INTRODUCTION TO BIOENERGETICS About this Unit Introduction

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1 INTRODUCTION TO BIOENERGETICS About this Unit Introduction - Exercise reduces the risk of all sorts of cancers. Fatigue is a symptom of cancer and that is improved by exercise. - Exercise improves mood, self-confidence, weight and metabolism. It can make a person go from an ordinary athlete towards becoming an elite athlete. - Cooling the body improves exercise performance. - Ergogenic aids - caffeine, sodium bicarbonate, sodium phosphate - all legal sporting aids. - This course is relevant to everyone. - Important information that will probably be examined word-for-word is in bold/red. Housekeeping - Main textbook - The Essentials of Exercise Physiology by McArdle, Katch and Katch. All of the examination questions come from the textbook. This book is essential. - A lot of the review questions are used in the examination. Do the review questions as you go, each week. - The first lab starts next week (Stream A). Stream B starts in Week 3 of Semester. The labs are every second week. You only have to come to four labs. They are usually done within 90 minutes. After the fourth lab, you are examined (in 15 minutes). You need to buy the lab manual - at the back is the examination for that practical examination. - Practical sessions begin on Wednesdays from Week 1-8 (Stream A); or on Wednesdays from Week 7-13 (Stream B). - There are no supplementary examinations for this unit. - This unit is easy if you come to the lectures. It is very important to attend all lectures and labs. Assessment - The mid-semester exam - lectures 1-12 = 35% - Mid-semester exam on 16 April at 11am in the lecture theatre. - The final exam - lectures 14+ and labs = 40% - Practical lab exam = 10% - Practical fitness = 15% Background Chemistry - Thousands of chemical reactions occur in the body every minute of the day that make you function. - Collectively, these reactions are called metabolism. - Generally, when you have a high metabolism, you have less of a problem with weight. People with slow metabolisms are often slower and heavier. - Metabolism involves the synthesis (creation) of molecules, as well as the breakdown of molecules. - A molecule is a combination of more than one atom. Matter is anything that occupies space and has weight. John Dalton ( ) discovered the atom - being indivisible and solid. This concept of the atom lasted a century. Ernest Rutherford ( ) was the first person to split the atom. Rutherford named the proton. In the nucleus are neutrons and protons. The number of protons in the nucleus will determine which element the atom is. Electrons orbit the nucleus. For every proton, there is a corresponding electron. It should in theory be neutrally charged. Energy Fields - There are a number of energy fields that surround the nucleus of an atom. - First field can hold 2 electrons; the second field can hold 8 electrons; and the third field can hold 8 electrons. - If the outer field is not full then an atom will attempt to fill the outermost field. For example, Na+ likes to bond with Cl- to make NaCl. Sodium and chlorine atoms combine to create a molecule (NaCl). Ions - If an atom gains an electron, it will acquire an overall negative charge. If an atom loses an electron, then it will acquire an overall positive charge. - An atom with a positive or negative charge is called an ion. - When we do a particular exercise, H+ is involved in the energy process. H will lose its electron to become H+. H+ causes pain. The burning sensation caused by exercise is caused by H+. - To have the energy to move, H became H+ by donating their electrons. Atoms - Atoms in molecules are held together by chemical bonds. Chemical bonding involves the donating, receiving or sharing of electrons between atoms. - Energy is needed to form these bonds - however when these bonds are broken energy is released. Metabolism = chemical reactions = the making or breaking of bonds between atoms. - There are 103 different atoms/elements in nature. Four of these make up ~95% of our body mass. The human body is composed of the following proportions of oxygen (65%), carbon (18%), hydrogen (10%) and nitrogen (3%). - Sodium, chlorine, iron, zinc, potassium, magnesium and calcium. - Molecules that contain carbon atoms are called organic. - Molecules that do not contain carbon atoms are inorganic.

2 - Compounds are the combination of two or more atoms. Cells - The union of two or more atoms forms a molecule. - This process occurs in a cell trillion cells are in the average human body. - Cells often have a membrane. It encloses the contents of the cell - a protective barrier. It regulates the passage of substances in and out of the cell. - The cell has a nucleus which contains the genetic material of the cell. - The cell has a cytoplasm which contains its organelles. - The mitochondria produce energy within the cell. - Enzymes are proteins that speed up cellular chemical reactions. A typical mitochondria may contain up to 10 billion types of enzymes. Hydrolase adds water to hydrolysis reactions. Protease interacts with protein. Oxidase adds oxygen to a substance. - Anabolism - the synthesis reactions. Catabolism - the breaking down of molecules. - Hydrolysis - when water is added to a complex organic molecule and the molecule is catabolised to two simpler molecules. - Sucrose water > Glucose + Fructose - Condensation - where water is lost - i.e. two simple glucose molecules lose a molecule of water to become a maltose unit. A water molecule is lost in this process. Enzymes - Impacted by: - Hydrogen ions - which affect the ph of the body. The body s ph affects the ability of enzymes to work. - Lower temperatures decrease enzyme activity and decrease metabolism. You sleep better when it is cold. - Enzymes work like a jigsaw. The structure of an enzyme is that it fits with a particular substrate in a lock and key mechanism. - The locking motion turns the enzyme on. The mechanism is called a lock and key mechanism. It means that only specific substrates can be activated by specific enzymes. When an enzyme joins a substrate, chemical bonds are broken, new bonds are formed and newly formed products are released. - Firstly, the active sites of the enzyme and substrate fit together. - Secondly, the enzyme catalyses the chemical reaction. - Thirdly, an end product is produced. - Finally, the enzyme is now free to start the process again. Coenzymes - A special class of enzymes are coenzymes that act as assistants to enzymes. The two important coenzymes are: - Nicotinamide adenine dinucleotide (NAD+) - Flavin adenine dinucleotide (FAD)

3 ENERGY SYSTEMS - Energy is the ability to do work. - Energy is provided by adenosine triphosphate (ATP). ATP supplies all energy for work in the body. - ATP is a very heavy molecule. There are only limited reserves of ATP in the body ( grams). ATP is used up and is constantly remade through respiration. It is remade from chemical energy. - Chemical energy is trapped within the bonds of the food that we eat. - When these bonds are broken, energy is released. - Some energy is used in order to rebuild ATP. - Some of this energy is lost as heat (~60%). - The rate at which chemical energy in food is extracted and used to make ATP depends on the intensity of the exercise. Food, Nutrients and Energy - Chemical energy comes from our food nutrients (macronutrients): - Carbohydrates (CHO) - generally anything grown will be a carbohydrate. - Lipids/fats - Protein - generally anything that has a mother.

4 FUNCTION AND STRUCTURE OF CARBOHYDRATES Energy - Energy is supplied in the body by ATP. It is an organic molecule. - ATP is a very heavy molecule. There are only limited reserves of ATP in the body (about grams at any one time). ATP is constantly remade from chemical energy trapped in our food. - Macronutrients have energy in them. Carbohydrates - Abbreviation for carbohydrates will be CHO. - CHO molecules are composed of carbon, hydrogen and oxygen. - There are numerous types of CHO molecules. The differences relate to the number of single sugar units linked within a molecular structure. - Monosaccharides is a basic unit of CHO - galactose, glucose and fructose are monosaccharides. - Oligosaccharides are 2-10 monosaccharides bound together. Disaccharides are a subcategory of Oligosaccharides with only 2 units. Examples include sucrose, lactose and maltose. - Polysaccharides describes the linkage of or more units. Examples include amylose (starch) and cellulose (fibre). - Names of CHO usually end with the suffix ose. - All CHO digested is ultimately converted to glucose which is a monosaccharide. A glucose molecule consists of C6H12O6. Determine your daily caloric intake - Calculate the following: - Your weight x 24 = A - Decide on your activity level: - Light A x 0.3 = B - Moderate A x 0.5 = B - High A x 0.7 = B - Combine A + B = recommended caloric intake. - This gives you an answer in kcal. To determine kj, multiply kcal by Individual variation is usually around 300 kcal. Kilojoules are the units used in Australia. - If a person consumes more kcal than the result of that equation, then they will put on weight. CHO - How much should be eaten? - Typical recommended dietary intake of CHO for non-athletes is 40-50% of total daily caloric intake. - For a sedentary 70kg person = about 300 grams of CHO daily. - For athletes, CHO intake should be approximately 60% of total daily caloric intake = grams daily. - Those involved in heavy training should consume 70% of total calories consumed per day (8-10 grams per kg of body mass). What happens when you ingest CHO? - All CHO that are ingested are converted into glucose. The glucose is carried in the blood to the body s tissues. The glucose is combined in the mitochondria with oxygen to create ATP. - Blood sugar levels are highly regulated in the body. The normal range is mmol/l. - If you don t have enough sugar you will become hypoglycaemic. - Any excess blood sugar is stored in the body as glycogen. It is stored in the muscles and the liver. Glycogen that has been stored in muscles has a different function to glycogen that has been stored in the liver. It has been stored for future use. Glycogen is the storage form of CHO. - What happens when you fill up your glycogen stores? The glycogen is converted to fat. If muscle and liver glycogen stores are full, then the excess blood glucose is converted to fat. Consider products that are 97% fat free. Portion size is the most important factor. CHO Stores in the Body - In a well nourished 80kg person, CHO stores are about 500 grams. Of the 500 grams, 400 grams will be stored as muscle glycogen grams will be stored as liver glycogen and 5 grams will be flowing in the blood. - Each gram of CHO contains 4.15 kcal's of energy (roughly 17 kilojoules). - Therefore, the average person stores roughly kcal's ( kj) as CHO. - This is enough fuel for 1.5 hours of moderate paced running before muscle glycogen runs out. Running out of muscle glycogen is the feeling you get when you hit a wall during a run. The process of converting glucose to glycogen - Glycogenesis 1. Blood glucose is converted to glucose 6-phosphate. 2. Glucose 6-phosphate is converted to glucose 1-phosphate. 3. Glucose 1-phosphate is converted to Uridine diphosphate (UDP) glucose. 4. UDP glucose joins with an existing glycogen polymer chain.

5 Functions of CHO CHO serve four important functions related to energy metabolism and exercise: 1. Energy source - CHO and fats are the main energy sources for the human body. CHO (glucose and glycogen) serves as the main fuel for the body during high intensity exercise. Daily CHO intake must be adequate to maintain the body s glycogen stores. 2. Protein sparing - protein serves a vital role in tissue maintenance, repair and growth. Protein can be used as a fuel. Protein is used as a fuel when nutritional status is poor, during prolonged exercise (hours). Protein is converted to glucose = gluconeogenesis. Reduction in protein stores under extreme conditions will lead to a significant decrease in muscle mass, which lowers metabolism. Adequate CHO intake helps to preserve protein in the body. 3. CHO is a metabolic primer. Fat cannot be burned unless CHO is present. Adequate CHO must be available in order for lipid breakdown to occur. Limited stores of CHO will result in incomplete lipid breakdown, which leads to the accumulation of by-products called ketone bodies, which are harmful. As a result, exercise performance is impaired. Fat burns in a CHO flame. 4. CHO is a fuel for the Central Nervous System. CHO is essential for the proper functioning of the CNS. The brain uses glucose almost exclusively as its fuel. You should never sit an exam or physical assessment without having breakfast. Prolonged heavy exercise (i.e. marathons) can result in low levels of blood glucose. Blood glucose that drops below 2.7 mmol/l leads to hypoglycaemia. This can result in feelings of weakness, hunger and dizziness. That leads to fatigue and may impair performance. Sustained and profound low blood sugar levels can cause a loss of consciousness, coma and irreversible brain damage. CHO as a fuel for exercise - Muscle glycogen is the major fuel used by active muscles during: high intensity exercise; and at the start of exercise. - Blood glucose will also play a role in providing energy during exercise. - Liver glycogen will only convert to blood glucose when blood glucose levels drop too low. Glycogenolysis is the process of liver glycogen being converted into glucose. - If liver and muscle glycogen supplies are low, due to dietary restrictions or prolonged exercise then protein will be converted into glucose in a process called gluconeogenesis hours of not having enough CHO will severely impact on your CHO stores. - The amount of glycogen stored in the body is dependant on CHO intake in your diet. - The body s glycogen stores can fluctuate considerably. A 24 hour fast or a low CHO diet can severely deplete glycogen stores. - Maintaining a CHO rich diet for several days nearly doubles the body s CHO stores. - Research has shown that a carbohydrate-rich diet improves sporting performance. Super-compensation - In Maughan (1960) it was shown that there was a good relationship between pre-exercise muscle glycogen content and performance. This led to the idea of super-compensation. Exercise duration needs to exceed minutes for the benefits to be seen. The more muscle glycogen that we have in our body, the longer we last during prolonged physical exercise. Super-compensation was the technique whereby an athlete, at 6 days from an event, would cut their CHO intake for three days, while still exercising. This would deplete their CHO stores. Then, for the last four days, the athlete eats more CHO. The CHO storage in the body increased. - CHO loading can increase time to exhaustion by 20%. - There can be problems with super-compensation. Each gram of glycogen stores 2.7 grams of water which can lead you to feel heavy. Secondly, training is really difficult during the periods where you have low CHO intake. Depleting CHO stores leads to fatigue, which can affect training. - Eating a high CHO diet (super-compensation) should be a temporary measure only. It is used for preparing to participate for an endurance event. Effects of Diet on Endurance Performance - The following study emphasises the importance of diet on performance. Participants were on a bike. - Trial 1 - caloric intake for 3 days was normal, however the majority of calories came from fats. - Glycogen content of the quadriceps was 0.63 grams per 100 grams wet mass minutes of cycling was sustained. - Trial 2 - caloric intake for 3 days was normal, however the recommended daily intake of CHO, lipids and protein were followed. - Glycogen content of the quadriceps was 1.75 grams per 100 grams wet mass minutes of cycling was sustained. - Trial 3 - caloric intake for 3 days was normal, but consisted mainly of CHO (83%). - Glycogen content of the quadriceps was 3.75 grams per 100 grams wet mass minutes of cycling was sustained. - A person on a low CHO diet will be unable to replenish their muscle glycogen - therefore, over consecutive training sessions, their performance will decrease dramatically. Swedish Soccer Team Study