Unit 2 Metabolism and Survival Key Area 2
Unit 2: Metabolism and Survival Key Area 2: Cell Respiration 15/01/2022 Metabolism and Survival
Respiration Cellular respiration pathways are present in cells from all three domains of life (the Archaea, Bacteria and Eukarya). The metabolic pathways of cellular respiration are of central importance to cells. They yield energy and are connected to many other pathways. 15/01/2022 Metabolism and Survival
The Role of ATP (adenosine triphosphate) is essential to biological systems as it is the link between reactions that release energy (catabolic) and those that use energy (anabolic). ATP is used to transfer energy to synthetic pathways and other cellular processes where energy is required. 15/01/2022 Metabolism and Survival
ATP also has the role of carrying out phosphorylation - adding phosphates to molecules. This very important, enzyme controlled, process regulates the function of many enzymes and receptors by either activating or deactivating the protein. e. g. during glycolysis ATP phosphorylates glucose forming glucose-6 -phosphate, this promotes continuous transport of glucose into the cell 15/01/2022 Metabolism and Survival
How is ATP made? The energy released by the breakdown of food (usually glucose) during cellular respiration is used to phosphorylate ADP. This releases ATP & Respiration: Crash Course Biology #7 http: //www. youtube. com/watch? v=00 jb. G_cf. Gu. Q First 4 ish minutes 15/01/2022 Metabolism and Survival
The membrane protein ATP synthase essential to the release of ATP. The ATP synthase enzyme is rotated by the flow of hydrogen ions returning to the matrix of the mitochondria. This catalyses the synthesis of ATP from ADP and Pi 15/01/2022 Metabolism and Survival
Answer the following questions. . . • Testing your knowledge Q 1 pg 148 • Applying your knowledge Q 2 & 3 pg 35 15/01/2022 Metabolism and Survival
Respiration During respiration, glucose is broken down in a series of enzyme controlled reactions. At various stages along the pathway hydrogen ions and high-energy electrons are removed by dehydrogenase enzymes and used in the synthesis of ATP. 15/01/2022 Metabolism and Survival
The metabolic pathways of respiration The enzymes controlled reactions of respiration are grouped into three: 1. Glycolysis 2. The citric acid cycle 3. The electron transport chain 15/01/2022 Metabolism and Survival
Glycolysis occurs in the cytoplasm of a cell. It is the breakdown of glucose to pyruvate. There are two stages to glycolysis: – The energy investment phase – The energy pay-off stage 15/01/2022 Metabolism and Survival
During the energy investment phase 2 ATP phosphorylate intermediate molecules The energy pay-off stage follows the investment phase and converts the intermediate molecules into two pyruvate molecules. This produces 4 ATP giving a net gain of 2 ATP during glycolysis. 15/01/2022 Metabolism and Survival
During the energy pay-off stage dehydrogenase enzymes remove hydrogen ions. These combine with the coenzyme NAD to form NADH can lead to the formation of ATP further on in the respiratory pathway (at the electron transfer chain) if oxygen is present. 15/01/2022 Metabolism and Survival
The Citric Acid Cycle If oxygen is present pyruvate gets passed on to the citric acid cycle. This stage takes place in the matrix of the mitochondria. 15/01/2022 Metabolism and Survival
A mitochondrion consists of two membranes: a smooth outer membrane and a folded inner membrane, surrounding a central matrix. The citric acid cycle takes place in the matrix. The electron transport chain consists of proteins embedded in the inner membrane. Folding of this inner membrane to form cristae increases the membrane’s surface area, so that more molecules of the electron transport chain can fit in. Very active cells contain lots of large mitochondria with many, long cristae. 15/01/2022 Metabolism and Survival
The Citric Acid Cycle After glycolysis 3 C pyruvate is broken down to a 2 C acetyl group that combines with coenzyme A to be transferred to the citric acid cycle as acetyl coenzyme A. During this carbon dioxide is released as a waste product and dehydrogenase removes hydrogen ions and high energy electrons which combine with coenzyme NAD to form NADH. 15/01/2022 Metabolism and Survival
The acetyl coenzyme A combines with oxaloacetate to form citrate. Citrate then goes through a series of enzyme-catalysed reactions which result in the generation of ATP, release of carbon dioxide and the regeneration of oxaloacetate. Again dehydrogenase removes hydrogen ions and high energy electrons, these combine with coenzymes NAD or FAD to form NADH or FADH 2. 15/01/2022 Metabolism and Survival
The Electron Transport Chain The electron transport chain is a series of proteins in the inner mitochondrial membrane. All the H ions and electrons passed to coenzymes NAD and FADH are passed to the electron transport chain. This stage results in ATP synthesis 15/01/2022 Metabolism and Survival
Within the electron transport chain the hydrogen ions and electrons now separate. The high energy electrons cascade down the electron transport chains and release their energy. The electrons are used to pump hydrogen ions across the inner mitochondrial membrane. The return flow of these ions rotates part of the membrane protein ATP synthase can then catalyse the synthesis of ATP. 15/01/2022 Metabolism and Survival
When electrons come to the end of the chain they combine with oxygen. Oxygen is the final electron acceptor, it combines with H ions and electrons forming water. 15/01/2022 Metabolism and Survival
A summary ATP & Respiration: Crash Course Biology #7 http: //www. youtube. com/watch? v=00 jb. G_cf Gu. Q 15/01/2022 Metabolism and Survival
Answer the following questions… • Testing your knowledge Q 2 & 3 pg 148 • Applying your knowledge Q 4 (Not d) & 5 pg 35 -36 • Give an account of glycolysis and the citric acid cycle in cells (8) 2013 revised higher • Give an account of the structure of the inner membranes of mitochondria and the function of the electron transport chain in cellular respiration. (8) 2015 revised higher 15/01/2022 Metabolism and Survival
Fermentation In the absence of oxygen at the citric acid cycle, fermentation takes place. Only two molecules of ATP are released – the net gain of two from glycolysis. In animal cells pyruvate is broken down in to lactate. This happens when doing vigorous exercise when oxygen is used up. This is reversible. 15/01/2022 In plant and yeast cells pyruvate gets converted to ethanol and CO 2. This is irreversible because CO 2 is lost from the cell. Metabolism and Survival
Alternative Substrates Glucose, the product of carbohydrate digestion, is the main respiratory substrate. Glycogen and starch (storage carbohydrates) can also be broken down into glucose for use during respiration. Other sugars can also be converted into glucose or intermediates of glycolysis. Fats and proteins can also be used as respiratory substrates when necessary. 15/01/2022 Metabolism and Survival
While excess dietary protein can be used as an energy source, most of the protein that is taken in is used for growth and repair of body tissues. Proteins are broken down to produce amino acids. When excess amino acids are broken down, some of the products enter the respiration pathway. proteins → amino acids → converted to pyruvic acid, acetyl co-enzyme A, or intermediates in the citric acid cycle 15/01/2022 Metabolism and Survival
Fat contains twice the energy of either carbohydrates or proteins. It can be broken down into fatty acids and glycerol, both of which can enter the respiratory pathway. fatty acids → converted to acetyl co-enzyme A before entering the citric acid cycle. glycerol → converted to intermediate molecules for use in glycolysis. 15/01/2022 Metabolism and Survival
Answer the following questions… • TYK Q 1 -3 pg 154 • End of topic 3 test 15/01/2022 Metabolism and Survival
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