Biology Past Paper PDF

Chapter 6: Blood and Circulation (Pages 89-92, 94) ​ Blood Composition: Blood is composed of plasma, red blood cells, white blood cells, and platelets. Plasma is a yellow liquid that carries nutrients, hormones, and waste products. Red blood cells transport oxygen using hemoglobin, wh...

Chapter 6: Blood and Circulation (Pages 89-92, 94) ​ Blood Composition: Blood is composed of plasma, red blood cells, white blood cells, and platelets. Plasma is a yellow liquid that carries nutrients, hormones, and waste products. Red blood cells transport oxygen using hemoglobin, while white blood cells are involved in immune responses. Platelets play a crucial role in blood clotting. ​ Circulatory System: The heart pumps blood through a network of blood vessels, which include arteries (carrying blood away from the heart), veins (returning blood to the heart), and capillaries (where gas and nutrient exchange occurs). The heart has two sides: the right side pumps deoxygenated blood to the lungs, while the left side pumps oxygenated blood to the rest of the body. ​ Heart Structure and Function: The heart consists of four chambers: two atria and two ventricles. Valves prevent backflow of blood, ensuring it flows in one direction. The heart's pumping action is controlled by electrical impulses from the pacemaker cells in the right atrium. ​ Blood Pressure: Blood pressure is the force exerted by circulating blood on the walls of blood vessels. It can be affected by various factors, including physical activity and emotional stress. High blood pressure can lead to health issues such as heart disease and stroke. ​ Blood Transfusions: The process of transferring blood products into a person's circulation intravenously. Blood transfusions are necessary when a person loses a significant amount of blood. Compatibility between blood types is crucial to prevent adverse reactions. The main blood groups are A, B, AB, and O, with O being the universal donor and AB the universal receiver, Blood type O can donate to all blood types because it has A or B antibodies and no antigens, so it won't react with any other blood type. Blood type AB can receive from all types because it has no antibodies against A or B, but it has A and B antigens, allowing it to accept any blood without reaction.  Disease ​ Immune Response: The body has several defense mechanisms against pathogens, including physical barriers (skin), immune cells (white blood cells), and antibodies. The immune system can recognize and remember pathogens, providing immunity against future infections. ​ Vaccination: Vaccines contain weakened or inactive pathogens that stimulate the immune system to produce antibodies without causing disease. This provides long-term immunity. ​ Antibiotics: Antibiotics are drugs that kill or inhibit the growth of bacteria. They are effective against bacterial infections but not against viruses. The misuse of antibiotics can lead to antibiotic resistance, making infections harder to treat. ​ Prevention and Treatment: Good hygiene practices(prevention), vaccination (prevention and treatment), and the use of antibiotics (treating) are essential for and treating infectious diseases. Public health measures, such as sanitation and education, also play a critical role in controlling disease outbreaks. Disease and Immunity ​ Disease occurs when something in the body does not function properly or when a foreign substance or organism enters the body. Symptoms and Signs ​ Symptoms: Manifestations of disease that are apparent to the patient; subjective evidence of disease. ​ Signs: Manifestations of disease that a physician perceives; objective evidence of disease. Immune System ​ Innate Immunity: Components of the immune system present from birth. 📈 ​ Adaptive Immunity: Components and processes of the immune system that adapt based on previous experiences with pathogens.bvcbv w Lines of Defence 1.​ Barriers: Physical mechanisms that keep pathogens out of the body. 2.​ Phagocytes: Cells that attack and eliminate invaded pathogens. 3.​ Lymphocytes: Cells that learn from phagocytes how to specifically and effectively kill certain types of pathogens.  ○​ Dendritic Cells: A type of phagocyte that displays parts of pathogens (antigens) on their membranes for presentation. ○​ Macrophages: Phagocytes that patrol tissues and eliminate pathogens; can be controlled by lymphocytes. ○​ Neutrophils: Phagocytes that kill pathogens, often sacrificing themselves in the process. Inflammation ​ A reaction from tissue in response to signaling molecules, indicating an immune response. Pathogens ​ Definition: Microorganisms that cause disease, including bacteria, viruses, and fungi. ​ Entry Routes: Pathogens can enter the body through the respiratory system, skin, and contaminated food or water. (holes) Types of Pathogens ​ Bacteria: Single-celled organisms without a nucleus that reproduce by multiplication. ​ Fungi: Organisms similar to plants but have no chlorophyll; often associated with poor hygiene. ​ Viruses: Intracellular parasites that replicate by stealing enzymes from host cells; characterized by their small size and that they don’t have a cell wall or nucleus. Barriers to Infection ​ Mechanical Barriers: Physical blockages that prevent pathogens from entering the body. ​ Chemical Barriers: Antimicrobial molecules that attack pathogens. Lymphatic System ​ Composed of lymph vessels, lymph nodes, bone marrow, spleen, and thymus; functions as the body's sewage system. ​ Drained tissue fluid is sent to lymph nodes for screening, where dendritic cells present pathogen parts (antigens). Antigens ​ Definition: Small parts derived from pathogens. ​ Presentation: Phagocytes (dendritic cells) present antigens on their surface after disassembly, referred to as Antigen Presenting Cells (APCs). ​ Types of Antigens: ○​ Foreign Antigens: Antigens that do not originate from the body. ○​ Self Antigens: Antigens that originate from the body.  ​ The adaptive immune system can distinguish between foreign and self antigens. Lymphocyte Functionality ​ T- and B-Lymphocytes: Trained to recognize only one specific antigen; new T- and B-lymphocytes are continuously created to recognize different antigens, even those that may never be encountered. ​ Only the T-cell that recognizes the antigen presented by the dendritic cell becomes active. ​ T-Cells: Can activate B-cells and re-activate macrophages, enhancing their pathogen-killing capabilities. ​ B-Cells: Produce antibodies in response to antigens. Antibodies ​ Definition: Proteins produced by activated B-cells. ​ Structure: Y-shaped and antigen-specific. ​ Function: Neutralize pathogens by preventing their movement and interaction. Memory Cells ​ A small portion of activated B- and T-cells remain as memory cells after the immune response. ​ Memory B-Cells: Produce low amounts of antibodies upon re-exposure to the same antigen. ​ Memory T-Cells: Continuously search for the specific antigen, enhancing the immune response upon subsequent exposures.