3.7.1 Define cell respiration [Cell respiration is the controlled release of energy from organic compounds in cells to form ATP]

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1 3.7 Cell respiration ( Chapter 9 in Campbell's book) Define cell respiration [Cell respiration is the controlled release of energy from organic compounds in cells to form ATP] Organic compounds store energy in covalent bonds mainly carbon-carbon and in electrons on the hydrogens bonded to the carbons. Glucose respiration yields 686kcals of energy per mole, it is an exergonic reaction. This means the products of respiration store less energy than the reactants. Adenosine Tri-Phosphate ATP is the currency of energy It is "spring-loaded" due to the negative charges of the phosphate groups. ATP is regenerated by adding phosphate to ADP mainly done in mitochondria. Phosphorylation Phosphorylation includes any reaction that adds a phosphate group to a molecule. Addition of the phosphate group to the target molecule in a reaction gives energy to the target molecule. ATP adds phosphate groups to molecules.

2 NADH (Nicotinamide Adenine Dinucleotide) NADH is another energy carrier molecule like ATP. It is a coenzyme used to generate ATP via the electron transport chain. Electrons are first added to NAD+. NAD+ receives the electrons and a proton becoming a neutral NADH. ( a similar molecule is FADH 2 ) C 3.1 State that oxidation involves the loss of electrons from an element, wheras reduction involves a gain of electrons; and that oxidation frequently involves gaining oxygen or losing hydrogen, wheras reduction frequently involves losing oxygen or gaining hydrogen. oxidation/reduction reactions redox reactions These are key to life's processes. Electrons are lost from one molecule ( oxidation) and at the same time added to another ( reduction). They are always coupled reactions. It is the movement of electrons and protons ( H+) that transfer energy. Oxygen is a strong oxidizer, it removes electrons from other molecules. glucose is oxidized it gives electrons to oxygen which is reduced.

3 Electrons move "downhill" towards the ultimate electron acceptor oxygen State that, in cell respiration, glucose in the cytoplasm is broken down by glycolysis into pyruvate with a small yield of ATP 3.2 Outline the process of glycolysis, including phosphorylation, lysis, oxidation and ATP formation Respiration occurs in 3 general phases: Glycolysis, Kreb's cycle and the electron transport chain. Glycolysis means "splitting of sugar" 6-carbon glucose is split into two 3-carbon pyruvate molecules

4 Initially, 2 ATP have to be added The yield is 4 ATP and 2 NADH and 2 pyruvate molecules and Net gain is 2 ATP and 2 NADH + H + substrate level phosphorylation An enzyme adds the phosphate group to ADP yielding the 2 ATP ( compare to oxidative phosphorylation in the electron transport chain) No oxygen is required at all, no CO 2 is released NADH can be converted to ATP via Electron transport chain if oxygen is available. Pyruvate can enter the Kreb's cycle or undergo fermentation Explain that, during anaerobic cell respiration, pyruvate can be converted in the cytoplasm into lactate, or ethanol and carbon dioxide, with no further yield of ATP [Mention that ethanol and carbon dioxide are produced in yeast, whereas lactate is produced in humans] Fermentation ATP can be produced at a lower rate without oxygen. In order to keep generating ATP, the NAD+ has to be regenerated otherwise the reactions stop. Fermentation is a means of regenerating this key oxidizing agent.

5 Alcohol fermentation transfers the H+ and electrons from NADH to pyruvate in a couple of steps making ethanol. 4 Lactic acid fermentation transfers the H+ and electrons to lactic acid Some yeasts, many bacteria and our muscle cells, can alternate between aerobic and anaerobic respiration. If oxygen is available, they use it because it can make as much as 19 times more ATP 3.3 Draw and label a diagram showing the structure of a mitochondrion as seen in electron micrographs. 3.6 Explain the relationship between the structure of the mitochondrion and its function. [ Limit this to cristae forming a large surface area for the electron transport chain, the small space between inner and outer membranes for accumulation of protons, and the fluid matrix containing enzymes of the Kreb's cycle.] Explain that, during aerobic cell respiration, pyruvate can be broken down in the mitochondrion into carbon dioxide and water with a large yield of ATP

6 3.4 Explain aerobic respiration, including the link reaction, the Krebs cycle, the role of NADH +H+, the electron transport chain and the role of oxygen. Link reaction Pyruvate is decarboxylated ( CO2 is removed) The remaining two-carbon molecule (acetyl group) reacts with reduced coenzyme A, and, at the same time, one NADH + H+ is formed. Krebs cycle..in mitochondrial matrix, releases CO 2 yields 6 NADH, 2 FADH2, 2 CO2, and 2ATP from substrate level phosphorylation Electron transport chain on inner mitochondrial membrane, uses oxygen, water is formed yields 34 ATP This is oxidative phosphorylation Kreb's Cycle takes place in the mitochondrial matrix 3 carbon pyruvate is converted to 2 carbon Acetyl CoA releasing CO 2 The pyruvate is decarboxlylated the carboxyl group is removed from the pyruvate. Each turn of the Kreb's cycle, 2 carbons enter as Acetyl CoA, 2 carbons leave as CO2. 3 NADH, 1 FADH 2 and 1 ATP are produced. A glucose provides two turns of the cycle. ( 2 pyruvates from glycolysis)

7 Note that most energy from the Kreb's cycle resides in the NADH and FADH 2 Electron transport chain Electron transport chain is where the ATP is mostly produced. A series of enzymes are imbedded in the cristae, or inner membrane of the mitochondria. Many of these enzymes, cytochromes, incorporate iron, like hemoglobin does. 3.5 Explain oxidative phosphorylation in terms of chemiosmosis Chemiosmosis is how ATP is produced. The H + proton is the source of power to produce ATP There is a concentration gradient across the inner membrane. H + is pumped into the mitochondria matrix by the electron transport chain. When it diffuses back across the membrane through special channels, the energy is used to add P to ADP Respiration is about 40% efficient. 60 % is lost as heat. By comparison, automobiles extract 25% of energy in gasoline. In order to consume proteins, their amino groups must first be removed deamination. Then enzymes can break up the carbon chains to enter the Kreb's cycle.

8 In order to consume fats, the fatty acids are broken up into fragments that enter the Kreb's cycle as Acetyl CoA. Fatty acids have lots of energy, and can produce twice as much ATP as glucose per unit weight. Intermediate molecules of the Kreb's cycle can be shunted off to be used as precursors to other important molecules needed in the cells. The 10 amino acids that we can make are made from Kreb's cycle molecules. 3.7 Analyse data relating to respiration