B9 Respiration

• respiration is continuously occuring in living cells
• animals use their energy for building up larger molecules from smaller (e.g. amino acids into proteins), for muscular contraction and to maintain body temperature
• a combination of all the chemical processes that occur in living things to maintain life is called metabolism
• aerobic respiration takes place in the presence of oxygen when there is enough, it is the most efficient way to transfer energy from glucose and it takes place continuously in the sub cellular structure mitochondria
• photosynthesis equation is the opposite of the aerobic respiration equation
• anaerobic respiration takes place when there is not enough oxygen to carry out aerobic respiration and we do this only when we have to. we prefer no to use this because of the incomplete breakdown of the glucose molecule because there is no oxygen to oxidise it, making it less efficient. as well as lactic acid being produced which causes muscle fatigue and needs to be removed later
• anaerobic respiration in yeast is called fermentation, the equation is glucose --> ethanol + carbon dioxide. we add yeast to bred so that the carbon dioxide created makes small pockets or air which can make the bread rise and appear fluffier.
• the liver has many functions like detoxifying poisonous substances such as ethanol from alcoholic drinks, they pass the breakdown products into the blood so they can be excreted in the urine via the kidneys
• in the liver, the hepatic vein carries blood from the liver onto the heart with levels of food adjusted, the hepatic artery brings oxygenated blood from the from the lungs to the liver and the hepatic portal vein carries blood containing digested food from the intestines to the liver.
• all organisms need energy; we need energy for movement, humans and other mammals need energy to keep warm and we also need energy for chemical reactions to build larger molecules. e.g. proteins are made by chemically joining amino acids
• the energy we need is supplied by a process called cellular respiration. respiration is an exothermic reaction because it releases energy and it takes place continually in all living cells
• in aerobic respiration, the sugar glucose is reacted with the oxygen gas, this produces carbon dioxide and water while releasing energy. this releases a large amount of energy, because the glucose molecule has been fully oxidised
• aerobic respiration as formulas is C6H12O6 + O2 ----> CO2 + H2O
• if oxygen is present in sufficient amounts, cells will carry out aerobic respiration. if theres not oxygen, cells will carry out anaerobic respiration
• muscles need lots of energy to contract but under certain conditions the amount of oxygen is limited. when there is a shortage, muscle cells must respire anaerobically
• during anaerobic respiration, glucose is converted into lactic acid, while releasing energy. anaerobic respiration doesn't release anywhere near as much energy as aerobic respiration because the oxidation of glucose is incomplete
• anaerobic respiration can take place in plant and yeast cells. the equation is glucose ---> ethanol + carbon dioxide and energy
• anaerobic respiration in yeast cells is called fermentation and is very useful. we use this reaction to make alcoholic drinks like beer as well as bread. in bread the carbon dioxide produced by fermentation is useful as it creates bubble in the dough which is what causes it to rise
• when we exercise we need more energy, the body will react and aerobic respiration increases so we require more oxygen. this is why the breathing rate and volume increase. the heart rate also increases to pump oxygenated blood around the body
• when we exercise, sometimes not enough oxygen can be supplied to the muscles especially when exercising hard. at this point, anaerobic respiration takes place.
• the oxidation of glucose is incomplete in anaerobic respiration, leading to a build up of the chemical lactic acid. the lactic acid can cause the muscles to become fatigued which makes the muscles stop contracting as efficiently
• from the build up of lactic acid, the body has to remove it, creating oxygen debt
• lactic acid is transported out of the muscles by the blood where it is taken to the liver and converted back into glucose in a series of chemical reactions
• reacting and removing accumulated lactic acid requires oxygen. the oxygen debt is the extra amount of oxygen the body needs after exercise to deal with the lactic acid. that is why we continue breathing rapidly after finishing exercise
• the energy released by respiration is used by enzymes to synthesise new molecules in the cell
• metabolism is the sum of all chemical reactions in a cell or the body
• in plant cells, glucose can be converted into cellulose which strengthens the plant cell wall or can be converted into starch which is a storage form of glucose or can react with nitrate ions to produce amino acids which are used to synthesise proteins
• in humans and animals, glucose can either be used directly in respiration or converted into glycogen which is a storage form of glucose
• 1 molecule of glycerol can react with 3 molecules of fatty acids to form a lipid molecule which we find in the cell membrane
• humans don't need to eat a large amount of protein. excess protein is broken down into the chemical urea. urea is then excreted in the urine by the kidneys
• the liver filters the body's blood which is received from the hepatic artery (from the heart) and the hepatic portal vein brings (from the intestine). this delivery fills the liver with nutrients that it sorts, processes and stores
• the liver breaks carbohydrates down and converts them into sugars for the body to use as energy for when the filtered blood is sent back out through the hepatic vein and the inferior vena cava. if not all is sent out, the liver can store some sugars too.
• when toxins are in the blood and get to the liver, the liver either converts it into something harmless or isolates it and gives to kidneys and intestines to be excreted
• the liver produces bile which comes from toxic waste products. bile is sent through the gallbladder, then goes into the intestine. it carries toxic products out of the body.