Benedict's Test

Question 1

Used to check for the presence of reducing sugars in a given analyte

Answer 1

Benedict’s test

Question 2

Benedict’s reagent is a complex mixture of

Answer 2

1. Sodium citrate
2. Sodium carbonate
3. Pentahydrate of copper (II) sulfate

Question 3

Indicates a positive Benedict’s test

Answer 3

Brick-red precipitate

Question 4

Test principle

Answer 4

Reducing sugar (subjected to heat) —-> converted to Enediol (a strong reducing agent) in the presence of an alkali (sodium carbonate)

Enediols –> reduce cupric ions (Cu2+) —-> cuprous ions (Cu+)

Cu+ (present in the form of insoluble copper (I) oxide) —-> oxidized to a Brick-red compound

⬆️ reducing sugars —> color gradually changes from green to yellowish to orange to brick-red

Question 5

False positives due to reaction with drugs like

Answer 5

1. Penicillin
2. Isoniazid
3. Streptomycin
4. Salicylates
5. P-aminosalicylic acid

Question 6

Chemicals in urine that delays the Benedict’s reaction

Answer 6

1. Creatinine
2. Ascorbic acid
3. Urate

Question 7

Result interpretation of Benedict’s Test

Blue

Answer 7

0
No reducing sugar

Question 8

Result interpretation of Benedict’s Test

Green

Answer 8

<0.5
Trace reducing sugar

Question 9

Result interpretation of Benedict’s Test

Green ppt

Answer 9

0.5-1
Trace reducing sugar

Question 10

Result interpretation of Benedict’s Test

Yellow ppt

Answer 10

1-1.5
Low reducing sugar

Question 11

Result interpretation of Benedict’s Test

Orange-red ppt

Answer 11

1.5-2
Moderate reducing sugar

Question 12

Result interpretation of Benedict’s Test

Brick-red ppt

Answer 12

> 2
High reducing sugar

Question 13

Benedict’s reagent: health hazard NTP

Answer 13

grade 2

Question 14

acts as chelating agent to form complex with Cupric ions (Cu2+) to prevent deterioration

Answer 14

Sodium Citrate

Question 15

Source of cupric ions

Answer 15

Copper sulfate

Question 16

REDUCING SUGARS:

Answer 16

• Glucose
• Fructose
• Glyceraldehyde
• Lactose
• Arabinose
• Maltose

Question 17

MONOSACCHARIDES:

Answer 17

• Glucose (aldose)
• Fructose
• Galactose

Question 18

DISACCHARIDES:

Answer 18

-Sucrose: Glu + Fru
-Lactose: Glu + Gal
-Maltose: Glu + Glu

Question 19

POLYSACCHARIDES:

Answer 19

• Starch
• Cellulose
• Glycogen

Question 20

Glucose Renal Threshold:

Answer 20

160-180mg/dl

Question 21

Normal Urine Glucose

Answer 21

15mg/dl

Question 22

Fasting Urine Glucose:

Answer 22

2-20mg/dl per 100ml

Question 23

drops for Benedict’s sol’n

Answer 23

2ml/40 drops

Question 24

Heat at

Answer 24

2-3mins

Question 25

What reagent provides heat for Benedict’s tablet test/clinitest?

Answer 25

SODIUM HYDROXIDE

Question 26

Urine and Reagent ratio

Answer 26

1 ml of urine and 2ml of reagent