Cellular Respiration 3.7 & 8.1

Cellular Respiration 3.7 & 8.1

Redox • Redox = oxidation/reduction reaction • Oxidation- loss of electrons - oxidized when it loses one or more e- • Reduction - gain of electrons- reduced when it gains one or more e- • Hint: to follow the electrons, look at where hydrogen goes

NAD+/NADH • NAD+ = NicotinamideAdenine Dinucleotide • An organic molecule that cells make from the vitamin niacin (B3) • It is used to carry electrons during cell respiration • The electrons added to NAD+ in making NADH carry energy the cell has harvested and can eventually use

Common Redox Reactions in Cellular Respiration: • C4H6O5 + NAD+ C4H4O5 + NADH + H + • What is being oxidized? • C4H6O5 • What is being reduced? • NAD+ Malic acid Tartaric acid

Another Carrier Molecule... FAD+/FADH2 • Flavin adenine dinucleotide

Cell Respiration • Controlled release of energy in the form of ATP from organic compounds in cells • Energy released is carried by electrons • At each step electrons start out in a molecule with more energy and end up in a molecule with less energy • Energy used in many processes inside cell • The reactions release small amounts of energy and the cell stores some of the energy in ATP • Types: • Aerobic: with O2 (Glycolysis + Krebs Cycle + Electron Transport Chain) • Anaerobic: without O2 (Glycolysis only) • Organic compounds used: glucose and fats (amino acids in extreme situations)

Common Step

ATP • Adenosine Triphosphate (type of nucleotide) • Cells generate ATP by phosphorylation: adding a phosphate group to ADP (adenosidediphosphate)

Glycolysis Summary • 10 steps • occurs in the cytoplasm • glucose (6 carbons) is broken down into two pyruvate molecules (3 carbons each) • 2 ATP are consumed • 4 ATP are produced • NET GAIN OF 2 ATP • 2 NADH are produced which can be used to make more ATP later on • http://www.youtube.com/watch?v=x-stLxqPt6E • If there is O2 : pyruvate enters the mitochondria, is transformed into Acetyl-CoA and the Krebs Cycle starts • If there is no O2 : pyruvate is transformed into lactic acid or ethanol (fermentation)

When there is no O2... • Anaerobic Respiration (or fermentation) Alcoholic fermentation - Occurs in yeast/bacteria Lactic acid fermentation - Occurs in muscle cells (humans and other mammals)

Mitochondria • 2 membrane layers = outer and inner membrane (contain proteins/enzymes) • cristae = folds = large surface area • Fluid =matrix

The Link Reaction • Pyruvate needs to be modified to enter the Krebs Cycle • CO2 is removed from pyruvate • the remaining molecule (acetic acid) binds with coenzyme A (made of protein and vitamin B5) • Acetyl CoA is produced • NADH is formed • 2 CO2 are released • Pyruvate + CoA + NAD = AcetylCoA + CO2 + NADH + H

The Krebs Cycle • also known as the CITRIC ACID CYCLE • occurs in the matrix of the mitochondria • only occurs if there is O2 • pyruvate ends up as CO2 and H2O • 1 glucose  2 pyruvate  2 acetyl-CoA 2 cycles • Products: • 2 ATP • 6 NADH • 2 FADH2 • 4 CO2's are released • NADH and FADH2 = used in the electron transport system (mitochondria cristae) to create large amounts of ATP • major objective = to get the hydrogens, along with their electrons, off the carbon compounds so they can be carried to the electron transport proteins that are embedded in the membrane of the mitochondrion.

Krebs Cycle Summary

Electron Transport Chain • Involves proteins embedded in the mitochondria’s inner membrane and cristae • NADH and FADH2 lose electron to proteins (H+ are released from NAD) • Electrons move from one protein to another (due to different electronegativity levels) • Oxygen accepts low energy electrons and binds with hydrogen creating water • Electron movement allows H+ to be pumped from the matrix to the intermembrane space • This process is called CHEMIOSMOSIS • Energy from H+ is used to make ATP Synthase work: phosphate is added to ADP to make 32 ATP

Fats and Cell Respiration • Fatty acids can also be used in cell respiration • Long fatty acid chains are oxidized • Sections containing 2 carbon atoms break off • These are changed to acetyl-CoA and enter the Krebs cycle • An eight-carbon fatty acid can produce 4 acetyl-CoA's

Videos • Glycolysis: http://www.youtube.com/watch?v=x-stLxqPt6E • Krebs Cycle: http://www.youtube.com/watch?v=aCypoN3X7KQ&feature=related • ATP Synthase: http://www.youtube.com/watch?v=3y1dO4nNaKY&feature=related • Electron Transport Chain: http://www.youtube.com/watch?v=xbJ0nbzt5Kw&feature=related http://www.youtube.com/watch?v=Idy2XAlZIVA&feature=related • Cell Respiration Overview: http://www.youtube.com/watch?v=Biq1xo-1eyo&feature=related • http://www.youtube.com/watch?v=zfvVvC4-u_A&feature=related

Cell respiration is the breakdown of organic molecules to release energy • Cell respiration can occur with O2 (aerobic) or without O2 (anaerobic) • The first step of cell respiration, called GLYCOLYSIS , involves the breakdown of glucose into pyruvate • This step is done with 10 chemical reactions • During glycolysis, 2 ATP and 2 NADH are formed • If there is no O2 available, the process ends in the cytoplasm • Yeast will convert pyruvate into ethanol and CO2 – 2 ATP are produced in this process • Muscle cells will convert pyruvate into lactic acid • If there is O2 available, the process continues in the matrix of the mitochondrion • Pyruvate enters the mitochondrion • Pyruvate is converted into Acetyl-CoA – This is called the Link Reaction • In the Link Reaction, NADH and CO2 are produced • Acetyl-CoA enters the KREBS CYCLE • 2 CO2, 2 ATP, 3 NADH and 1 FADH2 are produced in one Krebs Cycle • Two cycles occur for each glucose molecule used • NADH and FADH2 take the electrons (and H+) to proteins embedded in inner mitochondria membrane • This step is called ELECTRON TRANSPORT CHAIN • Electrons move from one protein to another • Oxygen accepts the electrons and binds with hydrogen: water is created • H+ move from the matrix to the intermembrane space • H+ gradient is created • H+ move back to matrix through enzyme called ATP Synthase: 32 ATP are created!

Cellular Respiration 3.7 & 8.1