Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
28 Cards in this Set
- Front
- Back
|
Core of nucleic acid |
Either DNA/RNA (RNA for HIV) |
|
|
Similarities between bacteria & viruses (3 marks) |
1) no nucleus 2) contain nitrogenous bases, amino acids, proteins 3) cause infection 4) seen using a microscope |
|
|
Differences between bacteria & viruses (3 marks) |
1) glycoprotein/ peptidoglycan cell wall (bacteria) vs envelope surrounding viral particle taken from host cell 2) cell membrane, made of phospholipids (bacteria) vs capsid made of viral proteins around core of nucleic acid 3) larger (bacteria) smaller (virus) 4) contain double stranded DNA (bacteria) contain single stranded DNA/ RNA (virus) 5) ribosomes present (bacteria) no ribosomes present (virus) |
|
|
What is a virus |
Infective agent consisting of a nucleic acid surrounded by a protein coat |
|
|
Size of a virus |
Tiny/small (E.g. HIV is 0.1 micrometer) |
|
|
Features of a virus |
- capsid - envelope - attachment proteins - proteins - core of nucleic acid |
|
|
Capsid |
Protein coat around the core |
|
|
Envelope |
Extra outer layer (cell membrane > same lipids & proteins)stolen from host cell |
|
|
Attachment proteins |
Stick out from edge of capsid/envelope > allow virus to bind to host cell |
|
|
Unlike bacteria, virus don’t have |
cell membrane, cytoplasm, ribosomes, mesosomes, cell wall, plasmids, flagellum, pilli capsule (3/ more = pass 😊) |
|
|
What are bacteria |
Single celled, prokaryotic, microbes (with no nucleus) |
|
|
What is the size of bacteria |
A few micrometers e.g. TB is 1 micrometer |
|
|
Features of a bacterial cell |
- ribosomes - mesosomes - cell wall - flagellum - cell membrane - pili - free floating DNA - plasmid - capsule
|
|
|
How is HIV spread? |
Through... - mixing of bodily fluids (vaginal secretions & semen NOT saliva/urine) - sexual intercourse (unprotected) - injected into bloodstream (sharing needles) - mixing of blood (cuts) |
|
|
Why do viruses need a host cell |
• provides nucleotides for making viral nucleic acids > RNA/DNA • provides organelles for making viral proteins > capsid layer |
|
|
General viral infection stages |
1) ATTACHES to host cell (Attachment proteins on virus to receptors on host cell) 2) INSERTS nucleic acid 3) REPLICATES (nucleic acid) 4) viral PROTEIN COATS synthesised (by host) 5) ^ viral PARTICLES FORMED 6) lysis of cell > virus RELEASED (buds off) |
|
|
HIV symptoms |
1) acute: fever, extreme fatigue, swollen lymph nodes, infection of mucous membranes 2) chronic: mostly asymptomatic (20 yrs), infections e.g. TB may occur due to weakened immune system 3) disease: no functional immune system, severe opportunistic infections e.g. toxoplasmosis, pneumonia, dementia > death |
|
|
Process of HIV replication |
1) attachment proteins (glycoproteins/gp120) bind to the CD4 receptor on T Helper cell 2) virus envelope fuses with T helper cell membrane > insertion of capsid > uncoats & releases genetic material/RNA into cytoplasm of host cell 3) reverse transcriptase used to make complementary strand of DNA from viral RNA template 4) double stranded DNA made & inserted into human DNA (using integrase) 5) Host cell enzymes used to make viral proteins from viral DNA (> protein coat forms) 6) viral proteins assembled to form new viruses, which bud from cell & go infect other cells |
|
|
Disease phase (AIDS) |
- deteriorates > no functional immune system (as T helper cell count extremely low (<200)) - severe ‘opportunistic’ infections e.g. pneumonia, dementia, toxoplasmosis > death - NOT AIDS killing individual but OTHER infections |
|
|
What causes Tubercolosis |
- Mycobacterium tuberculosis causes TB (write in italics) - rod shaped bacteria |
|
|
What causes TB infection |
When tiny air droplets containing bacteria are inhaled into lungs (respiratory disease as respires aerobically) |
|
|
Process of TB infection |
1. Inhalation of mycobacterium tuberculosis > lungs 2. Phagocytosis > phagocyte engulfs bacteria > survives & replicates in phagocyte 3. Dormant > no obvious symptoms as immune system seals these in tubercles 4. Dormant bacteria reactivated > overcome immune system causing TB (weakened immune systems) |
|
|
Symptoms of TB |
PRIMARY infection of TB is asymptomatic > Tb dormant due to tubercles formed ACTIVE TB 1) initial symptoms > fever, EXTREME fatigue, PERSISTENT cough > caused by inflammation of lungs 2) as TB progresses damages lungs > respiratory failure > death 3) effects other parts of body supplied with oxygen (when it spreads) > brain, kidneys, > organ failure > death |
|
|
What is the evolutionary race? |
evolutionary race = speed of evolution of pathogen competing against destruction by the immune system (& creation of antibiotics) |
|
|
HIVs evasion mechanisms |
1) kills immune system cells it infects > reduces overall no. > so reduces chance of HIV detection 2) antigenic variation > ^ rate of mutation in genes coding for antigen > new strains > x recognise ‘new’ antigen (glycoproteins) 3) disrupts antigen presentation in infected cells > immune system x recognise & kill pathogen |
|
|
Mycobacterium tuberculosis evasion mechanisms |
1) when engulfed by phagocyte produce substances preventing lysosome fusing with phagocytic vacuole > x broken down > multiply undetected in phagocyte 2) disrupts antigen presentation in infected cells > immune system x recognise & kill infected phagocytes 3) thick waxy cell walls > difficult to break down |
|
|
Relevance of pathogens (What do they do? What are they? What do they lead to?) |
• cause infectious diseases • e.g. bacteria, fungi, viruses • develops into a sequence of symptoms (e.g. in TB & HIV) |
|
|
Why do bacterial population evolve very quickly? |
random mutations advantageous to the cell containing them > successfully reproduce + less competition > ^ survival (+quickly reproduce & large population sizes) |
