23. cells that need to make a lot of protein are expected to have a large number of

24. a cell’s relatively constant internal physical and chemical conditions are called

25. the electrons that chlorophyll loses to the electron transport chain are replenished by molecules.

26. a cell that has 5 chromosomes in the g1 phase will have chromatids in the g2 phase.

27. adult skin cells can no longer become other types of cells because they have already under

23. The right answer is Ribosomes.

A ribosome is a cytoplasmic organelle, synthesized by the nucleolus, consisting of proteins and ribonucleic acids and at the level of which protein synthesis is carried out, starting from the amino acids of the cytoplasm, according to the information provided by a messenger RNA. This cytoplasmic organelle allows translation (deciphering mRNA and protein synthesis).

24. The right answer is Homeostasis

Homeostasis is a process by which a key factor (eg, temperature, acidity, blood pressure, blood sugar, ..) is maintained around a saturation value beneficial to a system under consideration, through a regulation system.

For example, glucose, a hexose (monosaccharide sugar composed of 6 carbon atoms) is the only energy substrate used by erythrocytes (red blood cells) and cells of the nervous system under physiological conditions. In addition, glucose is a very important energy source for muscle cells at work and is also needed for storage of free fatty acids in adipocytes. All these processes are regulated by hormones such as insulin, glucagon, adrenaline, cortisol ...

25. The right answer is Water

Photophosphorylation involves both photosystems (I and II) with the reaction centers (P700 and P680). The light energy causes the excitation and the departure of an electron from a chlorophyll molecule of photosystem II. To compensate for this loss, the latter recovers an electron from the photolysis of the water molecule:

H2O ---> 2 H + + 1/2 O2 + 2e-

26. The right answer is Ten (10)

In phase G2 (the one following phase S, consisting in replicating the DNA in two copies), we will recover the genetic capital of the doubled cell, with a view to its preparation for division (mitosis or meiosis). So if the G1 phase cell has 5 chromosomes (each chromosome is represented by a chromatid), it will have 10 chromatids in the G2 phase (always 5 chromosomes but each chromosome is represented by 2 sister chromatids).

27. The right answer is Differentiation

Cell differentiation consists of a cell-specific acquisition of cell type specific characters, such as cytodifferentiation. A cell is differentiated.

It is thus a process by which the cells take on particular morphological and physiological characters, different according to the tissues. Cell differentiation is a little less marked in plants than in animals, where the specialization of organs is more extensive.

This process is irreversible, that is to say that one can not obtain a stem cell (multipotent) from a cell already differentiated such as the cells of the skin.

the correct choice is i and iv.