أهم 100 سؤال فى مراجعة مادة أحياء لغات الجزء الثانى الصف الثالث ثانوي

من طرف **حنين الصمت** الخميس 18 أبريل 2013, 8:04 pm

الدرس في شكل نص مقروء

أهم 100 سؤال فى مادة أحياء لغات - الجزء الثانى

C) Give reasons for each of the following:

1 - The starch grains are small size inside the chloroplast.

To facilitate the conversion of starch into soluble sugar to move outside the chloroplast.

2- There are many convolutions in the lining of the large intestine.

To facilitate the absorption of water & salts through convolutions of the inner wall.

3- Gastric juice doesn’t affect the epithelial cells of stomach.

The stomach is lined internally with a thick layer of mucus from special cells.

Pepsinogen does not become active unless it reaches the stomach cavity

HCl is secreted at the tip of the cell &poured directly towards the stomach cavity .

4- The companion cell has large no. of ribosomes and mitochondria.

In order to control vital functions of sieve tube and producing energy.

5- The capillary theory is a weak force for the ascent of sap.

Because the finest capillary tube of xylem vessels (from 0.5 to 0.02 m.m) doesn’t allow water to rise more than 150 cm.

What would happen in each of the following cases?:

1- Introducing a piece of bread inside the mouth and chewing it continuously for 3 minutes.

The starch change into maltose sugar by the effect of ptyalin enzyme.

2- Removal of the ileum experimentally from the body of a mammalian animal.

The animal will die because in the ileum the digestion of food is completed and the

absorption of food takes place.

3- The Casperian strip is absent from cells of endodermis in the plant root.

The water pass to the phloem by imbibition which is not controlled by the cell.

4-The passage of ionic salts from the soil to the root cells against the concentration gradient

The cells need more amount of energy produced from the aerobic respiration (sugar +O2)

5- Absence of valves from veins.

the blood will flow back to the body organs and causing disturbance in the blood circulation and may causing blood cloting.

What is meant by each of the following:

Plasmid - Polyribosome - Release factor - Human genome.

Ans:

Plasmid is one or more small circular DNA molecules in some prokaryotic cells.

Polyribosome is mRNA molecule which has several to over 100
ribosomes attached to it and transcribing its codons as they move
along.

Release factor The releasing factor is a special protein, binds
to the stop codon on the mRNA & causes the mRNA to leave the
ribosome and the ribosomal subunits separate.

Human genome is all genes and DNA molecules in the body cell.