Cells
Structural and functional units of living organisms
Eukaryotic (“true nucleus”) vs. Prokaryotic (“before
nucleus”) cells
Proks - nucleoid is not separated from cytoplasm by a
membrane
Euks - nuclear material is enclosed in a double membrane nuclear envelope
Prokaryotic vs. Eukaryotic Cells
Prokaryotic vs. Eukaryotic Cells
Changes from Proks to Euks:
(1)
DNA size and compactions
(2)
Cell size and organization
(3)
Early euk cells were endosymbiotic
Development of Eukaryotic Cells
Prokaryotic (bacterial) Cell
Prokaryotic Cells
Two groups:
Archaebacteria
Eubacteria
recently discovered
live in extreme environments (salt
lakes, hot springs, deep in ocean)
most common
well-studied (Escherichia coli/E. coli)
inhabit soil, surface water, organisms
Eukaryotic Cell
Animal cell
Plant cell
Eukaryotic Cell
Plasma membrane
Eukaryotic Cell
Plasma membrane
Eukaryotic Cell
Endoplasmic Reticulum (ER)
Membrane-enclosed compartments
Extends through cytoplasm
Flattened branches = cisternae
Smooth ER (lipid biosynthesis, drug metabolism)
- Ribosome free
Rough ER (LOTS OF PROTEIN SYNTHESIS) Ribosomes attached
ALSO free ribosomes - synthesize proteins that
will remain in cytosol
Eukaryotic Cell
Golgi Complex
Membrane-enclosed compartments
Extends through cytoplasm
Flattened branches = cisternae
Site of processing, packaging and targeting of
proteins
Modifications - sulfate, carbohydrate, lipids, etc.
Modification tags protein for its destination
Eukaryotic Cell
Lysosomes
Animal cells only
Contain enzymes that digest proteins,
polysaccharides, nucleic acids, lipids
Enzymes kept inside by membrane
Lysosome pH ATP-fueled proton pump keeps pH in lysosome at
~5.0 rather than 7.0 (in cytosol)
Enzymes within lysosome act best at lower pH
Eukaryotic Cell
Peroxisomes
Purpose - take up reactive chemical species that
could otherwise damage cell machinery
Example: H2O2
Catalase
2H2O2 --> 2H2O + O2
Catalase at high concentration in peroxisome
Eukaryotic Cell
Nucleus
Contains cellular DNA (some DNA in mitochondria and
chloroplast)
Eukaryotic Cell
Nucleus
Chromosomes = 2 chromatids
Chromatin mass = 50%
DNA, 50% histones
DNA of single human
chromosome forms
~1,000,000 nucleosomes
Eukaryotic Cell
Most cells (somatic cells) have 2 copies of each chromosome
Gametes, germline cells (egg and sperm) have only 1 copy of
each chromosome
Eukaryotic Cell
Mitochondria
Diameter of ~1 µm (bacterial cells)
100s-1000 per cell
Metabolic cells have more mitochondria
Matrix has lots of enzymes and metabolic intermediates
Have their own DNA, RNA and ribosomes
Descendants of aerobic bacteria??
Eukaryotic Cell
Cytoskeleton
Meshwork through cytoplasm
Provides structure and organization to cytoplasm and shape to
cell
Viruses = Parasites of Cell
Viruses
Replicate themselves in host cells
Contain DNA or RNA surrounded by a capsid (protective coat)
Outside host cell, virus is nonliving particle (virion)
Inside host cell, virus is parasite
Uses host cells’ machinery to make more virus particles
Turnip yellow mosaic virus (spheres)
Tobacco mosaic virus (cylinders)
Bacteriophage T4
HIV
Poliovirus
Skeletal muscle cell
Red blood cells
Secretory cells
of pancreas
Sperm cells
Human embryo at
2-cell stage