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Respiration
Cellular respiration and ATP synthesis
| Question | Answer |
|---|---|
| Define cellular respiration. | It is the chemical breakdown of organic molecules that occurs inside all living cells. It is the transfer of chemical energy from organic molecules so that it is available in a useable form. |
| Give the values for the energy which can be harnessed from carbohydrates, lipids and proteins through cellular respiration. | Carbohydrates - 16 kJ g-1 Lipids - 39 kJ g-1 Proteins - 17 kJ g-1 |
| Give the name of the coenzyme which is always reduced during the oxidation of respiratory substrates. | NAD (nicotinamide adenine dinucleotide) - a very important hydrogen carrier. |
| Define aerobic respiration. | Respiration which requires oxygen. O2 is required for glucose to be completely oxidised to form CO2 and H20. |
| Define anaerobic respiration. | Respiration that does not require oxygen. |
| What is the final electron acceptor in aerobic respiration? | O2 |
| Define oxidative phosphorylation. | This is the final stage of aerobic respiration in which ATP is synthesized by chemiosmosis . It occurs in the inner mitochondrial membranes. |
| What is chemiosmosis? | The active transport of protons across a membrane and the subsequent facilitated diffusion down their electrochemical gradients with synthesis of ATP. |
| Define substrate-level phosphorylation. | Phosphorylation of ADP to form ATP that occurs in the active site of an enzyme in association with a substrate molecule. |
| Define phosphorylation. | Chemical process in which phosphate is added to a compound e.g. ADP to form ATP |
| What is the electron transport chain (ETC)? | Series of compounds that are alternately reduced and oxidised to transfer energy to form a proton gradient. |
| In anaerobic respiration, what is the final electron acceptor? | Pyruvate |
| Give the product(s) of anaerobic respiration in animals and some bacteria. | Lactate |
| Give the product(s) of anaerobic respiration in plants and fungi (e.g. yeast). | Ethanol and carbon dioxide |
| T or F. Glycolysis is common to to both aerobic and anaerobic respiration. The link reaction, Krebs cycle and oxidative phosphorylation occur in aerobic respiration only. | T |
| Define oxidation. | The loss of electrons and the loss of hydrogen. |
| Define decarboxylation | Reaction in which carbon dioxide is removed from a compound. |
| What is the fate of pyruvate in the cytosol when oxygen is available? | It enters the matrix and is converted to acetyl CoA via oxidative decarboxylation. |
| Describe the structure and function of the outer mitochondrial membrane. | -Phospholipid bilayer and proteins - Permeable to pyruvate, oxygen, carbon dioxide, ATP, ADP but not glucose |
| Describe the composition and function of the inner mitochondrial membrane - folded into cristae to give a large surface area | - Phospholipid bilayer with protein complexes of electron transport chain and ATP synthetase. - Pumping protons into intermembrane space; making ATP, permeable to pyruvate, oxygen, carbon dioxide, ATP, ADP BUT NOT hydrogen ions and glucose. |
| Describe the composition and function of the intermembrane space. | - Lower pH than cytosol and matrix - Site of high concentration of protons |
| Describe the composition and function of the matrix. | - Protein-rich region; contains DNA loop, ribosomes and many enzyme molecules. - Link reaction; Krebs cycle; production of urea |
| Describe the composition and function of the DNA in the mitochondria. | - Loop of double-stranded DNA not combined with histone proteins - DNA codes for 13 of the proteins used in the mitochondrion; genes are transcribed as mRNA; rest of mitochondrial proteins are coded for by DNA in the nucleus. |
| Describe the composition and function of the 70S ribosomes in the mitochondria. | - rRNA and proteins - translation - assembly of amino acids. |
| Give the number of carbon dioxide molecules produced through decarboxylation per one turn in the Krebs cycle. | 2 x CO2 in one turn |
| T or F. The Kreb's cycle undergoes two turns per glucose molecule. | T |
| Give the number of reduced NAD and reduced FAD produced through dehydrogenation per one turn of the Krebs cycle. | 3 x reduced NAD 1 x reduced FAD |
| Give the number of ATP molecules produced by phosphorylation in one turn of the Krebs cycle. | 1 x ATP |
| Respirometers are apparatus designed to measure rates of respiration. State three key features which are common to all respirometers. | 1) A container for living organisms 2) A carbon dioxide absorbent 3) A manometer to measure the decrease in volume of air inside the container |
| State three precautions which should be taken when conducting an investigation with a respirometer. | 1) Do not touch soda lime and other CO2 absorbents. Do not touch the organisms with bare hands. 2) Once the respirometer is set up, do not handle it as this may increase heat or alter behaviour (in case of animals) 3) Allow time for equilibration. |
| Give one advantage of using a Barcroft respirometer instead of a simple respirometer. | The tubes can be inserted into a water bath to maintain a constant temperature. It functions as a thermobarometer. A control tube is attached to the manometer. Any changes of temperature and pressure affect both sides equally and cancel each other out. |
| What is a control respirometer and what is it used for? | Apparatus set up exactly the same way as the test respirometer but with some inert material e.g. glass beads instead of the living organisms. It serves to validate that the rate of respiration observed by the actual organisms is genuinely from them. |
| Give the formula used to calculation rate of respiration. | V = π r ^2 h , where h is the distance moved by the coloured liquid. The unit of rate of respiration is cm^3/min. |
| Give one challenge associated with the use of respirometers. | Apparatus needs to be opened periodically for living organisms (animals) to receive fresh air. Scales on syringes in Barcroft respirometers are often difficult to read and errors can be introduced. |
| Define germination. | This is the process which occurs when the embryo inside a seed starts to grow. Enzymes and mitochondria in dry seeds become activated when soaked in water. These hydrolyze starch and lipids to produce glucose and fatty acids. |
| T or F. Germination is the most active stage in the life cycle of a plant. | T |
| What is the net gain of ATP during anaerobic respiration? | 2 ATP |
| T or F. Muscle tissues under high oxygen demand conditions respire aerobically as well as anaerobically. | T |
| Give one advantage and one disadvantage of anaerobic respiration in mammals. | - It is useful in providing energy as ATP very quickly to support exercise. - The build up of lactate in muscle tissues lowers the pH and reduces the efficiency of enzymes, leading to feelings of tiredness. |
| Define oxygen deficit. | The difference between the demand for oxygen in aerobic respiration during exercise and the volume supplied. |
| Define oxygen debt. | The volume of oxygen that is absorbed after exercise to respire lactate and restore oxygen concentrations in muscle and blood. |
| Give one way in which the bodies of sprinters are adapted to anaerobic respiration over an average individual. | They are able to tolerate higher concentrations of lactate in their blood. |
| Give 3 reasons why oxygen uptake remains high during the recovery period after exercise. | 1) Aerobic respiration of lactate in the liver 2) Re-oxygenating haemoglobin in the blood 3) Re-oxygenating myoglobin (oxygen store in muscle tissue) |
| Give 3 advantages of aerobic respiration in animals. | 1) 'Buys time' at the beginning of exercise until the lungs, heart and blood can provide oxygen to muscle tissue. 2) Provides a lot of ATP very quickly 3) Provides ATP for short-term explosive activity, such as sprinting, that last only a few seconds. |
| Give 3 disadvantages of aerobic respiration in animals. | 1) Wastage of energy; glucose is converted to lactate, which is energy rich. 2) Lactate is toxic above a certain concentration. 3) Net gain of ATP is only 2 per glucose molecule. |
| T or F. Yeast is a unicellular fungus that can be found growing on the surface of rotting fruit. | T |
| Define fermentation. | 1) The anaerobic respiration in yeast and other microorganisms. 2) The culture of any microorganism or eukaryotic cell grown in either anaerobic or aerobic conditions. |
| List three applications of the ability of yeast to ferment sugar to form ethanol and carbon dioxide. | 1) Bread making 2) Brewing (beer production) / rum making 3) Wine making. |
| What is the function of yeast in bread making? | The production of CO2 causes bread dough to rise (i.e. it causes leavening). |
| What is the 'must' in winemaking? | The fermented pulp of crushed grapes with yeast. |
| Give three reasons why the maximum theoretical number of ATP molecules is rarely, if ever, achieved. | 1) Some intermediates in glucose metabolism are not broken down completely. 2) The proton gradient is used to power the movement of substances into the matrix. 3) Chemiosmosis is not efficient as some protons 'leak' into the cytosol. |
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CAPE Biology Unit 2
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