LBM

There are four types of large biological molecules:
1. Carbohydrates - Polymer
2. Lipids - Not Polymers
3. Nucleic Acids - Polymer
4. Proteins - Polymer (made up of amino acids)

LBMs are primarily carbon-based.
Functional groups include hydroxyl (-OH), carbonyl (C=O), carboxyl (-COOH), amino (-NH₂), phosphate (-H₂PO₄), and sulfhydryl (-SH).
Behavior in water:
- Hydrophilic: water-loving molecules.
- Hydrophobic: water-fearing molecules.
- Amphipathic: molecules that have both hydrophilic and hydrophobic regions.

LBMs are synthesized by dehydration reactions:
- Example:
  $A-OH + OH-B \to A-O-B + H_2O$
- Enzyme-catalyzed (e.g., polymerase, synthase).
- Condensation reactions are another name for these processes.
LBMs are broken down by hydrolysis reactions:
- Example:
  $A-O-B + H_2O \to A-OH + OH-B$
- Enzyme-catalyzed (e.g., hydrolase).

Three of the four large molecules are polymers, while lipids are not polymers.
Polymers are molecules made by joining multiple similar subunits known as monomers.
Polymers can be very large and are also referred to as macromolecules.

Monomer: Monosaccharide (simple sugar)
Common monosaccharides include:
- Glucose (C₆H₁₂O₆) - main monosaccharide
- Ribose and Deoxyribose (5C sugars)
- Fructose, Galactose (and other 6C sugars)
- All monosaccharides end in -ose.

Carbonyl groups are found in sugars.
Types based on carbonyl group location:
- Aldose: carbonyl group on an end carbon (e.g., glucose).
- Ketose: carbonyl group on an internal carbon (e.g., fructose).
Arrangement of functional groups is critical for biological activity.

Formed by linking two monosaccharides:
- Examples:
- Maltose: glucose + glucose.
- Sucrose: glucose + fructose.
- Lactose: galactose + glucose (requires enzyme lactase).

Functions:
- Energy storage
- Starch: found in plants, polymers of glucose; stored in granules in chloroplasts.
- Glycogen: found in animals, also polymers of glucose; mostly stored in liver and muscle.
- Structural:
- Cellulose: main component of plant cell walls, polymers of glucose.
- Chitin: found in fungal cell walls and arthropod exoskeletons, polymers of modified glucose.

Not polymers but relatively smaller than other LBMs.
Grouped by their hydrophobic behavior in water.
Diverse groups with various sub-groups, formed from multiple molecules rather than monomers.

Fats (triglycerides)
- Functions:
  - Energy storage
  - Cushioning organs
  - Insulation (subcutaneous fat).
- Structure: Formed from glycerol and three fatty acids (16-18 carbons), which can have:
  - Saturated fatty acids: solid at room temperature.
  - Unsaturated fatty acids: liquid at room temperature (due to double bonds).
Phospholipids
- Functions: Major component of plasma membranes (cell membranes) and intracellular membranes.
- Structure: Composed of glycerol, two fatty acids, and a phosphate group, leading to an amphipathic structure with hydrophilic and hydrophobic regions.
Steroids
- Functions: Essential for maintaining plasma membranes and as steroid hormones.
- Structure: Characterized by four fused carbon rings (e.g., cholesterol in animals, phytosterols in plants, ergosterol in fungi and protozoa).

Two main types of nucleic acids:
- DNA (Deoxyribonucleic acid): involved in information storage.
- RNA (Ribonucleic acid): involved in accessing the information and performing functions based on that information.

Monomer: Nucleotide, which consists of:
1. Sugar (deoxyribose or ribose)
2. Phosphate group
3. Nitrogen-containing base (e.g., adenine, cytosine, guanine, thymine for DNA, uracil for RNA).
Structure of nucleic acids:
- Formed as polynucleotides where many nucleotides are bound in a linear manner creating a sugar-phosphate backbone, with base pairs hanging from the sides.
- Ends: 5' end and 3' end.

The working machines of the cell, serving various roles:
- Enzymes: catalyzing chemical reactions.
- Structural support: providing shape and strength to cells.
- Repair mechanisms: maintaining cellular integrity.
- Signaling molecules and receptors: for cell signaling and recognition.

Monomer: Amino Acid
General Structure of an amino acid:
- Composed of a central alpha carbon, an amino group (-NH₂), a carboxyl group (-COOH), a hydrogen atom, and an R group which represents one of 20 different options.
- Polypeptides are formed when multiple amino acids are linked by peptide bonds.

Primary Structure:
- Linear chain of amino acids from the N-terminal end to the C-terminal end.
Secondary Structure:
- Stabilized by hydrogen bonds between atoms of the polypeptide backbone, resulting in structures such as:
  - Alpha Helix.
  - Beta Pleated Sheet.
Tertiary Structure:
- The final folded shape of the polypeptide, stabilized by interactions among side chains (R groups), including hydrophobic interactions, van der Waals interactions, hydrogen bonds, ionic bonds, and disulfide bridges (covalent bonds between cysteine amino acids).
Quaternary Structure:
- Association of two or more polypeptides to form a functional protein.

Denaturation refers to the unfolding of a protein.
- Example: Cooking an egg disrupts protein structure.
Denaturing agents can stabilize tertiary structure:
- Irreversible factors: Harsh conditions like heat or strong agitation.
- Reversible factors: Gentle conditions, such as ionic or pH changes.
Renaturation: Refolding of a protein back into its functional shape is sometimes possible but not guaranteed.