Biochemistry and Metabolic Pathways Flashcards
(6 cards)
Gluconeogenesis
G6P is converted by glucose-6-phosphatase during gluconeogenesis to form glucose. Glucose-6-phosphatase is primarily expressed in the liver but also in the kidney cortex at times of starvation. It has further been found to be expressed in the β-cells of pancreatic islets and human intestinal mucosa in starved and diabetic states.
Importance: Gluconeogenesis is an anabolic process whereby glucose is formed from non-carbohydrate carbon precursors including pyruvate. The gluconeogenic pathway largely occurs within the liver and kidneys to maintain blood glucose levels following glycogen depletion, and in the renal cortex during starvation. Gluconeogenesis has also been found to occur within the β-cells of the islets of Langerhans and intestinal mucosa in starved and diabetic states.
Glycogenesis
Storage as glycogen. G6P is converted via glycogen synthase into glycogen for storage.
Importance: Glycogen can be degraded to supply energy to the body. This is specifically important as cells within the brain rely almost entirely on glucose for energy and therefore glucose released from liver cells can help supply this. Within periods of sudden activity, such as sprinting, the glucose obtained from glycogen degradation can produce enough energy when no oxygen is initially available.
The pentose phosphate pathway (PPP)
The generation of NADPH molecules allows fatty acid synthesis. The formation of ribose-5-phosphate to synthesise nucleotides. The PPP regenerates the intermediates of glycolysis such as F6P and glyceraldehyde-3-phosphate (GAP).
Importance: The PPP is an essential biochemical process that occurs within the cytosol of living organisms. This pathway runs parallel to glycolysis in the cytosol, as it utilises some similar components of this pathway for its own use. It is known to have several important roles.
Lipids
Chemically defined as substances that are insoluble in water but are soluble in nonpolar solvents such as acetone. Their insolubility in water is due to the presence of a long hydrophobic, hydrocarbon chain which can be either saturated or unsaturated.
Free fatty acid
Made up of lipids, consists of a carboxyl group (-COOH) linked to a straight chain of carbon atoms bound with hydrogen.
Warburg Effect
Cancer cells preferentially generate energy by aerobic glycolysis, followed by lactic acid fermentation. This is in contrast to normal cells which mainly generate energy through oxidative phosphorylation.
