Mod.A. Bio Lec5

Question 1

The only sugar utilized by the body is

Answer 1

glucose

Question 2

Fructose and galactose are converted to ?

in ?

Answer 2

glucose IN THE LIVER

Question 3

fructokinase compared to hexokinase (km, product, goal)

Answer 3

Fructokinase:
low km
fructose-1p
trapping of fructose

Hexokinase:
high km
fructose-6p
trapping of fructose

Fructose is not principally metabolized by hexokinase , but essentially all of the fructose is converted to fructose-1-phosphate in the human liver

Question 4

Fructose intolerance (cause, result)

Answer 4

deficiency of fructose 1-p aldolase B

accumulation in fructose 1-phosphate and a depletion of ATP and Pi.

Causes Liver damage & jaundice due to fructose-1-phosphate in tissue—that can progress in cirrhosis & ascites , renal tubular damage , hypoglycaemia due to inhibition of glycogenolysis

Question 5

Fructosuria (cause, result)

Answer 5

deficiency in fructokinase.

fructose appears in blood and urine

Question 6

Steps of galactose metabolism:

Answer 6

1-galactose is converted to galactose 1-p by galactokinase

2-galactose 1-p is converted to UDP galactose by galactose 1-p uridyl transferase

Question 7

Galactosemia (meaning, cause, result)

Answer 7

Inability to metabolize galactose to glucose

Deficiency of galactokinase or uridyl transferase

1.Reduction of galactose → يتكون
↑↑ galactitol → الذي يسبب
- cataract formation - acts on CNS (mental retardation).

2.Accumulation of Galact-1-P →→ Liver damage Anew born infant presents with poor feeding, vomiting, jaundice and enlarged liver. Urine analysis is positive for reducing substances

Question 8

Lactose Intolerance is due to

Answer 8

deficiency of LACTASE enzyme

Question 9

Lactose intolerance diagnosis is by

Answer 9

1- Dietary history of the patient 2- Family history

3- Stool acidity test, hydrogen breath tests.

Question 10

Lactose Intolerance symptoms :

Answer 10

1- bloating
2- foul smelling flatus
3- loose stools

Question 11

HMP shunt/ PPP (definition, site, goal, H acceptor)

Answer 11

• • التعريفات :- It is other pathway for glucose oxidation without direct generation of ATP.
• The minor pathways for oxidation which are not for energy production

** المكان : Active in 1- liver, mammary glands, adrenal glands, adipose tissue, RBCs
2- rapidly dividing cells (bone marrow, skin, and intestinal mucosa)
- داخل الخلية The enzymes are found in the cytosol.

هدفها : Is a process that generates NADPH and
pentoses (5-carbon sugars).

** H- acceptor : NADP, not NAD is used.

Question 12

key regulatory enzymes are:

Answer 12

1- G-6-P dehydrogenase (G6PDH)

2- 6-Phosphogluconate dehydrogenase (6-PG DH).

Question 13

rate limiting enzyme is:

Answer 13

G6PDH

Question 14

ribose-5-phosphate (R5P), is used in the synthesis of

Answer 14

nucleotides and nucleic acid

Question 15

erythrose-4-phosphate (E4P), is used in the synthesis of

Answer 15

aromatic amino acids.

Question 16

Regulation of HMS pathway :

Answer 16

1-Insulin:induces the synthesis of G-6-PDH and 6-PGDH.

2-NADPH: is an allosteric -ve for the previous 2 enzymes.

Question 17

NADPH is used in:

Answer 17

1- for biosynthesis
( Reductive biosynthetic reactions ) :
FA , synthesis of cholesterol and steroid hormones and isoprenoids.

2- NADPH protects the tissues and cells from oxidative damage
* ما سببها by hydrogen peroxide (H2O2) and superoxide free radicals
* كيف يقوم NADPH بهذا الدور ??? →→by providing reduced glutathione (GSH) for removal H2O2 especially in RBC
( Erythrocytes ) and the cells of the lens and cornea

Question 18

Favism (cause, result, symptoms, onset of symptoms)

Answer 18

Glucose 6-phosphate dehydrogenase (G6PD) deficiency

oxidative damage by hydrogen peroxide (H2O2) and superoxide free radicals,

Erythrocyte hemolysis →releasing free hemoglobin into the blood. Jaundice and sometimes dark urine

Erythrocytes begin to lyse 24 to 48 hours after after
 1- ingestion of the beans ,
2- certain legumes
3- various drugs (e.g.
ingestion of the antimalarial drug primaquine or of sulfa antibiotics
(Sulphonamides )
4- exposure to certain herbicides.
التعرض لبعض مبيدات الأعشاب .