Understanding Biological Molecules: Amino Acids, Proteins, and Genetic Code

Posted on May 1, 2024 in Biology

B1OA: Amino Acids and Proteins

1. Amino Acid Structure

Amino acids are organic molecules containing an amino group (-NH2) and a carboxyl group (-COOH). These functional groups give amino acids their characteristic properties.

2. Protein Structure and Stability

Proteins fold into specific three-dimensional structures, stabilized by various interactions, including:

  • Ionic bonds
  • Hydrogen bonding
  • Van der Waals forces
  • Disulfide bonds
  • Hydrophobic interactions

The stability of a protein’s structure is crucial for its function.

3. Protein Denaturation

Denaturation is the loss of a protein’s native structure, often caused by factors like high temperature, extreme pH changes, or certain chemicals. Denatured proteins lose their functionality.

4. Types of Proteins

Proteins are classified based on their functions:

  • Structural proteins: Provide shape and support to cells and tissues (e.g., keratin).
  • Storage proteins: Store amino acids for later use (e.g., albumin).
  • Active proteins: Perform various functions, including enzymes, transport proteins, regulatory proteins, contractile proteins, and immune proteins.

B2OA: Mitochondria and Cellular Respiration

1. Mitochondrial Structure

Mitochondria are organelles with two membranes: a smooth outer membrane and a folded inner membrane called the cristae. The cristae increase the surface area for cellular respiration.

2. Role of Mitochondria in Respiration

Mitochondria are the sites of cellular respiration, where energy is extracted from glucose and other molecules to produce ATP. The Krebs cycle and fatty acid oxidation occur within mitochondria.

3. Importance of Mitochondria

Mitochondria are essential for eukaryotic cells as they generate most of the cell’s ATP, the energy currency of life.

B3OB: Viruses and Genetic Material

1. Types of Genetic Material

Genetic material can be classified as:

  • Chromosomal DNA
  • Plasmids
  • Viral genomes

2. Viruses and Prions

Viruses are infectious agents that infect cells and replicate using the host cell’s machinery. Prions are misfolded proteins that can cause neurodegenerative diseases.

  • Bacteriophages: Viruses that infect bacteria.
  • RNA viruses: Viruses with RNA as their genetic material.
  • Prions: Misfolded proteins that can cause diseases like Creutzfeldt-Jakob disease.

3. Viral Replication Cycles

Viruses can replicate through two main cycles:

  • Lytic cycle: The virus infects the host cell, replicates, and destroys the host cell to release new virus particles.
  • Lysogenic cycle: The virus integrates its genetic material into the host cell’s DNA, remaining dormant until it enters the lytic cycle.

B4OA: Genetic Code and Gene Expression

1. The Genetic Code

The genetic code is a set of rules that determines how nucleotide sequences in DNA are translated into amino acid sequences in proteins. Each three-nucleotide sequence (codon) codes for a specific amino acid.

2. Genes and Codons

A gene is a segment of DNA that contains the instructions for making a protein or RNA molecule. Codons are three-nucleotide sequences within a gene that specify amino acids.

  • Gene: A sequence of nucleotides on a chromosome that codes for a specific protein or RNA molecule.
  • Codon: A three-nucleotide sequence that codes for an amino acid or a stop signal.

3. Mutations

Mutations are changes in the genetic material of an organism. They can occur at the chromosome level, affecting chromosome number or structure, or at the gene level, altering the DNA sequence.

  • Chromosomal mutations: Changes in chromosome number or structure (e.g., aneuploidy, deletions, duplications).
  • Gene mutations: Changes in the DNA sequence of a gene (e.g., substitutions, insertions, deletions).