Presentation on theme: "Enzymes are necessary because they cause reactions to happen."— Presentation transcript:
1Enzymes are necessary because they cause reactions to happen.
2Metabolism Chemical reactions of life forming bonds between molecules dehydration synthesissynthesisanabolic reactionsbreaking bonds between moleculeshydrolysisdigestioncatabolic reactionsThat’s why they’re called anabolic steroids!
4Enzymes work by decreasing the potential energy difference between reactant and product
5Catalysts So what’s a cell got to do to reduce activation energy? get help! … chemical help…ENZYMESCall in the ENZYMES!G
6As a result of its involvement in a reaction, an enzyme permanently alters its shape.
7Enzymes vocabulary substrate product active site active site products reactant which binds to enzymeenzyme-substrate complex: temporary associationproductend result of reactionactive siteenzyme’s catalytic site; substrate fits into active siteactive siteproductssubstrateenzyme
8Properties of enzymes Reaction specific Not consumed in reaction each enzyme works with a specific substratechemical fit between active site & substrateH bonds & ionic bondsNot consumed in reactionsingle enzyme molecule can catalyze thousands or more reactions per secondenzymes unaffected by the reactionAffected by cellular conditionsany condition that affects protein structuretemperature, pH, salinity
9If a patient in a hospital was accidentally given an IV full of pure water they would be fine because pure water is neutral so it can’t hurt us.
10Managing water balance Cell survival depends on balancing water uptake & lossfreshwaterbalancedsaltwater
11Aquaporins 1991 | 2003 Water moves rapidly into & out of cells evidence that there were water channelsprotein channels allowing flow of water across cell membranePeter AgreJohn HopkinsRoderick MacKinnonRockefeller
12Do you understand Osmosis… Cell (compared to beaker) hypertonic or hypotonicBeaker (compared to cell) hypertonic or hypotonicWhich way does the water flow? in or out of cell
13Cellular respiration is only done by heterotrophs because autotrophs can make their own energy.
14What does it mean to be a plant? Need to…collect light energytransform it into chemical energystore light energyin a stable form to be moved around the plant or storedneed to get building block atoms from the environmentC,H,O,N,P,K,S,Mgproduce all organic molecules needed for growthcarbohydrates, proteins, lipids, nucleic acidsATPglucoseCO2H2ONPK…
16The purpose of fermentation is to produce a small amount of energy when cells don’t have access to oxygen.
17Alcohol Fermentation pyruvate ethanol + CO2 Dead end process bacteria yeastrecycle NADH1C3C2Cpyruvate ethanol + CO2NADHNAD+back to glycolysisDead end processat ~12% ethanol, kills yeastcan’t reverse the reactionCount the carbons!
18Lactic Acid Fermentation animals some fungirecycle NADHO2pyruvate lactic acid3CNADHNAD+back to glycolysisReversible processonce O2 is available, lactate is converted back to pyruvate by the liverCount the carbons!
19Plants use water only as a means of keeping their cells full and holding the plant itself upright.
20ETC of PhotosynthesisChloroplasts transform light energy into chemical energy of ATPuse electron carrier NADPHTwo places where light comes in.Remember photosynthesis is endergonic -- the electron transport chain is driven by light energy.Need to look at that in more detail on next slidegenerates O2
21The second step of photosynthesis is called the dark reactions because it only happens in the dark.
22Light: absorption spectra Photosynthesis gets energy by absorbing wavelengths of lightchlorophyll aabsorbs best in red & blue wavelengths & least in greenaccessory pigments with different structures absorb light of different wavelengthschlorophyll b, carotenoids, xanthophyllsWhy are plants green?
23From Light reactions to Calvin cycle chloroplast stromaNeed products of light reactions to drive synthesis reactionsATPNADPHstromaATPthylakoid
24Diagram how a gamete with 3 chromosomes could be produced with two maternal chromosomes and one paternal chromosome. (there isn’t anything wrong in this statement)
30Proteins Most structurally & functionally diverse group Function: involved in almost everythingenzymes (pepsin, DNA polymerase)structure (keratin, collagen)carriers & transport (hemoglobin, aquaporin)cell communicationsignals (insulin & other hormones)receptorsdefense (antibodies)movement (actin & myosin)storage (bean seed proteins)Storage: beans (seed proteins)Movement: muscle fibersCell surface proteins: labels that ID cell as self vs. foreignAntibodies: recognize the labelsENZYMES!!!!
31Structural homologies only exist in animals, never in plants.
40Analogous structures Separate evolution of structures similar functionssimilar external formdifferent internal structure & developmentdifferent originno evolutionary relationshipDon’t be fooled by their looks!Solving a similar problem with a similar solution
41Convergent evolution Flight evolved in 3 separate animal groups analogous structuresDoes this mean they have a recent common ancestor?
42Convergent evolution Fish: aquatic vertebrates Dolphins: aquatic mammalssimilar adaptations to life in the seanot closely relatedThose fins & tails& sleek bodies are analogous structures!
43Bird and bat wings can only be described as homologous structures, not as analogous structures.
47The primitive atmosphere had to contain oxygen before life could evolve.
48Plants are simple organisms with no tissues or organs.
49Plant TISSUES Dermal Ground Vascular epidermis (“skin” of plant) single layer of tightly packed cells that covers & protects plantGroundbulk of plant tissuephotosynthetic mesophyll, storageVasculartransport system in shoots & rootsxylem & phloem
52Transport in plants H2O & minerals transport in xylem Transpiration Adhesion, cohesion & EvaporationSugarstransport in phloembulk flowGas exchangephotosynthesisCO2 in; O2 outstomatesrespirationO2 in; CO2 outroots exchange gases within air spaces in soilWhy does over-watering kill a plant?
53Ascent of xylem fluidTranspiration pull generated by leaf
55Pressure flow in phloem Mass flow hypothesis“source to sink” flowdirection of transport in phloem is dependent on plant’s needsphloem loadingactive transport of sucrose into phloemincreased sucrose concentration decreases H2O potentialwater flows in from xylem cellsincrease in pressure due to increase in H2O causes flowcan flow 1m/hrIn contrast to the unidirectional transport of xylem sap from roots to leaves, the direction that phloem sap travels is variable. However, sieve tubes always carry sugars from a sugar source to a sugar sink. A sugar source is a plant organ that is a net producer of sugar, by photosynthesis or by breakdown of starch. Mature leaves are the primary sugar sources. A sugar sink is an organ that is a net consumer or storer of sugar. Growing roots, buds, stems, and fruits are sugar sinks. A storage organ, such as a tuber or a bulb, may be a source or a sink, depending on the season. When stockpiling carbohydrates in the summer, it is a sugar sink. After breaking dormancy in the spring, it is a source as its starch is broken down to sugar, which is carried to the growing tips of the plant.A sugar sink usually receives sugar from the nearest sources. Upper leaves on a branch may send sugar to the growing shoot tip, whereas lower leaves export sugar to roots. A growing fruit may monopolize sugar sources around it. For each sieve tube, the direction of transport depends on the locations of the source and sink connected by that tube. Therefore, neighboring tubes may carry sap in opposite directions. Direction of flow may also vary by season or developmental stage of the plant.On a plant… What’s a source…What’s a sink?
56Transport of sugars in phloem Loading of sucrose into phloemflow through cells via plasmodesmataproton pumpscotransport of sucrose into cells down proton gradient
59Growth of the pollen tube and double fertilization If a pollen graingerminates, a pollen tubegrows down the styletoward the ovary.StigmaThe pollen tubedischarges two sperm intothe female gametophyte(embryo sac) within an ovule.One sperm fertilizesthe egg, forming the zygote.The other sperm combines withthe two polar nuclei of the embryosac’s large central cell, forminga triploid cell that develops intothe nutritive tissue calledendosperm.123PolarnucleiEggPollen grainPollen tube2 spermStyleOvaryOvule (containingfemaleGametophyte, orEmbryo sac)MicropyleOvulePolar nucleiTwo spermabout to bedischargedEndosperm nucleus (3n)(2 polar nuclei plus sperm)Zygote (2n)(egg plus sperm)
60Seed structure Seed coat Epicotyl Hypocotyl Radicle Cotyledons (a) Common garden bean, a eudicot with thick cotyledons. Thefleshy cotyledons store food absorbed from the endosperm beforethe seed germinates.(b) Castor bean, a eudicot with thin cotyledons. The narrow,membranous cotyledons (shown in edge and flat views) absorbfood from the endosperm when the seed germinates.(c) Maize, a monocot. Like all monocots, maize has only onecotyledon. Maize and other grasses have a large cotyledon called ascutellum. The rudimentary shoot is sheathed in a structure calledthe coleoptile, and the coleorhiza covers the young root.Seed coatRadicleEpicotylHypocotylCotyledonsEndospermScutellum(cotyledon)ColeoptileColeorhizaPericarp fusedwith seed coat
61Ectotherms do not regulate their body temperature in any way
63Most materials are transported through the blood stream of mammals and into and out of tissues by active transport.
64Arranged as a Phospholipid bilayer Serves as a cellular barrier / bordersugarH2Osaltpolarhydrophilicheadsnonpolarhydrophobictailsimpermeable to polar moleculespolarhydrophilicheadswastelipids
65Proteins domains anchor molecule Within membranenonpolar amino acidshydrophobicanchors protein into membraneOn outer surfaces of membrane in fluidpolar amino acidshydrophilicextend into extracellular fluid & into cytosolPolar areasof proteinNonpolar areas of protein
66Many Functions of Membrane Proteins “Channel”OutsidePlasmamembraneInsideTransporterEnzyme activityCell surface receptor“Antigen”Signal transduction - transmitting a signal from outside the cell to the cell nucleus, like receiving a hormone which triggers a receptor on the inside of the cell that then signals to the nucleus that a protein must be made.Cell surface identity markerCell adhesionAttachment to the cytoskeleton
67Membrane Proteins Proteins determine membrane’s specific functions cell membrane & organelle membranes each have unique collections of proteinsClasses of membrane proteins:peripheral proteinsloosely bound to surface of membraneex: cell surface identity marker (antigens)integral proteinspenetrate lipid bilayer, usually across whole membranetransmembrane proteinex: transport proteinschannels, pumps
68Membrane carbohydrates Play a key role in cell-cell recognitionability of a cell to distinguish one cell from anotherantigensimportant in organ & tissue developmentbasis for rejection of foreign cells by immune systemThe four human blood groups (A, B, AB, and O) differ in the external carbohydrates on red blood cells.
69In each of the following pairs the two terms given mean the same thing and do the same job. leukocyte; lymphocyteantigen; antibodyB lymphocyte; T lymphocytecytotoxic T cell; helper T cell
71Leukocytes: Phagocytic WBCs Attracted by chemical signals released by damaged cellsingest pathogensdigest in lysosomesNeutrophilsmost abundant WBC (~70%)~ 3 day lifespanMacrophages“big eater”, long-livedNatural Killer Cellsdestroy virus-infected cells & cancer cells
72Destroying cells gone bad! Natural Killer Cells perforate cellsrelease perforin proteininsert into membrane of target cellforms pore allowing fluid to flow in & out of cellcell ruptures (lysis)apoptosisvesiclenatural killer cellperforincell membraneperforin punctures cell membranecell membranevirus-infected cell
733rd line: Acquired (active) Immunity Specific defense with memorylymphocytesB cellsT cellsantibodiesimmunoglobulinsResponds to…antigenscellular name tagsspecific pathogensspecific toxinsabnormal body cells (cancer)B cell
74How are invaders recognized? Antigenscellular name tag proteins“self” antigensno response from WBCs“foreign” antigensresponse from WBCspathogens: viruses, bacteria, protozoa, parasitic worms, fungi, toxinsnon-pathogens: cancer cells, transplanted tissue, pollen“self”“foreign”
75Lymphocytes B cells T cells mature in bone marrow humoral response systemattack pathogens still circulating in blood & lymphproduce antibodiesT cellsmature in thymuscellular response systemattack invaded cells“Maturation”learn to distinguish “self” from “non-self” antigensif react to “self” antigens, cells are destroyed during maturationTens of millions of different T cells are produced, each one specializing in the recognition of oen particar antigen.
76Antibodies Proteins that bind to a specific antigen YYYYYYYYProteins that bind to a specific antigenmulti-chain proteinsbinding region matches molecular shape of antigenseach antibody is unique & specificmillions of antibodies respond to millions of foreign antigenstagging “handcuffs”“this is foreign…gotcha!”YYYYYYantigen- binding site on antibodyantigenYYYvariable binding regionYYeach B cell has ~50,000 antibodies
77Vaccinations Immune system exposed to harmless version of pathogen stimulates B cell system to produce antibodies to pathogen“active immunity”rapid response on future exposurecreates immunity without getting disease!Most successful against viruses
78Attack of the Killer T cells Destroys infected body cellsbinds to target cellsecretes perforin proteinpunctures cell membrane of infected cellapoptosisvesicleKiller T cellKiller T cell binds to infected cellcell membraneperforin punctures cell membranecell membraneinfected celldestroyedtarget cell
79Blood and filtrate move in the same direction through the nephrons of the kidney and this helps conserve energy.
80Osmotic control in nephron How is all this re-absorption achieved?tight osmotic control to reduce the energy cost of excretionuse diffusion instead of active transport wherever possibleDescending limb of the loop of Henle.Reabsorption of water continues as the filtrate moves into the descending limb of the loop of Henle.This transport epithelium is freely permeable to water but not very permeable to salt and other small solutes. For water to move out of the tubule by osmosis, the interstitial fluid bathing the tubule must be hyperosmotic to the filtrate.Because the osmolarity of the interstitial fluid does become progressively greater from the outer cortex to the inner medulla, the filtrate moving within the descending loop of Henle continues to loose water.Ascending limb of the loop of Henle.In contrast to the descending limb, the transport epithelium of the ascending limb is permeable to salt, not water.As filtrate ascends the thin segment of the ascending limb, NaCl diffuses out of the permeable tubule into the interstitial fluid, increasing the osmolarity of the medulla.The active transport of salt from the filtrate into the interstitial fluid continues in the thick segment of the ascending limb. By losing salt without giving up water, the filtrate becomes progressively more dilute as it moves up to the cortex in the ascending limb of the loop.the value of a counter currentexchange system
81why selective reabsorption & not selective filtration? Summarywhy selective reabsorption & not selective filtration?Not filtered outcells u proteinsremain in blood (too big)Reabsorbed: active transportNa+ u amino acidsCl– u glucoseReabsorbed: diffusionNa+ u Cl–H2OExcretedureaexcess H2O u excess solutes (glucose, salts)toxins, drugs, “unknowns”
82Neurons are at equilibrium at resting potential.
83Nervous system cells Neuron a nerve cell Structure fits function signaldirectiondendritescell bodyStructure fits functionmany entry points for signalone path outtransmits signalaxonsignal directionsynaptic terminalmyelin sheathdendrite cell body axonsynapse
84Cells have voltage!Opposite charges on opposite sides of cell membranemembrane is polarizednegative inside; positive outsidecharge gradientstored energy (like a battery)+This is an imbalanced condition.The positively + charged ions repel each other as do the negatively - charged ions. They “want” to flow down their electrical gradient and mix together evenly.This means that there is energy stored here, like a dammed up river.Voltage is a measurement of stored electrical energy. Like “Danger High Voltage” = lots of energy (lethal).––+
85How does a nerve impulse travel? Wave: nerve impulse travels down neuronchange in charge opens next Na+ gates down the line“voltage-gated” channelsNa+ ions continue to diffuse into cell“wave” moves down neuron = action potentialGate+–channel closedchannel openThe rest of the dominoes fall!–+Na+wave
87The nervous and endocrine systems send completely different kinds of messages so they never work together.
88Chemical synapse Events at synapse ion-gated channels open action potential depolarizes membraneopens Ca++ channelsneurotransmitter vesicles fuse with membranerelease neurotransmitter to synapse diffusionneurotransmitter binds with protein receptorion-gated channels openneurotransmitter degraded or reabsorbedaxon terminalaction potentialsynaptic vesiclessynapseCa++Calcium is a very important ion throughout your body. It will come up again and again involved in many processes.neurotransmitter acetylcholine (ACh)receptor proteinmuscle cell (fiber)We switched…from an electrical signalto a chemical signal
90All hormones have the same types of effects on cells, no matter what they are made of.
91Relay molecules in a signal transduction EXTRACELLULARFLUIDCYTOPLASMPlasma membraneReceptionTransductionResponseReceptorActivationof cellularresponseRelay molecules in a signal transductionpathwaySignalmolecule
92LE 11-6 Hormone EXTRACELLULAR (testosterone) FLUID The steroid hormone testosteronepasses through theplasma membrane.PlasmamembraneTestosterone bindsto a receptor proteinin the cytoplasm,activating it.ReceptorproteinHormone-receptorcomplexThe hormone-receptor complexenters the nucleusand binds to specificgenes.DNAmRNAThe bound proteinstimulates thetranscription ofthe gene into mRNA.NUCLEUSNew proteinThe mRNA istranslated into aspecific protein.CYTOPLASM
93LE 11-7b Signal molecule Signal-binding site a Helix in the membrane TyrosinesTyrTyrTyrTyrTyrTyrTyrTyrTyrTyrTyrTyrTyrTyrTyrTyrTyrTyrReceptor tyrosinekinase proteins(inactive monomers)DimerCYTOPLASMActivated relayproteinsCellularresponse 1TyrTyrPTyrPTyrPTyrTyrPTyrTyrPTyrTyrPPPTyrTyrTyrTyrPTyrTyrPPTyrTyrPCellularresponse 26ATP6 ADPActivated tyrosine-kinase regions(unphosphorylateddimer)Fully activated receptortyrosine-kinase(phosphorylateddimer)Inactiverelay proteins
94LE 11-10First messenger(signal moleculesuch as epinephrine)AdenylylcyclaseG proteinG-protein-linkedreceptorGTPATPSecondmessengercAMPProteinkinase ACellular responses
95LE 11-8 Signal molecule Receptor Activated relay molecule Inactive protein kinase1Activeproteinkinase1Inactiveprotein kinase2ATPADPActiveproteinkinase2PPhosphorylation cascadePPPiInactiveprotein kinase3ATPADPActiveproteinkinase3PPPPiInactiveproteinATPADPPActiveproteinCellularresponsePPPi
96All populations will increase continuously, regardless of outside factors.
97Survivorship curves Generalized strategies What do these graphs tell about survival & strategy of a species?Generalized strategies251000100Human(type I)Hydra(type II)Oyster(type III)10150Percent of maximum life span75Survival per thousandI. High death rate in post-reproductive yearsII. Constant mortality rate throughout life spanA Type I curve is flat at the start, reflecting low death rates during early and middle life, then drops steeply as death rates increase among older age groups. Humans and many other large mammals that produce few offspring but provide them with good care often exhibit this kind of curve. In contrast, a Type III curve drops sharply at the start, reflecting very high death rates for the young, but then flattens out as death rates decline for those few individuals that have survived to a certain critical age. This type of curve is usually associated with organisms that produce very large numbers of offspring but provide little or no care, such as long–lived plants, many fishes, and marine invertebrates. An oyster, for example, may release millions of eggs, but most offspring die as larvae from predation or other causes. Those few that survive long enough to attach to a suitable substrate and begin growing a hard shell will probably survive for a relatively long time. Type II curves are intermediate, with a constant death rate over the organism’s life span. This kind of survivorship occurs in Belding’s ground squirrels and some other rodents, various invertebrates, some lizards, and some annual plants.III. Very high early mortality but the few survivors then live long (stay reproductive)
98Reproductive strategies K-selectedlate reproductionfew offspringinvest a lot in raising offspringprimatescoconutr-selectedearly reproductionmany offspringlittle parental careinsectsmany plantsK-selectedr-selected
99Logistic rate of growth Can populations continue to grow exponentially?Of course not!no natural controlsK = carrying capacityDecrease rate of growth as N reaches Keffect of natural controlsWhat happens as N approaches K?
100Population growth predicted by the logistic model dNdt1.0NExponential growthLogistic growth1,500 N1,500K 1,500510155001,0002,000Number of generationsPopulation size (N)