The Fundamental Units of Life Pt. 2
The Fundamental Units of Life Pt. 2 Biology 105
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This 4 page Bundle was uploaded by Ashley-Maria Farnen on Tuesday November 10, 2015. The Bundle belongs to Biology 105 at Indiana University of Pennsylvania taught by in Summer 2015. Since its upload, it has received 34 views. For similar materials see Cell Biology in Biology at Indiana University of Pennsylvania.
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Date Created: 11/10/15
Bio Notes Chapter 6, part 2 The Fundamental Units of Life Previous: a. The Evolutionary Origins of Mitochondria and Chloroplasts i. Mitochondria and chloroplasts have similarities with bacteria ii. Enveloped by a double membrane iii. Contain free ribosomes and circular DNA molecules iv. Grow and reproduce somewhat independently in cells. New: b. Mitochondria: Chemical Energy Conversion i. Mitochondria are in nearly all eukaryotic cells ii. They have a smooth outer membrane and an inner membrane folded into cristae iii. The inner membrane creates two compartments: intermembrane space and mitochondrial matrix iv. Some metabolic steps of cellular respiration are catalyzed in the mitochondrial matrix v. Cristae present a large surface area for enzymes that synthesize ATP c. Chloroplasts: Capture of Light Energy i. Chloroplasts contain the green pigment chlorophyll, as well as enzymes and other molecules that function in photosynthesis ii. Chloroplasts are found in leaves and other green organs of plants and in algae iii. Chloroplast structure includes 1. Thylakoids, membranous sacs, stacked to form a granum 2. Stroma, the internal fluid iv. The chloroplast is one of a group of plant organelles, called plastids d. Peroxisomes: Oxidation i. Peroxisomes are specialized metabolic compartments bounded by a single membrane ii. Peroxisomes produce hydrogen peroxide and convert it to water iii. Peroxisomes perform reactions with many different functions iv. How peroxisomes are related to other organelles is still unknown e. The cytoskeleton is a network of fibers that organizes structures and activities in the cell i. The cytoskeleton is a network of fibers extending throughout the cytoplasm ii. It organizes the cell’s structures and activities, anchoring many organelles iii. It is composed of three types of molecular structures iv. Microtubules v. Microfilaments vi. Intermediate filaments f. Roles of the Cytoskeleton: Support and Motility i. The cytoskeleton helps to support the cell and maintain its shape ii. It interacts with motor proteins to produce motility iii. Inside the cell, vesicles can travel along “monorails” provided by the cytoskeleton iv. Recent evidence suggests that the cytoskeleton may help regulate biochemical activities g. Components of the Cytoskeleton i. Three main types of fibers make up the cytoskeleton 1. Microtubules are the thickest of the three components of the cytoskeleton 2. Microfilaments, also called actin filaments, are the thinnest components 3. Intermediate filaments are fibers with diameters in a middle range ii. Cilia and flagella share a common structure 1. A core of microtubules sheathed by the plasma membrane 2. A basal body that anchors the cilium or flagellum 3. A motor protein called dynein, which drives the bending movements of a cilium or flagellum h. Extracellular components and connections between cells help coordinate cellular activities i. Most cells synthesize and secrete materials that are external to the plasma membrane ii. These extracellular structures include 1. Cell walls of plants 2. The extracellular matrix (ECM) of animal cells 3. Intercellular junctions i. Cell Walls of Plants i. The cell wall is an extracellular structure that distinguishes plant cells from animal cells ii. Prokaryotes, fungi, and some protists also have cell walls iii. The cell wall protects the plant cell, maintains its shape, and prevents excessive uptake of water iv. Plant cell walls are made of cellulose fibers embedded in other polysaccharides and protein v. Plant cell walls may have multiple layers 1. Primary cell wall: relatively thin and flexible 2. Middle lamella: thin layer between primary walls of adjacent cells 3. Secondary cell wall (in some cells): added between the plasma membrane and the primary cell wall vi. Plasmodesmata are channels between adjacent plant cells j. The Extracellular Matrix (ECM) of Animal Cells i. Animal cells lack cell walls but are covered by an elaborate extracellular matrix (ECM) ii. The ECM is made up of glycoproteins such as collagen, proteoglycans, and fibronectin iii. ECM proteins bind to receptor proteins in the plasma membrane called integrins k. Cell Junctions i. Neighboring cells in tissues, organs, or organ systems often adhere, interact, and communicate through direct physical contact ii. Intercellular junctions facilitate this contact iii. There are several types of intercellular junctions 1. Plasmodesmata 2. Tight junctions 3. Desmosomes 4. Gap junctions l. Plasmodesmata in Plant Cells i. Plasmodesmata are channels that perforate plant cell walls ii. Through plasmodesmata, water and small solutes (and sometimes proteins and RNA) can pass from cell to cell m. Tight Junctions, Desmosomes, and Gap Junctions in Animal Cells i. At tight junctions, membranes of neighboring cells are pressed together, preventing leakage of extracellular fluid ii. Desmosomes (anchoring junctions) fasten cells together into strong sheets iii. Gap junctions (communicating junctions) provide cytoplasmic channels between adjacent cells iv.
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