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a-level bio (aqa) > 2: Cells > Flashcards

2: Cells Flashcards

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1
Q

What is a eukaryote?

A

A cell with a distinct nucleus (e.g. plant, animal, fungi).
- larger than prokaryotes
- has many similar structures (with membranes)
- very complex

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2
Q

What is a prokaryote?

A

a single-celled organism without a distinct nucleus (e.g. bacteria)
- genetic material floats freely in cytoplasm
- less than 2µm in diameter
- no membrane- bound organelles in the cell

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3
Q

What is a cell surface membrane?

a.k.a plasma membrane

A
  • outer surface of the cell
  • regulates movement in and out of the cell
  • contains receptor molecules to allow it to respond to chemicals
  • may be surrounded by slime capsule
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4
Q

What is a nucleus?

A
  • large organelle surrounded by nucleic envelope (a membrane with pores)
  • contains chromosomes and 1 or more nucleolus (which makes proteins)
  • controls cell activity (DNA which instructs proteins)
  • pores allow substances to move through the nucleus to the cytoplasm
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5
Q

What is cytoplasm?

A
  • everything in the cell outside the nucleus
  • has water, proteins and other organic and inorganic molecules and organelles
  • has viscous aqueous fluid (cytosol)
  • site of biochemical reactions
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6
Q

What is mitochondria?

A
  • where aerobic respiration takes place, producing chemical ATP (adenosine triphosphate)
  • oval shaped covered in double membrane
  • inner membrane folded forming cristae
  • has liquid inside (matrix), containing enzymes for aerobic respiration.
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7
Q

What is the golgi apparatus?

A
  • a group of fluid filled membrane-bound flattened sacs called cisternae
  • processes and packages lipids and proteins, which are then stored and transported, out by vesicles
  • they produce lysosymes
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8
Q

What are the golgi vesicles?

A
  • transport proteins and substances to cell surface where they fuse with the plasma membrane
  • also transports lipids
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9
Q

What are lysosymes?

A
  • round organelles surrounded by a membrane with no clear internal structure
  • contains digestine enzymes (lysozymes) which can digest hydrolyse or break down worn out components of a cell
  • kept seperate from cytoplasm by membrane
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10
Q

What are ribosomes?

A
  • found floating in cytoplasm or on the rough e.r.
  • made of proteins, not surrounded by a membrane
  • where proteins are made (protein synthesis)
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11
Q

What is the rough endoplasmic reticulum?

A
  • system of membranes that enclose a fluid filled space.
  • ‘rough’ as there’s ribosomes attatches to it
  • responsible for folding and processing proteins made by ribosomes
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12
Q

What is the smooth endoplasmic reticulum?

A
  • no ribosomes on surface
  • synthesising (making) and processing lipids/ fats
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13
Q

What is the vacuole

A
  • membrane bound organelle in the cytoplasm
  • permanent in plant cells
  • membrane is called tonoplast
  • contains cell sap to maintain pressure in the cell, keeping it rigid
  • involved in isolation of unwanted chemicals in the cell
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14
Q

What is the cell wall?

A
  • provides cell support and prevents it from changing shape

plant/algal cell- made of cellulose
bacteria cell- made of murein
fungal cell- made of chitin

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15
Q

What are chloroplasts?

A
  • in plant cells/ photosynthetic organisms
  • have a double membrane
  • has a membrane called thylaboids which can be stacked together to form grana which can be linked by another membrane to form lamellae
  • some photosynthesis occurs in grana and stroma (the fluid in chloroplasts)
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16
Q

What are some other cellular organelles?

A
  • cytoskelenton- gives cell its’ shape, organises cell parts and responisble for locomotion and organelle movement
  • microfilament- responsible for cell movement and changes in shape, thinnest part of cytoskelenton and makes muscle contraction possible
  • centrioles- hollow fibres, 2 cenrtrioles at right angles to each other form a centrosome to organise spindle fibres in cell division
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17
Q

What is the structure of prokaryotes?

A
  • not attatched to any histone proteins (turn DNA into structural units, nucleosome)
  • has plasmids that carry information from one place to another the cytoplasm
  • plasmids contain the genes for antibiotic resistance that can pass through different prokaryotes to another
  • a slime capsule surrounds the cell wall to protect the cell from being attacked by the immune system
  • murein cell wall (in bacteria)
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18
Q

What is binary fission?

bacterial mitosis

A
  1. circular DNA and plasmids replicate (main loop only replicates once, plasmids can replicate multiple times)
  2. cell gets bigger and DNA loops move to opposite cell poles (plasmids aren’t split evenly)
  3. cytoplasm begins to divide, new cell walls begin to seperate
  4. cytoplasm divides producing 2 daughter cells (not genetically identical as plasmids aren’t split evenly

occurs in 20 min incriments, fission means seperate

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19
Q

What is a virus?

A
  • not living, acellular
  • has nuceic acid surrounded by proteins
  • smaller than bacteria
  • no membrane, cytoplasm or ribosomes
  • cant reproduceon their own, require host cell to inject genetic information into
  • host cell uses own machinery within the cell to replicate viral particles
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20
Q

What is the structure of a viral cell?

A
  • contains core with genetic material
  • has capsid (a protein coat around the core)
  • has attatchment proteins that stick out from the capsid do it can bind to a complementary receptors on host cells
  • different viruses have different attatchment proteins and therefore require different receptor proteins
  • some viruses infect only 1 cell, others can affect multiple
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21
Q

What is viral replication?

A
  1. attatchment proteins on the virus binds to complementary receptor sites on host cells’ cell surface membrane
  2. the capsid is released into the host cell where it uncoats itself, releasing the core with genetic material into the cell’s cytoplasm
  3. a process called reverse transcriptase makes a complementary strand of* DNA* from a RNA/DNA template
  4. the double stranded DNA is inserted into host DNA
  5. host cell enzymes are used to make viral proteins, which are assembles into new viruses that burst the host cell and infect other cells
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22
Q

What is the magnification and resolution?

A

magnification- how many times bigger the image is compared to the specimen
resolution- the ability to distinguish between 2 point close together

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23
Q

How do you calculate image size?

A

IMAGE SIZE= actual size× magnification

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24
Q

What’s an optical microscope?

A
  • uses light beam so the specimen needs to be thin
  • maximum resolution= 0.2µm (wavelength of light)
  • can’t see small subcellular structures
  • maximum magnification= ×1500
  • only simple preperation needed
  • can see living and dead organisms
  • coloured
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25
Q

What are electron microscopes?

A
  • uses beam of electrons to form image
  • maximum resolution= 0.0002µm (for organelles)
  • maximum magnification= ×1500000
  • 2 types: transmission and scanning
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26
Q

What’s a transmission electron microscope?

A
  • electromagnet focuses electron beam to transmit through the specimen
  • denser parts absorbs more electrons so they appear darker
  • image appears 2D in black and white (you can add colour with false colour imaging)
  • higher resolution to see internal structure
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27
Q

What is a scanning electron microscope?

A
  • scans beam of electrons, knocks electrons on surface that gather in a cathode ray tube
  • only shows cell outer surface
  • 3D image in black and white
  • lower resolution than TEMs
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28
Q

What is cell fractionation?

A

homogenisation-break down cell by grinding in blender, pistel and pellet, homogeniser or vibrating cells to break down plasma membrane and release organelles.
filtration-filter the solution with gauze to seperate the large debris (e.g. connective tissue). organelles pass through gauze
ultracentifugation-spin for pellets in a centifuge machine, spin at increasing speeds. pour solution into next tube.

solution must be cold, isotonic (even concentration) and with a buffer

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29
Q

What is the order of pellets in cell fractionation?

A

animal- nuclei, mitochondria, lysosomes, endoplasmic reticulum, ribosomes
plant- nuclei, chloroplast, mitochondria, endoplasmic reticulum, ribosomes

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30
Q

What is the cell cycle?

A
  1. Interphase-cell prepares to divide as cell grows to make proteins and organelles (G1), DNA unravels and replicates (S), genes double and cell grows (G2)
  2. Prophase-chromosomes (2 sister chromatids joined at the centromere) condense and become shorter. the nuclear envelope breaks down, freeing chromosomes in the cytoplasm (early prophase). centrioles ove to opposite cell poles producing spindle/ protein fibres (late prophase).
  3. Metaphase-chromosomes meet at the centre, spindle fibres attatch to each centromere
  4. Anaphase-centromere divides and spindle fibres contract pulling V-shaped chromatids to opposite cell poles.
  5. Telophase-chromatids reach opposite sides, uncoil and thin again, 2 new nuclear envelopes form around chromosomes and cytokenesis occurs (cytoplasm pinches inwards). 2 genetically identical daughter cells form. This process repeats

I Peed on the MAT

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31
Q

What are calculations for mitosis?

mitosis time/ mitotic index

A

mitosis time= (no. cells in certain stage÷ no. cells observed)× total time
mittoc index= no. cells with visible chromosomes÷ no. cells observed

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32
Q

How can you identify different stages of mitosis on a diagram?

A

Interphase- chromosomes invisible in nucleus
Prophase- chromosomes visible
Metaphase- chromosomes at equator of cell
Anaphase- chromosomes pulling apart/ V-shaped
Telophase- 2 nuclei and cell walls begin to form

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33
Q

What are tumours?

A
  • mitosis and cell cycle caused by genes
  • when our cell cycle divides enough, they tend to stop dividing
  • a mutation in a gene causes cells to grow out of control if it controls cell division
  • the cell keeps dividing to make more cells
  • this forms a tumour
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34
Q

How do cancers form?

A
  • if a tumor can invade other tissues, it’s a cancer(malignant)
  • some cancer treatments are designed to control the rate of cell division in the tumor by disrupting the cell cycle, killing cells
  • these treatments can kill positive and bad cells (tumour cells)
  • they are more likely to kill tumour cells though as they divide more rapidly
  • this is why chemo-therapy is spread out
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35
Q

How do cancer treatment drugs work?

A
  • disrupt G1 phase of the cell cycle/ organelle synthesis (chemo therapy)
  • they prevent synthesis of enzymes needed for DNA replication
  • if not produced, the cell can’t enter the synthesis phase, disrupting the cell cycle, forcing the cell to kill itself
36
Q

How does radiation therapy work?

A
  • radiation therapy and some drugs can cause damage to the cell’s DNA
  • at several points during the cell cycle, the DNA is checked for damage
  • if severe damage is detected, the cell will kill itself, oreventing any further tumour growth
37
Q

What is the role of the cell surface (plasma) membrane?

A
  • surrounds cell, barrier between cell and external environment
  • controls substances leaving and entering the cell
  • partially permeable mebrane (only some molecules pass through)
  • substances enter cell through transport (4 types)
38
Q

What are roles of different membranes in cells?

A
  • all partially permeable to seperate cells from the cytoplasm
  • RNA can leave the nuclear envelope, the DNA can’t as it’s too large
  • made of lipids (mainly phospholipids), carbohydrates and proteins
  • these phospholipids form a continuous bilayer around the cell
  • bilayer is ‘fluid’ (can move) as phospholipids are constantly moving

fluid mosaic model- describes all basic cell membrane characteristics

39
Q

What is the phospholipid bilayer?

A
  • phospholipids form barriers to dissolved substances (water soluble)
  • phospolipids automatically arrange into the bilayer (hydrophillic head outwards, hydrophobic tail inwards)
  • canter of layer is hydrophobic and can move
  • water soluble substances (e.g. ions, polar molecules, glucose) can’t diffuse through the membrane
  • though water is small, it can diffuse through by mitosis (as it’s small)
  • has many proteins scattered through bilayer (e.g. channel/ carrier)
  • allows molecule to pass through the membrane
  • molecules/ ions can pass through channel proteins, simple diffusion and carriers by active transport and facilitated diffusion
40
Q

What is the role of proteins in the phospholipid bilayer?

A
  • receptor proteins help the cell to detect chemicals
  • these chemicals help the cell to respond in certain way (e.g. insulin binding to complementary liver receptors)
  • proteins and lipids may have carbohydrates attatched to them (glyco-)
  • these are invlolved in cell signalling and recognition
  • the bilayer also has cholesterol to privide stability found between phospholipids, binding to their tails packing it tightly.
  • this can restict movement in the bilayer, allowing the membrane to be more rigid
  • this maintains the shape of animal cells (as they don’t have a cell wall)
  • important in places like the red blood cells, aren’t suported by other cells and flow freely
41
Q

What is the impact of temperature on the cell membrane?

0,40,45+

A

0°C- phospholipid bilayer has little energy:
- doesn’t move as much, close together keeping cell rigid
- proteins can denature increasing permeability
- ice crystals can puncture ppm
- larger molecules can pass through
0-40°C- phospholipids have most efficient energy:
- phospholipids can move around, aren’t as packed closely together
- membrane is partially permeable
- as temp. increases, phosphopid molecules move around more and have more energy, increasing permeability
45+°C- phospholipid layer breaks down
- membrane becomes more permeable
- water in the cell expands putting pressure on the plasma membrane
- channel and carrier proteing begin to denature and remaine open increasing cell permeability

42
Q

What is diffusion?

A

WHAT?: the overall movement of particles in a gas or liquid from a region of high concentration to regions of low concentration, down the concentraion gradient
- particles continue to diffuse until there’s an even distribution of particles
- when particles are able to diffuse directly across the membrane, this is simple diffusion (without help)

this is a passive process (doesn’t rquire energy)

43
Q

What factors affect the rate of diffusion?

A

-** concentration gradient:** steeper concentration gradient, faster diffusion rate. as particles diffuse across the membrane, the difference in concentration gradient decreases until partciles reach equilibrium
- thickness in exchange surfaces: thinner, shorter diffuion pathway, faster rate, less distance needs to be travelled
- surface area: larger surface area/ exchange surface, faster rate of diffusion

44
Q

What is facillitated diffusion?

A

larger molecules (e.g. glucose/ amino acids) diffuse slowly across the phospholipid bilayer, so to increase the diffusion rate, carrier proteins are needed
CARRIER PROTEINS: protein changes shape to release molecule, each carrier protein is complementary to moving a certain substrate
CHANNEL PROTEINS: pores in the cell membrane allow diffusion, charged particles diffuse for facilitated diffusion complementary to them

a passive process as it still goes down the concentration gradient

45
Q

What factors affect FACILLITATED diffusion?

A
  • concentration gradient
  • **no. carrier/ channel proteins on surface membrane: **more proteins, faster diffusion rate but if all proteins are occupied, rate of diffusion remains constant
46
Q

What is active transport?

A

the movement of molecules against the concentration gradient, requiring energy in the form of ATP from mitochondria

47
Q

What factors affect active transport?

A
  • speed of carrier proteins
  • no. carrier proteins, limited by when they’re occupied
  • rate of respiration is dependend on ATP availability which controls the rate of active transport
48
Q

What is the role of carrier proteins?

A
  • move against the concentration gradient, requiring energy
  • ATP (adenosine triphosphate breaks down with hydrolysis (water) to form ADP (adenosine diphosphate) and pi (inorganic phosphate)
  • energy is released and used to transport substances and solutes
49
Q

What are co-transport proteins?

A
  • binds to 2 molecules at once
  • if one substance goes down the conc. gradient, other substance can move with it, against it
    e.g. glucose and sodium
  • sodium diffuses out of the cell down conc. gradient (high-low)
  • steep conc. gradient of sodium also moves glucose across the membrane against its conc. gradient

a type of carrier protein (symport- same direction, antiport- different)

50
Q

What is water potential (ψ)?

A
  • the likelihood of water molecules to diffuse/ move into or out of a solution
  • ‘free water’ (amount of water molecules free/ not dissolved)
  • more free water, the more it will move (pure wayer)
51
Q

What is osmosis?

A
  • movement of water molecules fron a region of high water potential (less negative) to a region of low water potential (more negative) across a partially permeable membrane, down the water potential gradient
52
Q

What is pure water?

A
  • water potential 0 (100% free water)
  • if a solute is added to the water, it lowers the water potential and the water potential is negative

lower w.p., less free water, more negative

53
Q

What is the effect of solutions with different water potentials?

same, higher and lower

A

if solution has the same w.p. on both sides of the ppm:
- solution is isotonic
- cells don’t lose or gain water, no net water movement or difference in water potential
if solution has higher w.p. than the inside of the cell:
- cell is hypotonic (too little solutes)
- if cell is places into solution with higher w.p., water will move into cell by somsosis so it swells/ bursts (lysis/ turgid)
if solution has a lower w.p. than inside of the cell:
- cell is hypertonic (too much solutes)
- if cell is placed into a hypertonic solution with less free water, water will move out of cells by osmosis, so cell shrivels (flaccid)

higher water potential, more free water, less negative

54
Q

What factors affect the rate of osmosis?

A
  • water potential/ concentration gradient:
    higher w.p. gradient, faster osmosis rate as osmosis continues, difference in w.p. on either side of the membrane decreases, so the rate levels pff
  • thickness of exchange surface (shorter diffusion pathway, faster)
  • surface area of exchange surface (larger)
  • temperature (evaporation of water, less free water, more energy)
55
Q

What in the immune system identifies foreign cells?

A
  • embedded in the cell-sirface membrane are proteins involved in cell recognition and act as antigens.
  • allow immune cells in the body to recognise the difference between our body cells (self) vs foreign cells (non-self)
  • this includes pathogens (causing disease), abnormal body mcells, cells from other people of the same species and toxins
56
Q

What are foreign cells?

A
  • cancerous or pathogen infected body cells have abnormal antigens on their cell surface membrane
  • toxins and poisons from other cells are antigens themselves
  • cells from other people will have different blood to your own (e.g. blood transfusion, organ transplants)
57
Q

What are the 4 different blood groups and the effect of their antigens?

A

Blood A- antigen a
Blood B- antigen b
Blood AB- antigens a and b
Blood O- antigen o

  • if a person needs a blood transfusion, they can only receive blood with the same antigens as there’s
  • a wrong blood type triggers the immune response
58
Q

What is the immune response?

A
  • triggered when a foreign antigen is detected in the body; this involves different white blood cells with different roles in the immune system
  1. phagocytosis
  2. t-cells
  3. b-cells
  4. antibody production
  5. production of memory cells and immunity
59
Q

immune response

1.PHAGOCYTOSIS

A
  • when an invading pathogen enters the body, phagocytes recognise the foreign antigen
  • cytoplasm of phagocyte engulfs it and surrounds the non-self cell
  • pathogen’s contained in phagocyctic vacuole in cytoplasm (seperate from the cell)
  • lysosome (witn lysozymes) fuses wit phagocytic vacuole and release digestive enzymes to break down and digest it
  • phagocyte presents pathogens’ antigens on the cell membrane
  • the phagocyte becomes an antigen presenting cell, activating the other immune system cells
60
Q

immune response

2.T-CELLS

A
  • a type of white blood cell with receptor proteins on the plasma membrane
  • binds to complementary antigens on the antigen presenting cell (phagocyte), activating the T-cells
  • helper T cells (Th) release chemical signals, activating and stimulating phagocytes and cytotoxic (Tc) to kill foreign/ abnormal cells
61
Q

immune response

3.B-CELLS

A
  • Th cells activate the B-cells when they bind to the antigen, secreting antibodies
  • B cells (B lymphocytes) are covered with antibodies each with different shaped binding sites, so they only form antigen-antibody complexes with antigens with a complementary shape.
62
Q

immune response

4.ANTIBODY PRODUCTION

A
  • B cells divide by mitosis to form plasma (identical) cells
  • this is called clonal selection when all cells are genetically identical and produce identical (monoclonal) antibodies specific to the pathogen
  • plasma cells secrete lots of antibodies
63
Q

immune response

5.PRODUCTION OF MEMORY CELLS AND IMMUNITY

A
  • after being exposed to antigen T and B cells, they also produce memory cells
  • Memory T cells remember the specific antigens and will recognise them if they enter the body again
  • Memory B cells remember the antibodies that are needed to bind to the antigens
  • the memory cells remain in the body for a long time, making them immune
64
Q

What is the primary response to pathogens?

A
  • when a pathogen first enters the body, the primary response is triggered
  • this response is slow as there aren’t many
    B-cells for that antigen to make the correct antibody needed to bind to it
  • the body eventually produces the right antibody
  • slow recovery, shows symptoms in the person
65
Q

What is the secondary response to pathogens?

A
  • if the same pathogen enters the body again, the secondary response is triggered
  • therefore clonal selection occurs faster and b-cells are activated, divided into plasma cells, producing the correct antibody
  • this destroyed the antigen before any symptoms show
66
Q

What is the difference between the cellular and humoral response?

A
  • cellular- t-cells and other immune system cells that they interact with (e.g. phagocytes) forming the cellular response
  • humoral- b-cells, clonal selection and the production of monoclonal antibodies form the humoral response

both responses are needed to remove the pathogen

67
Q

What is the structure of an antibody?

A
  • have two binding sites to bind to two pathogens at once
  • y-shaped (stick part is the constant region and two binding sites are the variable region)
  • variable region controls antibody specificity forming antigen binding site
  • variable region has a unique tertiary structure (complementary) -> disulphide bridges make constant region
  • Two binding sites cause pathogens to be clumped together (agglutination)
  • When the phagocyte binds to the antibodies, they engulf many pathogens at once

made of proteins (amino acid chains)

68
Q

What is antigenic variation?

A
  • when invading pathogens enter the body, antigens trigger the primary immune response, taking time, showing symptoms
  • when the same pathogen enters again, the secondary response occurs (immunity)
  • if you get the same virus you had before but it changed its antigens, the immune response has to start again, causing illiness
69
Q

Why does antigenic variation occur?

A
  • this is because memory cells produced won’t recognise antigens as they change regularly on surface membrane
  • e.g. flu vaccines change regularly as antigens change(different strains of flu)
  • as they’re the same pathogen, type but different antigens, they’re different strains of the pathogen
  • if memory cells don’t recognise the new strain of the same pathogen, the previous vaccine won’t work, causing you to show symptoms
  • new vaccines are developed, the most effective one is distributed

both pathogen strains are immunologically distinct

70
Q

What is HIV (human immunodeficiency virus)?

A
  • virus that attacks the immune system (virus aren’t living, they have to have host cells)
  • HIV infects and kills helper T-cells, acting as host cell for the virus
    STRUCTURE:
  • spherical with core (containing RNA with proteins+enzymes for reverse transcriptase)
  • outer coating (capsid) which has an extra outer layer (envelope)
  • has attatchment proteins for host cell
71
Q

What occurs during HIV replication?

HIV doesn’t have enzymes or ribosomes to replicate

A
  1. attatchment proteins attatch to receptor molecules on cell membrane of host helper T-cell
  2. capsid released into host cell where is uncoats and releases RNA into cytoplasm
  3. enzyme reverse transcriptase is used to make complementary DNA strand from viral RNA template
  4. double stranded DNA is made and inserted to human DNA
  5. host cell enzymes used ti make viral proteins from viral DNA found in human DNA
  6. viral proteins are assembled into nre viruses which bud from the cell and go onto infect other cells

when new HIV emerges from the host cell, cell emerges and dies

72
Q

What is the difference between HIV and AIDS?

A
  • When HIV in first infects the body it replicates rapidly and the person may experience symptoms of illness
  • After initial infection period the replication of HIV drops to a lower level
  • this is called the **latency period ** which can last for years and the person may not experience any more symptoms
  • as HIV replication continues as results in a decrease in the number of helper t cells in the body so the immune system can’t effectively respond
  • eventually number of helper t cells in body reaches a critically low level developing **AIDS **
  • When someone’s immune system fails or deteriorates making them vulnerable to more infections like pneumonia
  • They can develop diseases that normally wouldn’t cause issues in a healthy immune system
73
Q

What are the symptoms of AIDS?

A
  • initial symptoms: minor mucus membrane infections and recurring respiratory infections
  • as the number of immune system cells decreases the person becomes more susceptible to more serious infections (like chronic diarrhoea bacterial infections under tuberculosis)
  • during later aids stages some people may develop serious infections like toxoplasmosis of the brain (a parasitic infection)
  • They may also develop a fungal infection called candidiasis in the respiratory system

It’s these infections not HIV that kills the AIDS patient

74
Q

What is active immunity ?

A
  • what: when your own immune system produces antibodies following antigen exposure

natural- when you catch a disease and also produce antibodies
artificial- when you catch a disease and also produce antibodies given vaccine with antigen so the body produces antibodies

75
Q

What is passive immunity ?

A
  • what: when the immune system doesn’t produce antibodies in your given antibodies from a different organism

natural- for example babies are immune to diseases as they receive antibodies from their mother through breast milk and placenta
artificial- inject antibodies from someone else

76
Q

What is the difference between active and passive immunity ?

A
  • active has a slow response to protection and passive has an immediate response to protection
  • in active you need to be exposed to the antigen whereas in passive you don’t need exposure
  • In active memory cells are produced however in passive no memory cells are produced
  • Active provides long-term protection as antibodies are produced and response to complementary antigens in the body however in passive short-term protection is provided and antibodies eventually break down
77
Q

What is a vaccine ?

A
  • contains antigen stimulating our immune system to produce antibodies, plasma cells and memory cells against a particular pathogen without causing disease
  • against a particular pathogen without causing disease either contain free antigens or antigens attached to dead (attenuated/ weak living) pathogens so no symptoms or diseases are caused
    -Can be taken orally or injected
78
Q

What are advantages and disadvantages of Vaccines ?

A

ADVANTAGES:
- herd immunity- protect others from disease, reducing ocurrences of disease in the population so those aren’t vaccinated are less likely to catch the disease
DISADVANTAGES:
- orally: Maybe broken down by enzymes as its digested
- vaccine: hard to absorb into the bloodstream if they’re large molecules
- ethical issues- all Vaccines tested on animals before tested on humans
- Testing Vaccines on humans can be risky as volunteers put themselves at risk of gaining the disease
- Some people don’t take vaccine due to the side effects
- Difficult to decide who to give Vaccines too first it in risk of disease

79
Q

What is an elisa test?

A
  • an enzyme linked to an immunosorbant assay, using enzymes linked to antibodies to detect presence of antigens abd antibodies in a persons blood
  • test to see if personhas certain illness or antigena
80
Q

What are the steps of a direct elisa test?

A

used to test patient’s sample for presence of an antigen using only 1 type of antibody
1. take patient’s blood sample and remove plasmids/ antigens
2. bind all antigens to wall of test plate
3. detection antibody (with enzymes) with complementary binding site to the antigen is added to the wells
4. well is washed out to remove unbound antibodies
5. substrate is added to the wells
6. enzyme on antibody will react with substate causing it to change colour as it’s broken down
7. the colour chage means the patient has tested antigens

colour change intensity -> concentration of antigens

81
Q

What are the steps of an indirect elisa test?

A

used to test a patient’s sample for the presence of an antibody with a secondary antibody
1. take patient’s blood sample, removing plasmids and COMPLEMENTARY antigens
2. antigens complemetary to antibody is binded to the wall of the plate
3. antibodies from the patient’s blood plasma is added to the wells. if antibodies are present, they bind to antigens
4. well is washed out to remove unbound antibodies
5. secondary antibodies (with enzyme) complementary to antibody are tested for is added to the well
6. wash out well secons time to remove unbound secondary antibodies
7. add substrate and observe for colour change

colour change intensity -> concentration of antibodies

82
Q

What is a lateral flow test?

A
  • used to detect the preence of hormones (in pregnancy) and antigens (in covid) in a patient’s sample
  • these use antibodies (mobile or immobile) with a complementary binding side to the antigen or hormone being detected
  • antibodie have a coloured bead attatched to them
83
Q

What is the structure of a lateral flow test?

A
  • application area contains antibodies with comp. binding site to hormone/ antigens being detected
  • mobile antibodies have coloured bead attatched
  • in display window, there’s the same antibodies (no coloured beads) that are immobiised
  • further up the window, there’s a control zone
84
Q

What happens when the patient’s sample is applied to the application area?

A
  • when patient’s sample is applied to the application area, if hormone/ antigen is present, it will bind to the binding site on the anbtibody forming
  • sample contains fluid (urine/ buffer) causing sample to move up absorbent strip, carrying antibodies with them
85
Q

What is the method of lateral flow test?

A
  • first strip in the display window contains immobilised antibodies
  • Antigen antibody complexes that form bind to immobilised antibodies as they move up the test strip
  • Accumulation of antigen antibody complexes with coloured bead attaches to them causing a coloured strip to appear
  • If no antigen antibody complexes form, antibodies with coloured bead attached continue to move up the strip and no colored line forms
  • Any antibodies with coloured beads attached to them form antigen antibody complexes continue to move up the test immobilised on the second strip
  • Accumulation of antibodies with colored bead attached to them cause coloured strip to appear showing the test worked

immobile antibodies- strip
mobile antibodies- application zone

86
Q

What is an antigen and antibody?

A

Antibody: A protein found in the blood that is produced by plasma cells which binds to antigens as a part of the immune response.
Antigen: a foreign cell that can be detected by antibodies and trigger an immune response.

a-level bio (aqa) (8 decks)

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