6. Blood Glucose

Question 1

name one metabolite apart from glucose that is likely to increase in the blood of diabetic patients

Answer 1

plasma Ketone bodies, e.g. acetoacetate

Question 2

why do diabetic patients have more ketone bodies

Answer 2

Plasma ketone body levels are high in patients with untreated diabetes because fats are used as fuel instead of glucose [due to insulin issues] (fatty acids are degraded to acetyl CoA in mitochondria), leading to accumulation of acetyl CoA

Question 3

Diagnosis of diabetes requires a glucose tolerance test: what is the aim of this test

Answer 3

to find out how effectively the patient can remove glucose absorbed into the bloodstream.

Question 4

how do we carry out a glucose tolerance test

Answer 4

An oral dose of glucose (50 g) is given to patients who have fasted for 12 h, followed by the collection of blood samples at intervals for 2 h.

• Glucose concentration in these samples is measured and a glucose tolerance curve is constructed.

Question 5

what does a glucose tolerance curve look like for a normal person

Answer 5

starts low, peaks, and comes back down, pretty thin like /\

Question 6

what does a glucose tolerance curve look like for a mild diabetic

Answer 6

starts quite a bit higher than the normal persons, and goes back down to where is started only, both at a moderate/high glucose conc
- peak of graph line can even hit the renal threshold

Question 7

what does a glucose tolerance curve look like for a severe diabetic

Answer 7

same curve / semicircle shape but very high glucose concentration: all above the renal threshold

Question 8

what is renal threshold

Answer 8

the glucose concentration above which glucose appears in urine. High blood glucose levels for extended periods indicate that a patient is diabetic because they cannot absorb glucose from the blood.

Question 9

Phenol reagent used:

Answer 9

21.25 mM phenol and 154 mM sodium chloride.

Question 10

Enzyme reagent used:

Answer 10

100 mM sodium acetate/acetic acid pH 6.0, 1.48 mM 4- aminophenazone, 2 units/mL glucose oxidase, and 1 unit/mL peroxidase.

Question 11

Individuals with untreated diabetes produce large quantities of ketone bodies: what can this lead to

Answer 11

ketoacidosis

Question 12

why is ketoacidosis bad

Answer 12

The primary reason ketones are dangerous in ketoacidosis is that they cause the blood to become too acidic (acidosis). This can disrupt the body’s normal chemical balance and damage organs.
- causes excessive thirst, nausea, vomiting, pain in abdomen etc

Question 13

what is the major plasma ketone body in mammals

Answer 13

acetoacetate

Question 14

what reduces acetoacetate

Answer 14

β-hydroxybutyrate dehydrogenase

Question 15

what is acetoacetate reduced to?

Answer 15

β-hydroxybutyrate

Question 16

what is used as a cofactor to reduce acetoacetate to β-hydroxybutyrate

Answer 16

NADH

Question 17

Acetoacetate + NADH —(on top of the arrow= β-hydroxybutyrate dehydrogenase) —>

Answer 17

β-hydroxybutyrate + NAD

Question 18

a decrease in A340 corresponds to presence of acetoacetate in the sample: how come? what absorbs at 340nm

Answer 18

NADH absorbs at 340 nm, NAD doesn’t.

Question 19

Beer Lambert law

Answer 19

𝐴=ε𝑐𝑙

Question 20

𝐴=ε𝑐𝑙: what does each thing stand for

Answer 20

A = absorbance at 340 nm
ε = NADH molar extinction coefficient = 6300 M-1 cm-1
c = concentration of NADH in M
l = path length = 1 cm

Question 21

the control shows has no enzyme so shows what

Answer 21

natural decay of NADH over the course of the assay.

Question 22

calculation of change in absorbance for samples of interest - shows decrease in NADH due to conversion of acetoacetate. how do we work it out

Answer 22

(initial absorbance - final absorbance) - change in initial and final absorbance for the control

Question 23

NADH concentration allows us to determine acetoacetate concentration: why?

Answer 23

(because 1 mole of NADH is consumed per mole of acetoacetate).

Question 24

Beer-Lambert law used to convert what 2 things

Answer 24

NADH A340 to NADH concentration.

Question 25

units for y axis on a calibration curve (e.g. if its absorbance at 510)

Answer 25

nm A510 nm

Question 26

The hydrogen peroxide formed is detected using a second enzyme peroxidase forming the products water and oxygen. This oxygen is measured by its reaction with 4-aminophenazone and phenol to give what colour

Answer 26

pink

Question 27

how can we work out glucose concentration using a calibration curve of (conc vs absorbance) USING y = mx +c (more accurate)

Answer 27

Sure, here's the simplified version: Y = mX + c Where: Y = Absorbance (A₅₁₀) m = Slope (change in absorbance per unit change in concentration) X = Glucose concentration (mM) c = Y-intercept (absorbance value when glucose concentration is zero) To find unknown glucose concentration: Rearrange to: X = (Y - c)/m Where X is the glucose concentration you're solving for

Question 28

What is the Glycosuric Period?

Answer 28

The glycosuric period is the time during which glucose is present in the urine. It occurs when the blood glucose concentration is above the renal threshold.

Question 29

Severe diabetic: what is the renal threshold and the glycosuric period like on a graph

Answer 29

Prolonged time above the renal threshold → long glycosuric period. Blood glucose remains elevated for hours, showing poor insulin response or resistance.

Question 30

why is having fatty acids in the urine bad

Answer 30

shows ketoacidosis (When the body doesn't have enough insulin to process glucose (sugar) for energy, it starts breaking down fat instead. This fat breakdown produces ketones)

Question 31

type 1 vs type 2 diabetes mellitus

Answer 31

type 1 (juvenile) diabetes – a lifelong condition where the body's immune system attacks and destroys the cells that produce insulin. type 2 (fatty) diabetes – where the body does not produce enough insulin, or the body's cells do not react to insulin properly.

Question 32

ΔA = E c l: what each thing stands for

Answer 32

E = the molar extinction (absorbance) coefficient = 6.3x103 L/mol/cm for NADH c = concentration (mol/L) l = cuvette path length = 1 cm ΔA for acetoacetate

Question 33

how do we work out ΔA for acetoacetate

Answer 33

To calculate the change in A340 that is due to acetoacetate in each sample, subtract the control value from the test (i.e. ΔA test - ΔA con = ΔA for acetoacetate in sample).

Question 34

u understand how to do the beer Lambert law calc but make sure u memorise the method e.g formula or what're

Answer 34

look t ur lab report