3.7a Anaerobic Respiration
25/11/2012 § 1 Comment
Welcome to the fifth unit of Biology Year One. Today we’ll be starting one of the hardest concepts to cover: Cell respiration. Okay. Let’s get this over with.
Cell respiration. It is “the controlled release of energy from organic compounds to form ATP” as cells cannot absorb ATP through their plasma membranes and must instead produce their own supply. We all know that ATP is adenosine-triphosphate, which is the currency the cell uses to do the many different reactions for it to function. Cells do three main types of activity to fully function. These are:
- synthesizing macromolecules such as nucleotides and proteins
- pumping substances, typically molecules or ions, across membranes by active transport
- transporting substances around the inside of the cell
The most common way for cell respiration to release energy is through carbohydrates and lipids and glycolysis, which is the chain of reactions (taking place in the cytoplasm) that converts glucose into pyruvate. There is no oxygen used in glycolysis and very little ATP is produced, therefore, if there is no oxygen available for a cell to use – these are called anaerobic conditions – this is the process they use in cell respiration. For reasons I am not sure of myself, glycolysis can only continue in anaerobic conditions if the cell converts the pyruvate (the product of glycolysis) into another substance. For humans, it becomes lactic acid, but for other organisms, such as yeast cells, pyruvate converts into ethanol and carbon dioxide.
Glycolysis is not a single-step process but is instead a process composed of many small steps. It is an example of a metabolic pathway – something we learned during our enzyme unit, if I’m not mistaken. Quick, let’s recap and review that glycolysis changes glucose into pyruvate. What happens is that glucose phosphorylates into fructose, then again into fructose phosphate, then finally fructose biphosphate. The phosphorylations (which are the additions of phosphate groups) are what reduce the activation energy for the following reactions. Fructose biphosphate splits (somehow) to form two triose phosphate molecules, which are then oxidized to become glycerinate-3-phosphate. The hydrogen atoms (and only the hydrogen atoms) are removed from the molecule to be accepted by NAD+, converting it to NADH + H+. The last stage of glycolysis involves the transfer of the phosphate group to an ADP molecule to product ATP (finally). See the image below for clarifications.
- Outline the process of glycolysis. (5)
- Draw the structure of a mitochondrion as seen in an electron microscope. (5)
- Explain how the structure of the mitochondrion allows it to carry out its function efficiently. (8)
- Explain the reactions that occur in the matrix of the mitochondrion that are part of aerobic respiration. (8)
- Explain the process of aerobic respiration. (8)
- Outline the role of oxygen in providing cells with energy. (6)
- Explain how chemiosmosis assists in ATP production during oxidative phosphorylation. (9)
- Explain the similarities and differences in anaerobic and aerobic cellular respiration. (8)
- Describe the central role of acetyl (ethanoyl) CoA in carbohydrate and fat metabolism. (5)
DATA BASED QUESTIONS
Page 89, production and consumption of ATP
- a) State the volume units that are shown in the equation. dm^3
- b) State the mass units that are shown in the equation. g (grams) and kg (kilograms)
a) Calculate the mass of ATP produced per dm3 of oxygen.
0.14 kg per dm3 of oxygen (18.25 ATP kg / 134.4 oxygen dm3 = 0.14kg ATP / dm3)
b) Calculate the mass of ATP produced per race in Table 1.
Length of race / m Volume of oxygen consumed in cell respiration during the race / dm3 Mass of ATP produced per race (volume of oxygen * 0.14kg) / kg 1,500 36 4.88 10,000 150 20.37 42,300 700 95.10
3. Explain how it is possible to synthesize such large masses of ATP during races.
During races, the runner has to frequently draw in a lot of oxygen in order to keep running, and every breath of air allows him to take in large supplies per breaths. Because of the large amount of air consumed during races, the runner’s body is given a large supply of oxygen that is used for aerobic cell respiration, because it is supplied with oxygen to use in order to make ATP. The oxygen available in the runner’s body will be recycled and used again to make such large amounts to ATP during the race.
4. During a 100m race, 80g of ATP is needed but only 0.5dm3 of oxygen is consumed. Deduce how ATP is being produced.
ATP is being produced by glycolysis because, if very little oxygen is being consumed, then the amount of ATP that can be produced will be made through glycolysis, a cellular respiratory process that requires no oxygen in order to make ATP.