Paragraph. 편집하려면 여기를 클릭하세요.
U1. The skin and mucous membranes form a primary defense against pathogens that cause infectious disease.
- Skin and mucous membrane are physical barriers against infection from pathogens
- Skin is constantly replacing its outermost epidermal layer of skin. These dead cells provide effective protection against foreign pathogens
- Skin also secretes a substance called sebum to lubricate the skin. The sebum also lowers the pH of the skin, which effectively helps inhibit bacterial growth
- Mucous membranes line the surfaces of the nasal cavity, trachea, bronchi, and bronchioles (surfaces that are exposed to the outside environment)
- Mucous traps foreign particles and pathogens contained in the air before they reach the lungs
- Mucous contains lysozymes that can damage and kill pathogens
- Trapped pathogens can also be expelled through the mouth or nose, or swallowed and destroyed by the high acidity of the stomach
- Skin and mucous membranes are examples of non-specific immunity
U2. Cuts in the skin are sealed by blood clotting.
- Blood clotting is the process in which cuts or broken blood vessels are repaired and sealed to prevent excessive blood loss
- When a blood vessel is broken or cut, blood platelets collect at the site of the damaged blood vessel forming a platelet plug
U3. Clotting factors are released from platelets.
- The platelets and the damaged tissue release chemical factors called clotting factors
U4. The cascade results in the rapid conversion of fibrinogen to fibrin by thrombrin.
- The clotting factors convert the clotting protein prothrombin to its active form thrombin (enzyme)
- The enzyme thrombin converts clotting protein fibrinogen into the insoluble fibrous protein fibrin
- Fibrin forms a mesh at the point of the broken vessel further trapping other platelets sealing up the damaged vessel and forming a stable clot
- Once the damaged vessel has fully healed, the blood clot dissolves in the blood
U5. Ingestion of pathogens by phagocytic white blood cells gives non-specific immunity to diseases.
- Another type of non-specific immunity (not antigen specific and response is immediate) occurs when phagocytic leucocytes ingest and destroy foreign pathogens
- The main type of phagocytic leucocytes are called macrophages. When pathogens get past the physical barriers, macrophages will engulf foreign pathogens through endocytosis
- Pathogens are recognized as non-self cells by the structure of their protein coat
- Once the pathogen is engulfed, lysosomes within the macrophage contain hydrolytic enzymes that will digest and destroy the foreign pathogens
- Macrophages are the large white blood cell and involved in no-specific immune response.
U6. Production of antibodies by lymphocytes in response to particular pathogens gives specific immunity.
- When a pathogen enters the blood, the specific antigen on the surface of the membrane is identified as being foreign or non-self
- This stimulates a specific immune response in which antibodies are produced that are specific for that particular antigen
- B-lymphocytes are white blood cells that produce antibodies that bind to the antigen on the invading pathogen
- Each lymphocyte is able to produce one type of antibody; however, we have a vast diversity of lymphocytes that are able to respond to millions of foreign antigens.
- Once an antigen has been encountered the B-lymphocytes are stimulated to divide to produce a large amounts of clones of themselves.
- The active B-lymphocytes that are produced are called plasma cells which will begin to produce antibodies
- The plasma cells created, produce and release mass amounts of anitbodies into the bloodstream.
- These antibodies surround and bind to the antigens on the foreign pathogens
- Through a variety of different methods of pathogens are destroyed by the antibodies and other white blood cells.
Some lymphocytes act as memory cells and can quickly reproduce to form a clone of plasma cells if a pathogen carrying a specific antigen is re-encountered.
- Some of these divisions also produce B-cells called memory cells, which stay in the blood in case of a second infection to provide a quick response to the new infection
- The primary response is the production of antibodies to the initial challenge by the invading antigen.
- The secondary response which is much quicker because memory cells are still in the blood occurs after a subsequent challenge y the same antigen.
- Chemicals that induce an immune response inside the body
- Antigens are actually proteins, glycoproteins or other macromolecules on the surface of the cell membrane of the pathogen that are recognized by a specific antibody, to stimulate the immune response
- Protein molecules produced by B-lymphocytes that recognize and bind to the antigens on the foreign pathogens
- Each antibody is specific to each type of antigen
- Antibodies make the pathogen more recognizable to macrophages so that they are easily engulfed and destroyed
- Antibodies also stop viruses from spreading by binding to host cells preventing the viruses from entering
U7. ANTIBIOTIC BLOCKS PROCESSES THAT OCCUR IN PROKARYOTIC CELLS BUT NOT IN EUKARYOTIC CELLS.
- Antibiotics are a type of drug or chemical that inhibits the growth of microorganisms; mainly bacteria
- Antibiotics block cellular processes such as DNA replication, transcription, translation, and cell wall formation
- The first antibiotic discovered was identified as penicillin.
U8. Some strains of bacteria have evolved with genes that confer resistance to antibiotics and some strains of bacteria have multiple resistance.
- Some viruses lack their own metabolism, they have to use the chemical processes of a cell from a host that they infect
- They are unable to reproduce on their own and cannot perform protein synthesis, transcription and other metabolic functions
- Antibiotics work by blocking these vital processes in bacteria, killing the bacteria, or stopping them from multiplying
- Since viruses do not perform their own metabolic reactions antibiotics such as penicillin and streptomycin, are ineffective in treating viral infections.
- Therefore treating viruses with antibiotics is not only useless and ineffective, it can also create antibiotic resistance in bacteria strains.
A3. Effects of HIV on the immune system and methods of transmission
- HIV is a retrovirus that causes AIDS, which is a condition in humans where the immune system fails and is susceptible to life-threatening opportunistic infections
- HIV targets helper- T cells because HIV can bind to proteins on the T cells
- Helper- T cells play an important role in the production of clonal B lymphocyte cells, which produce antibodies for immune response
- Therefore the reduction of T cells will reduce the amount of antibodies produced needed to fight off infection from invading pathogens
- This inability to fight off disease is what eventually causes the person to die