Carbohydrate metabolism Flashcards
PFK is activated by a high ……. : ……. ratio
High insulin:glucagon
Muscle PFK is allosterically inhibited by a high ATP:AMP ratio. True or false?
True
By what method is pyruvate kinase regulated?
By phosphorylation/dephosphorylation depending on insulin:glucagon ratio
In which tissues does anaerobic respiration occur?
RBC’s and skeletal muscle
In galactosaemia, which enzymes may be deficient?
Galactokinase and UDP uridyl-transferase
When galactose accumulates in galactosaemia, what pathways can it enter?
It is converted to galacitriol via the enzyme aldose reductase. This pathways depletes NADPH.
How do you treat galactosaemia?
No lactose in the diet
What is the enzyme involved in the pentose phosphate pathway?
Glucose 6 phosphate dehydrogenase
What are common symptoms of a G-6-P DH deficiency? (2)
Anaemia and cataracts
Which tissues is the pentose phosphate pathway important in?
RBCs, adipose tissue and the liver
What is essential fructosaria?
It is the lack of fructokinase
If the aldolase is deficient resulting in fructose intolerance. Why is the condition harmful?
Accumulation of fructose 1-phosphate is toxic
What is the main clinical sign of essential fructosaria?
Fructose in the urine
What is the enzyme that catalyses the link reaction?
Pyruvate dehydrogenase
How is pyruvate dehydrogenase regulated?
By dephosphorylation/phosphorylation
What is the equation for the link reaction?
Pyruvate + CoA + NAD+ –> Acetyl-CoA + CO2 + H^+ + NADH
Pyruvate dehydrogenase when phosphorylated is inhibited. What are the name of 4 substrates that inhibit PDH?
Acetyl-CoA, NADH, ATP and citrate
Give an example of a substrate that activates PDH via dephosphorylation. (5)
Pyruvate, CoASH, NAD+, ADP, Insulin
Give the two key enzymes involved in the Krebs cycle?
Isocitrate dehydrogenase and a-ketoglutarate dehydrogenase
Where does the Kreb’s cycle occur?
The mitochondrial matrix
What effect does cyanide have on oxidative phosphorylation?
It inhibits the proton translocating complex
What is thermogenin and where is it found?
It is a natural uncoupler and found in brown adipose tissue
What is the difference between the enzymes involved in oxidative phosphorylation and substrate level phosphorylation?
The enzymes in oxidative are membrane bound as opposed to soluble enzymes
In which process does energy coupling take place directly? Oxidative or substrate level?
Substrate level phosphorylation
