2Cell EnergyEnergy is essential to life Plants trap light energy in sunlight and store it in the bonds of certain molecules to use later Other organisms get energy from eating those green plants What processes can you name that require energy?
3Adenosine Triphosphate (ATP) An energy molecule in the cell that allows for quick and easy access to energy when needed by the cell’s organelles.A type of chemical energyReleases energy when the chemical bonds are brokenA-P-P-P
4Forming ATP Phosphate groups are negatively charged Negative doesn’t like being next to negativeA small amount of energy is required to attach one phosphate group to adenosine (AMP)When a second phosphate group is added, this requires a lot more energy (ADP)When a third phosphate group is added, this requires an even greater amount of energy (ATP)The process of forming ATP requires much energy
5Breaking down ATPEnergy of ATP becomes available to a cell when the molecule is broken downWhen a cell requires energy, ATP goes to the cell, attaches to the binding site, and a phosphate group is broken off – this gives off energy for the cell and the ATP molecule becomes ADP (fig. 9.2 pg. 223)In order for ADP to become ATP again it goes to the mitochondria and gets recharged (another phosphate group gets attached)
6Uses of cell energy Energy is VERY important on the cellular level Making new moleculesBuilding membranes and cell organellesCells use energy to maintain homeostasisKidneys use energy to move molecules and ions in order to eliminate waste substances while keeping needed substances in the bloodstream.
7Photosynthesis In this section… What is photosynthesis? Where photosynthesis happensColor: How it worksThe two phases of photosynthesis
8PhotosynthesisA process of taking light energy and converting it into chemical energyThis energy is stored as carbohydrates in plantsHappens in two phases:Light-dependent reactions- converts light energy into chemical energy-molecules of ATP produced fuel light-independent reactionsLight-independent reactions- produce glucose
9Where does photosynthesis occur? In chloroplasts there are thylakoid disks/granaLight-dependent reactions happen in the thylakoid membranes
10PigmentsTo trap the energy in the sunlight, the thylakoid membranes contain pigments.Pigments are molecules that absorb specific wavelengths of sunlightChlorophyll is the most common type of pigment in chloroplasts
11Why we see colorWe see colors that are reflected and not absorbed. Green pigments absorb all light except green (chlorophyll)In the fall, trees stop producing chlorophyll, which results in the different colors seen.
12The Big PictureEnergy Light-Dependent Reactions Light-Independent Reactions (Calvin Cycle) Stored Energy (stored as glucose)
13Light-Dependent Reactions First phase of photosynthesis requires sunlight.A light-dependent reaction involves sunlight striking molecules of chlorophyll and exciting an electron.Excited electrons are passed from chlorophyll to an electron transport chainElectron transport chain- a series of proteins embedded in the thylakoid membrane
14Light-dependent reactions Once in the electron transport chain, each protein in the chain passes the energized electrons along to the next protein-some energy is lost during each pass-lost energy can be used to form ATP from ADP OR to pump hydrogen ions into the center of the thylakoid disc.After electrons have traveled down the electron transport chain, they are re-energized in a second photosystem and passed down a second electron transport chain- electrons are still very energized
15Light-Dependent reactions Electrons are then transferred to the stroma of the chloroplastTransferred by an electron carrier molecule called NADP+ (nicotinamide adenine dinucleotide phosphate)NADP+ can combine with two excited electrons and a hydrogen ion (H+) to become NADPH.NADPH stores the energy until it can transfer it to the stroma- this is where NADPH will play an important role in the light-independent reaction.
16Restoring ElectronsThe chlorophyll needs to replace the electrons that were lost at the beginning of photosynthesis in order to absorb additional light to keep the process going.To replace lost electrons, the molecules of water are split in the first photostem- reaction called photolysisFor every water molecule that is split, 1 Oxygen, 2 electrons, and 2 Hydrogen ions are formedOxygen produced by photolysis is released into the air-supplies oxygen for air we breatheElectrons are returned to the chlorophyllH+ ions are pumped into the thylakoid-> they accumulate in high concentrations which causes a concentration gradient- H+ ions diffuse out of thylakoid and provide energy for production of ATP (called chemiosmosis)
17Light-Independent reactions 2nd phase of photosynthesisDoes NOT require lightTakes place in the stroma of the chloroplastAka Calvin cycle- called a cycle bc one of the products is needed to start the cycle overFollow the cycle on pg. 229
18The Calvin Cycle1) CARBON FIXATION-The carbon atom from CO2 bonds with a five-carbon sugar called ribulose biphosphate (RuBP) to form an unstable six carbon sugar.2) FORMATION OF 3-CARBON MOLECULES-The six-carbon sugar immediately splits to form two three-carbon molecules.3) USE OF ATP AND NADPH-A series of reactions involving ATP and NADPH from the light-dependent reactions converts the three-carbon molecules into phosphoglyceraldehyde (PGAL), three-carbon sugars with higher energy bonds.4) SUGAR PRODUCTION- One out of every six molecules of PGAL is transferred to the cytoplasm and used in the synthesis of sugars and other carbohydrates. After three rounds of the cycle, six molecules of PGAL are produced.5) RuBP IS REPLENISHED- Five molecules of PGAL, each with three carbon atoms, produce three molecules of the five-carbon RuBP. This replenishes the RuBP that was used up, and the cycle can continue.
19Getting Energy to Make ATP Cellular Respiration- The process by which mitochondria break down food molecules to produce ATP.There are 3 stages of cellular respiration1) Glycolysis- anaerobic (no oxygen required)2) Citric acid cycle- aerobic (oxygen required)3) Electron transport chain- aerobic (oxygen required)
21Glycolysisa series of reactions in the cytoplasm of a cell in which glucose (a 6 carbon molecule) is broken down into two molecules of pyruvic acid (3 carbon molecules).ATP - it takes 2 molecules of ATP to start the process of glycolysis, and only 4 ATPs are made, therefore this process is not very energy efficient.
22Glycolysis*only 2 molecules of ATP are produced from the breakdown of one glucose molecule.NAD+ (nicotinamide dinucleotide) - just as photosynthesis has the energy carrier NADP+; glycolysis has an energy carrier called NAD+.*NAD+ forms NADH when carrying an electron.At the end of glycolysis the pyruvic acid molecules produced move to the mitochondria,the powerhouses or ATP producers of the cell.
25Post-GlycolysisPost-glycolysis reactions - before the pyruvic acid molecules can enter the citric acid cycle (the next stage of cellular respiration) some modifications need to be done.pyruvic acid loses a molecule of CO2 and combines with Coenzyme A to form a molecule of Acetyl-CoA.the rxn w/ Coenzyme A makes a molecule of NADH+ H+
26The Citric Acid CycleThe Citric Acid Cycle: “The breakdown of Glucose”-a series of chemical reactions similar to the Calvin Cycle, but opposite in purpose.Calvin Cycle - forms glucose in photosynthesisCitric Acid Cycle - breaks down glucose in cellular respirationMaterials needed :to break down glucose, two electron carriers areneeded:a) NAD+b) FAD (flavin adenine dinucleotide)
27The Citric Acid cycleThe Citric Acid Cycle (CAC) produces a number of molecules:a) 1 ATP is producedb) 3 NADH + H+ are producedc) 1 FADH2 molecule is produced
28Steps of the Citric Acid Cycle 1) formation of citric acid - a 2 carbon acetyl CoA combines with a 4 carbon compound called oxaloacetic acid, forming a 6 carbon molecule called citric acid.2) formation of CO2 - one molecule of CO2 is formed from the citric acid cycle which reduces the citric acid molecule to a 5 carbon molecule called ketoglutaric acid.*from this rxn, one molecule of NADH +H+ is made from one NAD+3) formation of second CO2 - another molecule of CO2 is formed and released from the ketoglutaric acid; this results in a 4 carbon compound called succinic acid. *from this rxn, one molecule of ATP and one molecule of NADH + H+ are formed.4) recycling of oxaloacetic acid - succinic acid undergoes a series of rxns which form FADH and NADH + H+ and oxaloacetic acid; this is then available for the next cycle to occur.Succinic -> fumaric -> malic -> oxaloacetic
31Electron Transport Chain Function - move energized molecules; NADH & FADH2 pass energized molecules from protein to protein releasing small amounts of energy with each pass.Location - the inner membrane of the mitochondria
33Electron Transport Chain The Process:a) NADH & FADH2 pass energized molecules from protein to protein; small amounts of energy are released with each pass.b) some energy is used to form ATP, while some is used to pump H+ ions into the center of the mitochondria.c) as H+ ions are pumped into the center of the mitochondria, the center becomes more (+),while the outside becomes more (-). Since the outside is more (-) it will attract more (+)’s or more H+ ions,creating an electrochemical gradient.d) The electrochemical gradient drives the inner membrane of the mitochondria to form ATP.e) The final electron acceptor in the ETC is Oxygen. The oxygen reacts with H+ ions to form water molecules.
35ETC Importance The importance of Oxygen (O2) If oxygen is not available for the ETC, then the chain cannot pass along energized electrons; if electrons cannot be passed, then there is no room to accept more electrons and a blockage results. Therefore, cellular respiration cannot occur.Overall productionThe ETC results in the production of 32 ATP moleculesThis is the most efficient means for production of ATPThink: Aerobic (jogging) vs, Anaerobic (sprinting) - which can be done longer?
36Fermentationsometimes your cells may be deprived of oxygen for a short timefermentation can occur during extremely strenuous activitiesFermentation - anaerobic process that occurs when your cells are w/o O2 for a short time. It occurs after glycolysis and provides a way to continue producing ATP until oxygen is available again.2 main types of fermentation:a) lactic acid fermentationb) alcoholic fermentation
37Lactic Acid Fermentation *occurs during anaerobic conditions when oxygen is not available as the final electron acceptor in the ETC, therefore a “back-up” occurs.What happens:a) as NADH and FADH2 try to pass theirenergized electrons onto the next protein in theETC, they are rejected.b) if NADH and FADH2 cannot pass on theirenergized electrons, then NADH and FADH2cannot be converted back to NAD+ & FAD, whichare needed to keep the CAC and glycolysisgoing.
38Alcoholic Fermentation *often used by yeast cells to produce CO2 and ethyl alcohol.*anaerobic process - used to make bread dough “rise” and brew alcohols.
39Comparing Photosynthesis and Cellular Respiration Both use an ETC to form ATPDo opposite jobsPhotosynthesis - produces high energy carbohydrates and O2 from the sun’s energyCellular respiration - uses O2 to break down carbohydrates with much lower energy level
40Photosynthesis Cellular Respiration Comparisons: Food is made or accumulatedFood is Broken downEnergy from sun is stored as glucoseEnergy from glucose is released to be used by bodyCarbon dioxide (CO2) is taken inCO2 is given off as a waste productOxygen (O2) is given off as wasteOxygen is needed and is taken inProduces glucose from PGALProduces CO2 and H2O as wasteCan happen only when some light is availableCan occur all day and all nightRequires Chlorophyll, can only happen in plantsOccurs in all living cells - plants and animals