Biological molecules

Amino acid

Amino acid

The building blocks of proteins, consisting of a central carbon atom, an amine group (-NH2), a carboxyl group (-COOH), and a variable side chain (R).

Ammonium

NH4+ ions that can be converted to nitrates by saprobionts during the nitrogen cycle.

Benedict's test for non-reducing sugars

A test that involves hydrolyzing non-reducing sugars and then proceeding with the Benedict's test as usual.

Benedict's test for reducing sugars

A test that involves adding Benedict's reagent to a sample and heating it to observe a color change from blue to orange or brick-red.

Biologically important properties of water

●reaches maximum density at 4℃ ●high surface tension ●incompressible ●metabolite/ solvent for chemical reactions in the body ●high specific heat capacity ●high latent heat of vaporisation ●cohesion between molecules

Biosensors

Devices that detect the presence of a chemical and convert the response into a detectable electrical signal.

Biuret test

A test for proteins that confirms the presence of peptide bonds by changing color from blue to purple.

Bond formed when monosaccharides react

(1,4 or 1,6) glycosidic bond.

Calcium ions

Ca2+ ions used to make calcium pectate for stability in plant cell walls and regulate neurotransmitter exocytosis.

Chloride ions

Cl- ions involved in inhibitory synapses to cause hyperpolarization.

Collagen

A fibrous protein that is a component of bones, cartilage, and connective tissues.

Colorimetry

A method to measure the concentration of a solution by measuring absorbance or % transmission.

Condensation reaction

Chemical bond forms between 2 molecules & a molecule of water is produced.

Disaccharides

Condensation reaction forms glycosidic bond between 2 monosaccharides: ●maltose: glucose + glucose ●sucrose: glucose + fructose ●lactose: glucose + galactose. All have molecular formula C12H22O11.

Elastin

A fibrous protein that provides elasticity to connective tissues, arteries, skin, lungs, and ligaments.

Elements in carbohydrates and lipids

C, H, O

Elements in nucleic acids

C, H, O, N, P

Elements in proteins

C, H, O, N, S

Fibrous proteins

Proteins that form long chains or fibers, are insoluble in water, and provide structural support.

Formation of triglycerides

Condensation reaction between 1 molecule of glycerol & 3 fatty acids which forms ester bonds.

Globular proteins

Proteins that are spherical and compact, usually water-soluble and involved in metabolic processes.

High specific heat capacity and latent heat of vaporisation of water

Acts as a temperature buffer which enables endotherms to resist fluctuations in core temperature to maintain optimum enzyme activity.

High surface tension of water

Slows water loss due to transpiration in plants. Water rises unusually high in narrow tubes, lowering demand on root pressure. Some insects can 'skim' across the surface of water.

Hydrocarbon tail

A long chain of carbon and hydrogen atoms that contributes to the hydrophobic properties of molecules.

Hydrogen bonds

Intermolecular forces of attraction between a lone pair on O 𝛿- of one molecule & H 𝛿+ on an adjacent molecule.

Hydrogen ions

H+ ions that regulate pH and can interact with bonds in tertiary protein structure to cause denaturation.

Hydrogencarbonate ions

HCO3- ions that form when CO2 dissolves in water and are involved in pH regulation.

Hydrolysis reaction

A water molecule is used to break a chemical bond between 2 molecules e.g. peptide bonds in proteins, ester bonds between fatty acids & glycerol in lipids.

Hydroxide ions

OH- ions that affect pH and can interact with bonds in tertiary protein structure to cause denaturation.

Hydroxyl group

A functional group consisting of an oxygen atom bonded to a hydrogen atom (-OH).

Ice floats on water

Ice is less dense than water because H-bonds hold molecules in fixed positions further away from each other. Insulates water in arctic climates so aquatic organisms can survive.

Incompressible nature of water

Provides turgidity to plant cells and hydrostatic skeleton for some small animals e.g. earthworms.

Keratin

A fibrous protein that serves as a structural component of hair, nails, and the outer layer of skin.

Monomer

Smaller units that join together to form larger molecules such as monosaccharides (glucose, fructose, galactose, ribose), amino acids, and nucleotides.

Nitrates

NO3- ions used to make DNA, amino acids, and NADP for photosynthesis.

Phosphate ions

PO4^3- ions that are components of ATP/ADP for energy release.

Phospholipid bilayer

A double layer of phospholipids that forms the cell membrane, providing structure and stability.

Phospholipids and triglycerides as polymers

No; they are not made from a small repeating unit. They are macromolecules.

Polymer

Molecules formed when many monomers join together, such as polysaccharides, proteins, and DNA/RNA.

Polypeptide

A chain of amino acids linked by peptide bonds formed through condensation reactions.

Potassium ions

K+ ions involved in the generation of action potentials in neurons.

Primary structure of a protein

The sequence, number, and type of amino acids in a polypeptide, determined by the sequence of codons on mRNA.

Properties of α-glucose

●Small & water soluble = easily transported in bloodstream. ●Complementary shape to antiport for co-transport for absorption in gut. ●Complementary shape to enzymes for glycolysis = respiratory substrate.

Quaternary structure of a protein

The structure formed when two or more polypeptide chains assemble into a functional protein, held together by bonds similar to those in tertiary structure.

Rf values

Ratios that allow comparison of how far molecules have moved in chromatograms, calculated as the distance between origin and center of pigment spot divided by the distance between origin and solvent front.

Saturated fatty acids

●Contain only single bonds ●Straight-chain molecules have many contact points ●Higher melting point = solid at room temperature ●Found in animal fats.

Secondary structure of a protein

The local folded structures that form within a protein due to hydrogen bonding, including α-helices and β-pleated sheets.

Sodium ions

Na+ ions involved in the maintenance of resting potential of neurons and co-transport mechanisms.

Structure and function of cholesterol

Steroid structure of 4 hydrocarbon rings. Hydrocarbon tail on one side, hydroxyl group (-OH) on the other side. Adds stability to cell surface phospholipid bilayer by connecting molecules & reducing fluidity.

Structure and function of phospholipids

Amphipathic: glycerol backbone attached to 2 hydrophobic fatty acid tails & 1 hydrophilic polar phosphate head. ●Forms phospholipid bilayer in water = component of membranes. ●Tails can splay outwards = waterproofing e.g. for skin.

Structure and functions of cellulose

Polymer of β-glucose gives rigidity to plant cell walls (prevents bursting under turgor pressure, holds stem up). ●1,4 glycosidic bonds. ●Straight-chain, unbranched molecule. ●Alternate glucose molecules are rotated 180°. ●H-bond crosslinks between parallel strands form microfibrils = high tensile strength.

Structure and functions of glycogen

Main storage polymer of α-glucose in animal cells (but also found in plant cells): ●1,4 & 1,6 glycosidic bonds. ●Branched = many terminal ends for hydrolysis. ●Insoluble = no osmotic effect & does not diffuse out of cells. ●Compact.

Structure and functions of starch

Storage polymer of α-glucose in plant cells: ●insoluble = no osmotic effect on cells ●large = does not diffuse out of cells. Made from amylose and amylopectin: ●1,4 & 1,6 glycosidic bonds ●branched = many terminal ends for hydrolysis into glucose ●1,4 glycosidic bonds ●helix with intermolecular H-bonds = compact.

Structure of haemoglobin

A globular conjugated protein with 2 α-chains, 2 β-chains, and 4 prosthetic haem groups, facilitating oxygen transport.

Structure of ribose

Pentose monosaccharide (5C) with ring structure.

Structure of triglycerides

●High energy:mass ratio = high calorific value from oxidation (energy storage). ●Insoluble hydrocarbon chain = no effect on water potential of cells & used for waterproofing. ●Slow conductor of heat = thermal insulation e.g. adipose tissue. ●Less dense than water = buoyancy of aquatic animals.

Structure of α-glucose

Cis isomer, both hexose monosaccharides (6C) with ring structure.

Structure of β-glucose

Trans isomer.

Tertiary structure of a protein

The three-dimensional structure formed by further folding of a protein, stabilized by various bonds including disulfide bridges and hydrogen bonds.

Test for lipids

A method involving dissolving solid samples in ethanol and adding water to form a milky white emulsion.

Test for starch

A test that involves adding iodine solution, resulting in a color change from orange to blue-black if starch is present.

Unsaturated fatty acids

●Contain C=C double bonds ●'Kinked' molecules have fewer contact points ●Lower melting point = liquid at room temperature ●Found in plant oils.

Water as a solvent

Polar universal solvent dissolves & transports charged particles involved in intra & extracellular reactions e.g. PO4 3- for DNA synthesis.

α-helix

A type of secondary structure in proteins characterized by a spiral shape with all N-H bonds on the same side.

β-pleated sheet

A type of secondary structure in proteins where N-H and C=O groups alternate from one side to the other.