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Terms & Concepts, Week 2
cell — basic structural & functional unit of organisms (some are unicellular, others are multicellular}
Hooke's observations (“cells" in cork)
the Cell Theory:
-organisms are built of celis
-cells come from preexisting cells
plant cell (= protoplast + cell wall)
cell wal! — “shell” around each cell
protoplast (= cytoplasm + nucleus)
cytoplasm -- a mixture of:
-membranes
-organelles
-cytoplasmic ground substance (a watery fluid)
plasma membrane — outer boundary of protoplast; controls what moves in & out of protoplast
nucleus — “contro! center’ containing DNA (genes)
nuclear envelope {with pores)
chromatin (DNA + proteins in nucleus)
chromosomes - form from chromatin during cell division
nucleolus — round structure inside nucleus; makes ribosomes
vacuole — a fluid-filled sac, like a water balloon; usually the largest structure in @ plant cell
functions: support; growth; waste repository; pigmentation of some cells
tonoplast — the membrane of a vacuole
ribosomes — site of protein synthesis
Endoplasmic Reticulum or ER (rough, smooth) — parallel sheets (or tubes) of membrane
functions: conduit for movement of materials; reaction surface; ribosome attachment
Golgi body (dictyosome) — “packaging center”
vesicle -- small balioon-like package of material
plastids — complex organelles found in plants & algae
-chioroplast — contains chlorophyll; site of photosynthesis
-chromoplast — contains other pigments
-leucoplast — lacks pigments
mitochondrion — “powerhouse” of cell; site of aerobic respiration
plastids & mitochondria are semi-autonomous, with their own DNA & ribosomes
microtubules — tiny, hollow fibers of protein
flagella & cilia — tiny hair-like structures some cells have for locomotion; made of microtubules
spindle fibers — form during cell division; made of microtubules
chemical composition of cell wall
cellulose (a polymer of glucose) fibers
polymer — large, chain-like molecule made of repeating subunits (monomers)
matrix of cell wall (between cellulose fibers)
hemicellulose
pectic substances or pectin — glue-like gel; holds water
waxes (waterproofing)
lignin — hard, rigid material
proteins
primary (1°) cell wall — formed while a cell is still growing in size — contains pectic substances
secondary (2° } cell wall -— formed after a cell has stopped growing — often thick, rigid (no pectin)
pits — gaps in 2° wall
middle !amella — “glue” (pectic substances) between adjacent celis, cementing together their cell walls
plasmodesmata — cytoplasmic “channels” between adjacent plant cells, containing ER
plant vs. animal cell (How do their contents differ?)
