Page 16 - ตัวอย่าง Science Solution 1

Plant and animal cells have some similar parts, such as cell membranes, cytoplasm and
nuclei. There are also some different components as well. Other differences in shapes and functions, such as
photosynthesis, will be presented in details later on.

1.3.1 Essential Components and Functions of Cells

Though organism cells are very small, there are many structures that are components inside, which
will be presented later on. For this class, students should learn about some essential components that can be
seen from electron microscopes as the following:

1. Cell Wall
A cell wall is an outermost layer of a plant cell in general, which consists mainly of cellulose. A cell
wall wraps around a plant cell to protect the cell from danger, preserve the shape and strengthens the cell.
Animal cells do not have cell walls, but some animals might have protective coatings for their cells which
are different, depending on cell types of the animals, e.g. shrimp and crab shells that are coated with
glycoprotein, and cells of diatoms that are coated with silicas. These coatings preserve the shapes of cells.

2. Cell Membrane

A cell membrane is a very thin layer that consists of proteins and lipids. A cell membrane controls
quantities and types of substances in and out of cells. It has a small hole that allows and prevents some certain
substances in and out of the cell. This type of membrane is called a semipermeable membrane.

Carbohydrate Chains
Proteins

Lipid
Bilayers

Protein channel

Figure 1.26 Cell Membrane
Important Question

Do animal cells have cell walls and why?

Unit 1 Units of Organisms and Plants Life 23