Date post: | 13-Dec-2015 |
Category: |
Documents |
Upload: | rosanna-lambert |
View: | 219 times |
Download: | 0 times |
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)
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
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)