Anaerobic and Aerobic Respiration Cellular Respiration Anaerobic and Aerobic Respiration

How it Works: Cellular Respiration is the energy-releasing chemical breakdown of glucose molecules and the storage of energy In living things the breakdown of glucose happens in two stages: Glycolysis – anaerobic stage Krebs cycle (citric acid cycle) and the electron transport chain – aerobic stage.

Anaerobic Respiration respiration in the absence of free oxygen occurs in the cytoplasm energy is ONLY produced by glycolysis final product is 2 ATP (energy) and an acid

Anaerobic Respiration 1. Glycolysis – the breaking of C6H12O6 into pyruvic acid Glucose enters the cytoplasm of the cell where 2 ATP of energy is used to break the 6-carbon sugar into two 3-carbon sugars The leftover P from ATP  ADP + P bonds to the 3-carbon sugar to make a PGAL The splitting of the glucose releases 4 ATP of energy, and makes 2 NADH The PGAL oxidizes to release a pair of electrons Results in two 3-carbon sugars called pyruvic acid or pyruvate (which can enter a mitochondrion) Net results of glycolysis: 2 ATP, 2 NADH, 2 pyruvic acids

Glycolysis Glucose (6-C) + 2ATP + 2NAD+ → 2 Pyruvic Acid (2 x 3-C) + 2NADH + 4ATP At this stage the pyruvic acid can follow one of several pathways. Two pathways are anaerobic (without oxygen) and the other is aerobic) The anaerobic pathways are inefficient in terms of energy released but can be important for the organism if it needs energy when there is a shortage or absence of oxygen. This anaerobic respiration is called fermentation.

Fermentation - The metabolism of pyruvic acid during fermentation does not produce any ATP. The function of fermentation is to break down pyruvic acid and regenerate NAD+ for reuse in glycolysis. the two pyruvic acids each accept a hydrogen from NADH -this forms the final products which are an acid and carbon dioxide -the NAD+ molecule is left to be reused so that glycolysis can continue.

Fermentation There are two types of fermentation which can be identified by their waste product: 1. Alcoholic Fermentation Is the process that occurs in some plant cells and some unicellular organisms, such as yeasts. Pyruvic acid is converted to ethanol. Pyruvic Acid + NADH → Ethanol + CO2 + NAD+ 2. Lactic Acid Fermentation Occurs in animal cells and in some unicellular organisms when oxygen is in short supply. Latic acid forms when pyruvic acid accepts hydrogen from NADH: Pyruvic Acid + NADH → Lactic Acid + NAD+ Lactic acid shuts down muscle function very quickly. It is the feeling of muscle soreness after heavy exertion. After shoveling snow, lifting weights, sprinting, our muscles need to recover. We can't force enough oxygen into those large muscles to satisfy their needs. Our recovery is called satisfying our oxygen debt.

Aerobic Respiration respiration in the presence of oxygen Begins in the cytoplasm with glycolysis, both the Kreb’s Cycle and the Electron Transport Chain are in the mitochondria final products are carbon dioxide, water, and 36 ATP (energy)   Remember: glycolysis produces 2 pyruvic acid molecules, which enter the mitochondria.

Aerobic Respiration 1. Glycolysis – the breaking of C6H12O6 into pyruvic acid Glucose enters the cytoplasm of the cell where 2 ATP of energy is used to break the 6-carbon sugar into two 3-carbon sugars The leftover P from ATP  ADP + P bonds to the 3-carbon sugar to make a PGAL The splitting of the glucose releases 4 ATP of energy, and makes 2 NADH The PGAL oxidizes to release a pair of electrons Results in two 3-carbon sugars called pyruvic acid or pyruvate (which can enter a mitochondrion) Net results of glycolysis: 2 ATP, 2 NADH, 2 pyruvic acids

2. Kreb’s Cycle -the pyruvic acids enters the mitochondria -both of the 3-carbon pyruvic acids are converted into 2- carbon acetic acid molecules; the 3rd carbon and the oxygens it is bonded to are released as the carbon dioxide waste product (CO2) -both acetic acid molecules bond to a coenzyme A (coA), which makes acetylCoA -both acetylCoA’s enter the Kreb’s Cycle, and goes through the cycle twice - each turn of the cycle produces 3NADH, 1FADH2, 1 ATP, and 2 more carbon dioxide molecules -therefore, for each ORIGINAL glucose molecule 6NADH, 2 FADH2, 2 ATP are made

3. Electron Transport Chain -Takes place in the matrix of the mitochondrion -the NADH and FADH2 molecules produced in the Kreb’s Cycle are transported to the matrix of the mitochondrion, where they release electrons onto a series of molecules along the inner membrane -H+ molecules are also removed from the NADH and FADH2 molecules, causing an imbalance of charges along the membrane and additional energy to be released -these H+ molecules bond to oxygen molecules in the mitochondria and water (H2O) is released as a waste product -for each NADH molecule 3 ATP are produced, and for each FADH2 molecule 2 ATP are produced -in total, 32 ATP of energy are produced for the cell to use!

In Aerobic Respiration 1 Molecule of Glucose Produces 6 H2O as a waste product 6 CO2 as a waste product 36 ATP of energy 2 from Glycolysis + 2 from Kreb’s + 32 from ETC

Aerobic Respiration Chemical Reaction Sugar + Oxygen  Carbon dioxide + water +Energy C6H12O6 + 6O2  6CO2 + 6H2O + 36ATP

What are the products of glycolysis? 1. Lactic acid in plants 2. Ethanol in animals 3. ATP and NADH

What are the products of glycolysis? 1. Lactic acid in plants 2. Ethanol in animals 3. ATP and NADH

Why must pyruvic acid be oxidized during fermentation in anaerobic respiration? 1. Its pH is dangerous to living cells 2. It has a negative charge and must be neutralized 3. More energy can be released to the cells if it ferments

Why must pyruvic acid be oxidized during fermentation in anaerobic respiration? 1. Its pH is dangerous to living cells 2. It has a negative charge and must be neutralized 3. More energy can be released to the cells if it ferments

What is produced during Kreb’s cycle? 1. Carbon dioxide 2. Hydrogen acceptors and electron carriers 3. ATP 4. All of the above

What is produced during Kreb’s cycle? 1. Carbon dioxide 2. Hydrogen acceptors and electron carriers 3. ATP 4. All of the above

Why is the electron transport chain an essential part of respiration? 1. It releases water molecules 2. It converts the stored H+ and e- into ATP

Why is the electron transport chain an essential part of respiration? 1. It releases water molecules 2. It converts the stored H+ and e- into ATP