BSC Exam 2 Study Guide
BSC Exam 2 Study Guide Biology 114
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This 9 page Study Guide was uploaded by Hannah Tomlinson on Saturday October 8, 2016. The Study Guide belongs to Biology 114 at University of Alabama - Tuscaloosa taught by Dr. Stevan Marcus in Spring 2016. Since its upload, it has received 179 views. For similar materials see Principles of Biology in Biology at University of Alabama - Tuscaloosa.
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Date Created: 10/08/16
Biology Exam 2 Chapter 7 When phospholipids are placed in water, they spontaneously form membranes These membranes exhibit selective permeability -Allows some substances to cross it more easily than others These are the most abundant lipids in most membranes They are amphipathic (contains hydrophobic and hydrophilic regions) Fluidity in the membrane can be increased by the presence of unsaturated hydrocarbon tails, which results in kinks and the inability to pack closely together Fluidity in the membrane can be decreased by the presence of saturated hydrocarbon tails The presence of cholesterol will reduce membrane fluidity because it restricts the lateral movement of phospholipids The membrane will remain fluid at lower temperatures if it’s rich in unsaturated hydrocarbons Plants increase their unsaturated phospholipids in the fall and winter to prevent the membranes from solidifying during cold temperatures 2 types of membrane proteins 1. Integral: transmembrane proteins with hydrophobic regions that span the membrane -They have hydrophilic ends that are exposed to solutions on either side of the membrane 2. Peripheral: not embedded in the lipid bilayer -Loosely bound to the surface of the membrane, often to the exposed portions of integral proteins -Attached to the cytoskeleton or ECM for structural support Diffusion is a spontaneous process Diffusion is passive transport because energy from ATP is not used Each substance will diffuse down its concentration gradient, unaffected by the concentration of others A substance will diffuse from where it is more concentrated (a substance will diffuse down its concentration gradient) Osmosis is passive transport It is the movement of water If a solute cannot pass through a membrane but water can, the water will diffuse to the area of higher solute concentration Hypertonic: the solution with a higher concentration of solutes Hypotonic: the solution with a lower concentration of solutes Isotonic: solutions of equal solute concentration Isotonic environment: the volume of water flowing across membrane will be stable Hypertonic environment: the cell will lose water to environment; shrivel up and die Hypotonic environment: the cell will take up water faster than it can leave; cell will swell and lyse Osmoregulation: the control of water balance -e.g.: paramecium Facilitated diffusion: the process whereby polar molecules and ions (which are impeded by the lipid bilayer of a membrane) are able to pass through with help of transport proteins Facilitated diffusion is spontaneous and passive transport High concentration Low concentration Active transport: the movement of a substance across a biological membrane against its concentration or electrochemical gradient It is the movement of a solute from a less concentrated side to more concentrated side For active transport ATP and membrane proteins are required Small molecules either pass directly though the lipid bilayer of a membrane or are pumped or carried across by transport proteins Passive transport: no energy required Exocytosis: the cell secretes macromolecules by the fusion of vesicles with the plasma membrane Endocytosis: the cell takes in macromolecules by forming vesicles from the plasma membrane -Pinocytosis: the cell engulfs fluids -Phagocytosis: the cell engulfs food particles Chapter 8 Metabolism: all the chemical changes that happen in an organism Enzymes: serve as catalysts (chemical agents that change the rate of a reaction without being consumed by the reaction) 2 types of pathways metabolism can follow -Catabolic: breaks down complex molecules to simpler compounds (from proteins to amino acids) -Anabolic: consume energy to build complex molecules from simpler ones (synthesis of proteins from amino acids) -These work together in order to make energy coupling. Energy coupling: interaction between catabolic and anabolic pathways Energy= capacity to do work Kinetic energy: when energy is associated with the relative motion of objects Potential energy: an object not presently moving may still possess energy (this is not kinetic energy) Chemical energy: the potential energy available for release in a chemical reaction -Ex.- molecules store energy because of the atom arrangement -Catabolic pathways release energy by breaking down complex molecules (through hydrolysis) Thermodynamics: the study of energy transformation that occur in a collection of matter 2 important laws of thermodynamics apply to biological systems -1 law of thermodynamics nd st -2 law of thermodynamics 1 Law Energy can be transferred and transformed but it cannot be created or destroyed AKA conservation of energy -e.g.: an electric company does not produce energy but it converts it to a form we can use -e.g.: 2nd Law Every energy transfer of transformation increases the entropy of the universe -Entropy is a measure of disorder -Entropy is less apparent tin biological systems because it takes the form of heat -Biological systems are not very efficient because of a great deal of energy is dispersed or lost through heat Heat is energy in a random state, we have not created or destroyed energy. Free energy (G) is the portion that is available to perform work Spontaneous does not necessarily mean fast, simply that it can occur eventually without energy -Spontaneous reactions have negative change in G value -Process that have a positive or zero change in G are never spontaneous Max stability=equilibrium Most chemical reactions are reversible (and proceed forward and backward at the same rate) Exergonic: reactions proceed with a net release of free energy (“energy outward”) and delta G is negative Endergonic: reactions absorb free energy from the environment (“energy inward”) and delta G is positive Catabolic processes DOES involve hydrolysis. Anabolic processes DOES involve dehydration reactions. Eating is an example of the First law of thermodynamics. An enzyme catalyzes a reaction by lowering the activation energy to the reaction. Enzymes act upon substrates Chapter 9 Ultimate source of energy is the sun Autotrophic organisms (green plants) convert sunlight into energy Heterotrophs eat the plants to obtain energy catabolically Autotrophs: convert sunlight into energy that is stored in the bonds of organic molecules (glucose) - Anabolic process of photosynthesis Heterotrophs: obtain energy catabolically via the breakdown of organic nutrients that must be ingested The mitochondria of eukaryotes use the organic products of photosynthesis as a fuel for cellular respiration Cellular Respiration: C 6 O12 6O 6C2 + 6H O2+ ATP 2 heat Glucose plays an essential role in cell metabolism A cell must use the energy stored in food molecules to make ATP Redox reactions: a chemical reaction resulting in the transfer of one or more electrons from one reactant to another Oxidation: loss of electrons from a substance Reduction: addition of electrons to a stubstance -OIL RIG (oxidation is loss, reduction is gain) Na + Cl yields Na + Cl - -Na is oxidized and Cl is reduced -Sodium is the reducing agent -Chlorine is the oxidizing agent In cellular respiration: glucose is oxidized because it loses electrons and oxygen is reduced (it gained water) and energy will be generated in the process By oxidizing glucose respiration takes the energy out of storage and makes it available to ATP synthesis After electrons are cleaved, they are usually passed first to an electron + acceptor—a coenzyme called NAD Each NADH + H molecule formed during respiration represents stored energy that can be used to make ATP Glycolysis occurs in the cytosol Breaks glucose into 2 molecules of pyruvate Pyruvate is not completely oxidized, energy remains Glycolysis uses 2 ATP and produce 4 ATP This ATP is generated directly in a few steps of glycolysis by substrate- level phosphorylation -A mode of ATP synthesis that occurs when an enzyme transfers a phosphate group from a substrate to ADP Glycolysis is harvested by -Fermentation pathway—anaerobic process (no oxygen) -Aerobic Respiration—aerobic process (with oxygen) 2 types of fermentation -Lactic acid fermentation: lactic acid is the end product -Alcohol fermentation: ethanol and CO are2the end products Fermentations do not oxidize glucose completely Still much energy left in fermentation end products- lactate and ethanol Without O ,2cannot extract more energy Wasted energy… Electrons end up in fermentation end products, no energy obtained Carbon ends up in fermentation end products, still energy present since not completely oxidized Aerobic respiration Consists of -Glycolysis -Oxidation of pyruvate -Citric acid cycle -Electron Transport System Citric Acid Cycle occurs in the mitochondria matrix - Decomposes a derivative of pyruvate to CO 2 -Donates electrons to the electron transport chain - A small amount of ATP is generated by substrate-level phosphorylation -2 different electron carriers: NAD and FAD (Flavin adenine dinucleotide) There is energy in the electrons removed by NAD and FAD in citric acid cycle Energy of electrons converted to ATP energy by Electron Transport System The electron transport chain is embedded in the inner membrane of the mitochondrion As electrons are passed from one carrier to the next, they lose energy, which can be converted to ATP energy Electrons are passed down a series of steps from one molecule to another until they reach the final electron acceptor (O ) 2 They are combined with hydrogen ions and molecular oxygen to form water Electron transport accepts electrons from the breakdown product of + 2 both glycolysis and citric acid cycle (from NADH + H to FADH ) Mitochondrion: powerhouse of the cell- most of ATP of respiration made there Chemiosmosis: a mechanism for energy coupling + A H gradient is used to transfer energy from redox reactions to the synthesis of ATP Protein complex called ATP synthase is used ATP synthase is located in the inner membrane of mitochondria (many of the copies of it) It is the enzyme that actually makes ATP It has specialized channels in the inner membrane of the mitochondria that allow hydrogen ions to pass through How it works: as electrons are passed down the chain, protons (hydrogen) are pumped out into the matrix A H gradient forms and then they flow down their gradient through an + H channel in ATP synthase molecules If a single glucose molecule is used. Then 2 pyruvates are produced. In a specific glycolysis reaction, 10 pyruvate molecules are produced. From this info, we know that this reaction started with 5 glucose molecules. Following the breakdown of glucose by glycolysis, if there are no oxygen present organisms will undergo fermentation Fermentations are inefficient and waste some energy. Chapter 10 Photosynthesis: The conversion of solar energy to chemical energy Autotrophs: they sustain themselves without eating anything derived from other living beings and they produce their organic molecules from CO 2nd other inorganic raw materials obtained from the environment Photosynthesis occurs mostly in the leaves in tissue called mesophyll (tissue in the interior of leaf) Green leaf color is from chlorophyll, the green pigment located within the chloroplasts The light energy absorbed by chloroplasts drives the synthesis of food molecules in the chloroplast CO 2nters a leaf and O ex2ts through pores called stomata Stroma: the fluid within the chloroplast Thylakoid membranes are a system of interconnected membranes that divide the stroma from the thylakoid space Chlorophyll is located in thylakoid membrane Grana: when thylakoid are stacked on top of each other 2 sets of reactions that cooperate to convert light energy to chemical energy -Light reactions (photo) occur in thylakoid membrane -Calvin cycle (synthesis) occurs in the stroma Light reactions convert solar energy to chemical energy - Light and Water that go into the reaction and generate ATP - NADPH is the electron carrier - Solar power generates ATP (energy) and NADPH (electron carrier) - They shuttle over to the Calvin cycle - All the energy (ATP) is dedicated to powering the Calvin cycle Calvin cycle incorporates CO fr2m the air into organic molecules by attaching CO2 to a 5-carbon sugar named ribulose biphosphate (RuBP) - Occurs in stroma - Uses ATP and NADPH (generated form light reaction) to produce sugar - Rubisco is the enzyme that catalyzes this reaction - The light reactions sustain the Calvin cycle by regenerating ATP and NADPH 3 phases of the Calvin cycle - Carbon fixation (Carboxylation) - Reduction - Regeneration of RuBP When oxygen is released as a result of photosynthesis, it is a direct by- product of splitting water molecules The NADPH required for the Calvin Cycle comes from light reactions The primary function of the Calvin Cycle if to synthesize simple sugars from CO 2 Photosynthesis is a redox reaction. This means H O i2 oxidized during the light reactions and CO i2 reduced during the Calvin cycle. Chapter 11 Signal transduction pathway: a process by which a signal on a cell’s surface is converted into a specific cellular response through a series of steps 3 types of cell communication in animal cells -Local regulators -Distant communication -Direct contact between cells Local regulators: substances that are secreted from one cell and then influence cells in the vicinity 2 types -Paracrine signaling: a secreting cell acts on nearby target cells by discharging molecules of a local regulator into the extracellular fluid (growth factors) -Synaptic signaling: a nerve cell releases neurotransmitter molecules into a synapse (the narrow space between transmitting and target cell) Distant communication: hormone signaling - Hormones signal target cells at much greater distances - In animal cells, specialized endocrine cells secrete hormones into body fluids, often the blood - Hormones may reach almost all body cells - Only specific target cells recognize and respond to a given chemical signal Direct contact between cells: cell junctions - Allow signaling substances to pass freely between adjacent cells - Occurs by direct contact between molecules on their surfaces - Important for embryos to develop and in immunology 3 stages of cell signaling -Reception -Transduction -Response Reception: the target cells detection of a signal coming from outside the cell - A chemical signal is detected when it binds to a cellular protein - This is usually at a cell’s surface - The chemical signal behaves as ligand -Ligand binding causes a receptor protein to undergo a shape change - Ligands are usually water soluble and too big to freely diffuse through the cell membrane - The receptor is usually a plasma membrane protein G-protein systems are involved in many diseases including infections like cholera and botulism. These bacteria make their victims ill by producing toxins that interfere with G-proteins. Transduction: the binding of the signal molecule changes the receptor protein in some way, initiating the process of transduction The transduction stage converts the signal to a form that can bring about specific cellular response G-proteins act like ON/OFF switches Bind guanine nucleotides: -GDP bound = OFF (inactive) -GTP bound = ON (active) -GTP powers the entire reaction Binding of ligand to G-protein-coupled receptor leads to displacement of GDP for GTP and subsequent binding to a downstream protein (usually an enzyme) Extremely wide-spread -Blood vessel development -Olfaction (smell) -Vision Highly conserved across species Ras -50% of colon cancers -90% of pancreatic cancer The molecules in transduction pathway is known as relay molecules Protein phosphorylation: a widely used process for regulating protein activity The general name for an enzyme that transfers phosphate groups from ATP to a protein is a protein kinase -They act on substrate proteins Cellular response: the transduced signal finally triggers a specific cellular response Many different responses -Enzyme response -Rearrangement of the cytoskeleton -Activation of specific genes in the nucleus G-protein coupled receptors are composed mainly of alpha helix secondary structure with many nonpolar type amino acids. The type of enzyme that added a phosphate onto this molecule is called a kinase.
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