1. Cell Respiration 3.7 and 8.1 http://www.youtube.com/watch?v=3aZrkdzrd04

2. What is cell respiration? Process by which energy in food molecules (glucose) is made available for an organism to do biological work via breakdown/being metabolized Each redox reaction causes a small amount of energy to be released; the end goal is to convert the energy into making ATP molecules Typically we discuss in terms of glucose, but other organic molecules can also be broken down; fats very important in making ATP and contribute to energy used in muscles, heart, liver, kidneys

3. OIL RIG An easy way to remember redox reactions is O – oxidation I – is L – loss R – reduction I – is G - gain Note: This is true when dealing with electrons and/or Hydrogen atoms

5. It is thought that aerobic respiration evolved after anaerobic respiration; possibly ~ 2.4 bya when O 2 accumulated on Earth The breakdown of glucose via respiration must be done in small steps in a controlled manner so that the heat produced does not destroy the cell/organism 3 steps in aerobic cellular respiration: 1)Glycolysis 2) Kreb’s cycle 3) electron transport system (ETS)

7. Step 1: Glycolysis Glucose enters the cell through the plasma membrane (via facilitated diffusion) and goes into the cytoplasm Process activated by 2 ATP molecules breaking down into ADP and phosphate (phosphate goes to energize glucose) A series of enzymes modifies and splits the 6- carbon glucose into two 3-carbon molecules of pyruvate

9. From the series of reactions in Glycolysis the following are produced: 2 Pyruvate Net 2 ATP 2 molecules NADH Let’s Review what happened in Glycolysis!

10. But first, what if NO oxygen is available: Plants and Fungi  alcohol fermentation Animals  lactate fermentation

11. Alcohol Fermentation Converts the pyruvate molecules to ethanol (ethyl alcohol) and CO 2 ; these are waste products that are given off to environment No further yield of ATP Ex: yeast for breads/beer C 6 H 12 O 6  2C 2 H 5 OH + 2CO 2 Glucose Ethanol Carbon Dioxide

13. Lactic Acid Fermentation Used by human muscle cells when oxygen is scarce Converts pyruvate molecules to lactate After strenuous exercise, you can feel the build up of lactic acid as muscle fatigue/pain; it will gradually be carried to liver via bloodstream C 6 H 12 O 6  2C 3 H 6 O 3 Glucose Lactate

15. And now, what if oxygen IS available:

16. Aerobic Respiration Cells with mitochondria and sufficient O 2 use aerobic respiration Takes place in the mitochondria Formula below: C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O + Energy (energy is ATP + heat) Most efficient pathway to produce ATP (net 36 ATP per 1 glucose)

17. The Link Reaction 1. Pyruvate enters matrix of mitochondria via active transport 2. Each pyruvate is converted to acetyl-CoA; this conversion involves the removal of: one CO 2 molecule and Hydrogen (oxidation) to make NADH

18. Acetyl-CoA sends acetyl group (2 carbon molecule) into Kreb’s cycle to start reactions and detaches to be used again For each glucose broken down in glycolysis (2 pyruvate were made) so the cycle occurs twice Kreb’s Cycle **Occurs in matrix of mitochondria**

20. Main purpose of Kreb’s Cycle: Feed electrons into the next stage of aerobic respiration via NADH and FADH 2 From the breakdown of one glucose (2 turns of the cycle): 2 ATP molecules produced 6 molecules of NADH produced 2 molecules of FADH 2 produced 4 molecules of CO 2 released Let’s Review The Kreb’s Cycle!

21. Electron Transport System (ETS) **occurs on inner membrane of mitochondria** Uses molecules that are electron carriers (easily reduced and oxidized) that are close together and vary in electronegativity (stronger pull as you go down the line)

22. ATP produced from molecules NADH and FADH 2 as they shuttle their electrons to electron carriers and their Hydrogen into the intermembrane space NADH enters system before FADH 2, therefore NADH makes 3 ATP and FADH 2 makes 2 ATP O 2 is final electron acceptor… making H 2 0

23. The electron carriers use some of the energy from the redox reactions to pump H + across mitochondrial membrane so that ATP synthase can use the H + energy gradient to convert ADP + Phosphate to ATP Note: The ETS has allowed for Chemiosmosis and Oxidative Phosphorylation Chemiosmosis – the movement of H + ions to provide energy Oxidative Phosphorylation – using an electron transport chain to make ATP

24. Let’s Review the Electron Transport System! Summary of ATP Production in Cell Respiration ProcessATP usedATP producedNet ATP gain Glycolysis242 Kreb’s Cycle022 ETS and Chemiosmosis 032 Total238 36