Topic 7 Flashcards
1
Q
antigens
A
compounds foreign to the body that trigger an immune response
- may be molecule or part of a molecule
- surface of pathogen may have several different antigens/epitopes
- if antigen gains entry into persons internal environment, immune system recognises them as foreign and immune response initiated.
2
Q
distinguishing self from non-self
A
- cells and molecules are identified as self antigens by our immune system- therefore not destroyed by our immune cells-by protein markers on the cell
- these protein markers are expressed due to information contained in DNA-unique in everybody
- foreign antigens are recognized by specific receptors on our immune cells as non-self and bind to these receptors- triggers an immune response through cascade of events
- group of genes that determines these protein markers is called MHC (major histocompatibility complex)
3
Q
MHC Class 1 marker
A
found on all cells (apart from red blood cell)
4
Q
MHC Class 2 marker
A
found on antigen presenting cells
5
Q
Antigen presenting cells
A
cells that process foreign antigens, placing them on their cell membrane to other immune cells- stimulates immune response
6
Q
disease
A
any condition that impairs normal activity of an organism
7
Q
what causes disease symptoms
A
physical or chemical damage to host
- inadequate supply of food and nutrients to a host
- symptoms don’t appear immediately- time between infection and symptom onset- incubation period
8
Q
virulence`
A
the degree to which a pathogen can cause disease
9
Q
entry points for a pathogen
A
nose and throat to lungs
mouth into digestive system
urethra or genital opening
cut, punctures, burns, insect bites that penetrate skin
10
Q
types of non-cellular pathogens
A
- prions
- viruses
11
Q
prions
A
- do not contain any genetic material
- consist of PrP protein, smaller than viruses
- two forms:
- PrPc- found naturally in nerve cells and plays role in memory, learning and transmission of signals between cells
- PrPsc- disease causing form, usually enters body through infected meat- causes nervous system degeneration
- very resistant to high temperatures, UV radiation and strong enzymes- difficult for immune system to combat
12
Q
prion reproduction
A
- PrPc can be transformed to harmful PrPsc prion by contact with harmful prion
- contact causes PrPc to unfold and refold abnormally- secondary structure is converted to that of harmful PrPsc prion
- each transformed prion can then make contact with other normal prions, transforming them into abnormal prions- sets up chain reaction that rapidly multiplies numbers of harmful prions
- not true biological reproduction
13
Q
Viruses
A
- non-cellular pathogens
- can only replicate inside living cell- obligate intra-cellular parasites
- usually host specific- will only cause disease in one kind or organism as they recognise specific surface molecules on cell membrane of specific host
- either contain DNA or RNA surrounded by protein coat (capsid)- naked viruses
- in some, the nucleocapsid is surrounded by an envelope- outer envelope may have glycoprotein spikes- act as recognition and attachment to specific host
14
Q
structure of retrovirus
A
- composed of RNA
- contains reverse transcriptase enzyme- allows virus RNA to be transcribed into DNA after entering host cell.
- retroviral DNA can then integrate with host cell’s chromosomal DNA- then is expressed
15
Q
reproduction of viruses
A
- host cells have specific receptor sites which allow only specific viruses to bind to them- virus can only replicate inside suitable host cell
- host cell infected with virus becomes factory- produces multiple copies of the virus
- mode of release of viral particles from infected cell- lysis or budding
- enveloped viruses- released from infected cell by budding- virions are released until infected cell dies
- naked viruses commonly released by lysis- infected host cell explodes and plasma membrane disintegrates
- viral particles released into extracellular fluid- allows them to infect other cells.
16
Q
process of budding
A
- virus becomes attached to target cell
- cell engulfs virus by endocytosis
- viral contents are released
- viral RNA enters nucleus where it is replicated by viral RNA polymerase
- viral mRNA is used to make viral proteins
- new viral particles are made and released into extracellular fluid by exocytosis
- cell is not killed in process, and continues to make new virus.
17
Q
process of lysis
A
- virus attaches to target cell
- virus penetrates cell membrane-injects DNA/RNA into cell
- viral nucleic acid replicates using host cell machinery
- new viral DNA/RNA are packaged into viral particles
- the cell continues to make and package new viral particles until it swells-membrane bursts and viral particles are released into extracellular fluid.
18
Q
retrovirus process
A
- virus binds to specific receptors on host cell
- viral RNA, reverse transcriptase, integrase and other viral proteins enter host cell
- viral RNA is reversed transcribed to make viral DNA
- viral DNA enters nucleus and integrates into host cells DNA
- host cell DNA with viral DNA is transcribed and translated- creating new viral proteins
- viral RNA and proteins are packaged and assemble at cell membrane
- viral particles are released via exocytosis
19
Q
how do viruses cause cancer
A
- viruses that cause cancer are lysogenic
- viral DNA incorporates into hosts DNA and is inactive.
- viral DNA is copied when DNA replication of cell occurs
- passed to new cell during mitosis
- viral DNA can be activated, often when cell is stressed
- site of incorporation into host- may result in some cells becoming cancerous
20
Q
bacteria
A
single-celled prokaryotic- DNA
- can live, reproduce and cause disease in organisms
- reproduce by binary fission
- can either live and reproduce inside or outside cell
- has cell wall made of peptidoglycan
21
Q
characteristics present in all bacteria
A
DNA, cell wall, plasma membrane, cytoplasm, ribosomes
22
Q
characteristics present in some bacteria
A
capsule, pilus, plasmid, flagellum
23
Q
shape characteristics of bacteria
A
round- coccus
rod-like- bacillus
spiral- spirochaete
24
Q
organisation characteristics of bacteria
A
single
in pairs- diplo
in chains- strepto
clustered- staphylo
25
oxygen requirement
requires oxygen
with or without oxygen- facultative anaerobe
must not have oxygen- obligate anaerobe
26
gram stain differences
gram positive- thick peptidoglycan (disaccharide and amino acid) cross linked layer+ techoic acid (polysaccharide)
-when treated with gram stain, they turn violet
-penicillin, sulfonamide are effective antibiotics
gram negative- thin peptidoglycan+ lipid
-when treated with gram stain, they remain pink
-resistant to penicillin, effective antibiotics include streptomycin and tetracycline
-phagocytosis by WBC difficult
27
exotoxin properties
- proteins produced by gram positive bacteria
- released as part of normal bacterial growth+metabolism
- most toxic compounds known
- can easily diffuse into circulatory system
- can be destroyed by heat
- small dose causes symptoms in infected person
28
endotoxin properties
- part of cell wall of gram- negative bacteria
- lipids and only take affect when bacteria die
- less toxic than exotoxins, but are heat resistant
- does to produce symptoms is high, but immune system can't produce antitoxins against them
29
fungi
single/multi-cellular prokaryotic organisms
-secrete digestive enzymes to break down organic matter
-secreted substance causes the disease
have cell wall made of chitin and will grow on any organic matter with suitable temperature and moisture
30
protozoan
- unicellular eukaryotic organisms
- absorb nutrients from host
- reproduce both sexually/ asexually outside or inside the cell
31
Macro-parasites
- worms are endo/macro parasites
- once inside- use organisms resources to live and reproduce- causing disease to host
- arthropods are invertebrates with external skeletons
- cause disease by biting their hosts
32
how does immune system detect all pathogens
- all have either surface molecules made of glycoproteins or polysaccharides- or they produce toxins and other secretions
- these act as non-self antigens to trigger body's immune system
33
allergens as non-self antigens
- antigens that cause allergic reactions-allergens
- specific type of immune response which immune system overreacts to normally harmless substance
- can produce minor symptoms or life threatening anaphylaxis
34
ways of avoiding immune system
```
antigenic variation
shedding antigens
antigenic mimicry
protection from antibodies
attacking immune system
normal immune response doesn't occur in dying tissue
```
