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ch6-7 (6.6 (Microtubules (Tubulin Polymers) (stpm-form-6-biology…
ch6-7
6.6
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The cytoskeleton
It organizes the cell’s structures and activities, anchoring many organelles
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Support and Motility
Inside the cell, vesicles can travel along tracks provided by the cytoskeleton
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6.2
Eukaryotic cells
For exampal Protists, fungi, animals, and plants all consist of eukaryotic cells
The basic structural and functional unit of every organism is one of two types of cells: prokaryotic or eukaryotic
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plasma membrane
is a selective barrier that allows sufficient passage of oxygen, nutrients,
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5.6
The Evolutionary Origins
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The engulfed cell formed a relationship with the host cell, becoming an endosymbiont
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7.3
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Passive transport
Although each molecule moves randomly, diffusion of a population of molecules may be directional
At dynamic equilibrium, as many molecules cross the membrane in one direction as in the other
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Passive Transport
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In facilitated diffusion, transport proteins speed the passive movement of molecules
Some ion channels, called gated channels
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6.8
A cell is greater
For example, a macrophage’s ability to destroy bacteria involves the whole cell
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Function
Chloroplast Photosynthesis (chloroplasts are in cells of photosynthetic eukaryotes,Including plants)
Peroxisome Contains enzymes that transfer H atoms from substrates to oxygen, producing H2O2 (hydrogen peroxide), which is converted to H2O.
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6-4
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Biosynthetic Factory
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Smooth ER, which lacks ribosomes
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The endoplasmic reticulum (ER) accounts for more than half of the total membrane in many eukaryotic cells
Rough ER, whose surface is studded with ribosomes
Distributes transport vesicles, secretory proteins surrounded by membranes
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Has bound ribosomes, which secrete glycoproteins (proteins covalently bonded to carbohydrates)
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7.5
Human cells
Individuals with the disease familial hypercholesterolemia have missing or defective LDL receptor proteins
Human cells use receptor-mediated endocytosis to take in cholesterol, which is carried in particles called low-density lipoproteins (LDLs)
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Bulk transport
Large molecules, such as polysaccharides and proteins, cross the membrane in bulk via vesicles
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Small molecules and water enter or leave the cell through the lipid bilayer or via transport proteins
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Animation
exocytosis
In exocytosis, transport vesicles migrate to the membrane, fuse with it, and release their contents outside the cell
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Endocytosis
Endocytosis is a reversal of exocytosis, involving different proteins
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In endocytosis, the cell takes in macromolecules by forming vesicles from the plasma membrane
5.4
Active transport
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Some transport proteins, however, can move solutes against their concentration gradients
requires energy, usually in the form of ATP hydrolysis, to move substances against their concentration gradients
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For example, an animal cell has a much higher potassium (K+) and a much lower sodium (Na+) concentration compared to its surroundings
Active transport allows cells to maintain concentration gradients that differ from their surroundings
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Membrane potential
Voltage is created by differences in the distribution of positive and negative ions across a membrane
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Cotransport
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Cotransport occurs when active transport of a solute indirectly drives transport of other substances
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6.7
Cell Walls of Plants
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Prokaryotes, fungi, and some unicellular eukaryotes also have cell walls
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(ECM) of Animal Cells
The ECM is made up of glycoproteins such as collagen, proteoglycans, and fibronectin
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7.2
Transport Proteins
Some transport proteins, called channel proteins,
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Other transport proteins, called carrier proteins
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6.1
Microscopy
In a light microscope (LM), visible light is passed through a specimen
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