Notes on Biomolecules

9.1 How to Analyze Chemical Composition

There is diverse life in the biosphere; a central question is whether all organisms are composed of the same chemicals. Elemental analysis can be performed on various living and non-living tissues, revealing common elements such as carbon, hydrogen, and oxygen. While both living and non-living samples contain similar elements, their relative abundances differ.

Key Points:

• Elemental Analysis: Reveals the composition of living and non-living tissues, highlighting the prevalence of certain elements.
• Living Organisms vs. Earth's Crust: Higher relative abundance of carbon and hydrogen in living organisms compared to non-living sources.
• Extraction Process: Tissue is ground in trichloroacetic acid for chemical analysis, yielding filtrate (acid-soluble) and retentate (acid-insoluble).

9.2 Primary and Secondary Metabolites

Biomolecules can be categorized into primary metabolites (essential compounds for growth and reproduction) and secondary metabolites (not essential but have ecological functions).

Examples:

• Primary Metabolites: Amino acids, sugars, nucleotides.
• Secondary Metabolites: Alkaloids, flavonoids, essential oils.

Secondary metabolites can play roles in plant defense and provide benefits to humans, such as drugs and flavors.

9.3 Biomacromolecules

Biomolecules are classified into two categories based on size:

1. Micromolecules: (molecular weight < 1000 Da) such as amino acids and sugars.
2. Biomacromolecules: (molecular weight > 10,000 Da) including proteins, nucleic acids, polysaccharides, and some lipids.

Key Points:

• Macromolecules: Proteins, nucleic acids, polysaccharides; lipids are categorized separately due to their complex structures.
• Chemical Composition of Living Tissues: Most abundant components include water, proteins, carbohydrates, lipids, nucleic acids, and ions.

9.4 Proteins

Proteins are polymers made of 20 different amino acids. They serve numerous functions including catalysis (as enzymes), structure, transport, signaling, and defense.

Protein Structure:

• Primary Structure: Sequence of amino acids.
• Secondary Structure: local folding into alpha-helices and beta-sheets.
• Tertiary Structure: overall 3D shape due to interactions among R groups.
• Quaternary Structure: arrangement of multiple polypeptide chains.

9.5 Polysaccharides

Polysaccharides are long chains of sugar molecules. Major types include:

• Cellulose: Found in plant cell walls.
• Starch and Glycogen: Energy storage polysaccharides in plants and animals, respectively.
• Chitin: A structural polysaccharide found in arthropod exoskeletons.

9.6 Nucleic Acids

Nucleic acids (DNA and RNA) are polymers of nucleotides. Each nucleotide consists of a nitrogenous base, a sugar, and a phosphate group.

Key Points:

• DNA: Contains deoxyribose sugar; carries genetic information.
• RNA: Contains ribose sugar; plays roles in protein synthesis.

9.7 Structure of Proteins

Understanding protein structure is crucial for understanding their function. The specific folding and assembly of proteins into their structural forms (primary, secondary, tertiary, and quaternary) determine their activities within cells.

9.8 Enzymes

Enzymes are proteins that catalyze biochemical reactions, significantly increasing reaction rates. They can work under optimal conditions of temperature and pH.

Key Concepts:

• Active Site: Region of the enzyme where substrates bind to facilitate reactions.
• Catalytic Cycle: Enzymes convert substrates into products through a series of states, lowering the activation energy required for reactions.

Factors Affecting Enzyme Activity:

1. Temperature: Each enzyme has an optimum temperature range.
2. pH Levels: Enzymes also have specific pH levels at which they function best.
3. Substrate Concentration: Reaction rates increase with substrate concentration up to a point of saturation.

Enzyme Classification:

Enzymes are classified based on reaction types into six major categories, which include oxidoreductases, transferases, hydrolases, lyases, isomerases, and ligases.

Cofactors:

Many enzymes require additional non-protein components called cofactors for activity, including metal ions and organic molecules (coenzymes).

Summary

Living organisms share similar biomolecular compositions, consisting mainly of biomacromolecules such as proteins, nucleic acids, and polysaccharides, all of which have vital roles in biological functions. Enzymes, a subset of proteins, are crucial for facilitating biochemical reactions and are characterized by their specificity and sensitivity to environmental factors.

1. Elemental Analysis shows similar elemental composition in living and non-living tissues but different abundances.
2. Primary Metabolites are essential for growth, while Secondary Metabolites have ecological roles.
3. Biomolecules are categorized as micromolecules (small) and biomacromolecules (large).
4. Proteins serve various functions and have four levels of structure: primary, secondary, tertiary, and quaternary.
5. Polysaccharides include cellulose (structural), starch, and glycogen (energy storage).
6. Nucleic Acids (DNA and RNA) are polymers of nucleotides important for genetic information.
7. Enzymes are proteins that catalyze biochemical reactions and are specific to substrates.
8. Enzyme activity is affected by temperature, pH, and substrate concentration.
9. Enzymes are classified into six main categories based on the reactions they catalyze.
10. Cofactors are often necessary for enzyme activity, enhancing catalytic effectiveness.