Chapter 1. Cells [JHS]

Several characteristic of living organism:
1. They reproduce
2. They take nutrients
3. They respire
4. They Grow
5. They excrete
6. They Move
7. They are sensitive
8. They are made of cells

Cell Structure
All animals and plants are made up of cells. Most cells have:

* A nucleus – controlling the activity of the cell. All cells have these at one point.
* Cytoplasm – where chemical reactions occur. Inside the cytoplasm are enzymes which speed up these reactions. Cytoplasm also contains mitochondria which is where energy is released.
* A cell membrane – to control the passage of substances in and out of the cell.

Plants cells also have

* Cell walls – to strengthen the cell.
* Chloroplasts – to absorb sunlight energy to make food by photosynthesis.
* Vacuole –full of cell sap.

Functions of organelles
1. Cell walls – to strengthen the cell.
2. Cell membrane – to controls what goes in and out of the cells
3. Vacuoles – contain cell sap
4. Chloroplasts – to absorb sunlight energy to make food by photosynthesis
5. Mitochondria – release energy from food
6. Nucleus – stores inherited information

Cells, tissues and organs
Cells act together to form tissues. For instance, the cells on the surface of a leaf form “pallisade tissue”. A group of cells with similar structures and a particular function are called a tissue. Tissues are grouped together to form an organ. A leaf is an organ. Organs are grouped together to form an organism such as a whole plant or animal.

Organelle –> Cells –> Tissue –> Organ –> Organ system –> Organism

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