Packet 6Cellular Energy
ATP: cellular energy
Why do cells need energy?Cells carry out three kinds of energy-requiring work:ChemicalMechanicalTransport
Making ATP: Aerobic cellular respiration
Glycolysis (Stage 1) Breaking down glucose glyco lysis (splitting sugar)
Occurs in the cytoplasmA little ATP energy is harvested, but its inefficient generate only 2 ATP for every 1 glucose
Overview10 reactionsconvert glucose (6C) to 2 pyruvate (3C) produces: 4 ATP & 2 NADHconsumes: 2 ATPnet yield: 2 ATP & 2 NADHSubstrate-level phosphorylationSubstrate-level phosphorylation
Products of glycolysis move on to stage 2 or 3
Mitochondria StructureDouble membranesmooth outer membranehighly folded inner membraneintermembrane spaceMatrixDNA, ribosomesenzymes
This happens twice for each glucose molecule that started glycolysiswhy?Stage 2: Pyruvate grooming and the Krebs Cycle
Electron Transport Chain and Chemiosmosis: ATP payoff!Electron Transport Chain series of proteins built into inner mitochondrial membrane
GlycolysisKrebs cycle8 NADH2 FADH2Remember the Electron Carriers? 2 NADHTime to break open the piggybank!
Electron Transport ChainWhat powers the proton (H+) pumps?Electronegativity!
Chemiosmosis and oxidative phosphorylationoxidative phosphorylation
Cellular respiration2 ATP2 ATP34 ATP++~38 ATP
Summary of cellular respirationWhere did the glucose come from?Where did the O2 come from?Where did the CO2 come from?Where did the CO2 go?Where did the H2O come from?Where did the ATP come from?What is recycled for use again?Why do we breathe?
ETC backs upnothing to pull electrons down chainNADH & FADH2 cant unload HATP production ceasescells run out of energyTaking it beyondWhat is the final electron acceptor in Electron Transport Chain?O2So what happens if O2 unavailable?
Anaerobic respirationMaking ATP without oxygen
All cells carry out glycolysis: prokaryotes and eukaryotes.Eukaryotes and many prokaryotes also carry out oxidative phosphorylation (remember this requires oxygen).
How can some bacteria carry out aerobic respiration if they don't have mitochondria?FUN FACT: many bacteria have ETCs in their cell membranes.
Reminders!A net of 2 ATP is generated in glycolysis.
NAD+ must be present available for this process.
New considerationsFor aerobic organisms this is not a problem, NAD+ is regenerated by the ETC.
Not all organisms can use oxygen, they are anaerobic
Anaerobic organisms use glycolysis only to make ATP
They regenerate , NAD+ through fermentation processes
Lactic acid fermentation
Review: Answer all of the following questions in your notebook.What are the products of pyruvate grooming for 1 molecule of glucose?What are the products of the citric acid cycle for 1 molecule of glucose?After glycolysis, pyruvate grooming, and the citric acid cycle, what are your net products?What is phosphorylation?What is substrate-level phosphorylation?What is the main goal for stages 1-3?
Review: Answer all of the following questions in your notebookWhat is the summary equation for cellular respiration?If oxidation is a loss of electrons (in the form of hydrogen atoms) and reduction is the gain of electrons (in the form of hydrogen atoms), what is oxidized during cellular respiration? what is reduced during cellular respiration?How does glucose get to your cells for cellular respiration?What is the point of cellular respiration?What are the net molecular products of glycolysis?
Where does glucose come from for cellular respiration?Photosynthesis!
Leaf structureMesophyll cellsVascular tissueStomateGuard cells
Chloroplast structureDouble membraneStromaThylakoidGrana
Stage 1:Light-dependent reactionsStage 2:Calvin cycleLight energy is converted to chemical energy (as NADPH and ATP).Glucose is made from CO2 and hydrogens carried by NADPH using ATP energy.
What factors might affect the rate of photosynthetic reactions?SUMMARY
Examples of work:Chemical work: dehydration synthesis reactionsMechanical: muscle contractionTransport: shuttling molecules across the membrane with transport proteins (active transport)***1st ATP used is like a match to light a fire initiation energy / activation energy.
Destabilizes glucose enough to split it in two*intermembrane spacefluid-filled space between membranesmatrixinner fluid-filled spaceenzymesfree in matrix & membrane-bound
*A 2 carbon sugar went into the Krebs cycle and was taken apart completely. Two CO2 molecules were produced from that 2 carbon sugar. Glucose has now been fully oxidized!
But wheres all the ATP??? ****NADH NAD+ + HH e- + H+
Ideally, each NADH yields 3 ATP; each FADH2 yields 2 ATP***Where did the glucose come from?from food eatenWhere did the O2 come from?breathed inWhere did the CO2 come from?oxidized carbons cleaved off of the sugars (grooming & Krebs Cycle)Where did the CO2 go?exhaledWhere did the H2O come from?from O2 after it accepts electrons in ETCWhere did the ATP come from?mostly from ETCWhat else is produced that is not listed in this equation?NAD, FAD, heat!*What if you have a chemical that punches holes in the inner mitochondrial membrane?***
Fermentation is the pathway that some prokaryotes always have to take (obligate anaerobes). This pathway is also used by prokaryotes and yeasts that are facultative anaerobes.
Fermentation is also used by your own muscles when you are working out strenuously and gas exchange is not happening fast enough to replenish ATP through oxidative phosphorylation.
*Bacteria and yeastNADH is recycled back to NAD+ when pyruvate is converted to ethanol. Alcohol is released into the organism's environment as waste.Fun fact: Bubbles in beer and champagne are CO2 released in the conversion of pyruvate to alcohol.*Animals, fungiNADH is recycled back to NAD+ when pyruvate is converted to lactate (enzyme-catalyzed)Once O2 is available, lactate is converted back to pyruvate by the liverCells can then resume aerobic respiration using pyruvate (starts Stage 2).
Mesophyll cells: Photosynthesis is a net endergonic reaction because there is more energy in the bonds of glucose than there are in the bonds of the reactants.***1. A five-carbon sugar molecule called ribulose bisphosphate, or RuBP, is the acceptor that binds CO2 dissolved in the stroma. This process, called CO2 fixation, is catalyzed by the enzyme RuBP carboxylase, forming an unstable six-carbon molecule. This molecule quickly breaks down to give two molecules of the three-carbon 3-phosphoglycerate (3PG), also called phosphoglyceric acid (PGA).
2. The two 3PG molecules are converted into glyceraldehyde 3-phosphate (G3P, a.k.a. phosphoglyceraldehyde, PGAL) molecules, a three-carbon sugar phosphate, by adding a high-energy phosphate group from ATP, then breaking the phosphate bond and adding hydrogen from NADH + H+.
3. Three turns of the cycle, using three molecules of CO2, produces six molecules of G3P. However, only one of the six molecules exits the cycle as an output, while the remaining five enter a complex process that regenerates more RuBP to continue the cycle. Two molecules of G3P, produced by a total of six turns of the cycle, combine to form one molecule of glucose.