1.1 Cell Structures
|
A Typical Human or Animal Cell
The human body is made up of millions of cells. There are hundreds different types of cells in humans and they have different structures to them, which makes them suitable for carrying out their specific function. Despite these differences in the structure of cells, most human (and animal cells) contain the same components.
We are going to look at a typical human/ animal to see what components we would expect to find there. However, there is no such thing as a typical human/ animal cell because humans and animals are made up of hundreds of different types of cells that all have different structures making them suitable to carry out their specific job. Examples of human cells are, blood cells (white and red), bone cells (osteocytes), nerve cells, muscle cells and many more.
The human body is made up of millions of cells. There are hundreds different types of cells in humans and they have different structures to them, which makes them suitable for carrying out their specific function. Despite these differences in the structure of cells, most human (and animal cells) contain the same components.
We are going to look at a typical human/ animal to see what components we would expect to find there. However, there is no such thing as a typical human/ animal cell because humans and animals are made up of hundreds of different types of cells that all have different structures making them suitable to carry out their specific job. Examples of human cells are, blood cells (white and red), bone cells (osteocytes), nerve cells, muscle cells and many more.
We cannot see the structure of cells by looking at them through a normal microscope. Instead, we must use a light microscope or an electron microscope to see the cell’s structure. A typical human or animal cell will look like the diagram above and contain the following components:
- Nucleus – almost all cells have a nucleus. A nucleus contains the genetic information for cells. A human nucleus will contain the genetic information in 46 chromosomes (we will be looking at chromosomes, DNA and genes in more detail later in the course). Genes control the activities that occur in the cell, such as what proteins or enzymes to make.
- Cytoplasm – a gel-like substance that makes up most of the cell. It is made up of many different substances.
- Cell membrane – the cell membrane is the outside of the cell. It provides a boundary between the cytoplasm and the outside. The cell membrane decides which substances come in and out of a cell. It is partially permeable (meaning that some substances can pass through it).
- Mitochondria – These are found in the cytoplasm of all living cells. They are responsible for some of the chemical reactions that take place in respiration and respiration releases energy that the cell can use. Cells that require a lot of energy have a lot of mitochondria.
- Endoplasmic reticulum – in addition to the cell membrane, there is a network of membranes in the cytoplasm called the endoplasmic reticulum.
- Ribosomes – the endoplasmic reticulum is covered by ribosomes. Ribosomes are responsible for assembling proteins for the cell.
Plant Cell
Plant cells have all the components that a human/animal cell has, and some more components:
- Rigid cell wall – the cell wall is found on the outside of the cell membrane. It is there to strengthen the cell and support the cell’s shape, hence why plant cells have a fixed shape. The cell wall is made from cellulose, which is a carbohydrate.
- Chloroplast – chloroplasts are responsible for photosynthesis in plants. They absorb light energy to make food. Chloroplast contain a pigment called chlorophyll, which makes the cells green in colour. Green parts of the plant, such as leaves, have chloroplasts in them.
- Permanent vacuole – plants cells have a vacuole, which is a relatively large space that is surrounded by a membrane. A vacuole contains cell sap, which is a weak solution of sugar, minerals and salts. Some animal cells have vacuoles but they are only temporary. A vacuole in a plant cell is a permanent feature.