Biomolecules

Functional groups

Specific group of atoms within a compound that is responsible for the characteristics of that compound

Carbohydrate structure

Hexagon form, lots of OH

Amino acid structure

Has acid group (COO) + amino (NH3)

Lipid/fatty acid structure

Hydrophobic, lots of CH2

Macromolecules

Polymers made from smaller monomers. Cells use small set of carbon-based molecules to construct macromolecules

Macromolecules act as:

Machines (e.g. speeding up reactions), structural components (e.g. proteins forming cell structure) and information carriers (e.g. DNA + RNA store genetic info)

Conformation

Flexible changes without breaking bonds

Configuration

Requires breaking and reforming bonds

Stereospecificity

Only certain molecules fit. E.g. Enzymes only bind specific substrates

Water role in biomolecule interactions - Hydrogen bonds

Weak short lived attractions between water molecules and other molecules. They are fleeting but constantly reform

Water role in biomolecule interactions - Ionic interactions

Charged molecules interact with water. Electrostatic interactions occur between permanently charged species or between ions and dipoles (like water)

Water role in biomolecule interactions - Hydrophobic interactions

The tendendy of non-polar molecules to group together in water. Non-polar molecules disrupt water’s structure, forcing water molecules into highly ordered, low entropy states. To minimise this, non-polar molecules clump together to reduce contact with water.

Water role in biomolecule interactions - Can der Waals interactions

Weak temporary attractions. Distance dependent interactions that can be attractive or repulsive. Though weak, they help stabilise macromolecules and allow molecules to bind.

Water molecule shape

Distorted tetrahedral shape (due to how electrons are arranged around the oxygen). Oxygen atom is more electronegative —> pulls electrons closer, creating a net dipole moment.

Water - hydrogen bond donor and acceptor

Because of its polarity, water can form hydrogen bonds with other molecules. They are weak but essential in stabilising proteins, DNA and cell structures

Hydrophilic

Water-loving, molecules dissolve easily in water (e.g. salts, sugars, proteins…)

Hydrophobic

Water fearing, molecules do not dissolve in water (e.g. lipids and oils)

Amphipathic

Both loving, molecules have both hydrophobic and hydrophilic parts. (e.g. cell membrane have water-attracting heads and water repelling tails)

Osmosis

Water movement across membranes

Isotonic osmosis

Balanced water flow

Hypertonic osmosis

Water leaves the cell, cell shrinks

Hypotonic osmosis

Water enters the cell, cell swells