Cellular Energy Photosynthesis and Respiration

Cellular EnergyPhotosynthesis and Respiration Jack Terrain Kelley Kuhn

Photosynthesis song • https://www.youtube.com/watch?v=C1_uez5WX1o • http://www.watchknowlearn.org/Video.aspx?VideoID=4026&CategoryID=6172

Homework for this unit: • 8.1: 1-4 • 8.2: 1-5 • 8.3: 1-5 • Pp 237-239: 6-9, 18-21, 33-37 (M/C) • Due 11/21 or 22 or 11/28 or 29—your choice…in other words, you can turn it in the class that meets before Thanksgiving or the first class that meets after.

Root beer fermentation lab • We are kicking off this unit with a lab where we will make root beer. We need you to bring in Spring Water. If you bring in a gallon of spring water, you can get 10 points bonus on this lab (which many of you need based on the last quiz!). We need this water by Monday/Tuesday November 14/15. If we do not get enough water, we will not be able to make root beer. 

Memorize this! Photosynthesis: 6 CO2 + 6 H2O + light energy  C6H12O6 + 6 O2 Respiration: C6H12O6 + 6 O2  6 CO2 + 6 H2O + ATP cellular energy

Photosynthesis • Occurs in the chloroplasts of plants • Has two main parts: • Light Reaction (aka Light Dependent Reaction) • Calvin Cycle (aka Dark reaction, Light Independent reaction)

Light Reaction Light reaction vital stats: 1. Occurs on the thylakoid membranes in the grana of the chloroplast 2. Requires light and water 3. Generates ATP and NADPH which will be used in the Calvin Cycle 4. Gives off oxygen gas and hydrogen ions as waste products

Light Reaction Details Step 1: Photosystem II (P680) is positively charged and it pulls an electron off water giving off oxygen and hydrogen ion (H2O  1/2O2 + 2H+) When its chlorophyl molecule absorbs light, it boosts the electron to a higher energy level, Step 2: This energized electron runs down an electron transport chain (a series of proteins embedded in the thylakoid membrane) and its energy is used to make an ATP by creates a proton motive force that moves H+ ions into the thylakoid space. These H+ ions then spins through a membrane protein called ATP synthase, generating ATP as the ions move out of the thylakoid space.

Step 3: . Now at a lower energy state, the electron reaches Photosystem I (P700).At this photosystem, more light energy is absorbed and the electrons is re-energized. It travels along a second electron transport chain and is added to NADP+ to make NADPH. http://www.science.smith.edu/departments/Biology/Bio231/ltrxn.html http://www.uic.edu/classes/bios/bios100/lectures/light_reaction.htm

Light Reaction again

Recap of light reaction • A photon is absorbed by photosystem II (P680) • An electron is raised from a low energy state to a high energy state • the electron then falls down to the low energy state, releasing its energy. However, this energy is not lost, it is picked up by an adjacent pigment molecule where it is used to raise an electron to a higher energy state, etc. etc., until this energy reaches the photosystem (like a bucket brigade or "the wave" at a football game) • At the photosystem, the electron is raised, but instead of falling back down, it is stolen by another, electron defficient molecule in the electron transport chain • Meanwhile the photosystem's stolen electron is replenished by photolysis, or the splitting of H2O to form H+, electrons, and O2 (note: the H+ is kept in side the thylakoid membrane). The O2 resulting is the source of all oxygen in our atmosphere • The electron travels down the electron transport system (ETS). Along the way, more H+ is pumped into the thylakoid compartment. • The electron eventually reaches photosystem I (P700), where it waits until the electron is excited by another photon • The electron is stolen by another electron acceptor from a second ETS • The final fate of the electron is in converting NADP+ to NADPH • This captures the high-energy electron and puts it into a mobile molecule, NADPH (an "electron taxi"). These high-energy electrons will be used in the Calvin Cycle to reduce CO2 to make sugars • The H+ is pumped into the thylakoid membrane to generate an H+ gradient (i.e. source of potential energy) use to later synthesize ATP

Calvin Cycle • Calvin cycle vital stats: • Requires NO light • Uses the ATP from the Light Reaction • Uses the NADPH from the Light Reaction to add hydrogen to carbon dioxide • Produces monosaccharides one carbon at at time • Occurs in the stroma of the chloroplast

Calvin Cycle Step 1: CO2 enters the plant cell via the stomas on the leaf and diffuses into the chloroplast. Step 2: This is bonded to RuBP (ribulosebisphosphate), a 5-carbon sugar. This is an unstable sugar that immediately splits into two 3-carbon sugars called PGA (phosphoglycerate). Step 3: 2 ATP molecules are used to add a phosphate to each of the PGAs.

Step 4: This energized form of PGA is then reduced by the NADPH, which converts back to NADP+ in the process. The new substance produced is PGAL (phosphoglyceraldehyde). • Step 5: Two molecules of PGAL combine to make a glucose molecule. • IMPORTANT NOTE: • The Calvin cycle must run 6 times to make a glucose molecule because the RuBP must be regenerated to keep the cycle going. So, several PGAL are generated before a glucose is finally made because some of them are used to make RuBP.

Calvin Cycle animation http://www.science.smith.edu/departments/Biology/Bio231/calvin.html

Calvin cycle diagram

Cellular Respiration All organisms, both autotrophs and heterotrophs, must break down organic molecules to supply their energy through the process of respiration. Organisms oxidize a mixture of carbohydrates, fats, and proteins for energy. We will study the oxidizing of glucose only; the complete oxidation of one molecule of glucose generates 38 ATP, which is the energy source for all cells.

C6H12O6 + 6 O2  6 CO2 + 6 H2O + ATP cellular energy • Note that amount of O2 consumed (in moles) is equal to the amount of CO2 produced. So, the rate of respiration for any organism can determined by measuring either the rate of O2 consumption or the rate of CO2 production. • There are three stages of respiration: • Glycolysis • Fermentation if no oxygen available • Oxidative respiration if oxygen is available

Glycolysis • Vital stats: • Occurs in the cytosol/cytoplasm • Breaking down one glucose by glycolysis generates a net 2 ATP, 2 NADH, and 2 3-carbon pyruvates

Glycolysis • Step 1: A 6-carbon glucose molecule is bonded to two high energy phophate group, using 2 ATP. • Step 2: The glucose-phosphate molecule breaks down to two 3-carbon sugar phosphate molecules. • Step 3: Each of these molecules donates an electron to NAD+ to make NADH and generates two ATP. • Net reaction of one glucose in glycolysis: • 4 ATPs produced – 2 ATP consumed = 2 ATP • 2 NADH produced • 2 pyruvate molecules produced

Some glycolysis animations http://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter25/animation__how_glycolysis_works.html http://www.northland.cc.mn.us/biology/biology1111/animations/glycolysis.html http://www.science.smith.edu/departments/Biology/Bio231/glycolysis.html

After Glycolysis If oxygen is present: aerobic respiration occurs in aerobic organisms. If oxygen is not present: fermentation occurs to regenerate the NAD+ so that glycolysis can resume. Anaerobes (organisms that never use oxygen) produce CO2 and ethyl alcohol in fermentation. Aerobes (organisms that use oxygen) produce CO2 and lactic acid in fermentation. NOTE: these organisms will use aerobic respiration preferentially, but sometimes oxygen is not supplied quickly enough.

Fermentation • Vital stats: • Only occurs if oxygen is not available in aerobes; always occurs in anaerobes. • The electron from NADH is simply added to a 3-C sugar to regenerate the NAD+.

Oxidative respiration • Glycolysis only generates 2 ATP and 2 NADH. The real energy from glucose is extracted in the next stage: oxidative respiration. • Vital stats: • Occurs in the mitochondria • Starts with pyruvate, the 3-C sugar generated from glycolysis. • Has two major components: the Kreb’s Cycle and the electron transport chain.

Oxidative respiration Step 1: pyruvate enters mitochondria. Step 2: A CO2 molecule and an electron are pulled off the pyruvate to make a 2-C acetyl group. The electron is donated to a NAD+ to make NADH. Step 3: The acetyl group is bonded to coenzyme A to make acetyl-CoA. Step 4: The acetyl-CoA enters the Kreb’s cycle and generates 1 ATP, 3 NADH and 1 FADH2.

Oxidative Respiration cont. • Step 5: The NADH and FADH2 enter the electron transport chain and their electrons are used to generate ATP. • Each NADH generates 3 ATP • Each FADH2 generates 2 ATP • Recap: each glucose molecule generates 2 pyruvates, 2 NADH and 2 ATP from glycolysis, 2 NADH and 2 ATP from the conversion of pyruvate to acetyl-CoA and ultimately produces 2 ATP, 6 NADH and 2 FADH2 during Kreb’s.

Total ATP from one glucose • 30 ATP from 10 NADH (10@3 ATP apiece) • 4 ATP from 2 FADH2 (2@2 ATP apiece) • 2 ATP from glycolysis • 2 ATP from making acetyl CoA • TOTAL: 38 ATP

Vocab Review Bell Work Write down these terms: Autotroph aerobic anaerobic alcoholic fermentation, ATP Calvin Cycle calorie chlorophyll glucose Kreb’s cycle glycolysis heterotroph lactic acid fermentation photosynthesis respiration

Matching Sugar formed through photosynthesis Organisms that produces its own food Organisms that cannot produce their own food Process in which autotrophs make their food Compound that stores energy in cells. Process that requires oxygen Process that requires no oxygen Process that breaks down food molecules to release energy Amount of heat required to raise 1 gram of water 1 degree Celsius

Matching cont. J. green pigment in plants that traps light energy K. anaerobic respiration of glucose that produces lactic acid L. fermentation that produces alcohol M. cycle in dark reaction of photosynthesis N. respiration reactions that produce CO2, NADH and FADH2 O. Production of ATP by converting glucose to pyruvic acid

Cellular Energy Photosynthesis and Respiration