B1.1 Carbs and Lipids

What type of bonds does carbon form and why are they important?

Carbon forms covalent bonds by sharing electron pairs, creating strong and stable structures essential for biological molecules.

Why is life described as carbon‑based?

Carbon is present in carbohydrates, lipids, proteins, and nucleic acids, forming the backbone of biological macromolecules

How many covalent bonds can carbon form and what does this allow?

Carbon forms four covalent bonds, allowing diverse structures such as chains, rings, and branched molecules.

What are monomers and polymers?

Monomers are small subunits; polymers are long chains of monomers formed through polymerisation.

What reaction forms macromolecules?

Condensation reactions form macromolecules by creating covalent bonds and releasing water.

What reaction breaks macromolecules?

Hydrolysis reactions break covalent bonds using water to split polymers into monomers.

What is the general formula for monosaccharides?

CnH2nOn

What are the properties of monosaccharides?

They are colourless, crystalline, and soluble in water.

What are triose, pentose, and hexose sugars?

Triose has 3 carbons, pentose has 5, hexose has 6.

What is glucose and why is it important?

Glucose is a hexose sugar (C6H12O6) used as the main respiratory substrate and produced in photosynthesis.

What are alpha and beta glucose?

They are structural isomers differing in the orientation of the hydroxyl group on carbon 1.

Which polysaccharides are formed from alpha glucose?

Starch and glycogen.

Which polysaccharide is formed from beta glucose?

Cellulose

Why is glucose soluble and easily transported?

Its polar structure allows it to dissolve in water and move through biological fluids.

What is the function of starch and glycogen?

They act as compact, insoluble energy storage molecules.

Why must storage polysaccharides be insoluble?

Soluble molecules lower water potential, causing cells to take in water and potentially burst.

What is amylose?

An unbranched alpha‑glucose polymer with 1,4 glycosidic bonds forming a compact helix.

What is amylopectin?

A branched alpha‑glucose polymer with 1,4 and 1,6 glycosidic bonds.

Why is glycogen highly branched?

More branches allow rapid hydrolysis to meet high metabolic demands in animals.

What is cellulose?

A structural polymer of beta‑glucose with alternating inverted monomers forming straight chains.

What gives cellulose its strength?

Hydrogen bonds between parallel chains forming microfibrils.

What are glycoproteins?

Molecules formed when carbohydrates covalently bond to polypeptides.

What roles do glycoproteins play in membranes?

Cell recognition, signalling, endocytosis, adhesion, and stabilisation.

How do glycoproteins determine blood type?

Different glycoprotein antigens (A, B, AB, or none) appear on red blood cells.

Why are lipids insoluble in water?

They contain long non‑polar hydrocarbon chains.

What is a triglyceride?

A lipid formed from glycerol and three fatty acids via esterification.

What is esterification?

A condensation reaction forming ester bonds between glycerol and fatty acids, releasing water.

What is the difference between saturated and unsaturated fatty acids?

Saturated fatty acids have only single bonds; unsaturated fatty acids contain one or more C=C double bonds.

Why are saturated fats solid at room temperature?

Straight chains pack tightly, increasing melting point.

Why are unsaturated fats liquid at room temperature?

Double bonds create kinks, preventing tight packing.

What is a phospholipid?

A lipid with glycerol, two fatty acids, and a phosphate group.

What does amphipathic mean?

Having both hydrophilic and hydrophobic regions.

How do phospholipids form membranes?

They form bilayers with hydrophobic tails inward and hydrophilic heads outward.

Why can steroid hormones cross membranes easily?

They are non‑polar lipids derived from cholesterol.

What is metabolic water?

Water produced when lipids are respired, useful for desert animals