Cells

What is a Cell ?

Cells were first discovered in by 1665 by Robert Hooke who used a microscope he built himself to observe microscopic living things in drops of lake water.

A Cell is the basic building block of life. There are millions of different types of Cells. Some living things contain millions of Cells, some are just one Cell. Not all Cells look the same and some Cells have different parts to do different jobs.

Animal Cells

There are millions of different types of animal Cells, each within a specific job. However, all animal Cells have three parts in common. They all have:-

  1. Cell Membrane - The 'skin' of the cell, the cell membrane controls the movement of substances into and out of the cell.

  2. Nucleus - The 'brain' of the cell, the nucleus controls everything that happens within the cell. The nucleus contains the genetic material.

  3. Cytoplasm - The cytoplasm is a 'jelly-like' substance, most chemical reactions take place here.


Plant Cells

Just like animal cells, there are millions of different types of plant cells, each within a specific job. A plant cell has:-

  1. Cell Wall - Gives the cell is rigid shape.

  2. Cell Membrane - The 'skin' of the cell, The cell membrane controls the movement of substances into and out of the cell.

  3. Nucleus - The 'brain' of the cell, the nucleus controls everything that happens within the cell. The nucleus contains the genetic material.

  4. Vacuole - Filled with cell sap, works with the cell wall to give the cell its shape.

  5. Cytoplasm - The cytoplasm is a 'jelly-like' substance, most chemical reactions take place here.

  6. Chloroplasts - Chloroplasts are only found in leaf cells, they contain the chemical Chlorophyll, which absorbs Light Energy for Photosynthesis.


Specialised Cells

All animal and plant cells contain the parts shown above, but these cells all look very different, depending on the jobs they do. Below is some examples of the ways that cells can be specialised:-


Red Blood Cell

The image above shows red blood cells. Red blood cells carry Oxygen around the body. A red blood cell is specialised in two ways:-

  1. Contains Haemoglobin, a chemical that can carry Oxygen.

  2. Has a biconcave shape, giving it a big surface area.


White Blood Cell

The image above shows a white blood cell. White blood cells are part of the body's immune system. A white blood cell is specialised in two ways:-

  1. Makes antibodies, chemicals which attack viruses and bacteria in the body.

  2. Can change shape, to engulf bacteria and digest them.


Nerve Cell

The image above shows a nerve cell. Nerve cells transmit signals around the body. A nerve cell is specialised:-

  1. Long and thin, to quickly send signals long distances in the body.


Root Hair Cell

The image above shows a plant's root hair cell. A root hair cell is specialised:-

  1. Long and thin, to give a large surface area for the transfer of water and nutrients from the soil.


Guard Cell

The image above shows a plant's leaf guard cell. The guard cell allows water to leave the leaf. A guard cell is specialised:-

  1. Can open and close, to let water leave the leaf, or to stop water leaving when needed.


Egg Cell

The image above shows an egg cell. Egg cells are part of the reproductive system. An egg cell is specialised :-

  1. Nucleus contains only 1/2 the DNA required to create a new organism.

  2. Has a lot of cytoplasm containing nutrients to keep the cell alive until implantation.


Sperm Cell

The image above shows a sperm cell. Sperm cells are part of the reproductive system. A sperm cell is specialised:-

  1. Nucleus contains only 1/2 the DNA required to create a new organism.

  2. Has a tail, to help it 'swim' to the egg cell .