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AP Bio Ch. 6.5 - 6.6
Mitochondria and chloroplasts have two defining features in common: they both have two membranes separating their interior from the cytosol, and they contain their own DNA and ribosomes. They are not part of the endomembrane system because they predate its evolution and were originally independent prokaryotic cells that became incorporated into eukaryotic cells via endosymbiosis. Mitochondria provide energy for the cell through respiration while chloroplasts perform photosynthesis.
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AP Bio Ch. 6.5 - 6.6
- 1. Mitochondria, Chloroplasts, Peroxisomes, &the Cytoskeleton 6.5-6.7
- 2. Mitochondria & Chloroplastsare special… Not part of the endomembrane system because… They both have 2 membranes separating their insides from the cytosol Have their own ribosomes Contain small amounts of their own DNA to make some of their own membrane proteins Grow and reproduce independently of the cell
- 3. Mitochondria Found in eukaryoticcells of plants, animals, fungi, and protists More active cells have more mitochondria Very small - ~ 1-10 microns
- 4. Structure of Mitochondria 2membranes Smooth outer membrane Convoluted inner membrane Folds called cristae This membrane creates 2 spaces inside the mitochondrion Space between outer & inner membrane = intermembrane space Space inside inner membrane = matrix Matrix has enzymes , DNA, ribosomes Lots of folds means lots of membrane surface for cell respiration to occur
- 5. Chloroplasts One of afamily of plant organelles called plastids Amyloplast – store starch Chromoplast – pigments that color fruits and flowers Chloroplast – contain the pigment chlorophyll & enzymes for photosynthesis Very small ~ 2 microns Found in green parts of plants
- 6. Structure of Chloroplasts Double membrane with narrow intermembrane space Inside is second membrane system – flattened discs called thylakoids Stacks of thylakoids are called grana Fluid inside grana called stroma Stroma contains DNA, enzymes for photosynthesis, ribosomes
- 7. Quick Think Describe atleast 2 things that mitochondria and chloroplasts have in common. Explain why mitochondria and chloroplasts are not part of the endomembrane system.
- 8. Peroxisomes Single membrane Contain enzymes that transfer hydrogen from other molecules to oxygen to produce H2O2 as a by-product. Contains enzymes that then break down H2O2 into water.
- 9. Peroxisomes Many different functions Someare used to break down fatty acids Those in the liver detoxify alcohol
- 10. The Cytoskeleton Cytoskeleton -a network of fibers that runs through the cell Helps organize the inside of the cell Made up of 3 types of tubes: Microtubules Microfilaments Intermediate filaments
- 11. Cytoskeleton Functions Supports cell Maintainscell shape (important for animal cells since no cell wall) Can be dismantled and reformed quickly so cells can change shape
- 12. Cytoskeleton Function Aides incell motility -2 types of motility: Whole cell movement - the cytoskeleton interacts with motor proteins to allow the cell to move along fibers outside the cell Movement of organelles and vesicles within the cell - internal parts move along filaments of cytoskeleton Sperm around an egg
- 13. Cytoskeleton Structure Microtubules -thickest Microfilaments - thinnest (aka actin filaments) Intermediate filaments - mid sized
- 14. Microtubules Hollow Made of aprotein called tubulin Give shape & support to cell Allows for organelles to move along them Separate chromosomes during cell division Grow out of centrosomes in many cells
- 15. Cilia & Flagella Specialized arrangement of microtubules makes flagella & cilia beat Internal structure of both the same Core of microtubules surrounded by plasma membrane 9 doublets of microtubules arranged in a ring Wagon wheel proteins that connect each doublet Motor proteins between each doublet Whole thing anchored to cell at the basal body
- 16. Cilia & Flagella Flagellaon sperm Cilia on cells in the throat move mucus along Cilia in reproductive tract of females moves egg toward uterus Lots of unicellular eukaryotes use cilia and flagella for movement in aquatic environments
- 17. Microfilaments (Actin Filaments) Solid Built froma protein called actin Help support cell’s shape Have an important role in muscle contraction
- 18. Intermediate Filaments Specialized forbearing tension Made up of keratin proteins More diverse than the other 2 More permanent than the other 2 Skin is dead cells full of keratin proteins Keep certain organelles, like nucleus, locked in place Maintain shape of cell, especially odd shapes like neurons
- 19. Quick Think –complete the table Main features Main functions Microtubules Hollow, thickest, tubulin support for cell, organelles move along it’s tracks, cilia & flagella Microfilaments Thinnest, solid actin Support cell shape, muscle contraction Intermediate filaments In between size, diverse structure, more permanent, keratin Lock certain organelles in place, maintain irregular cell shapes
- 20. Quick Think There aremany different cell types, even within the same organism. Cells vary in size, shape, structure, and function. This is part of the diversity of life. Which aspects of cells best reveal their evolutionary unity? What are some examples of specialized cellular modifications?