2.1.2 Biological Molecules Flashcards
Water structure
H20 - Two delta positive hydrogen atoms and one delta negative oxygen atom joined by covalent bonds. Makes hydrogen bonds with other molecules of water.
Cohesion and Adhesion
Because water is slightly negative its polar (charged).
Cohesive - the attraction of molecules of the same type, water molecules form hydrogen bonds to each other, helps water to be transported up stems in the transpiration stream.
Adhesive - the attraction of molecules of one type to another, allows it to flow up the transpiration stream.
Solvent
Because water is slightly negative its polar (charged). This means that the positive end and the negative end will be attracted to different ions which will dissolve the ions. Therefore water can be used as a solvent to transport ions in the blood. Most biological reactions take place in solution.
Less dense when solid
At low temperatures water freezes, the extra H bonds when frozen increase the space between molecules. Therefore it floats as ice. This enables a habitat for animals that live on ice and insulation for fish.
High Specific Heat Capacity
The energy needed to raise the temperature of 1 gram by 1°C. H bonds absorb a lot of energy. Doesn’t undergo rapid temperature changes and so it’s a good habitat.
High Latent Heat of Evaporation
Lots of energy to break H bonds. Good for cooling, sweating cools the skin.
Carbohydrates
Made up of CHO.
Ribose
Pentose monosaccharide. C5H10O5
Alpha and Beta Glucose
Hexose monosaccharide. C6H12O6. In alpha glucose the carboxyl group points below the plane of the ring, In beta glucose the carboxyl group points above the plane of the ring.
Glucose
Soluble due to polar hydroxyl groups so can be transported. The chemical bonds contain lots of energy.
Monosaccharides to Disaccharides
Joined by condensation reactions and glycosidic bonds (removing H2O), broken by hydroxyl bonds (adding H2O).
Disaccharides
a Glucose + a Glucose = Maltose
a Glucose + Fructose = Sucrose
a/b Glucose + Galactose = Lactose
Starch
Plant store of glucose. Insoluble in water so it doesn’t cause water to enter and stays compact.
Starch Structure - Amylose
Long unbranched chain of a glucose, 1.4. Coiled and compact.
Starch Structure - Amylopectin
Long branches chain of a glucose,1.4 and 1.6. Side branches allow it to be quickly broken down for quick releases of glucose.
Glycogen
Animal store of glucose. Compact.
Glycogen Structure
Very branched, a glucose 1.4 and 1.6.
Cellulose
Plant cell wall material. Strong.
Cellulose Structure
Unbranched, b glucose 1.4. Straight cellulose chains bond by hydrogen bonds to from strong microfibrils.
Triglycerides
Store energy in plants and animals. Lots of chemical energy stored in hydrocarbon chains which is released when broken down. Insoluble so no water enters by osmosis.
Triglycerides Structure
1 glycerol, 3 fatty acid/hydrocarbon (CH) molecules. Hydrophilic tails so insoluble in water. Ester bonds join, condensation and hydrolysis.
Saturated vs Unsaturated
Saturated contain single bonds. CₙH(2 ₙ+1)COOH
Unsaturated contain double bonds.
Phospholipids
Plasma membrane. Hydrophilic head, hydrophobic tail.
Phospholipid Structure
1 phosphate, 1 glycerol, 2 fatty acid molecules.
Cholesterol
Small size, flat shape to fit between membranes. At high temperatures makes phospholipids closer, at low temperatures prevents to closeness. Controls and regulates membrane fluidity.
Amino Acids
Amine group (H2N), carboxyl group (COOH) and an R group. CHON(S).
Peptide bonds, condensation and hydrolysis.
Primary Structure
Sequence of amino acids in the polypeptide chain, a change in the sequence may affect the protein made.
Secondary Structure
Initial folding. H bonds between positive-negative R group atoms cause alpha helix or beta pleated sheet.
Tertiary Structure
Further folding.
Ionic bonds between R groups.
Disulphide bonds when there’s 2
cysteine.
Hydrophilic and hydrophobic interactions.
H bonds between positive-negative R groups atoms.
Quaternary Structure
More than one polypeptide chain.
All same bonds as tertiary.
Globular Proteins
R groups are on the outside therefore hydrophilic and soluble.
Haemoglobin
Globular protein. Carries oxygen around the body. 4 polypeptide chains held together by hydrophobic and H bonds. Conjugated protein- has a prosthetic group (non protein - haem which contains iron to bind to oxygen).
Insulin
Globular protein. Hormone secreted by pancreas to regulate blood glucose levels. Solubility means it can be transported to the tissue where it’s needed. 2 polypeptide chains held together by disulphide bonds.
Amylase
Globular protein. Enzyme that breaks down starch. Single polypeptide chain, alpha helix and beta pleated sheets.
Fibrous Proteins
Insoluble and strong.
Collagen
Fibrous protein. In connective tissue, strong and minerals can bind to make stronger.
Keratin
Fibrous protein. Hair, skin, nails, feathers, horns etc. Flexible or tough.
Elastin
Fibrous protein. Stretch and recoil in skin, blood vessels, ligaments etc.
Ions
Cation - positive charge.
Anion - negative charge.
Inorganic - usually no C.
Ca2+
Calcium. Transmitting of nerve impulses, release of insulin, cofactor, bone formation.
Na+
Sodium. Generating nerve impulses, muscle contraction, regulating fluid balance.
K+
Potassium. Generating nerve impulses, muscle contraction, regulating fluid, activates essential enzymes for photosynthesis.
NH4+
Ammonium. Absorbed from the soil by plants, source of nitrogen.
NO3-
Nitrate. Absorbed from the soil by plants, source of nitrogen.
HCO3-
Hydrocarbonate. Buffer to maintain blood pH.
Cl-
Chloride. Chloride shift to maintain blood pH, amylase cofactor, nerve impulses.
PO43-
Phosphate Photosynthesis and respiration reactions, synthetics of biological molecules.
OH-
Hydroxide Affects pH of substances.
Test For Sugars
Benedict’s
Blue - Green - Yellow - Orange - Brick Red
Reducing sugars - all monosaccharides/some disaccharides
1. Add Benedict’s reagent (blue) to a sample and heat in a water bath
2. Positive should be a coloured precipitate, higher concern traction the further the colour change or filter and weigh precipitate
- If its negative, could still be sugar
- New sample, add hydrochloride acid and heat in water bath
- Neutralise with sodium hydrocarbonate
Test For Glucose
Test strips coated in reagents. Test for glucose in urine to indicate diabetes.
Test For Starch
Iodine
Brown/Orange - Blue/Black
Test For Proteins
Biuret
Blue - Purple
1. Add sodium hydroxide solution
2. Copper sulphate solution
Test For Lipids
Cloudy emulsion
1. Shake ethanol with sample
Colourimetry
Quantitive estimate of glucose or reducing sugars can be done with a colourimeter and benedicts. Colourimeters measure strength of a coloured solution.
How to use a colourimeter
- Make serial dilutions by adding glucose to increasingly lower volumes of distilled water
- Benedict’s on every solution and pure water
- Remove red precipitate
- Calibration curve b
Biosensors
A device that uses a biological molecule to detect a chemical. Glucose biosensor.
Chromatography
Mobile phase - molecules can move - solvent
Stationary phase - molecules can’t move - paper
How to do chromatography
- Draw a pencil line near the bottom of the paper - not too far down and place a concentrated spot of the mixture of amino acids on the line
- Roll the paper into a cylinder with the spot on the outside
- Small amount of solvent (water and glacial ethanol acid for amino acids) dip the paper in and cover with a lid to prevent evaporation
- Solvent will move up the paper and solutes will move at different rates
- When the solvent is almost at the top, take the paper out, mark the solvent front with pencil and dry
- If using amino acids - spray with ninhydrin solution to be able to see
- Calculate Rf value
Rf value
Distance travelled by solute/distance travelled by solvent
