Biology-Cell Respiration

NAD and FAD

-They are required for normal cellular respiration. They carry protons or electrons from glycolysis and the krebs cycle to the electron transport chain. -They facilitate the transfer of hydrogen atoms from a substrate, such as glucose, to its coenzyme NAD+. -Without NAD+ to accept electrons and protons from glycolysis and the Krebs Cycle, both processes would cease and the cell would die. -they are vitamin derivatives -NAD+ is the oxidized form of NADH -FAD is the oxidized form of FADH2

Structures of the mitochondria

-enclosed by a double membrane. The outer membrane is smooth, but the inner membrane (Cristae) is folded. Divided the mitochondria into two internal compartments, the outer compartment and the matrix. The Krebs Cycle takes place in the matrix; the electron transport chain take place in the cristae membrane.

Summary of ATP production

-substrate level phosphorylation occurs when an enzyme, a kinase, transfers a phosphate from a substrate directly to ADP. Only a small amount of ATP is produced this way. This is the way energy is produced during glycolysis and the Krebs Cycle -oxidative phosphorylation occurs during chemiosmosis. This is the way that 90% os all ATP is produced from cell respiration. During oxidative phosphorylation, NAD and FAD lose protons (become oxidized) to the electron transport chain, which pumps them tot he outer compartment of the mitochondrion, creating a steep proton gradient. This electrochemical or proton gradient powers the phosphorylation of ADP into ATP.

Steps in the Citric Acid Cycle

1. Acetyl co-A combines with oxaloacetic acid to produce citric acid; hence the name citric acid cycle 2. Remember that each molecule of glucose is broken down to 2 molecules of pyruvate during glycolysis. Therefore, respiration of each molecule of glucose causes the krebs cycle to turn 2 times 3. Before it enters the Krebs cycle, pyruvate must first combine with coenzyme A to form acetyl co-A, which does enter the Krebs Cycle. This process produces 2 NADH, 1 NADH for each pyruvate. 4. Each turn of the krebs cycle releases 3 NADH, 1 ATP, 1FADH, and waste product of CO2, which is exhaled 5. During the Krebs Cycle, ATP is produced by the substrate-level phosphorylation--direct enzymatic transfer of a phosphate to ADP. Very little energy is produced this way compared with the amount produced by oxidative phosphorylation.

catabolism breakdown in order

1. Glycolysis 2.pyruvate oxidation 3. citric acid cycle 4. produces coenzymes NADH and FADH2 5. Coenzymes are oxidized by the ETC and ATP is produced by oxidative phosphorylation

glycolysis

10 step process that breaks down 1 molecule of glucose into 2 3-carbon molecules of pyruvate or pyretic acid and releases 4 molecules of ATP. 2 ATPs are taken to do the reaction of glycolysis. Occurs in the cytoplasm and produces ATP without using oxygen. Each step is catalyzed by different enzymes. The process only releases 1/4th of the energy in glucose and make pyretic acid which is the raw material for the Krebs cycle, which the next step in aerobic respiration. ATP is produced by substrate level phosphorylation by direct enzymatic transfer of a phosphate to ADP. Only small amount of ATP is produced. Phospofructokinase (PFK), is an allosteric enzyme. It inhibits glycolysis when the cell contains enough ATP and does not need to produce any more. If ATP is present in the cell in large quantities, it inhibits PFK by altering the conformation of that enzyme, thus stopping glycolysis. As the cell uses up ATP, less ATP is available to inhibit PFK and glycolysis continues to produce more ATP. Cell is regulating through allosteric inhibition.

oxidative phosphorylation

an enzymatic process in cell metabolism that synthesizes ATP from ADP by the oxidation of the carrier molecules NADH and FADH2. -Powered by redox reactions of the electron transport chain -protons are pumped from the matrix to the outer compartment by the electron transport chain. The electron transport chain is an energy converter that couples the exergonic flow of electrons with the endergonic pumping of protons across the cristae membrane and into the outer compartment. -proton gradient is created between the outer compartment and the inner matrix -protons cannot diffuse through the cristae membrane; they can flow only down the gradient into the matrix through the ATP synthase channel. As protons flow through the proton channel, it fuses ADP w/ phosphate to make ATP. -Oxygen is the final hydrogen acceptor, combining 1/2 an oxygen molecules with 2 electrons and 2 protons, thus forming water. Water is a waste product of cellular respiration and is excreted.

facultative anaerobic process

can tolerate the presence of oxygen; they simply do not use it

obligate anaerobes

cannot live in an environment containing oxygen

alcoholic fermentation

certain cells convert pyruvate from glycolysis into ethyl alcohol and carbon dioxide in the absence of oxygen and in that process oxidize NADH+ back into NAD+. Ex. yeast to produce carbon dioxide and make bread rise beer to ferment sugar into alcohol

ATP

consists of adenosine and 3 phosphates. It is an unstable molecule because the 3 phosphates are all negatively charged, and she one phosphate groups is removed from ATP through hydrolysis turns into a more stable molecule, ADP. This transformation releases energy.

anaerobic/fermentation respiration

glycolysis is followed by either alcoholic fermentation or lactic acid formation, not a synonym for glycolysis. Originated when there was not free oxygen on Earth. There are 2 types of anaerobes: facultative or obligate Fermentation can generate ATP during anaerobic respiration only as long as there is an adequate supply of NAD+ to accept electrons during glycolysis. Without some mechanism to convert NADH+ back to NAD+, glycolysis would shut down. Fermentation consists of glycolysis plus the reactions that regenerate NAD+. There are 2 types of fermentation: alcohol and lactic acid

aerobic transpiration

glycolysis is the first phase followed by the Citric Acid cycle, Krebs Cycle, the electron transport chain, and oxidative phophorylation. Glycolysis is the anaerobic cycle that is followed by the krebs and oxidative phosphorylation which are aerobic.

electron transport chain

proton pump is the mitochondria that couples two reactions, one exergonic and one endergonic. It uses the energy released from the exergonic flow of electrons to pump protons against a gradient from the matrix to the outer compartment. This results in a proton gradient inside the mitochondrion. The electron transport chain makes no ATP directly but sets the stage for ATP production through chemiosmosis. -collection of molecules embedded into the cristae membrane of the mitochondrion -thousands of copies of ETC in every mitochondrion due tot he extensive folding of the cristae membrane -the ETC carries electrons delivered by the NAD and FAD from glycolysis and the Krebs cycle to oxygen, the final electron acceptor, through a series of redox reactions. In a redox reaction, one atom gains electrons or protons (Reduction), and one atom loses electrons (oxidation). -highly electronegative oxygen acts to pull electrons through the electron transport chain -NADH delivers its electrons to a higher energy level in the chain that does FAHD2. NADH provides more ATP than FADH does. NADH=3 and FADH2=2 -ETC consists mostly of cytochromes. There are proteins structurally similar to hemoglobin. Cytochromes are present in all aerobes and are used to trace evolutionary relationships.

lactic fermentation

pyruvate from glycolysis is reduced from lactic acid or lactate. NADH+ gets oxidized back to NAD+. ex. human skeletal muscles do this anaerobic fermentation during strenuous exercise that depletes the bioavailable oxygen and produce lactic acid until oxygen levels are restored.

krebs cycle

takes place in the matrix of the mitochondria and requires pyruvate, the product of glycolysis. The Krebs cycle completes the oxidation of glucose to CO2. Each cycle produces 1 ATP and 2 turns per glucose molecule added by substrate-level phosphorylation, but most of the chemical energy is transferred from NADH+ to FAD. The reduced coenzymes of NADH+ and FAD2, shuttle high energy electrons into the electron transport chain in the cristae membrane.

Cell respiration

the means by which cells extract energy stored in food and transfer that energy to molecules of ATP. There are 2 types: anaerobic and aerobic

chemiosmotic theory

the process of oxidative phophorylation. The process uses potential energy storedin the proton (H+) gradient to phosphorylate ADP and produces ATP