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Cell Biology. Ch. 4. 1. Cell Theory. Every organism is made of on or more cells. Cell is the smallest unit of life. Continuity of life depends on the growth and division of single cells. 2. Basic Components of a Cell:. Plasma membrane Nucleus or nucleoid Cytoplasm. 3. Cell Membrane.
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Cell Biology Ch. 4 1
Cell Theory • Every organism is made of on or more cells. • Cell is the smallest unit of life. • Continuity of life depends on the growth and division of single cells. 2
Basic Components of a Cell: • Plasma membrane • Nucleus or nucleoid • Cytoplasm 3
Cell Membrane • Lipid bilayer – two sheets of lipid molecules. Hydrophilic Head Hydrophobic Tail 4
Cell Size • If a cell keeps growing the volume will increase more rapidly than its surface area will. • Problem: a cell needs surface area to take in material and excrete material. surface-to-volume ratio • If volume is too large then materials cannot be transported easily across the cell. 5
Nucleus • Directs cell activities. • Separated from cytoplasm by nuclear membrane. • Contains genetic material – DNA • DNA stores information to make proteins, enzymes that are needed for cellular functions. 6
Nucleus • Nuclear envelope- double-membrane system, 2 lipid bilayers. • Proteins are embedded in the innermost layer. • These are used to anchor the molecules of DNA to the envelope and help keep them organized. • On the surface of the nuclear envelope are ribosomes where proteins are built. 7
Nucleolus • Inside nucleus • Protein and RNA molecules are being constructed here. • Needed to synthesis proteins. 8
Chromosomes • Tightly bundled DNA. 9
Cytomembrane System • System in cytoplasm that assembles, modifies, packages and ships proteins and lipids. • Some polypeptide chains enter the space inside rough ER, where they are shaped into proteins. • In smooth ER, lipids are assembled. • Vesicles bud from the ER membrane and then transport unfinished proteins and lipids to a golgi body. 10
Proteins and lipids take on their final form in the space inside the golgi body. There they are sorted out and shipped to their proper destinations. • Vesicles budding from the golgi membrane transport finished products to the plasma membrane. 11
Endoplasmic Reticulum ER • Rough – ribosomes attached. • Smooth – ribosome free, lipids are assembled here. • Polypeptide chains are synthesized on ribosomes. 12
Golgi Bodies • Enzymes in here put the finishing touches on proteins and lipids. • Sorts them. • Package them inside vesicles for shipment. 13
Vesicles • Tiny sacs that move through the cytoplasm. • Common type: Lysosome- buds from golgi membranes. • Lysosomes contain digestive enzymes that breakdown proteins, carbs, nucleic acids, and some lipids. 14
Vesicles • Peroxisomes – another type of vesicle that break down fatty acids and amino acids. • Hydrogen peroxide is formed during these reactions. 15
Mitochondria • Where ATP is formed. • Organic compounds are broken down to carbon dioxide and water. • Has a double membrane system. • Crista – inner fold. 16
Membrane System of Mitochondria • Enzymes and other proteins stockpile hydrogen ions in the outer compartment of the cristae. • Electrons transfer through the folds which drive the stockpiling. • This electron transfer forms ATP. 17
Chloroplasts • Only in photosynthetic cells. • Convert sunlight energy into ATP which is used to make sugars and other organic compounds from CO2 and Water. CentralVacuole -stores amino acids, sugars, ions, and toxic wastes. • x 18
Cytoskeleton • Internal organization • Shape • Capacity to move Cytoskeletal Elements: -microtubules -microfilaments -intermediate filaments (give strength to cells) 19
Microtubules • Long, hollow cylinder, largest • Tubulin – protein • Polar – so that the microtubules can line up in the same direction. • Used in cell division to split chromosomes apart. 20
Microfilaments • Thinnest of cytoskeletal elements • Helix shape • Polar • Myosine and actin – protein that attaches to microtubules and microfilaments to cause cell movement. 21
Cell Cortex • 3d network of microfilaments and other proteins. • Just beneath the plasma membrane. • Reinforces the cell surface. • Facilitates movements.
Movement • Pseudopods • Microfilaments and microtubules • Cilia • flagella
4.11 Prokaryotic Cells • All bacteria cells are prokaryotic. • Simplest kind of cells. • Some have flagella. • pilli
Class Jump Assignment Homework pg.77 • Review Questions: 1 – 15 • Self-Quiz: 1 - 6
Sec. 5 – Membrane FluidMosaicModel: • Mixture of phospholipids, glycolipids, sterols, and proteins. • Glycolipids have more than one sugar than phospholipids on their heads. • Membrane is fluid, drift sideways, short or kinked hydrophobic tails contribute to the membrane fluidity because phospholipid bonds are weak.
Proteins in Membrane X • Transportprotein – span the bilayer and allow water-soluble substances to move through their interior. Bind to molecules on one side of the membrane then release them on the other side.
ReceptorProteins – bind extracellular substances, like hormones, that trigger changes in cell activities. RecognitionProteins – oligosaccharide chains identify other cells. Ex. WBC AdhesionProteins – help locate like cells and adhere to them.
Selective Permeability • Membrane permits some substances but not others to cross it in certain ways, at certain times. • Large polar molecules such as glucose almost never move freely across the bilayer, nor ions.
Concentration Gradients and Diffusion Concentration – number of molecules or ions of a substance in a specified region. Gradient – the number in one region is not the same as it is in another. Concentrationgradient – a difference in the number of molecules or ions of a given substance between adjoining regions.
Diffusion • Molecules moving from high concentration to lower concentration. Ex. Drop of dye in water or spraying perfume. Faster at higher temp. When concentration is equal – dynamic equilibrium http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_diffusion_works.html
Electric Gradient • Difference in electric charges of adjoining regions. Ex. Fluid around a membrane may have many dissolved ions. --- so the fluid having the more negative charge tends to exert the greatest pull on positively charged substances such as sodium ions.
Pressure Gradient • Difference in the pressure being exerted in adjoining regions. • High pressure to low pressure
Facilitateddiffusion – transport protein diffuses substances into cell, no energy required. http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_facilitated_diffusion_works.html ActiveTransport – solutes are pumped through interior by transport proteins, energy required.
Active Transport System-against concentration gradient • Calciumpump – helps keep the calcium concentration in a cell at least a thousand times lower than outside. • Sodium-potassiumpump – moves potassium ions across the plasma membrane. This protein also facilitates binding of a sodium ion on one side of a cell membrane and released on the other side. Its release facilitates the binding of K+ at a different binding site on the protein, which reverts to its original shape after K+ is delivered to the other side.
http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_the_sodium_potassium_pump_works.htmlhttp://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_the_sodium_potassium_pump_works.html
Osmosis • Bulkflow – mass movement of one or more substances in response to pressure, gravity, or some other external force. • Osmosis – diffusion of water molecules in response to a water concentration gradient between two regions separated by a selectively permeable membrane. • http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_osmosis_works.html
Isotonic – the amount of solute in a water solution is equal on both sides of membrane. • Hypotonic – one side has less solute than the other side of membrane.
Hypertonic – one side has more solute than the other side of the membrane.
Bulk Transport Across Membrane • Exocytosis – exocytic fuses with plasma membrane and release its contents outside the cell. • Endocytosis – substance is taken up by cell. • Receptor mediated: membrane receptors recognize specific substances and bind with them. Ex. Vitamins, lipoproteins, iron, hormones..
Bulk-phase: endocytic vesicle forms around a small volume of extracellular fluid regardless of what kinds of substances happen to be dissolved in it. • Phagocytosis: cell engulfs microorganisms, large particles, and cellular debris. “cell eating” http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__phagocytosis.html
Review • Prokaryotes • Pro = before; karyon = nucleus • lack membrane-bound organelles • earliest cell type • Eukaryotes • Eu = true; karyon = nucleus • contain membrane-bound organelles • Evolved from prokaryotes
Cytoskeleton Answer: • Scaffold of microfilaments, intermediate filaments, microtubules that maintain cell shape, support, anchor organelles, movement, intracellular transport…
Answer: Nucleus • Contains DNA
Rough ER Answer: • Contains ribosomes and is involved in protein synthesis.
Smooth ER Answer: • Lacks ribosomes and is involved in membrane lipid synthesis.
Golgi Apparatus Answer: • Flattened vesicles that receive protein from ER. • Refine protein and sort it and send it out in either vacuoles or lysosomes.
Lysosome Answer: • Contain enzymes for use in hydrolytic breakdown of macromolecules.
Ribosomes Answer: • Involved in protein synthesis. • Free or bound to ER.