Exam 2 Study Guide
Exam 2 Study Guide Bio1113
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Popular in Biology
This 13 page Study Guide was uploaded by Jessy Notetaker on Monday October 10, 2016. The Study Guide belongs to Bio1113 at Ohio State University taught by Dr. Larson in Fall. Since its upload, it has received 297 views. For similar materials see Biology in Biology at Ohio State University.
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Date Created: 10/10/16
Key Points for Cell Communication Membrane transport Membrane is selectively permeable Nonpolar molecules can cross easily Ions and polar molecules need a doorway Types of transport Simple diffusion Passive transport Moves a molecule from high concentration areas to low concentration areas Moves down its own concentration gradient Doesn’t require energy input Osmosis Molecules moving across a barrier Facilitated diffusion Passive transport Membrane does not allow ions and polar molecules Transport proteins help them diffuse passively across the membrane High concentration to low concentration Channel proteins Provide a doorway, but with no door Carrier proteins Changes shape Doorway with a swinging door High concentration to low concentration Active transport Requires ATP Movement of molecules against their concentration gradient Does not happen on its own Bulk transport Allows large amounts of molecules and particles to enter the cell Requires energy Endocytosis Cell encompasses the molecules/particles Brings things into a cell Tonicity Refers to the environment around a cell (gain/lose water) Isotonic Same amount of solute inside the cell as outside the cell Hypertonic More solutes outside of the cell More solutes = less water Water moves out of the cell Cells shrivel up Hypotonic More water in the environment Water moves into the cell Animal cells may burst Tophat questions Which of the following would move through the lipid bilayer most rapidly? Not a polar molecule Not a large molecule Not an ion CO 2 What statement about osmosis is correct? The presence of aquaporins would speed the process up Key points of Cell Signaling Local signaling Cell junctions allow signaling molecules to pass freely between adjacent cells Direct physical contact Cell to cell recognition via cell-surface molecules Can tell a neighboring cell what they are Paracrine signaling Molecule is released in a vesicle will enter other cells with the other cells that have the right receptors Long-distance signaling Use hormones Hormones travel through the bloodstream to reach target cells Ability of cell to respond depends on whether or not it has receptors that can bind to the signaling molecules 3 stages of cell signaling Reception Signal is detected by the cell A receptor protein on the surface of the cell (or inside the cell) binds to a signaling molecule (ligand) and transmits the signal Binding is very specific Usually causes the receptor to change its shape 3 types of membrane receptors G protein-coupled receptors G protein acts as an on/off switch When GDP is attached it is off Phosphate is attached When signaling molecule enters the receptor, it kicks GDP out and makes GTP that turns it on Phosphate is attached Makes GTPase Receptor tyrosine kinases (RTKs) Membrane receptors with enzymatic activity which attach phosphates to tyrosine residues Signal molecules bind outside of the cells and cause the monomers to come together and make a dimer One RTK may activate 10 or more different pathways Ion channel receptors Binding of a ligand causes conformational change Opens the channel Allows specific ions through Intracellular receptors Inside the cell Found either in the cytoplasm or nucleus Signaling molecule must be able to move through the membrane Small molecules Transduction The relay of signals from receptors to target molecules in the cell Often involves multiple steps More steps amplify the signal Allows for more regulation Message is often passed along through a change in shape of the protein Phosphorylation = add phosphate Protein kinase Makes a phosphorylation cascade Dephosphorylation = remove phosphate Phosphatases Second messengers Small, non-protein, water-soluble molecules cAMP Cyclic adenosine monophosphate ATP--> cAMP Calcium Used as a second messenger in both G-pathways and tyrosine kinase receptor pathways Increasing Ca2+ concentrations cause a variety of responses Muscle contractions Secretion Cell division Response Nuclear response Happens in the nucleus Transcription factor Binds to specific genes in the DNA and turns them on Makes mRNA to produce a protein outside of the nucleus Cytoplasmic response Turns on an enzyme that is already there Faster response Specificity and Coordination of response Termination of the signal In order to respond to new signal molecules, you have to be able to turn old signals off Binding to receptors is reversible The messengers to their inactive form GTP hydrolyzes to GDP cAMP to AMP Phosphatases remove phosphates to deactivate proteins Apoptosis Programed cell death Necessary for proper development Key points of metabolism Metabolism- all of the chemical reactions that occur in our cells to keep us alive Catabolic Break things down "cats break things" Spontaneous Free energy Portion of a system's energy that can perform work Exergonic reaction Products have a lower amount of free energy that reactants No input of energy Requires enzyme as a catalyst Positive ∆G Anabolic Build things up Body-builders use anabolic steroids Endergonic reaction Require an input of energy Products have more free energy than reactants Negative ∆G Key points of energy Energy- the capacity to cause change Kinetic Heat Kinetic energy associated with random movement of molecules Potential Chemical Potential energy available for release in a chemical reaction In our food Use food to make ATP Thermodynamics- the study of the energy transformations that occur in a collection of matter 1st law- energy can be changed but not destroyed Food can be used as energy to run or stored as fat 2nd law- every energy transformation or transfer increases the entropy of the universe Entropy- measure of disorder/randomness Lots of the energy that goes through transformation is lost as heat, which increases the entropy in the universe How is work done in a cell? Cells do 3 main types of work Chemical Building complex structures Transport Cell membrane Active transport Mechanical Muscle contractions Energy coupling Use the energy from exergonic reactions to power endergonic reactions ATP Bonds between phosphate groups can be broken by hydrolysis Building block for RNA Spring-like structure Lots of tension Lots of potential energy Exergonic reaction ATP + water = ADP + P i A phosphate group is cleaved off Energy is given off ATP causes… Motor proteins to move Transport proteins to change shape and move solutes Regeneration of ATP Reverse reaction must be endergonic Key points of energy and enzymes Enzymes are proteins (mostly) which act as a catalyst Not consumed by the reaction Act by lowering the activation energy Cannot make an endergonic reaction exergonic Can only speed up reactions that would occur anyway Starting molecules generally have to be contorted into an unstable form for a reaction to occur Only changes ∆G Ways to affect the reaction Stress the bonds in molecules Enzyme specificity Substrate: reactant acted on by the enzyme The reaction catalyzed by the enzyme is very specific Active site: region that binds with the substrate Only a specific substrate can fit Factors that Affect enzyme activity Proteins function best under certain conditions Temp pH Cofactors Nonprotein helpers Inhibitors Competitors Resemble substrate and competes for active site Non-competitors Bind to enzyme somewhere other than the active site Causes a conformational changes Enzyme regulation Metabolic pathways are tightly regulated by controlling when and where enzymes are active Allosteric regulation Binding of a regulatory molecule at one site affects the activity at a separate active site Can either stimulate or inhibit activity Works as an on and off switch Makes a stable and inactive form Cooperativity Binds to an active site Stable and active Key points of cellular respiration Redox reactions Transfers electrons Oxidation = loss of electrons Reduction = gain electrons Two main pathways Aerobic respiration Energy and fuel is converted to ATP ATP is from glucose Glycolysis Outside of mitochondria Makes 2 ATPs per glucose molecule Pyruvic acid Krebs cycle Makes 2 ATP Oxidative phosphorylation Makes water Oxygen is the final electron acceptor Anaerobic respiration Anaerobic respiration Oxygen is not the final electron acceptor Fermentation Generates energy without Oxygen or an electron transport chain Extension of glycolysis Glycolysis + a process to regenerate NAD+ Different types of fermentation Alcohol fermentation Pyruvate is reduced to ethanol Generate ATP and 2 NADH 2 NADH is oxidized back to 2 NAD+ Lactic acid fermentation Pyruvate is reduced directly by NADH to form lactate What is the purpose of fermentation reactions? To regenerate NAD+ so glycolysis can continue Respiration Stages Glycolysis Takes place in the cytosol Splits glucose into 2 molecules of pyruvate Net gain of 2 ATP Pyruvate oxidation and citric acid cycle Pyruvate oxidation Pyruvate enters the mitochondrial matrix through active transport 3 reactions take place COO is removed and gives off CO2 The remaining 2 carbon molecule is oxidized NADH is formed Citric acid cycle (Krebs/TCA cycle) A series of 8 steps Each step is catalyzed by an enzyme Occurs in the mitochondrial matrix 1 cycle produces: 2 CO2 molecules 1 GTP 3 NADH 1 FADH2 CoA and oxaloacetate are recycled Oxidative phosphorylation Generates ATP by adding a phosphate to ADP Happens in 2 steps Electron transport chain Collection of molecules in the mitochondria's inner membrane Electrons are dropped off by NADH and FADH2 No ATP production Chemiosmosis (energy coupling) Creates a gradient Energy coupling mechanism that uses energy stored in H+ ATP synthase Uses the energy of the H+ gradient to power ATP synthesis Located in the mitochondrial inner membrane H+ ions flow through ATP synthase down their concentration gradient Biosynthesis Reverse of cellular respiration Use molecules from food breaking down as building blocks Key points of photosynthesis Water + carbon dioxide + sunlight = glucose and oxygen Takes place in chloroplasts Has a double membrane (thylakoid membrane) Chlorophyll aids in the process Photosynthesis is a redox reaction Water is split and the electrons are transferred to CO2 Light Photons Discrete particles with a fixed amount of energy No mass! Chlorophyll is the pigment in leaves Pigment = substance that absorbs visible light Different pigments absorb different wavelengths of light Process of Photosynthesis Light reactions Convert light energy to chemical energy Reactants Light energy Water is split to provide electrons and Hydrogen ions Products ATP NADPH Oxygen Photosystems which capture light are located in the thylakoid membrane Light-harvesting complexes Contain pigment molecules which absorb light Pairs of chlorophyll reduce primary electron receptors Water acts as an electron donor to the P680 Produces Oxygen Dark reactions Calvin cycle Fueled by light reactions Uses the chemical energy stored in ATP and NADPH to reduce CO2 to sugar 3 phases Carbon fixation Rubisco attaches CO2 molecule to ribulose Reduction Makes G3P (sugar) Regeneration of CO2 acceptor (RuBP) Critical There has to be 3 CO2 molecules going at one time to make 1 net G3P Technically produces 6 G3P, but 5 must be used to regenerate RuBP For 1 G3P , the cycle uses 9 ATP and 6 NADPH Tophat Questions How is cellular respiration regulated? Follows principal of supply and demand Prevents cell from wasting energy Main mechanism of control is feedback inhibition ATP can inhibit ADP can stimulate What is the probable effect on ATP production when on a low calorie diet? ATP production would remain constant as stored fats or other body molecules are oxidized When you lose weight, how is fat eliminated from the body? It is released as CO2 and water In the thylakoid membranes, what is the main role of the pigment molecules? Transfer light energy to electrons The light energy reactions supply the Calvin cycle with… ATP and NADPH Where is the Oxygen coming from in Photosynthesis? When water is split, the electrons go to the P680 and the Oxygens bind together to make O2 How are the light reactions related to the Calvin Cycle? The light reactions provide ATP and NADPH while the Calvin Cycle returns ADP, Pi, and NADP+ to the light reactions What does not occur in the Calvin cycle? Release of Oxygen Which process is most directly driven by light energy? Removal of electrons from the chlorophyll molecules Where does the mass of a plant come from? The air Key points of mitosis Mitosis Cell theory: all cells come from other cells Reasons why cells divide Asexual reproduction Growth and development Tissue renewal Standard maintenance Maintain a surface area to volume ratio Types of cellular division Sexual division We will talk about this next week Asexual reproduction Mitosis Binary fission DNA Genome The DNA of a cell Prokaryotes Single circular chromosome Makes reproduction easy Eukaryotes Linear chromosomes Cells often contain 2 copies of each chromosome Homologous chromosomes Chromosomes Composed of chromatin DNA + histones (proteins) DNA is wrapped around histones like a spool of thread Structure Centromere- condensed region of the chromosome Telomere- a region of repetitive DNA sequences at the end of chromosomes Does not code for anything Kinetochore- disc-shaped protein that spindle fibers attach to Chromatid 2 chromatids make a chromosome Exact copy of each other Chromosomes are duplicated before division When the cell divides, the chromosomes are pulled apart, making 2 copies of a cell Binary fission Form of asexual reproduction Used by bacteria One circular chromosome Process DNA replicates DNA is pulled to the ends of the cell Cell wall and plasma membrane divide Wall and membranes completely form and cell divides Mitosis Eukaryotic cycle G1 Gap 1 Cell is growing Protein synthesis Organelle synthesis S DNA is replicated G2 Growth Synthesis of microtubules Makes sure there is enough mass to sustain 2 cells Cell cycle checkpoints G0 Metabolically active Majority of the cells in the human body are here Not actively reproducing Nuclear division 5 phases Prophase DNA condenses into chromosomes Nuclear envelope is disassembled Prometaphase Microtubules connect to the kinetochores Metaphase Chromosomes are lined up in the center of the cell Anaphase Chromatids are pulled apart Protein that held them together gets cut Telophase and cytokinesis Telophase Nuclear envelope starts to reassemble DNA uncoils into chromatins Cytokinesis Actual division Animal cells Membrane pinches in Makes a cleavage furrow Plant cells New cell wall is formed Golgi makes the building materials to the wall Cell cycle regulation Multiple checkpoints make sure the cells is ready to go on to the next step G1 ing into S Restriction point Most important in mammals If cell receives: Green light- continues to S phase Red light- exits cell cycle, enters 0 2 main regulatory molecules Cyclins Levels fluctuate cyclically Peak during mitosis Cyclin-dependent kinase Enzyme with a phosphate Function requires a cyclin Also peaks during mitosis G2 eckpoint Maturation-promotion factor (MPF) Uses cyclin-dependent kinases Targets include: Condensins Condenses the chromosomes Proteins involved in mitotic spindle formation Lamins Proteins involved in nuclear envelope breakdown/assembly Anaphase promoting complex (APC) Metaphase to anaphase checkpoint Ensures that there is a microtubule attached to each side of the chromosomes Tophat questions When the chromosome looks like an S, what phases could the cell be in? Metaphase or prophase Compared to the other phases, how much DNA is in a cell during metaphase? Metaphase contains twice the amount of DNA because replication has occurred, but has not split yet
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