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Date Created: 11/03/15
Bio Exam 2 Notes Cell Structure All cells have: - Cytoplasm – semifluid in cell (water, salt, other molecules, etc.) - Chromosome – contains genetic material - Plasma membrane – define separate cells, regulates what goes in and out of cell, phospholipid bilayer - Ribosomes – critical for making proteins Phospholipid bilayer – hydrophobic tails facing each other, hydrophilic heads on outer sides Ribosomes – proteins made, two subunits (one large, one small), attached to endoplasmic reticulum (ER – only in eukaryotic cells), OR may be free in the cytoplasm Prokaryotic cells: - No membrane-bound organelles - Does have chromosomes, therefore has DNA - Often are bacteria and archaea – CAN be beneficial - Mostly unicellular - Cell wall – protective coating, keeps sturdy shape - Nucleoid – often confused for a nucleus, location of bacterial chromosomes - Capsule – a gel-like coating outside of the cell wall Eukaryotic cells: plants and animals - Have a nucleus - Have membrane-bound organelles - Nuclear membrane/envelope o Has DNA o Consists of two bilayers (two of picture example) - Chromatin – loose in the cell o DNA and associated proteins o Coils into chromosomes – tightly condensed - Nucleoplasm – liquid - Nucleolus – darker stain o Has RNA o Puts together ribosomes - Pores – for enzymes to get in, and get other “stuff” out - Endoplasmic Reticulum (ER) – two types o Rough ER (rER) – ribosomes on surface to give a rough look, glycoprotein modification happens in rER Glycoprotein = protein with sugars, their shapes change in order to carry out their function o Smooth ER (sER) – NO ribosomes, lipid synthesis, holds calcium ions, metabolizes carbs (makes them), detoxes drugs and poisons in the body, molecules are also made here and get carried to the Golgi Body - Golgi – the post office of the cell o Stack of membrane o cis side faced toward the ER o trans side faces the plasma membrane o Stores, holds, and distributes, proteins and lipids Vesicles help to send them out to plasma membrane o Receives molecules (pods) from ER, then they pass through the Golgi, and are sent out to the cell - Mitochondria – the power house of the cell o Converts chemical energy (carbs) to ATP o Double-membrane (the inner fold are called cristae) o Matrix – the inner liquid of mitochondria o Has enzymes for cellular respiration on the folds of mitochondria o Can divide (or bud) independently o Contains circular DNA of its own and also has its own ribosomes (in common with bacteria) - Cellular Respiration – carbs convert to ATP o Carbs (glucose) + oxygen = carbon dioxide + water + energy (ATP) o ATP – used for energy-requiring process in cells - Lysosomes – recycler of the cell o Small, spherical, only in animal cells o Contain hydrolytic enzymes to break down macromolecules o Uses broken down molecules for something else, or breaks down and clean molecules for something else (a new function) - Peroxisomes – helps break down hydrogen peroxide, makes it into water - Vacuoles (plants) – central and large, used to support the cell o Takes up a large volume of the cell o Consists of water, solutes, etc. - Cell wall – protective layer or second barrier, has cellulose - Chloroplast – site of photosynthesis o Producers – use solar energy and makes it into carbs o Double membrane organelle o Stroma – liquid inside o Thylakoid – connected inside, a stack of grana (resembles a stack of candy Sprees) o Have their own DNA and ribosomes, can divide independently (like the mitochondria) o Chlorophyll – inside the thylakoid - Cytoskeleton o Maintains cell shape o Helps move cell and organelles o Assembled and broken down critically o Types (small and large) Actin filaments – actin subunits Intermediate filaments – fibrous subunits Microtubules – straw appearance, make up spindle in dividing cells, tubulin subunits - Microtubules – grow out from centrosome o Centrosome – two centrioles, tube structure with nine triplets in a ring o New microtubules sprout from centrioles (at a right angle) - Cilia – contain microtubules, has doublets around center pair - Flagella – contain microtubules, one flagellum per cell o Cilia and flagella move nutrients together o Microtubules in flagella and cilia interact with dynein to cause movement Photosynthesis – conversion of energy (solar energy into carbs (sugars) - Plants, algae, cyanobacteria - Solar energy + carbon dioxide + water = carbohydrate + oxygen (this is the OPPOSITE of ATP, equation is flipped) Endosymbiotic Theory - Eukaryotic cells evolved from interactions and engulfing of bacteria that produce ATP and photosynthesize - Support of this theory – mitochondria and chloroplast have own DNA and ribosomes and divide independently Outside of the Cell: - Extracellular matrix (ECM): o Glycoproteins – collagen, proteoglycans, fibronectin o ECM proteins bind to receptor proteins in plasma membrane called integrins Interactions causes movement or anchoring of cells (wrinkles) - Cell junction – neighboring cells interact, different types o Plasmodesmata – between plants cells, allow water and small solutes to pass o Tight – animal cells, prevents movement of molecules across sheet of epithelial cell o Desmosomes – animal cells, anchor for fibers in cytoskeleton o Gap – animal cells, small channels for water and solutes - Plasma membrane o Fluid mosaic – molecules not static o Marks boundaries inside and outside of cell o Regulates passage in and out of cell o Main molecule is the phospholipids Polar heads – hydrophobic, face into watery area Nonpolar tails – hydrophobic, face each other, fatty acid part makes hydrophobic core (barrier) o Embedded proteins, glycoproteins, cholesterol - Fluidity of membranes o Lipids and proteins move side to side o Solid at low temperature o More unsaturated hydrocarbon tails (double bonds) of phospholipids = more space for fluidity More unsaturated tails – crooked appearance o Saturated tails – have a straighter appearance, more organized o Cholesterol Warm temperature = more solid Cooler temperature = more fluidity by preventing tight packing - Evolution of Lipid Differences o Species in environmental conditions have variations in lipid composition of cell membranes o Some can change liquid composition in response to temperature change - Membrane Proteins and Functions: o Peripheral proteins – only associated with one side of membrane o Integral proteins – within the membrane o Transmembrane proteins – peek out on both sides of membrane o Functions of proteins in the membrane Transport Enzyme activity – speed of reactions Attachment to cytoskeleton and ECM, anchor Recognition (glycoproteins) – communication, on the surface of red blood cells Intercellular joining-junction Signal transduction – reactions such as adrenaline o Membranes are selectively permeable Water uses aquaporins to cross Small uncharged molecules pass easily – hydrophobic, gases Charged molecules do not pass easily because of hydrophobic core Large molecules (like sugar), fold into 3-D shape, do not cross freely, need extra help