GLUCOSE PATHWAYS! - NOV14

Engaging conversation at the beginning.
Mention of caffeine drinks, specifically a flat white with four shots of espresso.

Discussion begins with glucose's entry into the bloodstream through the hepatic portal system, reaching the liver.
Blood sugar levels rise, leading to insulin release from the pancreas.

Definition: Insulin is a hormone that regulates blood glucose levels.
Insulin rises in response to increased blood glucose to facilitate glucose uptake by cells.
Glucose is a polar molecule; it cannot diffuse into cells and requires transport proteins or receptors.

Explanation of glucose transport mechanisms through GLUT receptors in response to insulin.
Discussion about insulin resistance and the need for higher insulin levels to achieve glucose uptake.

Upon entering the cell, glucose serves two main purposes: production of energy or storage.
Metabolism Overview: - Breakdown of complex carbohydrates into simple sugars.
- Anabolic vs Catabolic Processes:
- Catabolic pathway: breaks larger molecules into smaller ones, producing energy.
- Anabolic pathway: synthesizes larger molecules from smaller ones, consuming energy.

Cells manage resources akin to budgeting in a household.
Immediate needs determine whether glucose is used immediately or stored as glycogen for future use.

A series of linked reactions ranging from smaller to larger molecules (anabolic) or larger to smaller (catabolic).
Pathways can be linear, circular, or branched.

Glycogenesis: Conversion of glucose to glycogen (anabolic).
Glycolysis: Breakdown of glucose to pyruvate, producing ATP (catabolic).
Routes of glucose management in cells: Catabolic pathways lead to energy production, while anabolic pathways lead to energy storage.

Glycogen: Storage form of glucose in animals, primarily in the liver and muscles.
Stored as a branched polymer with structures comprised mainly of alpha-1,4 and alpha-1,6 glycosidic linkages.

Pyruvate is the end product of glycolysis from glucose.
The process includes two phases: investment and payoff.
Investment Phase: Investment of energy (ATP) to prepare glucose for breakdown.
Payoff Phase: Production of ATP and pyruvate from glucose.

Glucose to glucose-6-phosphate: Catalyzed by hexokinase (requires ATP).
- Hexokinase's Role: A transferase that adds phosphate.
Isomerization to fructose-6-phosphate.
- Enzyme Used: An isomerase converts glucose-6-phosphate to fructose-6-phosphate.
Fructose-1,6-bisphosphate creation: From fructose-6-phosphate via phosphofructokinase, utilizing ATP (rate-limiting step of glycolysis).
Cleavage into two three-carbon molecules: Producing two glyceraldehyde-3-phosphate (G3P) molecules.
Convert G3P to pyruvate via a series of reactions, yielding ATP.

Glycogenesis is initiated by glucose molecules linking to glycogenin.
Enzymes Involved:
- Glycogen synthase: Responsible for adding glucose (linking primarily alpha-1,4).
- Branching enzyme: Creates branch points (alpha-1,6 linkages).

Glycogenin acts as a primer for glycogen synthesis, catalyzing the first glycosidic bond.

The breakdown of glycogen into glucose is termed glycogenolysis.
Enzyme involved: Glycogen phosphorylase, which cleaves glucose units off glycogen chain.
Converts glucose from glycogen to glucose-1-phosphate, which is then converted to glucose-6-phosphate (then potentially routed to glycolysis).

Glycogenesis and glycogenolysis are tightly regulated processes.
Understand reciprocal regulation of enzymes to maintain energy balance in the body.
The integration of pathways discussed explains how glucose and energy are managed effectively in cells.