I. Cell theory
� major biological paradigm (Schleiden, botanist, 1838; Schwann, zoologist,
1839)
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organisms comprised of one or more cells
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cell basic unit of organization
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cells derived from other cells (Virchow, 1858)
II. Exceptions?
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fungi � filamentous, no cross walls; slime molds
� �blob-like� & multinucleate; virus
III. Cell size
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range from 100 nm (mycoplasmas)
→ BIG (bird eggs)
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typically small (5-40 μm)
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difference between big/small organisms is number
of cells, not cell size
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how many cells in the average human?
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Why aren�t cell larger? Or, what sets an upper
limit on size?
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maintain control
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maintain large surface/volume ratio � sa �
amounts of skin or outside; vol = amt guts; s/v = proportion of sa to
volume; as an object gets larger its s/v ratio decreases; e.g., cats &
buildings, parachutes, Goldilocks, ice
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important to maximize diffusion
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Why aren�t cells smaller? Or, what sets a lower
limit on size? Must be big enough to house necessary cellular machinery
(ribosomes, DNA, etc)
IV. Cells show unity &
diversity
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diversity � size, structure
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unity � share man common features
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strong evidence for evolution, evolved from
common ancestral cell
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cell theory � if cells derived from other cells,
must ultimately be one original cell
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some deductive logic � IF cells from other cells,
THEN cells must contain hereditary information that is passed from parent
cell to daughter cell (some consider this a fourth axiom of the cell theory)
V. Cells show
compartmentalization � organelles
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separates activities from other parts of cells
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allows incompatible reactions to occur (i.e.,
hydrophilic/hydrophobic)
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more efficient
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helps diffusion
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Factory Model
VI. Cell membrane
� gate keeper
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boundary, regulates entry/exit, cell
communication & recognition
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cytoplasm
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cytosol
VII. Nucleus
� the �brains�
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double membrane = TWO phospholipids bilayers
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pores, nucleoplasm
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chromatin = DNA; euchromatin, heterochromatin
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nucleolus
VIII. Mitochondrion
� cell powerhouse
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double membrane
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own DNA, RNA, ribosomes, divide by fission
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matrix/cristae � provides hydrophobic and
hydrophilic regions for two different types of reactions
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produces ATP via cellular respiration
IX. Plastids
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double membrane
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also have own DNA, RNA, ribosomes, divide by
fission
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thylakoids
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grana, stroma
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types: chloroplast � site of photosynthesis;
amyloplasts � store starch; chromoplast � store pigments other than
chlorophyll
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interconvert from one to the other
X. Ribosomes
� sites of protein manufacture
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site of protein synthesis
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2 subunits, one large, other small
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made in nucleus (nucleolus), subunits exported to
cytoplasm
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zip codes help tag and determine which way
materials transported
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2 subunits don�t assemble until begin making
protein
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ribosomes may be associated with ER or not
XI. Endoplasmic
Reticulum
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membrane sacs & tubes
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continous & interconnect with nuclear membrane &
plasma membrane
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rough � associated with ribosomes; smooth � no
ribosomes
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functions: support, transport (highway system),
membrane synthesis, synthesis of lipids, carbohydrates
XII. Golgi Body
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pita-like stack of membranes
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polarity � cis/trans
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shipping & processing center
XIII. Lysosomes
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membrane sacs
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contain hydrolytic enzymes � digest materials in
cells, recycling centers
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acidic pH (ca. 5)
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vesicles containing smaller cell or food particle
or macromolecules fuses with lysosome; damaged organelles surrounded by
membrane and fuse with lysosome
XIV. Peroxisomes
& glyoxisomes
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types of microbodies � single membrane, contain
catalase
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hydrogen peroxide generated during metabolism
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peroxisomes - common in leaf cells; remove
photosynthetic waste products
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glyoxisomes � common in seeds; metabolize fats in
seeds
XV. Endomembrane System
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Vacuoles & vesiciles � membrane sacs, plants with
large central vacuole
XVI. Cytoskeleton System
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roles: (a) structural support; (b) movement; (c)
maintain cell shape; (d) anchorage for cell components; (e) cytoplasmic
streaming
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Components of cytoskeleton assembled/disassembled
readily
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Three major components: microtubules,
microfilaments, intermediate filaments
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Microtubules � α and β tubulin; hollow,
assembled at one end, disassembled at other; involved in chromosomal
movements, structural support, resist compression
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Microfilaments � actin, twisted chain,
cytoplasmic streaming; resist pulling
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Intermediate filaments � keratin, braided
chains, resist pulling
XVII. Cell Movements
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via motor molecules; involve various proteins �
dynein (microtubules), kinesin (moves vesicles along microtubules)
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powered by ATP
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allow microtubules to slide past one another &
walk organelles along microtubules
XVIII.
Centrosome/Centriole
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centrosome � region near nucleus where
microtubules originate
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centrioles � 9+3 arrangement; 2 bundles at right
angles to one anther
XIX. Cilia/Flagella
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cilia � short, many, oarlike movement
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flagella � long, few, undulate, whiplike movement
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features: 9+2 arrangement, held by protein
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anchored by basal body (9+3)
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dynein arms
XX. Cell walls
(plants, fungi, bacteria)
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like a box that surrounds a water balloon
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wall essentially non-living
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initially formed during cell division, subsequent
additions by exocytosis, as wall gets thicker cell space gets smaller
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like a steel-belted radial tire; rubber matrix
with steel belts (cellulose in plants)
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cellulose; fungi � chitin; bacteria �
peptidoglycan
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many functions � protect, prevent cell from
bursting in hypotonic environment
XXI. Prokaryotic cells
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simple structure � cell membrane, cytoplasm,
ribosomes, few other organelles
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no nucleus, DNA in nucleoid region
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DNA large circular loop (a few linear chromosomes
aka eukarotes)
XXII Cell surface � ECM
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animal cells
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extracellular matrix
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cells essentially sugar-coated (& protein-coated)
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made of assorted CHO�s & proteins (collagen)
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integral proteins in membrane bind to collagen
via fibronectin
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helps cells adhere & cell recognition
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metastatic cancer � failure of cells to remain
attached
XXIII � Multicellularity
& Cell/Cell Connections
(not on exam, F07)
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multicellularity involved multiple times
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cells link together
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plants cells joined by middle lamella (�glue�)
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animal cells connected via:
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ECM
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tight junctions � fuse membranes, prevent
leakage
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desmosomes � like rivets, for strength;
cadherin proteins
XXIV. Cell/Cell
Communication (not on exam, F07)
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plants � plasmodesmata � cytoplasmic channels
through wall
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animals � gap junctions
XXV. Getting Materials
into/out of cells
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exocytosis/endocytosis
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diffusion/osmosis across membrane
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phagocytosis
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pinocytosis
XXVI. Comparison of
Eukaryotic vs. Prokaryotic cells �
complete table
XXVII. Comparison of
Plant & Animal cells � complete table