Edexcel IAS Biology Unit 1 Notes – Water, Carbohydrates, Lipids, Proteins (VOCABULARY)

Vocabulary flashcards covering water properties, carbohydrates, lipids, and proteins as described in the lecture notes.

Water

A covalent compound of hydrogen and oxygen that is dipolar and forms hydrogen bonds; acts as a universal solvent with high melting/boiling points due to hydrogen bonding.

Dipole

A molecule with partial positive and partial negative charges at opposite ends, as seen in water.

Hydrogen bond

A weak bond formed when a hydrogen atom covalently bonded to an electronegative atom (like O) is attracted to another electronegative atom; responsible for many water properties.

Polar molecule

Molecule with unequal distribution of charge, having a positive and a negative end; water is polar.

Solvent

A substance that dissolves solutes; water is an unusual/excellent solvent for polar or ionic substances.

Hydrophilic

Water-loving; substances that dissolve in water.

Hydrophobic

Water-repelling; substances that do not dissolve in water.

Cohesion

Water molecules sticking to each other via hydrogen bonds.

Adhesion

Water molecules sticking to non-water surfaces via hydrogen bonds.

Surface tension

Tension at the surface of a liquid caused by cohesive forces; water has high surface tension from hydrogen bonding.

Latent heat of vaporization

Heat required to convert 1 kg of water from liquid to vapor at a constant temperature; high value enables evaporative cooling.

Specific heat capacity

Energy required to raise the temperature of 1 kg of water by 1°C; high value stabilizes temperatures.

Density (ice vs water)

Water is most dense at 4°C; ice is less dense than liquid water and floats, insulating bodies of water.

Evaporative cooling

Cooling achieved when water absorbs heat to vaporize; helps regulate body and environmental temperatures.

Transpiration

Loss of water vapor from plant surfaces, driven by cohesion and adhesion in the xylem.

Capillary action

Movement of water up narrow tubes due to cohesion and adhesion; enables plant transport.

Hydration shell

Water molecules surrounding dissolved ions; stabilizes ions in solution.

Monosaccharide

A single sugar unit (e.g., glucose, fructose, galactose); building blocks of carbohydrates.

Disaccharide

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

Polysaccharide

Polymers of many monosaccharides (e.g., starch, glycogen, cellulose) for energy storage or structure.

Glycosidic bond

Bond between monosaccharides formed by condensation; can be cleaved by hydrolysis.

Condensation reaction

Reaction that forms a glycosidic bond with release of water.

Hydrolysis

Reaction that splits a glycosidic bond by adding water.

Alpha glucose

Glucose isomer with OH on C1 below the ring; component of starch.

Beta glucose

Glucose with OH on C1 above the ring; component of cellulose.

Glucose

Primary monosaccharide used in cellular respiration for energy.

Fructose

Monosaccharide, sweeter than glucose, found in fruits.

Galactose

Monosaccharide; component of lactose found in milk.

Maltose

Disaccharide of glucose + glucose; formed by condensation; 1,4-glycosidic bond.

Sucrose

Disaccharide of glucose + fructose; formed by condensation; 1,2-glycosidic bond; common table sugar.

Lactose

Disaccharide of glucose + galactose; milk sugar; hydrolyzed by lactase.

Starch

Plant storage polysaccharide consisting of amylose and amylopectin (glucose polymers).

Amylose

Linear, unbranched component of starch; 1,4-glycosidic bonds; forms a helix.

Amylopectin

Branched component of starch; 1,4 and 1,6 glycosidic bonds; branched structure.

Glycogen

Animal storage polysaccharide; highly branched; 1,4 and 1,6 glycosidic bonds; energy reserve.

Cellulose

Structural polysaccharide; polymer of β-glucose; forms cellulose microfibrils in plant cell walls; not digestible by humans.

Ribose

Pentose sugar found in RNA.

Deoxyribose

Pentose sugar found in DNA; lacks one oxygen compared to ribose.

1,4-glycosidic bond

Bond linking glucose units in starch/amylose along the chain.

1,6-glycosidic bond

Bond that creates branches in amylopectin and glycogen.

Reducing sugar

A sugar capable of acting as a reducing agent; mono- and some disaccharides show reducing properties.

Lipids

Organic compounds with carbon, hydrogen, and less oxygen than carbohydrates; hydrophobic and soluble in organic solvents; energy-dense.

Triglyceride

Lipid formed by glycerol plus three fatty acids via ester bonds; main storage form of fat.

Ester bond

Bond between fatty acids and glycerol in triglycerides; formed during condensation (water released).

Saturated fatty acid

Fatty acid with no C=C bonds; straight chain; packs tightly; high melting point.

Unsaturated fatty acid

Fatty acid with one or more C=C bonds; kinked chain; lower melting point; liquids at room temperature.

Monounsaturated

One C=C bond in the fatty acid chain.

Polyunsaturated

More than one C=C bond in the fatty acid chain.

Cis double bond

Double bond causing a bend in the fatty acid tail, preventing tight packing.

Phospholipid

Lipid with glycerol, two fatty acids, and a phosphate head; hydrophilic head and hydrophobic tails; major membrane component.

Glycolipid

Lipid with carbohydrate attached; involved in cell membrane structure and recognition.

Cholesterol

Steroid lipid; component of membranes and precursor for steroids.

Waxes

Esters of fatty acids and alcohols; provide waterproofing and protection.

Glycoprotein

Conjugated protein with carbohydrate attached; part of membranes and signaling.

Lipoprotein

Combination of lipid and protein for transport of lipids in blood.

Haemoglobin

Globular protein with four polypeptide subunits and a heme prosthetic group containing iron for oxygen transport.

Albumin

Globular, soluble protein; highly soluble due to exposed hydrophilic R groups.

Prosthetic group

Non-protein component tightly bound to a protein (e.g., heme in haemoglobin).

Denaturation

Loss of protein structure and function due to heat, acids, salts, or mechanical disruption; primary structure may remain intact.

Collagen

Fibrous protein with three polypeptide chains in a triple helix; high tensile strength; structural protein in connective tissue.

Globular protein

Water-soluble, compact proteins with hydrophilic exterior surfaces; functional roles in transport and catalysis.

Peptide bond

Bond between amino group of one amino acid and carboxyl group of another; forms by condensation.

Amino acid

Building block of proteins; contains amino group, carboxyl group, hydrogen, and a variable R group.

Primary structure

Linear sequence of amino acids in a polypeptide.

Secondary structure

Folding patterns like α-helix and β-pleated sheet held by hydrogen bonds.

Tertiary structure

Three-dimensional folding of a polypeptide stabilized by various bonds and interactions.

Quaternary structure

Assembly of two or more polypeptide chains into a functional protein.

Disulfide bond

Covalent bond between cysteine residues that helps stabilize tertiary/quaternary structure.

Haem

Iron-containing prosthetic group in haemoglobin that binds to oxygen.

Albumin vs Collagen (summary)

Albumin is soluble globular protein; collagen is fibrous with high tensile strength and a triple-helix structure.