UNIVERSITI TEKNOLOGI MARA INTERNATIONAL EDUCATION COLLEGE (INTEC) NAME GROUP STUDENT ID TITLE OF PRACTICAL :HANNAH CHEN YEE SZE :12M12 :2011219506 :MEASURING THE RATE OF OXYGEN UPTAKE USING A RESPIROMETER DATE LECTURER :3/10/2012 :MS FATHIAH Introduction: In this process. Organic substances like carbohydrates. muscle contraction which enables locomotion. . Each molecule of triose phosphate will result in a pyruvate. the 6-carbon glucose is phosphorylated by using two molecules of ATP. Each molecule of triose phosphate will be oxidised by nicotiamide adenine dinucleotide (NAD). active transport of biochemical substances. proteins and enzymes. hormones. There are two types of respiration. lipids and proteins contain chemical energy which enters living organisms in the form of food and in order to be converted into a form of energy which can be readily used by cells. Then. There are many complicated steps involved in respiration. respiration is carried out. It is a redox reaction and its equation is as shown below. Aerobic respiration takes place in the cells of living organisms to convert chemical energy from food into energy in the form of ATP. the phosphorylated 6-carbon molecules will then be split into two carbon triose phosphate called glyceraldehyde-3-phosphate. cell division in which new cells are produced for growth and development. amino acids and fatty acids can be used as substrates too. Two molecules of ATP are also produced. maintaining the body temperature in warm-blooded animals) and synthesis of lipids. C6H12O6 + O2 CO2 + H2O + energy The main substrate for respiration is glucose. The net gain of ATP from glycolysis is two molecules. When glucose is not available. This production of ATP is known as substrate level phosphorylation. transmission of nerve impulses.Living organisms require energy for various activities and living processes. This activates the glucose and prevents glucose from being transported across the cell membrane. The first stage of respiration is glycolysis. which are all controlled by enzymes. absorption of digested food through active transport.aerobic respiration and anaerobic respiration. Some of the processes which require energy are excretion of waste products. which is also known as the citric acid cycle. . the pyruvate will enter the link reaction and this process requires oxygen. Pyruvate is decarboxylated to form a molecule of carbon dioxide. Pyruvate becomes acetate which combines with coenzyme A to form acetyl coenzyme A (acetyl coA).Diagram 1: Glycolysis Next. This will proceed to the Krebs Cycle. It is also dehydrogenated to form a molecule of reduced NAD. hence the name Kreb’s cycle. As the electrons pass from carriers to carriers. forming one molecule of carbon dioxide and one molecule of reduced NAD. It will form a five-carbon molecule known as alpha-ketoglutarate.Diagram 2: Link Reaction and Krebs Cycle Acetyl coA will combine with a four-carbon molecule called oxaloacetate to form citrate. The hydrogen acceptors (reduced NAD and reduced FAD) will enter the electron transport chain (ETC) to be oxidised. Coenzyme A will then be released and recycled in the next link reaction. two molecules of reduced NAD and one molecule of reduced flavine adenine dinucleotide (FAD). This forms a cycle. and then undergo three times of dehydrogenation to form one molecule of ATP. Citrate is decarboxylated and dehydrogenated. a six-carbon molecule. one molecule of carbon dioxide. energy is released in the form of ATP . dephosphorylated. Alpha-ketoglutarate itself becomes oxaloacetate which combines with acetyl coA. decarboxylated. The ATP-ase on these pores are used to drive the synthesis of ATP and 38 ATP are gained. but pyruvate will not enter the link reaction but undergo anaerobic respiration. The pH gradient . concentration gradient and electrochemical gradient that exist between the intermembrane space and the matrix of the mitochondria causes the protons to move back into the matrix via special pores found on stalked particles. he said that protons were actively transported into the intermembrane space using energy provided by the electrons as electrons are passed down the electron transport chain. No carbon dioxide is produced. this is known as alcoholic fermentation. Anaerobic respiration is carried out when oxygen is absent. The product is lactic acid and only two molecules of ATP. it is known as lactic acid fermentation. Glycolysis is still carried out. It is much less efficient compared to aerobic respiration because only two molecules of ATP are formed in contrast to the 38 molecules of ATP formed by aerobic respiration. where else in animals. In plants.Diagram 3: Electron Transport Chain In the chemiosmotic theory by Peter Mitchell. . The protons cannot diffuse the inner membranes as they are impermeable to protons. This shows that oxygen is very important as the final electron acceptor which allows the Krebs cycle and electron transport chain to work. Yeasts are eukaryotic microorganisms from the kingdom Fungi. Diagram 4: Yeast . They usually reproduce asexually by a process called budding. They are also facultative anaerobes. which means they can respire both aerobically and anaerobically. as they use organic compounds as a source of energy and do not require sunlight to grow. They are unicellular and their size varies depending on the species. Yeasts are chemoorganotrophs. usually ranging between 3-4µm in diameter. 1cm3 syringe. gauze. Null hypothesis: The respiration rate cannot be measured by the means of a respirometer by calculating the uptake of oxygen per unit time. delivery tubes.Objective: To investigate the rate of oxygen uptake of yeast using a respirometer. filter paper. three-way tap. red dye. cling film . potassium hydroxide solution. Problem Statement: What is the rate of oxygen uptake of yeast? Hypothesis: The respiration rate can be measured by the means of a respirometer by calculating the uptake of oxygen per unit time. stopper. measuring cylinder. Apparatus: Boiling tubes. micropipette Materials: Yeast. manometer tube. The manometer tube was filled with approximately 200 μl of red dye using a micropipette. Both of the boiling tubes were filled with 7cm3 of potassium hydroxide solution. on the gauze and not touching the potassium hydroxide solution. 7. 5. . 6. A gauze was placed in the other boiling tube. and a syringe was inserted on top of the stopper. 3. One of the boiling tubes was stoppered.Procedure: Diagram 5: Apparatus Set-up 1. The stoppers were replaced. Two filter papers soaked in yeast were placed in the experimental tube. 4. The apparatus was set up as shown above 2. as shown in Figure . • The increment of red dye level was assumed to be the volume of oxygen absorbed by the yeast.8.60 Table 1: Table showing Displacement of manometer Level in a Period of 12 Minutes Final level of manometer fluid = 6.6 3.90 4 3.60 3 3.7 2.10 2 3.8 1.30 5 4.20 8 5.00 1 2. The liquid in the manometer tube was adjusted using the syringe attached to the non- experimental tube so that the level of the liquid in the manometer tube became equal 10. The manometer tube was connected to both of the boiling tubes simultaneously. The readings of the level of the coloured dye is recorded every minute for 6 minutes.1 0. The three way tap was turned to ensure air flows between the manometer and the boiling tubes 12.5 2. Time/Minutes Readings on Manometer/cm Displacement in Manometer Level/cm 0 2.5cm Initial position of syringe piston = 0.0 2.1 3.30 12 6.1cm . The starting position of the fluid was recorded 11.50 9 5.5cm3 Displacement in manometer level (cm) = Final reading (cm) – Initial reading (cm) *Displacement in manometer level corresponds to the total amount of oxygen consumed. 9.90 6 4.6 0.10 11 5.3 2.5 0.4 1.00 7 4.4 0.80 10 5. Results: Initial level of manometer fluid = 2.8 3. Final position of syringe piston = 0.1 cm – 2.6 cm Calculated rate of oxygen uptake (cm s-1) = = 3.5 cm = 3.00 x 10-3 cm s-1 .6 cm ÷ 720 seconds = 5.5cm3 Total increment in manometer reading = Total amount of oxygen consumed (cm) = 6. The rate of respiration is calculated by measuring the amount of oxygen consumed by yeast over a period of time. Before the experiment. while the oxygen in the experimental tube is being used up in respiration. the level of red dye increases in response to the decreased pressure. As the volume of air decreases. The control tube is very important as it helps to compensate for the change in temperature and pressure of the atmosphere. Thus. easily available and also easy and safe to handle. When the three way tap is turned to the direction of the manometer and the stopwatch was started. the level of the red dye in the manometer was adjusted to be at the same level at both sides and the initial level on the experimental tube side was recorded. This shows that the volume of air in the experimental tube is decreasing as time passes. the pressure also decreases. This will help to ensure that the change in level of red dye is solely due to the respiration of yeast and not by other external factors. the volume of gas remains constant and the pressure is constant as well. The oxygen consumed is indicated by the level of fluid in manometer. while the level of dye on the control side decreased. As there is no respiration taking place in the control tube. The equation for respiration is as shown below: . it can be seen that the level of red dye at the side of the manometer connected to the experimental tube started increasing.Analysis of results: In this experiment. The volume of air decreased as carbon dioxide released during respiration has been absorbed by the potassium hydroxide solution. yeast was used as it is cheap. The connections to the tubes may not have been completely tight and secure. The level of red dye does not change. thus making the results of the experiment more reliable. Although this may be compensated slightly by the control set. This will result in wrong readings being taken and the results of the experiment being less accurate. Thus. Thus. Fluctuations in surrounding temperature also affect the experimental results as gas expands when temperature increases and thus have a bigger volume. the rate of respiration calculated may not be accurate as when yeast respires anaerobically. the stopper for the boiling tubes and the connection between the syringe and the non-experimental tube. parallax error are likely to occur when the measurement of the level of the coloured liquid in respirometer. This may allow the gas inside the tubes to escape through the unsealed gaps. there is no change in volume of gas in the experimental tube and hence. All the connections should be sealed tightly with cling film to ensure the connections are airtight and air is unable to escape via the connections. Besides. they do not take in oxygen and the carbon dioxide released is absorbed by potassium hydroxide solution. Some ways to overcome these limitations and sources of errors are to use other organisms such as crickets that only undergo aerobic respiration. no change in pressure. This will ensure temperature is kept constant and does not affect the displacement of red dye. This will ensure that the air pressure does not change due to gas escaping from the tubes. Fluctuations in the surrounding temperature can be overcome by using a water bath set at a constant temperature. it may still affect the displacement of the red dye over the period of time when it is recorded. . for example the connection between the delivery tubes to the manometer tube.Discussion: The main limitation in this experiment is that yeast is a facultative anaerobe and can respire both aerobically and anaerobically. the eye level must be perpendicular to the scale of the respirometer. if the temperature is too high. and finally respiration ceases and organisms die. This will prevent parallax error and wrong readings to be taken and make sure the results are more accurate and reliable. the surrounding temperature. The displacement of the coloured fluid in the capillary tube is an indication to the uptake of oxygen. not using a hand as the broken glass may cut the fingers. living organisms take in oxygen from the surrounding and release carbon dioxide. Theoretically. we can conclude that the rates of respiration of yeast is 5. enzymes may denature. However. the rate of respiration increases with temperature as the enzyme activity speeds up at higher temperature. Conclusion: During aerobic respiration where oxygen is available. If the KOH comes into contact with skin accidentally. the broken apparatus should be swept away using a broom. wash under running tap water immediately.When readings are taken. If the apparatus breaks. Safety precautions: 1. for instance. 2. 3. a manipulated variable can be included to this experiment. Potassium hydroxide solution has to be handled with care as it is strong base and corrosive. Water bath with different temperature can be used and their effects on the respiration rate can be investigated.00 x 10-3 cm s-1 Further work: For further investigation. In this experiment. The respiration rate can be measured by means of a respirometer by calculating the uptake of oxygen per unit time. Word count: 2240 words . Care must be taken when handling the apparatus to avoid the apparatus from breaking. http://www. Edexcel Biology.essortment.htm 6.html 3. http://biology. Web based: 1.com/what-is-aerobic-respiration. 2008.htm 5. A Pearson Company 2008.com/all/cellularrespira_rmpr.sinica. London.com/biology/respire. 3.rcn.ma.htm 2.html .tw/ckao/About%20the%20Lab. Hodder Education.about. UK.Bibliography: Non web based: 1. http://www.com/jkimball. http://idv.purchon.com/od/cellularprocesses/a/cellrespiration.J.html 4.wisegeek. Edexcel A2 Biology.ultranet/BiologyPages/C/CellularRespiration. http://www. Clegg C.edu. A Pearson Company. http://users. Salters-Nuffield Advanced Biology for Edexcel A2 Biology 2.