Carbohydrates Structure& Metabolism Flashcards
Where are Glut-1 receptors found?
Red blood cells, Placenta, brain, kidney, colon, retina
Which Glucose Transporter molecule is Insulin dependent?
GLUT-4
Where are GLUT-4 transporters located?
Skeletal, heart muscle, adipose tissue
Where are Glut - 3 receptors located?
brain, placenta, kidney
Which receptors are found in the liver, pancreas, small intestine and kidney?
GLUT-2
GLUT -5 receptors are found ?
Small intestine, testis, sperms, kidney
Which enzyme phosphorylates Glucose to form Glucose-6-phosphate?
Hexokinase and Glucokinase
True or False? Hexokinase is under the influence of Insulin while Glucokinase is not.
FALSE!! Glucokinase is Insulin is under the influence of insulin while Hexokinase is not.
Which substance is required for the enzyme enolase?
Mg 2+
Which substance irreversible inhibit the enzyme Enolase thus stopping the whole glycolysis process?
Flouride
What is the rate limiting step of Glycolysis?
Fructose-6- phosphate is turned into fructose 1,6- bisphosphate using the enzyme.
What enzyme is used in the rate limiting step of Glycolysis?
Phosphofructokinase-1 (PFK-1)
What is substate level phosphorylation?
Substrate-level phosphorylation is a metabolic reaction that results in the formation of ATP or GTP by the direct transfer of a phosphoryl (PO3) group to ADP or GDP from another phosphorylated compound.
In what steps of Glycolysis does , substrate level phosphorylation occur?
Reaction 7:1,3- bisphosphoglycerate to 3-phosphoglycerate
Reaction 9: Phosphoenolpyruvate (PEP) to Pyruvate
What are the Irreversible steps in Glycolysis?
Hexokinase/Glucokinase - ( Glucose- Glucose-6- phosphate)
Phosphofructokinase 1 (PFK-1) - Fructose 6-phosphate to fructose 1,6- bisphosphate
Pyruvate Kinase - PEP - Pyruvate
What happens in the Energy Investment phase of Glycolysis?
Phosphorylation of glucose and its conversion to Glyceraldehyde -3- phosphate
What happens in the Energy Pay off stage?
Oxidative Conversion of glyceraldehyde 3-phosphate to pyruvate and the coupled formation of ATP and NADH
In what type of muscle fibres are there few mitcohondria?
Fast Twitch muscle fibres - Sprinters
In what organs do Gluconeogenesis occur?
In the liver & kidney ( Proximal convoluted tubules)
What is Gluconeogenesis?
It is the process by which glucose molecules are produced from non-carbohydrate precursors.
When does Gluconeogenesis occur?
~ In a hypoglycaemic state
~ Also used for the brain
What’s the amount of glucose needed for brain fuel per day?
120g/day
In Gluconeogenesis, What is the name of the enzyme that converts glucose-6 phosphate to glucose?
Glucose -6- phosphatase
In Gluconeogenesis, What is the name of the enzyme that converts fructose 1,6-bisphosphate to glucose?
Frcutose -6- bisphosphotase
Where is the enzyme glucose -6-phosphotase found?
In the liver & kidney
What are the energy requirements for Gluconeogenesis?
4 ATP, 2 GTP, 2NADH
Which substances can be described as Glucogenic( any substance that can be turned into Pyruvate)?
Glucose
Alanine
Lactate
Glycerol
How do glucogenic amino acid( substrate of Glucogeneisis) help with the formation of Pyruvate?
Glucogenic amino acids are transaminated to corresponding carbon skeletons. These then enter the TCA cycle and form oxaloacetate or pyruvate.
How does glycerol ( substrate of Glucogeneisis) help with the formation of Pyruvate?
The glycerol part of fat is phosphorylated in the liver cytosol by ATP to glycerol-3-phosphate. It is then oxidized to dihydroxy acetone phosphate by an NAD+ dependent dehydrogenase
How does lactate( substrate of Glucogeneisis) help with the formation of Pyruvate?
The lactate formed in the muscle is transported to the liver. In the liver cell lactate dehydrogenase converts lactate to pyruvate. The pyruvate enters the gluconeogenic pathway to form glucose.
Fill in the blanks. “ _______ is an activator for the enzyme Pyruvate carboxylase.”
Acetyl CoA
What substance can inhibit Gluconeogenesis?
Ethanol
What is the storage form of Carbohydrates?
Glycogen
What can be used to prevent lactic acid build up in the body?
The Cori cycle
What is another name for the Glucose-Alanine cycle?
The Cahill cycle
Describe the processes of the Glucose Alanine cycle?
*Alanine is transported to liver, transaminated to pyruvate and converted to glucose.
*This glucose may again enter the glycolytic pathway to form pyruvate, which in turn, can be transaminated to alanine.
~ Glucose-alanine cycle is important in conditions of starvation . Thus net transfer of amino acid (nitrogen) from muscle to liver and corresponding transfer of glucose (energy) from liver to muscle is effected.
Where is glycogen stored?
In the liver and muscle
True or False? The liver does not use its own stored glucose for ATP generation.
TRUE!!
What is the glycogen content in liver and muscle?
Liver- 10% (10 gm/100 gm)
Muscle - 2% (1–2 gm/100 gm)
Fill in the blank. “_________is the central metabolite in the synthesis and decomposition of glycogen.”
Glucose-6-phosphate
Who studied the role of cyclic AMP as the second messenger in glycogenolysis?
Earl Sutherland
Which enzyme removes emoves glucose as glucose-1-phosphate from glycogen
Glycogen phosphorylase
What is the function of the Debranching enzyme?
It releases free glucose from α(1 → 6) bonds at the branch points.
What is the substrate for Glycogenisis?
Uridine diphosphate (UDP) glucose.
What is the debranching enzyme?
alpha- 1,6- glucosidase
What is the debranching enzyme?
alpha- 1,6- glucosidase
What substances can activate the enzyme Glycogen phosphate?
Glucagon
Cyclic AMP
Epinephrine
Calcium
What is the Type I storage disease?
Von Gierke disease
Which type of Storage disease is caused by a deficiency in the Debranching enzyme?
Type III - Cori / Forbes disease
What type of Storage disease is cause by a deficiency in Branching enzyme?
Anderson’s disease ( Type IV)
‘ Anderson is on a branch’
Type II storage disease is known as and what is its deficiency of?
Pompe’s disease- deficiency of Acid maltase
What cofactor is involved in the catalytic mechanism of glycogen phosphorylase?
Pyridoxyl phosphate
Where does the Pentose Phosphate pathway occur?
Occurs in the cytosol
What is the function of the Pentose Phosphate Pathway?
*Formation of NADPH for synthesis of fatty acids, steroids.
* Maintaining reduced glutathione for antioxidant activity.
* Synthesis of ribose for nucleotide and nucleic acid formation.
What are the end products of the HMP shunt?
2 NADPH (net)
Glyceraldehyde -3- phosphate
Fructose-6-phosphate
ribose-5-phosphate
What are the two phases of the Pentose Phosphate Pathway?
Oxidative phase (irreversible)
Non-Oxidative phase(reversible)
True or False? The oxidative phase of PPP produces NADPH.
TRUE!!
Fill in the blank. “ The non-oxidative stage produces ______”
Ribose- 5- phosphate
What is the regulatory enzyme in the Pentose Phosphate pathway?
Glucose-6-phosphate dehydrogenase
Which enzyme in the non-oxidative phase of the Pentose phosphate pathway is dependent on thiamine pyrophosphate (TPP)
Transketolase
Which enzyme converts Ribulose- 5-phosphate to Xylulose-5- phosphate
Epiremase
Which enzyme converts Ribulose -5-phosphate to Ribose-5-phosphate?
Isomerase
Which organs are associated with Steroid synthesis?
Adrenal gland, Testes , Ovaries
Which organs are associated with Fatty acid synthesis?
Liver,Adipose Tissue , Mammory gland
Which part of the body is associated with the maintenance of reduced glutathione
Red blood cells
What substances make up Glutathione?
Glutamate, cysteine and glycine.
