Practical Test

Question 1

In spectrophotometry, we know there is a linear relationship between A and c because:

Answer 1

ɛ and l are fixed.

Question 2

True or false, c=nv

Answer 2

False, n = cv

Question 3

What is the name of the law pertaining to spectrophotometry absorption?

Answer 3

Beer-Lambert

Question 4

What is coefficient ɛ in the Beer Lambert-Law?

Answer 4

Molar absorption coefficient

Question 5

What units is ɛ in?

Answer 5

L mol-1cm-1

Question 6

With a higher l (path length), would there be more or less light transmitting through the solution?

Answer 6

Less, as the light is travelling further and hitting more molecules.

Question 7

What is V0 in enzyme kinetics?

Answer 7

The initial reaction velocity.

Question 8

What is on the X axis of a standard curve?

Answer 8

Amount or concentration.

Question 9

In thin layer chromatography, is the cellulose plate polar or non-polar?

Answer 9

Polar.

Question 10

Why do polar amino acids travel less far on cellulose plates?

Answer 10

Polar groups form H bonds with the cellulose.

Question 11

What is normal resting blood glucose?

Answer 11

4-6mM

Question 12

What are three qualities of an enzyme that make it ideal for a lab setting?

Answer 12

1. Stability after extraction from tissue
2. Easily quantifiable and reproducible activity
3. Obtainable in sufficient quantity

Question 13

Why is V0 the only meaningful measurement of enzyme activity for the lab?

Answer 13

After a point, the activity is altered too much by pH, temperature, and concentrations.

Question 14

Which requires more complex equipment - a continuous or stopped assay?

Answer 14

Continuous assay.

Question 15

What is the major assumption of a stopped assay?

Answer 15

Enzyme activity is linear over the time period of the assay.

Question 16

What was the substrate in the enzymes lab?

Answer 16

P-NPP (p-nitrophenol phosphate)

Question 17

How was P-NPP converted to P-NP in lab 3?

Answer 17

Phosphatase removed a phosphate.

Question 18

What is the dual purpose of adding NaOH in the stopped assay of Lab 3?

Answer 18

1. Denature phosphatase to stop the reaction.
2. Ionise P-NP to produce a yellow colour.

Question 19

Glycolysis is the pathway that converts glucose to ______.

Answer 19

Pyruvate.

Question 20

Why is lactate measured in the glycolysis lab?

Answer 20

The amount of lactate formed is a measure of glycolytic activity.

Question 21

Why is perchloric acid added to the muscle extract incubation in the glycolysis lab?

Answer 21

To denature the enzymes and terminate glycolytic activity.

Question 22

True or false, the rat muscle extract incubation is followed by lactate assays in the glycolysis lab.

Answer 22

True.

Question 23

What purpose does the LDH enzyme serve in the lactate assay of the glycolysis lab?

Answer 23

LDH oxidises lactate to pyruvate, in turn reducing NAD+ to NADH.

Question 24

How is absorbance at 340nm a useful measurement in the lactate assay of the glycolysis lab?

Answer 24

LDH reduces NAD+ to NADH, and NADH absorbs strongly at 340nm. Thus, changes in absorbance at 340nm help us determine the amount of lactate produced in the initial muscle extract incubations, as the amount of NADH formed is equal to the amount of lactate.

Question 25

What is the overall purpose of the muscle extract incubations and lactate assays in the glycolysis lab?

Answer 25

To reveal the cofactor requirements for glycolysis.

Question 26

Why is TLC so good at separating different amino acids?

Answer 26

Different side chain polarities.

Question 27

Which one carries the mixture (of amino acids, say) up the absorbent plate - stationary or mobile phase?

Answer 27

Mobile phase (consisting of solvents)

Question 28

What does the foil do in TLC?

Answer 28

Prevents the evaporation of the solvent.

Question 29

What is the Rf value in TLC?

Answer 29

Distance travelled by solute (amino acid) over distance travelled by solvent.

Question 30

Would polar amino acids have a lower or higher Rf value?

Answer 30

Lower.

Question 31

What is phenylketonuria?

Answer 31

Mutation that prevents the conversion of phenylalanine to tyrosine, leading to an accumulation of phenylalanine. Untreated, it will lead to intellectual disabilities and low life expectancy.

Question 32

How does the GTT work?

Answer 32

Patient is given a large single dose of glucose. The following hyperglycaemia (increase in blood sugar) is measured and compared to healthy levels.

Question 33

In a healthy patient, does the ingestion of glucose lead to secretion of insulin?

Answer 33

Yes.

Question 34

What does insulin do, in regards to hyperglycaemia?

Answer 34

Increases glucose uptake, storage, and metabolism in tissues (especially liver, muscle, and adipose tissues).

Question 35

Type 1 diabetes is a failure to respond to insulin, Type 2 is a result of low insulin secretion. T or F?

Answer 35

False, other way around.

Question 36

No coffee, tea, nicotine, or alcohol before GTT... why?

Answer 36

These substances (and excitement) affect adrenaline action, which increases blood glucose. Caffeine also inhibits the breakdown of cyclic-AMP.

Question 37

What are the two enzymes involved in the blood glucose concentration assay?

Answer 37

Hexokinase and glucose 6-phosphate dehydrogenase.

Question 38

How are glucose levels measured in the blood glucose concentration assay? (hint: similar to another lab)

Answer 38

For every molecule of glucose converted by the two enzymes, an NADH is formed. This can be measured spectrophotometrically at 340nm.

Question 39

What is the purpose of the glycine/hydrazine buffer in the glycolysis lab lactate assay?

Answer 39

Raise pH significantly and add NAD+ to the solution, pushing the reaction equilibrium to favour NADH production which we can measure spectrophotometrically.

Question 40

The addition of which co-factor leads to more lactate formation, GAP or 1,3BPG?

Answer 40

GAP produces a lot of lactate, 1,3BPG produces barely any.

Question 41

Why does starting the glycolytic pathway from 1,3BPG lead to very little lactate formation?

Answer 41

1,3BPG does not recycle NAD+ to NADH (like GAP does). Thus, the reaction simply consumes this cofactor and does not regenerate NAD+ for continuous formation of lactate.