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Cells
Scientists
• Hooke-saw cork cells under a microscope
• Van Leeuweenhoek – saw living bacteria
• Pasteur – studied bacteria and developed the
germ theory that said that ‘germs’ cause
disease. He also developed the first vaccines.
• Koch – rules to test if a germ is the cause of a
specific disease
• Margulis – tested DNA in mitochondria and
found it was the same as bacteria DNA
Cell Theory
• All living organisms are composed of one
or more living cells
• Cells are the basic units of life
• All cells come from preexisting cells
Microscopes
• Compound Light Microscope – series of
glass lens that can be no better than
1000X, but can be used to view living cells
• Electron microscopes – aims a beam of
electrons at thin slices of cells (dead)
– Transmission electron microscope (TEM)
– Scanning electron microscope (SEM)
Microscopes
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
Cell Size
Cell Size
Basic Cell Types
• Prokaryotes – cells without a nucleus or
other membrane bound organelles
– Example: most unicellular organisms, e.g.,
bacteria
• Eukaryotes – cells with a nucleus and
other membrane bound organelles (ER,
mitochondria, Golgi apparatus,
chloroplast, lysosome)
Plasma Membrane
The Lipid Bilayer
• Lipids of the bilayer
– fluid or liquid-crystalline state
• Proteins move within the membrane
Hydrophilic
region of protein
Hydrophobic
region of protein
Phospholipid
bilayer
Peripheral
protein
Integral
(transmembrane)
protein
(b) Fluid mosaic model. According to this model, a cell
membrane is a fluid lipid bilayer with a constantly changing
“mosaic pattern“ of associated proteins.
Fig. 5-2b, p. 108
Cytoplasm
• Environment inside cell membrane
• Cytoskeleton – supporting network of long,
protein fibers that form a network and
anchor for the cell organelles
Membrane structure
• Phospholipids~ membrane fluidity
• Cholesterol~ membrane
stabilization
• “Mosaic” Structure~ proteins
• Membrane carbohydrates ~ cell
to cell recognition;
Nucleus
• Genetic material...
•chromatin
•chromosomes
• Nucleolus:; ribosome synthesis
• Double membrane envelope
with pores
• Protein synthesis
Ribosomes
• Protein manufacture
Endomembrane system, I
• Endoplasmic reticulum (ER)
• Smooth ER
•no ribosomes;
•synthesis of lipids
• Rough ER
•with ribosomes;
•synthesis of proteins
Endomembrane system, II
• Golgi apparatus
– •ER products are modified, stored, and then shipped
Endomembrane system, III
• Lysosomes
•sac of hydrolytic
enzymes; digestion of
macromolecules
• Tay-Sachs disease~
lipid-digestion
disorder
Other membranous organelles, I
• Mitochondria
• quantity in cell
correlated with
metabolic activity;
•cellular respiration
•contain own DNA
Other membranous organelles,
II
• Chloroplast (doubled membranous plastid)
•photosynthesis
•own DNA
Peroxisomes
• Metabolism of fatty
acids; detoxification of
alcohol (liver)
Cellular Transport
• Passive Transport – does not require energy
– Diffusion
– Across a membrane
• Osmosis
• Facilitated diffusion
• Active Transport – requires energy
– Sodium/Potassium pump
– Transport of Large Particles
• Endocytosis
• Exocytosis
Diffusion
Osmosis
Water balance
• Osmoregulation~
control of water balance
• Hypertonic~ higher
concentration of solutes
• Hypotonic~ lower
concentration of solutes
• Isotonic~ equal
concentrations of solutes
•
•
•
•
Cells with Walls:
Turgid (very firm)
Flaccid (limp)
Plasmolysis~ plasma
membrane pulls away from
cell wall
Turgor and
Plasmolysis
Facilitated Diffusion
Types of Active Transport
• Sodium-potassium pump
• Exocytosis~ secretion of
macromolecules by the fusion
of vesicles with the plasma
membrane
• Endocytosis~ import of
macromolecules by forming
new vesicles with the plasma
membrane
•phagocytosis
•pinocytosis
2. Phosphate group is
transferred from ATP
to transport protein.
3. Phosphorylation
causes carrier protein
to change shape, releasing
3 Na+ outside cell.
1. Three Na+ bind
to transport protein.
4. Two K+ bind to
transport protein.
6. Phosphate release causes 5. Phosphate is released.
carrier protein to return
to its original shape. Two
K+ ions are released inside
cell.
Fig. 5-17b, p. 121
Phagocytosis
Large particles enter cell