Biology 2170 Week 5 Notes
Biology 2170 Week 5 Notes BIOL 2170 - 002
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BIOL 2170 - 002
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This 6 page Class Notes was uploaded by Katie Veselka on Wednesday September 21, 2016. The Class Notes belongs to BIOL 2170 - 002 at University of Toledo taught by Robert M. Stevens in Summer 2016. Since its upload, it has received 13 views. For similar materials see Fundamentals of Life Science: Biomolecules, Cells, and Inheritance in Biology at University of Toledo.
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Date Created: 09/21/16
Lecture 7: Cells 09/17/16 A) Cell theory a) All known living things are made up of one or more cells b) All living cells arise from pre-existing cells by division c) The cell is the fundamental unit of structure and function in all living organisms d) Implications: I) Functions of all cells are similar II)Life is continuous IIIOrigin of life was the origin of cells B) Properties of cells a) Cells are small (mostly) I) Exceptions: eukaryotic cells, plant cells, human eggs II) Cells are small because they need a high ratio of surface area to volume (1) Volume determines the amount of chemical activity in a cell per unit time (2) Surface area determines the amount of substances that can pass the cell boundary per unit time C) Microscopes a) Two basic types I) Light microscope (1) Uses glass lenses and light (2) Resolution=200 nanometers II)Electron microscope (1) Electromagnets focus an electron beam (2) Resolution= 50 picometers D) Plasma Membrane a) All cells are surrounded by a membrane I) The plasma membrane is made of a phospholipid bilayer b) Functions: I) Allows cells to maintain constant internal environment II)Is a selectively permeable barrier IIIImportant for communication and receiving E) Types of cells a) Two types of cells I) Prokaryotic II)Eukaryotic F) Prokaryotic cells a) Bacteria and archaea b) The first cells were probably prokaryotic c) Very small and very successful d) They can live on a diversity of energy sources and inhabit every environment, including extreme environments e) Characteristics I) Enclose in plasma membrane II)Cytoplasm consists of cytosol (water and dissolved material) IIIThe DNA is contained in the nucleoid IV)Ribosomes are the site of protein synthesis V) Have a rigid cell wall outside the plasma membrane VI)Some bacteria have a slimy capsule of polysaccharides VII) Some prokaryotes swim by the means of flagella VIII) Some bacteria have pili (1) Hair like structures projecting from the surface. (2) They help bacteria adhere to other cells f) Photosynthesis I) The photosynthetic bacteria, the plasma membrane folds into the cytoplasm to form an internal membrane system where photosynthesis occurs G) Eukaryotic cells a) All other living cells b) DNA is in a membrane enclosed compartment called the nucleus c) Characteristic I) Up to 10 times larger than prokaryotes II)Have membrane enclose compartments called organelles (1) Organelles have been studied using different techniques: microscopy and cell fractionation IIIHave protein scaffolding called the cytoskeleton d) The nucleus is usually the largest organelle I) Contains DNA II)Site of DNA replication IIISite of genetic control of cell activities IV) The nucleolus begins assembly of ribosomes V) Surrounded by two membranes (1) The nuclear envelope (i) Nuclear pores in the envelope control passage of molecules. (ii) Large molecules such as proteins need a signal to pass through VI)DNA in the nucleus (1) DNA combines with proteins to form chromatin in the nucleus (2) Chromosomes are separate strands of chromatin, which condense before cell division H) Ribosome a) In both eukaryotic cells and prokaryotic cells b) In eukaryotes ribosomes are either free in the cytoplasm, attached to the ER (RER), or inside mitochondria and chloroplasts I) Endomembrane system a) Includes the nuclear envelope, endoplasmic reticulum, Golgi apparatus, and PM b) The outer membrane of the nuclear envelope is continuous with the endomembrane system. c) Endoplasmic reticulum (ER) is a network of interconnected membranes including the RER and SER d) Rough endoplasmic reticulum (RER) I) Ribosomes are attached II) Segregates newly made proteins which enter the lumen and can be modified and transported e) Golgi apparatus I) Receives proteins from the ER and can further modify them II) Packages and sorts proteins f) Lysosomes originate from the Golgi apparatus I) They contain digestive enzymes to hydrolyze macromolecules into monomers II) Food molecules enter the cell through phagocytosis (1) A phagosome is formed, which fuses with the lysosome III)Lysosomes also digest cell materials (1) Autophagy J) Protein sorting a) Some amino acids sequences contain a signal sequence—an address label that tells the polypeptide where it belongs b) It gives directions I) 1. After translation go to an organelle (no signal then stay in cytosol) OR 2. Stop translation, go to the ER, finish synthesis at the ER surface c) If the protein is sent to the ER I) Signal sequence binds to a signal recognition particle before translation is done II) Ribosome attaches to a receptor on the ER; the growing polypeptide remains in membrane or passes through a channel III)An enzyme removes the N-terminal signal sequence K) Mitochondria a) In the mitochondria, energy in fuel molecules is transformed to the bonds of energy rich ATP: cellular respiration b) The inner membrane of the mitochondrion folds inward—a large surface are for proteins that participate in cellular respiration reactions c) The mitochondrion matrix contains DNA and ribosomes L) Chloroplasts a) Site of photosynthesis—light energy is converts to the energy of chemical bonds I) Have double membrane II) Contain ribosomes and DNA III)Thylakoids—flat, circular compartments of an inner membrane Lecture 8: Energy and Enzymes 09/21/16 A) Origin of eukaryotic cells a) Eukaryotic cells appeared about 1.5 billion years ago b) Endosymbiosis theory explains how eukaryotes could evolve from prokaryotes I) cells engulfed other cells that became mitochondria and chloroplasts. B) Energy a) The capacity to do work, or the capacity for change b) The transformation of energy is hallmark of life c) In cells, energy transformations are linked to chemical transformations and molecular movement. d) Types I) Potential energy (1) Is stored energy-as chemical bonds, concentration gradient, change imbalance, for example. II)Kinetic energy is the energy of movement C) ATP (adenosine triphosphate) a) Captures and transfer energy b) ATP releases a large amount of energy when hydrolyzed c) ATP can donate phosphate groups to other molecules d) Metabolism: the entire set of life-sustaining chemical reactions occurring in the cells of organisms D) Laws of Thermodynamics a) First Law I) When energy is converted from one form to another, the total energy before and after the conversion is the same b) Second Law I) When energy is converted from one form to another, some of the energy becomes unavailable to do work II)No energy transformation is 100 percent efficient E) Entropy a) Entropy is a measure of the disorder of a system b) It takes energy to impose order on a system. Unless energy is applied to a system, it will be randomly arranged or disordered. c) Living organisms must have a constant supply of energy to maintain order d) If a chemical reaction increases entropy, the products will be more disordered I) Example: hydrolysis of a protein into its component amino acids—ΔS is positive II)The products have less energy than the reactants and disorder increased: free energy is released F) Free Energy a) In any system I) Total energy= usable energy + unusable energy II)Enthalpy(H)= free energy (G)+ Entropy (S) IIIH=G+TS (T= absolute temperature) IV) G=H-TS b) Change in free energy (ΔG) in a reaction is the difference in free energy of the products and the reactions I) Change in energy can be measured in calories or joules II) ΔG=ΔH-TS (1) If ΔG is negative, free energy is spontaneous reaction (exergonic) (i) Exergonic reactions: cell respiration, catabolism (2) If ΔG is positive, free energy is not spontaneous (endergonic) (i) Endergonic reactions: active transport, cell movements, anabolism (3) If free energy is not available, the reaction will not occur III)Magnitude of ΔG depends on: (1) ΔH—total energy added (ΔH>0) or released (ΔH<0) (2) ΔS—change in entropy. Increases in entropy make ΔG more negative. G) Enzymes and Catalysts a) Catalysts increase the rate of reaction b) The catalyst is not altered by the reaction c) Most biological catalysts are enzymes (proteins) that act as a framework in which reactions take place d) An enzyme forms a complex with its substrate which turns into the product I) The complex can promote the reaction of two substrates by aligning their reactive groups and limiting their motion II) The enzyme may change when bound to the substrate, but eventually return to its original form. III)Enzymes orient substrate molecules, bringing together the atoms that will bond. IV) Substrate molecules bind to the active site of the enzyme. e) biological catalysts (enzymes and ribozymes) are highly specific I) three dimensional shape of the enzyme determines the specificity II) shape of enzyme active site allows a specific substrate to fit f) Enzymatic reactions I) The rate of a catalyzed reaction depends on substrate concentration II) Concentration of an enzyme is usually much lower than the concentration of a substrate III)At saturation, all enzyme is bound to substrate—reaction at maximum rate H) inhibitors a) inhibitors regulate enzymes: molecules that bind to the enzyme and slow reaction rates b) naturally occurring inhibitors regulate metabolism c) Types I) Irreversible inhibitor: inhibitor covalently bonds to side chains in the active site—permanently inactivates the enzyme (1) Example: DIPF in nerve gas II) Reversible inhibition: inhibitor bonds noncovalently to the enzyme, inhibiting its function (1) Competitive inhibitors bind to the enzyme active site (2) Noncompetitive inhibitors bind to the enzyme at a different site (not the active site) (i) The enzyme changes shape and its activity is reduced (ii) Allostery (allo, ‘different’, stereos, ‘shape’) Effector binding to a region separate from the avtive site alters enzyme activity 1. Activators bind to stimulate the enzyme 2. Inhibitors bind and inhibit the enzyme function I) Activation energy a) All chemical reactions require input of energy I) The amount of energy required to start a reaction is the activation energy (Ea) II) The larger the (E a the slower the reaction b) Activation energy changes the reactants into unstable forms with higher free energy—transition state intermediates c) Activation energy can come from heating the system—the reactants have more kinetic energy d) Enzymes lower the kinetic barrier by bringing the reactants together
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