Metabolism Overview Quiz

Study Notes

Overview of Metabolism & Metabolic Pathways

Anabolic pathways construct larger molecules from smaller ones, consuming energy in the process.
Catabolic pathways break down molecules into smaller units, releasing energy.
Amphibolic pathways integrate both anabolic and catabolic processes, facilitating metabolic flexibility.

Metabolism of Major Nutrients

Carbohydrate metabolism occurs primarily in the liver, involving breakdowns and conversions at the tissue and subcellular levels.
Lipid metabolism is crucial for energy storage and release, facilitated by enzymes in adipose tissue and the liver.
Amino acid metabolism plays a vital role in protein synthesis and energy production, occurring in various tissues.

Regulation of Metabolic Flux

Metabolic pathways are regulated through feedback mechanisms, enzyme activity modulation, and substrate availability.
Hormones like insulin and glucagon play significant roles in regulating the flow of metabolites.

Metabolic Fuels Supply in Fed and Fasting States

In the fed state, carbohydrates, lipids, and proteins are digested and stored as metabolic reserves.
During fasting, the body mobilizes stored fuels to maintain energy balance, utilizing glycogen and fat stores.

Digestion and Absorption of Carbohydrates

Major dietary carbohydrates include starch, sucrose, and lactose.
Key sites for carbohydrate digestion:
- Mouth: Salivary enzyme a-Amylase initiates starch breakdown into shorter polysaccharides.
- Stomach: Low pH halts salivary amylase activity.
- Small Intestine:
  - Pancreatic a-Amylase further breaks down polysaccharides and disaccharides.
  - Membrane-bound enzymes such as maltase, lactase, and sucrase at intestinal cell walls convert disaccharides to monosaccharides (glucose, fructose, galactose).
- Portal Circulation: Monosaccharides are absorbed into the bloodstream, transported to the liver.
- Liver: Processes carbohydrates for energy use, storage, or metabolic pathways.

Enzyme Function in Carbohydrate Digestion

Endoglycosidases: Hydrolyze internal glycosidic bonds in polysaccharides and oligosaccharides.
Disaccharidases: Split disaccharides into their constituent monosaccharides.

Key Points about Carbohydrate Digestion Sites and Enzymes

Digestion begins in the mouth and is completed in the small intestine.
The small intestine's functional enzymes finalize carbohydrate breakdown, allowing efficient absorption into the bloodstream.

Description

Test your understanding of metabolic pathways, including anabolic, catabolic, and amphibolic processes. This quiz covers the metabolism of carbohydrates, lipids, and amino acids, along with the regulation of metabolic flux and the provision of metabolic fuels. Perfect for students studying biochemistry or related fields.