Unit 2 Notes
Unit 2 Notes BSC 2010
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This 9 page Class Notes was uploaded by Stefanie Villiotis on Sunday March 27, 2016. The Class Notes belongs to BSC 2010 at Florida State University taught by Dennis in Fall 2015. Since its upload, it has received 12 views. For similar materials see General biology in Biological Sciences at Florida State University.
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Date Created: 03/27/16
BSC2010 Unit 2 Notes Cells- The fundamental unit of life - All organisms are made of cells - Simplest collection of matter that can live - Cell Structure is correlated to cell function How we study cells: I. Microscopy - Types of Microscopes: Light- most plant and animal cells, nucleus, bacteria, mitochondrion; visible light passing through a lens system to magnify images; can magnify ~1000x; various techniques enhance contrast; most subcellular structures are too small to be resolved. Electron- Smallest bacteria, viruses, ribosomes, proteins, lipids, small molecules, atoms. Two types: Scanning electron microscope- focuses beam of electron to surface of a specimen- 3-D image; specimen must be coated in film of gold. Transmission electron microscope- focus beam of electron through specimen- 2-D image, specimen stained with a heavy metal such as urinyl acetate. - Quality of images: Magnification- ratio of an objects image to its size. Resolution- measure of clarity; minimum distance of two distinguishable parts. Inversely related to wavelength. Contrast- visible differences in parts of a sample. II. Cell Fractionation - Taking apart cells and separating major organelles - [Ultra] centrifuges fractionate cells into component parts - Enables scientists to determine function of organelles Two Types of Cells: Prokaryotic & Eukaryotic I. Features common to ALL cells - Plasma Membrane- selective barrier allows sufficient passage of oxygen nutrients and waste; generally, a double layer of phospholipids. - Cytosol- semifluid interior of a cell - Chromosomes- carry the genetic material (DNA) II. Prokaryotic Cells - No nucleus, DNA is in an unbound region called nucleoid. - No membrane bound organelles - Cytoplasm bound by the plasma membrane III. Eukaryotic Cells - DNA is in a nucleus bound by a membrane envelope - Membrane bound organelles - Cytoplasm is the region between plasma membrane and nucleus Organelles - Two groups of 1) Endomembrane System and 2) Energy Conversion Endomembrane System (membranes are directly and indirectly connected by transport vesicles) - Nucleus- Information central - Endoplasmic Reticulum (ER)- Factory - Golgi Apparatus- Shipping & Receiving - Lysosomes- Digestive compartments—disassembling compartments - Vacuoles- Maintenance and Storage compartments Energy Conversion - Mitochondria- energy production (has own DNA, double phospholipid bilayer) - Chloroplasts- make sugars small carbohydrates (has own DNA, double phospholipid bilayer) - Peroxisome- breakdown compartment Extracellular Components - Cell walls of plants (and other organisms) -Distinguish plants, fungi, prokaryotes, and some protists from animal cells -Protect the cell from excessive uptake of water -Made of cellulose - multiple layers: Primary Cell Wall (thin/flexible) Middle Lamella (thin layer between primary) Secondary Cell Wall (some cells) (between plasma Membrane & primary cell wall) - Extracellular Matric of Animal Cells -Animal cells lack cell walls but are covered by an elaborate extracellular matrix (ECM) -made up of glycoproteins (collagen, proteoglycans, and fibronectin) -ECM proteins bind to receptor proteins in plasma membrane called INTEGRINS. -Functions of ECM: support, adhesion, movement, regulation - Intercellular Junctions -Neighboring cells adhere intact and communicate through direct physical contact. -Intercellular junctions facilitate this contact -Types of Intercellular Junctions: -Plasmodesmata- channels that perforate cell walls through plasmodesmata water and small solutes can pass from cell to 2 cell. -Tight Junctions- membranes of neighboring cells pressed together to prevent leakage of extracellular fluid. -Desmosomes- anchoring junctions fasten together cells in strong storing sheets -Gap Junctions- provide cytoplasmic channels between adjacent cells. Plasma Membrane - Boundary that separates the cell from its surroundings - Exhibits SELECTIVE PERMEABILITY - Phospholipids: -The most abundant lipid in plasma membrane -Are AMPHIPATHIC molecules- contain hydrophobic/hydrophilic regions -Can move within the bilayer- generally laterally// rarely flip across - As temperature decreases membranes can solidify- degree of solidification depends upon the type of lipid. - Membranes rich in unsaturated fatty acids are more fluid than those rich in saturated fatty acids. - Cholesterol: At warm temps. Cholesterol restrains movement of membrane; At cool temps, Cholesterol maintains fluidity of membrane. Proteins in the Cell Membrane - Determine most of the membrane’s specific functions -Peripheral Proteins= bound to the surface -Integral Proteins= pass through hydrophobic core; also called Transmembrane proteins -Hydrophobic regions consist of one or more strands of non-polar amino acids. - Functions or membrane proteins: -Transport Enzymatic Activity, Signal Transduction, Cell to Cell Recognition, Intercellular Joining, Attachment to ECM - Synthesis & Sidedness of Membranes -Membranes have a distinct inside and outside face -The asymmetrical distribution of proteins, lipids, and associated carbohydrates is determined when the membrane is built by the endoplasmic reticulum and golgi apparatus. - Membrane structure results in SELECTIVE PERMEABILITY - Hydrophobic/ non-polar/ hydrocarbons pass readily through cell membrane 3 - Polar molecules do not cross easily & need help (Transport Proteins) - Transport Proteins= Aquaporins provide hydrophilic channels through which polar molecules can pass - Passive Transport - Requires no energy - Diffusion- tendency for molecules to spread out evenly in space - At equilibrium you have an EQUAL number of molecules crossing each way - Substances diffuse down their concentration gradient **(move from high concentration to low concentration) - Osmosis- diffusion of H O 2cross a selectively permeable membrane - Water diffuses across a membrane from the region of lower solute concentration to the region of higher solute concentration. - Tonicity- the ability of solution to cause a cell to gain or lose water. - Isotonic- solute concentrations are the same inside & outside of the cell. (normal) - NO net movement of H O acr2ss membrane - Hypertonic- solute concentration > than inside cell= the cell loses water (shriveled) - Hypotonic- solute concentration < than inside cell = cell gains water (LYSIS- bursting cell) - Facilitated Diffusion - Transport proteins speed the passive movement of molecules across the plasma membrane. - Channel Proteins- provide corridors that allow specific molecules or ions to cross the cell membrane. - Include: Aquaporins (facilitated diffusion of H O) 2 Ion Channels (open or close in response to stimulus) Carrier Proteins (undergo change in structure to translocate solute) - Active Transport - Uses energy to move solutes against a concentration gradient - REQUIRES ENERGY- ATP - Allows cells to maintain concentration gradients that differ from their surroundings. - ION PUMPS - COTRANSPORT- when active transport of a solute indirectly drives transport to another solute - Bulk Transport - Across the plasma membrane by EXOCYTOSIS and ENDOCYTOSIS - Requires Energy - Exocytosis= transport vesicles migrate to membrane, fuse with it, then release contents. 4 Metabolism - Transforms matter/energy - Subject to laws of thermodynamics - Pathways- begin with a specific molecule and end with a specific product - Each step is catalyzed by an enzyme Catabolic - release energy by breaking down complex molecules into simpler molecules - Cellular respiration, breaks down glucose in the presence of oxygen. Anabolic - Conserve energy to build complex molecules from simpler ones - E.g. the synthesis of a protein from amino acids Bioenergetics = the study of how organisms manage energy resources Energy = the capacity to cause change - Kinetic Energy- energy associated with motion; HEAT= thermal energy is kinetic energy associated with the motion of atoms or molecules - Potential Energy- energy possessed because of location/structure; Chemical Energy= potential energy available for release in a chemical reaction **ENERGY can be converted from ONE form to ANOTHER** Laws of Energy Transformation = Laws of Thermodynamics - Thermodynamics- study of energy transformation - Studied in closed or open systems - Closed system= isolated from surroundings - Open system= energy and matter can be transferred to/from surroundings - ORGANISMS ARE OPEN SYSTEMS 5 Laws of Thermodynamics 1. Principle of conservation of energy - The amount of energy in the universe is CONSTANT - Energy can be transferred and transformed but never created or destroyed. 2. During every energy transformation some of the energy is unstable and given off as heat; Energy transfer or transformation increases the entropy of the universe = Disorder Energy Changes in Reactions - Some reactions occur spontaneously - Without energy input - They can happen quickly or slowly - If no energy input they must increase the entropy(disorder) of the universe - Biologists want to know what reactions occur spontaneously and what reactions require the input of energy - We measure free energy change in Gibbs Free Energy G 2 (generally the x-axis of a reaction energy diagram) - The change in free energy( G) is related to the change in total energy (H) and temperature G= H TS - -G = Exergonic, spontaneous, gives off energy - + G = Endergonic, non-spontaneous, requires energy Free Energy, Stability, and Equilibrium - Free energy (G) measure of a system’s instability or tendency to change to a more stable state - More free energy = G = less stable = greater work capacity - Less free energy = G = more stable = less work capacity - During spontaneous change, the free energy decreases (- G) and stability increases; energy given off can do work - During a non-spontaneous change, free energy increases (+ G), stability decreases, work/energy is required How ATP performs work - Cellular work powered by the hydrolysis of ATP - Energy from exergonic reactions of ATP hydrolysis can be used to drive an endergonic reaction 6 - The use of an exergonic reaction to drive an endergonic reaction is ENERGY COUPLING The Activation Energy Barrier - The initial energy needed to start a chemical reaction FREE ENERGY OF ACTIVATION, ACTIVATION ENERGY, E A - Enzymes lower the E baArier - Enzyme activity, of course is affected by temp. at pH - Enzyme activity is also affected by “helper” chemicals - Cofactors= non protein enzyme helpers - May be organic or inorganic (co- enzyme) Regulation of Enzyme Activity - Occurs by: 1. Turning of and off enzyme-encoding genes 2. Regulating the activity of the enzyme - Enzyme Inhibitors - Allosteric Regulation- occurs when a regulatory molecule binds a protein at one site and affects function at another site - Can be ACTIVATORS or INHIBITORS –or substrates binding in a cooperative manner - Feedback Inhibition- end product shuts down pathway - Prevents cells from wasting resources 1. Catabolic pathways yield energy by oxidizing organic fuels 2. Redox reactions release energy when electrons closer to electronegative atoms 3. Organic fuel molecules are oxidized during cellular respiration Respiration- progressive oxidation of a macromolecule (glucose) to harvest potential energy (in form of electrons) to regenerate ADP ATP ATP 7 - Only 4 of the 38 ATP produced by respiration are made by substrate level phosphorylation. - The remaining 34 are made by oxidative phosphorylation - Oxidative phosphorylation may be broken down into two parts 1. Electron transport Chain Chemiosmosis - Electron transport Chain- collection of molecules buried in the cristae- inner membrane of mitochondrion - Mostly protein complexes numbered I-IV, plus ubiqui(idk) and Cyto(idk) C **check notes for actual words, prof has shitty handwriting** - The complexes are increasingly electronegative - The final e- acceptor is oxygen - Each oxygen also picks up a pair of H+ to form H O 2 Chemiosmosis - As electrons are passed down ETC protons are pumped inside of the inner membrane - This leads to a chemiosmotic gradient - The only way H+ and diffuse out through ATP synthase - Protons more 1 by 1 into the “rotor” of ATP synthase causing it to spin - This spinning provides the energy for phosphorylation of ADP ATP HOW MANY MOLECULES OF NADH WOUD BE PRODUCED BY 3 TURNS OF THE CAC? 9 3 TURNS OF THE CAC PRODUCES ENOUGH NADH TO MAKE _______ ATP BY OXIDATIVE PHOSPHORYLATION = 9 NADH x 3ATP = 27 All life fills into one of two groups - Autotrophs- sustain - Produces at biosphere - Produce organic molecules Photosynthesis converts light energy to chemical food On the test***= photosystem!! 8 9
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