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26 Cards in this Set
- Front
- Back
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Mitochondria
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Organelle That contains DNA
• Mitochondria are cellular powerhouses • Contain circular DNA • Sites for chemical reactions called oxidative metabolism • The organelle is surrounded by two membranes |
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Chloroplasts
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Organelle that contains DNA
• Chloroplasts are the location for photosynthesis • The organelle is also surrounded by two membranes • Inside a series of membrane are fused to form Thylakoids, site of photosynthesis • Contain circular DNA• Chloroplasts are the location for photosynthesis • The organelle is also surrounded by two membranes • Inside a series of membrane are fused to form Thylakoids, site of photosynthesis • Contain circular DNA |
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Organelles That Contain DNA
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• Both mitochondria and chloroplasts
possess circular DNA that is not found elsewhere in the cell • They cannot be grown free of the cell - they are totally dependent on the cells within which they occur |
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The theory of endosymbiosis is...
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- states that some organelles evolved from a symbiosis
in which one cell of a prokaryotic species was engulfed by and lived inside of a cell of another species of prokaryote - the engulfed species provided their hosts with advantages because of special metabolic activities - the modern organelles of mitochondria and chloroplasts are believed to be found in the eukaryotic descendants of these endosymbiotic prokaryotes |
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Evidence Supporting Endosymbiosis theory:
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• In addition to the double membranes and
circular DNA found in mitochondria and chloroplasts, there is a lot of other evidence supporting endosymbiotic theory - mitochondria are about the same size as modern bacteria - the cristae in mitochondria resemble folded membranes in modern bacteria - mitochondrial ribosomes are similar to modern, bacterial ribosomes in size and structure - mitochondria divide by fission, just like modern bacteria |
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The Cytoskeleton: Inferior framework of the cell.
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• The cytoskeleton is an internal framework of
protein fibers that - anchor organelles to fixed locations - support the shape of the cell - helps organize ribosomes and enzymes needed for synthesis activities • The cytoskeleton is dynamic and its components are continually being rearranged (formed and disassembled) |
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Three different types of protein fibers comprise
the cytoskeleton |
-intermediate filaments
• thick ropes of intertwined protein • Mechanical strength -microtubules • hollow tubes made up of the protein tubulin • Intracellular transport, stabilization cell structure - microfilaments • long, slender microfilaments made up of the protein actin • Cell movement |
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Microtubules
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Microtubules provide a means to transport
material inside the cell efficiently over long distances |
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Centrioles
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Centrioles are complex structures that assemble
microtubules in animal cells and the cells of most protists - they anchor locomotory structures, such as flagella or cilia - they assemble microtubules near the nuclear envelope - Involved in cell division |
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Cell Movement
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Cell movement is associated with the
movement of actin microfilaments and/or microtubules - some cells “crawl” by coordinating the rearrangement of actin microfilaments - some cells swim by coordinating the beating of microtubules grouped together to form flagella or cilia |
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Outside the Plasma Membrane: Cell Movement
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• found in plants, fungi,
and many protists • comprised of different components than prokaryotic cell walls • function in providing protection, maintaining cell shape, and preventing excessive water loss/uptake |
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Extracellular Matrix
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Extracellular matrix (ECM)
• takes the place of the cell wall in animal cells and is comprised by a mixture of proteins secreted by the cell • collagen and elas(n proteins form a protec4ve layer over the cell surface • fibronectin protein connects the ECM to the plasma membrane • the fibronectin molecules also connect to integrins, proteins that extend into the cytoplasm of the cell – this extracellular‐intracellular connec4on allows the ECM to influence cellular behavior and to coordinate groups of cells functioning as tissues |
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Diffusion and Osmosis Definition
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Movement of water and nutrients into a
cell or elimination of wastes out of cell is is essential for survival |
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Diffusion and osmosis: Movement occurs in 3 ways:
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This movement occurs across a biological
membrane in one of three ways • diffusion • membrane folding • protein transport |
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Diffusion: Difuse: duh!
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• Molecules move in a random fashion but there is
a tendency to produce uniform mixtures • The net movement of molecules from an area of higher concentration to an area of lower concentration is termed diffusion • Molecules diffuse down a concentration gradient from higher to lower concentrations -diffusion ends when equilibrium is reached |
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Only certain substances undergo diffusion
across the plasma membrane |
• Only certain substances undergo diffusion
across the plasma membrane - molecules like oxygen, carbon dioxide, and nonpolar lipids - ions and polar molecules cannot cross the interior of the membrane • Water, although polar, is able to diffuse freely across the plasma membrane - aquaporins are selective channels that permit water to cross |
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Osmosis
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• Water moves down its concentration
gradient in moving into or out of a cell through a process called osmosis - the movement of water is dependent on the concentration of other substances in a solution - the greater the amount of solutes that are dissolved in a solution, then the lesser the amount of water molecules that are free to move |
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Osmotic Concentration
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• The concentration of all molecules dissolved
in a solution is called the osmotic concentration of the solution • Osmotic concentrations of different solu4ons can be compared relative to each other |
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Bulk Passage into and out of Cells
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• Bulky substances are contained within
vesicles as they are moved into and out of a cell - endocytosis is the engulfing of substances outside of the cell in order to form a vesicle that is brought inside the cell - exocytosis is the discharge of substances from vesicles at the inner surface of the cell |
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Forms of Endocytosis
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• Phagocytosis is
endocytosis of particulate (solid) matter • Pinocytosis is endocytosis of liquid matter |
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Selective Permeability
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Selective permeability allows cells to
control specifically what enters and leaves - involves using proteins in the membrane for transporting substances across - transport can be down a concentration gradient (i.e., diffusion) or against a concentration gradient (i.e., active transport) |
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Selective Permeability
- Selective diffusion |
proteins act as open channels for whatever is
small enough to fit inside the channel • this form of diffusion is common in ion transport |
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Selective Permeability
- Facilitated diffusion |
• proteins act as carriers that can bind only to
specific molecules to transport • transport is limited by the availability of carriers • if there are not enough carriers, then the transport is saturated |
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Selective Permeability
-Active Transport |
Selective Permeability
• Active transport - utilizes protein channels that open only when energy is supplied - energy is used to pump substances against or up their concentration gradients -allows cells to maintain high or low concentration of certain molecules • recall that diffusion always ends in equilibrium • There are two kinds of channels that perform active transport in cells - sodium-potassium pump - proton pump |
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How the sodium-potassium pump
works |
• The result of the Na+-K+ pump is to
generate a concentration gradient with more Na+ outside of the cell than inside • Cells exploit this gradient in key ways -for the conduction of signals along nerve cells - for the transportation of important molecules into the cell against their concentration gradient |
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Selective Permeability
-Coupled Transport |
• the cell membrane has many facilitated diffusion
channels for Na+ but it is only transported if partnered with another substance -this is called coupled transport • The concentration gradient favoring the entry of Na+ into the cell is so strong that a coupled substance will be transported even if it is against the concentration gradient -coupled transport is a common way for cells to accumulate sugars and amino acids |
