Biology-1406 Chapter-7 Cellular Respiration
Energy is stored in Chemicals Catabolism- the breaking down of complex molecules, such as glucose, to release their stored energy. Catabolism may or may not require oxygen. Fermentation and anaerobic respiration does not require oxygen. Cellular or aerobic respiration does require oxygen.
External Respiration Inspired air contains 21% oxygen Inspired air contains.04 % Carbon dioxide Inspired air contains 78% Nitrogen Inspired air contains.96% of other gases such as argon. Expired air contains 16.42% oxygen 4.62% Carbon dioxide 78% Nitrogen.96% other gases
Internal Respiration Internal Respiration- the production of ATP in the mitochondria of the cell by the consumption of oxygen and the breakdown of glucose
Internal Respiration C 6 H 12 O 6 + O 2 > CO 2 +H2 0 +32 ATP +Heat 1 mole of glucose contains 686 Kilocalories of energy. 32 ATP s contains 233.6 Kilocalories of energy. Where did the remaining energy in the glucose molecule go?
34% converted to ATP 66% lost as heat (entropy) Why? The second law of thermodynamics states- that in every energy transfer or transformation lots of energy is lost as heat (Entropy-wasted,unusable energy)
What do we use ATP for? Mechanical workcontraction of your muscles so you can move. Electrical work- beating of your heart or conduction of nerve impulses. Transport work-active transport Chemical workcatabolism and anabolism.
Oxidation and Reduction Oxidation Adds oxygen Removes hydrogen Removes electrons Liberates energy Reduction Removes oxygen Adds hydrogen Adds electrons Stores energy
Examples of Oxidation and Reduction Xe- + Y >>>> X + Ye- Since X has lost its electron it has been oxidized Since Y has gained an electron it has been reduced When Na combines with Cl to form NaCl sodium loses an electron (oxidation) and chlorine gains an electron (reduction)
Internal Cellular Respiration The energy stored in glucose is not released all at once, otherwise you would burn up. So the energy in glucose is released a little at a time by the process of internal cellular respiration Internal respiration is divided into 4 steps. Glycolysis- which occurs in the cytoplasm Pyruvate Oxidation occurs in the mitochondria Citric Acid Cycle- occurs in the mitochondria Oxidative Phosphorylation which consists of (a) the electron transport chain and (b) chemiosmosis) This step also occurs in the mitochondria.
Overview of Aerobic Cellular Respiration 1. Glycolysis>>2ATP, 2NADH, 2Pyruvate Glucose Oxygen 2. Pyruvate Oxidation>> 2NADH, 2 Acetyl CoA 3. Citric Acid Cycle >>2ATP, 6NADH, 2FADH 2 4. Oxidative Phosphorylation >> 28ATP (a) Electron transport chain (b) Chemiosmosis Cell
Lets examine each of the 4 steps Step 1: Glycolysis (page 147 text)
Step 2. Pyruvate Oxidation (page 148 text)
Step 3. Citric Acid Cycle (page 149 text)
Step 4. Oxidative Phosphorylation (a) Electron Transport chain (b) Chemiosmosis) Page 152 text
Whenever you see this: ATP>>ADP+P That means ATP is being used This is an exergonic reaction
Whenever you see this: ADP + P>>ATP That means ATP is being made When ADP picks up a phosphate from another compound we call this: substrate level phosphorylation This is an endergonic reaction
Energy Storing Molecules NADH = Nicotinamide adenine dinucleotide FADH 2 = Flavin adenine dinucleotide
The electron transport chain FMN = Flavin mononucleotide Fe.S = Iron sulfur protein Q = Ubiquinone Cyt = Cytochromes
NADH and FADH 2 For every molecule of NADH that enters the electron transport chain 2.5 molecules of ATP are produced. For every molecule of FADH 2 that enters the electron transport chain 1.5 molecules of ATP are formed.
Chemiosmosis A process of ATP generation that occurs in the mitochondria. The movement of electrons down the electron transport system is used to pump hydrogen ions across a membrane, thereby building up a concentration gradient of hydrogen ions across the membrane; the hydrogen ions diffuse back across the membrane through the pores of ATP synthesizing enzymes; the energy of their movement down their concentration gradient drives the endergonic reaction: ADP + P>>>> ATP
Respiratory Blocks of the Electron Transport System
Respiratory Blocks of the Electron Transport System Cyanide- inhibits the ET system by binding with the cytochromes. Other Poisons inhibit ATP synthases or interfere with the flow of H + Vitamin B and iron- if you are deficient in these you will not produce as much NAD and FAD and cytochromes. Oxygen deprivation- drowning or smothering. Remember oxygen is the final electron acceptor in the ET system. Carbon monoxide poisoning- CO will combine with your RBC s very quickly. Now due to lack of oxygen your cells will die.
Fermentation (does not require O 2 ) Fermentation- reactions that convert the pyruvic acid produced by glycolysis into lactic acid or alcohol and carbon dioxide. There are two types: Alcohol Fermentation- carried out by yeast and some bacteria. Lactic Acid Fermentation- occurs in your muscles when oxygen is low due to vigorous exercise. Bacteria and Fungi can also carry out lactic acid fermentation
Glucose is not the only source of energy Proteins and Fats can also provide us with energy. Carbohydrates and proteins can also be converted to fat by Anabolic reactions So, even though we may consume less fat in our diet we can still get fat if we consume excess carbohydrates and proteins. It s the total # of excess calories we take in that causes us to gain weight.
Cellular Respiration Obeys the First Law of Thermodynamics According to the first law of thermodynamics energy is neither created or destroyed. The total amount of energy in the universe remains constant Therefore: The energy that keeps you alive is Released not Created by cellular respiration