Topic 2 last (start w immunity) Flashcards
(103 cards)
1
Q
What are the body’s two mechanisms of defense?
A
- Non specific (Immediate responses and the same for all pathogens E.G. physical barriers and phagocytosis)
- Specific (slower responses, specific to each pathogen involving lympocytes)
2
Q
How does the immune system distinguish between self and foreign?
A
- Each type of cell has specific molecules on its surface that identify it.
- However it is by the proteins on the surface which the immune system can recongnise if the cell is self or foreign.
3
Q
What is an antigen?
A
- A molecule/protein that triggers an immune response by lymphocytes
4
Q
What is a phagocyte?
A
- A type of white blood cell which carries out phagocytosis
5
Q
What is phagocytosis?
A
- The mechanism by which cells engluf particles to form vesicles that eventually destroy pathogens.
6
Q
Outline the process of phagocytosis..
A
1) Phagocyte is attracted to the pathogen
2) phagocyte attaches to chemicals on the surface of the pathogen by specific receptors
3) Phagocyte englufs pathogen and forms a phagosome
4) lysosome fuses with phagosome forming phagolysosome
5) Hydrolysis of the pathogen
6) Phagocyte presents its antigens on its cell surface membrane (APC)
7
Q
What are T lymphocytes?
A
- Bone marrow
- Mature in the Thymus gland
- Associated with the cellular response (cell-mediated)
8
Q
What are B lymphocytes
A
- Made in bone marrow like T
- Mature in the bone marrow
- Associated with the humoural response
9
Q
What is the cellular immune response?
A
- Immunity involving body cells that have antigens presented on their surface
10
Q
What is the humoural response?
A
- Involves antibodies that are present in body fluids
11
Q
Outline the cell mediated response…
A
- Pathogen invades body cell or are taken in by phagocytosis
- Invaded cell presents antigen on its surface membrane
- T helper cell binds to the antigen via a specific T-cell receptor
- This activates the T helper cell to rapidly divide by mitosis and form clones of this specific T helper cell (clonal selection)
12
Q
What is the role of cloned T helper cells?
A
- Can develop into memory cells that enable rapid response to future infections by the same pathogen
- Stimulate phagocytes to engulf pathogens by phagocytosis
- Stimulation of B cells to divide and secrete antibodies
- Activation of cytotoxic T cells.
13
Q
What are cytotoxic T cells?
A
- Cells that kill abnormal cells and body cells that are infected by pathogens
- Produce perforin, a type of protein, which makes holes in the cell membrane causing the cell to die as any substances enter it.
14
Q
What is an antibody?
A
- proteins produced by b lymphocytes in response to an antigen.
15
Q
How to antibodies bind to antigens?
A
- On the surface of pathogens to form an antibody-antigen complex.
16
Q
Outline the B cell response…
A
- B cell takes in antigens of a pathogen by endocytosis
- B cell processes antigens and presents them on its surface
- T helper cells attach to the processed antigens on the B cells and activate it.
- B cell divides by mitosis to provide a clone to form plasma cells
- Plasma cells produce and secrete the antibodies specific to the antigen on the pathogen’s surface.
- Antibodies attach to antigens on the surface of pathogens causing them to agglutinate, making it easier for phagocytes to locate and engulf them
- B cells develop into memory cells which can divide rapidly into plasma cells.
17
Q
What is the role of plasma cells?
A
- Secrete antibodies, usually in blood plasma and are involved in the primary immune response
18
Q
What is the role of memory cells?
A
- Involved in the secondary immune response
19
Q
Difference between primary response and secondary response?
A
- Secondary response is quicker than primary response
- Memory B cells are able to divide rapidly into plasma cells.
20
Q
What is vaccination?
A
- The introduction of dead/inactive pathogen to stimulate an immune response.
- Vaccine stimulate the production of memory cells to an antigen without producing harsh symptoms.
- So if the body is exposed to the same antigen, antiboides are produced rapidly.
21
Q
What is herd immunity?
A
- When a large population is immune to a disease, then the spread of that pathogen is significantly reduced.
22
Q
What is antigenic variability?
A
- Where the tertiary structure of antigens changes so the vaccine can no longer be effective against a particular disease.
- Pathogens mutate to have different antigens so it is no longer recognised by the immune system.
23
Q
What is active and passive immunity?
A
- Active immunity is the triggering of immune system by exposure to antigens
- Passive immunity is the introduction of antibodies from an outside source
24
Q
What is natural active?
A
- Infection and recovery
25
What is natural passive?
- Antibodies recieved from mother via breast milk or placenta
26
What is active artifical?
- Vaccination by a jab
27
What is passive artificial?
- Injection of antiserum containing antibodies
28
Differences between active and passive immunity?
- Active provides long term immunity but passive is short term immunity
- Active produces memory B cells but passive doesn't
- Passive is quicker
29
What is the role of a reverse transcriptase enzyme?
- An enzyme that catalyses the production of DNA from RNA.
30
How does HIV replication happen?
1) HIV binds to host T helper cell receptor via the attachment protein
2) Viral capsid and host cell membrane fuse and RNA and reverse transcriptase enters.
3) Reverse transcriptase makes DNA
4) Double stranded DNA is mad and inserted into host cell's DNA
5) Transcription into mRNA, making new proteins that are viral and then these are released and infect other areas.
31
Why is HIV a bad thing?
- Kills T helper cells leading to insufficient T helper cells
- Less T helper cells means less B cells can bind to their antigens to produce antibodies
- Memory cells are infected and destroyed
32
Why are antibiotics insufficient against viruses?
- Antibiotics target bacterial enzymes however viruses use human enzymes which are a different structure
- Viruses do not have sites where antibiotics can work
33
What are monoclonal antibodies?
- Antibodies produced from a single group of genetically identical B cells
34
Why are monoclonal antibodies specific?
- They have binding sites that are only complementary to one antigen
35
What are the uses of monoclonal antibodies?
E.G cancer cells
1) Monoclonal antibodies are produced which are specific to receptors on cancer cells
2) Antibodies attach to the surface of cancer cells and block chemical signals that stimulate uncontrolled growth.
(direct monoclonal antibody therapy)
36
Why are monoclonal antibodies so effective?
- Specific to one type of cell
- Not toxic
- Fewer side effects as there doesn;t need to be used in large doses
37
Ethical issues of monoclonal antibodies?
- Animals are used and may suffer
- Vaccines may not be fairly distributed to people
- Cancer is deliberately induced in the animals
38
Why is the ELISA test useful?
- We can measure the presence and quantity of a protein in a sample.
39
What can the ELISA test for?
- Infections
- Allergies
- Levels of a drug
40
Outline the ELISA test...
1) Antigen is bound to the surface of a well.
2) Antibody specific to the antigen is added and will bind if present (enzyme linked, enzyme attached)
3) rinse the well to remove unbound antibodies
4) Substrate solution is added, substrate binds to enzymes
5) Causes a colour change
6) colourimeter detects the amount of colour change which correlates to the the amount of antigen present.
41
What is the purpose of membranes?
- Act as barriers between cells and their environment as well as between the cytoplasm and the organelle
42
What is the fluid mosaic membrane?
- The structure of all cell membranes is the same being made of lipids, proteins and carbohydrates
- It is fluid as phospholipids are constantly moving and mosaic because it is packed full of proteins.
43
What are intrinisc proteins?
- Span the two sides of the membrane
44
What are channel proteins?
- Water filled tubes which allow water soluble molecules to pass through
45
What are carrier proteins?
- Proteins that bind to molecules or ions and change their shape to move them across.
46
What are extrinisc proteins?
- Mechanical support for the membrane, acting as cell receptors for molecules such as hormone and act as receptors to identify other cells
47
What are glycoproteins
- Proteins with carbohydrates attached
- They act as receptors for molecules such as hormones and neurotransmitters.
- Allows cell adhesion
- Allow cell recognition
48
What are glycolipids?
- Lipids with carbohydrates attached
- Act as recognition sites
- Help stability of the membrance
- Cell adhesion
49
What is cholesterol?
- A type of lipid
- Restricts the movement of other molecules in the membrane which causes rigidness
- They can bind to phosopholipid fatty acid tails to pack closely together.
50
Why is the centre of the bilayer being hydrophobic important?
- The centre of the bilayer is hydrophobic so no water soluble substances pass through such as ions
51
What are the transport mechanisms?
- Diffusion
- Facilitated diffusion
- Active transport
- Osmosis
- Co-transport
52
What factors affect the rate of diffusion?
- Concentration gradient
- Surface area
- Temperature
- Diffusion distance
- Size of particle
- Number of channel/carrier proteins
53
What is water potential?
- The pressure created by water molecules
- The likelihood of water molecules to move in or out
54
What is hyper and hypotonic?
- Hypertonic the movement of water into a cell causing bursting
- Hypotonic is the movement of water out of a cell
(remember hyper movement into not out)
55
What is active transport?
- The movement of molecules or ions from a region where they are in low concentration to one where their concentration is higher, against a concentration gradient.
56
What is co transport?
- Takes place in the ileum where concentration is too low for diffusion to occur.
57
Outline the process of co transport...
1) Sodium ions are actively transported out of the epithelial cells into the blood via a sodium potassium pump in exchange for a potassium ion (carrier protein)
2) Low conc of sodium ions creating diffusion gradient of sodium from the lumen
3) Sodium ions diffuse into epithelial cells via a sodium-glucose co transporter protein and as it does this is couple with a glucose molecule to take more glucose into the epithelial cell too.
4) Concentration of glucose inside cell increases too.
5) Glucose diffuses into the blood via facilitated diffusion
58
How are algal cells similar to plant cells?
- They have the same organelles as well as a cell wall and chloroplast
59
How are fungal cells different to plant cells?
- Cell walls are made of chitin, not cellulose
- Fungal cell don't have chloroplasts
60
Go over the structure of Nucleus, mitochondria, chloroplasts and their functions (easy stuff)
..
61
Structure of the golgi apparatus..
- Group of fluid-filled, membrane bound flattened sacs
- Vesicles are often seen at the edges of the sacs
62
Function of the golgi apparatus
- Processes and packages new lipids and proteins
- Also makes lysosomes
63
Structure of the golgi vesicle?
- Small, fluid filled sac found in cytoplasm which is surrounded by a membrane and produced by golgi apparatus
64
Function of golgi vesicle?
- Store lipids and proteins produced by the golgi apparatus and transport them out of the cell via exocytosis
65
Structure of lysosome?
- Round organelle surrounded by a membrane with no clear internal structure
66
Function of lysosome?
- Contains enzymes that hydrolyse invading cells or worn out components
67
Structure of ribosomes?
- Small organelle
- Made of protein and rRNA
68
Structure of the rough ER?
- System of membranes enclosing a fluid filled space
- Consistent with the nuclear envelope and covered with ribosomes
69
function of the rough ER?
- Process and packages proteins made at the ribosome.
70
Structure of smooth ER?
- Similar structure to the rough ER but no ribosomes
71
Function of smooth ER?
- Synthesise and processes proteins and lipids
72
4 key points about prokaryotic structure?
- The cytoplasm has no mmebrane bound organelles
- Ribosomes are much smaller than in eukaryotic cells (70s only)
- Single ciruclar DNA molecule that is free in the cytoplasm and isn't associated with proteins
- Cell wall supports the cell and prevents change in shape made of muerin (peptidoglycan)
73
What are other unique features of prokaryotic cells?
- One or more plasmids (small loops od DNA which contain genes for things such as antibiotic resistance and are used to transfer genetic material between bacterium)
- Slime capsule helps protect bacteria from attack by other cells and helps bacteria group together for further protection
- Flagella allow the bacteria to move
74
Key differences between eukaryotic cells and prokaryotic cells...
- Prokaryotic have no nucleus but eukaryotic do
- Prokaryotic have plasmid but eukaryotic don't
- Prokaryotic have smaller ribosomes than eukaryotic cells
- Prokaryotic cells have a peptidoglycan cell wall but eukaryotic have a cellulose cell wall in plants
75
Structure of viruses?
- Acellular and non-living
- Genetic material
- Capsid
- Attachment proteins
76
How do viruses replicate?
- Bind to complementary receptor proteins using attachment proteins
- Inject genetic material into the cell
- Host cell's enzymes and ribosomes are used to make new viral proteins that assemble into viruses which are released from the host and go on to hijack other cells.
77
Light microscopes vs electron microscopes regarding (how they work, magnification, resolution, live speciment)
Light: Uses a beam of light
Electron: Uses a beam of electrons
Light: Max magnification of x1500
Electron: Max magnification of x1,500,000
Light: Max resolution (0.2 micrometres)
Electron: Max resolution (0.002 micro metres)
Light: Live specimen yes
Electron: Live specimen no because speciments have to be contained in a vacuum as the air particles would absorb electrons and interfere with results.
78
What organelles can light microscopes not see?
- Cannot see ribosomes, endoplasmic reticulums and lysosomes as theyre too small for the 0.2 micrometre resolution
79
Outline 5 features of the Transmission Electron Microscope...
- Electrons are transmitted through the speciment
- Show you the internal structure of organelles
- Higher resolution
- Can only be used for thin speciments
- 2D images
80
Outline 5 features of the Scanning electron micrsocope?
- Scan a beam of electrons across the speciment
- Only show the specimen's surface
- Lower resolution
- Can be used for thick speciments
- 3D
81
Define resolution and magnification (search)
...
82
What is cell fractionation?
- Process by which cells are broken up and their organelles are separated out
83
What is homeginisation?
- Breaking up cells using a homogeniser or by vibrating them
84
Why must solutions be cold, isotonic and pH buffered?
Cold - reduces enzyme activity which may hydrolyse organelles
Isotonic - To prevent the movement of osmis which may burst or shrink the cell
Buffered - To maintain pH and prevent ay damage to organells or enzymes
85
What is filtration?
- Resultant fluid is filtered to remove any unbroken cells or cell debris
86
What is ultracentrifugation?
- Different organelles in the filtered solution are separated out in a centrifuge
- Centrifuge spun at low speed forming pellet (individual organelle) and supernatent (remaining liquid)
- Spun at higher speed
87
Order of organelle density
Nucleus, mitochondria, lysosomes, ER, ribosomes
88
2 types of cell division
- mitosis, meiosis
89
Overall purpose of mitosis?
- Produces 2 genetically identical daughter cells
90
2 things mitosis is needed for?
- Growth
- Repair
91
What happens in prophase?
- Chromosomes condense, get shorter and fatter
- Nucleolus disappears
- Nuclear envelope breaks down
- Centrioles move to opposite poles
92
What happens in metaphase?
- Spindle fibres pull chromsomes to the equator of the cell
93
What happens in anaphase?
- Centromeres divide separating each pair of sister chromatids
- Spindle fibres shorten and pull each chromatid to opposite poles where they are referred to as chromsomes
94
What happens in telophase?
- Chromsomes lengthen again
- Spindle fibres disintegrate
- Cytoplasm divides to form two sepearate cells.
95
What is interphase?
- Part of the cell cycle
- Period of cell growth and DNA replication
96
What is G1
- Cell grows and increases in volume when new organelles are made
97
What is S?
- Cell replicates its DNA
98
What is G2?
- Cell continues growing and synthesises enzymes and structures needed for mitosis
99
Calculation for time taken for each stage?
Number of cell in phase/total number undergoing mitosis x time taken for one cell cycle
100
Mitotic index
Number of cells undergoing mitosis/Total number of cells x100
101
What is cancer?
- Uncontrolled cell division by mitosis
102
How do bacteria divide?
- Binary fision
1) Replication of DNA and plasmids
2) circular DNA strands move to opposite poles
3) Cytoplasm divides and new cell walls grow to divide the original cell into 2 identical daughter cells, each with 1 copy of the ciruclar DNA and a variable number of plasmids.
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