Assignment No 1

Assignment No 1

Biochemistry Course HIT 214

2^nd semester 2020 Dr. Ayat B. Al-Ghafari

Instructions تاميلعتلا

ةبسن سايقل ةيلمعملا براجتلاب ةصاخلا ةيلاتلا ةلئسلأا ىلع ةباجلإا لمآ 

.مدلا يف تايركسلا :يلاتلا ةاعارم عم 

.اهل ةليمز عم ةكراشملاب سيلو ةلئسلأا نع ةباجلإاب اهدرفمب موقت ةبلاط لك .1

بجاولا ميلستل دعوم رخأ .2

قفاوملا ءاعبرلأا موي 25

سرام 2020

م

ةعاسلا فصن مصخ متيس خيراتلاو تقولا اذه دعب ،Jءاسم 9:00

.ميلستلا يف ريخأت ةعاس لك ىلع ةجرد .ةيزيلجنلاا ةغللاب نوكت نأ دبلا ةباجلاا .3

ةغيص يف بجاولا فلم لاسرا متي نأ .4

Word يليميا ىلع

abalghafari@kau.edu.sa ( تاجردلاو ةلئسلأا .5

10 ةحيرشلا يف يلاتلاك ةمسقم نوكتس )تاجرد

.ةلبقملا قفاوملا سيمخلا موي لاؤس لكل ةحيحصلا تاباجلإا ضرع متيس .6

26 سرام

2020 للاخ ةلبقملا تابجاولاب مكملاعإ متيسو يصخشلا يعقوم ىلع م

ةمدخ MyKau

.

عيزوتو اهيلع ةباجلإا بولطملا ةلئسلأا تاجردلا

1. What is Fehling test (2 marks)?

2. Does it used for the detection of reducing or non- reducing sugars (0.5 mark)?

3. What is the final product color (0.5 mark)?

4. Write the general equation for this reaction (2 marks)?

5. Which compound does not give Fehling test (1 mark)?

6. What is the difference between Fehling A and Fehling B (2 marks)?

7. Does sucrose give positive result with Fehling test and why (2 mark)?

Answers

1- What is Fehling test (2 marks)?

 Fehling's test is a chemical reagent used to differentiate between water

soluble carbohydrate and ketone functional groups, and as a test for reducing

sugars and non-reducing sugars,

supplementary to the Tollens' reagent test.

Answers

2- Does it used for the detection of reducing or non-reducing sugars (0.5 mark)?

 Reducing sugars only

Answers

3- What is the final

product color (0.5 mark)?

 Red copper)I( oxide then precipitates out of the reaction mixture, which indicates a positive result i.e. that redox has taken place )this is the same positive result as

with Benedict's solution(.

Final positive product

The net reaction between an aldehyde and the copper(II) ions in Fehling's solution may be written as:

RCHO + 2 Cu²⁺ + 5 OH⁻ → RCOO⁻ + Cu₂O + 3 H₂O

or with the tartrate included:

RCHO + 2 Cu(C₄H₄O₆)₂²⁻ + 5 OH⁻ → RCOO⁻ + Cu₂O + 4 C₄H₄O₆²⁻ + 3 H₂O

4- Write the general equation for this reaction (2 marks)?

Answers

Answers

5- Which compound does not give Fehling test (1 mark)?

 Aldehydes are oxidized, giving a positive result, but ketones do not react, unless they are alpha-hydroxy-ketones.

 A negative result is the absence of the red precipitate; it is important to note

that Fehling's will not work with

aromaticaldehydes; in this case Tollens' reagent should be used.

Answers

6- What is the difference between Fehling A and Fehling B (2 marks)?

 Fehling's A is aqueous solution of copper)II(

sulfate, which is deep blue (1 mark). 

 Fehling's B is a colorless solution of

aqueous potassium sodium tartrate )also known as Rochelle salt( made in a strong alkali, commonly with sodium hydroxide.

Typically, the L-tartrate salt is used (1 mark).

Answers

7- Does sucrose give positive result with Fehling test and why (2 mark)?

 Since in Sucrose, as reducing groups of glucose and fructose are involved in

glycosidic bond formation, sucrose is a non- reducing sugar )1 mark( and hence don’t give positive Fehling test )1 mark(.

GOOD LUCK