Cellular Respiration 4.3

Photosynthesis- the process of absorbing light energy and converting it into stored chemical energy. Chemical equation: Cellular Respiration- the breaking down of a food substance into usable cellular energy in the form of ATP Chemical equation: Cellular respiration is the opposite of photosynthesis: Photosynthesis combines water, carbon dioxide and light energy to form glucose, and oxygen is a waste product. Cellular respiration uses oxygen to help break down glucose to form ATP, and water and carbon dioxide are waste products. The reactants of photosynthesis are the products of cellular respiration and the reactants of cellular respiration are the products of photosynthesis. In photosynthesis light energy is stored in glucose as chemical energy so it is endergonic. In cellular respiration energy is released from glucose so it is exergonic.

 Plants, algae, and some bacteria can undergo photosynthesis and produce their own food, but they still have to undergo cellular respiration to make ATP before they can use the energy.

Cellular Respiration Cellular respiration ~ the breaking down of a food substance into usable cellular energy in the form of ATP. Two types: 1.Aerobic cellular respiration  requires oxygen  most common  produces more ATP per glucose molecule 2.Anaerobic respiration (fermentation)  does not require oxygen  sometimes used by certain cells if oxygen is not available, some bacteria and fungi only use anaerobic respiration  produces less ATP per glucose molecule

Aerobic Cellular Respiration 1.Glycolysis 2.Oxidation of pyruvate 3.Kreb’s Cycle (Citric Acid Cycle) 4.Oxidative Phosphorylation

Aerobic Cell Respiration 1. Glycolysis Occurs in the cytoplasm of the cell Glucose is converted to 2 pyruvate or pyruvic acid molecules – Net of 2 ATP 4 ATP are produced but 2 are used – 2 NADH (electron carrier)

Aerobic Cellular Respiration 2. Oxidation of Pyruvate Occurs in the matrix of the mitochondria Each pyruvate molecule is converted into an acetyl-coenzyme A (acetyl-CoA) molecule – 2 NADH – 2 CO 2

Aerobic Cellular Respiration 3. Kreb’s Cycle (Citric Acid Cycle) Occurs in the matrix of the mitochondria Each acetyl-CoA molecule combines with an oxaloacetic acid molecule – 2 ATP – 6 NADH – 4 CO 2 – 2 FADH 2 (electron carrier)

Aerobic Cellular Respiration 4. Oxidative Phosphorylation NADH and FADH 2 pass electrons to an electron transport chain in the inner mitochondrial membrane. As electrons are passed along the electron transport chain, energy is slowly released which is used to make ATP through the process of chemiosmosis. The final electron acceptor is oxygen. Oxygen accepts 2 electrons and 2 hydrogen ion (H + ) to form water.  Chemiosmosis- Hydrogen ions are actively transported across the inner mitochondrial membrane to create a high concentration. Then they diffuse through ATP synthase from high concentration to low concentration and ATP synthase synthesizes ATP.  Oxidative phosphorylation produces around 32 ATP per glucose

Oxidative Phosphorylation Diagram

Aerobic cellular respiration converts 50%-60% of the energy contained in glucose into ATP. This is one of the most efficient energy processes known. Cars use only about 20% of the energy available from the fuel.

Energy Losses in a Vehicle Only about 15 percent of the energy from the fuel you put in your tank gets used to move your car down the road or run useful accessories, such as air conditioning. The rest of the energy is lost to engine and driveline inefficiencies and idling. Therefore, the potential to improve fuel efficiency with advanced technologies is enormous. Engine Losses percent Idling Losses percent Accessories percent Driveline Losses percent Aerodynamic Drag percent Rolling Resistance percent Overcoming Inertia; Braking Losses percent Source:

Anaerobic Cellular Respiration Aka fermentation Two types: alcoholic fermentation and lactic acid fermentation Both types begin with glycolysis just like in aerobic cellular respiartion

Anaerobic Cell Respiration 1) Glycolysis Occurs in the cytoplasm of the cell Glucose is converted to 2 pyruvate or pyruvic acid molecules – Net of 2 ATP 4 ATP are produced but 2 are used – 2 NADH (electron carrier)

Anaerobic Cellular Respiration 2) Two types – Alcoholic fermentation- conversion of pyruvate produces carbon dioxide and ethyl alcohol and regenerates NAD+ – Lactic acid fermentation- conversion of pyruvate produces lactic acid and regenerates NAD+

Anaerobic Cellular Respiration Lactic Acid Fermentation – Occurs in muscle cells when oxygen is not available – Certain bacteria are used to make cheese and yogurt Alcoholic Fermentation – Occurs in yeast cells (single celled fungi) when oxygen is not available and causes dough to rise

Figure 6.13A 2 NAD  2 NADH 2 NAD  2 NADH 2 Lactate 2 Pyruvate Glucose 2 ADP 2 ATP 2 P Glycolysis

Figure 6.13B 2 NAD  2 NADH 2 NAD  2 NADH 2 Ethanol 2 Pyruvate Glucose 2 ADP 2 ATP 2 P Glycolysis 2 CO 2

Respiration and Cellular Respiration Respiration is commonly thought of as breathing. Your body must bring in oxygen and release carbon dioxide. Your respiratory system allows you to bring in oxygen and release carbon dioxide, and your circulatory system transports those gases to and from body tissues. In your body tissues you need oxygen so cell respiration can occur and food substances can be broken down into usable cellular energy in the form of ATP. Cell respiration produces carbon dioxide, which is a waste product and must be expelled from the body.