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YOU START LIFE AS A SINGLE CELL FORMED FROM THE SPERM AND THE EGG. From one cell to millions • The sperm and egg form your first cell •This cell will then divide to form two cells and the two cells divide to become 4 cells, then 8 cells, then 16 cells etc •This division goes on from the beginning of your life until the end of your life. What does a cell look like? Cell structure •Cells look different ( there are approximately 210 different types of cells found in the human body) •Each type of cell has a specific job that they do in the human body •However, no matter what the type of job that the cell does in the human body there will be certain features that all cells will have. Cell nucleus Cell membrane Cytoplasm Membrane pores With a normal light microscope you will probably only be able to see the nucleus, cell membrane and cytoplasm but there are a lot more really small organelles In a cell. Golgi complex Cytoplasm What do all these organelles do in a cell? NUCLEUS: The nucleus contains the D.N.A in the cell and is sometimes called the control centre of the cell CELL MEMBRANE: The cell membrane is the outer boundary of the cell which has small holes or pores in its surface to allow substances to move in and out the cell. CYTOPLASM: The cytoplasm is a watery substance which everything in the cell floats in. As the cytoplasm is mainly water there are a lot of substances dissolved in the cytoplasm which the cell is able to use. MITACHONDRIA: The Mitochondria is the powerhouse of the cell. Respiration occurs in the Mitochondria and releases energy for the cell RIBOSOMES: Use the information from the D.N.A to make proteins. Ribosomes can be free or attached to the Endoplasmic Reticulum. ENDOPLASMIC RETICULUM AND GOLGI COMPLEX: These two organelles process and package the proteins made by the ribosomes. DEOXYRIBONUCLEIC ACID •When the sperm and egg fuse to form the zygote all the information that makes you unique is contained in this new cell •This information is contained in your D.N.A (deoxyribonucleic acid) and your D.N.A is found in every one of your cells in your body in the nucleus •Your D.N.A has the code that tells your body what proteins to make. •As everyone's D.N.A is unique you will end up with a unique combination of proteins which in turn makes you unique. Cell nucleus Chromosome: made up of D.N.A cell Double helix Why do cells look different? • Cells all have the same basic blueprint but will have specialised structures that will allow the cell to carry out different tasks in the human body. • All the cells in your body started out from the original cell created from the sperm and egg which was not specialised. •As the number of cells increases they undergo cell differentiation to become specialised so that they are able to carry out a specific job. SPECIALISED CELLS RED BLOOD CELLS OSTEOCYTE (Erythrocytes) (bone cells) SKIN CELLS HORMONE PRODUCING CELLS (E.g.: Pancreatic cells that secrete (Epithelial cells) Insulin) MUSCLE CELLS (E.g.: smooth , cardiac, striated etc) LIVER CELLS (Hepatocyte) NERVE CELLS (e.g. Olfactory receptor cell, cold and heat sensitive Neurons, taste buds, pain sensitive neurons) PIGMENT CELLS (E.g. melanocytes produce skin pigment Retinal pigmented epithelial cells produce eye colour) WHITE BLOOD CELLS E.g.: neutrophil, Eosinophil, Helper T cell Suppressor T cell, Cytotoxic T cell etc FAT CELLS (White fat cells, Brown Cells, Liver Lipocyte) SECRETORY CELLS (E.g.: salivary gland cells, mammary gland cell Sweat gland cells stomach lining cells that secrete Mucus, ceruminous gland cell in ear) PHOTORECEPTOR CELLS (cells in the retina of the eye) RED BLOOD CELLS (Erythrocytes) • Red blood cells have a biconcave shape which increases the surface area of the cell and makes it easier for the cell to move through narrow blood vessels • Red blood cells contain the pigment Haemoglobin which carries oxygen • Mature red blood cells don’t have a nucleus but they only have a life span of 28 days. HUMAN CHEEK CELLS These cells form the lining of the cheek • Cheek cells are a type of epithelial cell • Epithelial cells provide a barrier like the skin. • Cell membrane Nucleus Cytoplasm Bone cells (osteocytes) Fat cells Cardiac muscle Nerve cell (neuron) Striated muscle cells White blood cells Image of human skin cell: . Tissue consists of cells of similar structure. Example Muscle tissue Organs are made up of tissues of different types Example: Heart Organ systems serve the needs of cells for food, air, and waste removal Examples: Respiratory system and Digestive system.