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BIOC192 > Labs > Flashcards

Labs Flashcards

1
Q

How does a P1000 pipette work

A

100/1000, add a zero to make measurement in the thousands

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2
Q

How does a P200 pipette work

A

20/200, reading on pipette is measurement in µL (measurement in the hundreds)

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3
Q

How does a P20 pipette work

A

2/20, last number is a zero. Measurement in the 10s

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4
Q

How can dilution factor be calculated

A

Final total volume (V2) / volume of undiluted solution (V1)
Or
Undiluted concentration (c1) / Diluted concentration (c2)

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5
Q

How are C1, C2, V1 and V2 related

A

C1V1 = C2V2

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6
Q

How does heat affect protein structure

A

Increased kinetic energy of molecules, weaker non covalent interactions disrupted

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7
Q

How does pH affect protein structure

A

Ionisable side chains affected, disruption of non covalent interactions (ionic: electrostatic)

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8
Q

What is spectrophotometry

A

Different molecules absorb light at different wavelengths, so spectrophotometry is used to identify molecules present in a solution (based on measurement at a specific wavelength) or to identify unknown molecules in a solution based on their absorbance characteristics

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9
Q

What is an absorbance maxima

A

The particular wavelength that a specific chemical absorbs more than any other wavelength

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10
Q

What is the absorbance reading

A

The log ratio of incident and transmitted light (ratio, so no units)

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11
Q

What is Beer’s law

A

Concentration of a solution is linearly proportional to the absorbance of that solution

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12
Q

What is Lambert’s law

A

The intensity of the transmitted light is linearly proportional to the pathlength

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13
Q

What is the Beer-Lambert Law

A

A = εcl

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14
Q

What are the units of ε

A

L/mol/cm

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15
Q

What is ε

A

Molar absorption coefficient: a measure of how strongly a chemical absorbs light at a particular wavelength. Intrinsic property of the molecule

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16
Q

What is an enzyme assay

A

Measuring enzyme catalytic activity based on appearance of product or disappearance of substrate

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17
Q

What is alcohol dehydrogenase (usually involved in redox, needs a coenzyme for reaction to proceed)

A

An enzyme produced in the liver which breaks down primary alcohols into aldehydes

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18
Q

What is the equation for the reaction involving ADH

A

ethonal + NAD+ -> acetalydehyde +NADH/H+

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19
Q

What is reaction initial velocity

A

Initial velocity of reaction: V0 = ΔA / Δt

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20
Q

What is used to measure reaction initial velocity

A

V0: progress curve for absorbance against time

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21
Q

What graph is used to measure Km and vmax

A

v vs [s] curve

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22
Q

What do competitive inhibitors do to Km and Vmax

A

Increase Km, don’t affect vmax

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23
Q

What do pure non competitive inhibitors do to Km and vmax

A

Don’t affect Km, decrease vmax

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24
Q

What do mixed non competitive inhibitors do to Km and vmax

A

Increase Km and decrease vmax

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25
Q

Which structural component of starch is responsible for the blue black colour in the iodine-starch test

A

Amylose

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26
Q

What does a dilution factor of 6 mean

A

1 part solution, 5 parts water
TOTAL of 6

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27
Q

What is a standard curve

A

Concentration of molecule against absorbance at particular wavelength

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28
Q

A standard curve should be roughly

A

Linear

29
Q

When using enzyme assays to analyse complex solutions for specific molecules, it is assumed that

A

the reaction goes to completion.

30
Q

What is a progress curve

A

Absorbance against time

31
Q

What is the shape of a progress curve

A

Linear to begin with, then exponential decay as substrate concentration decreases over time

32
Q

What unit should V0 be in (progress curves)

A

ΔA/min

33
Q

Volume of enzyme in enzyme assay is directly proportional to

A

Reaction initial velocity

34
Q

What are the two forms of starch

A

Amylose and amylopectin

35
Q

Which amino acid can easily be charged or uncharged at physiological pH and why

A

Histidine as it has a side chain pKa around 6

36
Q

Why do some chemicals appear colourless in solution

A

Because they absorb/reflect wavelengths outside the spectrum our eyes can see

37
Q

Lambert’s law indicates that for monochromatic light passing through an absorbing solution, the intensity of transmitted
light

A

Decreases exponentially with increasing pathlength

38
Q

What is a reference sample (spectrophotometry)

A

Contains everything in an assay except the compound being measured. Used to blank spectrophotometer

39
Q

What can a standard curve be used for

A

To determine the concentration range over which the Beer-Lambert law applies for a particular molecule

40
Q

Why do we want an absorbance maxima that doesn’t overlap with other molecules’

A

So that we can measure the concentration of a single molecule

41
Q

What wavelengths does haemoglobin absorb and reflect

A

Absorbs blue and yellow, reflects red (hence blood appears red)

42
Q

Describe the oxy haemoglobin absorbance spectra

A

2 peaks

43
Q

Describe the deoxy haemoglobin absorbance spectra

A

1 peak

44
Q

Why do oxy and deoxy haemoglobin have different absorbance spectra

A

Because one has oxygen so absorbs light differently

45
Q

How can you best measure a molecule of interest in a mixed solution

A

By measuring absorbance at a wavelength with the greatest difference (e.g secondary peak)

46
Q

What are the 4 types of receptors

A

Ligand gated ion channels, GPCRs, receptor proteins coupled to phosphorylation enzymes (RTKs) and nuclear receptors

47
Q

What is gluco/hexokinase

A

Monomeric enzyme that catalyses phosphorylation of glucose to glucose-6-phosphate

48
Q

What is MODY2 (maturity onset diabetes of the young)

A

A glucokinase variant resulting in decreased sensitivity of pancreatic beta cells to glucose, resulting in less insulin secretion and higher blood glucose levels

49
Q

What glucokinase variant is associated with MODY2

A

E339K (causes ATP binding pocket of enzyme to be blocked)

50
Q

What is a restriction enzyme

A

DNA cutting enzyme which recognises and cuts DNA at its specific site

51
Q

What is DNA gel electrophoresis

A

Separation of DNA fragments by size

52
Q

What is PCR (polymerase chain reaction)

A

Amplification of gene of interest. DNA primers bind upstream and downstream of gene of interest, many copies of a small portion of DNA are made

53
Q

At what level does the body maintain blood glucose

A

3-7 mmolL-1

54
Q

What is a fasting and non fasting blood glucose level indicative of type 2 diabetes

A

> 11mmolL-1 and >8mmolL-1

55
Q

What does HbA1C give a good depiction of

A

Glucose levels over the previous 3 months

56
Q

Extracellular water is approximately ___% of our body weight

A

20

57
Q

What is the unit for HbA1C

A

mmol/mol, because expressed as a ratio of glycosylated haemoglobin to total haemoglobin

58
Q

What HbA1C levels indicate diabetes

A

> 50

59
Q

What HbA1C levels indicate pre diabetes

A

41-49

60
Q

What HbA1C levels are normal

A

<40

61
Q

What is the equation for working out the concentration of a sample when given the absorbance of the sample and reference, and the concentration of the reference

A

conc(sample) = A(sample)/A(reference) * conc(reference)

62
Q

What does the density of lipoproteins refer to

A

Proportion of lipids to proteins in the lipoprotein complex

63
Q

What is “bad” cholesterol and why

A

LDL (carries the majority of cholesterol, can deposit into arterial walls if too high concentration)

64
Q

What is “good” cholesterol and why

A

HDL (carries cholesterol to liver where it is broken down and excreted from the body)

65
Q

How are LDL levels decreased

A

Reducing saturated fat intake

66
Q

How are HDL levels increased

A

Increased exercise, eating poly or monounsaturated fats

67
Q

How can cholesterol levels be measured by an enzyme assay

A

Series of reactions resulting in formation of quinoneimine which is red and absorbs light at 500nm

68
Q

How are proteins electrophoresed

A

Based on isoelectric point (different charges at certain pH allows separation by charge)

69
Q

What assumption is made in order to calculate the concentration of cholesterol in a sample

A

All cholesterol is present in its free form

BIOC192 (5 decks)

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