Carbohydrate Metabolism

Hannah Tribe
Flashcards by Hannah Tribe, updated more than 1 year ago
Hannah Tribe
Created by Hannah Tribe over 7 years ago
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Degree MCBHD Flashcards on Carbohydrate Metabolism, created by Hannah Tribe on 04/29/2014.

Resource summary

Question Answer
What is the process that converts glucose to pyruvate? Glycolysis
What is average blood glucose? 2.5mM
Name 5 symptoms of hypoglycaemia 1. Muscle weakness 2. Loss of coordination 3. Mental confusion 4. Sweating 5. Coma/death?
In hyperglycaemia, ________ can be modified without _______ because glucose is very ________. This can lead to conditions such as _________, and modify lipoproteins important in ____________. proteins, enzymes, reactive, cataracts, atherosclerosis
What is another risk in hyperglycaemia? Hyperosmolar coma - imbalance in water retention
What mechanisms are used to lower blood glucose? (3) 1. Glycogen synthesis 2. Pentose phosphate pathway 3. Fatty acid synthesis
What mechanisms are used to raise blood glucose? (2) 1. Glycogenolysis 2. Gluconeogenesis
Where is most glycogen synthesised? Liver
At which stage of glycolysis is glycogen synthesised? After conversion of glucose to G-6-P by glucokinase (in liver)
What protein is associated with glycogen? Glycogenin
What is glycogen? A storage molecule, capable of storing high concentrations of glucose.
Where is glycogen found? Liver hepatocytes and muscle
Why can glucose not be stored in its natural state? It is osmotically active
Glycogen is a much more efficient way of storing glucose. 400mM of glucose can be stored as _______ glycogen. 0.01 microM
Why can fat not be used as the energy store? (3 reasons) 1. Fat takes much longer to be mobilised 2. Fat cannot be used for energy if there is no oxygen 3. Fat cannot be directly converted to glucose
1. G-6-P is converted to _______ Glucose 1 phosphate (G-1-P)
2. The G-1-P molecule is converted to ____-______ by the enzyme ____-________ __________________, using a molecule of ____. This activates the _________ molecules so they will readily _______. UDP-glucose, UDP-glucose pyrophosphorylase, UTP, glucose, react
3. ___-______ combines with _________ and a chain forms with multiple molecules of ____-_______, under the action of the enzyme __________ _________. UDP-glucose, glycogenin, UDP-glucose, Glycogen synthase
4. When the chain is approx ___ residues in length, a ________ _________ removes the last ___/___ residues and moves them down the chain to form a _______. 11, branching enzyme, 6/7, branch
What is the advantage of having many branches? There are lots of 'ends' which can be broken off in times of need and be converted to glucose.
What kind of links exist between the chain and branches? Alpha 1,6
What kind of links exist between each UDP-Glucose molecule in the chain? Alpha 1,4
Which enzyme removes the alpha 1-4 links between glucose molecules? phosphorylase
Which enzyme converts the resultant G1P back to G6P in a reversible reaction? phosphoglucomutase
What are the 2 possible fates of this G6P? 1. In muscle, this will directly enter glycolysis to produce ATP 2. In the liver, it will be exported back into the bloodstream in order to raise blood glucose levels
Once the chain of glucose is too short on a branch, ____________ moves all but the last residue onto the end of the original chain. Translocase
When there is a single glucose residue left on a branch, ___________ _________ removes the _________ __ __ bond and leaves a single _________ molecule. debranching enzyme, alpha 1-6, glucose
If this occurs in the liver, it will be exported to the ______ ______ to raise _______ ________ levels. In muscle, it will be converted to ___ ___ ___ and enter __________ to produce ______. blood stream, blood glucose, G6P, glycolysis, ATP
Which enzyme converts G6P to glucose? Where is it found? Glucose 6 phosphatase, in the liver and kidneys
Mobilisation of glycogen is so efficient because multiple ____________ molecules bind to each glycogen particle at the same time. phosphorylase
Glycogen phosphorylase is a _______-_______ complex, and can be activated by _____________. multi-enzyme, phosphorylation
Which enzyme phosphorylates the inactive phosphorylase b to the active form? phosphorylase b kinase
Breakdown of glycogen can be stimulated by hormones binding to the cell membrane. Examples are ________ and __________. They stimulate the ____ pathway to cause increased ______ and _____ inside the cell. It is the _____ which phosphorylates and therefore activates ____________ ___ ________ enzyme, so that ________ __________ can be activated. glucagon and adrenaline, Gs, cAMP and PKA, PKA, phosphorylase b kinase, glycogen phosphorylase
PKA also phosphorylates ___________ _________ to its inactive form so that ____________ of __________ is inhibited. glycogen synthase, synthesis of glycogen
Which ion can also activate phosphorylase b kinase? Ca++
How is a raise in calcium achieved in muscle and liver cells? In muscle: Ca++ is released for contraction, which is when energy is also needed. In liver: stimulation of alpha-1 adrenergic receptors activates Gq pathway and causes increased Ca++
Which molecule indicates the muscle cell is low on energy? AMP
When levels of this are high in muscle cells, __________ __________ __ can be activated without ______________ by the enzyme. glycogen phosphorylase b, phosphorylation
Similarly, when levels of _____ are high, the muscle cell does not need more energy so _____ binds to the same active site and ________ activation of ___________ _____________. ATP, ATP, inhibits, glycogen phosphorylase
This is also inhibited by ___________ __ _________. Glucose 6 phosphate
In the liver, high levels of ________ will inhibit activation of ___________ _____________. glucose, glycogen phosphorylase
What activates glycogen synthase? (3) 1. ATP 2. G6P 3. Dephosphorylation of glycogen synthase by protein phosphatase 1
What inactivates glycogen synthase? phosphorylation by protein kinase A
What is another fate of glucose 6 phosphate apart from forming pyruvate in glycolysis and being stored as glycogen? Entering the pentose phosphate pathway
What is the resultant product of this? Ribose 5 phosphate which can be used to form nucleotides and coenzymes to form DNA and RNA
This pathway produces 2 molecules of ______ which can be used to synthesise ______ _________. NADPH, fatty acids
This process also releases one molecule of _____. CO2
What is the name of the pathway which converts pyruvate back to glucose? Gluconeogenesis
Where does the majority of this take place? Liver
What are the 3 main substrates for gluconeogenesis? 1. Alanine 2. Lactate 3. Glycerol
In the __________ of the cell, _______ gets converted to pyruvate and combined with ________ to give ____________ ______, using the enzyme ___________ ____________. mitochondria, lactate, alanine, oxaloacetic acid, pyruvate carboxylase
Oxaloacetic acid is combined with more ______ ______ to give _________ ________, using the enzyme ____________ __________ _____________. amino acids, phosphoenol pyruvate, phosphoenol pyruvate carboxykinase
Phosphoenol pyruvate is combined with __________ (another 3C molecule) to produce ____________ __ __ ____________. This reaction does not require an enzyme, it is reversible. glycerol, fructose 1,6-bisphosphate
The enzyme ________ ___________ breaks this down to __ __ __, which is broken down further by _______ __ _________ to give glucose. fructose bisphosphatase, G6P, glucose 6 phosphatase
Where is the pyruvate formed? Matrix of the mitochondria
In the reactions to produce oxaloacetic acid from pyruvate, the oxaloacetate must be transported out of the matrix in the form of ________, before the rest of the reaction can take place in the ________. malate, cytoplasm
What stimulates gluconeogenesis? Glucagon
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