Скачать с ютуб Anaerobic Respiration in Mammals, Plants & Fungi | A-level Biology | OCR, AQA, Edexcel в хорошем качестве

Anaerobic Respiration in Mammals, Plants & Fungi | A-level Biology | OCR, AQA, Edexcel

Anaerobic Respiration in Mammals, Plants & Fungi in a Snap! Unlock the full A-level Biology course at http://bit.ly/2W776sF created by Adam Tildesley, Biology expert at SnapRevise and graduate of Cambridge University. SnapRevise is the UK’s leading A-level and GCSE revision & exam preparation resource offering comprehensive video courses created by A* Oxbridge tutors. Our courses are designed around the OCR, AQA, SNAB, Edexcel B, WJEC, CIE and IAL exam boards, concisely covering all the important concepts required by each specification. In addition to all the content videos, our courses include hundreds of exam question videos, where we show you how to tackle questions and walk you through step by step how to score full marks. Sign up today and together, let’s make A-level Biology a walk in the park! The key points covered of this video include: 1. Respiration in the Absence of Oxygen 2. Introduction to Anaerobic Respiration 3. Anaerobic Respiration in Mammals 4. Anaerobic Respiration in Plants and Fungi Respiration in the Absence of Oxygen So far we have seen how ATP is generated in the presence of oxygen during aerobic respiration. However, in some circumstances there is not enough oxygen available in a given time period to carry out aerobic respiration. When oxygen isn’t present, it cannot act as the final electron acceptor. When there is now final electron acceptor, the proton gradient across the inner mitochondrial membrane cannot be maintained. This also means that redNAD and redFAD cannot unload their hydrogen atoms at the inner mitochondrial membrane. Therefore the Links Reaction, the Krebs Cycle and oxidative phosphorylation cannot occur. Introduction to Anaerobic Respiration The only respiratory pathway that can continue without oxygen is glycolysis. To produce ATP glycolysis requires a free NAD to accept a hydrogen atom from triose phosphate and this results in the formation of redNAD. To allow glycolysis to continue, this redNAD needs to be reoxidised to NAD so it can return to glycolysis and accept a hydrogen atom again. To allow glycolysis to continue, this redNAD needs to be reoxidised to NAD so it can return to glycolysis and accept a hydrogen atom again. It cannot be reoxidised at the electron transport chain so another pathway is needed to re-oxidise NAD. Anaerobic respiration therefore consists of glycolysis combined with an alternative pathway to re-oxidise NAD. Anaerobic Respiration in Mammals Anaerobic respiration always occurs in the cytoplasm of the cell. In mammals, the lactate fermentation pathway is used to re-oxidise the reduced NAD so it can be reused in glycolysis. Lactate fermentation occurs mostly in muscle tissue when the demand for ATP for muscle contraction is high and there is an oxygen deficit. In the lactate fermentation pathway a molecule of pyruvate, which was produced during glycolysis, accepts the hydrogen atoms from the reduced NAD - also made in glycolysis. This is catalysed by the enzyme lactate dehydrogenase and it results in the formation of lactate and oxidised NAD. This oxidised NAD can then go back and accept more hydrogen atoms from triose phosphate during glyclolysis. This allows ATP production from glycolysis to continue. Lactate is acidic so if it is not removed from the muscle tissue it can lower the pH in the tissues and inhibit the actions of important enzymes. To prevent this, the lactate produced is transported to the liver where it is converted back to pyruvate when more oxygen is available. Anaerobic Respiration in Plants and Fungi Fungi and plants use the ethanol fermentation pathway to reoxidise reduced NAD. In this pathway, the pyruvate produced from glycolysis is decarboxylated and converted to ethanal. This reaction is catalysed by the enzyme pyruvate dehydrogenase. The oxidised NAD is then available to accept more hydrogen atoms from triose phosphate during glycolysis. Summary Without oxygen aerobic respiration cannot take place Anaerobic respiration takes place in the cytoplasm and occurs when there is no oxygen available Anaerobic respiration consists of glycolysis and an alternative pathway to reoxidise reduced NAD Reduced NAD has to be reoxidised so it can accept hydrogen atoms during glycolysis and allow glycolysis to continue In mammals the lactate fermentation pathway is used to reoxidise reduced NAD In plants and fungi the ethanol fermentation pathway is used to reoxidise reduced NAD