Biochemistry practice

Question 1

pH is:

Answer 1

The negative value of Log [H+].

Question 2

5 Buffers in body

Answer 2

(1) bicarbonate buffer (HCO3–/CO2),
(2) hemoglobin buffer (in erythrocytes),
(3) phosphate buffer,
(4) Acid protein buffer

Question 3

Normal values of bicarbonate, PH, PCO2, PO2

Answer 3

HCO3: 22-26
PH: 7.35-7.45
PCO2: 35-45
PO2: 80-100%

Question 4

4- Low ionic strength buffers give sharp bands and cause heat production so may denature protein

True or false?

Answer 4

false

Question 5

What are the most common supporting media in electrophoresis

Answer 5

Agarose gel and Polyacrylamide gel

Question 6

Enumerate five stains used in electrophoresis

Answer 6

1. Bromophenol blue for proteins .
2. Ninhydrin for amino acids .
3. Sudan black for lipoproteins .
4. Nitroblue tetrazolium for isoenzymes .
5. lodine for polysaccharides

Question 7

Factors affecting the velocity of migration of molecules

Answer 7

Electric field
Net charge of molecule
Friction coefficient
Buffers
Temperature

Question 8

Three vectors are

Answer 8

Plasmid: double stranded circular; for small DNA fragments (10kb)

Phage: virus, for large DNA fragments (20kb)

cosmid: synthetic vector: large DNA fragments (50kb)

Question 9

Requirements of PCR

Answer 9

a- Two oligonucleotide primers .
b- Thermus aquaticus DNA polymerase ( Taq polymerase ) .
c- All the four dNTP’s
d- DNA to be amplified.
e- Buffers.

Question 10

Application of PCR

Answer 10

1- It allows synthesis of DNA for sequencing or cloning .
2- Diagnosis study and of genetic disease e.g. sickle cell anemia .
3- Diagnosis of viral disease as HIV .
4- Synthesis of human proteins ( e.g. insulin ) , synthesis of vaccines ( e.g.
hepatitis B virus) and synthesis of antibodies ( e.g. monoclonal antibodies ) .
5- Gene therapy .
6- Forensic analysis .

Question 11

enumerate 5 supporting medium

Answer 11

Paper
Cellulose acetate
Agar
Agarose gel (common)
Polyacrylamide gel (common)

Question 12

PCR temp for: Denaturation, Primer annealing. elongation

Answer 12

95C, 50C, 72C

Question 13

The greatest buffering capacity at physiological pH would be provided by a protein
rich in which of the following amino acids?

Answer 13

Histidine

Question 14

A climber attempts an assault on a high mountain in the Andes and reaches an
altitude of 5000 meters (16,400 ft) above sea level. What will happen to his arterial
PCO2 and pH?

Answer 14

The pH will rise and PCO2 will fall

Question 15

DNA cloning is used for

Answer 15

Amplification of DNA in vivo

Question 16

Process of cloning

Answer 16

1. Plasmid is isolated then cut with a restriction enzyme forming cohesive ends .
2. The foreign DNA is cut by the same restriction enzyme .
3. The cohesive ends of the foreign DNA anneal with the ends of the plasmid DNA and joined by DNA ligase to form a recombinant plasmid DNA .
4. The recombinant plasmid DNA is introduced into bacteria by transformation .
5. The bacterial cells are allowed to divide and the recombinant plasmid DNA undergoes replication and amplification.

Question 17

Metabolic acidosis is compensated by the kidney, true or false?

Answer 17

false

Question 18

Separation of molecules in electrophoresis is according to their charges and
molecular weight. true or false?

Answer 18

True

Question 19

Importance of buffers in electrophoresis

Answer 19

transmit electric current, adjust the pH and facilitate
migration of the substance.

Question 20

enumerate 3 mechanisms for regulation of pH

Answer 20

Buffers - respiration - kidney

Question 21

2 Methods for composition of buffers

Answer 21

A weak acid and its salt with strong base - A weak base and its salt with strong acid

Question 22

Advantages of bicarbonate buffer system

Answer 22

• Present in higher concentrations than other buffers
• Easily formed at the tissues
• Easily corrected by respiration;

Question 23

1 physiological buffer linked to the kidneys & another 1 linked to the lungs

Answer 23

Phosphate - Bicarbonate buffer system

Question 24

The components of the electrophoresis unit.

Answer 24

• Electrodes: Cathode (-ve) and anode (+ve) made of platinum better than stainless
• Buffer reservoir
• Support of electrophoretic medium
• Transparent cover to prevent evaporation of the buffer

Question 25

Two main cuts in DNA by restriction enzymes

Answer 25

Staggered cut
Blunt ends

Question 26

Effect of ketosis

Answer 26

electrolyte imbalance

Question 27

Management of ketosis

Answer 27

1. IV glucose in starvation
2. IV glucose and insulin in DM
3. Bicarbonate to correct acidosis
4. K in case of hypokalemia
5. IV fluids in cases of dehydration