Page 18 - ตัวอย่าง Science Solution 1

5. Nuclei

Nuclei are structures situated in the middle of cells. Most cells have nuclei, except some types of cells,
such as red blood cells in mammals and phloems in plants.

A nucleus is an essential component
in controlling functions of cells along
Nuclear Membrane with cytoplasm in genetic transmission.
Besides, nucleus also controls compound
substances of cells.
Chromatin

Nucleolus
A nucleus also consists of a nuclear
membrane, which is very thin membrane
similar to cell membrane that surrounds
essential substances. Inside, nucleus
is connected to endoplasmic reticulum.
Nuclear membrane consists of small holes
all around it to let substances in and
out between liquids within the nucleus
(nucleoplasm) and outside the nucleus of

Figure 1.29 Nucleus the cell (cytoplasm) through diffusion.

All substances in nuclei are called nucleoplasm, which consist of the following essential parts:
1. Nucleolus – a nucleoprotein which is seen as an opaque or a darken-coloured substance in a nucleus.
It is the organelle that synthesize ribosomes.
2. Chromatin networks – linear structures which are woven together to form nets. They consist of DNA or
genes. When a cell divides, chromatin networks turn into chromosomes and control characteristic
expressions in organisms.
3. Nuclear membrane – a bilayer tissue with the outer layer being rough since it is adhered with ribosomes
and contains a connected path to endoplasmic reticulum, Golgi bodies and mitochondria. It functions as
the controller of substance exchanges and a passage way of substances between nucleus and cytoplasm.

Which components allow small molecular substances to pass-through but not the larger ones?
Which components are semipermeable membranes?
Which components of plant cells are shrimps or crab shells compared to?
Which components are especially more required in cells that need abundant energy the most?
Which components are found in plant cells but are not found in animal cells?

Unit 1 Units of Organisms and Plants Life 25