Macromolecules and Their Building Blocks

Monomers and Polymers

Macromolecules are large biological molecules essential for life, constructed from smaller units called monomers. When monomers join together, they form polymers, which exhibit unique properties and functions in living organisms.

• Monomer: The smallest unit of an organic molecule, such as amino acids, monosaccharides, or nucleotides.

• Polymer: A larger molecule made up of repeating monomer units, e.g., proteins, polysaccharides, nucleic acids.

• Example: Nucleotides are monomers that build DNA polymers.

Hydrolysis and Dehydration Synthesis

Polymers are assembled and broken down by specific chemical reactions. Dehydration synthesis forms polymers by removing water, while hydrolysis breaks polymers into monomers by adding water.

• Dehydration Synthesis: Joins monomers, releasing water as a byproduct.

• Hydrolysis: Splits polymers into monomers, consuming water.

• Equation for Dehydration Synthesis:

• Equation for Hydrolysis:

Carbohydrates: Structure and Function

Types and Roles of Carbohydrates

Carbohydrates are organic molecules composed of sugars, serving as energy sources and structural materials in cells.

• Monosaccharides: Simple sugars (e.g., glucose, fructose) used for energy.

• Disaccharides: Two monosaccharides joined by a glycosidic bond (e.g., sucrose).

• Polysaccharides: Long chains of monosaccharides used for storage (starch, glycogen) or structure (cellulose, chitin).

Structural and Storage Polysaccharides

Polysaccharides differ in their function and structure. Storage polysaccharides (starch, glycogen) are branched, while structural polysaccharides (cellulose, chitin) are linear and provide rigidity.

• Starch: Storage form in plants, found in bulbs, roots, tubers.

• Glycogen: Storage form in animals, stored in liver and muscles.

• Cellulose: Structural component of plant cell walls, composed of β-glucose.

• Chitin: Structural component in fungi and exoskeletons of arthropods, contains nitrogen groups.

Lipids: Structure and Function

Types of Lipids

Lipids are hydrophobic molecules with diverse functions, including energy storage, membrane structure, and signaling.

• Triglycerides: Long-term energy storage, composed of glycerol and three fatty acids.

• Phospholipids: Major component of cell membranes, with hydrophilic heads and hydrophobic tails.

• Cholesterol: Structural component of membranes and precursor for steroid hormones.

• Steroid hormones: Chemical messengers derived from cholesterol.

Dietary Fats

Fats in the diet can be classified as saturated, unsaturated (cis and trans), each affecting health differently.

• Saturated fats: No double bonds, solid at room temperature.

• Unsaturated fats: One or more double bonds, liquid at room temperature.

• Trans fats: Unsaturated fats with trans configuration, associated with health risks.

• Cis fats: Unsaturated fats with cis configuration, generally healthier.

Cholesterol and Steroids

Cholesterol is a precursor for various steroids, including corticosteroids, androgens, sex hormones, sterols, and bile salts.

• Corticosteroids: Used in anti-inflammatory medications.

• Androgens: Promote muscle growth.

• Sex steroids: Regulate reproductive functions.

• Sterols: Help synthesize vitamin D3.

• Bile salts: Aid in digestion.

HDL vs LDL Cholesterol

Cholesterol is transported in the blood by lipoproteins. HDL (high-density lipoprotein) is considered 'good' cholesterol, while LDL (low-density lipoprotein) is 'bad' cholesterol due to its association with cardiovascular risk.

• HDL: Removes cholesterol from arteries.

• LDL: Deposits cholesterol in arteries, increasing risk of atherosclerosis.

Proteins: Structure and Function

Amino Acids and Protein Structure

Proteins are polymers of amino acids, which are joined by peptide bonds. The sequence and properties of amino acids determine protein structure and function.

• Amino Acid Structure: Contains an amino group (N-terminus), carboxyl group (C-terminus), and variable R-group.

• Types of Amino Acids: Non-polar, polar, basic (positive charge), acidic (negative charge).

• Essential Amino Acids: Must be obtained from diet.

• Nonessential Amino Acids: Can be synthesized by the body.

Levels of Protein Structure

Proteins have four levels of structure, each contributing to their function.

• Primary Structure: Sequence of amino acids.

• Secondary Structure: Hydrogen bonding between backbone atoms, forming α-helices and β-sheets.

• Tertiary Structure: Interactions among R-groups, including hydrophobic, electrostatic, hydrogen bonds, and disulfide bridges.

• Quaternary Structure: Combination of multiple polypeptide subunits.

Protein Structure and Disease

The function of a protein depends on its structure. Changes in structure, such as mutations, can lead to diseases like sickle cell anemia.

• Sickle Cell Anemia: Caused by a point mutation in hemoglobin, resulting in abnormal protein structure and function.

• Denaturation: Loss of protein structure due to heat or chemicals, leading to loss of function.

Protein Functions and Analysis

Proteins perform diverse functions, including transport, defense, structure, catalysis, and movement. X-ray crystallography is used to determine protein structure.

• Transport: Hemoglobin transports oxygen.

• Defense: Antibodies protect against pathogens.

• Structure: Collagen provides support.

• Enzymes: Catalyze biochemical reactions.

• Movement: Actin and myosin enable muscle contraction.

• X-ray Crystallography: Reveals protein and nucleic acid structure by analyzing diffraction patterns.

Nucleic Acids: Structure and Function

Nucleic Acids and Nucleotides

Nucleic acids, including DNA and RNA, store and transmit genetic information. Their monomers, nucleotides, consist of a phosphate group, pentose sugar, and nitrogenous base.

• DNA: Deoxyribonucleic acid, stable, stores genetic information.

• RNA: Ribonucleic acid, less stable, involved in protein synthesis and regulation.

• Nucleotide Structure: Phosphate, pentose sugar (deoxyribose or ribose), nitrogenous base (purine or pyrimidine).

Types of Pentose Sugar

DNA contains deoxyribose, which is more stable, while RNA contains ribose, which is less stable and more reactive.

• Deoxyribose: Lacks an oxygen atom at the 2' carbon.

• Ribose: Has an OH group at the 2' carbon.

Nitrogenous Bases

Nucleotides contain either purine (adenine, guanine) or pyrimidine (cytosine, thymine, uracil) bases.

• Purines: Two rings (adenine, guanine).

• Pyrimidines: One ring (cytosine, thymine, uracil).

DNA Structure

DNA is a double helix with antiparallel strands, held together by hydrogen bonds between complementary bases.

• Antiparallel: Strands run in opposite directions (5' to 3' and 3' to 5').

• Base Pairing: Adenine pairs with thymine, guanine pairs with cytosine.

Genomics and Proteomics

Bioinformatics

Bioinformatics uses computer software to analyze large biological data sets, such as DNA sequences and protein structures. Tools like BLAST help researchers compare genetic information efficiently.

• Genomics: Study of genomes, the complete set of DNA in an organism.

• Proteomics: Study of the entire set of proteins produced by an organism.

• Applications: Disease research, evolutionary studies, biotechnology.