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Ch 9: Respiration.

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Presentation on theme: "Ch 9: Respiration."— Presentation transcript:

1 Ch 9: Respiration

2 The Big Picture Cellular respiration has the sole purpose to produce ATP. Its an exergonic reaction. Can be summarized as a whole as: Glucose + Oxygen CO2 + Water+ ATP

3 Reminder on ATP ATP (adenosine triphosphate) is a nucleotide with unstable phosphate bonds that the cell hydrolyzes for energy. Cells use ATP to continue cellular work. But they must replenish the ATP supply to continue cellular work. Respiration does this.


5 Redox reactions These are the energy-shuttling mechansisms of metabolism Partial or complete gain of electrons=reduction Partial or complete loss of electron=oxidation They are always coupled…so in order for a material to lose an electron, another molecule must accept it

6 The NAD+, NADH, FAD+, FADH NAD+ and FAD+ are coenzymes that function in the redox reactions and are found in all cells. Traps energy-rich electrons from glucose or food. NAD+= oxidized coenzyme NADH= reduced coenzyme

7 Why glucose? C6H12O6 It’s the energy source used most often by living organisms. Keep in mind that fats and proteins could also be considered but glucose is the “hallmark” molecule to use in cellular respiration

8 Glycolysis, Krebs Cycle, and Oxidative Phosphorylation
1. Glycolysis is the decomposition of glucose to pyruvate (or pyruvic acid) 2. Krebs Cycle takes pyruvate (1 pyruvate) and yields electron acceptors and ATP. 3. Oxidative phosphorylation extracts ATP from NADH and FADH2.

9 Cellular Respiration Process that releases energy by breaking down glucose & other food molecules in the presence of oxygen Glycolysis Cellular Respiration Two Stages: Krebs Cycle Electron Transport Chain

10 Glyclolysis (per glucose molecule)
Takes place in cytosol. Mutiple steps (9 or 10 depending on source) in the process of decomposing glucose into pyruvate. Mg2+ ions are cofactors to help. 2 ATP go IN 4 ATP PRODUCED (so what is NET?) 2 NAD+ go IN 2 NADH PRODUCED 2 Pyruvate (Pyrivic acid) PRODUCED

11 Glycolysis Breaks down “Glucose” (6-carbon sugar) into 2 molecules of “Pyruvic Acid” (3-carbon compound) The products are: 2 Pyruvic Acid molecules 2 ATP molecules 2 NADH molecules

12 Glycolysis has 2 pathways…
If Oxygen is present (Aerobic) ...“Krebs Cycle”… then to Electron Transport Chain If Oxygen is absent (Anaerobic) … “Fermentation”… (directly to Electron Transport Chain)

13 KREBS Cycle (per pyruvate)
Takes place in mitochondrial matrix. Pyruvate combines with CoA (coenzyme A) to make acetyl CoA. This makes 1 NADH and 1 CO2. Acetyl CoA combines with OAA to form citric acid. (7 intermediate products). 3 NADH and 1 FADH2 are made and CO2 released. 1 ATP is made. How much total ATP then for Krebs?

14 KREBS CYCLE (Aerobic Pathway)
Pyruvic Acid is broken down into CO2 in a series of energy extracting reactions

15 ETC (Oxidative Phosphorylation)
Takes place in inner mitochondrial membrane Involves a passing of electrons through a series of membrane associated electron carriers in the mitochondria to ultimately produce ATP You shuffle electrons to pump protons across the mitochondiral membrane against a concentration gradient to help establish a proton gradient


17 The ETC transports electrons from NADH and FADH2 along a transport chain
The respiratory chain is composed of 4 enzyme complexes and carriers called cytochrome c and ubiquinone (Q). The 1st two complexes shuttle the electrons of NADH + H+ and FADH2 to Q. The third complex moves electrons from Q to chytochrome c. The final complex passes electrons to O2, an ultimate acceptor, which results in H20 as a by-product

18 That chain is an energy converter that pumped H+ across the membrane
That chain is an energy converter that pumped H+ across the membrane. How? Certain members along the electron transport chain accept and release protons along with electrons. A gradient is created that is referred to as the proton-motive force Now this H+ has the capacity to do work


20 This electron transport chain made no ATP directly, but it did ease the fall of electrons from food to oxygen So now, by chemiosmosis, it will couple this electron transport and energy release to ATP synthase ATP synthase is an enzyme that catalyses ATP from ADP and an inorganic phosphate Each NADH produces 3 ATP Each FADH produces 2 ATP


22 To summarize… Glycolysis makes 2 NET ATP and 2 NADH and
2 pyruvate 2 acetyl CoA = 2 NADH Krebs Cycle: 6 NADH, 2 FADH2, 2 ATP Since each NADH produces 3 ATP during oxidative phosphorylation and each FADH2 produces 2 ATP…how many ATP total?

23 Wait…but what if there is no oxygen?
What will be affected? Well now there is no electron acceptor to accept electrons at the end of the ETC. NADH will accumulate. Once all NAD+ has been made to NADH, Krebs and glycolysis will eventually stop. We have to free NAD+ to allow glycolysis to continue! We must release some NAD+ for use by glycolysis

24 FERMENTATION (Aanerobic Pathway)
Alcoholic : Yeast & other microorganisms use this to produce alcohol & CO2 as wastes. Beer is a beverage made by alcoholic fermentation 2 TYPES: Alcoholic & Lactic Acid

25 Alcoholic Fermentation
Commonly done by yeast in an anaerobic environment. 1) Glycolysis is done as normal. And then, to regenerate the NAD+… 2) Pyruvate  acetaldehyde 3) Acetaldehyde ethanol…the energy in NADH is used to drive this reaction and this will release NAD+. For each acetaldehyde, 1 ethanol is made and 1 NAD+ is produced. Now we have made 2 ATP from glyocolysis for each 2 converted pyruvate


27 Or…we can do Lactic Acid Fermentation
(Aanerobic Pathway) Lactic Acid: Exercise causes the body needs more oxygen for respiration to make more ATP Body resorts to lactic acid fermentation to make ATP Lactic Acid is also produced causing burning sensation in muscles

28 Lactic Acid Fermentation
Commonly done by: Muscle cells during oxygen debt. Same thing as before: -do glycolysis -but then to regenerate NAD+, a byproduct called lactate is made instead of acetylaldehydeethanol.


30 Diagram Assignment You will diagram the major pathways to respiration in color in a way that is understandable to you. Use websites and the book to help you form diagrams for each section of respiration. It must be in color, complete, and have words on it to describe what is happening in the process for full credit. Also must have an input/output chart by each stage: glycolysis, krebs, + ETC

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