Ćarbohydrates and glucose metabolism Flashcards
Monosaccharides are (3)
glucose, fructose, galactose
Disaccharides are (3)
lactose (galactose + glucose),
maltose (glucose + glucose),
sucrose (fructose + glucose, non-reducing)
The brain CANNOT - relationship between brain and glucose (3)
- Synthesize glucose
- Store glucose in significant amounts
- Metabolize substrates other than glucose and ketones
Entry of glucose in the brain is not facilitated by _______
insulin
Normal glucose plasma conc.
from PPT: 4-10 mmol/L
Guidelines fasting glucose : 3.5-5.5 mmol/L
What do renal tubular cells do regarding the glucose?
- Renal tubular cells reabsorb almost all of the filtered glucose and little glucose is lost unchanged from the body
Functions of glucagon (3)
- Stimulates production of glucose by glycogenolysis and gluconeogenesis
- It increases ketogenesis in the liver
- It increases lipolysis in adipose tissue
Epinephrine functions (2)
- It stimulates glycogenolysis/glycogen breakdown and decreases use of glucose, increasing its blood concentration
- It stimulates glucagon secretion and inhibits insulin secretion
Growth hormone functions (3)
- It stimulates gluconeogenesis
- It stimulates lipolysis
- It inhibits insulin-stimulated glucose uptake
Cortisol functions (2)
- It stimulates gluconeogenesis
- It stimulates breakdown of protein and fat
Thyroxine functions (not direct) (3)
- It stimulates glycogenolysis
- It stimulates rate of gastric emptying
- It increases glucose intestinal absorption
Somatostatin function
- Somatostatin inhibits secretion of glucagon and insulin by the pancreas
What are ketone bodies?
Water-soluble molecules produced from fatty acids in the liver
What are 3 things that happen when insulin is low in regards to ketone bodies?
- increased lipolysis
- decreased re-esterification of fatty acids to triglycerides
- increased plasma free fatty acids
Increased amount of __________ increases fatty acid oxidation in the liver
glucagon
_______ and ________ lead to acetoacetate accumulation in the blood
increased hepatic ketone production
decreased peripheral tissue metabolism
In severe ___________ ratio of beta-hydroxybutyrate to acetoacetate may increase _________ due to large amount of NADH which favors beta-hydroxybutyrate
diabetes
6:1
What are 2 enzymatic methods of glucose determination?
Hexokinase and
glucose oxidase method
What is Hexokinase method and what are interfering substances?
- 2 reactions, measures increase in absorbance of NADP (it is directly proportional to glucose)
- Interfering substances: RBC esters, bilirubin, triglycerides (500 and up), drugs, fructose
What is glucose oxidase method and what are interfering substances?
- specific for beta-D-glucose, may be coupled with peroxidase indicator reaction or by measuring oxygen consumption using oxygen electrode
- Interfering substances: ascorbic acid, uric acid, bilirubin, haemoglobin, tetracycline, glutathione, galactose, d-xylose
In serum and plasma values are 10-15% _______ than in whole blood
higher
Serum or plasma must be separated within 1h to prevent degradation by _________, glucose is stable for 24h in whole blood when preserved with ______________
glycolysis
sodium fluoride
Serum/plasma fasting glucose values?
Serum/plasma fasting 74-100 mg/dL; CSF 60% of that value
Other methods for detection of glucose are (2)
- Reduction method, which is based on the ability of glucose to reduce Cu++ to Cu+, less sensitive, substances that could reduce Cu++: fructose, galactose, vitamin C, uric acid, etc.
- Enzymatic method (more specific and precise result): Glucose is oxidized by glucose oxidase gluconic acid + H2O2 red dye