Clothespins and Muscle Fatigue Introduction Automobiles and machines

Clothespins and Muscle Fatigue Introduction: Automobiles and machines must be supplied with gasoline or electricity as a source of energy before they can move. Your muscles require energy in the form of ATP to contract. Muscles can produce ATP by using oxygen (aerobic respiration) or not using it (anaerobic respiration). Anaerobic respiration in muscle cells produces lactic acid. When muscles do a lot of work quickly, the buildup of lactic acid reduces their ability to contract until exhaustion eventually sets in and contraction stops altogether. This is called muscle fatigue.

Materials: clothespin, timer Procedure: • Hold a clothespin in the thumb and index finger of your dominant hand. • Count the number of times you can open and close the clothespin in a 20 -s period while holding the other fingers of the hand straight out. Make sure to squeeze quickly and completely to get the maximum number of squeezes for each trial. • Repeat this process for nine more 20 -s periods, recording the result for each trial in a suitable. Do not rest your fingers between trials. • Repeat the procedure for the non-dominant hand.

Right Hand Trial 1 Trial 2 Trial 3 Etc…. Left Hand Trial 1 Trial 2 Trial 3 Etc…. Number of squeezes Sample table: Questions: • Prepare a suitable graph of the data you collected. • What happened to your strength as you progressed through each trial? • Describe how your hand fingers felt during the end of your trials. • What factors might cause you to get more squeezes (to have less fatigue)? • Were your results different for the dominant and the nondominant hand? Explain why they would be different. • Your muscles would probably recover after 10 min of rest to operate at the original squeeze rate. Explain why.

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Cellular respiration 8 -year-old Sarah suddenly felt pins and needles in the muscles of her legs as she walked. Within a year, she couldn’t walk without experiencing muscle pain, shortness of breath, and a racing heart. When Sarah engaged in light physical activity, her muscles generated as much lactic acid as would normally be produced during prolonged strenuous exercise. The lactic acid buildup was responsible for the muscle pain, but why was it accumulating abnormally? Sarah’s problem was narrowed down to her energy production system. But where? The trouble could lie within one of the three components of cellular respiration: glycolysis, the Krebs cycle, or the electron transport system? ? ?

Cellular respiration Biochemists traced Sarah’s problem to the electron transport system in her mitochondria. This chain of proteins allows for the efficient production of ATP, and in Sarah’s case, one of the proteins, cytochrome a 3, was defective. Her muscles could not make sufficient amounts of ATP and, instead, produced excess lactic acid. Observations showed that Sarah’s muscle cells had produced huge numbers of mitochondria to make up for the low energy yield.

Cellular respiration Researchers found a substitute for the faulty protein: a simple mixture of vitamin C and a modified form of vitamin K. Sarah began feeling better almost instantly. By the age of 20, she no longer used a wheelchair and was completely free of symptoms. The mixture did not cure Sarah’s it simply filled the gap caused by the defective protein. Without a team of investigators who understood cellular respiration, she would have been denied the opportunity to lead a normal life.

Cellular respiration We are going to start by focusing on how to get energy from glucose…. Photoautotrophs – make glucose from sunlight (photosynthesis) Heterotrophs – get glucose from eating photoautotrophs or heterotrophs.

REDOX Reactions revisited….

Cellular respiration Cells have developed several different mechanisms to extract the energy they need from available nutrients. In each case, redox reactions are involved. In one method, the redox reactions result in the transfer of electrons from glucose to oxygen. Glucose is oxidized to carbon dioxide and oxygen is reduced to water. The overall reaction is as follows: C 6 H 12 O 6 (aq) + 6 O 2(g) 6 CO 2(g) + 6 H 2 O (l) + energy via heat and ATP

Cellular respiration Aerobic respiration is accomplished through a series of about 20 reactions in which the product of one reaction is the reactant of the next, with each step catalyzed by a specific enzyme. Definition of aerobic : aer·o·bic/əˈrōbik/ Adjective: Relating to, involving, or requiring free oxygen: "simple aerobic bacteria". Relating to or denoting exercise that improves the efficiency of the body's cardiovascular system in absorbing and transporting oxygen.

Cellular respiration The overall equation for aerobic respiration tells us that 12 hydrogen atoms break away from glucose and attach to six oxygen atoms from the six oxygen (O 2) molecules to become six water (H 2 O) molecules. This is called oxidation because hydrogen atoms carry electrons away from carbon atoms in glucose to oxygen atoms.

Cellular respiration When the hydrogen atoms form covalent bonds with oxygen, the shared electron pairs occupy positions closer to the oxygen nuclei than they did when they were part of the glucose molecule. This happens because oxygen is much more electronegative than carbon. An electron occupying an energy level closer to a nucleus is equivalent to a skydiver occupying a position closer to the ground—both possess less free energy. The decrease in potential energy coupled with an increase in entropy causes a decrease in free energy and an overall exergonic process.

Cellular respiration This change also constitutes an oxidation because, once bound to carbon atoms, the highly electronegative oxygen atoms draw the shared electron pairs to themselves. This results in a change that is considered equivalent to carbon losing electrons

Cellular respiration In a living cell, the free energy released from the combustion of glucose would also dissipate as heat and light, but cells have evolved methods to trap some of the energy (about 34% of it). By moving the positions of electrons in certain molecules to higher free energy states (such as in ATP).

Cellular respiration Activation energy prevents spontaneous combustion and allows living things to control the oxidation process. Specific enzymes catalyze every step in the aerobic respiration process. They lower the activation energy and allow the reactions to occur at a rate that is consistent with the needs of the cell.

Cellular respiration Oxygen is not the only possible electron acceptor in the oxidation of glucose in a cell. Some microorganisms use NO 2, SO 4, CO 2, and even Fe 3 as final electron acceptors. These organisms are known as obligate anaerobes and include such notable bacteria (and their associated disorders) as: Clostridium tetani (tetanus) Clostridium botulinum (food poisoning) Clostridium perfringens (gas gangrene).

Have you been paying attention? ? ? What is a photoautotroph? An organism that produces energy by photosynthesis What is the equation for cellular respiration for a heterotroph? C 6 H 12 O 6 (aq) + 6 O 2(g) 6 CO 2(g) + 6 H 2 O (l) + energy via heat and ATP What type of proteins are required for Aerobic respiration ? Enzymes What does OIL RIG stand for ? Oxidation is loss, reduction is gain

In cellular respiration is glucose oxidized or reduced? oxidized When the hydrogen atoms form covalent bonds with oxygen, the shared electron pairs occupy positions closer to the oxygen nuclei than they did when they were part of the glucose molecule. Why? ? Oxygen is more electronegative than carbon How much of the free energy released is actually traped by the cell? 34%

The first law of thermodynamics tells us that energy cannot be created or destroyed—it can only be changed from one form into another or transferred from one object to another. The ultimate goal is to capture as much of the available free energy as possible in the form of ATP. This goal is accomplished through two distinctly different energytransfer mechanisms called: 1. substrate-level phosphorylation 2. oxidative phosphorylation.

Substrate-level phosphorylation In substrate-level phosphorylation, ATP is formed directly in an enzyme-catalyzed reaction. In the process, a phosphate-containing compound transfers a phosphate group directly to ADP, forming ATP

Oxidative Phosphorylation ATP is formed indirectly. This process is oxidative because it involves a number of sequential redox reactions, with oxygen being the final electron acceptor. It yields many more ATP molecules for each glucose molecule processed.

Cellular respiration - homework Read pages 114 – 120. Answer “Learning check” 1 – 6. Write a paragraph that describes a coupled reaction.