3.7 & 8.1

Cellular Respiration

IB Biology

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+/NADHNAD+ = Nicotinamide Adenine DinucleotideAn organic molecule that cells make from the vitamin niacin (B3) It is used to carry electrons during cell respirationThe 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 RespirationControlled release of energy in the form of ATP from organic compounds in cellsEnergy 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 energyEnergy used in many processes inside cellThe reactions release small amounts of energy and the cell stores some of the energy in ATPTypes:

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

ATPAdenosine Triphosphate (type of nucleotide)Cells generate ATP by phosphorylation: adding a phosphate group to ADP (adenoside diphosphate)

Glycolysis Summary10 stepsoccurs in the cytoplasmglucose (6 carbons) is broken down into two pyruvate molecules (3 carbons each)2 ATP are consumed4 ATP are producedNET GAIN OF 2 ATP2 NADH are produced which can be used to make more ATP later onhttp://www.youtube.com/watch?v=x-stLxqPt6E If there is O2 : pyruvate enters the mitochondria, is transformed into Acetyl-CoA and the Krebs Cycle startsIf 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)

Mitochondria2 membrane layers = outer and inner membrane (contain proteins/enzymes)cristae = folds = large surface areaFluid =matrix

The Link ReactionPyruvate needs to be modified to enter the Krebs CycleCO2 is removed from pyruvatethe remaining molecule (acetic acid) binds with coenzyme A (made of protein and vitamin B5) Acetyl CoA is producedNADH is formed2 CO2 are releasedPyruvate + CoA + NAD = AcetylCoA + CO2 + NADH + H

The Krebs Cyclealso known as the CITRIC ACID CYCLEoccurs in the matrix of the mitochondriaonly occurs if there is O2pyruvate 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 ATPmajor 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 cristaeNADH 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 waterElectron movement allows H+ to be pumped from the matrix to the intermembrane spaceThis process is called CHEMIOSMOSISEnergy 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 respirationLong fatty acid chains are oxidizedSections containing 2 carbon atoms break offThese are changed to acetyl-CoA and enter the Krebs cycleAn eight-carbon fatty acid can produce 4 acetyl-CoA's

C H

C H

C H

C H

C H

C H

C H

C H

C H

C H

C H

C H

C H

C H

C H

C H

C H

C O O H

3

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

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Stea ric ac id

VideosGlycolysis: 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=relatedhttp://www.youtube.com/watch?v=zfvVvC4-u_A&feature=related

CELL RESPIRATION GUIDE!!!Cell respiration is the breakdown of organic molecules to release energyCell 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 mitochondrionPyruvate enters the mitochondrionPyruvate is converted into Acetyl-CoA – This is called the Link Reaction

In the Link Reaction, NADH and CO2 are producedAcetyl-CoA enters the KREBS CYCLE2 CO2, 2 ATP, 3 NADH and 1 FADH2 are produced in one Krebs CycleTwo cycles occur for each glucose molecule usedNADH and FADH2 take the electrons (and H+) to proteins embedded in inner mitochondria membraneThis 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!