Cells, tissues and organs - key points

Animal and plant cells
1. Most human cells are like most other animal cells and contain a nucleus, cytoplasm, cell membrane, mitochondria and ribosomes.
2. 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.
Diffusion
1. The greater the difference in concentration, the faster the rate of diffusion.
2. 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.
3. Dissolved substances and gases such as oxygen move in and out of cells by diffusion.
Tissues and organs
1. A tissue is a group of cells with similar structure and function.
2. Organs are made of tissues. One organ may contain several types of tissues.
Specialised cells
1. Cells may be specialised to carry out a particular function.
2. Examples of specialised cells are fat cells, cone cells, toot hair cells and sperm cells.
Organ systems
1. Organ systems are groups of organs that performs a particular function.
2. Plants organs include stems, roots and leaves.
3. The digestive system in a mammal is an example of a system where substances are exchanged with the environment.
Bacteria and yeast
1. A bacterial cell contains of cytoplasm and a membrane surrounded by a cell wall. The genes are not in a distinct nucleus.
2. Yeast is a single-celled organism. Each cell has a nucleus, cytoplasm and a membrane surrounded by a cell wall.

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Cells, tissues and organs - key points

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