Biological Molecules overview

Monomers = small chemical sub-units

Polymers = chemically linked chain of monomers

Condensation = chemical reaction which binds monomers together, eliminating water

Hydrolysis = chemical reaction which breaks bonds, adding water

Examples:

Monomer                        Polymer

Monosaccharides -        polysaccharides

Amino acids -                 polypeptides & proteins

Nucleotides -                  nucleic acids

Monosaccharide = carbohydrate monomers (simple sugars) - glucose, fructose, galactose

Alpha & beta = same chemical properties - different monosaccharide combination

Function = release of energy by respiration

Disaccharide = double sugar - glycosidic bond - maltose, sucrose, lactose

Polysaccharide = long chain of mono/disaccharides - glycogen, starch, cellulose

Glycogen & starch = energy storage, insoluble = no osmotic effect - iodine test (starch-plants)

Cellulose = plants - structural, cell wall strength

Glycoproteins & glycolipids = short sections of carbs/lipids in extra cellular spaces - cell communication/recognition - glycoproteins can serve as cell surface antigens

Functions = energy storage, waterproof, protection, thermal insulation

Triglycerides = glycerol backbone & 3 fatty acid tails - ester bonds

R group = may be saturated (single bonds) or unsaturated (at least 1 double bond)

Phospholipids = glycerol backbone & 2 fatty acids & 1 phosphate group - can ionise and interact with water - fatty acids have hydrophilic heads and hydrophobic tails

Emulsion test = test for presence of lipids:

• 1 test tube containing water, 1 containing food sample
• ethanol added to sample tube - shake to encourage lipid to dissolve
• clear ethanolic layer created (unless filtered/diluted)
• contents of this tube - poured into tube of water
• white emulsion = presense of fats/oils
• small droplets visable - may take time to separate out

Amino acids = monomers which form proteins - specific R groups cause them to differ

Dipeptide = bond formed between 2 amino acids in condensation reaction

Polypeptide = bond formed when condensation occurs many times

Structure of proteins:

• Primary = sequence of amino acid monomers, maintained by peptide bonds
• Secondary = coiling & folding of polypeptide chain, maintained by hydrogen bonds
• Tertiary = further folding - 3D shape, maintained by various covalent bonds
• Quaternary = 2 or more polypeptide chains maintained by hydrogen & non-covalent bonds

Structural = make up parts of body, keep tissue rigid - keratin in hair, skin, nails, etc

Functional = perform active role in body processes - antibodies such as immunoglobins, recognise foreign cells

Denaturation = disrupted structure - heat, pH, concentration, etc

Biological catalyst = speeds up/initiates reactions - doesn't get used up

Substrate = reactants in enzyme-controlled reactions

Enzyme-substrate complex = lowers activation energy - temporary, chemically binded - products released

Active site = lock&key - specific shape....induced fit - similar shape that adjusts

Factors affecting rate = enzyme conc, substrate conc, temp, pH, inhibitor conc.

Competitive inhibitors = similar structure to substrate, competing to bind with active site

Non-competitive = different structure to substrate - binds to enzyme at allosteric site

Structure = consists of adenine, ribose and 3 phosphate groups - doesn't conense into polymer

Hydrolysis = broken into ADP, using the enzyme ATP hydrolase

Functions = energy-requiring reactions, active transport, anabolic reactions

• known as the cell's energy currency
• universally used to assist any reaction which needs energy
• once cell takes in and uses fuel & oxygen, it uses it to produce ATP
• does not leave the cell

Structure = double helix, each is polynucleotide - outside edges=alternating deoxyribose and phosphate groups - held together by phosphodiester bonds

Nitrogenous bases = adenine + thymine, cytosine + guanine - weak hydrogen bonds

• Semi-conservative replication:
• 2 sides peeled apart - forming replication fork
• 2 alternating sugar-phosphate backbone sections remain attached
• bases stay attached to deoxyribose, but are exposed - not attached in base pair
• DNA helicase moves along DNA strands - breaks H bonds, separating strands
• DNA polymerase - different copies act independently on different strands
• nucleotides bind with complementary bases (A+T, C+G)
• phosphodiester bonds form between deoxyribose of new nucleotide and previous nucleotide (which is on the end of developing strand)
• continues until full single DNA strand is added to each template strand
• finally results in 2 double helixes (originally there was only 1)

In DNA replication, one strand runs in 3' to 5' direction - one runs in 5' to 3' direction (known as antiparallel)

• Metabolite:
• Water is involved in biochemical reactions in cells - metabolism
• Condensation (removal of water), hydrolysis (addition of water)
• Essential for light-dependent reactants of photosynthesis

• Solvent:
• Many biological & inorganic substances dissolve in water
• Hydrophilic - "water-liking", will react with/dissolve in water
• Hydrophobic - "water-hating", will not react with/dissolve in water

• high heat capacity (amount of heat needed to raise temperature by 1 degree)
• makes water useful for storing heat energy - stabilises temperature within bodies of animals
• latent heat of vapourisation - efficient cooling by means of sweating
• cohesive properties - allows water to be drawn up in vascular tissues of plants
• low density of ice - lower density than liquid form, so it floats - forms insulating layer at top of ponds/lakes

• known as mineral salts or electrolytes
• always paired with other ions
• Examples:
• Hydrogen ions: H+, aka protons - key to pH - affects metabolism & enzyme activity

• Sodium ions: Na+, involved in uptake of glucose & animo acids ileum by co-transport

• Iron ions:
• 2 types -
• ferrous ions - (Fe2+)
• ferric ions - (Fe3+)
• forms various important biological chemicals
• present in haemoglobin in red blood cells - centre of haem group where it attracts oxygen
• 4 polypeptide chains & 4 haem groups - so 4 iron atom per haemoglobin molecule