Organisation of cells, tissues, organs and systems
Living Cells:
There are 100 trillion cells in an adult’s body and all function collectively to maintain an individual life. Each human life begins with a single cell, a fertilised ovum, which divides to form two cells, four cells…so on. Cells exhibit specialist functions. There are about 200 different types of cells in our body.
All Cells Have:
A membrane – which is a thin wall that holds in the cytoplasm and controls what enters and leaves the body.
A cytoplasm – Which is jelly providing energy to keep the cell alive. Chemical reactions take place here in the cytoplasm.
A nucleus - this controls cell division and it is responsible for the function of the individual cell e.g. nerve cell.
Specialized cells:
Nerve cells - they conduct electrical impulses to and from the brain. These can be very long and connects distant parts of the body to the spiral cord and brain. The chemical reaction causes impulses to travel along the fibre.
Cilicated cells – these are from the lining of the nose and windpipe, the tiny hairs called cilia continually move keeping up a stream of fluid (mucus) that carries dust and bacteria away from the lungs.
Components inside of a cell are called organelles; the following organelles are in a typical cell.
Nucleus:
A nucleus consists of a large irregular shaped structure surrounded by a membrane called the nuclear envelope. Inside the nucleus is found the genetic information in the form of chromosomes which allows the cell to be able to make other parts of the cell or chemicals such as enzymes or hormones, for use inside or outside the cell. The chromosomes are made of nuclear materials sometimes called chromatin but more correctly known as DNA (Deoxyribose Nucleic Acid). The chromosomes contain codes to make proteins within the nucleus and the information’s on the codes (genes) is copied on to a smaller molecule of chromatin RNA (Ribose Nucleic Acid). The RNA can pass through the nuclear envelop via the nuclear pores. There are 23 pairs of chromosomes in every human cell except red blood cells, eggs and sperm.
Ribosomes:
They are found either free in the cytoplasm or attached to the rough endoplasmic reticulum. Each ribosome consists of two protein sub units. The protein sub units are made using information in the nucleolus in the nucleus. The function of the ribosomes is to make individual proteins they RNA from the nucleus is the code to allow amino acids to be strung together to make a protein. There are thought to be different ribosomes to process each piece of RNA making proteins.
Rough Endoplasmic Reticulum (RER):
RER is the transport system throughout the cell it can have ribosomes studded on its surface where proteins are made. Proteins can then be carried to other parts of the cell. Some ER has no ribosomes and is known as smooth endoplasmic reticulum, this SER is thought to be a site of making lipids, which can be combined with proteins made on ribosomes to form other chemicals or molecules.
Cytoplasm:
This is the jelly like material that supports and separates all the cells organelles, it consists mostly of water, with various
