1. Module 8 Intro

1.51. Lab

Lesson 9

Module 8—Circulation, Immunity, and Excretion

Lab: Urinalysis

 

You will now perform a modified urinalysis based on the investigation on page 320 of your textbook.

 

Problem

 

What physical and chemical tests can you use, and what data do they provide in the analysis of urine?

 

Procedure

 

Consider this scenario. A theft was committed in the washroom of a community building. Forensic specialists collected a urine sample at the scene of the crime. The police have four suspects in custody. Your task is to find out who committed the crime.

 

Open the Lesson 9 Assignment file, where there is a table to document the results of the tests and support the elimination of suspects. For each test, indicate the results for each individual in the chart. Once you have recorded the results for all of the tests, you should be able to identify the criminal.

 

You will start by interpreting the results of each test.

 

This is a photo of a gloved hand holding a sample of urine.

© Christina Richards/iStockphoto

Test 1—Colour, Odour, Clarity: Normal urine is a clear, straw-coloured liquid. Urine may be cloudy because it contains red or white blood cells, bacteria, or pus from a bladder or kidney infection. Normal urine has a slight odour. Foul-smelling urine is a common symptom of a urinary tract infection. A fruity odour is associated with diabetes mellitus. Use the following descriptions of the urine samples to fill in your chart located in your Lesson 9 Assignment.

 

Control: Urine is yellow. Smell is normal. Looks cloudy.

 

Crime suspect: Urine is yellow. Smell is fruity. Looks clear.


 

Suspect 1: Urine is yellow. Smell is fruity. Looks clear.

 

Suspect 2: Urine is yellow. Smell is normal. Looks clear.

 

Suspect 3: Urine is yellow. Smell is normal. Looks cloudy.

 

Suspect 4: Urine is yellow. Smell is fruity. Looks clear.

 

This is a photo of a test tube of urine in a water bath.

© mypokcik/shutterstock

Test 2—Protein: One sign of kidney damage is the presence of protein in urine. To test for protein, a portion of each sample is placed in a hot water bath. If the sample becomes cloudy or is cloudier than the original sample, it contains protein.

  1. After a few minutes, the test tube from the hot water bath is removed and compared to the original sample.
  1. If the heated sample is cloudier, it contains protein. The test is positive.

Use the following descriptions of the urine samples to fill in your chart located in your Lesson 9 Assignment.

 

Control: positive

 

Crime Suspect: negative

 

Suspect 1: negative

 

Suspect 2: negative

 

Suspect 3: positive

 

Suspect 4: negative


 

pH1 is a deep purple; pH2 is red/orange; pH 3 is orange; pH4 is a light orange; pH5 is yellow; pH6 is a yellow green; pH7 is green; pH 8 is dark green; pH 9 is dark green/blue; pH10 is blue; pH11 and above is dark blue.

Test 3—pH: The wide range of pH values (pH 4.7 to 8.5) makes this the least useful parameter for a diagnosis of kidney disorders. Kidney stones are less likely to form and some antibiotics are more effective in alkaline urine. There may be times when acidic urine may help prevent some kinds of kidney stones. Bacterial infections also increase alkalinity, producing a urine pH in the higher 7–8 range.

 

A clean medicine dropper is used to place a drop of each sample of urine on small pieces of universal indicator (pH) paper. They are left for about 30 seconds. The pH paper can turn several different shades, depending on pH. pH can be determined by comparing the indicator to a colour chart.

 

Use the following descriptions of the urine samples to fill in the chart located in your Lesson 9 Assignment. To determine pH, use this indicator colour chart.

 

Control: yellow green

 

Crime Suspect: yellow/green

 

Suspect 1: orange

 

Suspect 2: green/blue

 

Suspect 3: green

 

Suspect 4: yellow/green

 

This photo is of a bottle of glucose test strips. The label shows a colour gradient from light blue to dark brown. Intermediate colours are greens and browns. Blue indicates no sugar, while dark brown indicates high glucose levels. Intermediate colours indicate the presence of glucose in varying concentrations.

© Norman Chan/shutterstock

Test 4—Glucose: One sign that a person has diabetes mellitus is the presence of glucose in the urine.

  1. To test for glucose, a glucose test strip is dipped into each sample of unheated urine and immediately taken out.
  1. The strip is compared to a colour chart. The chart shows a colour gradient from light blue to dark brown. Intermediate colours are greens and browns. Blue indicates no sugar, while dark brown indicates high glucose levels. Intermediate colours indicate the presence of glucose in varying concentrations.

Use the following descriptions of the urine samples to fill in your chart located in your Lesson 9 Assignment.

 

Control: dark brown

 

Crime Suspect: dark brown

 

Suspect 1: light blue

 

Suspect 2: green

 

Suspect 3: light blue

 

Suspect 4: dark brown

 

From the results of the urine analysis, you should be able to tell which suspect committed the crime, or at the very least left his or her urine at the crime scene.

 

Complete the Analysis questions in the Lesson 9 Assignment.