There is a type of white blood cell called plasma cells which are produced in the bone marrow as B cells then mature into plasma cells, these produce antibodies. Antibodies are either attached to cell surface membranes or secreted as soluble glycoproteins. Antibodies are large Y-shaped proteins which the immune system uses to neutralise and lead to the elimination of foreign bodies. Antibodies are glycoproteins, due to carbohydrates binding to amino acid residues on the polypeptides; these are composed of four polypeptide chains, of which, two heavy chains and two light chains to form the complete antibody. There are small regions at the tip of the antibody called the antigen binding sites; this region is hugely diverse due to rand

The human body has numerous cells with differing functions but the same basic. The shell of the cell is the plasma membrane and is selectively permeable allowing it to control what enters and leaves, this surrounds the cytoplasm which is a jelly like substance that may appear grainy as it contains organelles. The nucleus, the largest of the organelles contains chromosomes which are made of DNA and carry the instructions for the cell. The nucleolus is a darker stained region in the nucleus that is densely packed DNA and makes ribosomal and packages it with ribosomal protein to make ribosomes. Just outside the nucleus is the rough endoplasmic reticulum (RER), which has a rough appearance due to the ribosomes that cover some endoplasmic reticulum (ER). The ribosomes translate the instructions carried on mRNA into protein (protein synthesis). Some ER lacks ribosomes, this is referred to as smooth ER and is responsible for making lipids and steroid. Golgi body collects and processes protein and lipid which bud of as vesicles and go to either the surface membrane (secretion) or to form lysosomes. Lysosomes contain powerful hydrolytic enzymes that break things down, their role is to destroy damaged organelles/cells and bacteria cells. Also within the cell are mitochondria that complete the later stages of aerobic respiration and synthesis, producing ATP (a chemical energy) for the cell.

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Human cells have 23 pairs of chromosomes giving a total of 46, the exceptions to this are the reproductive cells they have only 23 single chromosomes, as fertilisation takes place the two single sets of chromosomes unite to develop a genetically unique organism (Enotes.com). The sperm cells sole function is to carry its chromosomes to the female egg cell so that this process can take place. The structure of the sperm cell is designed specifically for this function; it has three sections, the head, the midpiece and the tail (flagellum). In the head is the nucleus which contains its 23 single chromosomes and at the tip it has acrosome which is an organelle of a cap-like structure derived from Golgi apparatus and contains enzymes to break down the egg membrane. The midpiece has a central filamentous core with many mitochondria coiled around it to produce ATP giving the sperm cell the energy it needs to travel through the female cervix to the egg cell. There is a thin layer of cytoplasm and an outer smooth membrane around the flagellum which lashes to in order to propel the sperm cell forward and helps it burrow through the egg cells membrane (national centre for biological information)

The function of the egg cell is to be fertilized by a sperm cell, if this does occur its function then becomes to provide food for the new cell. It is the largest cell in the human body and has a lot of cytoplasm, surrounded by the plasma membrane that is responsible for regulating the cell’s chemical composition. Within the cytoplasm is the nucleus which contains 23 single chromosomes that will unite with chromosomes from the sperm cell when fertilised, the cytoplasm also has droplets of lipids, which if the egg is fertilised will be used as food during the embryos early stages. The cell is encased in a glycoprotein membrane called the zona pellucida, when a sperm cell penetrates the plasma membrane it leads to the modification of the zona pellucida blocking more sperm from entering the egg. This modification happens when enzymes released into the zona pellucida by cortical granules (vesicles just under the plasma membrane) hardening the zona pellucida meaning they can’t get through the membrane therefore stopping more than one sperm fertilising the egg (Linda J. Heffner, Danny J. Schust).

The motor neuron sends signals to the muscles for joint control, this is achieved by the ‘upper motor neurons’ in the brain relaying signals to the ‘lower motor neurons’ in the spinal cord, then to the muscles. It is made up of a cell body, axon and dendrite. The code for production of the neurotransmitter substances are in the nucleus and this is transported along with protein in a dense group of ribosomes and ER (Nissl granules). The axon is where rapid transmission of nerve impulses occurs; “synapse, where two nerves join, is the slowest part of transmission, so the longer the axon, the fewer synapse, and the faster the impulses transmitted”. The axon also contains axoplasm that permits transport from the cell body to the axon. It has Schwann cells wrapped around it forming a fatty sheath called the myelin sheath which provides electrical insulation, between the Schwann cells are nodes of Ranvier which facilitates the rapid conduction of the nerve impulses. Dendrites branch out from the cell body and allow communication between neurons by connecting with the terminal branches of the axon. At the ends of the dendrites are synaptic knobs that contain many mitochondria to provide energy for active refilling of the synaptic vesicles which are used for the modification and release of chemical transmitters across the synapse (bio factsheet 1997).

The red blood cells main function is to transport oxygen from the lungs to other cells in the body, it also takes waste carbon dioxide from cells lungs. RBC’s are biconcave in shape which means they have a larger cell membrane surface enhancing the diffusion of oxygen. They are around 6-8 micrometers and are flexible; these two features allow it to pass through the minute capillary alleyways between cells in the tissues. Unlike most cells RBC’s have no nucleus or other organelles, they are passive and simply get swept along by the blood so can sustain the little energy they need by a form of anaerobic respiration therefore have no need for mitochondria. The lack of organelles also leaves more room for a substance called haemoglobin, haemoglobin is a complex molecule composed of protein and iron that is responsible for picking up the oxygen from the lungs and transporting to the other cells in the body. They also contain an enzyme called carbonic anhydrase which carries the carbon dioxide from the other cells in the body to the lungs so it can be breathed out (Erich Rosenberger M.D.)

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There are many different types of cells in the human body, looking at these four specialised cells shows how the basic structure remains the same, the red blood cell might be seen as the exception, but still has a main body surrounded by a plasma membrane. Each cell differs in shape, size and the amount of organelles it has, for example the sperm cell needs lots of energy so has lots of mitochondria whereas the red blood cell is passive so needs little

om genetic mutations leading to amino acid chain variations causing a hyper variable region that allows it to bind to many different antigens.

Adaptive immunity is the immune response that involves antibodies. It is undeveloped at birth, and is the response of the lymphocytes to specific antigens.

Antibodies are heavy globular plasma proteins that belong to the family of proteins, immunoglobins. They have sugar chains attached to some of their amino acids making them glycoproteins. Each of their heavy chains has two regions; the constant region (carboxyl-terminal end) for biological effector functions and the variable region (amino-terminal end) for antigen recognition. The light and heavy chains forming the antibody have inter and intra chain disulphide bridges which hold the chains together, the quantity of bonds varies between different antibody molecules. They have a hinge region where the arms of the antibody molecule form a Y-shape; it is named the hinge region due to segmental flexibility at this point. Antibodies have a massively variable antigen binding site due to the different heavy and light chain amino acid configurations.

After birth the only antibodies present in the body are the ones passed over by passive immunization from the mother. Early active immune system antibodies develop in the first few years of life.

The main function of each antibody is to specifically bind to one or few similar antigens (foreign molecules). The structure of antibodies relates to the three main functions; activity, versatility and specificity. Antibodies prevent pathogens from damaging or entering cells by binding to them. Antibodies stimulate macrophages to engage in the removal of pathogens and also stimulate other immune responses. They bind to various cells such as phagocytes, lymphocytes, platelets etc. this binding leads to the activation of these cells to perform immune functions such as antibody production and phagocytosis. Antibodies can also bind together when they’re bound to pathogens, linking them together and stopping the pathogens from moving or causing damage.

The function of an antibody binding to an antigen is provided by the structure of the variable region which has the antigen-binding site (known as the Fragment antigen-binding fragment made from one constant and one variable region); the variable amino acid configuration allows a diverse possibility of specific antibodies to bind with antigens found on foreign bodies. The Fragment crystallisable region at the base of the antibody triggers the appropriate immune response for the situation, for example clumping together (where the Fab fragment joins with the Fc region of another antibody) or triggering the release of histamine in an allergic reaction.

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There are five different antibody isotypes in humans; IgG, IgA, IgM, IgD, and IgE. IgG is the main antibody in the blood however it can move throughout the body’s tissue. It forms the majority of the active immune antibody response to pathogens. It is also able to cross the placenta during pregnancy, passing on passive immunisation from the mother to the developing foetus. IgA is present in bodily fluids in entrances to the body, such as tears, breast milk, and saliva and also in the respiratory tract, urogenital tract and digestive tract, and its function is to prevent colonisation from pathogens. IgM is either present on B cell surfaces or in a soluble secreted form (in which is the largest antibody due to its pentamer form) in the blood and it is involved in the early immune response and can kill pathogens. IgD is the antigen receptor on B cells not already exposed to antigens. IgE is involved in the allergic response to foreign bodies and releases histamine when bound to allergens. The B cell will produce these various isotypes at different stages of its development.

Antibodies are secreted by a type of white blood cell called a plasma cell. Antibodies can occur in two physical forms, a soluble form that is secreted from the cell, and a membrane-bound form that is attached to the surface of a B cell and is referred to as the B cell receptor (BCR). The BCR is only found on the surface of B cells and facilitates the activation of these cells and their subsequent differentiation into either antibody factories called plasma cells, or memory B cells that will survive in the body and remember that same antigen so the B cells can respond faster upon future exposure.[4] In most cases, interaction of the B cell with a T helper cell is necessary to produce full activation of the B cell and, therefore, antibody generation following antigen binding.[5] Soluble antibodies are released into

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