A1 Unity and Diversity : Molecules Flashcards
water and nucleic acids
electronegativity
How strongly the nucleus of an atom attracts the electrons it shares with another atom.
polar molecule
Molecule with positive and negative charge eg. H2O
covelant bond
Bond between non metal atoms where they share electrons eg. H2O
Hydrogen bond
A weak intermolecular force that exists when electronegativity creates a polar covalent bond.
Cohesion
Force that pulls water molecules together that occurs when like molecules are attracted to each other (positive hydrogen to negative oxygen) and causes structures like droplets.
xylem
The tissue in a plant that transports water and mineral ions from roots to the leaves and shoots made of dead cells.
adhesion
The force of attraction between water and other substances making it “stick” to objects - gets things wet.
capillary action
The ability of a liquid to move through narrow tubes that results from adhesion being stronger than cohesion used by plants to move water to move water into cell walls.
hydrophilic
The property of polar substances that attract water molecules.
hydrophobic
The property of non-polar substances that repel water molecules
cell/plasma membrane
The boundary layer of a biological cell, which controls the movement of substances into and out of the cell.
aquaporins
Specialist proteins that facilitate the transport of water across cell membranes. Also known as channel proteins.
Amino acids
Small molecules that make up proteins made of hydrogen, oxygen, carbon and nitrogen.
phloem
Vascular tissue in plants which conducts sugars and other metabolic products downwards from the leaves.
Buoyancy
A force that counteracts the force of gravity caused by high density of liquid water allowing less dense materials to float.
Viscosity
Resistance to flow, related to how much energy is needed to change the shape of a fluid.
Thermal conductivity
The ability of a substance to transfer heat when there is a temperature difference.
Specific heat capacity
How much energy is needed to raise the temperature of a substance.
Goldilocks zone
The orbital distance from a star that will result in liquid water.
polymer
Large molecules, or macromolecules, made by combining smaller compounds called monomers.
nucleic acids
Polymers of nucleotides such as DNA and RNA.
Monomers
A small molecule that can join with other monomers to make a larger polymer molecule.
nucleotides
The building blocks (monomers) of nucleic acids.
condensation reaction
A polymerisation reaction in which two or more molecules combine to form a larger molecule and water is released.
