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Year 12 Biology > Topic 7 > Flashcards

Topic 7 Flashcards

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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.
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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)
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3
Q

MHC Class 1 marker

A

found on all cells (apart from red blood cell)

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4
Q

MHC Class 2 marker

A

found on antigen presenting cells

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5
Q

Antigen presenting cells

A

cells that process foreign antigens, placing them on their cell membrane to other immune cells- stimulates immune response

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6
Q

disease

A

any condition that impairs normal activity of an organism

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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
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8
Q

virulence`

A

the degree to which a pathogen can cause disease

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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

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10
Q

types of non-cellular pathogens

A
  • prions

- viruses

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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
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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
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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
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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
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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.
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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
Q

oxygen requirement

A

requires oxygen
with or without oxygen- facultative anaerobe
must not have oxygen- obligate anaerobe

26
Q

gram stain differences

A

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
Q

exotoxin properties

A
  • 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
Q

endotoxin properties

A
  • 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
Q

fungi

A

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
Q

protozoan

A
  • unicellular eukaryotic organisms
  • absorb nutrients from host
  • reproduce both sexually/ asexually outside or inside the cell
31
Q

Macro-parasites

A
  • 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
Q

how does immune system detect all pathogens

A
  • 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
Q

allergens as non-self antigens

A
  • 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
Q

ways of avoiding immune system

A 
antigenic variation
shedding antigens
antigenic mimicry
protection from antibodies
attacking immune system
normal immune response doesn't occur in dying tissue

Year 12 Biology (16 decks)

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