Inside a cell

Cells are divided into two broad categories - prokaryotic cells and eukaryotic cells. Prokaryotic cells were the first kind of life to appear on earth and existed for millions of years until a branch evolved into eukaryotic cells.

The main difference between the two cells is how they store their genetic information. 

The cell wall gives the cell its structure, prevents dehydration and protects the genetic information held within the cell.

In prokaryotic cells the genetic information is found within the whole cell, coiled up like a tangle of rope. Only a single loop of DNA is present in these cells.

Cytoplasm is the fluid inside the cell. 

Ribosomes are responsible for protein production. In a prokaryotic cell the ribosomes are loose within the cytoplasm. 

Prokaryotic cells reproduce by binary fission (the cell replicates itself then divides). Prokaryotic cells reproduce much faster than eukaryotic cells. 

Most of life on earth is comprised of eukaryotic cells, including humans. Life as we know it would not have been possible without the evolution of eukaryotic cells. 

Eukaryotic cells are different to prokaryotic cells in many ways with one of the biggest difference is how the genetic information is stored. 

In a eukaryotic cell the genetic material is stored within a special membrane called a nucleus. 

Organelles is the overarching term for all the specialised parts found inside an eukaryotic cell. 

Mitochondria are responsible for taking in nutrients and creating energy within the cell. 

The Golgi apparatus collects simple molecules and turns them into more complex molecules, which are then stored or sent out of the cell. 

All animals are comprised of different types of eukaryotic cells. Nerve cells are the communication system within the body. There are three different type of nerve cells found in the human body. 

The sensory nerve cell is responsible for communicating information about external stimuli, for example when we touch something hot these nerve cells send the signal to the brain to move our hand away. Motor nerve cells are the communication system for any type of movement.

Association nerve cells connect the sensory and motor neurons together. 

Dendrites are long branching structures that receive electrical signals from around the body. Axons are similar structures that send electrical signals away from the cell.

Synapses are the gaps between two nerve cells. Electrical or chemical signals can be passed between this area.

Nerve cells, particularly brain cells like this one use an incredible amount of energy. These organelles create energy from oxygen and glucose to power the cell.

 The genetic information is contained within the nucleus.

Blood is a special fluid that flows around the human body (and in the bodies of other vertebrates). Blood is comprised of four types of fluid - red blood cells, white blood cells, plasma and platelets. 

The role of blood is to transport oxygen to where it is needed in the body, to form clots to plug holes created when injuries occur, carry cells designed to fight infections, transport waste products to the liver and kidneys and to regulate body temperature.

Red blood cells transport oxygen around the body. Interestingly in mammals red blood cells do not contain a nucleus. Nuclei are found in red blood cells of all other vertebrates. 

White blood cells defend the body against disease. These cells contain a nucleus and mitochondria. 

Platelets are not actually cells but are small fragments of cells. These are used to help clot blood when an injury occurs. 

Unsurprisingly plant cells differ from animal cells. Both types of cells are eukaryotic but the cells found within plants are needed to perform different function than within animals.

Plant cells have a range of different organelles and the cell wall structure is also quite different. Plant cells are also generally larger than animal cells.  

The cell wall in a plant cell is structured very differently to other eukaryotic cells. These cell walls contain cellulose and protein, giving the plant cell structure and rigidity. 

Every plant cell has a large storage area called a vacuole. Some animal eukaryotic cells have these as well but they are much bigger in plant cells. This area stores food, water and waste.

This is the most important part of a plant cell. Chloroplast contains the chemical chlorophyll which is used to create food from sunlight (via the process of photosynthesis).

Plant cells also contain a nucleus which contains genetic information.

Yeast are single celled, eukaryotic organisms. Humans use yeast for a number of different things like bread making and beer production due to its ability to produce bubbles of carbon dioxide. 

There are over 1,500 different types of yeast and some species have the ability to form into multicelled organisms. 

In the absence of oxygen yeast cells produce carbon dioxide in the cytoplasm. This process is called fermentation. The production of the carbon dioxide bubbles is what causes bread to rise. 

Yeast reproduce asexually (without a partner). To do this the cell forms a bud which will eventually form an identical cell and break away. The reproduction rate depends on the temperature, pH levels and food availability.

The similarities between a yeast cell and other eukaryotic cells makes it an ideal candidate for scientific cell research. About 25% of human genes can be found in yeast cells and these genes are easily identified and separated. 

Genetic information is contained within the nucleus of the yeast cell.