Gsce - A Level Transition (Retrival Questions)

Question 1

When is a measurement valid?

Answer 1

When it measures what it’s supposed to be measuring

Question 2

When is a result accurate?

Answer 2

When it’s close to the true value

Question 3

What are precise results?

Answer 3

When repeat measures are consistent/ agree closely with each other

Question 4

What is repeatability?

Answer 4

How precise repeat measurements are when they are taken by the same person using the same equipment under the same conditions

Question 5

What is reproducibility?

Answer 5

How precise repeated measurements are when they are taken by different people using different equipment

Question 6

What is the uncertainty of a measurement?

Answer 6

The interval within which the true value is expected to lie

Question 7

Define measurement error

Answer 7

The difference between a measured value and a true value

Question 8

What type of error is caused by results varying around the true value in an unpredictable way?

Answer 8

Random error

Question 9

What is a systematic error?

Answer 9

A consistent difference between the measured values and true values

Question 10

What does zero error mean?

Answer 10

A measuring instrument gives a false reading when the true value should be zero

Question 11

Which variable is changed or selected by the investigator?

Answer 11

Independent variable

Question 12

What is a dependent variable?

Answer 12

A variable that is measured every time the independent variable is changed

Question 13

Define a fair test

Answer 13

A test where only the independent variable is allowed to affect the dependant variable

Question 14

What are control variables?

Answer 14

Variables that should be kept constant to avoid them affecting the dependant variable

Question 15

What are monomers?

Answer 15

Smaller units from which larger molecules are made

Question 16

What are polymers?

Answer 16

Molecules made from a large number of monomers joined together

Question 17

What is a condensation reaction?

Answer 17

A reaction that joins two molecules together to form a chemical bond whilst releasing a molecule of water

Question 18

What is a hydrolysis reaction

Answer 18

A reaction that breaks a chemical bond between two molecules and involves the use of a water molecule

Question 19

What is a monosaccharide?

Answer 19

Monomers from which larger carbohydrates are made

Question 20

How is a glycosidic bond formed?

Answer 20

A condensation reaction between two monosaccharides

Question 21

How is a glycosidic bond formed?

Answer 21

A condensation reaction between two monosaccharides

Question 22

Name the three main examples of polysaccharides

Answer 22

Glycogen, starch and cellulose

Question 23

Describe Benedict’s test for reducing sugars

Answer 23

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

Question 24

Name the two main groups of lipids

Answer 24

Phospholipids, triglycerides (fats and oils)

Question 25

Give four roles of lipids

Answer 25

Source of energy, waterproofing, insulation and protection

Question 26

What is an Ester bond?

Answer 26

A bond formed by a condensation reaction between glycerol and a fatty acid

Question 27

Describe the emulsion test for lipids

Answer 27

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

Question 28

What are the monomers that make up proteins?

Answer 28

Amino acids

Question 29

Draw the structure of an amino acid

Answer 29

(Check camera roll)

Question 30

How is a peptide bond formed?

Answer 30

A condensation reaction between two amino acids

Question 31

What is a polypeptide?

Answer 31

Many amino acids joined together

Question 32

Describe the biuret test for proteins

Answer 32

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

Question 33

How does an enzyme affect a reaction?

Answer 33

It lowers the activation energy

Question 34

Give five factors which can affect enzyme action

Answer 34

Temperature, pH, enzyme concentration, substrate concentration and inhibitor concentration

Question 35

What is a competitive inhibitor?

Answer 35

A molecule with a similar shape to the substrate, allowing it to occupy the active site of the enzyme

Question 36

What is a non-competitive inhibitor?

Answer 36

A molecule that changes shape of the enzyme by binding somewhere other than the active site of the enzyme