Metabolism Overview

Metabolism Overview

What is Metabolism?

  • Definition of Metabolism: A set of chemical reactions in living organisms that sustain life.

  • Functions:

    • Facilitates growth.

    • Maintains homeostasis.

    • Enables reproduction.

    • Allows adaptation to the environment.

  • Types of reactions:

    • Anabolic Reactions: Build complex molecules from simpler ones.

    • Catabolic Reactions: Break complex molecules into simpler ones, releasing energy.

Major Metabolic Pathways

  • Substrates:

    • Fats: Broken down into fatty acids and glycerol.

    • Polysaccharides: Broken down into glucose and other sugars.

    • Proteins: Broken down into amino acids.

  • Stages of Metabolism:

    • Stage I: Fatty acids and other sugars are converted.

    • Stage II: Conversion to Acetyl CoA and entry into the Citric Acid Cycle.

    • Stage III: Electrons are transferred to O2 via oxidative phosphorylation, producing ATP and H2O.

The Truth About Metabolism

  • Commonalities:

    • All organisms share common metabolic pathways.

    • Limited number of molecules involved across pathways.

    • Shared classes of chemical reactions.

    • Simple mechanisms of reactions.

    • Similar process control points.

  • Conservation: What enters the system must eventually be expelled.

Catabolism

  • Characteristics:

    • Degradation reactions that produce energy.

    • Reduce molecular complexity.

    • Example Reaction: Convert fuels (carbohydrates, fats) into CO2, H2O, and energy.

  • Gibbs Free Energy ( \u0394G'):

    • Typically negative in catabolic reactions.

  • Examples include:

    • Carbohydrate degradation.

    • Amino acid degradation.

    • Fatty acid degradation.

Anabolism

  • Characteristics:

    • Synthesis reactions that require energy.

    • Create complexity and energy-rich substrates.

    • Reaction Example: Useful energy + Simple precursors = Complex molecules.

  • Gibbs Free Energy ( \u0394G'):

    • Generally positive in anabolic reactions.

  • Examples include:

    • Amino acid synthesis.

    • Fatty acid synthesis.

ATP and Energy Transfer

  • Key Components:

    • Simple molecules: Glucose, amino acids, and glycerol.

    • Energy storage and transfer through ATP.

  • Processes:

    • Catabolic reactions transfer energy from complex molecules to ATP.

    • ATP can be converted to ADP and inorganic phosphate (P).

    • Energy is also released as heat.

Oxidation and Reduction in Metabolism

  • Biological Oxidation: Involves loss of hydrogen atoms/electrons (dehydrogenation).

  • Reduction: Involves gain of hydrogen atoms/electrons, increasing energy potential.

  • Coenzymes that facilitate these processes:

    • NAD (Nicotinamide adenine dinucleotide)

    • NADP (Nicotinamide adenine dinucleotide phosphate)

    • FAD (Flavin adenine dinucleotide)

Carbohydrates

  • Definition: "Hydrates of carbon."

  • Types:

    • Monosaccharides, disaccharides, trisaccharides, oligosaccharides, and polysaccharides.

  • Functions:

    • Energy storage.

    • Provide fuel and metabolic intermediates.

    • Structural components of biomolecules.

Carbohydrate Structures

  • Monosaccharides: Characterized by carbon count:

    • Tri – 3 carbons.

    • Tetr – 4 carbons.

    • Pent – 5 carbons.

    • Hex – 6 carbons.

    • Hept – 7 carbons.

  • Structure: Mostly contain an OH group, and the last carbon has either an aldehyde or ketone group.

Fischer Projection

  • Characteristics:

    • Carbon chain represented vertically; horizontal lines indicate bonds projecting towards the viewer.

    • C1 is always at the top; cannot rotate within the plane of the page.

    • Creates enantiomers (non-superimposable mirror images).

Stereochemistry

  • Highest numbered stereocenter indicates the configuration (D or L designation):

    • If it resembles D-glyceraldehyde, it’s denoted as D.

Cyclic Sugars

  • Cyclic Structures:

    • Pyran and furan forms of sugars exist; examples include D-glucopyranose and D-fructofuranose.

Glycosidic Linkages

  • Formation of glycosidic bonds involves 'locking' the anomeric configuration.

  • Non-reducing and reducing sugars are characterized based on linkage types (example: lactose, sucrose).

Polysaccharides

  • Examples include:

    • Cellulose: Composed of beta-1,4 linkages.

    • Starch and Glycogen: Composed of alpha-1,4 linkages with branching.

  • Glycogen structure includes multiple linkage types (alpha-1,6 for branching).

Carbohydrate Metabolism Summary

  • Key processes:

    • Glycogenesis: Formation of glycogen from glucose.

    • Glycogenolysis: Breakdown of glycogen.

    • Pentose phosphate pathway: Converts glucose for nucleotide synthesis.

    • Gluconeogenesis: Formation of glucose from non-carbohydrate sources.

    • Glycolysis: Breakdown of glucose to pyruvate.

    • Citric Acid Cycle and Electron Transport Chain: Final ATP production.

Conclusions

  • Metabolism consists of energy-yielding and energy-requiring reactions.

  • Catabolic processes degrade macromolecules while yielding ATP.

  • Anabolic processes utilize energy to construct complex molecules from simpler ones.