12BIC - Unit 3: Biological Molecules

Macromolecule

large molecule (also called a polymer)

Polymer

molecule made of repeating identical subunits (monomer) joined together

Polysaccharide monomer

monosaccharide

Polypeptide monomer

amino acids

Polynucleotide/nucleic acid monomer

nucleotides

Lipid monomer

fatty acids and glycerol

Condensation reaction

chemical reaction where monomers are joined by removing a water molecule (makes water); controlled by enzymes

Hydrolysis reaction

chemical reaction where a polymer is split into smaller units by adding water; controlled by enzymes

Carbohydrates

Contain: C, H, O. Formula: Cx(H2O)y. Examples: sugar, starch, cellulose and glycogen

Monosaccharide

one sugar molecule; simplest sugars; soluble, taste sweet, form crystals; Formula: CH₂O; Suffix: -ose

Disaccharide

two sugar molecules; formed when 2 monosaccharides join via condensation (glycosidic bond)

Polysaccharide

more than two sugar molecules; polymer of monosaccharides joined by condensation (e.g., starch, glycogen, cellulose)

Triose

3C monosaccharide

Pentose

5C monosaccharide

Hexose

6C monosaccharide (formula: C₆H₁₂O₆ or (CH₂O)₆)

⍺-glucose (Alpha-glucose)

Hexose sugar where the OH group on 1C is below the plane

𝛽-glucose (Beta-glucose)

Hexose sugar where the OH group on 1C is above the plane

Glucose ring structure

5 carbon atoms and 1 oxygen; Carbons numbered 1 to 6 clockwise; 5C linked to 2 O; side branches end with H/OH, one CH2OH (alcohol)

Glycosidic bond

Bond formed during condensation when 1 OH-group bonds to the H on the next molecule to form water

Starch

Polymer of thousands of 1-4 linked ⍺ glucose molecules forming a long, unbranched chain

Amylose

Starch form that is curved and coils up into helical structures; H-bonds form between some H and O

Amylopectin

Starch form where the chain is branched

Glycogen

Compact polymer of ⍺ glucose monomers; 1,4 links (parent chain) and 1,6 links (branch); Stored in muscle tissue and the liver

Cellulose

Most abundant organic molecule; mechanically strong; made of 𝛽-glucose monomers rotated 180°

Microfibrils

Bundles of 60-70 cellulose molecules cross-linked tightly by H-bonds

Cellulose Fibres

Bundles of microfibrils held together by H bonding; form cell walls with layers running in different directions for strength

Lipids

organic molecules that are insoluble in water; Contain C, H and O

3 important lipid groups

Triglycerides, Phospholipids, Steroids

Functions of Lipids

Energy supply (long term, releases more E than carbs), thermal insulator, buoyancy, mechanical support, electrical insulation in nerve cells, cell membrane

Triglyceride

3 fatty acids react with glycerol via condensation; ester bonds form; COOH group loses acidic properties

Ester bond

Bond between each fatty acid and glycerol in a triglyceride

Glycerol

An alcohol with 3 -COH groups

Phospholipid

Formed when a triglyceride is converted by replacing a fatty acid with a phosphoric acid

Saturated fats

Saturated fatty acids + glycerol

Unsaturated fats

Fatty acids contain double bonds (Monounsaturated = 1, Polyunsaturated = 2/more)

Liquid lipids (room temp)

Triglycerides with short fatty acid chains or unsaturated fatty acids; produced by plants

Proteins

Elements: C, H, O, N and sometimes S; Made of monomers called amino acids

Amino acids (aa)

Central C is bonded to NH₂-group, COOH-group, H and a R-group; differ only in R-group (20 used in synthesis)

Peptides

Form when amino acids are bonded by peptide bonds at the ribosome (2 aa = dipeptide, 2+ = polypeptide)

Primary Structure

chain sequence of aa; type and order of aa determines final protein structure

Secondary Structure

chain coils up (𝝰-helix) or folds (𝛃-pleated sheets); held by H-bonds for stability

Alpha (𝝰) helix

Secondary structure where H-bonds form between O in COOH and H in NH₂

Beta (𝛃) pleated sheets

Secondary structure where H-bonds form between parallel chains

Fibrous protein

Generally insoluble (hydrophobic R-groups outside); twisting adds tensile strength; e.g., collagen and keratin

Collagen

Fibrous protein of 3 𝝰-helix polypeptides wound into a triple helix rope; held by H-bonds/covalent bonds; found in skin, tendons, bone

Glycine in collagen

Almost every 3rd aa is a glycine (smallest aa); allows strand to stay close to form a tight coil

Collagen fibrils

Covalent bonds between R-groups cross-link parallel molecules side by side; ends are staggered to prevent weak spots

Tertiary Structure

secondary structures fold around on itself forming a complex 3D-shape; held by H-bonds, disulphide bridges, ionic bonds, hydrophobic interactions

Disulphide bridges

Covalent bonds (S-S) that form between cysteine molecules to hold protein folds

Ionic bonds in proteins

Form between R-groups (amino + carboxyl groups)

Quaternary Structure

formed when 2 or more polypeptide chains join

Globular Proteins

Molecule curled up into a small ball; usually soluble; hydrophobic R-groups point to center, hydrophilic on outside (e.g., hemoglobin)

Hemoglobin

oxygen carrier pigment found in RBC; 4 polypeptide chains (2 𝛼, 2 𝛽); each folds around a haem-group

Haem group

prosthetic group (not made of aa) containing an Fe-atom; O₂ binds to Fe; responsible for bright red colour when oxygenated

Water's physical state

Normally exists as gas at room temp but H-bonds allow it to remain liquid; energy needed to break H-bonds to change phase

Water as a solvent

Dissolves polar molecules or ions

High heat capacity (Water)

Takes a lot of energy to heat up due to H-bonds

High latent heat of evaporation (Water)

Energy needed to evaporate is high due to H-bonds

Water density

Solid state (ice) is less dense than liquid state because H-bonds hold the molecules further apart

Cohesion (Water)

Water molecules stick together

Adhesion (Water)

Water molecules stick to other substances

Roles of Water

Transport medium, reagent in reactions (photosynthesis/hydrolysis), insulation (ice floats), surface tension (pond skaters)