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CELLS!
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Cytology= the study of cells
Viewed a slice of cork and thought the tiny boxes looked like the rooms that monks lived in… so he named them “cells”.
Microscopes opened up the world of cells
The 1st cytologist– Robert Hooke (1665)
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Microscopes
Light microscopy- magnification ~ ratio of image size to real size - resolution ~ measure of clarity
Electron microscopy
- TEM~ (transmitting) electron beam to study cell ultrastructure
- SEM~ (scanning) electron beam to study cell surfaces
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An electron microscope
Grasshopper Spider
Images:
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Isolating Organelles
Cell fractionation– separate organelles from others in the cell– variable density of organelles (heaviest fall
out first)– ultracentrifuge
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Cell Theory
All organisms are made up of cells
The cell is the basic living unit of organization for all organisms
All cells come from pre-existing cells
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What makes a cell a cell?
All cells:– surrounded by a plasma membrane– have cytosol (semi-fluid substance within the
membrane)– cytoplasm = cytosol + organelles– contain chromosomes (have genes in the form of
DNA)– have ribosomes (tiny “organelles” that make
proteins using instructions contained in genes)
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Prokaryotic Cells
pro- before karyon- kernel (nucleus)
Nucleoid region: DNA concentration
No membrane-bound organelles
Bacteria cells
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Eukaryotic Cells
eu- true karyon- kernel (nucleus)
Larger than prokaryotes
Membrane-bound organelles
Plant and animal cells
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Cell Size As cell size increases,
the surface area to volume ratio decreases
Rates of chemical exchange may then be inadequate for cell size
Cell size, therefore, remains small
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Cell Size LimitsLower limit smallest bacteria, mycoplasmas
– 0.1 to 1.0 micron (μm = micrometer) most bacteria
– 1-10 microns
Upper limit eukaryotic cells
– 10-100 microns micron = micrometer =
1/1,000,000 meter diameter of human hair = ~20
microns
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Nucleus
Genetic material...– chromatin (proteins and DNA)– chromosomes (units of DNA–
humans have 46) Nucleolus: rRNA; ribosome
synthesis Nuclear envelope: double
membrane with pores and nuclear lamina (protein filaments for structure)
Directs protein synthesis (mRNA)
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Ribosomes
Protein manufacturing– Free- cytosol; protein function in cell– Bound- endoplasmic reticulum; membranes,
organelles, and export
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Endomembrane System
Synthesis of proteins, transport within and outside of cell
Parts involved:– Nuclear envelope– Endoplasmic Reticulum– Golgi apparatus– Lysosomes– Transport vesicles– Plasma membrane
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Endoplasmic Reticulum
Continuous with nuclear envelope Smooth ER
– no ribosomes– synthesis of lipids– metabolism of carbohydrates– detoxification of drugs and
poisons Rough ER
– with ribosomes– synthesis of secretory proteins
(glycoproteins), membrane production
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Golgi Apparatus ER products are modified, stored, and then shipped Cisternae: flattened membranous sacs
– Opposite sides have different thickness and polarity– cis face (receiving) & trans face (shipping)
Transport vesicles move modified materials to other parts of the cell
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Lysosomes
Sac of hydrolytic enzymes in animal cells
Digestion of macromolecules
Phagocytosis- cell eating Autophagy: recycle cell’s
own organic material (damaged organelles, etc.)
Tay-Sachs disease~ lipid-digestion disorder
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Vacuoles Membrane-bound sacs
(larger than vesicles) for storage and hydrolysis
May contain proteins, ions, pigments, sap, toxins, etc.
Special types– Food (created in
phagocytosis)– Contractile (pump excess
water in protists)– Central (storage in plants);
surrounded by tonoplast membrane