Cellular Metabolism and Macromolecules

Introduction to Small Molecules and Macromolecules

• Small molecules and macromolecules are key components of cellular biochemistry.
• Understanding small molecules is essential to synthesizing macromolecules, which are abundant in cells.
• The study of energy in cellular metabolism sets up the discussion of macromolecules.

Energy in Cellular Metabolism

• Cellular Metabolism consists of biochemical reactions within cells.
• Organized into two main processes: Catabolism (breaking down larger molecules) and Anabolism (building more complex molecules).
• Energetically favorable reactions correspond with oxidation processes in catabolism.
• Energetically unfavorable reactions are linked with reduction processes in anabolism.

Activated Carrier Molecules

• Activated carrier molecules temporarily store energy for biosynthetic processes.
• Examples include ATP, NADH, and NADPH:
  • ATP (Adenosine Triphosphate): Energy currency of the cell; releases energy upon hydrolysis to ADP (Adenosine Diphosphate) by breaking the high-energy phosphoanhydride bond.
  • NADH: Involved in cellular respiration and catabolic reactions that generate ATP.
  • NADPH: Primarily involved in biosynthetic (anabolic) processes that require reducing power.
• Acetyl CoA is both an activated carrier and a hub in cellular metabolism, derived from the metabolism of amino acids, fatty acids, and carbohydrates.

Biosynthetic Processes

• Biosynthesis: The formation of complex molecules from simpler ones, requiring energy.
• Examples:
  • Formation of glycogen from glucose molecules.
  • Conversion of glutamic acid to glutamine, which requires input energy from ATP.

Mechanisms of Protein Synthesis

• Peptide Bonds: Formed between the amino group of one amino acid and the carboxyl group of another, creating a polypeptide chain.
• Proteins can have complex structures bridged by non-covalent interactions (hydrogen bonding, ionic bonds) leading to:
  • Primary Structure: The amino acid sequence.
  • Secondary Structure: Common folding patterns (alpha helices and beta sheets) held together by hydrogen bonds.
  • Tertiary Structure: The overall three-dimensional shape, stabilized by numerous interactions.
  • Quaternary Structure: Interaction between multiple polypeptide chains or proteins.

Protein Structure and Function

• The structure of a protein directly relates to its function. Changes in shape can affect binding to ligands and biological activity.
• Classification of proteins:
  • Fibrous Proteins: For structural functions (e.g., collagen).
  • Globular Proteins: Spherical and often enzymatic in function (e.g., enzymes).
• Denaturation: The process of unfolding proteins, which can be triggered by changes in environmental conditions like pH.

Summary

• The interconnectedness of small molecules, activated carriers, and macromolecules forms the basis of cellular metabolism.
• Understanding energy transfer and biosynthesis processes is essential for comprehending metabolic pathways.
• Proteins are central to these processes, with their structure intricately linked to their diverse biological functions, facilitated by their ability to adopt various conformations and interact with other cellular components.