Grade 9: Biology
Lesson # 1 All about cells
Introduction to cells
WHAT ARE CELLS?
○ Cells are the basic structural and functional units of all living organisms.
○ Every living thing is made up of one or more cells.
Types of Cells:
1. Prokaryotic Cells:
○ Simpler, smaller cells without a true nucleus.
○ Found in unicellular organisms like bacteria.
○ DNA floats freely in the cytoplasm.
○ Examples: Escherichia coli (E. coli), Salmonella.
2. Eukaryotic Cells:
○ Larger, more complex cells with a nucleus.
○ Found in plants, animals, fungi, and protists.
○ Contain many organelles with specialized functions.
○ Examples: Skin cells, nerve cells, leaf cells.
Key Differences Between Prokaryotic and Eukaryotic Cells:
● Prokaryotes: No nucleus, no membrane-bound organelles, usually smaller.
● Eukaryotes: Have a nucleus, membrane-bound organelles, and are larger.