Aspartame is an artificial sweetener marketed under the name Nutra-Sweet. A partial Lewis structure for aspartame is shown below. Note that the six-sided ring is shorthand notation for a benzene ring (OC6H5). Benzene is discussed in Section 9.5. Complete the Lewis structure for aspartame. How many C and N atoms exhibit sp2 hybridization? How many C and O atoms exhibit sp3 hybridization? How many and _ bonds are in aspartame? Aspartame is an organic compound and the Lewis structure follows the guidelines outlined in Exercise 55.
Chapter 43 – Immune System I. Introduction A. Immune System An animal body’s defense against agents that cause disease Antigen is a foreign substance/molecule that evokes a specific response by a lymphocyte B. Two Defense Systems 1. Innate Immunity a. You are born with it b. A defense that is active immediately up infection c. Includes coverings i. Skin, Chemical secretions, Lining (of the nose ) 2. Acquired Immunity a. Found only in vertebrates b. Get it after being sick c. Develops more slowly d. Recognition of traits that are specific to particular pathogens i. Chicken pox, and swine flu II. Innate Immunity Ch. 43 1 A. External Defense a. Mucus i. Sticky and located in respiratory track ii. Works with small hairs in trachea to push invader up and away from lungs iii. Saliva and tears bathe exposed epithelia washing away fungi and bacteria iv. Creates a hostile environment for microbes 1. Have lysozymes – destroys cell wall of bacteria b. Skin i. Has a low pH (3-5) ii. The low pH is due to secretions from oil and sweat glands B. Internal Defense a. Phagocytic cells i. Detects fungal or bacteria components (receptors) 1. These are the invading pathogens ii. After detection, phagocytic cell engulfs pathogen in vacuole iii. Vacuole fuses with lysosomes iv. Gases produced in lysosome poison pathogen and then enzymes degrade going down the cell is endocytosis( coming in) a. Types of phagocytic cells Ch. 43 2 1) Neutrophils 2) Macrophages White blood cells 3) Eosinophils 4) Dendritic cells 3. Natural Killer Cells a. Circulate through body and detects abnormal proteins b. Release chemicals that lead to cell death i. It going kill the cell – something is not working well (abnormal protein) 4. Antimicrobial Proteins a. Attack invader (i.e bacteria/microbes) and breaks them open b. They also stop reproduction of the invader c. Types Unique to Vertebrate Immune System i. 1- Interferons 1. Attack viruses 2. Alpha and beta are secreted by a cell that is infected with a virus 3. Gama(symbol) is secreted by T-cells to active macrophages ( white blood cell – phagocytic cell) ii. 2 - Complement System 1. About 30 proteins 2. Found in blood plasma 3. Not activated until come in contact with substances on surface of microbes 4. Will cause a cascade of biochemical reactions that ends in lysis of the microbe a. Cascade is like some one reporting to one and reporting again and then a reaction iii. Inflammation 1. Blood vessels dilates and become more permeable (bigger so things can go in and out) 2. Due to a release of histamine 3. Histamine is a signaling molecule that is stored in mast cells of connective tissues 4. Macrophages and neutrophils become activated (phagocytic cells – WBC) and they release cytokines which are also signaling molecules 5. They cause an increase in blood flow to in the injured area – so blood engorged(inflamed) capillaries causes swelling Ch. 43 3 6. Sometimes have fever which is due to macrophages resetting the body thermostat higher in order to help phagocytosis a. Twisted the ankle – capillary gave a lot blood to it that why it swollen really bad. b. Ex: A boy falls while riding his bike. A scrape on his hand almost immediately begins to bleed and becomes red, warm, and swollen 1. Summarize First line of defense – skin and mucus Second line of defense – phagocytes, natural killer cells, antimicrobial proteins and inflammation III. Acquired Immunity A. Lymphocytes (WBC) a. Originated from stem cells (lymphoid) b. Have receptor proteins on surface that bind to antigens on the foreign molecule i. Receives antigen from the foreign molecule 1. Two Types a. B-cells i. Recognize intact antigen 1. They are together ii. Receptor protein has 2 heavy chain and 2 light chains( crease variability for different antigens) iii. Disulfide brides (weak bonds) links the chains Ch. 43 4 iv. The heavy chains are anchored in the transmembrane region into the cytoplasm v. A “V” regions is created at the other ends where antigens bind 1. Epitope – accessible region of an antigen 2. Epitope associated with the variable regions of a heavy chain and light chain combined vi. After binding a protein, an antibody is secreted (immunoglobulin Ig) b- cell b. T-cells i. Recognized antigen FRAGMENTs bound to major histocompatibility complex(MHC) proteins on the surface of infected cells ii. Receptor protein consists of 1 alpha and 1 beta chain link by a disulfide bridge that is anchored into the transmembrane region Ch. 43 5 iii. Only a single “V” region in T-cells 2. Major Histocompatibility Complex a. Host cell become infected by a pathogen (has antigen) b. Enzymes in host cell breaks the antigen which becomes antigen fragments c. Antigen fragments bind to an MHC protein d. The MHC which antigen fragment moves to the surface of the infected cell e. The T-cell antigen receptor will bind to both the antigen fragment and MHC i. Find the fragment and move to the surface of the cell Ch. 43 6 ii. Two classes of MHC 1. Class I MHC a. Found on all cells with a nucleus b. Recognized by cytotoxic T-cells i. T-cells are divided 2. Class II MHC a. On dendritic cells, macrophages and B- cells b. Recognized by helper T-cells B. Lymphocyte Development a. 1- Differentiation i. B-cell (bone) - Matured on the bone marrows and thymus too ii. T-cell – lymphocyte that left the bone marrow and moved to the thymus where they matured into T-cell iii. Location will cause gene rearrangement, determines which receptors chains to make b. 2- Lymphocyte specific i. A lymphocyte is specific for only one antigen ii. Some recognize our normal bod components 1. Those that could destroy our normal cells 2. However, they get destroyed before any harm is done c. 3- Immune Response i. Primary Ch. 43 7 1. Lymphocyte binds to antigen and triggers proliferation and differentiation (multiple cell division) 2. Results is a close called clonal selection a. Selects which lymphocyte will divide to produce clones b. Makes short lived effector cells and long lived memory cells c. Effector cells take immediate action against antigen d. Memory cells can give rise to effector cell later ii. Secondary 1. If antigen comes back, memory cell gives rise to the effector cells 2. This time it is faster and more efficient response Figure 1 Primary Immune Response Ch. 43 8 IV. Humoral and Cell-Mediated Immunity A. Define 1. Humoral Immunity a. Occurs in blood ad lymph fluid b. B-cells are activated and release antibodies to help neutralize or eliminate toxins/pathogens 2. Cell-Mediated Immunity a. Cytotoxic T-cells are activated b. Kill infected cells, cancer cells and transplanted cells C. Helper T-cells (both humoral and cell-mediated) a. Turns on both B-cells and cytotoxic T-cells b. Make CD4 (protein) on the cell surface which helps bind to Class II MHC on infected cell i. CD4 and CD8 are molecules present on the surface of T-cells where they interact with major histocompatibility (MHC) molecules. c. When bound to infected cell, the help T-cells gives off cytokines which turns on other lymphocytes D. Cytotoxic T-cells (cell-mediated) a. These are the effector cells b. Make CD8 protein on cell surface which bind to Class I MHC on infected cells c. Cytotoxic T-cells gives off proteins that destroy infected cell i. These are fighter cells Ch. 43 9 E. B-cells (humoral) a. A helper T-cell binds to Class II MHC infected cell and releases cytokines b. B- cell is therefore signaled and binds to the antigen on the helper T-cell c. The B-cell proliferates (divided) and differentiates into plasma cells and memory cells d. That plasma releases antibodies e. Antibodies look like B-cell receptor but can not attach to cell membrane f. Binds to antigens and tags for destruction F. Active/Passive Immunization a. Active – arises naturally when you get an infection i. Immunization Ch. 43 10 1. Inject “non-pathogenic” strain of microbe into body and immune system makes memory cells (chicken pox) ii. Passive Immunity 1. Immediate short term protection 2. Get this from mom when born 3. Antibodies cross placenta during pregnancy and breast milk after birth 4. Can also get through injection of antibodies V. Tissue Transplantation 1. Blood Transfusion (A, B, AB and O) a. Red blood cells have specific antigen on cell surface b. Tour body has antibodies to blood antigens that don't match yours c. SO if given the wrong blood type, the new blood cells will be destroyed d. O – no antigen universal donor e. AB – no antibodies Universal acceptor Ch. 43 11 2. Rh Factor a. Red blood cells aslo have another antigen – Rh factor b. Rh factor – you are either (+) or (-) i. Problem for pregnant mom when she is (-) and baby is (+) ii. Not a problem with first pregnancy because the baby has no antibodies yet but will make them because of the baby iii. If the next baby is +, mom’s antibodies will cross and placenta and attack the antigen 1. Have medicine to counteract effect C. Tissue/Organ Transplant a. Rejected by action of MHC molecules b. Works best if donor and recipients MHC match well i. Still give drugs to suppress immune system, ii. Also about the AMC IV. Extreme Immune Response (disease) 3. Allergies a. Hypersensitive reposes to allergens b. First exposure – antibodies to allergen are made and stuck to receptors of mast cell c. Second – exposure – allergen binds to antibody on mast cells A. Release histamine and causes allergy symptoms d. Anapathylatic shock – acute reaction A. Can be threatening B. Blood vessels dilated’ C. Blood pressure drop 4. Autoimmune Disease a. Immune system stars to attach body cells b. Losses ability to recognize itself c. Examples: Lepus, MS, Rheumatoid arthritis d. Insulin=dependent diabetes C. Immunodeficiency Disease Ch. 43 12 1. Inborn (primary) a. Hereditarily i. Humoral cell-mediated defenses do not work ii. Example Sever combined Immune diefiecneity SCID iii. Need bone marrow transplant 2. Acquired (secondary) a. From exposures to chemical/biological agents b. Can be temporary or chronic i. Ex. Aids – caused by HIV ii. `Virus destroys helper T-cells then humoral and cell –mediated defense do not work. Ch. 43 13