IGCSE Revision- Biology
Chapter 2- Cells
2.1 Animal and plant cells
Cells: The smallest units from which all organisms are made
MICROSCOPES
- The kind of microscope that is used in a school laboratory is called a light
microscope- magnify about 1500 times
- A photograph taken by a light microscope is called a photomicrograph
- To see smaller things in a cell, an electron microscope is used. This can magnify
up to 500 000 times. A photo taken with this microscope is called an electron
micrograph
CELL MEMBRANE
- The cell membrane is a very thin layer of protein and fat
- This controls what goes in and out of the cell
- It is said to be partially permeable
CELL WALL
- All plant cells’ cell walls are made of cellulose
- Animal cells never have cell walls
- Cellulose belongs to a group of substances called polysaccharides
- Cellulose forms fibers which criss-cross over another to form a strong wall
- If the cell absorbs too much water, the cell wall stops it from bursting
- It is fully permeable
CYTOPLASM
- The cytoplasm is a clear jelly
- About 70% of it is water
- It contains many substances absorbed in it especially, proteins
- Many different metabolic reactions take place in the cytoplasm
VACUOLE
- This is a fluid-filled space inside a cell which is surrounded by its own membrane
- Plant cells have very large permanent vacuoles which contain the solutions of
sugars and other substances called cell sap
- When the vacuole is full it presses outward on the rest of the cell and helps it to
keep its shape
- Animals cells have small vacuoles called vesicles
NUCLEUS
- Nucleus is where the genetic information is stored
- This information is kept in the chromosomes, which are inherited from the
organisms’s parents
- The chromosomes are made of DNA
Chapter 2- Cells
2.1 Animal and plant cells
Cells: The smallest units from which all organisms are made
MICROSCOPES
- The kind of microscope that is used in a school laboratory is called a light
microscope- magnify about 1500 times
- A photograph taken by a light microscope is called a photomicrograph
- To see smaller things in a cell, an electron microscope is used. This can magnify
up to 500 000 times. A photo taken with this microscope is called an electron
micrograph
CELL MEMBRANE
- The cell membrane is a very thin layer of protein and fat
- This controls what goes in and out of the cell
- It is said to be partially permeable
CELL WALL
- All plant cells’ cell walls are made of cellulose
- Animal cells never have cell walls
- Cellulose belongs to a group of substances called polysaccharides
- Cellulose forms fibers which criss-cross over another to form a strong wall
- If the cell absorbs too much water, the cell wall stops it from bursting
- It is fully permeable
CYTOPLASM
- The cytoplasm is a clear jelly
- About 70% of it is water
- It contains many substances absorbed in it especially, proteins
- Many different metabolic reactions take place in the cytoplasm
VACUOLE
- This is a fluid-filled space inside a cell which is surrounded by its own membrane
- Plant cells have very large permanent vacuoles which contain the solutions of
sugars and other substances called cell sap
- When the vacuole is full it presses outward on the rest of the cell and helps it to
keep its shape
- Animals cells have small vacuoles called vesicles
NUCLEUS
- Nucleus is where the genetic information is stored
- This information is kept in the chromosomes, which are inherited from the
organisms’s parents
- The chromosomes are made of DNA
