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Biochem and medical genetics

Quiz yourself by thinking what should be in each of the black spaces below before clicking on it to display the answer.
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Question
Answer
Role of Hormones   show
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show Secreted by beta cells in the fed state Stimulated by increased blood glucose, certain amino acids and fatty acids Signal of substrate excess Tells tissue to store fuel and breakdown glucose  
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show Secreted by alpha cells in the fasted state Stimulated by low glucose Signal of substrate deficiency Only acts on liver Signal to liberate glucose into blood from liver  
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Adrenaline   show
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show Diverse group of molecules Stored as triglycerides Used for energy as non-esterified fatty acids Converted into sterols and phospholipids Hydrophobic - need specialised transport molecules  
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show Large stores More energy dense per molecule than glucose Rapidly mobilised and stored Ideal for tissues with high energy demand Cant be used by all tissues Requires more oxygen than glucose  
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show Digestion of dietary fats De novo lipogenesis Use in oxidative tissue to make energy Storage in adipose tissue Used to make ketone bodies in the liver  
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Digestions   show
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show Inside intestinal cells, mixed micelles are reformed into TAG Fatty acids are combined with cholesterol and glycerol to form chylomicrons These are surrounded by apoproteins to make them hydrophilic  
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show LPL sits on surface of endothelial cells Hydrolyses TAG in the chylomicron into NEFA This releases NEFA for uptake by adipose and muscle LPL is activated by insulin  
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show Organelles squashed to the outside Majority is a lipid droplet Adipose triglyceride is a mixture of saturated and unsaturated fatty acids  
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Transport of NEFA in the blood   show
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show Activate by phosphorylation via adrenaline activating cAMP and PKA This increases fuel to the muscles and heart Inactivated by dephosphorylation by protein phosphatase, activated by insulin signalling  
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Plasma NEFA concentrations   show
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show Many cells have TAG stores Provides a source of energy is need to suddenly produce ATP TAG stores must be kept low to avoid damaging normal function Too much TAG leads to non-alcoholic fatty liver disease etc  
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show Fats are more energy rich than glucose - the heart needs more ATP per gram than any other organ Its use of TAG leaves glucose for cells which must use it 60-70% of ATP comes from fatty acid oxidation Contains intrinsic TAG stores  
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show Kidneys require large amounts of energy to accomplish reabsorption Cortex is highly reliant on fatty acids Medulla has a poor oxygen supply - limited mitochondrial respiration so rely on glucose  
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show Type 1 - slow twitch - oxidative - higher reliance on fatty acids Type 2 - slower fast twitch and faster fast twitch - glycolytic - rely on glucose In exercise initially use glycogen stores, then switch to fatty acids when these run out  
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show Uptake Activation Carnitine shuffle Beta oxidation  
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Transport across the plasma membrane   show
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show Fatty acids are activated in the cytosol by adding a CoA molecule to form Fatty acyl CoA Catalysed by Acetyl CoA synthetase Uses ATP Traps them in the cell and makes them a substrate for further enzymes  
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show Need to cross highly impermeable inner membrane - no transporter Conjugated with carnitine which can be transported Achieved by 2 enzymes and one transporter  
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Carnitine Shuffle   show
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Stages of beta oxidation   show
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Isoforms of Acyl CoA dehydrogenase   show
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Products of Beta oxidation   show
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show Contain a cis double bond Isomerase converts cis to trans double bond Reductase makes it a substrate for ongoing oxidation  
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show B oxidation produces acetyl CoA with 2 carbons, so if an odd chain FA enters this is not possible The last cycle generates 1 Acetyl CoA and 1 propionyl CoA This can then be metabolised to succinyl CoA and enter the krebs cycle  
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Dealing with short chain fatty acids   show
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show 20-22 carbons Must be shortened in the peroxisomes to 16-18 carbons Then transferred to mitochondria This does not generate ATP but produces H2O2  
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show Starts in peroxisomes with alpha oxidation before transfer to mitochondria for beta oxidation  
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show Hormone sensitive lipase - regulated by hormonal phosphorylation as an external signal The carnitine shuffle - regulated intracellularly via allosteric control - inhibited by malonyl CoA from lipogenesis to prevent futile cycling  
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show Relatively rare genetic disorder Unable to take carnitine up into cells, shutting down the carnitine shuffle Cardiomyopathy, fatty infiltration of organs, muscle weakness and hypoglycaemia Caused by switch from FAs to glucose as a fuel  
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Jamaican Vomiting Sickness   show
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