Cells, tissues and organs - key points

Cells, tissues and organs - key points

1. Animal and plant cells

   • Most human cells are like most other animal cells and contain a nucleus, cytoplasm, cell membrane, mitochondria and ribosomes.
   • Plant and algal cells contain all the structures seen in animal cells as well as a cell wall. Many plant cells also contain chloroplasts and a permanent vacuole filled with sap.

2. Diffusion

   • The greater the difference in concentration, the faster the rate of diffusion.
   • Diffusion is the net movement of particles from an area where they are at a high concentration to an area where they are at a lower concentration.
   • Dissolved substances and gases such as oxygen move in and out of cells by diffusion.

3. Tissues and organs

   • A tissue is a group of cells with similar structure and function.
   • Organs are made of tissues. One organ may contain several types of tissues.

4. Specialised cells

   • Cells may be specialised to carry out a particular function.
   • Examples of specialised cells are fat cells, cone cells, toot hair cells and sperm cells.

5. Organ systems

   • Organ systems are groups of organs that performs a particular function.
   • Plants organs include stems, roots and leaves.
   • The digestive system in a mammal is an example of a system where substances are exchanged with the environment.

6. Bacteria and yeast

   • A bacterial cell contains of cytoplasm and a membrane surrounded by a cell wall. The genes are not in a distinct nucleus.
   • Yeast is a single-celled organism. Each cell has a nucleus, cytoplasm and a membrane surrounded by a cell wall.