. Cell membrane

• All cells have a membrane surrounding the cell. It is called the cell surface membrane. This membrane forms the outer boundary of the cell. It is here that all exchange takes place between the cell and its surrounding environment.
• Cell membranes allow some substances to pass in and out of the cell, but prevent the passage of others. Hence cell membranes are said to be differentially or selectively permeable.
• In a plant cell, it is very difficult to see the cell membrane, because it is right against the cell wall I. e. The cell membrane is covered by the cell wall. In an animal cell, the cell membrane forms the outermost cell boundary.
• The cell membrane protects the cytoplasm and the nucleus.

2. Cytoplasm

• The term cytoplasm refers to all the living substance of a cell, except the nucleus. The cytoplasm is a clear jelly. It is nearly all water; about 70% water in many cells.

• It contains many substances dissolved in it, especially proteins.

• Cytoplasm contains a number of sub-units of which there are two types: inclusions and organelles.

Inclusions consist of a variety of materials, as starch grains, fat globules and crystals of excretory substances which are stored temporarily in the cell.

Organelles are bounded by membranes, are more permanent structures and are active in the life of the cell e.g. Mitochondria, chloroplast etc.

3. The nucleus

• The nucleus is the cell’s control centre I. e. It controls all the activities of the cell. First and foremost it controls the formation and development of a cell.
• At least one nucleus is found in the cells of all animals, plants and protoctists.

The only human cell that does not have a nucleus is an old red blood cell

This explains why red blood cells have a short life span.

• The nucleus is enclosed by a nuclear envelope or nuclear membrane, which is perforated by nuclear pores. These pores control the exchange of materials between the nucleus and the cytoplasm.

• The nucleus also controls the chemicals which the cell manufactures.

4. Vacuoles

• In a plant cell, the vacuole is a space in the cytoplasm of the cell, filled with sap (hence the name sap vacuole), a watery fluid of various substance including sugars, mineral salts, pigments etc.

• A thin membrane called tonoplast surrounds the vacuole of a plant cell.

• On the other hand, small, numerous, temporal vacuoles, or vesicles, are often found in animal cells.

5. Cell wall

• It is present only in plant cells.
• It is made up of a tough material called cellulose.
• The cell wall gives the cell a fixed shape and gives the plant some rigidity.
• In plant cells, the cell wall forms the outer most boundary of the cell while in animal cells the cell membrane forms the outermost boundary of the cell (animal cells lack a cell wall I. e. they are naked)

• The presence of a cell wall makes plant cells clearly visible as distinct units when viewed under a microscope. It is rather like a box around the plant cell giving many plant cells this rectangular shape.

• Animal cells have a less distinct outline when seen under a microscope.

6. Chloroplasts

• They are green in colour and are located throughout the cytoplasm.
• They contain the green pigment chlorophyll which absorbs sunlight for as a source of energy during photosynthesis.
• Animal cells never contain chloroplast and chlorophyll·
• Photosynthesis takes place in the chloroplast.

1. Functions of cells plant

• palisade cells make carbohydrates by photosynthesis
• root hair cell absorb water and minerals from the soil
• guard cells open and close the stomata of the leaves

2. Functions of cells animal

• Cheek cell line the inside of the mouth
• Red blood cells carry oxygen to and fro to the heart
• White blood cells fight diseases by destroying pathogens/ germs
• Ovum/egg cell develop into a baby when fertilized
• Sperm cell fertilize ovum
• Neurone/nerve cells carry impulses around the body