Ways in which body acts as a barrier to pathogens - Skin (sebum, skin flora which has antimicrobial secretions) - Gut flora, HCl in stomach, vomiting - Platelets which help in repairing broken skin - Tears which contain lysozymes - Acidic secretions in vagina Types of immune responses:- Specific and Non-specific Non specific:- inferons, phagocytosis, inflammation, lysozyme action - Inferons:- inhibit viral reproduction pathway by binding to mRNA coded by the virus - Phagocytosis (neutrophil):- engulf the pathogen, enclose in vesicle and release digestive enzymes - Inflammation:- Histamines are released - vasodilation which increases blood flow to the infected area - increases permeability of the blood vessels - antibodies and WBC’s leak out into the infected tissue and destroy the pathogen - Lysozyme action:- contain digestive enzymes which cause lysis of the pathogens walls leading to death oops Specific:- humoral and cell mediated - Humoral (B cells + antibodies) B cells mature in Bone marrow - Pathogen exists - Macrophage sees pathogen and phagocytes it - Macrophage displays antigens of pathogens on its surface and becomes APC - it presents it antigens to the T helper cells - the T helper cells stimulate the B cells - B cells differentiate into B plasma cells and B memory cells - B plasma cells produce antibodies against the antigen - Cell mediated (T cells ) T cells mature in Thymus - Pathogen exists -Macrophage sees pathogen and phagocytes it - Macrophage displays antigens of pathogens on its surface and becomes an APC - it presents the antigens to the T helper cells - the T helper cells stimulate the T killer cells by releasing cytokines - T killer cells kill the infected cell via lysis (creating holes in the cell membrane) Ways in which Antibodies work against antigens - Opsonization (mark them so that the macrophages can find them easily and destroy) - Agglutination (clump the pathogen cells together so easy to destroy) - Neutralisation (neutralise the toxic effects of the antigen) - Complement Activation (encourage proteins with complementary shapes to bind to the pathogen) Types of immunity:- Active, Passive, natural and artificial How does a vaccine work:- Vaccine contains dead/weakened form of the virus - Is introduced to the body - Body develops antibodies against the virus (talk about specific immune responses) - Produce memory cells in the process - So that when the virus infects the individual, they already have the memory cells and are able to produce an immune response in a shorter time Disadvantages of vaccine:- may contain egg which is allergic, might produce an adverse immune response Herd immunity:- when a large part of the population is vaccinated against the pathogen. Good because a large number of the people are immune to the pathogen, therefore lower risk of transmission. Beneficial for those who can’t take the vaccine because they are allergic/too old or young/vulnerable immune systems Evolutionary race:- when a pathogen tries to evade the immune system of the host and the host responds by developing new ways to destroy the pathogen (defend against infection by pathogen) Antibiotics:- chemical that kills/ inhibits growth of bacteria - types - Bactericidal (kills bacteria by creating pores in its cell wall) - Bacteriostatic (inhibits bacterial growth by interrupting metabolic pathways) - How are bacteria gaining resistance against antibiotics - mutation causing one of the bacteria to be resistant - this bacteria survives and reproduces to form resistant bacteria - this acts as selective advantage - over time frequency of the advantageous allele increases - increases resistance against the antibiotics - Hospital protocols while giving out antibiotics DNA Profiling - PCR (amplifies the DNA so we can use for comparison) -Taking small sample of DNA - placing in a thermal cycler - Heat to 90 to break hydrogen bonds between the 2 strands of DNA - Cool to 40-60 so that the primers can anneal on the strands of DNA that needs to be copied - Heat back to 70 so that Taq Polymerase can rebuild the chain using free nucleotides - Repeat cycle to produce how many ever copies of DNA that you need - - - In between use restriction endonuclease to break the copies up into different fragments and fluorescent tags Gel electrophoresis - To arrange the copies based on their masses and charge - Dna is negative because of phosphate so it’ll be attracted to the positive terminal - smaller fragments can move through the pores more easily and hence will be moved the most Analyse the resulting DNA fragment to find similarities in the banding pattern of the DNA. more similarities, more closely related. Death and Decomposition Decomposers:- feed on the organic matter, respire and release the CO2 back into the air where it used by the plants. Inorganic ions are returned to the soil where they are assimilated into plants. Stages of Decomposition:- Tissue break down (skin appears green) - Tissue turns into liquid and leaves the body - Skin blisters and peels off - Skeleton remains Entomology (using life cycle of insects to determine Time of Death) - Decomposers and microorganisms are present almost immediately after death - Flies arrive and eat the tissue and flesh - Lay larvae - Beetles come - Tissue drys up - Therefore flies leave - Beetles stay Ways in which Body temperature can be affected - Clothing - Body fat - Surrounding temp. - Mode of death Rigor mortis (muscle stiffness) - - - - - - Not enough oxygen because cells stop respiring Anaerobically respires and produces lactic acid Changes the pH Shape of ATP changes Actin and myosin fibres can’t unlock without ATP Muscle is in a state of contraction Ways to measure the growth of cultures - Cell counts (pipette a small sample of culture onto a slide with a grid, count the number of cells in the sample and multiply up to give a prediction for the number of cells) - Dilution plating (series of dilution with sterile liquid, count the number of microorganisms on an easily countable plate and work backwards to find the original number of microorganisms) - Mass (known volume is sampled, spun in centrifuge and weighed then multiply the mass by the original volume to find the mass of the culture) - Turbidity (use a colorimeter to check the turbidity, as cultures grow less light is passed through ) Photosynthesis Light dependant reactions (cyclic and non-cyclic phosphorylation - Take place in the the thylakoid membrane (the disc structures) (Photosystem 2) 1. Electrons in chlorophyll get excited by the sunlight and move up the chlorophyll and into the start of the electron transport chain 2. They move through the Electron transport chain and lose energy 3. Meanwhile photolysis of water in the chlorophyll allows for more electrons to be excited 4. The electrons de excite and the released energy is used to pump H+ ions across the membrane creating a high H+ conc. Gradient 5. H+ passes through ATP synthase which turns and binds P to ADP, synthesizing ATP 6. The electrons go to PS1 and excite again 7. In the end they bind with NADP to form NADPH
