Carbs 3 Flashcards
What is the structure of glycogen?
- Polymer of glucose (a1-4) subunits
- a1-6 branches occur every 8-12 residues
What does glycogenin do?
Covalently binds glucose from UDP-glucose to form chains of 8 subunits
What enzyme takes over glycogenin after the primer has been made?
Glycogen synthase
What enzyme breaks glycogen to form the 1-6 branching points?
Glycogen-branching enzyme
How is glucose removed from glycogen?
As G-1-P
What is the aim of glycolysis?
To save some of the potential energy from glucose as ATP through substrate level phosphorylation
What stages are irreversible in glycolysis?
- Glucose to G-6-P
- F-6-P to F-1,6-Bisphosphate
- PEP to pyruvate
What enzyme is used to convert glucose to G-6-P in glycolysis?
Hexokinase
What enzyme is used to convert F-6-P to F-1,6-BP
Phosphofructokinase
What enzyme is used to convert PEP to pyruvate?
Pyruvate Kinase
What can pyruvate be used for in the human body?
- Converted to lactate in vigorously exercising muscle
- Converted to acetyl coA in aerobic conditions
What is lactate dehydrogenase used for?
Converting lactate into pyruvate
What is used by lactate dehydrogenase to make this conversion?
NAD+
What does pyruvate dehydrogenase do?
Converts pyruvate into Acetyl CoA
How is lactate made back into glucose?
Through gluconeogenesis in the liver.
How does the cell bypass the unfavourable reactions in gluconeogenesis?
By using different enzymes that catalyse a different set of reactions
How much glucose in grams is used by the brain as energy per day?
120g
On average how much glucose can be produced from glycogen stores?
190g
What is pyruvate first converted into to be reverted to PEP in gluconeogenesis
Oxaloacetate
When does gluconeogenesis usually end?
F-6-P to G-6-P
What is fructose converted into to be able to be used in glycolysis?
F-1-P
How is F-1-P converted to F-6-P
Through internal rearrangement of the structure
How can galactose be used in glycolysis?
It can be converted to glucose through UDP-glucose:galactose 1-phosphate uridylyltransferase
What does the pentose phosphate pathway produce?
- NADPH
- Pentose sugars
What are the two parts of the pentose phosphate pathway?
- Oxidative irreversible part
- Non-oxidative reversible part
What does the oxidative part produce?
- NADPH
- Converts G-6-P into a pentose phosphate
What does the non oxidative part produce?
Interconverts G-6-P and a pentose phosphate to form lots of 3, 4, 5, 6, 7 carbon sugars.
What are some real life examples of enzyme and electron carrier deficiencies?
- Black water fever
- Inability to convert hydrogen peroxide as it requires NADPH
What does glutamate combine with in the glucose alanine cycle in the tissues?
Pyruvate
What does the combination of glutamate and pyruvate produce?
- Alpha ketoglutarate
- Alanine
