W1 CELLULAR LEVEL ORGANISATION

Matter

Anything with mass and volume, made of atoms.

Atoms

Basic units of matter that join to form chemicals.

Proton

Positively charged subatomic particle with 1 mass unit.

Neutron

Neutral subatomic particle with 1 mass unit.

Electron

Negatively charged subatomic particle with very small mass.

Nucleus

The central part of an atom, containing protons and neutrons.

Electron Cloud

Area around the nucleus, containing electrons.

Atomic Number

The number of protons, defines the element.

Electron Shells

Layers of electrons surrounding the nucleus.

Valence Shell

Outermost electron shell that determines bonding.

Atomic Weight

Average mass based on isotopes of an element.

Isotopes

Atoms of the same element with different neutron numbers; some can be radioactive.

Reactivity

The degree to which an atom readily forms chemical bonds with other atoms.

Molecule

Two or more atoms joined by strong bonds.

Compound

Atoms of different elements joined by bonds.

Molecular Weight

Sum of atomic weights in a molecule/compound.

Ionic Bonds

Formed by the transfer of electrons from a donor (cation) to an acceptor (anion).

Covalent Bonds

Atoms share electrons to form this type of bond.

Hydrogen Bonds

Weak bonds between slightly positive and slightly negative regions of molecules.

Nonpolar Covalent Bond

Equal sharing of electrons.

Polar Covalent Bond

Unequal sharing of electrons creating polar molecules.

Solid

Constant volume and shape.

Liquid

Constant volume, shape changes.

Gas

Changes volume and shape.

Reactants

Materials entering a chemical reaction.

Products

Materials produced by a chemical reaction.

Metabolism

All chemical reactions in the body.

Energy

Capacity for work (kinetic = motion, potential = stored).

Chemical Energy

Potential energy in chemical bonds.

Decomposition (Catabolism)

Breaks bonds, e.g. AB → A + B.

Hydrolysis

AB + H₂O → AH + BOH. A decomposition reaction.

Synthesis (Anabolism)

Forms bonds, e.g. A + B → AB.

Dehydration Synthesis

AH + BOH → AB + H₂O. A synthesis reaction.

Exchange Reaction

Involves both decomposition and synthesis, e.g. AB + CD → AD + CB.

Reversible Reactions

Can proceed in either direction (A + B ↔ AB), seek equilibrium.

Enzymes

Protein catalysts that lower activation energy needed for reactions.

Saturation Limits

Max speed determined by substrate availability.

Cofactor/Coenzyme

Ions/molecules needed for enzyme function. Non-protein organic cofactors.

Specificity

Only catalyze specific reactions.

Regulation

Controlled by other chemicals.

Denaturation

Loss of enzyme shape/function due to heat or pH changes.

Inorganic Compounds

Usually lack carbon; include water, acids, bases, salts.

Organic Compounds

Always contain carbon and hydrogen; include carbohydrates, lipids, proteins, nucleic acids.

Solvent

Liquid portion of a solution.

Solutes

Dissolved substances in a solution.

Universal Solvent

Many substances dissolve in water.

Dissociation/Ionization

Ionic compounds separate in water, producing ions.

Hydration Spheres

Water surrounds ions, keeping them in solution.

Electrolytes

Inorganic ions that conduct electricity in solution.

Hydrophilic

Water-loving; dissolve easily in water.

Hydrophobic

Water-fearing; do not dissolve easily in water.

Colloid

Solution with large molecules, e.g. plasma.

Suspension

Large particles settle out, e.g. whole blood.

pH

Measure of hydrogen ion (H⁺) concentration.

Acids

Proton donors, increase H⁺ in solution.

Bases

Proton acceptors, remove H⁺ from solution.

Buffers

Stabilize pH.

Monomer

Single subunit.

Polymer

Chain of monomers.

Monosaccharides

Simple sugars (glucose, fructose, galactose).

Disaccharides

Two monosaccharides (sucrose, maltose).

Polysaccharides

Many sugars (glycogen, starch, cellulose).

Isomers

Same formula, different structure.

Fatty Acids

Long hydrocarbon chains that may be saturated or unsaturated.

Monounsaturated

One double bond.

Polyunsaturated

Two or more double bonds.

Eicosanoids

Cannot be made by the body; derived from diet (arachidonic acid).

Leukotrienes

Immune system mediators derived from arachidonic acid.

Prostaglandins

Local hormones derived from arachidonic acid.

Glycerides

Fatty acids + glycerol (mono-, di-, triglycerides); energy, insulation, protection.

Steroids

Four-ring structure (e.g. cholesterol, sex hormones, corticosteroids, bile salts).

Phospholipids/Glycolipids

Diglyceride + phosphate/sugar; key for cell membranes.

Amino acids

Monomers of proteins, linked together by peptide bonds.

Peptide bond

Link between amino acids forming polypeptides.

Enzymes

Catalysts that lower activation energy and are unchanged after reaction

Active Site

Binds the substrate to the enzyme.

Glycoproteins

Protein + carbohydrate (enzymes, hormones, antibodies, plasma membranes).

Proteoglycans

Protein + polysaccharide (increase viscosity).

RNA

Involved in protein synthesis.

DNA

Stores genetic information, directs protein synthesis.

Phosphorylation

Addition of phosphate group; stores energy.

ATP (Adenosine Triphosphate)

Three phosphates, main energy currency.

ADP (Adenosine Diphosphate)

Two phosphates.

AMP (Adenosine Monophosphate)

One phosphate.

ATPase

Enzyme converting ATP to ADP, releasing energy.