Inorganic Ions

Your body needs inorganic ions to stay alive, even though they don't contain much carbon. Think of them as essential minerals that keep your cells running smoothly.

There are two main types: micronutrients (needed in tiny amounts like copper and zinc) and macronutrients (needed in larger amounts). Magnesium is vital for photosynthesis in plants as part of chlorophyll, whilst iron helps your red blood cells carry oxygen around your body.

Nitrate provides the nitrogen needed to make DNA, RNA and amino acids - basically the building blocks of life. Phosphate is equally important, forming part of your DNA and the membranes around every cell. Calcium keeps your bones and teeth strong and helps build plant cell walls.

Quick Tip: Remember "MINPC" - Magnesium, Iron, Nitrate, Phosphate, Calcium - the five essential macronutrients you need to know!

Water

Water isn't just for drinking - it's a polar molecule that makes life possible. The oxygen atom pulls electrons closer, creating a slightly negative end and a slightly positive hydrogen end.

This polarity lets water molecules stick together through hydrogen bonds, forming a lattice-like structure. These weak individual bonds become incredibly strong when there are millions of them working together.

Water acts as the perfect solvent for charged particles and polar molecules $though non-polar substances won't dissolve$. It's also an excellent transport medium - your blood is mostly water carrying nutrients around your body, and plants use water to transport minerals through their xylem.

The high specific heat capacity keeps temperatures stable in aquatic environments, whilst cohesion between molecules creates surface tension and allows water to travel up plant stems. When ice forms, it's less dense than liquid water, so it floats and insulates the water below.

Remember: Water's polar nature gives it all its amazing properties - from dissolving substances to helping plants transport nutrients!

Carbohydrates - The Basics

Carbohydrates are your body's favourite fuel source, ranging from simple sugars to complex starches. Monosaccharides (like glucose) are the simplest form - they're sweet, soluble, and ready to use for energy.

When two monosaccharides join together through a condensation reaction, they form disaccharides like maltose $glucose + glucose$ or sucrose $glucose + fructose$. This process removes water and creates glycosidic bonds. The opposite reaction, hydrolysis, breaks these bonds by adding water back.

Glucose comes in two forms: alpha glucose (OH group points down on carbon 1) and beta glucose (OH group points up). This tiny difference completely changes how they behave in larger molecules.

Plants and animals convert glucose into polysaccharides for storage because they're insoluble (won't affect osmosis), compact (fit in small spaces), and packed with energy in their chemical bonds.

Key Concept: The position of one OH group in glucose (up or down) determines whether you get starch or cellulose - completely different functions!

Carbohydrate Structures

Starch is plants' energy storage system, made of two components. Amylose (20% of starch) forms a compact spiral from alpha glucose with 1-4 linkages. Amylopectin (80% of starch) has both 1-4 and 1-6 linkages, creating branches that can be broken down quickly when energy is needed.

Glycogen works like amylopectin but with even more branches, making it perfect for animals who need rapid energy release. The shorter chains between branches mean more ends for enzymes to attack simultaneously.

Cellulose uses beta glucose with 1-4 linkages, but here's the clever bit - every other molecule rotates 180°, allowing hydrogen bonds to form between parallel chains. This creates incredibly strong microfibrils that give plant cell walls their structural strength.

Chitin follows a similar pattern to cellulose but uses modified glucose molecules with added acetyl groups. This creates the strong, waterproof, lightweight material found in insect exoskeletons and crab shells.

Memory Trick: Alpha glucose makes energy storage molecules (starch, glycogen), beta glucose makes structural molecules (cellulose, chitin)!

Lipids

Lipids are the body's long-term energy storage experts, containing only carbon, hydrogen and oxygen but arranged very differently from carbohydrates. Triglycerides consist of glycerol bonded to three fatty acid tails through ester bonds formed by condensation reactions.

Fatty acids can be saturated (no double bonds, solid at room temperature) or unsaturated (double bonds present, liquid at room temperature). This affects how tightly the molecules can pack together and determines whether you get fats or oils.

Phospholipids are the stars of cell membranes, with a hydrophilic $water-loving$ phosphate head and hydrophobic $water-hating$ fatty acid tails. They automatically arrange into bilayers with heads facing outward and tails tucked inside.

Lipids serve brilliant functions: energy storage (more energy per gram than carbohydrates), insulation, protection around organs, waterproofing, and forming the myelin sheath around nerve cells for faster signal transmission.

Essential Point: Phospholipids' dual nature (loving and hating water) makes them perfect for controlling what enters and exits cells!

Proteins

Proteins are incredibly diverse molecules built from just 20 different amino acids. Each amino acid has an amine group (alkaline), a carboxyl group (acidic), and a unique R group that gives it special properties.

Amino acids join through condensation reactions that create peptide bonds, removing water in the process. Your body can make some amino acids $non-essential$ but others must come from your diet (essential amino acids).

Proteins have four levels of structure. Primary structure is simply the sequence of amino acids. Secondary structure involves hydrogen bonding creating alpha helices or beta pleated sheets. Tertiary structure forms when R groups interact through disulfide bridges, hydrogen bonds and ionic interactions, creating complex 3D shapes.

Quaternary structure occurs when multiple polypeptide chains combine, like the four chains in haemoglobin. The final shape determines the protein's function - enzymes, antibodies, structural proteins and transport molecules all depend on having exactly the right 3D structure.

Critical Insight: Change just one amino acid in the sequence and you can completely alter a protein's function - that's how powerful the primary structure is!