Topic 6

• Keratin in skin provides a physical barrier against pathogens.
• The total number, position, and width of bands are compared.
• The use of dye, fluorescent tag, or UV is employed to visualize.
• Flora (bacteria) on the skin and in the gut compete with pathogens for space, water, minerals, and nutrients.
• Hydrochloric acid in stomach provides a chemical barrier against pathogens.
• Inflammation involves the release of histamine from mast cells/basophiles, which causes arterioles to dilate (vasodilation), increasing blood flow to the site, and results in redness.
• Inflammation also involves the increase in permeability of capillaries, causing blood plasma and white blood cells to enter tissues, resulting in swelling/oedema.
• Interferons are proteins secreted by host cells infected by viruses, which attach to receptors on uninfected host cells, preventing virus binding and entry into the cells, and therefore, the virus cannot replicate and infect more cells.
• Phagocytosis involves the engulfing of a pathogen by a phagocyte/macrophage by endocytosis, forming a phagosome, which then fuses with the lysosome to form a phagolysosome, where the pathogen is digested by lysozymes and antigen is presented on the surface of the macrophage, which becomes an antigen presenting cell (APC).
• The interaction between the antigen presenting cell (APC) and the T helper cell involves antigens from the pathogen associating with major histocompatibility complex II (MHCII) and being translocated to the cell surface, where they are presented to the T cell receptor (TCR) on the T helper cell surface.
• The role of the T helper cell in the immune response involves the release of cytokines, which activate T killer cells and B cells, and B cells divide and differentiate to form plasma cells and B memory cells.
• Bactericidal antibiotic kills the bacteria, while bacteriostatic antibiotic inhibits the division of bacteria.
• Hospitals reduce antibiotic resistance by having a code of practice and hand wash stations.
• Bacteria have circular DNA, whereas viruses have linear DNA.
• Bacteria have plasmid DNA, whereas viruses have no plasmid DNA.
• Educating patients about taking a full course of antibiotics is a crucial aspect of antibiotic therapy.
• Vaccination activates the primary immune response, resulting in the production of B memory cells.
• HIV can escape the immune response or vaccination through a change in the sequence of nucleotides resulting in a change in the sequence of amino acids, resulting in a new antigen that is not recognised by B memory cells.
• Gel electrophoresis involves loading DNA onto an agarose gel, applying an electric current, and separating DNA strands based on size.
• Bacteria have 70S ribosomes, whereas viruses have no ribosomes.
• Increased washing of beddings is a preventive measure against the spread of antibiotic-resistant bacteria.
• Prescribing antibiotics with care involves not giving antibiotics if not necessary, not using antibiotics for prophylaxis, and rotating the use of antibiotics.
• HIV can result in opportunistic disease through destruction of T helper cells, fewer cytokines being released, and fewer B cells dividing and differentiating into plasma cells.
• HIV can result in bursting of T helper cells through reverse transcriptase using viral RNA to form viral DNA, integrase integrating viral DNA into T helper cell’s DNA, and viral particles forming and the T helper cell bursting.
• On infection or second exposure, B memory cells differentiate into plasma cells to produce antibodies.
• Bacteria have DNA, whereas viruses have DNA or RNA.
• HIV enters a T helper cell through Gp120 binding to CD4 receptor on T helper cell membrane, viral envelope fusing with the T helper cell membrane, and viral RNA entering the host cell.
• Vaccination involves putting a dead or attenuated pathogen into a person, which is a form of artificial active immunity.
• Polymerase chain reaction (PCR) involves heating DNA to separate the two strands of DNA (90-98oC), binding primer to the complementary bases on DNA at the either end (50-65oC), lining up DNA nucleotides along the DNA strands through complementary base pairing (70-75oC), and catalysing the formation of phosphodiester bonds between adjacent nucleotides (70-75oC).
• Screening involves testing patients for the presence of antibiotic-resistant bacteria before admission, followed by isolation of infected patients.
• Secondary immune response is not possible and a new primary immune response is needed.
• DNA replication involves the separation of the two strands of DNA by DNA helicase, the lining up of DNA nucleotides along the DNA strands through complementary base pairing, and the formation of phosphodiester bonds between adjacent DNA nucleotides.
• DNA replication is semiconservative.
• Transcription involves the separation of the two strands of DNA by DNA helicase, the lining up of RNA nucleotides along one DNA strand (the template/antisense strand) through complementary base pairing, and the formation of phosphodiester bonds between adjacent RNA nucleotides.
• Transcription is semiconservative.
• Polymerase chain reaction (PCR) involves heating DNA to separate the two strands, primer annealing, DNA nucleotides lining up along the DNA strands through complementary base pairing, and DNA polymerase catalysing the formation of phosphodiester bonds between adjacent nucleotides.
• Gel electrophoresis involves loading DNA onto an agarose gel, applying an electric current, and using dye, fluorescent tag, or UV to visualise bands.
• Splicing is the processing of pre-messenger RNA (pre-mRNA) to messenger RNA (mRNA), which includes the removal of introns (intruders, non-coding regions) and the splicing together of exons (coding regions).
• Alternative splicing is a process where different exons can be removed from pre-messenger RNA (pre-mRNA), resulting in different messenger RNAs (mRNAs) with different sequence of nucleotides, and therefore, different proteins with a different sequence of amino acids.
• Estimating time of death can involve changes in body temperature, rigor mortis, degree of decomposition, and forensic entomology.