AS Biology - Molecules, Bonding, Water, Carbohydrates, Lipids, Proteins, and Circulation (Notes)

A comprehensive set of vocabulary-style flashcards covering key concepts from bonding, water properties, organic molecules (carbohydrates, lipids, proteins), and mammalian transport systems (circulation, heart, plasma).

Atom

The basic unit of an element; composed of a nucleus (protons and neutrons) surrounded by electrons in shells.

Compound

Substance formed when atoms of two or more elements react to form chemical bonds.

Nucleus

Center of the atom containing protons and neutrons.

Proton

Positively charged particle in the nucleus.

Neutron

Electrically neutral particle in the nucleus.

Electron

Negatively charged particle that orbits the nucleus in electron shells.

Full outer shell

A stable electron arrangement where the outermost shell is complete, making an atom unlikely to react.

Ion

An atom that has gained or lost electrons, giving it a net electric charge.

Cation

Positively charged ion formed when atoms lose electrons.

Anion

Negatively charged ion formed when atoms gain electrons.

Ionic bond

Bond formed by the complete transfer of valence electrons, producing oppositely charged ions.

Electron donor

Atom or element that gives up electrons in a bond (often a metal in ionic bonding).

Electron acceptor

Atom or element that gains electrons in a bond (often a nonmetal in ionic bonding).

Noble gas configuration

Stable electron arrangement achieved when outer shell is filled (octet rule).

Octet rule

Atoms tend to gain, lose, or share electrons to obtain a full outer shell of eight electrons.

Net charge

Overall electrical charge of a compound; for ionic compounds it must be zero.

Covalent bond

Bond formed when two atoms share one or more pairs of electrons.

Electronegativity

The ability of an atom to attract electrons in a bond.

Polar covalent bond

Covalent bond with unequal sharing of electrons (electronegativity difference typically 0.5–1.7).

Non-polar covalent bond

Covalent bond where electrons are shared equally (electronegativity difference typically 0–0.4).

Dipole

Separation of charge within a molecule due to unequal sharing of electrons.

Polar molecule

Molecule with a dipole moment due to unequal distribution of charge.

Dissociation

Process by which ionic substances separate into ions when dissolved in water.

Hydrogen bond

Weak intermolecular attraction between a slightly positive H atom and a slightly negative atom (often O or N) in another molecule.

Water (H2O)

Polar solvent essential for life, forms hydrogen bonds, dissolves many substances, has high cohesion and surface tension.

Hydrophilic

Substances that are attracted to water and can dissolve in it.

Hydrophobic

Substances that repel water or do not dissolve in it; non-polar substances.

Solvent

The liquid in which solutes dissolve (water is a key biological solvent).

Solute

The substance dissolved in a solvent.

Cohesion

Attraction between water molecules, enabling water transport (e.g., in xylem).

Adhesion

Attraction between water and other surfaces.

Surface tension

The cohesive forces at the surface of a liquid that make it act as if covered with a thin skin.

Inorganic ions

Positively or negatively charged ions formed when ionic substances dissolve in water.

Nitrate (NO3−)

An important plant ion used in DNA, amino acids, and proteins formation.

Phosphate (PO4^3−)

Ion used to make ATP, DNA, and RNA.

Chloride (Cl−)

Ion important for nerve impulses and secretory systems.

Hydrogen carbonate (HCO3−)

Ion that buffers blood pH.

Sodium (Na+)

Cation essential for nerve impulses and secretory processes.

Calcium (Ca^2+)

Cation important for bones, cell walls (plants), and muscle contraction.

Hydrogen ion (H+)

Proton important in cellular respiration and pH balance.

Monosaccharide

Simple sugar, the basic unit of carbohydrates (e.g., glucose, ribose).

Disaccharide

Two monosaccharides joined by a glycosidic bond (e.g., sucrose, lactose, maltose).

Polysaccharide

Long chains of monosaccharides; used for energy storage or structure (e.g., starch, glycogen, cellulose).

Glycosidic bond

Covalent bond linking monosaccharide units in carbohydrates.

Alpha glucose

Glucose isomer that forms a coiled structure in starch; bonds cause branching patterns different from beta forms.

Beta glucose

Glucose isomer that forms straight chains in cellulose due to differing glycosidic linkages.

Amylose

Unbranched chain of alpha-glucose in starch, forming a helical structure.

Amylopectin

Branched polysaccharide in starch (alpha-glucose with some 1→6 bonds).

Cellulose

Structural polysaccharide made of beta-glucose; unbranched and forms microfibrils in plant cell walls.

Glycogen

Branched glucose polymer used for energy storage in animals and liver/muscle cells.

Starch

Energy-storage polysaccharide in plants composed of amylose and amylopectin.

Glycosidic linkage (1-4, 1-6)

Specific carbon atoms involved in sugar-to-sugar bonds in disaccharides/polysaccharides.

Condensation reaction

Chemical reaction that links monomers with release of water; builds polymers.

Hydrolysis

Breakdown of polymers into monomers by adding water.

Lipid

Biological group including fats and oils; insoluble in water; energy storage and membrane components.

Triglyceride

Lipid formed from glycerol and three fatty acids via ester bonds.

Glycerol

Three-carbon alcohol backbone of triglycerides.

Fatty acid

Hydrocarbon chain with a carboxyl group; forms esters with glycerol.

Ester bond

Bond formed between glycerol and fatty acids via condensation (esterification).

Saturated fatty acid

Fatty acid with only single bonds between carbon atoms; usually solid at room temperature.

Unsaturated fatty acid

Fatty acid with one or more C=C double bonds; often liquid at room temperature.

Monounsaturated

Fatty acid with one double bond.

Polyunsaturated

Fatty acid with more than one double bond.

Cis fatty acids

Hydrogen atoms on the same side of a double bond; bend in chain; usually liquid at room temperature.

Trans fatty acids

Hydrogen atoms on opposite sides of a double bond; straighter chains; often solid at room temperature.

Hydrophobic

Tendency to repel or fail to mix with water; non-polar substances.

Phospholipid

Lipid with hydrophilic head and hydrophobic tail; forms cell membranes (not detailed in notes but related).

Protein

Biomolecule made of amino acids; essential for structure, function, and regulation of body tissues and organs.

Amino acid

Building block of proteins; contains amino (-NH2), carboxyl (-COOH), hydrogen, and an R group.

Peptide bond

Covalent bond formed between amino acids during condensation to form a polypeptide.

R group (side chain)

Distinct group attached to the central carbon of an amino acid determining its properties.

Primary structure

Sequence of amino acids in a polypeptide, held by peptide bonds.

Secondary structure

Local folding of the polypeptide (e.g., alpha-helix, beta-pleated sheet) held by hydrogen bonds.

Alpha-helix

Right-handed coiled structure as a common secondary structure in proteins.

Beta-pleated sheet

Secondary structure with strands linked by hydrogen bonds forming a pleated sheet.

Tertiary structure

Three-dimensional folding of a polypeptide held by various bonds between R groups.

Quaternary structure

Arrangement of two or more polypeptide chains in a protein complex.

Fibrous protein

Protein with long, parallel chains; usually insoluble and structural (e.g., collagen).

Globular protein

Globular-shaped proteins with complex tertiary/quaternary structures; functional proteins like enzymes and antibodies.

Collagen

Fibrous protein providing structural strength to connective tissue; abundant in animals.

Haemoglobin

Globular protein with four polypeptide chains and heme iron; transports oxygen.

Conjugated protein

Protein attached to a non-protein component (prosthetic group) that influences function.

Prosthetic group

Non-protein component tightly bound to a protein, affecting its function.

Lipoprotein

Protein conjugated with lipids that aids lipid transport in the blood.

Glycoprotein

Protein with carbohydrate group; water-binding and protective roles in mucus and membranes.

Denaturation

Loss of a protein’s native structure due to changes in temperature or pH, leading to loss of function.

Hydrogen bonds in proteins

Intermolecular bonds that help stabilize secondary and tertiary structures.

Disulfide bonds

Strong covalent bonds between cysteine residues that stabilize protein structure.

Ionic bonds in proteins

Electrostatic bonds between charged side chains within a protein.

Haemoglobin’s structure

Quaternary globular protein with four polypeptide chains around a heme group for oxygen binding.

Haem group

Iron-containing component of haemoglobin essential for oxygen binding.

Primary structure (protein)

Amino acid sequence of a protein, held by peptide bonds.

Globular vs Fibrous proteins

Globular: spherical, soluble, enzymatic/hormonal; Fibrous: elongated, structural, insoluble.

Plasma

Liquid component of blood; carries cells, nutrients, hormones, waste, and maintains temperature.

Red blood cells (RBCs)

Cells that transport oxygen via haemoglobin.

White blood cells (WBCs)

Cells of the immune system defending against pathogens.

Platelets

Cell fragments involved in blood clotting.

Diffusion

Movement of particles from high to low concentration down a concentration gradient.

Surface area to volume ratio (SA:V)

Ratio determining the efficiency of diffusion; decreases as organisms grow larger.

Single circulation

Circulation pattern where blood passes through the heart once per cycle (typical of fish).