Component 3 - Topic 3.3 - Immunology & Disease (COMPLETED) Flashcards
(17 cards)
a) Why are viruses described as being ‘INERT’? In their INERT state, viruses are simply called a collection of WHAT?
b) There are two types of ways viruses can replicte. Explain the 5 step process of the LYTIC CYCLE.
1. Attachment
2. PENETRATION
3. BIOSYNTHESIS
4. ASSEMBLY
5. LYSIS
a) Outside of a host organism, viruses are described as being INERT. This is because they’re UNABLE to sustain their ownselves. They are INACTIVE.
They are simply called a collection of GENETIC MATERIAL in their INERT stage.
b)
1. The virus INFECTS the host cell. It does this by attaching to certain RECEPTORS on the surface of the host cell membrane. This is called ATTACHMENT.
- The virus or its genetic material ENTER the host cell. This entry is subsequent to the fusion of the both cell membranes via ENDO-CYTOSIS (the host cell engulfs the virus). This is called PENETRATION
- Once the virus is inside the cell, the viral genome (either DNA or RNA) takes control of the host cell’s machinery. The cell begins to produce new viral components (new viral genomes and protiens using the resources of the host cell). This is the biosynthesis phase
- The newly made components are assembled into complete viral particles (Virons) inside the host cell. This is the assembly phase.
- Once a sufficient number of new viruses are produced, the host cell BURSTS (lyses), releasing these new viruses into the surrounding environment. Those viruses then go and infect other neighbouring cells. This is the lysis and release phase.
a) The second method of replication is called the lysogenic cycle. What is one of the main differences between the two methods of replication? Explain the LYSOGENIC cycle (step-by-step).
a) They integrate their nucleic acid into the host cell genome and may remain there for many cell generations with no clinical effect. They enter the lytic cycle at a later point in time.
- The LYSOGENIC cycle begins like the lytic cycle in which the virus binds to specific receptors found on the surface of the host cell. This is the attachment phase.
- The viral genome (DNA or RNA) enters the host cell, but instead of immediately hijacking the host cell’s machinery, the viral DNA is integrated into the host cell’s DNA and becomes an integral part of the host cell’s chromosome. This is the penetration phase.
- When the host cell undergoes mitosis (Cell division/replication). The host cell replicates its own DNA (as we know during DNA synthesis - S-phase). As a result, the viral integrated DNA is then passed on to the daughter cells produced. The key point to note is that the virus is still DORMANT (i.e. it’s essentially in ‘deep sleep’).
4.Under certain conditions, the viral DNA can exit the host’s genome and enter the lytic cycle immediately. This is the induction phase.
a) Can you explain why bacterial cells burst when infected by bacteria? Furthermore, explain what happens in an animal cell. There’s a difference. Why does inflammation occur as a result of t-lymphocyte response? What is apoptosis? Who do t-lymphocyte cells directly attack?
b) How can the insertation of viral DNA lead to cancer? Induce cancer?
a) When the bacteria are infected by a virus, the pressure of the newly synthesised virus particles inside causes the bacteria to BURST. By contrast, in virus-infected animal cells, it’s the inflammation caused by the T-lymphocytes or antibodies that brings about cell lysis.
Essentially, it’s your body’s immune response. T-lymphocytes are a type of t-cell that directly attack infected or cancerous cells. When they recognise foreign antigens present on the surface of an infected cell’s surface, the t-lymphocytes release toxic substances which induce apoptosis (induced cell death or lysis).
b) If the viral DNA goes through the lysogenic cycle and the viral DNA integrates into the pro-oncogene
The viral DNA can insert itself near or within the proto-oncogene. This can lead to it being overexpressed, leading to excessive production of the protein it encodes. This can drive unchecked cell growth & division. Or simply, viral DNA integration can just activate it and lead to uncontrolled cell growth. It becomes cancerous.
Antibiotics - Their types:
a) What are compounds that kill bacteria instantly called? Beneath them you’ll find antibiotics. What are antibiotics? What are broad and narrow spec. antibiotics?
b) Different antibiotics impact various parts of the bacterial metabolism. What are the two classifications?
a) Compounds that inhibit the growth or immediatley kill bacteria are called antimicrobials. Antibiotics are a type of antimicrobial - they’re a substance produced by microorganims which delay the growth of, or kills, other microorganisms, especially bacteria but NOT viruses or eukaryotic cells. Thus, they can treat BACTERIAL infections without inducing any harm to the patient.
b) Broad spec. antibiotics kill a variety of gram +VE and -VE bacteria while Narrow spec. antibiotics are more selective. Different antibiotics impact various parts of the bacterial metabolism. There are two classifications of antibiotics.
1. BACTERICIDAL = antibiotics that KILL bacteria (penecillin destroys the cell wall)
2. BACTERIOSTATIC = antibiotics that prevent bactrial multiplication - but don’t cause death. Protein synthesis can be inhibited. Once the antibiotics are no longer present they resume division.
We shall now look at the structure of the cell walls of bacteria and then we shall look at how 2 different antibiotics have various mechanisms which destroy the cell wall.
a) Murein is also called peptidoglycan. It contian a WHAT layer and WHAT short chains (made of monomers joined by peptide bonds). An enzyme called WHAT is responsible for the formation of side chains of these monomers between the layers of __________. Why is this cross-linking so important osmotically?
a) Peptidoglycan forms a part of the bacterial cell wall. It contains polysaccharide and short chain amino acids (short polypeptide chains). There is an enzyme called transpeptidase, its job is to form side chains of amino acids cross-linking the layers of polysaccharide. This cross-linkage provides great strength to the cell wall. It helps with the resistance of cell lysis due to the osmotic uptake of water.
a) What % of Gram +VE bacteria is murein? What closes during the decolourisation stage that causes the WHAT stain to remain/retain? Why are Gram +VE bacteria sucesptible to antimicrobial agents such as penecillin?
a) What % or Gram -VE bacteria is murein? What is the murein layer surrounded by? Why are Gram -VE bacteria safe from antimicrobial agents such as penecillin?
a) 90% is MUREIN! Pores in the murien layer of Gram +VE bacteria CLOSE during decolourisation stage of the gram stain protocol, thus, crystal violet colour is retained. The peptidoglycan layer is accessible to molecules OUTSIDE the cell, making it susceptible to attack by lysozyme and penicillin - we shall see next what both of these do. Gram +VE bacteria have 90% murein layer.
b) The cell walls of the gram -VE bacteria have a thin layer of murein, no more than 10%. This murein layer is surrounded by a layer of lipoprotien and lipopolysaccharide, These lipid containing molecules are disrupted by the decolourisation stage or the gram staining protocol and as a result the crystal violet stain leaks OUT. Safranin, the counter-stain turns it RED. The lipid-containing layer protects the murien layer from antimicrobial agents such as antibiotic, penecillin.
a) Why does penecillin NOT impact humans?
a) Penecillin impacts the murein layer in the cell walls of bacteria. Humans DO NOT have a peptidoglycan layer or cell wall and so penecillin does NOT impact humans.
The ROLE of the antimicrobial, PENECILLIN.
a) The enzyme is essentially a catalyst that boosts WHAT reaction that does what to form WHAT?
b) Hydrolysis occurs and its broken down as a result. This is because bacteria continually make and break parts of the cell wall. If more is being broken than made then this can cause the bacteria to become sucepitble to lysis due to ________ pressure. Furthermore, as there is a lack of ________ linkages between _____________ layers, the cell wall is further weakened. Water can enter via ________. Therefore, this antibiotic is an example of a ____________ antibiotic.
a) The enzyme DD-transpeptidase is the ‘catalyst’ that boosts condensation reactions making cross-links between amino acid side chains joining peptidoglycan molecules and water. Penecillin binds to it acting as an inhibitor to the catalysts functions.
b) Hydrolysis occurs and its broken down as a result. This is because bacteria continually make and break parts of the cell wall. If more is being broken than made then this can cause the bacteria to become sucepitble to lysis due to osmotic pressure. Furthermore, as there is a lack of peptide linkages between polysaccharides, the cell wall is further weakened. Water can enter via osmosis. Therefore this antibiotic is an example of a bacteriocidal antimicrobial.
The ROLE of the antimicrobial, Tetracycline:
a) It’s a ______ spectrum antibiotic impacting most Gram +VE and Gram -VE bacteria and so it has a wide medical use.
Tetracycline inhibits _______synthesis. It diffuses and is pumped into bacteria cells. It binds to the small ___ subunit of the ribosome blocking the attachment of the tRNA to the __nd position. As a result NO new amino acids can be added to a polypeptide chain. This is reversible however, therefore, tetra cycline is a ______________ antimicrobial.
a) It’s a broad spectrum antibiotic impacting most Gram +VE and Gram -VE bacteria and so it has a wide medical use.
Tetracycline inhibits protein synthesis. It diffuses and is pumped into bacteria cells. It binds to the small 30s subunit of the ribosome blocking the attachment of the tRNA to the 2nd position. As a result No new amino acids can be added to a polypeptide chain. This is reversible however, therefore, tetra cycline is bacteriostatic.
a) What is antibiotic resistance and how does it conincide with selective advantage.
a) Antibiotic resistance - any individuals who have a mutation that enables them to resist the effects of antibiotics shall survive. The have a selective advantage and can therefore pass on their successful allele that enables the antibiotic resistance. This builds up protection/resistance in subsequent generations…
a) What are the two sources of anitbiotic resisance? Explain BOTH…
a) There are two SOURCES of antibiotic resistant alleles.
1. Every time bacterial DNA replicate, a mutation conferring resistance arises. Bacteria divide rapidly when conditions are suitable and so the mutation rate rises.
2. Bacteria may aquire the plasmids that carry an allele conferring resistance from their environment. The plasmids replicate inside the bacterium and are passed on to the daugther cells during division.
The mutated DNA codes for proteins that prevent antibiotics from working in ways that depend on the mechanism of the antibiotic. For example, there is a protein/enzyme that degrades penecillin preventing it from inhibiting the enzyme that catalyses the condensation rection that forms the peptide cross-links between polysaccharide.
THE IMMUNE RESPONSE:
The immune system enables the body to ______ disease. There are ______ barriers and there are _______ & _______ barriers of which kick in if the _______barriers fail. What is the body’s task? i.e what does it have to distinguish between in order to relay an immune response? It has to detect WHAT essentially from WHAT?
a) The immune system enables the body to resist disease. There are physical barriers and there are cellular and chemical barriers if the physical barriers fail. The body has the task of distinguishing between foreign antigens from ‘self’ antigens in its own tissues.
a) The first of the 7 features that make up the innate immune system is the largest organ of the body, which is the WHAT. This organ has 3 layers, within the first layer there are cells called ________ which produce keratin which is responsible for the skin being WHAT? Furthermore, the middle layer called the ______is home to a connective tissue called ________ which is responsible for the skin being WHAT?
b) The skin comprises many microbiota (________ or _________ bacteria that are found on all multicellular organisms). These microbiota are helpful in the sense that they _________ pathogenic strains. When we say they ________, we mean that the microbiota leave ___ resources that enable the pathogen to ___ on the surface. Furthermore, some microbiota ________ __________ that can disrupt the cell membranes of harmful bacteria and can inhibit their __________ capabilities.
c) The _______ in our nose and trachea TRAP any harmful _______ coming in from the surrounding air. The ________ _________ _______ then, through _______ rhythm, wafts the collection up to the opening of the __________, where they’re swallowed and the stomach’s ______ deals with them.
- The skin is the largest organ covering all external surfaces of the body, except at vital openings including the eyes and mouth. Our skin is WATERPROOF due to the keratin which is produced by the epidermal cell keratinocytes (cells of the epidermis). Collagen is a connective tissue of the dermis (i.e the area sandwiched between the epidermis and the hypodermis, which is the region at the bottom of the skin layer). Collagen makes the skin TOUGH.
- The skin comprises many microbiota (commensal or mutualistic bacteria found on all multicellular organisms). These microbiota are helpful in the sense that they outcompete pathogenic strains. When we say they outcompete, we mean that the microbiota leave few resources that enable the pathogen to grow on the surface. Furthermore, some microbiota produce substances that can disrupt the cell membranes of harmful bacteria and can inhibit their reproductive capabilities.
- The mucus in our nose and trachea TRAP any harmful spores coming in from the surrounding air. The ciliated epithelial cell then, through tempantic rhythm, wafts the collection up to the opening of the oesophagus, where they’re swallowed and the stomach acid deals with them.
e) When the skin barrier is _________, e.g if the capillaries are _____, blood immediately begins to ______, preventing the _________ of harmful microbes. Furthermore, increased blood ____ occurs to the site of the ________. This brings more ________ cells. The broken capillaries heal and the body’s induced _____ (high temperature) kills off the microbes (fever is part of the body’s immune _______ system).
f) Tears, mucus and saliva ALL contain ________, an enzyme that _________ peptidoglycan molecules that are present in the bacterial ____ _____, and kills them.
e) When the skin barrier is breached, e.g if the capillaries are broken, blood immediately begins to CLOT, preventing the eneternace of harmful microbes. Furthermore, increased blood flow occurs to the site of the infection. This brings more phagocytic cells. The broken capillaries heal and the body’s induced fever (high temperature) kills off the microbes (fever is part of the body’s immune response system).
f) Tears, mucus and saliva ALL contain LYSOZYME, an enzyme that hydrolyses peptidoglycan molecules that are present in the bacterial cell wall, and kills them.
a) There are 2 components to this specific immune response. Give both names. In the first component WHAT is produced?
b) What are ANTIBODIES? What is their main purpose?
c) B-lymphocytes are the first to recognise the _______ antigen WHERE? They then do WHAT making both ______cells and _______cells. The first goes to producing
d) An antibody is called a glycoprotein. WHat is that? Furthermore, they have a WHAT protein structure? The polypeptide chains are held together by WHAT bond?
e) What is agglutination (essentially the opposite of anticoagulation)? Why does this occur? Think about the structure of an antigen…
a) The first is the humoral response. The second is the cell-mediated response. The humoral response (i.e the first response in the adaptive response) results in the production of antibodies.
b) Antibodies are immunoglobulins produced by the body’s immune system. These are specialised proteins produced by B-cells (a type of white blood cell). They essentially, “search and destroy” harmful invaders. The main purpose of an antibody is to recognise and bind to specific foreign particles or molecules (called antigens found on the surface of the foreign body).
c) The B-lymphocytes (B-cells) are the ones who first recognise the foreign body in the bloodstream. The B-lymphocytes then divide, making: plasma cells, which release antibodies (plasma cells are simply specialised B-cells) and B-cell also divide to produce”memory cells”, these remain dormant in the circulation and then divide to form more B lymphocytes if the same antigen is presented again in the future.
d) Antibodies are glycoprotein molecules (molecules that consist of both carbohydrate and protein molecules). They’re called immunoglobulins. They have a QUATERNARY STRUCTURE as each molecule is made of 4 polypeptide chains joined together. The polypeptide chains are all held together by di-sulfide chains.
e) Antibodies have variable proportions that are specific to each antigen. Antibodies have two binding sites and as a result they (pathogens) clump together this is called agglutination.
Active & Passive Immunity - ACTIVE IMMUNITY:
a) The body makes its own WHAT? How is this formed? It’s stimulated by either ____________ or ______________. It lasts longer WHY?
b) Vaccination - when you’re vaccinated, the _______________ and ___________ response kick into action despite there NOT being a harmful pathogen present. This is because a VACCINE is a ______________ or killed pathogen that’s introduced into your system so that your body can ________ an __________ response. This results in the formation of __________ cells! This is part of the active immunity group because the body is making its own ____________.
a) The body makes its own antibodies in ACTIVE immunity, stimulated by either infection or vaccination. It’s longer lasting due to the production of memory cells simultaneously.
b) Vaccination - when you’re vaccinated, the cell-mediated and humoral response kick into action despite there NOT being a harmful pathogen present. This is because a VACCINE is a weakened or killed pathogen that’s introduced into your system so that your body can INDUCE an immune response. This results in the formation of memory cells! This is part of the active immunity group because the body is making its own antibodies.
