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Moores Biochem Test3

moores biochem

QuestionAnswer
some triacylglycerols solid at room temperature and some are liquid? triacylglycerols that don’t have any double bonds between in their hydrocarbon chain, are rigid and are solid at room temperature. But those that have double bonds, have “kinks” that distort the rigidity of the structure, causing them to be in the liquid
Will a 13-Carbon fatty acid be soluble in water? (No. If the fatty acid has more than 12 carbons, it will become hydrophobic, and therefore insoluble ).
What enzyme breaks up glycerol to yield fatty acids? Lipase
What is the first step of fat digestion in the intestines? Bile salts emulsify the fat
What is the function of intestinal lipases? (They degrade triacylglycerols. These products are then taken up by the intestinal mucosa, and the triacylglycerols are reformed).
What is the function of lipoprotein lipase? It converts triacylglycerols carried by chylomicrons to fatty acids and glycerol).
Where in the body is lipoprotein lipase located? (In the capillaries of the tissues).
What substance activates lipoprotein lipase? (Apo CII).
Why is having the B-48 marker on the chylomicron important in the liver? (This is how the liver cells recognize the empty chylomicron coat, and recycle it).
Once triacylglycerol is broken down, what can glycerol be used for? (It can enter the glycolytic pathway to be used for energy metabolism).
Why is it important to break down fatty acids into Fatty acyl-CoA as soon as they enter the cell? Because their carboxylic acid will become deprotonated and form a salt. An increased concentration of these can lyse the cell. So we form Fatty acyl-CoA which is much more stable
What are the 2 main results of beta oxidation? Making Acetyl CoA and generating ATP
What is the rate limiting step in beta oxidation? Moving the Fatty Acyl CoA from cytosol into the cell matrix
What happens to the electrons from beta oxidation? (They are captured by NAD+ and FAD+
Where does beta oxidation occur? (In the inner mitochondrial matrix)
What is the main purpose of all the different steps in beta oxidation? To form an unstable intermediate that can be cleaved off
Why does beta oxidation depend on the TCA cycle? Because sometimes the rate of beta oxidation is faster than the rate at which acetyl CoA is metabolized through the TCA cycle
When is acetone produced during beta oxidation? When beta oxidation advances at a very fast rate. It can leave the body through breath
Ketones can be used as an energy source to produce what? (2 acetyl CoA)
What is the first step of ketone synthesis? It is the reversal of the last step of beta oxidation, and forms acetoacetyl CoA).
ill ketones be overproduced or underproduced during starvation? Overproduced, because glyconeogenesis is activated during starvation/fasting. Same will be true for uncontrolled diabetes
In the fasted state, what will the liver be secreting? (Ketones and glucose).
What regulates the switch from carbohydrate metabolism to fat metabolism? Malonyl CoA
What activates the conversion of Acetyl CoA to Malonyl CoA by Acetyl CoA Carboxylase? (Insulin has an activating effect on Acetyl CoA Carboxylase).
Why is the presence of Malonyl CoA a regulatory step? Because it will block beta oxidation by inhibiting the carnitine shuttle and will go on to make new fatty acids instead
Why is Malonyl CoA a good precursor molecule for biosynthesis? (Because it is a high energy molecule).
What is the function of Transcarboxylase in the conversion of Acetyl CoA to Malonyl CoA? (It facilitates the movement of bicarbonate to Acetyl CoA to make Malonyl CoA
What 3 proteins make up the acetyl CoA carboxylase enzyme complex? (Transcarboxylase, biotin carboxylase and biotin carrier protein
How is the Malonyl CoA chain length increased to form Palmityl CoA (fatty acid synthesis)? It is part of a multistep reaction in which 2 carbon units provided by Malonyl CoA are added at a time, until we have a 16 carbon Palmityl CoA
What are the 4 reactions that make up fatty acid synthesis (in order)? Condensation, reduction, dehydration and again reduction
What are the 2 important sources of NADPH? The Pentose Phosphate Shunt and from the conversion of Malate to Pyruvate
Which enzyme is responsible for the conversion of Malate to Pyruvate? Malic enzyme
During the fed state, can Acetyl CoA be easily shuttled out of the mitochondria? No. It condensed with oxaloacetate to form citrate, which can then pass into the cytosol
What is the fate of citrate once it went from the mitochondrial matrix into the cytosol? (It is broken back down into Acetyl CoA and oxaloacetate
How do high levels of insulin affect citrate? Insulin activates citrate lyase, which allows for the formation of Acetyl CoA from citrate
One of the most important ways to regulate fatty acid synthesis is by regulating the acetyl CoA carboxylase complex. What is its function? (It convert Acetyl CoA to Malonyl CoA
The acetyl CoA carboxylase complex is regulated as follows: Citrate (inhibits/activates it), Insulin (inhibits/activates it), Glucagon (inhibits/activates it), Palmitoyl CoA (inhibits/activates it). (Citrate and Insulin-activate, Glucagon, epinephrine and Palmitoyl CoA- inhibit).
Why are Polyunsaturated fatty acids (PUFAs) structurally important? They contain more than one double bond in their chains).
. What are the 2 products of the Cyclooxygenase pathway? (Thromboxanes and prostaglandins
What is the main physiological function of thromboxanes? They affect platelet function
What 2 drugs inhibit cyclooxygenase activity? Aspirin and Ibuprofen
How does aspirin inhibit the cyclooxygenase activity? (It does so by covalently modifying the active site of the enzyme
What does it mean if a fatty acid is omega 6? (The first double bond on the chain is on the 6th carbon
How do ibuprofen and naproxen inhibit cyclooxygenase? They are competitive inhibitors, so they mimic the substrate
What do lipoxygenase enzymes produce? (Leukotrienes. These are involved in the asthma response)
What kind of effect do COX (cyclooxygenase) inhibitors have on leukotrienes? No effect
Isoprene is the building block of ………….. ? Cholesterol
What is the rate limiting step in cholesterol synthesis? The synthesis of mevalonate from acetate
Which enzyme from the cholesterol synthesis pathway do the “statin” drugs work on? HMG-CoA reductase. This is also the enzyme that is in the rate limiting step
Is cholesterol synthesis energetically favorable or not? The body uses a lot of glucose and ATP to make NADPH, which is needed for cholesterol synthesis
How are lipids able to the transported in blood, if they are hydrophobic? Lipids are packaged into lipoprotein particles, with a hydrophilic outer core
How is LDL and VLDL related? LDLs are VLDL particles that have given all of their triacylglycerols to the tissues
What is the function of HDL when it comes to cholesterol? HDL picks up cholesterol in the tissues and takes it back to the liver
What do chylomicrons signal? Dietary excess
LDL and HDL particles have high levels of what? Cholesterol
What is the functional different between ApoC-II and ApoC-III? ApoC-II activates lipoprotein lipase, while ApoC-III inhibits it
What will be the effect of the imbalance in the ratio of ApoC-II and ApoC-III? It will affect how lipids are cleared out of our system
What is the function of ApoE? It triggers clearance of VLDL and chylomicron remaints
In the fed state, what is Acetyl CoA turned into? Fatty acids and cholesterol. Then, ketone bodies in the fasted state
What organ supplies glucose during the fed state, and what organ supplies during fasting? Intestines during the fed state, and liver during fasting
Created by: Joren
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