Transcript nuclear region

Cells
Prokaryotic and Eukaryotic
Prokaryotes
• Prokaryotic cells have no “true” nucleus but
rather a nuclear “region”
• Typical prokaryotic components are:
– Capsule
– Cell wall
– Plasma membrane
– Cytoplasm (alt. cytosol)
– Pili (fimbriae)
– Flagella
– Ribosomes
– Nucleoid (nuclear region)
Prokaryotic Cell
Escherichia coli
(E. coli)
Result of Binary
Fission
Eukaryotic Cells
• More “evolved” cells
• Composed of:
– Nucleus
– Nucleolus
– Chromatin
– Nuclear Envelope
– Plasma Membrane
– Golgi Apparatus
– Lysosome
- Peroxisome
- Mitochondria
- Endoplasmic
Reticulum
- Ribosomes
- Microvilli
- Cytoskeleton
- Centrosome
Eukaryotic Cells
Organelle Structure & Function
• Nucleus
– Contains the genetic information of
the cell
– Surrounded by the nuclear envelope
– Nuclear pores lined with pore
complex protein
– Nuclear lamina maintains shape of
envelope
– Chromosomes contain chromatin;
DNA mixed with proteins
– Nucleolus synthesizes rRNA
• Proteins and rRNA make subunits of
ribosomes
• May function in cell division
Structure & Function
• Ribosomes
– Complex of rRNA and protein
– Present abundantly in cells active in protein synthesis
(i.e., pancreas, muscle, etc.)
– Sight of polypeptide assemblage
– Free and bound
– 70S and 80S ribosomes
• 70S in prokaryotes
• 80S in eukaryotes
– Mitochondria/Chloroplast 70S
Endoplasmic Reticulum
• Approximately ½ of total membrane in
eukaryotic cells
• Composed of cisternae or lumen
• Both smooth and rough endoplasmic
reticulum
Smooth Endoplasmic Reticulum
• Functions include
– Synthesis of lipids
• Oils, phospholipds and steriods
– Cells that secrete sex hormones
are rich in smooth ER (ovaries and
testicles)
– Metabolism of carbohydrates
– Detoxification of drugs and
poisons
• Liver cells add hydroxyl group for
water solubility
• Proliferation occurs with consistent
exposure
– Calcium storage in muscle
tissue
Rough Endoplasmic Reticulum
• Studded with Ribosomes
– Pancreatic cells synthesize
insulin on the ER
– Polypeptide chains enter lumen
of ER
• Bound to carbohydrates to form
glycoproteins
• Considered “Secretory Proteins”
• Secretory Proteins separated from
cytosol via transport vessicles
Golgi Apparatus
• Receiving center for vesicles from ER
• Plentiful in cells specialized for
secretion
• Cis face and trans face to “stack” due to
polarity difference
– Cis is receiving side of Golgi; trans is
shipping side
• ER products are enzymatically modified
between cis and trans sides
– Glycoproteins
– Monomers are removed and substituted
for large variety of carbs
– Membrane phospholipids also altered in
Golgi
• Polysaccharides (pectin and other cell
wall materials) synthesized directly by
the Golgi
• Targeting of products takes place
between cis and trans face via
molecular tags
Lysosome
• Sack of hydrolytic enzymes
– Enzymes made at Rough ER and refined at Golgi
• Lysosomes form from trans face of Golgi
Apparatus
• Engage in phagocytosis
• Lysosomes merge with food vacuoles in cells
and digest food
– Products then passed onto the cytosol
• Autophagy
– Damaged organelle surrounded by double membrane
– Lysosome fuses with membrane and digests
organelles
– Recycles raw materials back into cytosol
Vacuoles
• Food, contractile and central vacuoles
• Certain plants have vacuoles that act as
disposal sites for “toxic” metabolic
byproducts
• Others hold pigments that determine the
petal color of flowers
• Defense mechanism to make plant
unpalatable to animals
Mitochondria
• Site of cellular respiration
• Found in nearly all eukaryotic cells: plants, animals, fungi
and most protists
– Human parasites have organelles that may have evolved from
mitochondria
• Number of mitochondria correlates to level of metabolic
acitivty
• Mitochondria move, alter shape and divide
• Double phospholipid bilayer encases mitochondria
– Outside smooth; inside convoluted and forms “cristae”
– More folds create more efficiency
• Mitochondrial matrix is inside inner membrane
– Enzymes, mitochondrial DNA and ribosomes present here
• Some enzymes aid in cellular respiration
Chloroplasts
• Member of the plastid family
– Amyloplasts
• Contain chlorophyll and photosynthetic
enzymes
• Double membrane bound
• Three major components
– Thylakoids
– Granum
– Stroma (DNA and ribosomes)
Peroxisome
• Single membrane
• Transfers hydrogen to various molecules
to create H2O2 (some conversions are for
mitochondria)
– Enzymes within lysosome convert H202 to
water for expulsion from cell
• Glyoxysomes found in plant seed fat
tissue
– Converts fatty acids to sugar
Cytoskeleton
• Mechanical support and maintenance of
shape
• “Monorail” theory for movement within cell
• Three components of cytoskeleton
– Microtubles
– Micorfilaments
– Intermediate filaments
Microtubules
• Hollow tube 25 nm in diameter
• Composed of tubulin protein
– Dimer: composed of two subunits
• Growth occurs by adding tubulin dimers
• “Plus end” is the more active of two microtubule
ends
• Functions include
– Guiding secretory vesicles from Golgi
– “Beating” of cilia and flagella
– Separate chromosomes during cell division
• Form from centrosome (near nucleus)
– Centrioles located here
Microfilaments
• Composed of actin (globular protein)
– Twisted chain with branching ability
• Function in specialized cells that pull
materials across plasma membrane
(microvilli)
• Play a major role in cell motility (think
muscle cells and clevage furrows)
Intermediate Fibers
• Form the “permanent” framework for the
cell
• Much more of a structural molecule than
microtubules and microfilaments
– Nuclear lamina
– Nucleus
– Nerve cell strength