All living things are made up of cells, which are the basic units of structure and function. Robert Hooke discovered cells in 1665 using a microscope. The cell theory states that cells are the fundamental unit of life, new cells arise from existing cells, and all organisms are composed of one or more cells. Cells vary in size, shape, and function depending on their role. The main components of cells are the plasma membrane, nucleus, and cytoplasm. The plasma membrane regulates what enters and exits the cell and maintains its shape.

1. CHAPTER 1
FUNDAMENTAL UNIT OF LIFE

2. TOPICS
•DISCOVERY OF CELL
•MICROSCOPE
•CELL THEORY
•WHAT ARE LIVING THINGS MADE UP OF?
•WHAT IS A CELL MADE UP OF
•PLASMA MEMBRANE/CELL MEMBRANE
•CELL WALL

3. DISCOVERY OF CELL
ROBERT HOOKE – DISCOVERED CELL IN THE YEAR 1665

4. MICROSCOPE

7. CELL THEORY IS MADE UP OF THREE IDEAS
•All organisms are made up of one or more
cells.
•Cells are the basic unit of structure and
organization of organisms.
• New cells come from pre-existing cells.

8. WHAT ARE LIVING THIS MADE UP OF?
ONION PEEL

9. TYPE OF ORGANISMS
1. Unicellular organisms
• An organism made of only one cell
• These organisms are very small and need to be seen with a
microscope
• Example: amoeba, paramecium, fungi, bacteria etc

10. 2. Multicellular organisms
• Organisms made of two or more cells
• These organisms are able to be seen with the naked eye
• Multicellular organisms arise in various ways, for example
by cell division or by aggregation of many single cells.

11. DO ALL THE CELLS LOOK SAME?
CELLS VARY IN :
• Size
• Shape
• Function
SMALLEST CELL LARGEST CELL LONGEST CELL

12. SHAPE OF CELLS
• Shape of a cell is evolved based on its function
• Shape can be simple or complex
• Cells can be round, flattened, cylindrical, elongated, branched etc

13. WHAT ARE CELLS MADE UP OF?
Three main features in every cell :
•Plasma membrane
•Nucleus
•Cytoplasm
All activities inside the cell and interactions of the cell
with its environment are possible due to these features
All the components that make up cell is known as cell
organelles

15. PLASMA MEMBRANE
• Also known as cell membrane
• Extremely delicate, thin, elastic, living and semi permeable
membrane
• Made up of lipids, proteins and carbohydrates
• Maintain shape and size of the cell
• Protect internal content of the cell
• Regulates entry and exit of substances in and out of the cell

16. WHY IT IS KNOWN AS A SEMIPERMIABLE MEMBRANE ?
•The plasma membrane forms a barrier between
the cell organelles from the outside
environment.
•It allows only certain molecules to pass through
it.
•It facilitates communication and signaling
between the cells.

17. TRANSPORT ACROSS CELL MEMBRANE
1. Diffusion
• Diffusion is the movement of molecules from a region of higher
concentration to a region of lower concentration down the
concentration gradient.
• Liquid and gases undergo diffusion as the molecules are able to move
randomly.
2. Dialysis
• It is the diffusion of solutes across a selectively permeable
membrane. A selectively permeable membrane is the one that allows
only specific ions and molecules to pass through, while it obstructs
the movement of others.

18. 3. Osmosis
• It is the movement of solvent molecules from the
region of lower concentration to the region of higher
concentration through a semipermeable membrane.
• Since water is solvent in every living being, biologists
define osmosis as the diffusion of water across a
selectively permeable membrane.
•Example, plants take water and minerals from roots
with the help of osmosis.

19. EXAMPLE FOR OSMOSIS

20. EXAMPLE OF OSMOSIS FROM OUR DAY TO DAY LIFE

21. CELL WALL
• A cell wall is defined as the non-living component, covering the
outmost layer of a cell.
• Its composition varies according to the organism and is permeable in
nature.
• The cell wall separates the interior contents of the cell from the
exterior environment.
• It also provides shape, support, and protection to the cell and its
organelles.
• However, this cellular component is present exclusively in eukaryotic
plants, fungi, and few prokaryotic organisms.
• The cell wall lies outside the plasma membrane

23. FUNCTION OF CELL WALL
•When a living plant cell loses water through
osmosis there is shrinkage or contraction of the
contents of the cell away from the cell wall. This
phenomenon is known as plasmolysis
•Cell walls permit the cells of plants, fungi and
bacteria to withstand very dilute (hypotonic)
external media without bursting