Ch. 7 - 11 notes for exam #2
Ch. 7 - 11 notes for exam #2 LIFE 102-220
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This 39 page Class Notes was uploaded by Bailey Sniffin on Wednesday January 20, 2016. The Class Notes belongs to LIFE 102-220 at Colorado State University taught by Dr. Patricia Bedinger in Fall 2015. Since its upload, it has received 36 views. For similar materials see Attributes of Living Systems (Honors) in Biology at Colorado State University.
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CHAPTER 6 Extracellular Matrix ECM The ECM of animal cells is not as thick as a cell wall, but it is complex and important Fig. 6.28 in textbook Collagen fibers alone make up about 50% of the protein in your body ECM is very important in cellcell adhesion and communication Tight junctions: example shown = lining of gut o Must keep food and bacteria out of the body cavity Gap junctions: example = heart o The contractions of the heart must be coordinated o Specialized intercellular connections between animal cell types Membranes Structure and Functions Phospholipids: major component of most biological membranes o Form the lipid bilayers, which charged “heads” oriented toward water, hydrophobic tails on the inside Complex Biological Membrane 1. Lipid bilayer: o Phospholipids and cholesterol 2. Integral proteins: o Pass through the membrane = transmembrane 3. Peripheral proteins: o Associate with one side 4. ECM o On outside (note lots of carbohydrates and collagen) o Cytoskeleton on inside CHAPTER 7 Fig. 7.3 in textbook Lipids and proteins can move laterally (in the plane of 2 dimensions) in membranes o How do we know that membrane components can move in a membrane? Fig. 7.4 in textbook Lipids can also move in membranes – how fast they can move depends on the degree of saturation of the fatty acids in the lipids o Fig. 7.5 in textbook Most membranes are about as fluid as salad oil Text: cholesterol serves to stabilize membrane fluidity; a “fluidity buffer” o Newer idea: cholesterol is in lipid rafts The lipid bilayer of cell membranes is not uniform – that there exist more “ordered” microdomains that are detergent – resistant and that are enriched for cholesterol and glycolipids with longer hydrocarbon tails and signaling proteins – the existence of these is not absolutely proven Membrane proteins are also amphipathic o Fig. 7.6 in textbook Fig. 7.1 in textbook is of a membrane protein o = Aquaporin, a protein that forms a water channel in a membrane Functions of Membranes Why are membranes so important? o Membranes allow cells to regulate which molecules come into the cell and which exit the cell Selective permeability Water, dissolved carbon dioxide, and oxygen can pass freely through membranes Some hydrophobic molecules can also dissolve in, and pass through membranes o Ex. Steroid hormones ALL OTHER MOLECULES (and information) MUST ENTER AND EXIT WITH THE HELP OF MEMBRANE PROTEINS Functions of membrane proteins: o Many things happen at cell surfaces o Fig. 7.7 in textbook o HIV gets into cells by first binding to a complex of 2 transmembrane proteins (CD4 and CCR5) and then fusing with the plasma membrane Fig. 7.8 in textbook Some people are resistant to HIV because they lack CCR5 o How do membrane proteins get inserted into membranes? Through the endomembrane system Fig. 7.9 in textbook Exocytosis: soluble materials contained in a vesicle that fuses with the plasma membrane get secreted from the cell Diffusion: the tendency of molecules to distribute uniformly in a contained space o Note: diffusion is faster than mixing Ex. By cytoplasmic streaming When molecules redistribute as they move from an area of higher concentration to that of lower concentration, they are moving down the concentration gradient Osmosis: diffusion of water across a membrane o Fig. 7.11 in textbook The cytoplasm of cells is not pure water: it contains dissolved salts, sugars, and macromolecules o The cytoplasm of animal cells can be considered to be about 0.15 M salt Water concentration is important to living cells Molecules other than water, oxygen, and carbon dioxide cannot pass through membranes – they must use membrane transport proteins o If the passing of the transported molecules only goes down their concentration gradient and no energy is required, this is called facilitated diffusion Fig. 7.14 in textbook Neither osmosis nor facilitated diffusion require energy: both are passive transport o Solutes are moving DOWN their concentration gradients Cells have different internal environments than their external environments o Ex. The cell must be able to move molecules in and out AGAINST the concentration gradient If the molecule being actively transported is charged, an electrochemical gradient will be formed across a membrane o Fig. 7.17 in textbook o Important for respiration and photosynthesis In some cases, two different molecules will be transported at the same time: cotransport Summary: selectively permeable includes both active and passive transport How do bigger things get inside cells? o Vesicles Endocytosis: movements into cells using membranebound vesicles (reverse process is exocytosis) o Phagocytosis: cellular eating of particles including food o Pinocytosis: cellular drinking of dissolved substances and water o ReceptorMediated Endocytosis: some viruses like flu virus can sneak inside cells this way, rather than by direct membrane fusion like HIV Energy and Cells Cells require energy to live and function – the cell’s energy is derived from metabolic processes o Metabolism: to change = general o Catabolism: to break down Ex. Digestion, respiration generally do not require net energy input o Anabolism: to build up Ex: Photosynthesis, macromolecule synthesis generally do require net energy input Cells have complex metabolic pathways CHAPTER 8 Thermodynamics The study of energy transformation (fig. 8.2 and 8.3 in textbook) Energy: the capacity to do work o Some forms of energy: Kinetic = movement Potential = stored, including chemical Thermal = heat (the least useful to organisms) First Law of Thermodynamics: o Energy (like matter) can be transformed, but cannot be created or destroyed = the conservation of energy Ex. Potential energy in dam transformed into kinetic energy transformed into electrical potential energy o In many energyutilizing processes, mechanical or chemical, energy is not lost but is finally converted to heat, which is the “lowest quality” form of energy Second Law of Thermodynamics: o During energy transformations, a closed system becomes more disordered (entropy increases) Entropy = measure of disorder o Fig. 8.4 in textbook o If entropy always increases, how can life be so ordered? The earth, with its organisms, is NOT a closed system Capture of light energy to photosynthetic processes renew the energy Energy and Reactions G = free supply o The amount of energy in a system available for work o Fig. 8.5 in textbook The change in G is negative when the change is to a more stable state Exergonic reactions: free energy is released = negative () delta G o Ex. Catabolism Endergonic reactions: free energy is absorbed = positive (+) delta G o Ex. Anabolism Fig. 8.6 in textbook Making bonds absorbs energy; breaking bonds releases energy In other words, delta G describes the energy difference between 2 states Spontaneous: a change that occurs without a catalyst o () Delta G Life on earth is an open system ATP, a nucleotide that is the cell’s energy currency o Adenosine triphosphate o Fig. 8.9 in textbook ATP ADP but cellular respiration renews ADP to ATP When one of the bonds between the phosphate groups is broken, energy is released = () Delta G = 7.3 kcal/mole Cells couple ATP hydrolysis to endergonic reactions o Usually energy is captured from ATP hydrolysis by transferring a high energy phosphate to another molecule, which becomes more highly reactive Fig. 8.10 in textbook Spending money = more examples of endergonic processes (active transport and movement) o Notice the phosphorylated intermediates in Fig. 8.10 in textbook ATP Cycle Fig. 8.12 in textbook You have about 250 g of ATP in your body right now – but you use at least 40 kg per day! You need to constantly renew your supply The tragic Antechinus (marsupial)/ATP story: o Size of a mouse but not a mouse, the males go into a “Big Bang” reproductive mode at 10.5 months of age during which they do not eat, only fight and mate, and die two weeks later They are essentially unable to produce new ATP Enzymes Enzymes: Factors that catalyze (promote, increase the rate of) chemical reactions Vast majority of enzymes are proteins (not vice versa) but sometimes RNA molecules can be enzymes o Ribozymes o The name “ases” applies to enzymes A typical enzyme reaction: o A B A = substrate = Reaction catalyzed by enzyme B = Product Most chemical reactions (even those with a () Delta G) have an amount of energy required for initiating the reaction o The activation energy o Fig. 8.13 in textbook Enzymes lower the activation energy for a chemical reaction o Fig. 8.14 in textbook First step: o The substrate (not reactant) binds to the enzyme, which can cause its tertiary structure to change o Fig. 8.15 in textbook Enzymatic Reaction Cycle 1. The substrates bind to the enzyme at a particular place called the active site 2. The enzyme alters the substrates to make them more reactive (enter a “transition state”) 3. The chemical reaction occurs 4. The products are released from the enzyme, which is now available for another reaction o Fig. 8.16 in textbook The environment affects the enzyme’s activity o Most enzymes are proteins with a complex, folded tertiary/quaternary structure, highly dependent on hydrogen bonds o pH = acid or basic environment will affect protein folding (especially H bonds) and therefore enzyme activity o Temperature = high temperatures will cause protein unfolding, low temperature do not allow the necessary molecular movement For example: test enzyme activity under different conditions of pH temperature Fig. 8.17 in textbook Some kinds of small molecules can affect enzyme activity: o 1. Some are required for some reactions (inorganic ex. Metals like Mg++ = called a cofactor; if organic, ex. Vitamins = called a coenzyme) o 2. Some small molecules are specific enzyme inhibitors Inhibitors Inhibitors are either competitive or noncompetitive o You can “overcome” competitive inhibition by increasing the substrate competition o Often the drug will be similar to the normal substrate o Increasing the substrate concentration does NOT help! Enzyme inhibitors in medicine: o 1. Aspirin and other analgesics; inhibitors of prostaglandin synthesis o 2. Anticholesterol drugs: inhibit a ratelimiting enzyme for cholesterol biosynthesis o 3. Many antibiotics o 4. AIDS “cocktail” includes competitive DNA synthesis inhibitors Sometimes the end product can “turn off” an entire synthetic pathway by inhibiting the first enzyme of the pathway = “feedback inhibition” o Fig. 8.21 in textbook In Chapter 8, SKIP: Derivation of delta G Allosteric effects Cooperatiivity Enzyme evolution CHAPTER 9 Energy Transformations of Photosynthesis and Respiration Fig. 9.2 in textbook Cellular respiration: provides energy for cellular work o Fig. 8.10 in textbook The point of respiration Rs: o A simple nutrient (glucose) gets slowly broken down; as each covalent bond is broken, some of the energy is captured and converted to ATP All aerobic organisms use oxygen in this process During Rs, ADP is phosphorylated to the high energy triphosphate form Summarizing Rs = o Glucose + Oxygen Carbon Dioxide + water o C H 6 126 6 6 C2 + 6 H 2 2 o One way to look at it: H’s are getting “plucked off” the glucose molecule and put onto a different molecule “Plucking off” electrons (and a proton often comes along for the ride) and putting them on other molecules = Redox reactions: Reduction/Oxidation Reactants and products are always paired Names are somewhat counterintuitive: o Oxidation – electrons are removed o Reduction – electrons are added Often protons will travel with the electrons o Redox are always in pairs – one molecule is oxidized and one is reduced on each side of a reaction Ex. Combustion of methane o Oxidation/Reduction can be explosive: Rs can conserve some of the energy released Overall () Delta G Final e acceptor is oxygen In Rs, C 6 12 6 2 2 6 H O 2 Glucose is oxidized Oxygen is reduced Phosphorylation: a process in which a phosphate group is added Kinase: an enzyme that attaches phosphates (performs a phosphorylation) Dehydrogenase or oxidase: enzyme that oxidizes a substrate During respiration, electrons gets shuttled around by a particular kind of molecule: NAD o Fig. 9.4 in textbook A Dehydrogenase transfers e (and H+) to NAD, reducing it to NADH 3 Important Roles for Nucleotides (So Far) Monomers of nucleic acids Energy currency Carriers of electrons An Overview of Respiration Fig. 9.6 in textbook 1. Glycolysis: breaking of glucose in cytoplasm 2. Oxidation of organic molecules in citric acid cycle in mitochondria 3. Most ATP is made during oxidative phosphorylation in mitochondria The First Steps – Glycolysis (Sugar Breaking) Occurs in cytoplasm/cytosol Glucose (6carbon organic molecule) gets split into 2 3carbon molecules o Pyruvates Mouth (enzymes) Stomach (acid) Intestine (enzymes) Energy investment phase: o Glucose is phosphorylated twice, using 2 ATPs Fig. 9.9 in textbook Product is very unstable Next phase, energy payoff: o 2 ways: 1. Electrons transferred to NAD NADH (think of this as potential energy) 2. Get some ADP + organicP ATP 1. First redox: o Oxidation of 3GP NADH 2. ADP is phosphorylated by substratelevel phosphorylation Energy payoff part II: o A second substrate level phosphorylation occurs End of glycolysis = two 3carbon acids (pyruvates) and 2 net ATPs o NADH Citric Acid Cycle Fig. 9.8 in textbook Once pyruvate is formed, it can either enter the mitochondrion and continue in Rs, or it can remain in the cytoplasm and be fermented to lactate or ethanol o Fig. 9.18 in textbook In the absence of O2, NADH builds up in the cytoplasm and fermentation results o Fig. 9.17 in textbook o Alcoholic fermentation: in yeast (and some bacteria) o Lactic acid fermentation: in yogurt and muscle tissue Pyruvate Processing If pyruvate enters the mitochondrion, it is immediately decarboxylated to a 2carbon compound attached to a larger compound (CoA) and the first CO2 is released; we get another NADH, too Fig. 9.10 in textbook Let’s assume that oxygen is present: o Pyruvate enters the mitochondria and Rs continues o Inner membrane folds = cristae o Mitochondria have a center matrix involving the citric acid cycle Citric Acid Cycle Old name = Krebs cycle A circular disassembly line Occurs in the mitochondrial matrix o Fig. 9.12 in textbook Organic molecules are oxidized o Producing NADH and other reduced carrier FADH2 and some ATP 2 CO 2s released for each cycle, some ATP o Fig. 9.11 in textbook Stages: o The 2 carbon fragment gets added to the first carrier (4carbon oxaloacetate) o As oxidation occurs, savings in potential energy: 3 NAD NADH 1 FAD FADH 2 o Carbon flies away o Also substrate level phosphorylation of ADP ATP By the end of the citric acid cycle: o All carbons from glucose are released as CO ,2but NO oxygen used yet! o Some ATP has been generated (about 2 net ATP per glucose) o NADH Electron Transport Chain Fig. 9.13 in textbook These are all membrane proteins most often with metal cofactors including iron and/or sulfur, in the inner mitochondrial membrane/cristae (except Q) o Q = ubiquinone Electrons on NADH (and FADH2) are separated from protons H+ As the proteins pass electrons, they pump H+ from the matrix into the intermembrane space o Fig. 9.15 in textbook Creates an electrochemical proton gradient across the inner mitochondrial membrane o Called the “Protonmotive force” A source of potential energy Think of the protonmotive force like a dam: o There’s a build up in the intermembrane space of higher protons (H+) = low pH and more acidic o Low H+ = higher pH in matrix o There are turbines in the dam that allow some water to pass through, much like the proteins on the membrane Protons can flow back into the matrix like this The “turbine” is ATP synthase Complexes in the inner mitochondrial membrane has 46 polypeptide chains Electrons and protons are pulled off NADH (oxidation) and transferred to a series of ironsulfur clusters in the complex – the protons diffuse through the complex A conformational (tertiary) change in the complex causes protons to be transferred across the membrane ATP synthase: This large protein complex (8 different proteins = quaternary structure) drives the phosphorylation of ATP using the energy of the electrochemical gradient (protonmotive force) across the inner mitochondrial membrane Chemiosmosis: process where movement across a membrane (H+ here) causes a chemical reaction to occur o The coupling of a membrane potential (H+) with a chemical reaction (ADP + Pi ATP) o This kind of phosphorylation of ADP to ATP is called oxidative phosphorylation because it results from the oxidation of food, then NADH (and FADH ) u2es inorganic phosphate (P) i Cyanide poisoning: inhibitor of cyt c oxidase (last step of e transport) almost any way death occurs is du to the failure of Rs Electron Transport Chain (successive oxidation steps) + chemiosmosis (driven by the proton motive force) = oxidative phosphorylation of ADP ATP The last steps of Rs make the most ATP Respiration for each input glucose get about 38 ATP o About 40% efficient o Fig. 9.19 in textbook How do you get energy from the different kinds of foods that you consume? The Energy Transformation of Photosynthesis and Respiration Photosynthesis: o Produces food o Heterotrophs: organisms that must obtain food o Autotrophs: organisms that produce their own food by photosynthesis Johann Baptiste von Helmont o Mid1699’s o “Last alchemist and first chemist” o Coined the word “gas” o Contemporary to Galileo, also put under house arrest by Inquisition o His question: “do plants grow by consuming soil?” The experiment: plant a 5 lb. willow sprig in 200 lb. of soil, watered the growing plant and waited 5 years Result: the tree weight 164 lbs. and the soil lost 2 oz His conclusion: plants grow by consuming water o SO. o Where do plants really get their food? From the carbon dioxide in the air Joseph Priestley o English “dissenting” minister and natural philosopher o His question: do plants “repair” air that has been “injured?” o His experiment: put a mouse in a closed off container where no gas exchange was possible (the mouse died). Then he put a mint plant in the container with the mouse and found that it survived only in the company of the plant with access to light o Conclusion: plants can repair “dephlogisticated” air CHAPTER 10 Photosynthesis 6CO 2from air) + 12H O 2 C H O6 +12O6 + 6H 2 2 Requires energy, obtained from sunlight Another Redox reaction: o Carbon dioxide is reduced, water is oxidized Chloroplasts: o Contain folded thylakoids A stack of thylakoids is called a granum An overview of Photosynthetic reactions: o 2 kinds of reactions occur: o 1. Light reactions in thylakoid Grana o 2. Carbon fixation in stroma (Calvin Cycle) Light Light has a dual nature, including properties of particles or quanta = photons o Photons have neither charge nor mass o They do have energy and can be detected The photoelectric effect explained by Einstein: o If you have a metal sheet and shine light on it, the sheet would become positively charged Electrons would be emitted Light has properties of waves – energy of light is defined by its wavelength (λ) How do photosynthetic organisms capture light? o Chlorophyll Light absorbing “head” Fig. 10.11 in textbook Hydrocarbon tail inserts it into the thylakoid membrane Chlorophyll is green because it does NOT absorb green light! How we measure light: o Fig. 10.8 in textbook Absorption spectrum of pure chlorophyll Action spectrum (λ at which a lightdependent reaction works: Ps works at red and blue λ Bioassay: Engelmann’s wonderful experiment with a filamentous algae, light and motile bacteria that is attracted to 2 o On a microscope slide, Engelmann had an algae that was photosynthetic o Then he added bacteria to the slide o The slide was all in water Found out bacteria can swim towards an attractant In this case, it was oxygen Theodor Engelmann o German, 1880’s scientist + professor, contemporary of Lincoln o Question: Does Ps produce more O at different light wavelengths? 2 o Experiment: Shine alight spectrum on algae in the presence of aerotactic bacteria o Results: Bacteria accumulate in regions where blue or red light is being shown o Conclusion: More O is 2roduced in the presence of blue or red light Chlorophyll When light hits a chlorophyll molecule, an electron is excited; if nothing else happens, get fluorescence light (light of a different wavelength emitted as the excited electron returns to its prior state) Chlorophyll is not found free in plant cells, it is in a complex with proteins – this kind of complex is a “photosystem” (PSI and PSII) with more than 10 different proteins and several 100 chlorophyll molecules o Fig. 10.13b in textbook o Photosystems are in the thylakoid membranes in the grana Light energy is captured when a photon hits an “antenna” pigment, excites an electron High energy state of the antenna pigment: passed from chlorophyll to chlorophyll molecule until it reaches particular chlorophyll pair in the reaction center of the Ps called P(igment)680 The reaction center chlorophylls (P680) are next to a molecule called the primary electron acceptor – it “grabs” the excited electron from the chlorophyll before it can return to its ground state o Takes a billionth of a second The oxidation o is the first chemical reaction of the Light Reactions – light energy has been converted to a chemical energy o IMPORTANTFOR LIFE ON EARTH What about the poor reaction center chlorophylls? o They are lacking electrons o They have a positive charge = P680+ P680+ splits water through a lightdriven reaction into protons, electrons, and oxygen by oxidation o Photolysis o P680+ gets the electrons and we get the oxygen Fig. 10.14 in textbook The splitting of water is a highly endergonic process o P680+ is the most powerful oxidizing agent in biology Chloroplasts can split water to get oxygen ***** Electrons from P680 are passed from the primary electron acceptor down an electron transport chain in the thylakoid membranes o A proton motive force is generated across the thylakoid membrane and ADP phosphorylation occurs by chemiosmosis This time powered by light = photophosphorylation H 2 P680 ETC P700 ETC NADPH reduction in the Calvin Cycle Three Ways to Phosphorylate ADP ATP 1. Substrate level phosphorylation e.i. Glycolysis, Citric Acid Cycle o Phosphate is transferred from an organic molecule to ADP, by a kinase enzyme Phosphorylation of ADP ATP Source of Phosphate Driven By Substrate Level Organic Molecules Kinases Oxidative Pi Oxidation of food Photo Pi Light energy Photophosphorylation A protonmotive force = an electrochemical proton gradient across a membrane is established (a pH difference of 3 = 1000x difference in [H+]!) This force is used by an ATP synthase to phosphorylate ADP so that ATP is built up in the stroma Chemiosmosis in Rs and Ps: o Rs: Powered by oxidation of food by Enzymes = oxidative phosphorylation o Ps: Powered by oxidation of chlorophyll by light = photo phosphorylation Photosystems There are 2 different photosystems o So far, we’ve only been dealing with events in Photosystem II In photosystem I, light oxidation of P700 happens o The electron “hole” in PSI P700 gets filled by electrons originally from PSII P680 o Called the =Z scheme o Fig. 10.14 in textbook Reduction of NADP The final electron acceptor in the electron transport chain from photosystem I is NADP, a dinucleotide electron carrier similar to NAD What other part of photosynthesis has occurred in the Light Reactions? Input: water and light energy Output: oxygen, NADPH, and ATP Calvin Cycle / Carbon Fixation Occurs in the stroma of the chloroplast Bottom line: carbon dioxide gas gets “fixed” = added to organic molecules, for a net synthesis of sugars, an endergonic process using the ATP and NADPH from the Light Reactions o This creates life on earth 1. The big, slow enzyme Rubisco (most abundant protein and enzyme on earth) adds CO from air (only 2 0.03% of air!) to an organic molecule RuBP – CO g2s has now been “captured” or fixed = transformed from gas to solid o This is Phase 1: carbon fixation 2. ATP is used to activate intermediates and NADPH is used to reduce organic compounds, some of which get shunted off for final steps of glucose synthesis o This is Phase 2: reduction 3. Regeneration of the molecule – get used to regenerate the original 5carbon compound (RuBP) that can accept CO 2(requires ATP) o This is Phase 3: regeneration Summary of Ps: Figure 10.22: be able to fill in processes Exergonic = catabolic Spontaneous = () delta G Relationship of chemiosmosis to oxidative phosphorylation: o ETC + chemiosmosis ETC: As that occurs, the proton motive force is generated Chemiosmosis: Phosphorylation used to drive H+ through ATP synthase to drive the chemical reaction of ADP + Pi CHAPTER 11 Cell Communication With environment: nutrients or other chemical attractant = chemotaxis Light = phototaxis (movement) or phototropism (growth) Between cells: mating = recognition between cells of different mating types Other examples of communication between cells: o Transmission of nerve impulses o Hormonal signaling Fig. 11.5 in textbook Cell communication: direct contact o Fig. 11.4 in textbook Ex. Sperm and egg, immune system The general pathway of cell communication can be divided into 3 phases: o 1. Reception o 2. Transduction o 3. Response Reception: o Signals are received by receptor proteins Ligands: the signaling molecules that bind to the receptor The signals themselves, which may be small molecules or large proteins, bind VERY specifically to their Receptors – molecular recognition is largely determined by hydrogen bonding and other subtle kinds of interactions Signals/ligands: o Hormones o Neurotransmitters o Taste molecules o Light o Odorants o Metals and other dissolved elements o Organic metabolites o Vitamins and other consumed nutrients, toxins, and medications o Stress molecules like histamine Example: cytokines, or interleukins (ILs) = peptides that allow communication between white blood cells Most receptor proteins are transmembrane proteins in the plasma membrane o 3 of the four types we will discuss are transmembrane Fig. 11.8 in textbook o The ligand binds to the extracellular domain of the receptor Flu Slides Part 2 Vaccines: o A harmless form of the pathogen (virus, bacteria, etc) which is administered to cause a production of antibodies to the pathogen before infection so that when you are exposed to the real pathogen, you will have a rapid immune response to it o TYPES of vaccines: Killed by chemical treatment – flu, polio, Hep A Live “attenuated” – passaged through tissue culture to weaken the virus Yellow fever, measles, mumps Toxin – inactivated chemical rather than actual pathogen Tetanus, diphtheria vaccines Recombinant – cloned gene produces a protein expressed in bacteria or yeast Hep B, HPV, a single viral protein (ex. A viral capsid protein) is used Why do we need a new flu vaccine every year? Who decides what viruses are used to make a flu vaccine? o There are many strains of flu and a few become dominant each year o The vaccine strain selection process requires surveillance info, collected yearround o In late January of each year, the FDA reviews worldwide surveillance data at 130 flu centers around the world o By midFebruary, the WHO completes its review and makes recommendations for the Northern Hemisphere vaccine o In March, about 3 strains of virus are selected for the U.S. influenza vaccine Immunization: artificial induction of immunity by the injection of a foreign object (=antigen in the vaccine) into an individual causing the body to generate an immune response to the object – infected cells will be identified and killed Once you get your vaccination, you will produce Bcells making antibodies (proteins that bind to antigens) to the virus; if you are exposed after several weeks, your body can eliminate the virus (even years later) For the exam: read through to the 4 receptors 4 kinds of receptor proteins we need to know: 1. Gprotein Associated Receptors Figure 11.8 in textbook G Proteincoupled receptor o Everything you can smell is related to gprotein receptors! Humans can sense and remember 10,000 different odors We have 1000 different odorreceptor genes o 3D structure of a Gprotein receptor – adrenaline/epinephrine is the ligand 2. Tyrosine Kinase Receptors o When ligand binds to the receptor, it dimerizes and an inherent protein kinase is activated The receptor (auto)phosphorylates and becomes active Once this happens: a series of reactions occurs for the transduction process 3. Ligand Gated Ion Channel Receptors o Transmembrane proteins that can open up and let ions into the cell o Propagation of nerve impulses o Protein channels through membranes that are opened when the protein binds a specific ligand = ligand gated ion channels o The ligand is NOT the ion! Think of this analogy: A gate with a key where the key is the ligand – and you (the ion) get to go through the gate Example: at a synapse between two nerve cells, the key (ligand) is the neurotransmitter and IONs can flow through the channel if the key is in the lock How do we detect pain? o Special nerve cells called nociceptors; different kinds of pain (chemical, temp, mechanical) are detected by different membrane receptors in nociceptors o Ligandgated channels, tyrosine kinase and Gprotein receptors are all involved in pain reception 4. Intracellular Receptors (NOT transmembrane) Example: steroid hormones o Steroids are hydrophobic molecules that can pass through membranes without the help of a protein – their receptor is in the cytoplasm o Once the ligand (steroid) is bound, the receptorligand complex moves to the nucleus and activates new gene expression Fig. 11.9 in textbook Terms to keep straight: o Intra within/inside, endo also means inside (endocytosis) o Inter between o Extra outside, exo also means outside (exocytosis)
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