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Respiration Revision Questions and Answers

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F214 Communication, Homeostasis and Energy Module 4 Respiration 4.4.1 Respiration a. Outline why plants, animals and microorganisms need to respire, with reference to active transport and metabolic reactions All living organisms need energy so as to undergo their biological processes, of which all of the reactions are known altogether as metabolism. Metabolic reactions Those that build large molecules are anabolic. Those that break large molecules into smaller ones are catabolic. Active transport It is when ions and molecules are moved across a membrane against the concentration gradient. A lot of an organisms energy is used for this. Secretion When large molecules in some cells are removed via exocytosis. Endocytosis The movement of large molecules into the cell. Synthesis of large molecules from smaller ones. Replication of DNA and synthesis of organelles. Movement e.g. cilia Activation of chemicals. b. Describe the structure of ATP Adenosine= Ribose + Adenine Adenosine Monophosphate= Phosphate + Ribose + Adenine Adenosine Diphosphate= Phosphate + Phosphate + Ribose + Adenine Adenosine Triphosphate= Phosphate + Phosphate + Phosphate + Ribose + Adenine c. State that ATP provides the immediate source for biological processes ATP is a universal energy currency because it is in every living organism in cells, and energy can be created by losing a phosphate group and can be added to the molecule by adding a phosphate. ...read more.


m. Outline the Krebs cycle with reference to the formation of citrate from acetate and oxaloacetate and the reconversion of citrate to oxaloacetate and n. Explain that during the Krebs cycle decarboxylation and dehydrogenation occur, NAD and FAD are reduced and substrate phosphorylation takes place Krebs cycle Acetate is removed from the coenzyme a and joins with oxyaloacetate to form citrate. Citrate is decarboxylated (removing one carbon dioxide molecule) and dehydrogenated (removing a pair of hydrogen atoms) to form a five carbon compound. The pair of hydrogen atoms are accepted by NAD which makes Reduced NAD. The 5 carbon compound is decarboxylated and dehydrogenated to form a 4 carbon compound and another molecule of Reduced NAD is made. The 4 carbon compound is changed to another 4 carbon compound. Substrate level phosphorylation takes place where a molecule of ATP is produced by the phosphorylation of ADP. The new 4 carbon compound is changed into another 4 carbon compound. A pair of hydrogen atoms are removed and accepted by FAD to make Reduced FAD. This new 4 carbon compound is then dehydrogenated and makes oxaloacetate again. Another molecule of Reduced NAD is made. This happens once for every molecule of acetate so happens twice for every molecule of glucose. In total 6 reduced NADs, 2 reduced FADs, 4 carbon dioxide and 2 ATPs are made. ...read more.


Each pyruvate molecule loses a carbon dioxide molecule. So the pyruvate is decarbonised and becomes ethanal. The reaction is catalysed by the enzyme Pyruvate decarboxylase. Ethanal accepts hydrogen atoms from reduced NAD which becomes reoxidised. Ethanal becomes ethanol and is catalysed by ethanol dehydrogenase. v. Define the term respiratory substrate Respiratory substrate- An organic substance that can be used for respiration. w. Explain the difference in relative energy values of carbohydrate, lipid and protein respiratory substrates Carbohydrate Lipid Protein Energy value=15.8 kJg-1 Theoretically the respiration of 1 mol of glucose should be nearly 94 but it is more like 30 mol ATP. It has an efficiency of about 32%. Other monosaccharaides are changed to glucose for respiration. Energy value=39.4kJg-1 Each fatty acid is combined with CoA which needs energy from the hydrolysis of ATP to AMP. The fatty acid-CoA complex is transported into the mitochondrial matrix where it is broken down into 2-carbon acetyl groups. Reduced NAD and Reduced FAD is formed. When the acetyl groups are released from CoA they enter the Krebs cycle and make three molecules of Reduced NAD, one molecule of Reduced FAD and one molecule of ATP. Energy value=17.0kJg-1 When an organism undergoes fasting, starvation or prolonged exercise protein from muscles can be respired. Some can be converted to pyruvate, some to acetate and some enter the Krebs cycle directly. The number of hydrogen atoms accepter by NAD and used in oxidative phosphorylation is slightly higher than glucose so proteins release slightly more energy than carbohydrates. ...read more.

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