- Cells are the building blocks of an organism.
- Unicellular organisms are made up of only one cell, for example bacteria.
- Multicellular organisms are made up of lots of cells, for example a human.
Cell Structure
- Cells may look different but they have the same basic structure.
- Most cells have the following structures: cell membrane, cytoplasm, nucleus, small vacuole and mitochondrion.
- Plant cells have extra structures: chloroplasts, cell wall and large vacuole.
Functions of the Cell Organelles
Cell membrane: holds the cells together and controls what can enter and leave the cell.
Cytoplasm: watery fluid that holds the organelles in place.
Nucleus: controls cell activities and contains DNA.
Small vacuoles: stores food and waste.
Large vacuoles: gives structure to a plant.
Cell wall: provides support and structure.
Chloroplast: contains chlorophyll which is a green pigment used to trap sunlight to make food for the plant. This reaction is called photosynthesis.
Cell Organisation
Cells lead to tissue which leads to an organ which leads to a system which leads to an organism.
- A group of cells working together is called a tissue. For example nerve tissue in animals and xylem tissue in plants.
- Tissues work together to form an organ. For example the heart in animals and the stem in plants.
- Different organs work together to form a system. For example the digestive system in animals and the root system in plants.
- Systems work together to make an organism. For example, a tree or a person.