Gsce - A Level Transition (Retrival Questions) Flashcards
When is a measurement valid?
When it measures what it’s supposed to be measuring
When is a result accurate?
When it’s close to the true value
What are precise results?
When repeat measures are consistent/ agree closely with each other
What is repeatability?
How precise repeat measurements are when they are taken by the same person using the same equipment under the same conditions
What is reproducibility?
How precise repeated measurements are when they are taken by different people using different equipment
What is the uncertainty of a measurement?
The interval within which the true value is expected to lie
Define measurement error
The difference between a measured value and a true value
What type of error is caused by results varying around the true value in an unpredictable way?
Random error
What is a systematic error?
A consistent difference between the measured values and true values
What does zero error mean?
A measuring instrument gives a false reading when the true value should be zero
Which variable is changed or selected by the investigator?
Independent variable
What is a dependent variable?
A variable that is measured every time the independent variable is changed
Define a fair test
A test where only the independent variable is allowed to affect the dependant variable
What are control variables?
Variables that should be kept constant to avoid them affecting the dependant variable
What are monomers?
Smaller units from which larger molecules are made
What are polymers?
Molecules made from a large number of monomers joined together
What is a condensation reaction?
A reaction that joins two molecules together to form a chemical bond whilst releasing a molecule of water
What is a hydrolysis reaction
A reaction that breaks a chemical bond between two molecules and involves the use of a water molecule
What is a monosaccharide?
Monomers from which larger carbohydrates are made
How is a glycosidic bond formed?
A condensation reaction between two monosaccharides
How is a glycosidic bond formed?
A condensation reaction between two monosaccharides
Name the three main examples of polysaccharides
Glycogen, starch and cellulose
Describe Benedict’s test for reducing sugars
Gently heat a solution of a food sample with an equal volume of Benedict’s solution for five minutes and the solution turns orange/brown is reducing sugar is present
Name the two main groups of lipids
Phospholipids, triglycerides (fats and oils)
Give four roles of lipids
Source of energy, waterproofing, insulation and protection
What is an Ester bond?
A bond formed by a condensation reaction between glycerol and a fatty acid
Describe the emulsion test for lipids
Mix the sample with ethanol in a clean test tube, shake the sample, add water, shake the sample again, a cloudy white colour indicates that lipid is present
What are the monomers that make up proteins?
Amino acids
Draw the structure of an amino acid
(Check camera roll)
How is a peptide bond formed?
A condensation reaction between two amino acids
What is a polypeptide?
Many amino acids joined together
Describe the biuret test for proteins
Mix the sample with sodium hydroxide solution at room temperature, add very dilute copper(II) sulphate solution, mix gently, a purple colour indicates that peptide bonds are present
How does an enzyme affect a reaction?
It lowers the activation energy
Give five factors which can affect enzyme action
Temperature, pH, enzyme concentration, substrate concentration and inhibitor concentration
What is a competitive inhibitor?
A molecule with a similar shape to the substrate, allowing it to occupy the active site of the enzyme
What is a non-competitive inhibitor?
A molecule that changes shape of the enzyme by binding somewhere other than the active site of the enzyme
