Clinical Chemistry I Exam 1

Front 1

8 steps in obtaining a laboratory test

Back 1

1. test order placed
2. patient identified/sample collected and labeled
3. specimen transported to lab
4. specimen accessioned
5. specimen processed
6. specimen analyzed
7. result reviewed and verified
8. result released

Front 2

Types of samples for chemical analysis

Back 2

whole blood, serum, plasma, urine, other fluids (i.e. CSF, amniotic fluid, saliva, etc.)

Front 3

Serum

Back 3

supernatant obtain if blood sample is allowed to clot and then centrifuged

free of fibrinogen

Front 4

Plasma

Back 4

clear yellow supernatant obtained by centrifuging a blood sample that has been treated with an anticoagulant

does have fibrinogen
has more protein than serum

Front 5

Which sample is usually preferred in the industry - plasma or serum?

Back 5

plasma, mostly due to the time it takes serum to clot before processing

Front 6

Anticoagulant

Back 6

substance the suppresses, delays or prevents coagulation of blood by preventing the formation of fibrin

Front 7

Preservative

Back 7

chemical that prevents a change in the concentration of analytes in a sample of blood, urine or other body fluid

Front 8

Additive

Back 8

chemical added to a specimen that changes one or more of its physical or chemical properties

Front 9

Red-top collection tube

Back 9

no anticoagulant or preservative, used for collecting serum, need 20 minutes for clotting before centrifugation, mostly used for blood bank speciments, some chemistries (drugs, trace metals)

Front 10

Gold-top and tiger-top collection tubes

Back 10

SST, contains a gel that forms a physical barrier between the serum and cells after centrifugation, no other additives, can be used for most chemistry analysis but gel affects some lab tests

Front 11

Gray-top collection tube

Back 11

sodium fluoride and potassium oxalate OR sodium iodoacetate, cannot use for electrolytes (iodoacetate has less of an effect), stabilizes glucose in plasma

Front 12

Sodium fluoride and potassium oxalate

Back 12

inhibits enolase

Front 13

Sodium iodoacetate

Back 13

inhibits G-3-P dehydrogenase

Front 14

Green-top collection tube

Back 14

sodium, ammonium or lithium salt of heparin, anti-coagulant

Front 15

Lithium heparin

Back 15

Most common anti-coagulant in chemistry laboratory, inhibits thrombin

Front 16

Lavender-top collection tube

Back 16

EDTA anti-coagulant, cannot use for any divalent cations or sodium/potassium, only required for hemoglobin analysis

Front 17

Light blue-top collection tube

Back 17

sodium citrate anti-coagulant, causes problems with almost all chemistry analytes

Front 18

Sodium citrate

Back 18

anti-coagulant which chelates calcium and inhibits coagulation, used for coagulation studies, not used in chemistry

Front 19

Which anticoagulant is pH neutral?

Back 19

lithium heparin

Front 20

What are some laboratory systems that are utilized to avoid patient and sample identification errors?

Back 20

bar code labeling, delta checks, criteria for sample acceptance/rejection

Front 21

What type of analyte is required for delta check analysis?

Back 21

Analytes that do not change drastically from day to day

Front 22

What are some preanalytical errors that occur during blood collection?

Back 22

prolonged tourniquet application, improper site of draw (above IV, for example), improper order of draw, improper time of day, use of improper tube, incomplete filling of tubes, improper antiseptic use (i.e. when testing for alcohol)

Front 23

What analytes are affect by diurnal variation?

Back 23

iron, cortisol and other hormones, glucose, etc.

Front 24

What analytes are affected by posture?

Back 24

Proteins decrease when standing

Front 25

What analytes are affect by diet?

Back 25

glucose, lipids, electrolytes, phosphorus, hormones, etc.

Front 26

What analytes will be affected by physical training?

Back 26

protein, creatinine, lactic acid, uric acid, creatinine kinase

Front 27

What analytes will be affected by smoking?

Back 27

ammonia, CEA, glucose, GH, urea

Front 28

What analytes will be affected by gender?

Back 28

hormones, calcium, iron

Front 29

What analytes will be affected by age?

Back 29

ALP (released from bone during growth), creatinine (renal function)

Front 30

What analytes will be affected by alcohol intake?

Back 30

GGT, Glucose, Triglyceride

Front 31

What are analytical variables that can affect the reliability of results?

Back 31

anticoagulant used, sample integrity, instrument functioning, method accuracy and reliability, following SOP correctly

Front 32

Lipemic sample

Back 32

turbid sample due to increased triglyceride, dilutes plasma or serum analytes, can only be used for lipid analysis until lipids removed by ultracentrifugation, can be confused with turbidity due to protein

Front 33

Icteric sample

Back 33

yellow sample due to increased bilirubin, affects colorimetric assays

Front 34

Hemolyzed sample

Back 34

red sample due to hemoglobin, falsely increases potassium, phosphorus and decreases glucose, also affects colorimetric assays

Front 35

What are postanalytical variables that can affect the reliability of results?

Back 35

accurate reporting, accurate transfer of information electronically (from LIS to HIS), timeliness of result verification, appropriate flagging of results

Front 36

Photometry

Back 36

Measurement of intensity of light falling on a surface from a source without consideration of wavelength

Front 37

Spectrophotometry

Back 37

Measurement of intensity of light at a selected wavelength

The mostly widely used automated method in the clinical chemistry laboratory.

Front 38

Two principles spectrophotometry is based on

Back 38

Substances absorb light at unique wavelengths

Amount of light absorbed is proportional to the concentration

Front 39

Light is electromagnetic radiation or photons of energy and it behaves like a....

Back 39

wave

Front 40

Wavelength of light equals...

Back 40

the distance between identical sites on a consecutive wave (i.e. peak to peak or trough to trough)

Front 41

Relationship between wavelength and energy

Back 41

Energy in Ergs = Planck's constant x Frequency of light in cycles per second

Front 42

Energy and wavelength are ______ related to each other

Back 42

inversely

E = hc / lambda

Front 43

UV has a _____ wavelength and a _____ energy than visible light

Back 43

lower, higher

Front 44

Wavelength < 190nm

Back 44

X rays and gamma rays

Front 45

Wavelength 190-390 nm

Back 45

UV

Front 46

Absorption

Back 46

electromagnetic radiation is assimilated by a substance (neither reflected or transmitted)

Front 47

Wavelength 380 - 750 nm

Back 47

Visible light

Front 48

Wavelength > 750 nm

Back 48

Infrared

Front 49

When an atom or molecule absorbs a photon...

Back 49

valence electrons are raised from a low energy orbital (ground state) to a higher energy orbital (excited state) by absorbing the energy of the photon, changes occur in the vibration and rotation of covalent bonds, excited electron will fall back to ground state by emitting energy (transmittance)

Front 50

% Transmittance

Back 50

I sample / I incident x 100

OR

T/I x 100

Front 51

Each succuessive layer of solute absorbs a _____ % of light incident on it

Back 51

constant

Front 52

Beer's law

Back 52

concentration of a substance is directly proportional to the amount of light absorbed or inversely proportional to the logarithm of the transmitted light

Absorbance = proportionality constant (L/mol x cm) x length of light path (cm) x concentration (mol/L)

Front 53

Absorbance varies with...

Back 53

concentration, pH and temperature

Front 54

Relationship between absorbance and %T

Back 54

A = 2 - log %T

Front 55

Assumptions of Beer's law

Back 55

light striking the solute is only one wavelength

solute being analyzed is the only colored solute present in the solution

light being measured comes only from the analytical beam of light

Front 56

Single calibrator method

Back 56

A unknown / A calibrator = C unknown / C calibrator

Front 57

Tungsten and Tungsten Halogen lamp

Back 57

320 to >1000 nm (Visible and near IR)

Front 58

Xenon lamp

Back 58

200 to 800 nm (UV and visible)

Front 59

Deuterium-discharge & hydrogen lamp

Back 59

165 to 450 nm (UV)

Front 60

Mercury-arc lamp

Back 60

UV and visible range

Front 61

Laser

Back 61

Light amplification by stimulated emission of radiation

intense and focused beam of light of very specific wavelength

Used commonly for hormones and drugs

Front 62

Monochromator

Back 62

system that isolates radiant energy of desired wavelength and excludes other wavelengths

Front 63

In a monochromator, the degree of wavelength isolation is dependent on.....

Back 63

the width of entrance and exit slits

Front 64

Spectral bandpass/bandwidth

Back 64

Defines the range of wavelengths that will be transmitted

lower number means less interference

calculated as the width in nm of the spectral transmittance curve at a point equal to one-half peak transmittance

Front 65

A chromagen absorbs the wavelength that corresponds to...

Back 65

the energy level of its electrons

Front 66

Types of fixed wavelength monochromators

Back 66

colored glass/plastic, interference filter

Front 67

How does an interference filter work?

Back 67

Uses constructive interference to create reinforced waves of desired wavelength. The filter transmits the wavelength that is an even multiple of the distance between its sides. (spectral bandwidth between 5 and 15 nm)

Front 68

Types of variable wavelength monochromators

Back 68

prisms, diffraction grating

Front 69

Prisms are now commonly used in spectrophotometry (T/F)

Back 69

False, they are rarely used anymore

Front 70

How does diffraction grating work?

Back 70

It is based on the principle that wavelengths bend as they pass through a sharp corner; short wavelengths are diffracted through a small angle while large wavelengths are diffracted through a large angle.

Front 71

What are the properties of an ideal cuvet?

Back 71

square with plane-parallel optical surfaces and a constant light path, scratch-resistant, transmits essentially all incident light

Front 72

What do detectors in spectrophotometers do?

Back 72

Convert light energy into electrical energy by allowing light to hit the surface and dislodge electrons, producing a current or potential difference which may then be measured

Front 73

What are quality assurance procedures that must be performed on spectrophotometers?

Back 73

Checks on wavelength accuracy, stray light, detector function and linearity

Front 74

When is bichromatic analysis used?

Back 74

when interfering chromogens are present (hemolysis, lipemia, etc.)

Front 75

How does bichromatic analysis work?

Back 75

Light beam is split in two and a different wavelength is selected for each beam.
One wavelength is desired peak of analyte, other wavelength is peak of interfering chromogen. Subtract second wavelength from first to determine concentration of analyte.

Front 76

Serum blank

Back 76

use serum instead of water for blank, used for colored serum (lipemic, hemolyzed)

Front 77

Hemolyzed samples are not appropriate for which studies?

Back 77

Electrolytes (especially potassium), LD

Front 78

Reagent blank

Back 78

If you have a colored reagent, use it for a blank instead of water

Front 79

Standard deviation

Back 79

Quantifies the degree of dispersion of data points about the mean

Front 80

Coefficient of variation

Back 80

% cv = standard deviation/mean X 100

Measure of variability expressed as a percentage

Front 81

Frequency histogram

Back 81

Graphical representation of data, values on x-axis versus number of time the value is obtained on the y-axis

Front 82

Normal distribution

Back 82

equal number of values above and below the mean, Gaussian curve (bell-shaped) where one standard deviation includes 68.2% of the data, two standard deviations include 95.5% of the data and three standard deviations include 99.7% of the data

Front 83

Range

Back 83

difference between the highest and lowest values in the sample of population

Front 84

When are parametric statistics used?

Back 84

when variability is known

Front 85

Inferential statistics

Back 85

Summarize data to draw logical conclusions about a population from a sample

Used to compare features of two or more groups of data

Front 86

Method evaluation parameters

Back 86

Linearity, method comparison experiment, reference range establishment or validation, analytic sensitivity, specificity, predictive value

Front 87

Linearity (Analytical Measurement Range)

Back 87

Also known as dynamic range. Concentration range over which measured concentration is equal to actual concentration.

Front 88

How are linearity studies performed?

Back 88

By assaying a set of standards in duplicate or triplicate with concentrations focused at specific points (medical decision points) then graphing expected concentration (x-axis) versus mean of results (y-axis). A 45 degree angle confirms linearity.

Front 89

Comparison of two testing methods

Back 89

Compare new method and old method by running at least 40 samples using both methods and compare the two sets of results

Front 90

When comparing two test methods, analysis must be completed within...

Back 90

2 to 4 hours by both methods

Front 91

What type of samples must be used when comparing two test methods?

Back 91

At least 50% abnormal, with half of those values low and half high

Front 92

Total error

Back 92

Random error + Systematic error

Front 93

Random error

Back 93

present in all measurements with no pattern; due to instrument, operator or environment

Front 94

Systematic error

Back 94

consistent error in one direction, should not be present in a method, can be proportional or constant

Front 95

Accuracy

Back 95

Obtaining the true value, method comparison study, recovery study or linearity check usually verifies accuracy

Front 96

Precision

Back 96

Reproducibility, estimated by running a sample of known concentration repeatedly

Front 97

Linear regression method comparison analysis

Back 97

Plot results of new method (y) versus old method (x), results should agree within 5%

Front 98

In linear regression method comparison analysis, the y-intercept represents _____ error and the slope represents _____ error

Back 98

constant, proportional

Front 99

Purpose of recovery experiment

Back 99

Used to look for effect of unknown interfering substance,

Front 100

How is a recovery experiment performed?

Back 100

Divide sample in two parts then add known amount of pure analyte to one sample (spiked). Analyze both samples and calculate percent recovery:

amount recovered/amount added x 100 = percent recovery

95-105% = no interference

Front 101

How is the total allowable error determined for each analyte?

Back 101

CLIA 88 (see pages 459-461 in text)

Front 102

What are the two sub-types of systematic error?

Back 102

constant and proportional

Front 103

The correlation coefficient r is utilized for what?

Back 103

to show the strength of the relationship or correlation between x and y variables

Front 104

What is indicated by r=0?

Back 104

There is no relationship between the x and y variables

Front 105

When comparing a new method and old method of testing, what is an acceptable r value?

Back 105

0.95 to 1.05 (positive or negative)

Front 106

What is the equation for systematic error?

Back 106

SE = constant error + proportional error

Front 107

What is the equation for proportional error as obtained from a linear regression model?

Back 107

PE = (slope - 1) x 100

Front 108

What is the constant error as obtained from a linear regression model?

Back 108

CE = y-intercept

Front 109

Standard error of the estimate compares...

Back 109

the values obtained and the values expected based on the linear regression model

this is a measure of random error/precision

Front 110

Parametric statistics are used when...

Back 110

variability is known

Front 111

The t-test determines what?

Back 111

statistically significant difference between means of two groups, used for accuracy

Front 112

The f-test determines what?

Back 112

statistically significant difference between standard deviations of two groups, used for precision

Front 113

Chi square is a parametric method (T/F)

Back 113

False, it is a nonparametric method

Front 114

Chi square indicates what?

Back 114

the statistical significance if probability of difference between calculated value and critical value is less than 5%

Front 115

105% recovery is acceptable in a recovery experiment (T/F)

Back 115

True, 95-105% recovery is acceptable and indicates no interference

Front 116

Equation for percent recovery

Back 116

amount recovered/amount added x 100 = percent recovery

Front 117

Why is a percent recovery experiment usually performed?

Back 117

to check for interfering substances

Front 118

The analytic sensitivity or detection limit

Back 118

the smallest concentration of an analyte that can be measured accurately by an instrument or method

Front 119

Analytic specificity

Back 119

the method's ability to measure the analyte of interest

Front 120

Method of developing predictive value

Back 120

evaluate analytes on large group of patients with the disease and large group of patients that do not have the disease

Front 121

Diagnostic sensitivity

Back 121

probability of a positive result if the disease is present

Sensitivity = true positive / (true positive + false negative) x 100

Front 122

Diagnostic specificity

Back 122

probability of negative result if the disease is not present

Specificity = true negative/ (true negative + false positive) x 100

Front 123

Positive Predictive Value

Back 123

true positives/all positives x 100

Front 124

Negative Predictive Value

Back 124

true negatives/all negatives x 100

Front 125

Method of developing predictive value

Back 125

evaluate analytes on large group of patients with the disease and large group of patients that do not have the disease

Front 126

Diagnostic sensitivity

Back 126

probability of a positive result if the disease is present

Sensitivity = true positive / (true positive + false negative) x 100

Front 127

Diagnostic specificity

Back 127

probability of negative result if the disease is not present

Specificity = true negative/ (true negative + false positive) x 100

Front 128

Positive Predictive Value

Back 128

true positives/all positives x 100

Front 129

Negative Predictive Value

Back 129

true negatives/all negatives x 100

Front 130

Define reference range

Back 130

the acceptable range of an analyte or acceptable result of a lab test for a healthy patient

this range differentiates between sick and well

Front 131

Data must be stratified when determining a reference range (T/F)

Back 131

True, data must initially be stratified by age and gender in order to determine if reference ranges must be separate

Front 132

How often must a reference range be validated after it is established?

Back 132

Every year with at least 20 samples

Front 133

Parametric studies can only be used if the frequency distribution is _______

Back 133

Gaussian (normal)

Front 134

With a Gaussian distribution, reference range = 95% of the group = ______

Back 134

mean +/- 2 standard deviations

Front 135

The receiver operating characteristic curve (ROC) plots...

Back 135

sensitivity versus 100% - specificity

greater area under curve indicates better test

Front 136

For a screening test, is sensitivity or specificity more important?

Back 136

Sensitivity

Front 137

For a confirmatory test, is sensitivity or specificity more important?

Back 137

Specificity

Front 138

Fluorometer

Back 138

instrument that detects fluorescent emissions, often used in clinical laboratory in highly automated immunoassay systems for measurement of drugs, hormones, etc.

Front 139

There are two curves that are present on a fluorometer graph of absorbance versus wavelength, what do they represent?

Back 139

the light emitted from the light source (higher energy, lower wavelength), the light emitted from the sample (lower energy, higher wavelength)

Front 140

Types of lamps used in fluorometer

Back 140

halogen - least expensive
xenon - most used
laser - most expensive

Front 141

The light source (lamp) and detector in the fluorometer are at what angle from each other?

Back 141

90 degree

Front 142

Fluorescence and concentration are ______ proportional

Back 142

directly

Front 143

Advantages of fluorometry

Back 143

High sensitivity and specificity

Front 144

Disadvantages of fluorometry

Back 144

very sensitive to environmental changes: pH, temperature, contamination

Front 145

Chemiluminescence

Back 145

chemical reaction that emits light

Front 146

Advantages of chemiluminescence

Back 146

quick, very low detection limits, one step reactions, simple

Front 147

Disadvantages of chemiluminescence

Back 147

impurities can cause background signals and decrease the sensitivity and specificity

Front 148

Nephelometry

Back 148

amount of light scattered as it passes through the particulate solution

Front 149

Turbidometry

Back 149

Measures decrease in the amount of light as it passes through a particulate solution

Front 150

Turbidometry can measure the presence of soluble particles (T/F)

Back 150

False, turbidometry can only measure the presence of insoluble particles

Front 151

Turbidometry measures at an angle of _______ to the light source, while nephelometry measures at an angle ________ to the light source

Back 151

180 degrees, other than 180 degrees

Front 152

Limitations of nephelometry and turbidometry

Back 152

lipemic, hemolyzed or contaminated specimens not recommended

improper centrifugation may cause interference

sample cuvettes must be clean/free of scratches

Front 153

Reflectance spectrophotometry

Back 153

spectrophotometric technique in which light is reflected from the surface of a reaction and used to measure the amount of the analyte

Front 154

Hemoglobin A is what percentage of hemoglobin in the body?

Back 154

80%

Front 155

The glucose oxidase-peroxidase method is specific for what type of glucose?

Back 155

Beta-D-glucose

Must allow alpha-D-glucose to be converted to beta-D-glucose before measuring

Front 156

Oxidating agents produce a falsely _____ glucose result in the glucose oxidase-peroxidase method

Back 156

elevated

Front 157

Reducing agents produce a falsely _____ glucose result in the glucose oxidase-peroxidase method

Back 157

decreased

Front 158

Absorbance for NADH or NADPH is always measured at what wavelength?

Back 158

340 nm

Front 159

Benedict's copper reduction reaction measures what?

Back 159

Glucose reducing cupric ions to cuprous ions. This produces a yellow or red cuprous compound.

Front 160

What substances would interfere with the Benedict's copper reduction reaction test for glucose?

Back 160

Any other reducing agent (including other reducing sugars)

For this reason, it is only used for babies under the age of one (in order to check for all metabolic sugar disorders)

Front 161

The reference method for glucose determination is ______

Back 161

hexokinase

Front 162

Hb A1c estimates the average blood glucose over ________

Back 162

2-3 months (lifespan of the red blood cell)

Front 163

The goal of diabetes therapy is a result of Hb A1c less than ____

Back 163

7%

Front 164

Methods to separate glycated hemoglobin

Back 164

ion-exchange or affinity chromatography, electrophoresis, isoelectric focusing, high-pressue liquid chromatography, immunoassay

Front 165

Ion-exchange chromatography is extremely sensitive to _______

Back 165

temperature

Front 166

Affinity chromotagraphy utilizes _____ as a reagent to bind ________

Back 166

boronic acid, glycosylated protein

Front 167

EDTA

Back 167

Chelates divalent cations to prevent coagulation

produces falsely low iron, Ca and Mg results

Front 168

Apoferritin

Back 168

protein that binds iron in storage, called ferritin when iron is bound

Front 169

Transferrin

Back 169

glycoprotein that binds iron in circulation for transport

known as apotransferrin when iron is not bound

Front 170

Hepcidin

Back 170

regulator molecule for iron intake

as hepcidin decreases, iron intake increases and splenic iron is released

Front 171

Serum iron is sensitive to the ______ stage of iron deficiency

Back 171

mild

Front 172

Serum iron levels _____ after body stores are fully depleted but _______ hemoglobin levels drop

Back 172

decrease, before

Front 173

Serum transferrin is ______ in iron deficiency

Back 173

increased

Front 174

Each transferrin binds _____ molecules of iron

Back 174

2

Front 175

Transferrin saturation is the ratio of _______ to _______

Back 175

serum iron, iron-binding capacity

Front 176

Transferrin saturation is the most accurate indicator of ________

Back 176

iron supply to the bone marrow

Front 177

The Serum Transferrin Receptor Assay indicates _______. The circulating sTfR becomes _____ in iron deficiency.

Back 177

the cells' need for iron, elevated

Front 178

The best diagnostic test for iron deficiency is _________

Back 178

serum ferritin because it measures iron stores in the body

Front 179

For serum ferritin, a concentration below ______ indicates iron deficiency

Back 179

12 micrograms/L

Front 180

The R/F ratio measures what?

Back 180

the sTfR/serum ferritin ratio

It is used to provide an estimate of iron stores.

Front 181

The R/F ratio test may be adversely affected by?

Back 181

oral contraceptives, inflammation

Front 182

Special collection considerations for iron measurement

Back 182

early morning collection, no hemolysis, fasting

Front 183

Steps in colorimetric measurement of iron

Back 183

1. Add acid to remove iron from transferrin

2. Add reducing agent to convert Fe3+ to Fe2+

3. Add an oxidized dye than can be reduced to cause a color change which can be measured colorimetrically

Front 184

Lead poisoning blocks the heme synthesis pathway at what point(s)?

Back 184

Alpha-ALA dehydratase, Coproporphyrinogen oxidase, Ferrochelatase

Front 185

% saturation of transferrin =

Back 185

serum iron/TIBC * 100

Front 186

UIBC =

Back 186

TIBC - Serum iron

Front 187

Special considerations for collection of lead testing samples

Back 187

Must use lead-free needle, metal free collection tube (royal blue), prevent post-collection contamination

Front 188

Best test for detection of lead exposure and reference range

Back 188

whole blood lead measurement

<10 mcg/dL normal in children
>10 mcg/dL toxicity indicated
>30 mcg/dL in adults indicates significant exposure

Front 189

Free erythrocyte protoporphyrin assay (EPP) is not useful as a screening test for lead exposure because ________

Back 189

it is not a sensitive indicator of low-level lead (<35 mcg/dL)

Front 190

The common feature of all porphyrias

Back 190

excess accumulation of porphyrins or porphyrin precursors in the body

Front 191

When testing for plasma glucose, the plasma must be separated from the cells within ______ of collection and refrigerated to prevent ________

Back 191

1 hour, loss of glucose due to cellular metabolism

Front 192

Fasting plasma glucose samples should be obtained when?

Back 192

In the morning after an 8 to 10 hour fast

Front 193

What preservative is added to the tube used to collect fasting plasma glucose samples? What color is the tube?

Back 193

Sodium fluoride, grey

FYI: lithium heparin tubes are not as preferable but may be used

Front 194

What reaction does hexokinase catalyze?

Back 194

phosphorylation of glucose to G-6-P

Front 195

How does EDTA interfere with the Hexokinase method of measuring glucose?

Back 195

EDTA binds MG2+. This interferes because ATP is stabilized by magnesium and ATP is necessary for the phosphorylation of glucose in the first reaction of the procedure.

Front 196

Is the Hexokinase enzyme specific for glucose?

Back 196

No.

This could potentially cause interference in the hexokinase method of glucose measurement as other carbohydrates could use up all of the ATP, limiting the phosphorylation of glucose.

Front 197

First rxn of hexokinase method of glucose measurement

D-glucose + ________ + hexokinase ⇀ glucose-6-phosphate + ADP

Back 197

ATP(Mg2+)

Front 198

First rxn of hexokinase method of glucose measurement

D-glucose + ATP(Mg2+) + ______ ⇀ glucose-6-phosphate + ADP

Back 198

Hexokinase

Front 199

Second rxn of hexokinase method of glucose measurement

G6P + NAD+ + G6PD ⇀ ______ + NADH + H+

Back 199

6-phosphogluconic acid

Front 200

Second rxn of hexokinase method of glucose measurement

G6P + NAD+ + _______ ⇀ 6-phosphogluconic acid + NADH + H+

Back 200

G-6-PD (glucose-6-phosphase dehydrogenase)

Front 201

Aldose

Back 201

A carbohydrate containing an aldehyde (carbonyl bound to a carbon and a hydrogen) group at the end of the carbon chain

Front 202

Ketose

Back 202

A carbohydrate containing a ketone, a carbonyl connecting two internal carbons.

Front 203

Simple sugars contain which functional groups?

What is the empirical formula for any carbohydrate?

Back 203

One aldehyde and two ore more hydroxyl groups.

Empirical formula = (CH2O)n where n=3 or more

Front 204

What is the most abundant and important carbohydrate in nature?

Back 204

D-glucose

Front 205

Reducing sugar

list examples (gold star for every one you get!)

Back 205

Carbohydrate with an aldehyde or ketone group; this allows the sugar to become oxidized/be a reducing agent

ex: glucose, galactose, fructose, lactose, maltose

Front 206

Oligosaccharides

Back 206

Carohydrate 2 to 10 monosaccharides long; joined by covalent bonds

Front 207

three most abundant disaccharides and their substituents

Which ones are capable of reducing?

Back 207

Maltose = glucose + glucose
Lactose = glucose + galactose
Sucrose = glucose + fructose

Maltose and lactose can reduce

Front 208

Where are monosaccharides absorbed after their breakdown?

Back 208

small intestine

Front 209

Describe the functions of pancreatic and salivary amylases

Back 209

Salivary amylase: cleaves starch polymers into dextrins

Front 210

Second rxn in Hexokinase method

G6P + ________ + G6PD ⇀ 6-phosphogluconic acid + ________ + H+

Back 210

NAD+, NADH

Front 211

At what wavelength is the absorbance measured in the hexokinase method? What does this measure?

Back 211

340 nm, to capture the conversion of NAD+ to NADH

Front 212

Glucose oxidase-peroxidase method rxn 1

________ + O2 + glucose oxidase → ________ + H2O2

Back 212

Beta-D-Glucose, gluconic acid

Front 213

GOD-POD method rxn 1

B-D-glucose + O2 + _______ → gluconic acid + ________

Back 213

glucose oxidase, H2O2

Front 214

GOD-POD method rxn 2

H2O2 + _________ + peroxidase → _________ + H2O

Back 214

reduced dye, oxidized dye (color change)

Front 215

Peroxidase performs what function in the second reaction of the GOD-POD method?

Back 215

The peroxidase catalyzes the oxidation of the dye utilizing oxygen obtained from the hydrogen peroxide molecule

Front 216

Explain how the GOD-POD method measures glucose levels.

Back 216

Beta-D-Glucose reduces H2O to hydrogen peroxide (glucose oxidase catalyst)

This hydrogen peroxide then oxidizes a color changing dye (peroxidase catalyst)

The colored dye is measured spectrophotometrically

Front 217

What are substances that can interfere with the GOD-POD glucose method? How do they interfere?

Back 217

Any strong reducing or oxidizing agent.

A reducing agent will use up the hydrogen peroxide in the second reaction, falsely decreasing the result

An oxidizing agent will oxidize the dye further resulting in a falsely increased result.

Front 218

Name examples of substances that will interfere with the GOD-POD glucose method

Back 218

Bleach (oxidizing agent - will falsely increase result)

Ascorbic acid (reducing agent - will falsely decrease result)

Front 219

Is the copper reduction test specific for glucose?

Back 219

No, it is positive for any reducing sugar

Front 220

How are monosaccharides other than glucose utilized by the body?

Back 220

Non-glucose monosaccharides are converted to glucose by hepatic enzymes

Front 221

Before glucose can be metabolized or stored, what reaction takes place?

Back 221

The hexokinase reaction wherein the hexokinase enzyme converts glucose into glucose-6-phosphate

Front 222

Preproinsulin

Back 222

Preproinsulin contains both the C peptide and the signal peptide; converted almost immediately to proinsulin after translation into protein in Beta-cels

Front 223

Proinsulin

Back 223

- formed from preproinsulin after cleavage of signal peptide
- Stored in Beta-cells of the pancreatic islets of Langerhans
- Stimulus to convert to insulin results in the cleavage of C-peptide

Front 224

Describe insulin formation from proinsulin

Back 224

Insulin is converted from proinsulin by the cleavage of the C-peptide, leaving only the A and B chain connected by disulfide bridges

Front 225

Insulin inhibits which pathways?

Back 225

Glycogenolysis (glycogen formation in liver)
Gluconeogenesis (glucose synthesis in liver)
Lipolysis in adipose tissue
Protein breakdown/amino acid release

Front 226

C-peptide levels are used clinically to...

Back 226

Determine how much insulin the patient is producing naturally

in contrast, therapeutic insulin will not cause a change in C-peptide levels

Front 227

Insulin stimulates which physiological processes in the:
liver?
adipose tissue?
muscle/other cells?

Back 227

Liver: glycogenesis and fatty acid synthesis
Adipose tissue: glycerol and fatty acid synthesis
Muscle/cells: inc. permeability to glucose, amino acid uptake, protein synthesis

Front 228

Hypoglycemia is seen at ____ glucose levels; symptoms set in at ____ glucose levels (panic value). Describe these symptoms

Back 228

Hypoglycemia: <70 mg/dL
Panic/symptoms: <50 mg/dL

Symptoms: Confusion, chills, rapid HB, weakness, nausea, trembling

Front 229

Which hormones have the opposite effect of insulin on blood glucose levels?

Back 229

Glucagon
Epinepherine
Growth hormone
Cortisol

Front 230

Which method of glucose measurement is the reference method?

Back 230

Hexokinase

the second reaction of this method is very specific for G6P

this method is not very susceptible to interference (only EDTA, some other carbohydrates in rxn 1)

Front 231

In the GOD-POD method, why must the sample be incubated?

Back 231

To allow all A-D-glucose to convert to B-D-glucose. This ensures that the 1st reaction will measure all glucose present.

Front 232

Other than measuring glucose levels, what else is the copper reduction test used for?

Back 232

Evaluation of infants for metabolic disorders. This test is sensitive to all reducing sugars so it may be used to detect sugar breakdown defects such as galactosemia.

Front 233

How does the copper reduction test for glucose work?

Back 233

Glucose (or any reducing sugar) reduces cupric ions to cuprous ions to produce a yellow or red cuprous compound

Front 234

What does the glucose oxidase enzyme catalyze in the first reaction of the GOD-POD method?

Back 234

B-D-glucose to gluconic acid and oxygen to hydrogen peroxide via redox reaction

Front 235

What does the peroxidase enzyme catalyze in the second reaction of the GOD-POD method?

Back 235

The oxidation of the dye by hydrogen peroxide via redox reaction

Front 236

How is the final product of the GOD-POD measured?

Back 236

The oxidized dye is measured by spectrophotometry

Front 237

How can a pO2 electrode be used as an alternative to the peroxidase reaction in the glucose oxidase method?

Back 237

O2 electrode measures the stoichiometric decrease in pO2 in the glucose oxidase reaction (oxygen is used up to oxidize glucose).

This indicates how much B-D-glucose is being converted to gluconic acid.

Therefore, colorimetric peroxidase reaction is unnecessary.

Front 238

4 different methods that can be used to measure glycosylated hemoglobin

Back 238

Ion-exchange chromatography method, affinity chromatography method, immunoassay, electrophoresis (including isoelectric focusing)

Front 239

What can interfere with the measurement of hemoglobin by ion exchange chromatography?

Back 239

Abnormal hemoglobins (have different charge)

increased hemoglobin A level (falsely increased result)

decreased RBC survival (falsely decreased result)

Front 240

The resin in ion exchange chromatography adsorbs glycosylated hemoglobins, while non-glycosylated hemoglobins elute (T/F)

Back 240

False, the resin in ion exchange chromatography is negatively charged, therefore glycosylated hemoglobins elute (they are less positively charged than nonglycosylated hemoglobins)

Front 241

What are some etiologies of hypoglycemia?

Back 241

Excessive insulin response
Insulinoma
Depleted glycogen storage
Rigorous exercise
Fasting
Liver disease

Front 242

Lab criteria for diagnosis of diabetes mellitus for: CPG, FPG, OGTT, HgbA1C

Back 242

First, any diagnosis must be done based on tests on at least two separate days.
CPG: ≥ 200 mg/dL + symptoms
FPG: ≥ 126 mg/dL
OGTT +2hr: ≥ 200 mg/dL
Hgb A1C: ≥ 6.5%

Front 243

Childhood onset, ketoacidosis and FPG that rarely exceeds 500 mg/dL are characteristics of...

Back 243

Type I diabetes mellitus

Front 244

DM Type 1 is an insulin _____ while DM Type 2 is an insulin ______

Back 244

Type 1: insulin deficiency
Type 2: Insulin resistance

Front 245

Very high FPG levels (>1000 mg/dL) are characteristic of

Back 245

DM Type 2

Front 246

Nonketonic-hyperosmolar coma is associated with...

Back 246

DM Type 2

Coma results from severe dehydration due to water following glucose into excreted urine