Topic 6 - Immunity, Infection And Forensics Flashcards
What is the structure of bacteria and what dont they have?
Same structure as prokaryotes, dont have membrane bound structures or nucleus and they dont produce spindles during cell division.
Why do viruses have to enter host cells?
They lack the internal structures required for growth and reproduction so use host cell’s metabolic systems to make more viruses.
What are the 3 components of a virus?
- Protein coat= contains proteins to help virus infect cells and some have them in their cell membranes.
- Viral genetic material = either DNA or RNA, contains instructions for viral proteins.
- Viral enzymes= help establish infection.
What is the virus life cycle? (4)
- Virus binds to surface of host cell.
- Viral genetic material enters host cell.
- Viral nuclei acids replicate and protein coats are synthesised so new viral proteins are particles are made.
- Viral particles burst out of cell splitting it open and killing it. This is called lysis.
What is tuberculosis?
A contagious disease caused by mycobacterium tuberculosis.
What are the 2 phases of TB?
- Primary phase= where immune system responds well or can be evaded.
- Active TB = where immune system cannot contain disease or is failing.
What are the 4 steps of effective immune response to TB?
- M. Tuberculosis causes inflammatory response in lungs.
- Macrophage engulfs bacteria by phagocytosis.
- Mass of tissue called a granuloma forms to deal with infection.
- Centre of granuloma is anaerobic as M. Tuberculosis is an obligate aerobe so dies.
What are the 2 types of immune response?
Specific and non-specific.
What are the 4 types of non specific immune responses?
- Fever
- Inflammation
- Interferon
- Phagocytosis.
What are phagocytes?
White blood cells that include: neutrophils, macrophages and lymphocytes (T and B cells)
What are the 4 steps of phagocytosis?
- Chemicals released by the pathogen or body e.g histamines, attract phagocytes.
- Neutrophils or macrophages bind to pathogen and membrane moves to form pseudopodia.
- Pseudopodia join and engulf pathogen by endocytosis which forms a phagosome, like a vesicle, around the pathogen.
- Phagosome fuses with lysosome which releases enzymes that digest pathogen into peptides.
What are antigens?
Antigens are markers on the surface of cells that are detected by the immune system.
What are the 3 steps of antigen display?
- The peptides from the pathogen inside the phagocyte bind to MHC proteins.
- MHC-peptide complexes move to the cell’s surface.
- The phagocyte becomes an antigen presenting cell.
What comes first in the specific immune response?
The activation of t helper cells.
What are the 4 steps for T-helper cell activation?
- APC is recognised by T-helper cell with complementary CD4 receptor for antigen.
- T-helper cell binds to the antigen which activated the T-helper cell.
- T-helper cell divides by mitosis into 2 genetically identical daughter cells with the same CD4 receptor.
- As they divide by mitosis, the T-helper cells differentiate into active T helper cells and memory T helper cells which circulate the blood and enable faster specific immune response if pathogen is encountered again.
What are the 5 steps of B cell activation?
- B cell with complementary receptor recognises and binds to pathogen’s antigen.
- B cell engulfs pathogen by phagocytosis and becomes and antigen presenting cell.
- Active T helper cells with complementary CD4 receptors bind to antigen.
- Active T helper cells release cytokines which activate and stimulate B cells to divide by mitosis and differentiate into memory B cells and B-effector cells.
- The B-effector cells further differentiate into plasma cells which produce antibodies.
What holds together the polypeptide chains in antibodies?
Disulphide bonds
What 3 things can antibodies do in the immune response?
- Antibodies can bind to pathogens and mark them for phagocytosis.
- Agglutination= antibody binding causes pathogens to clump together which makes phagocytosis easier.
- Blocking= antibodies can bind to the antigens on viral proteins which prevents them from binding to target cells.
What is the activation of T killer cells also called?
The cell mediated response
What are the 5 steps of T-killer cell activation?
- Infected body cell displays pathogen antigens on surface.
- T-killer cell with complementary receptor binds to antigen.
- T helper cell with the same receptor releases cytokines which activate the T killer cell.
- Activated T-killer cell divides by mitosis and differentiates into memory T killer cells and Active T killer cells.
- Active T killer cells bind to infected cells and release chemicals that cause pores to form which causes lysis and infected cell dies.
What are the 3 unique features of the HIV virion?
- GP120= glycoprotein that binds to CD4 receptors on T-helper cells
- Reverse transcriptase= enzyme that converts single stranded RNA genome into double strand DNA molecule.
- Integrase= takes viral DNA and integrates it into host gene.
What is splicing?
The removal of introns from DNA.
What are introns and exons?
Introns= the parts that separate exons, non-coding DNA
Exons= contain the information to be translated into proteins
What are the 2 steps of splicing?
- Transcription takes place and produces pre-mRNA which still has introns.
- Splicing occurs which produces mature mRNA which only contains exons.
What type of splicing means that several different proteins can be formed from one length of mRNA?
Alternative splicing
What is alternative splicing?
This is where different combinations of exons can be removed or retained to produce a different amino acid sequence resulting in a different protein and contributes to genetic variation
What is the treatment for HIV and how do they work?
Anti-retroviral drugs. They work by inhibiting the life cycle of HIV by inhibiting reverse transcriptase, integrase and viral protease.
What is the treatment for TB?
Antibiotics.
What are the 2 different types of antibiotics?
Bacteriacidal and bacteriostatic
What do bacteriacidal antibiotics do and how?
They directly kill the bacteria. By inhibiting cell wall synthesis which weakens the cell wall so when it tries to divide, the cell bursts and dies.
What do bacteriostatic antibiotics do and how?
They stop bacteria from growing to buy time for the immune response. They do this by inhibiting transcription, DNA replication and translation so the cell stops dividing but doesnt die.
What are the 2 versions of the evolutionary race?
- Selection pressures from pathogen drives natural selection in hosts e.g CF causing alleles protect against cholera.
- Selection pressures from host responses drive natural selection in pathogens. E.g variation of spike protein on coronavirus to evade immune response.
How is immunity developed (3)?
- New antigen is encountered which launches primary immune response.
- Primary immune response consists of non-specific and specific responses. This takes several days to activate T-helper, T-killer and B-cells so symptoms occur.
- If the same pathogen is encountered again, the secondary immune response takes place which uses memory cells and antibodies so is rapid and no symptoms occur.
What are the 4 different types of immunity?
- Active natural
- Active artificial
- Passive natural
- Passive artificial
What is active immunity and what are the 2 types?
Active immunity is where an antigen enters the body and triggers the immune response.
Natural= being exposed to the pathogen
Artificial= through vaccination
What is passive immunity and the 2 types?
Passive immunity is acquired without the immune response where antibodies are gained from another source.
Natural= antibodies passed across placenta from mother or from breastfeeding.
Artificial= through injection or transfusion of antibodies.
No memory cells are present as immune response was not activated.
