Biochemistry: Hydrolysis and Condensation Reactions

Hydrolysis Reactions

• Break down complex molecules into simpler ones.
• Involve adding a water molecule to split a bond.
• Purpose: Decompose polymers into monomers, making them available for biological processes.

Condensation or Dehydration Reactions

• Join two molecules together.
• Involve releasing a water molecule.
• Purpose: Synthesize larger molecules (polymers) from smaller ones (monomers).
• Key in forming macromolecules like proteins, nucleic acids, and carbohydrates.

Polymer and Monomer

• Polymer: A large molecule made up of repeating subunits.
• Monomer: A small, single molecule that can join with others to form a polymer.
• Relationship: Monomers are the building blocks of polymers.

Building and Breaking Polymers

• Condensation reactions: Add monomers to lengthen polymers.
• Hydrolysis reactions: Remove monomers to shorten polymers.

Carbohydrates

• Monomers: Monosaccharides (simple sugars, e.g., glucose).
• Polymers: Polysaccharides (complex carbohydrates).
• Monosaccharide Function: Primary energy source for living organisms.

Polysaccharide Types

• Storage: Store energy (e.g., starch in plants, glycogen in animals).
• Structural: Provide support (e.g., cellulose in plants).

Storage Polysaccharides

• Plants: Starch (amylose and amylopectin).
• Animals: Glycogen.

Starch Components

• Amylose: Linear polymer of glucose (unbranched).
• Amylopectin: Branched polymer of glucose.

Structural Polysaccharide

• Plants: Cellulose.

Sugar Isomers

• Sugars with the same molecular formula but different structural arrangements.
• Example: Glucose and fructose (both C6H12O6).

Glycosidic Bond

• The covalent bond that links two sugars together.

Amylases and Maltases

• Amylases: Break down starch into smaller sugars (e.g., maltose).
• Maltases: Break down maltose into glucose.
• Breakdown Products: Simpler sugars (maltose, glucose).
• Production: Amylases in saliva and pancreas; maltase in the small intestine.

Proteins

• Monomers: Amino acids.
• Polymers: Polypeptides or proteins.
• Peptide Bond: Covalent bond linking amino acids.

Amino Acid Structure

• Central carbon atom with three attached groups: amino group, carboxyl group, and side chain.
• Difference: Variation in the side chains determines amino acid properties.
• Number: 20 standard amino acids.

Amino Acid Groups

• Based on side chain chemistry.
• Ability to determine group membership given an amino acid structure.

Protein Structure and Function

• Closely linked.
• Structure: Specific arrangement of amino acids determines protein shape.
• Function: Protein's shape dictates how it interacts with other molecules.

Levels of Protein Structure

• Primary: Sequence of amino acids (peptide bonds).
• Secondary: Folding/coiling into structures like alpha helices or beta sheets (hydrogen bonds).
• Tertiary: Overall 3D shape of a single polypeptide chain (hydrogen bonds, ionic bonds, disulfide bridges, hydrophobic interactions).
• Quaternary: Arrangement of multiple polypeptide chains (subunits) into a single functional protein (same bonds as tertiary).

Denaturation

• Process where a protein loses its native structure.
• Impact: Loss of biological function.
• Causes: Changes in temperature, pH, exposure to chemicals.

Nucleic Acids

• DNA: Stores genetic information.
• RNA: Involved in protein synthesis and gene regulation.

Nucleic Acid Structure

• Monomers: Nucleotides.
• Polymers: Nucleic acids.
• Phosphodiester Bond: Covalent bond linking nucleotides.

Polynucleotide Structure

• Ends: 5' end (phosphate group) and 3' end (hydroxyl group).
• Bond: Hydrogen bonds hold two strands of DNA together.

Nucleotide Components

• Phosphate group, sugar, nitrogenous base.
• Difference: Variation in the nitrogenous base.

DNA Bases

• Adenine (A), guanine (G), cytosine (C), thymine (T).

RNA Bases

• Adenine (A), guanine (G), cytosine (C), uracil (U).

DNA Structure

• Double helix with two strands of nucleotides running in opposite directions.
• Base Pairing: Adenine pairs with thymine (A-T); cytosine pairs with guanine (C-G).

RNA vs DNA

• Similarities: Both are made of nucleotides and can form structures.
• Differences: RNA is typically single-stranded, has ribose sugar, and contains uracil instead of thymine.

Lipids

• Characteristic: Hydrophobic or amphipathic (do not mix well with water).

Fats

• Composed of glycerol and fatty acids.
• Official Name: Triglycerides.
• Saturated: No double bonds between carbon atoms (solid at room temperature).
• Unsaturated: One or more double bonds (liquid at room temperature).

Phospholipids

• Hydrophilic "head" (phosphate group) and two hydrophobic "tails" (fatty acids).
• Function: Form the bilayer of cell membranes, allowing for compartmentalization.

Fat vs Phospholipid

• Fat: One glycerol and three fatty acids.
• Phospholipid: One glycerol, two fatty acids, and a phosphate group.

Steroids

• Lipids with characteristic four-ring structure.
• Function: Cholesterol: Maintains membrane fluidity in cell membranes.

Cell Organelles

• Nucleus: Contains genetic material; surrounded by a nuclear envelope with pores.
• Ribosomes: Sites of protein synthesis (RNA and proteins).
• Endoplasmic Reticulum (ER):
  • Rough ER: Studded with ribosomes; involved in protein synthesis and processing.
  • Smooth ER: Synthesizes lipids and detoxi es harmful substances.

Membrane Transport (Diffusion & Osmosis)

Plasma Membrane Permeability

• Easy Passage: Small nonpolar molecules (oxygen, carbon dioxide), lipid-soluble substances.
• Difficult Passage: Large polar molecules (glucose), ions (Na+, K+).
• Transport Proteins: Required for molecules unable to freely pass.

Transport Protein Types

• Channel Proteins: Form pores for specific ions or water to pass through.
• Carrier Proteins: Bind to specific molecules and change shape to transport them.

Diffusion

• Movement of solutes from high concentration to low concentration until evenly spread.
• Energy Requirement: Diffusion is passive; no energy input required.
• Simple Diffusion: Diffusion across a biological membrane without assistance.

Osmosis

• Diffusion of water across a semipermeable membrane.
• Water Movement: Towards the area of higher solute concentration.

Tonicity

• Comparison of solute concentration between a solution and a cell:
  • Isotonic: Equal solute concentration; no net water movement.
  • Hypertonic: Higher solute concentration outside the cell; water moves out of the cell (cell shrinks).
  • Hypotonic: Lower solute concentration outside the cell; water moves into the cell (cell swells and may burst).

Facilitated Diffusion

• Movement of molecules across a membrane with the help of transport proteins.
• Passive Process: Does not require energy.
• Specificity: Transport proteins bind to specific molecules.