Chapter 9 Lecture Notes

Transcription

1 Bilgy Chapter 9 Lecture Ntes Name Per Quiz #11 Yu will be able t describe the structure and functin f ATP Yu will be able t identify the inputs and utputs f each prcess f respiratin and phtsynthesis. Yu will be able t identify the imprtant steps f each prcess. Yu will be able t lcate when and where each prcess ccurs in the cell. Laws f Thermdynamics The three main laws f thermdynamics are three f the mst imprtant statements in science. They must be fllwed anytime yu are dealing with energy transfers. 1) Energy cannt be created r destryed. Energy can nly change frms 2) Systems f energy tend t mve twards randmness 3) Energy never stps flwing frm ne place t anther The Need fr Energy Strage Every actin by every rganism n the planet is nly pssible thanks t different energy frms. Casual energy (basic life tasks) Rts absrbing water, breathing Immediate energy (sudden bursts) Flwers blming; walking Lng term energy (savings accunt) Fruits, vegetables and nuts; Fat strage Emergency energy (h lk! A tiger ) Flytraps; Epinephrine (Adrenaline) ATP Sketch Area We have lts f different frms f energy in ur wrld. Cal, il, slar, wind, water, ethanl Our energy surces are the fd we cnsume. These are gd energy surces, but we can t use them as energy until we cnvert them int a useful surce. I dn t pwer up my cell phne with water; I pwer it up with electricity prduced by the energy f water mving thrugh a dam. Befre ur bdies can use the energy frm fd, we have t turn fd, liquids and gasses int a usable pwer surce called an ATP mlecule

2 ATP is a sugar mlecule hlding tgether three mlecules f phsphates. ATP can be used in ur bdy bth as a unit f pwer (just like electricity) and as a unit f energy strage (just like a battery). Phsphates d nt easily bnd t each ther, like tw psitive ends f magnets trying t repel. The nly way t hld the phsphates tgether is with high amunts f energy Therefre as lng as the 3 phsphates are attached t each ther, the ATP is hlding large amunts f energy It can carry this energy anywhere in the cell ATP as a battery Hw des the cell plug in ATP t use its energy? ATP is highly unstable. It wants t break ff ne f its phsphate mlecules. All enzymes have a special site that is shaped t fit a phsphate mlecule. ATP will release its phsphate int an enzyme, effectively plugging in the battery. Nw, nce the enzyme finds it s substrate, it has enugh pwer t perfrm its functin ATP, after having given up a phsphate, is nw ADP (Adensine Diphsphate) Hw the cell recharges ATP batteries ATP is s unstable, it nly exists fr micrsecnds. Every cell in every rganism needs t cnstantly be pwering up new ATP mlecules t replace the used nes. In this chapter we will talk abut respiratin, fermentatin, and phtsynthesis. Each f these are prcesses that plants, animals, fungi and bacteria use t recharge their ADP mlecules int ATP Essentially, these prcesses are the pwer plants f cells. Cell Respiratin Cell respiratin is the primary prcess f energy prductin fr animals, and a secndary prcess fr plants. Respiratin cnsists f three stages. Each stage requires different inputs and utputs and run under different circumstances. The equatin fr cell respiratin is 6 O2 + C6H12O6 6 CO2 + 6 H2O + energy *Nte: Glucse is a 6-carbn mlecule* Chemical Energy and Fd Ntice that ne f the inputs fr cellular respiratin is a glucse mlecule. One gram f glucse releases 3811 calries f heat energy Because a calrie is s small, fd labels, wrkut machines, etc, all measure calries as a kilcalrie (1000 calries) and label it with a capital C. What we dn t want t d is burn all f thse calries at nce. We want t break the glucse int pieces and use nly a little at a time.

3 Glyclysis Glyclysis is the first step f cell respiratin. It ccurs in the cytplasm. Glyclysis is ten steps lng. It begins with a mlecule f glucse. Here are the imprtant steps: Step 1 and Step 3 require ATP t be used. (As is typical in life, yu have t spend sme nw in rder t earn mre later) *Step 4 and 5 split the glucse int tw 3-carbn mlecules called PGAL Frm nw n, each step f cell resp. will happen twice, ne fr each mlecule f PGAL prduced. In step 6, a mlecule f NAD + becmes NADH. This will be used later. In steps 7 and 10 each, ne ADP becmes an ATP. At the end f glyclysis, the cell has built tw mlecules f pyruvic acid. These tw mlecules can nw enter ne f three different stages f energy prductin. Inputs f glyclysis: 1 glucse, 2 ATP Outputs f glyclysis: 2 pyruvic acids, 4 ATP, 2 NADH Net Gain: 2 Pyruvic Acids, 2 ATP, 2 NADH The Next Step Glyclysis is cnstantly ccurring in the cell. Where the pyruvic acids g next depends n yur situatin and envirnment. 1 st, is there any xygen present? 2 nd, why d yu need the energy? Are yu exercising? Fatigued? In danger? If xygen is present, yur cell will g thrugh aerbic respiratin (Citric Acid Cycle and Electrn Transprt Chain) If xygen is nt present, yur cell will g thrugh anaerbic respiratin (Fermentatin) Intermediate Step (Aerbic Respiratin) Befre the pyruvic acids enter the Citric Acid cycle, they have t d what is called the intermediate step The pyruvic acid enters the mitchndria The 3-carbn pyruvic acids give ff a CO2 mlecule and becme a 2-carbn mlecule called acetyl-ca. Als, anther mlecule f NADH is frmed Nw, the acetyl-ca can enter the Citric Acid Cycle Citric Acid Cycle (Krebs Cycle) The citric acid cycle takes place in the mitchndria. The cycle is six steps lng. It begins with ne mlecule f acetyl-ca. There is ne cmplete cycle fr every mlecule f acetyl-ca, but tw fr every mlecule f glucse. The first step f the cycle is when a mlecule f acetyl-ca (a 2-carbn mlecule) bnds with a mlecule f citric acid (a 4-carbn mlecule) t frm a 6-carbn mlecule

4 During ne cycle, 2 carbns are remved t prduce CO2 and the riginal mlecule becmes a 4-carbn citric acid again. During ne cycle, the cell als prduces ne mlecule f ATP, 3 mlecules f NADH, and ne mlecule f FADH 2 Net gain fr ne mlecule f acetyl-ca (fr every glucse): 1 ATP, 3 NADH, 1 FADH2, 2 CO2 Electrn Transprt Chain The electrn transprt chain fllws glyclysis and the citric acid cycle. The ETC takes place in the inner membrane f the mitchndria. Yu have seen that during the first tw stages we have prduced many mlecules f NADH and FADH 2. They will be used here in the ETC. The ETC is pwered thanks t the cncept f diffusin and equilibrium The ETC is a series f prtein channels embedded in the inner mitchndrial membrane. NADH and FADH 2 are like ATP because they are pwer surces (think, miniature batteries). The NADH and FADH2 give ff an electrn which pwers each prtein channel in sequence. The functin f these prteins is t mve hydrgen atms frm inside the membrane t utside the membrane. This creates an unequal rati f hydrgen atms alng the membrane. The membrane is NOT in equilibrium ATP Synthase The nly way fr the hydrgen atms t get back acrss the membrane is thrugh a special prtein channel enzyme called ATP synthase. ATP synthase lks like an upside-dwn light bulb. As the hydrgen atms pass thrugh the ATP synthase, they prvide pwer t the enzyme. When the enzyme has pwer, it attaches phsphates t ADP mlecules in the bulb part and prduces an ATP mlecule. ATP Prductin Each mlecule f NADH pwers the ETC enugh t build 3 mlecules f ATP FADH gives a little less pwer and can build nly 2 ATP This means the ETC can prduce a ttal f 32 ATP per glucse mlecule. Add that t the fur ATP already prduced, yu have a maximum-pssible net gain f ATP mlecules frm 1 mlecule f glucse. T remve the electrn frm the ETC, the cell bnds it with a mlecule f xygen. This is why yu need t breathe. This is what the xygen is used fr. Fermentatin If n xygen is present (hlding yur breath, underwater, asthma, etc) the pyruvic acid will nt g thrugh the citric acid cycle. Yu can nly get energy thrugh glyclysis. Fr glyclysis t start again, yu need the NADH t becme NAD+ again. This happens in fermentatin. There are tw types f fermentatins Alchlic fermentatin: The NADH becmes NAD+, with alchl as a waste prduct

5 Pyruvic acid + NADH Alchl + CO2 + NAD + Lactic Acid fermentatin: energy in the frm f lactic acid is prduced by the muscle. Pyruvic acid + NADH Lactic Acid + NAD + Muscles have enugh ATP readily available fr a few secnds f intense exercise. After that, if the exercise is anaerbic (sprinting, swimming, lifting weights), ATP is prduced via lactic acid fermentatin. The average human being can nly handle this fr apprximately 90 secnds. Then they need xygen. Lactic acid is helpful fr a few secnds, but harmful lng term. Oxygen is required t remve the lactic acid and relieve the sreness felt in yur muscles This is why yu breath deep after intense exercise Fr exercise lnger than 90 secnds, the bdy frces the rganism t take in xygen. This allws the cells t enter aerbic respiratin. Phtsynthesis What is the main surce f energy fr all life? The sun! Plants need t be able t capture light and transfrm it int a usable energy surce. The prcess f using energy frm the sun t make sugars fr energy strage r usable energy is called phtsynthesis. The equatin fr phtsynthesis is Energy + 6 CO H 2 0 C 6 H 12 O O 2 Nte: this is the exact ppsite f the cell respiratin equatin Phtsynthesis is tw parts: Light-dependent and Light-Independent Reactins Chlrplasts and Pigments Phtsynthesis takes place in the chlrplast f plant cells. Chlrplasts cntain stacks f disks called thylakids. Each thylakid cntains different types f pigments. Pigments are the chemicals that run phtsynthesis. The mst cmmn type f pigment is chlrphyll. Chlrphyll absrbs all wavelengths f sunlight except fr the clr green, which it reflects. This is why plant leaves and stems are mst ften clred green. Light-Dependent Reactins When sunlight strikes the pigments in the plant cells, it energizes these pigments (think, slar panels) The pigments are then able t take this energy and add an electrn t an NADP + mlecule int an NADPH. The surce f the electrn is H2O The NADPH ges thrugh the plants electrn transprt chain, creating ATP mlecules. **Nt much ATP is prduced. But it s all frm the sun s energy s, fr the plant, it s all free**

6 Light-Independent Reactins What d plants d with this energy? And hw d they survive during winter, r when the sun isn t shining, r when their leaves have fallen? Plant cells g thrugh a prcess called the Calvin cycle. The Calvin cycle uses energy frm ATP built in the light reactins t prduce sugars fr respiratin. Plant cells underg bth phtsynthesis AND respiratin; animal cells nly underg respiratin. The Calvin cycle takes place in the strma (the space inside the chlrplast in between the thylakids) The first step f the Calvin cycle is called carbn-fixatin, because three mlecules f CO 2 are attached t three 5-carbn mlecule called RuBP (Ribulse Bisphsphate) Thrughut the next series f steps, the 6-carbn mlecule is rearranged int tw 3-carbn mlecules. One f these 3-carbn mlecules leave the chlrplast and are used t build sugars. Other 3-carbn mlecules are recmbined t build new RuBP mlecules s that the cycle can begin again. The Calvin Cycle requires 2 ATP and 1 NADPH fr pwer. But it gets this pwer frm the sun. Phtsynthesis Summary In the Light Reactins H2O and Sunlight are required (free energy) ATP and NADPH are prduced In the Calvin Cycle CO2 is required The ATP and NADPH frm the light reactins are needed Glucse (and ther sugars like starch, maltse, cellulse, etc) are prduced The inputs f energy cme entirely frm the sun. The benefits f that energy g entirely t the plant! Cell Respiratin Sugars are brken dwn Glucse is main surce f energy CO 2 given ff Oxygen taken in Prduces water Des nt require light Occurs in all living cells Phtsynthesis Sugars are built Sun is main surce f energy CO2 taken in Oxygen given ff Requires water Requires light Occurs nly in presence f pigments