Chemistry Pracs Flashcards
What process is used for separating and identifying amino acids in a mixture based on their different chemical characteristics
Thin layer chromatography
What is thin layer chromatography
Where a mobile phase is able to move the component of the mixture that you are trying to separate and there is a stationary phase that the mobile phase moves over and it is interaction between the components of the mixture and the stationary phase that allows the mixture to be separated into the different pure compounds
What are the 3 steps to the thin layer chromatography technique
- Spotting
- Development
- Visualization
What substance was the reactant in TLC
Aspartame
What are the amino acids which make up aspartame
- phenylalanine
- aspartic acid
What are the 2 functional groups in amino acids and describe if they are acidic or basic
acidic carboxylic acid and basic amino group
What binds the mobile phase to the stationary phase
H-bonds
how do you explain the results from thin layer chromatography
The absorbent material is usually silica gel or alumina which contains polar functional groups which can form H-bonds with AA.
So if the AA is polar it will form strong intermolecular bonds and will not travel as high as an amino acid which is not polar.
You compare the distances travelled by the unknown amino acid to distances of known amino acids
What 2 factors affect the migration rate of an amino acid
- solubility of the side chain in the solvent
- Affinity of the amino acid for the stationary phase
Amino acids with similar side chains are supposed to what
move with similar though not identical migration rates
What are the dependent factors of thin chromatography
- Distance travelled by the amino acid
- Distance travelled by the solvent front
how does the solvent (mobile phase) move up the stationary phase
capillary action
What is the stationary phase mostly made up of
silica gel or alumina
What is the stationary phase in thin layer chromatography
the adsorbent material on the TLC plate
What is the solvent front
how far the solvent has traveled along the plate
What is the mobile phase of thin layer chromatography
The solvent (amino acid mixture)
How is the position of the amino acid visualized
Spraying the TLC plate with a ninhydrin solution
What does spraying the TLC plate with ninhydrin solution do
It reacts with the amino group of the amino acid causing it to turn purple (proline not having a primary amine gives a yellow colour)
What is the retention factor (Rf)
quantitative measure to describe the migration of a compound relative to the solvent from the TLC plate. Its the ratio of the distance travels by the amino acid and by the solvent front
What is the equation for the retention factor
Why is is aspartame hydrolyzed with HCl
breaks down aspartame into its amino acids
What is the function of HCl in the hydrolysis of aspartame
catalyst
what is the machine called which measures the absorbance of a chemical solution
spectrometer
This is lecithin
Choline
This is lecithin
Phosphate
This is lecithin
Glycerol
This is lecithin
Hydrophobic tail
This is lecithin
Hydrophilic head
What is the term where a molecule is both hydrophobic and hydrophilic
amphipathic
What is the cell membrane made of
- glycerophospholipids
- proteins
- cholesterol
What are factors which influence the integrity of lipid bilayer/ solution polarity (4)
- Extreme temperatures (heat and cold)
- Extreme pH
- Alcohol
- Detergent
What is the main lipid which comprises the cell membrane
glycerophospholipids
What describes the dynamic nature of a cell membrane
the fluid mosaic model
What cell membrane is used in the experiment which test factors which influence cell membrane function and permeability
cell membrane of beetroot
Why was the beetroot cell membrane chosen
Because changes to membrane fluidity and permeability can be identified quantitatively by the leaking of red-coloured pigments that normally resides inside the cell
What is the name of the beetroot pigment
betanin (a class of betacyanins)
What is the enzyme used in prac 3
a- amylase
What is the function of a-amylase
an enzyme (globular protein) found in saliva that hydrolyses starch into glucose
What are other enzymes found in saliva
lactoperoxidase and lysozyme which exhibit an antimicrobial role
What is the blue-black colour a measure of in prac 3
the formation of a starch-iodine complex (presence of starch - the reaction has not occurred)
However if starch is hydrolyses it will become smaller sugars which don’t form this complex
What are some factors which influence activity of enzymes
-temperature
- pH
What is oxidation
the loss of electrons by a substance, which is said to be oxidised in the process
What is reduction
the gain of electrons by a substance which is said to be reduced in the process
What is an oxidation-reduction reaction
In an oxidation-reduction reaction, electrons re transferred from one species to another, and the valence states or oxidation state of elements are changed in the process.
What are the components of a galvanic cell
- 2 electrodes known as cathode and anode
- solutions in which the electrodes are immersed in
- salt bridge (non-reacting ions that connect the half cells and maintain charge balance)
- Conductor (to transfer the electrons from one electrode to another)
What is the function of a salt bridge in a galvanic cell
It allows ions to travel between the containers to maintain electrical neutrality as negatively charged electrons are moved from one side to the other
What are electrodes
the 2 solid metals that are connected by the external circuit
What is an anode
The electrode where oxidation occurs, this is where electrons are released.
Negatively charged since electrons are negatively charged
What is a cathode
the electrode where reduction occurs. Positively charged since because it appears to attract the negative electrons
What direction does electrons flow in a galvanic cellf
from anode to the cathode
What is the name of the equation which calculates emf
Nernst Equation
What is the equation for Ecell
Ecell = Ecathode - Eanode
What does a positive emf indicate
that reduction occurs on the right in the diagram
What does a negative emf indicate
reduction is occurring on the left (not the normal way though, reduction usually occurs on the right)
What is the function of a conductor in a electrochemical cell
it connects the 2 electrodes
It allows the transfer of electrons from the anode to the cathode
What is the observation of redox of the corrosion of metals (iron)
blue/green at the center
pink on the surface/edges
What indicator was used during the corrosion of metal experiment
ferroxyl indicator
What does the blue colour indicate from the ferroxyl indicator
Anabolic redox reaction - where reduction occurs
What does the pink colour indicate from the ferroxyl indicator
Catabolic redox reaction - where oxidation occurs
Volumetric Flask
Bulb Pipette
Burette
Measuring Cylinder
Graduated Pipette
