Biological Molecules Flashcards
What is a covalent Bond ?
2 atoms share a pair of electrons
what is an ionic bond ?
1 atoms in the pair donates an electron and the other receives it
What is a cation ?
atoms loses electrons and has a positive charge
what are the roles of cations ?
calcium - nerve impulse transmission, muscle contraction
potassium + sodium - nerve impulse transmission
What is an anion ?
atoms gain electrons and have a negative charge
what is the structure of water
- 2 atoms of hydrogen covalently bonded to one atom of oxygen
- polar molecule
- weakly negative charge on oxygen atom
- weakly positive charge on hydrogen atom
what are hydrogen bonds
- form between water molecules
- weak bonds
- very few bonds
high latent heat of evaporation of water
- very high boiling point
- takes a lot of energy to increase the temperature and break hydrogen bonds to become a gas and evaporate
- only need to evaporate little water to lose heat
- provides cooling effect for living organisms
water is less dense when it is a solid
- hydrogen bonds hold water molecules further apart than in liquid
- giant rigid open structure
- solid that is less dense than liquid - ice floats
- forms insulating layer so water below doesn’t freeze
high specific heat capacity of water
- the amount of thermal energy needed to raise the temperature of 1kg of a substance by 1oc
- lots of thermal energy can break and build hydrogen bonds
- provides suitable habitats - maintains constant temperatures
water is a good solvent
- positive water molecule is attached to a negative ion
- negative water molecule is attached to a positive ion
- ions are surrounded by water molecules and will dissolve
- ions can dissolve in the water in the blood and then transported around the body
what is cohesion
- moves as one mass as molecules are attached to each other
- transpiration
what is adhesion
- water molecule are attracted to other properties
what is a monomer
- many small molecules from which larger molecules are made
what are polymers
molecules made from a large number of monomers joined together in a chain
what is a condensation reaction
- monomers are joined together by covalent bonds to form polymers/macromolecules and water is removed
- dehydration synthesis
what is a hydrolysis reaction
covalent bonds are broken when water is added
what are monosaccharides
- single sugar unit
- glucose, fructose, ribose
what are disaccharides
- two monosaccharides linked together
- lactose, sucrose
what are polysaccharides
- many monosaccharides linked together
- glycogen, cellulose, starch
what is the structure of glucose
- hexose monosaccharide - 6 carbons
- isomer - alpha and beta glucose
- alpha glucose - OH below the ring
- beta glucose - OH above the ring
what are pentose monosaccharides
- sugars that contain 5 carbon atoms
- deoxyribose and ribose
how is the glycosidic bond formed
- condensation reaction and removal of 1 water molecule
- catalysed by enzymes specific to which OH groups are interacting
- maltose has alpha 1-4 glycosidic bonds
- sucrose has alpha 1-6 glycosidic bonds
how is the glycosidic bond broke
- water is added in a hydrolysis reaction
- catalysed by enzymes
what makes up starch
- amylase
- amylopectin
what is the structure of amylase
- 10-30% of starch
- unbranched helix
- 1-4 glycosidic bonds between alpha glucose molecules
- more compact and more resistant to digestion
what is the structure of amylopectin
- 70-90% of starch
- 1-4 glycosidic bonds between alpha glucose molecules
- 1-6 glycosidic bonds
- branched molecule
what is the structure of glycogen
- made of alpha glucose
- 1-4 and 1-6 glycosidic bonds
- more branched - releases glucose quicker
what is the structure of cellulose
- polysaccharide found in plants
- long chains of beta glucose molecules joined by 1-4 glycosidic bonds
- to form 1-4 bonds consecutive beta glucose molecules must be rotated 180oC to each other
- several hydrogen bonds = high tensile strength
what is the function of starch
- insoluble
- compact
- storage polysaccharide in plants
what is the function of glycogen
- storage polysaccharide of animals/fungi
- compact
- highly branched
- branching enables more free ends where glucose molecules can be added or removed for faster condensation and hydrolysis
what is the function of cellulose
- main structural component of cell walls
- several hydrogen bonds between microfibrils
- high tensile strength - cell walls withstand pressure
- lignin for strengthened cell walls
how do you test for reducing and non - reducing sugars
- place sample in boiling water
- add equal volume of benedict’s reagent
- heat mixture gently in a water bath for 5 minutes
Red = high concentration of reducing sugar
Yellow/orange = medium concentration of reducing sugar
Green = low concentration of reducing sugar
Non-reducing sugars = don’t react with benedict’s reagent and final colour is blue
how do you test for the presence of starch
- iodine test
- add a few drops of iodine mixed in potassium iodide solution to a sample
Purple/Black = starch is present
Yellow/Brown = no starch present
what are lipids
- contain carbon, hydrogen, oxygen
- non-polar molecules
- not soluble
what are triglycerides
- combines 1 glycerol molecule and 3 fatty acids
- both molecules contain hydroxyl groups - formation of 3 water molecules and bonds between fatty acids and glycerol
- non polar-hydrophobic molecules
what is a saturated fatty acid
- no double bonds between carbon atoms
- all carbon atoms form the maximum number of bonds with hydrogen atoms
what is an unsaturated fatty acid
- double bonds between some of the carbon atoms
- one double bond = monosaturated
- two or more double bonds = polysaturated
- double bonds cause the molecule to kink
what are phospholipids
- contain phosphorus, carbon, hydrogen, oxygen
- soluble in water due to the presence of inorganic phosphate ions
- one fatty acid chain replaced with a phosphate group
-fatty acid tails - phosphate heads
- form a phospholipid bilayer
what is the role of lipids
- membrane formation
- hydrophobic barriers
- electrical insulation for impulse transmission
- waterproofing (plant leaves)
- thermal insulation to reduce heat loss
- cushion to protect organs (heart, kidneys)
- Buoyancy for aquatic animals - float
how do you test for lipids
- emulsion test
- add ethanol to sample to be tested
- shake to mix
- add mixture to a test tube of water
Clear solution = no lipids present
Milky solution = lipids present
what are proteins
- polypeptides made up of monomers : amino acids
- important for cell growth, cell repair , structure
how are peptides synthesised
- amino acids join when amine and carboxylic acid groups connect to the central group and react
- hydroxyl in carboxyl group of one amino acid reacts with hydrogen in the amine group
- peptide bond formed between amino acids produces water
what is the primary sequence of a protein
- amino acids are joined
- amino acids influence how the polypeptide will fold
- determines function
- peptide bonds
What is the secondary sequence of a protein
- oxygen, hydrogen and nitrogen of the structure react
- form alpha helix or beta pleated sheets by hydrogen bonds
what is the tertiary sequence of a protein
- folding of protein into its final shape
- coils or folds further
-hydrophobic and hydrophilic interactions
- hydrogen bonds
- ionic bonds
- disulphide bonds
what is the quaternary structure of a protein
proteins that have more than one polypeptide chain
what are globular proteins
- compact
- water soluble
- spherical
- fold
- essential for metabolic reactions
what is a conjugated protein
- contains a prosthetic groups
Haemoglobin ]- 4 polypeptides
- haem group containing iron that can combined reversibly with oxygen
what are fibrous proteins
- long polypeptide chains
- little or no tertiary structure
- highly repetitive amino acid sequence = very organised strong insoluble properties
Keratin - in skin and nails
Elastin - blood vessels and alveoli
how do you test for proteins
- biuret test
- add sodium hydroxide to food sample to make alkaline
- add a few drops of copper sulphate solution
- repeat the first steps using a control solution
- Blue to Lilac = protein
- no change = no protein
