RECAP Photosynthesis produces: Oxygen Sugar (glucose) How will these substances be used to make ATP for the organism?

Cellular Respiration Chemical bond energy in food molecules is converted to a form that can be used by the cell (ATP)

Energy stored in food is measured in calories Fats store more energy per gram than do carbohydrates and proteins

Cellular Respiration may be: Anaerobic: doesn’t require oxygen Aerobic: requires oxygen

Anaerobic Respiration Makes a small amount of usable energy without using oxygen Reactions occur in cytoplasm Produces 2 ATP per glucose molecule

Takes place in yeast, and bacteria Can also occur in human muscle cells if no oxygen is present.

Anaerobic Respiration Glycolysis: (sugar is “split”) Glucose is only partially broken down Not all of it’s stored energy is released C6H12O6 + 2 ATP → 2 pyruvic acid + 4 ATP (6-carbon) (3-carbon) Net gain of energy is 2 ATP Are produced Needed to start

What Happens to Pyruvic Acid?

What happens to Pyruvic Acid? Fermentation of Alcohol (Oxygen not present) C6H12O6 → Ethyl Alcohol + CO2 + 2ATP Happens in Yeast Pyruvic acid (from split glucose) is turned into ethyl alcohol and CO2 (carbon dioxide)

Useful in the brewing and baking industries Produces alcohol Produces carbonation Bubbles of CO2 make bread rise

What happens to Pyruvic Acid? Fermentation of Lactic Acid: (Oxygen not present) C6H12O6 → Lactic Acid + 2ATP Happens in some bacteria Pyruvic acid (from split glucose) becomes lactic acid Used to make cheese, yogurt and buttermilk

GLYCOLYSIS Alcohol Fermentation Lactic Acid Fermentation

Let’s Try This Activity: Finger “Crunches” As fast as possible crunch your fingers 100 times

Lactic Acid buildup in human muscle cells During intense exercise, if oxygen is not present, human muscle cells use anaerobic respiration to produce some energy, yielding lactic acid Lactic acid builds up Muscles eventually cramp up (burning feeling)

Oxygen Debt: Eventually Lactic acid goes to your liver where it is changed back into glucose which can be used again. In order to convert the lactic acid, your body needs oxygen

When You Die

Anaerobic Respiration

Glycolysis happens in cytoplasm To produce more ATP, (if oxygen present) reactions must take place in the Mitochondria

Mitochondria Structure

Aerobic Respiration Makes more ATP using oxygen Occurs in mitochondria Most eukaryotic organisms carry out aerobic respiration Plants also carry out respiration!!!

Glucose gets completely broken down to release energy Releases more energy than anaerobic respiration (more energy efficient) Most of the CO2 and H2O you exhale is produced from aerobic respiration C6H12O6 + O2 → CO2 + H2O + 36 ATP

Aerobic Respiration Summary

3 Steps of Aerobic Respiration Step 1: Glycolysis Same as in anaerobic respiration Doesn’t require oxygen Takes place in cytoplasm Glucose is split producing 3-carbon pyruvic acid Also produces NADH from NAD+ This “carries” some high energy electrons and H+ Net production of 2 ATP

Step 2: Kreb’s Cycle (Citric Acid Cycle) Requires oxygen Pyruvic acid from glycolysis enters mitochondria Reactions occur in mitochondrial matrix Produces high energy electron/hydrogen carriers NADH and FADH2 (called coenzymes) These molecules carry “H+” and high energy electrons These will be used later to help produce more ATP Produces CO2 gas Produces 2 ATP

Aerobic Respiration Summary

Step 3: Electron Transport Chain Requires oxygen Occurs on inner membrane of mitochondria Uses high energy electrons and H+ to convert ADP to ATP Uses the NADH/FADH2 from glycolysis & Krebs cycle Final electron & hydrogen acceptor is oxygen (which then becomes H2O which is released) Produces 32 ATP!!! Produces H2O

Animation of Electron Transport Chain Note that Oxygen is the final electron acceptor and accepts 2 H+ to become water! http://vcell.ndsu.nodak.edu/animations/etc/movie-flash.htm

Respiration Animation http://www.qcc.cuny.edu/BiologicalSciences/Faculty/DMeyer/respiration.html

Anaerobic Phase Doesn’t need O2 Aerobic Phase Needs O2

Efficiency of Cellular Respiration Anaerobic: Yields 2 ATP per glucose End products of fermentation still contain a lot of unused potential energy Meets energy needs of simple organisms Aerobic: Yields 36 ATP per glucose More efficient 45% of the energy available in glucose is transferred to ATP where it can do further work for the cell Note: Car engines only converts about 25% of the energy from gasoline

Respiration of Fats and Proteins Get broken down and converted into amino acids, glycerol and fatty acids These can enter respiration pathway at different points Fats yield twice as much ATP as glucose Proteins yield about the same as glucose but are not the preferred energy source for the cell

Evolution of Cellular Respiration First life originated when there was hardly any oxygen in the atmosphere. (Probably prokaryotes with few organelles and no mitochondria) Glycolysis was the first biochemical process to evolve Happens in cytoplasm and no oxygen needed.

Comparing Photosynthesis and Cellular Respiration How are these two processes related to each other? In a typical plant cell describe the way energy is obtained and utilized through both photosynthetic and respiration processes. Include the materials that need to be taken in and released

Comparing Photosynthesis and Respiration