.