Biological molecules

• Cellulose is a beta glucose polysaccharide, forming long unbranched chains of beta glucose with straight bonds between the glucose molecules
• Cellulose forms microfibrils held together by hydrogen bonds, providing structural support for cell walls due to its strong properties
• Properties of cellulose: Strong, insoluble, hard to break down in fibrous form
• Starch is composed of amylose and amylopectin, both made up of alpha glucose, which is stored as glycogen in animals
• Amylose has a tight, unbranched helix structure, while amylopectin has a long, tight helix structure with branches, making them compact and ideal for storage
• Glycogen, suitable for storage, is compacted like amylopectin, coiled, and has many branches allowing for quick energy release
• Glycosidic bond is the bond between two monosaccharides, like in maltose which consists of 2 alpha glucose monomers
• All monosaccharides are reducing sugars, while most disaccharides are non-reducing sugars
• Examples of hexose monosaccharides: Glucose, fructose, and galactose; examples of pentose monosaccharides: Ribose and deoxyribose
• Ice is less dense than water because the hydrogen bonds between ice are further apart than in liquid water, allowing ice to float and form an insulating layer on top of ponds, maintaining a constant temperature for organisms
• Water is a good solvent due to its polarity, attracting other charged molecules to it
• Water is cohesive and adhesive because of its ability to form hydrogen bonds, useful for acting as a transport medium and moving upwards through narrow capillary tubing
• Amylose forms 1,4 glycosidic bonds
• Amylopectin forms 1,6 glycosidic bonds
• Lipids are a large group of compounds that includes triglycerides, phospholipids, and steroids
• Lipids are insoluble in water, stored as droplets inside the cell, and have various functions in the body:

  • Thermal insulation
  • Energy storage
  • Protection of organs from mechanical damage
  • Control of the entry and exit of molecules into cells
  • Component of steroid hormones like testosterone
  • Buoyancy
  • Waterproofing parts of the body
  • Source of water via respiration
  • Electrical insulation around neurones
  • Aid in the absorption, storage, and production of fat-soluble vitamins A, D, E, and K
• Triglycerides are macromolecules containing one glycerol molecule and three fatty acid chains
• Triglycerides are rich in energy and used to store excess energy, can be broken down in aerobic respiration to release energy, and provide protection to major organs from physical shock
• Saturated fatty acids have each carbon bonded to two hydrogen atoms, found in animal fats, have a higher melting point, and can increase low-density lipoproteins (LDLs, 'bad' cholesterol)
• Unsaturated fatty acids have fewer hydrogen atoms, can have double or triple bonds between carbon atoms, found in plant fats and oils, have lower melting points, and are more likely to be liquid at room temperature
• Phospholipids are similar to triglycerides but have one fatty acid chain replaced by a phosphate group
• Phospholipids form bilayers with hydrophobic 'tails' in the center and hydrophilic 'heads' pointing outwards, making up all cell membranes
• Glycogen has more branches compared to amylopectin
• Cellulose forms 1,4 glycosidic bonds
• Chitin forms 1,4 glycosidic bonds
• Amylopectin is branched polymer of glucose that makes up about 80% of starch
• Amylose is an unbranched polymer of glucose that makes up about 20% of starch
• Lactose is a disaccharide formed by galactose and glucose
• Sucrose is a disaccharide made up of one fructose and one glucose unit
• Maltose is a disaccharide made up of two alpha-glucose units joined together with a beta linkage
• Galactose is a monosaccharide found in lactose
• Fructose is a monosaccharide found in sucrose
• Cellulose is the main component of plant cell walls