Cellular Respiration

Food=chemical energy Cellular Respiration All living things need energy Energy in the form of… Food=chemical energy Cell energy=ATP

How Do We Get Energy From ATP? By breaking the high- energy bonds between the last two phosphates in ATP Copyright Cmassengale

When is ATP Made in the Body? During a Process called Cellular Respiration that takes place in both Plants & Animals Copyright Cmassengale

What is cellular respiration ? Cellular respiration is the set of the metabolic reactions and processes that take place in the cells of organisms to convert biochemical energy from nutrients into (ATP), The reactions involved in respiration are catabolic reactions, which break large molecules into smaller ones, releasing energy

Copyright Cmassengale Cellular Respiration Includes pathways that require oxygen Breakdown of one glucose molecule produces 38 ATP molecules Copyright Cmassengale

Overall Equation for Cellular Respiration C6H12O6 + 6O2 YIELDS 6CO2 + 6H20 + 38ATP’s

Important Molecules in Cellular Respiration CO2 – Carbon Dioxide ATP – Adenine triphosphate NAD – Nicotinamide adenine dinucleotide FAD – Flavin adenine dinucleotide

What are the Stages of Cellular Respiration? STEP 1 - Glycolysis STEP 2 - The Krebs Cycle STEP 3 - The Electron Transport Chain (ETC)

Where Does Cellular Respiration Take Place? It actually takes place in two parts of the cell: Glycolysis occurs in the Cytoplasm Krebs Cycle & ETC Take place in the Mitochondria

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STEP 1 Glycolysis Glycolysis is takes place in the cytosol of cells in all living organisms. This pathway can function with or without the presence of oxygen. process converts one molecule of glucose into two molecules of pyruvate (pyruvic acid),

generating two net molecules of ATP. Four molecules of ATP per glucose are actually produced, however, two are consumed as part of the preparatory phase. The overall reaction can be expressed this way: Glucose + 2 NAD+ + 2 Pi + 2 ADP → 2 pyruvate + 2 NADH + 2 ATP + 2 H+ + 2 H2O + heat

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Glycolysis Summary Produces 2 NAD and 4 ATP molecules (2 ATP Used & 4 Produced so overall 2 ATP molecules from glycolysis) 2 molecule of Pyruvate

Steps 2: The Fate of PYRUVATE 1. As pyruvate enters the mitochondrion, a modifies pyruvate to acetyl CoA which enters the Krebs cycle in the matrix. 2. A carboxyl group is removed as CO2. 3. A pair of electrons is transferred from the to NAD+ to form NADH

2 molecule of pyruvate produce 2 NADH

When oxygen is present, the mitochondria will undergo aerobic respiration which leads to the Krebs cycle. However, if oxygen is not present, fermentation of the pyruvate molecule will occur. In the presence of oxygen, when acetyl-CoA is produced, the molecule then enters the citric acid cycle (Krebs cycle)

inside the mitochondrial matrix, and gets oxidized to CO2 while at the same time reducing NAD to NADH. NADH can be used by the electron transport chain to create further ATP as part of oxidative phosphorylation. The citric acid cycle is an 8-step process involving different enzymes and co-enzymes.

Steps3: KREBS CYCLE or TCA This is also called the citric acid or the tricarboxylic acid cycle Takes place in matrix of mitochondria Requires Oxygen (Aerobic) Each cycle produces 1 ATP, 3 NADH, and 1 FADH

The TCA or KREBS CYCLE 4 CO2 6NADH 2FADH 2 more ATP

NETS: 3NADH, 1ATP, 1FADH2, & 2CO2

The conversion of pyruvate and the Krebs cycle produces large quantities of electron carriers. • So what do you think the major purpose of the Krebs cycle is??

Electron Transport The mitochondria has two membranes the outer one and the inner membrane The H+ which are brought to mitochondria accumulate between these two membranes.

the electrons move from molecule to molecule until they combine with oxygen and hydrogen ions to form water. As they are passed along the chain, the energy carried by these electrons is stored in the mitochondrion in a form that can be used to synthesize ATP

Electrons carried by NADH are transferred to the first molecule in the electron transport chain The electrons continue along the chain that includes several cytochrome proteins and one lipid carrier. The electrons carried by FADH2 added to a later point in the chain. Electrons from NADH or FADH2 ultimately pass to oxygen. The electron transport chain generates no ATP directly.

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ONE GLUCOSE MOLECULE PRODUCES 38 ATP Each NADH 3 ATP Each FADH 2 ATP Glycolysis (2 NADH) 6 ATP Prep for Citric Acid 6 ATP Citric Acid (6 NADH) 18 ATP (2 FADH2) 4 ATP 34 ATP direct 4 ATP total 38 ATP

What happens when there is no oxygen to accept the electrons? If no oxygen is available, cells can obtain energy through the process of anaerobic respiration. A common anaerobic process is fermentation. Fermentation is not an efficient process and results in the formation of far fewer ATP molecules than aerobic respiration. There are two primary fermentation processes: Lactic Acid Fermentation Alcohol Fermentation

Fermentation allows the production of a small amount of ATP without oxygen.

Lactic acid fermentation occurs when oxygen is not available. For example, in muscle tissues during rapid and hard exercise, muscle cells may be depleted of oxygen. They then switch from respiration to fermentation.

The pyruvic acid formed during glycolysis is broken down to lactic acid and energy is released (which is used to form ATP). Glucose → Pyruvic acid → Lactic acid + energy

Lactic acid that builds up in the tissue causes a burning, painful sensation. results in muscle soreness

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Alcohol fermentation occurs in yeasts and some bacteria.

Alcohol Fermentation Pyruvate is converted to ethanol (ethyl alcohol) in 2 steps. 1. carbon dioxide is released from pyruvate, which is converted to acetaldehyde. 2. acetaldehyde is reduced by NADH to ethanol. Regenerating a supply of NAD+

Anaerobic Respiration Anaerobic respiration is respiration without oxygen; the process uses a respiratory electron transport chain but does not use oxygen as the electron acceptors Aerobic respiration uses oxygen Definition Produces lactic acid (in lactic acid fermentation but not in alcoholic fermentation) Does not produce lactic acid Production of lactic acid: Low (2 ATP molecules) High (36-38 ATP molecules) Amount of energy released: Lactic Acid Fermentation - lactic acid, ATP Alcoholic Fermentation - ethyl alcohol, ATP, carbon dioxide Carbon dioxide, water, ATP Products: glucose glucose, oxygen Reactants:

Copyright Cmassengale Anaerobic Aerobic Cytoplasm Cytoplasm and mitochondria Site of reactions: Glycolysis, fermentation Glycolysis, Krebs cycle, Electron Transport Chain Stages: Copyright Cmassengale

Copyright Cmassengale The aerobic system requires 60 to 80 seconds to produce energy for resynthesizing ATP from ADP + P.  The heart rate and respiratory rate must increase sufficiently to transport the required amount of O2 to the muscle cells, allowing glycogen to break down in the presence of oxygen. Copyright Cmassengale

Copyright Cmassengale the lactic acid system need 8 to 10 seconds to produce energy Copyright Cmassengale

Summary Quiz What are the reactants of aerobic respiration?? Products? Equation? List the three respiratory stages: Where in the cell do each occur? What are the products of each? How much ATP is produced by Anaerobic gylcolysis? Aerobic glycolysis? List the 2 types of fermentation??