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The cell: unity of life

Cells are the smallest living units of an organism. All cells have three things in common no matter what type of cell they are. All cells have a cell membrane, which separates the inside the cell from its environment, cytoplasm, which is a jelly-like fluid and DNA which is the cell's genetic material. There are two broad categories of cells.

The first is eukaryotic cells. they have organelles which include the nucleus and other special parts. Eukaryotic cell are more advanced, complex cells such as those found in plants and animals. The second category is prokaryotic cells. They don't have a nucleus or membrane enclosed organelles. The do have genetic material but it's not contained within a nucleus. Prokaryotic cells are always one celled or unicellular organisms, such as baceria.

What are organelles? Organelles means: little organ. Organelles are the specialized parts of a cell that have unique jobs to perform.

The nucleus is the control centre of the cell. Contains DNA or genetic material. DNA dictates what the cell is going to do. Chromatin, spread out form of DNA found inside the nuclear membrane. When a cell is ready to divide DNA condenses into structures known as chromosomes. Nucleus also contains nucleolus, which is a structure where ribosomes are made. After ribosomes leave the nucleus synthesizing proteins. The ribosomes and the rest of organelles float around in cytoplasm.

Ribosomes are free in cytoplasm or attach the endoplasmic reticulum (ER). There are two types of ER: rough ER has ribosomes attached to it and smooth ER doesn't have ribosomes.

Proteins and other materials emerge from the ER in small vesicles where golgi apparatus receives and customized them.

Vacuoles are structures that store different materials like water in plants.

Lysosome are the garbage collectors of the cell, they are filled with enzymes.

The mitochondrion is an energetic organelle. Is an organelle that is the powerhouse for both animal and plant cells.

 

Activities:

a) Define the words that are in bold

b) Explains the difference between eukaryotic cells and prokaryotic cells.

c) Draw an animal and plant cell with its organelles and indicates its name.

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