Cellular Respiration Cellular Respiration All living things need

Cellular Respiration

Cellular Respiration All living things need energy l Energy in the form of… l l. Food=chemical energy l 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), l The reactions involved in respiration are catabolic reactions, which break large molecules into smaller ones, releasing energy l

Cellular Respiration l Includes pathways that require oxygen and other don't need oxygen l Breakdown of one glucose molecule produces 38 ATP molecules

Overall Equation for Cellular Respiration C 6 H 12 O 6 + 6 O 2 YIELDS 6 CO 2 + 6 H 20 + 38 ATP’s

Important Molecules in Cellular Respiration l CO 2 – l ATP Carbon Dioxide – Adenine triphosphate l NAD – Nicotinamide adenine dinucleotide l FAD – Flavin adenine dinucleotide

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

Where Does Cellular Respiration Take Place? l 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 l Glycolysis is takes place in the cytosol of cells in all living organisms. l This pathway can function with or without the presence of oxygen. l process converts one molecule of glucose into two molecules of pyruvate (pyruvic acid), l

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

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Glycolysis Summary l Produces molecules 2 NADH and 4 ATP • (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 Co. A which enters the Krebs cycle in the matrix. 2. A carboxyl group is removed as CO 2. 3. A pair of electrons is transferred from the to NAD+ to form NADH

l 2 molecule of pyruvate produce 2 NADH

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

l inside the mitochondrial matrix, and gets oxidized to CO 2 l while at the same time reducing NAD to NADH. l NADH can be used by the electron transport chain to create further ATP as part of oxidative phosphorylation. l The citric acid cycle is an 8 -step process involving different enzymes and co-enzymes.

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

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

NETS: 3 NADH, 1 ATP, 1 FADH 2, & 2 CO 2

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 l The H+ which are brought to mitochondria accumulate between these two membranes. l

l the electrons move from molecule to molecule until they combine with oxygen and hydrogen ions to form water. l 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

1. 2. 3. 4. 5. 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 FADH 2 added to a later point in the chain. Electrons from NADH or FADH 2 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) • Prep for Citric Acid • Citric Acid (6 NADH) • (2 FADH 2) • • direct • total 6 ATP 18 ATP 4 ATP 34 ATP 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: 1. Lactic Acid Fermentation 2. 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 q occurs in yeasts and some bacteria q The most famous yeast is bakers yeast called saccharomyces

Alcohol Fermentation l 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+

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

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

The aerobic system requires 60 to 80 seconds to produce energy for resynthesizing ATP from ADP + P. l The heart rate and respiratory rate must increase sufficiently to transport the required amount of O 2 to the muscle cells, allowing glycogen to break down in the presence of oxygen. l

l the lactic acid system need 8 to 10 seconds to produce energy

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