Topic 2 - Cells Flashcards
1
Q
what are the distinguishing features of eukaryotic cells
A
cytoplasm containing membrane-bound organnelles. DNA enclosed in a nucleus
2
Q
what general structures does a eukaryotic cell have
A
cell surface membrane
mitochondrion
nucleus
ribosomes
RER
SER
golgi apparatus
lysosome
3
Q
what general structures does a plant cell have
A
cell surface membrane
mitochondrion
nucleus
ribosomes
RER
SER
golgi apparatus
lysosome
chloroplast - plants, algae
cell wall - plants, fungi, algae
cell vacuole - plants only
4
Q
describe the structure of cell-surface membrane
A
hydrophillic phosphate heads which are attracted to water
hydrophobic fatty acid tails which repell water
known as a phospholipid bilayer with proteins
5
Q
describe the function of cell-surface membrane
A
selectively permeable - enables control of passage of substances in and out of the cell
molecules/receptors/antigens on the surface which allow for cell recognition/signalling
6
Q
describe the structure of the nucleus
A
nuclear envelope - double membrane and nuclear pores (3000) which allow large molecules to enter/leave the nucleus e.g. mRNA
outer membrane of the nucleus is usually continuous with membrane of RER
nuceloplasm - aqueous, granular, jelly-like material
possesses a nucleolus
protein/histone-bound linear DNA with condensed chromatins and highly condensed chromosomes
7
Q
describe the function of the nucleus
A
holds/stores the genetic information which codes for polypeptides
site of DNA replication
site of transcription producing mRNA
nucleolus makes ribosomes/rRNA
8
Q
describe the structure of a ribosome
A
made of riboisomal RNA and protein - consists of 2 subunits
not a membrane bound organelle
eukaryote - 80S ribosomes
prokaryotes - 70S ribosomes
9
Q
describe the function of a ribosome
A
site of protein synthesis - translation
10
Q
describe the structure of RER
A
3D system of tubules and flattened sacs called cristernae
posses a single membrane with ribosomes embedded w/n it to give a ‘rough’ appearance
11
Q
describe the function of RER
A
provides a large surface area for the synthesis, storage and trasnport of proteins and glycoproteins.
ribosomes synthesis the proteins, proteins are processed, folded, tranported inside RER, packaged into vesicles for transport
12
Q
describe the structure of SER
A
3D system of tubules and cisternae [flattened sacs]
posses a single membrane
13
Q
describe the function of SER
A
provides a large SA for synthesis,storage and transport of lipids and carbohydrates
14
Q
describe the strucutre of golgi apparatus and golgi vesicles
A
stakcs of flattened sacs called cisternae with small membrane sacs called vesicles
more compact compared to SER
15
Q
describe the function of golgi apparatus
A
modifies protein, adds carbohydrates to produce glycoproteins
modifies lipids - adds carbohydrates to make glygolipids
packages proteins/lipids into golgi vesicles
produces lysosomes - type of golgi vesicle
16
Q
describe the function of the golgi vesicle
A
transports proteins/lipids to their required destination
e.g. moves to and fuses with cell surface membrane
ddeliers contents outside cell via exocytosis
17
Q
describe the structure of lysosomes
A
vesicle containing hydrolytic enzymes
18
Q
describe the function of lysosomes
A
to release hydrolytic enzymes to break down/hydrolyse pathogens or worn out cell compoenents
19
Q
describe the structure of mitochondria
A
outer membrane and inner membrane folded into many cristae. has a matrix containing 70S ribosomes and circular DNA
20
Q
describe the function of mitochondria
A
site of aerobic respiration to produce ATP for energy relase e.g. for protein synthesis
21
Q
describe the structure of chloroplasts in plants and algae
A
double membrane organelle with stroma as a aqueous granular jelly like liquid, contains thykaloid membrane, 70S ribosomes, circular DNA, starch granules. has lamella which are thylakoid lining grana. grana are stacks of thykaloid
22
Q
describe the function of chloroplasts in plants and algae
A
absorbs light energy for photosynthesis to produce organic substances
23
Q
describe the structure of cell wall in plants, algae, fungi
A
plants/algea - composed mainly of cellulose
fungi - composed of chitin
24
Q
describe the structure of cell vacuole in plants
A
tonoplast membrane with cell sap inside
25
describe the function of cell vacuole
maintains turgor pressure in the cell to prevent it from wilting.
contains cell sap which stores sugars, amino acids, pgiments and any waste chemicals
26
define what a tissue is
group of specialised cells with a similar structure working together to perform a specific function often with the same origin
27
define what an organ is
aggregations of tissues perfoming specific functions
28
define what an organ system is
groups of organs working together to perform specific functions
29
what are the distinguishing features of prokaryotic cells
cytoplasm lacking membrane-bound organelles so genetic material isn't enclosed in a nucleus-
30
what structures are sometimes prsent in prokaryotic cells
capsule
plasmids
flagella
31
what structures are always present in prokaryotic cells
cell surface membrane
cell wall - contains murein, glycoprotein
cytoplasm
small ribosomes
circular DNA
32
compare and contrast structure of prokaryotic and eukaryotic cells
- membrane bound organelles vs none
- nucleus containing DNA vs free floating DNA, no nucleus
- long and linear DNA, associated w histone proteins vs short and circular DNA
- larger 80S ribosomes vs smaller 70s ribosomes
- cell walls only in plants, algae and fungi containing cellulose or chitin vs cell walls in all cells containing murein and glycoprotein
- no plasmids or capsule somtimes has flagella vs plasmids, flagella and capsule sometimes present
- larger overall size vs smaller overall size
33
explain why viruses are described as acellular and non living
accelular - not made of cells, no cell membrane, cytoplasm, organelles
nonliving - have no metablosim cannot independently move, respire, replicate, excrete
34
describe the general structure of a virus particle
nucleis acids surrounded by a capsid
attachment proteins allow attachment to specific host cells
no cytoplasm, ribosomes, cell wall, cell surface membrane
some surrounded by a lipid envelope e.g. HIV
35
what is magnification
the number of times greater image is than the size of the real object
36
how to calculate magnification
MIA
37
what is resolution
minimum distance apart 2 objects can be to be distinguished as separate objects
38
students should be able to appreciate that there was a considerable period of time during which the scientific community distinguished btwn artefacts and cell organelles
to overcome this, scientists prepared specimens in different ways. if an object was seen with one techinque but not another, it was more likely to be an artefact than an organelle
-
39
compare principles of optical, TEM, SEM
optical - light is focused using glass lenses. the light passes through the specimen and different structures absorb different amounts + wavelengths. it generates a 2D image of a cross section
TEM - electrons are focused using electromagnets. they pass through specimens and denser parts absorb more and appear darker. it generates a 2D image of a cross section
SEM - electrons are focused using electromagnets. they get deflected/bounce off specimen surgace, generating a 3D image of surface
40
compare the limitations of optical, TEM, SEM
opticaal - low resolution due to long wavelength of light, can't see internal structure of organelles or ribosomes. thin specimen. low magnification [x1500], can view living organisms. simple to prep and shows colour
TEM - very high resolution due to short wavelength of electrons, can see internal structures of organelles and ribosomes, very thin specimen, high magnification [x1,000,000], can only view deda, dehydrated specimens as vacuum is used. complex preparation so artefacts often present. doesn't show colour
SEM - high resolution due to short wavelength of electrons, can't see interal structures, specimen doens't need to be thin, high magnification [x1,000,000], can only view dead, dehydrated specimen because vacuum is used, complex preparation so artefacts are often present, doens't show colour
41
describe how the size of an object viewed with an optical microscope can be measured
- line up eyepiece graticule with stage micrometer
- calibrate eyepiece graticule, use stage micrometre to calculate size of division on eyepiece graticule
- take micrometre away and use graticule to measure how many divisions make up the object
- calculate size of object by multiplying number of divisions by size of division
- recalibrate eyepiece graticule at different magnifications
42
describe and explain the principles of cell fractionation
- homogenise tissue using a blender: disrupts cell membrane, breaking open cells and releasing contents/organelles
- place in cold, isotonic, buffered, solution: cold to reduce enzyme activity organelles aren't broken down or damaged, isotonic so water doesn't move in or out via osmosis so cells don't burst, buffered to keep pH constant and prevent enzymes denaturing
- filter homogenate: removes large unwanted debris e.g. whole cells
43
describe and explain the principles of ultracentrifugation
separates organelles in orrder of density/mass
- centrifuge homogenate in tube at high speed
- remove pellet of heaviest organelle and respin supernatant at higher speed
- repeat at increasing speeds until separated out, each time pellet made of lighter organelles
nuclei, chloroplasts/mitochondria, lysosomes, ER, ribosomes
44
describe cytokinesis
cytoplasm and cell membrane divides to form 2 new genetically igentical daughter cells
45
describe interphase
- S phase DNA replicates semi conservatively, leading to 2 chromatids (identical copies) joined at a centromere
- G1/G2 number of organelles and volume of cytoplasm increases, protein synthesis
46
describe mitosis
nucleus divides to produce 2 nuclei with indentical copies of DNA produced by parent cell
47
describe the behavirous of chromosomes and role os spindel fibres in prophase
- chromosomes condense, becoming shorter, thicker appears as 2 sister chromatids jioned by a centromere. nuclear envelope breaks down. centrioles move to opposite poles forming spindle network
48
describe the behaviour of chromosomes and role os spindel fibres in metaphse
spindle fibres attach to chromosomes by their centromeres, chromosomes align along the equator
49
describe the behaviour of chromosomes and role os spindel fibres in anaphase
spinidle fibres shorten/contract, centromere divides, pulling chromatids from each pair to opposite poles of cell
50
describe the behaviour of chromosomes and role os spindel fibres in telophase
chromosomes uncoil becoming longer/thinner, nuclear envelopes reform = 2 nuclei, spindle fibres/centrioles break down
51
why do some eukaryotic cells not undergo cell cycle
within multicellular organisms, not all cells retain ability to divide, only cells that do retain this ability go through a cell cycle
52
explain the importance of mitosis in the life of an organism
parent cell divides to produce 2 genetically identical daughter cells for:
- growth of multicellular organims by increasing cell numbers
- replacing cells to repair damanged tissues
- asexual reproduction
53
describe how tumours and cancers form
mutations in DNA/genes controlling mitosis can lead to uncontrolled cell division
tumour formed if this results in a mass of abnormal cells
malignant tumour - cancerous and can spread
benign tumour - non cancerous
54
suggest how cancer treatments control rate of cell division
some disrupt spindle fibre activity/formation
- chromosomes can't attach to spindle by their centromere
- chromatids can't be separated to opposite poles, no anaphase
- prevents/slows mitosis
some prevent DNA replication during interphase
- can't make 2 copies of each chromosome (chromatids)
- prevents/slows mitosis
55
describe how prokaryotic cells replicate
binary fission
- replication of circular DNA
- replication of plasmids
- division of cytoplasm to produce 2 daughter cells: single copy of circular DNA and variable number of copeis of plasmids
56
describe how viruses replicate
as they are non-living, viruses do not undergo cell division
- attachment proteins attach to complementary receptors on host cells
- inject viral nucleic acid (DNA/RNA) into host cell
- infected host cell replicates virus particles: nucleis aid is replicated, cell produces viral protein/capsid/enzymes, virus assembled then released
57
describe the fluid mosaic modell of membrane structure
molecules are free to move laterally in the phospholipid bilayer
contains phospholipids, proteins, glycoproteins and glycolipids
58
describe the arrangement of components of a cell membrane
phospholipids form a bilayr - fatty acid tails face inwards, phosphate heasd face outwards
proteins: intrinsic proteins span bilayer e.g. channel and carrier proteins, extrinsic proteins on the surface membrane
glycoproteins, glycolipids found on exterior surface
cholesterol bonds to phospholipid hhydrophobic fatty acid tails
59
explain the arrangment of phospholipids in a cell membrane
bilayer with water presnt on either side, hydrophobic tails and hydrophillic heads
60
explain the role of cholesterol in cell membranes
note: not always present
restricts movement of other molecules making up membrane, decreasing fluidity and incrreases rigidity
61
suggest how cell membranes are adapted for other functions
phospholipid bilayer is fluid, membrane can bend for vesicle formation/phagocytosis
glycoproteins/glycolipids act as receptors,antigens involved in cell signalling/recognition
62
describe how movement across membranes accours by simple diffusion
lipid soluble or very small substances move from an area of higher conc. to an area of lower conc. down a conc. gradient across phospholipid bilayer
passive doens't reuiqre energy from ATP/respiration
63
explain the limitaitons imposed by the nature of the phospholipid bilayer
restricts movement of water soluble [polar] and larger substances e.g. Na+/glucose
due to hydrophobic fatty acid tails in the interior of the bilayer
64
describe how movement acorss membranes occurs by facilitated diffusion
polar, slightly larger substances moved down a conc. gradient through specific channel/carrier proteins
passive doens't require energy from ATP
64
explain the role of carrier proteins in facilitated diffusion
shape/charge of protein determines which substances move
carrier proteins facciliate diffusion of slightly larger substances. the complementary substances atttaches to a binding site, protein chages shape to transport substance
65
explaine the role of channel proteins in facilitated diffusion
channel proteins facillitate diffusion of water soluble substances. the hydrophillic pore is filled with water, may be gated: can open/close
66
describe how movement across membranes occurs by osmosis
water diffuses/moves from an area of high water poentital down a water potential gradient through a partially permeable membrane. passive doesn't require energy from ATP
67
what is water poential
a measure of how likely water molecules are to move out of a solution
68
pure distilled water has the maximum possible water potential [0 kPA]
increasing solute conc. decrases water potential
-
69
describe how movement across membranes occurs by active transport
substances move from one area of lower to higher conc. against a conc. gradient, requiring hydrolysis of ATP and specific carrier proteins
70
describe the role of carrrier proteins and importance of hydrolysis of ATP in active transport
- complementary substance binds to specific carrier protein
- ATP binds, hydrolysed into ADP + Pi releasing energy
- carrier protein changes shape, realeasing substancce on side of higher conc.
- Pi relased, protein returns to original shape
71
describe how movement across membranes occurs by co-transport
two different substances bind to and move simultaneously via co-transporter protein [type fo carrier protein]
movement of one substance against its conc. gradient is foten couple with the movement of another down its conc. gradient
72
describe the absorption of sodium ions and glucose by cells lining the mammalian ileum
illustrates co-transport
- NA+ actively transported from epithelial cells to blood by Na+/K+ pump
- establishes a conc. gradient of Na+ (higher in ileum than epithelial cell)
- Na+ enters epithelial cell down its conc. gradient with glucose against its conc. gradient via co-transporter protein
- glucose moves down a conc. gradient into blood via facilitated diffusion
73
state 5 things which affect rate of movement across cell membrane
- increasing SA
- increasing no. of channel/carrier proteins increases rate of F.D AND A.T
- conc. gradient increasing = rate of S.D, F.D and osmosis increases
- increasing water potential increases rate of osmosis
- number of channel/carrier proteins could be a limiting factor if they become saturated
74
explain the adaptations of some specialised cells in relation to the rate of transport across their internal and external membranes
- membrane folded to increase SA
- more protein channels/carriers for FD or AT (carrier proteins only)
- large number of mitochondria = more ATP byb aerobic respiriation for active transport
75
what is an antigen
foreign molecule/protein/glycoprotein/glycolipid which stimulates an immune response leading to production of antibody
76
how are cells identified by the immune system
each type of cell has specific molecules on its surface that identify it. often proteins have a specific teriary structure
77
what types of cells and molecules can the immune system identify
pathogens
cells from other organisms of the same species
abnormal body cells e.g tumours or viral infected cells
toxins released by some bacteria
78
describe phagocytosis of pathogens
- phagocyte attracted by chemicalss/ recognises antigens on pathogen
- phagocyte englufs pathogen by surrounding it with its cell membrane
- pathogen contained in vesicle/phagosome in cytoplasm of phagocyte
- lysosome fuses with phagosome and releases lysozymes (hydrolytice enzymes)
- lysozymes hydrolyse/digest pathogen
79
what is a mitotic index
proportion of cells undergoing mitosis with visible chromosomes
number of cells ungergoind mitosis/total no. of cells in a sample
80
explain how temp affects permeability of cell surface membranes
as temp increases, permeability increases
- phospholipids gain Ek and fluidity increases
- transport proteins denature at high temps as H bonds break, changing tertiary structure
at very lowtemps, permeability increases - ice crystals can form which pierce the cell membrane and incrrease permeability
81
explain how pH affects permeability of cell surface membranes
high or low pH increases permeability so transport proteins denature as H/ionic bonds break, chcanging tertirary structure
82
explain how lipid-soluble solvents e.g. alcohol, affects permeability of cell surface membranes
as conc. increases permeability increases. ethanol may dissolve phospholipid bilayer
83
describe the response of T lymphocytes to a foreign antigen
T lymphocytes recognise aintnngens on surface of antigen presenting cells e.g infected cells, phagocytes, presenting antigens, transplanted cells, tumours cells etc
sepcific helper T-cells with complementary receptors bind to antigen on antigen-presenting cell = activated and divide by mitosis to form clones which stimulate:
. cytotocis T cells - kill infected cells/tumour cells
- specific B cells - humoural response
- phagocytes - engluf pathogens by phagocytes
84
describe the response of B lymphocytes to a foreign antigen
B lymphocytes can recognise free antigens e.g in blood or tissues, not just antigen presenting cells.
- clonal selection:
specific B lymphocyte with complementary receptorbinds to antigens. this is then stimulated by helpter T cells so divides by mitosis to form clones
- some differentiate into B plasma cells = secretes large amounts of antibody
- some differentiate into B memory cells = remain in blood for secondary immune response
85
what are antibodies
quaternary structure proteins (4 polypeptide chains) secreted by B lymphocytes e.g. plasma cells in response to specific antigens which bind specifically to antigens forming antigen-antibody complexes
86
describe the structure of an antibody
the 4 chains are found in pairs the longer pair called heavy chains and the shorter pair called light chains. the chains bonded together using disulphide bridges.
there is a constant region and a variable region. the constant region includes the receptor binding site (allows antibodies to bind to WBCs and other antibodies) [end of stem] and the seqeunce of the amino acids is the same in all antibodies.
the varriable region is where the sequence of amino acids is unique in all antibodies. the sequence dictates the shape of the antigen binding sites.
constant is the stem bit of Y and the variable is the branches of Y
87
explain how antibodies lead to the destruction of pathogens
antibodies bind to antigens on pathogens forming an antigen-antibody complex - specific tertiary structure so binding site/variable region binds to complementary antigen
each antibody binds to 2 pathogens at a time causing agglutination of pathogens
antibodies attract phagocytes, phagocytes bind to the antibodies and phagocytose many papthogens at once
88
explain the differences btwn the primary and secondary immune response
primary: first exposure to antigen
- antibodies produced slowly at a lower conc.
- takes time for specific B plasma cells to be stimulated to produce specific antibodies
- memory cells produced
secondary: second exposure to antigen
- antibodies produced faster at a higher conc.
- B memory cells rapidly undergo mitosis to produce many plasma cells which produce specific antibodies
89
what is a vaccine
injection of antigens from attenuated pathogens stimulating formation of memory cells
90
explain how vaccines provide protection to individuals against disease
- specific B lymphocyte with complementary receptor binds to antigen
- specific T helper cell binds to sntigen-prsenting cell and stimulates B cell
- B lymphocyte divides by mitosis to form clones
- some differentitate into B plasma cells which releases antibodies
- some differentiate into B memory cells
- on secondary exposure to antigen, B memory cells rapidly divide by mitosis to produce B plasma cells
- these release antibodies faster and at a higher concentration
91
explain how vaccines provide protections for populations against disease
herd immunity = large proportion of population vaccinated reducing spread of pathogen
- large proportion of population immune so do not become ill from infection
- fewer infected people to pass pathogen on/unvaccinated people less likely to come in contact with someone with disease
92
describe the differences btwn active and passive immunity
- initial exposure to antigen e..g vaccine or primary infection vs no exposure
- memory cells invovled vs none
- antibody produced and secreted by B plasma cells vs antibody introduced from another organism
- slow, takes longer to develop vs faster acting
- long term immunity as antibody can be produced in response to a specific antigen again vs short term immunity as antibody hydrolysed
93
explain the effect of antigen variability on disease and disease prevention
antigens on pathogens change shape/tertiary structure due to gene mutations (creating new strains) so no longer immune (from vaccine or prior infection)
- B memory cell receptors cannot bind to/recognise changed antigen onsecondary exposure
- specific antibodies not complementary/cannot bind to changed antigen
93
describe the structure of HIV particle
2 RNA strands including the enzyme reverse transcriptase surrounded by a capsid with a lipid envelope with attachement proteins on it
94
describe the replication of HIV in helper T cells
HIV attachment proteins attach on receptors on helper T cell
Lipid envelope fuses with cell-surface membrane, releasing capsid into cell
Capsid uncoats, releasing RNA and reverse transcriptase
Reverse transcriptase converts viral RNA to DNA
viral DNA inserted/incorporated into helper T cell DNA (may remain latent)
Viral protein/capsid/enzymes are produced
- DNA transcribed into HIV mRNA
- HIV mRNA translated into new HIV proteins
Virus particles assembled and released from cell (via budding)
95
Explain how HIV causes the symptoms of AIDS
HIV infects and kills T helper cells as it multiplies rapidly
- T helper cells can't stimulate cytotoxic T cells, B cells and phagocytes
- B plasma cells can't release as many antibodies for agglutination and destruction of pathogens
Immune system deteriorates becoming more susceptible to infections, pathogens reproduce, release toxins and damage cells
96
explain why antibodies are ineffective against viruses
viruses do not have structures/processe that antibodies inhibit:
- no metabolic processes e.g. no ribosomes
- no bacterial enzymes or a murein cell wall
97
what is a monoclonal antibody
antibody produced from genetically indentical/cloned B lymphocytes/plasma cells so have the same tertiary structure
98
explain how monoclonal antibodies can be used in medical treatments
- monoclonal antibody has a specific tertiary structure/binding site/variable region
- complementary to receptor/protein/antigen found on only a specific cell type
- therapeutic drug attached to antibody
- antibody binds to sepcific cell, forming antigen-antibody complex, delivering drug
some are also designed to block antigens/receptors on cells
99
explain how monoclonal antibodies can be used in medical diagnosis
- monoclonal antibody has a specific tertiary structure/binding site/variable region
- complementary to specific receptor/protein/antigen assiciated with diagnosis
- dye/stain/fluorescent marker attached to antibody
- antibody binds to receptor/protein/antigen forming an antigen-antibody complex
100
explain the use of antibodies in the direct ELISA (enzyme-linked immunosorbent assay) to detect antigens
attach sample with potential antigens to well and add complementary monoclonal antibodies with enzymes attached, bind to antibodies if present. wash well, remove unbound antibodies to prevent false positives. add substrate - enzymes create rpoducts that cause a colour change
101
explain the use of antibodies in the sandwich ELISA (enzyme-linked immunosorbent assay) to detect antigens
attach specific monoclonal antibodies to well, add sample with potential antigens then wash well. add complementary monoclonal antibodies with enzymes attached, bind to antigens if present. wash well to removed any unbound antibodies to prevent a false positive. add substrate - enzymes create productts that cause a colour change
102
explain the use of antibodies in the indirect ELISA test to detect antibodies
indirect
attach specific antigens to well, attach sample with potential antibodies, wash well. attach complementary monoclonal antibodies wwith anzymes attached will bind to antibodies if present. wash well to remove unbound antibodies. add substrate - enxymes create products that cause a colour change.
103
suggest the purpose of control well in the ELISA test
compare to test to show only enzyme causes colour change and to show all unbound antibodies have been washed away
104
discuss some general ethical issues associated with the use of vaccines and monoclonal antibodies
- preclinical testing on animals = potential harm, stress, mistreatment. but aniamsl aren't killed and helps to produce drugs which reduce human suffering
-
105
suggest some points to consider when evaluating methodology relating to use of vaccines and monoclonal antibodies
- was the sample size large enough to be representative
- were participants diverse in terms of age, sex, ethinicty and health status
- were placebo, control groups used for comparison
- was duration of study long enough to show long term effects
- was trial double blind to reduce bias
106
suggest some points to consider when evaluating evidence and data relating to the use of vaccines and monoclonal antibodies
- what side effects were observed and how frequent
- was a statisstical test done to see if there was significant different btwn start and final results
- was standard deviation of final results large, showing some people didn't benefit, did they overlap = no significant benefit
- was dosage optimum and does incrreasing does increase effectiveness to justify cost
- was cost of production and distribution low enough
107
what is a pathogen
microorganism that causes disease
108
what is an antigen
a specific protein ont he surface of a pathofen that allows our immune system to identify it as a foreign material e.g. non self
109
what is a phagocyte
a WBC that englufs forreign materia, neutralises it via hydrolysis and presents antigens on it's own cell membrane
110
what is a lymphocyte
a WBC that once activated, differentiates into different types of T cells and B cells
111
what are antibodies
a y shaped protein produced by plasma cells that bind to and neutralise pathogens and their toxins
112
what are memory cells
differentiated T cell and B cells that persist in our circulatory and lymphatic systems, ready to be activated upon a secondary infection
113
what is immunity
the ability of an organism to resist infection due to the production of a seconday immune response which deals with the infection before symptoms can develop
114
what are the two types of defence mechanisms and sub 4 groups
non specific response (immediate response same for all pathogens) -> physical (prevents entry of pathogen) and phagocytosis
specific response (slower as its 'tailor-made' for specific pathogens so its stronger) -> cell mediated (attacks pethogens directly) and humoural (antibodies)
115
explain some examples of the non specific immune response
- skin acts as a hysical barrrier. gut and skin flora compete for food and space
- mucus membranes are bathed in secretions that possesses antimicrobial properties that destroy pathogens. lysozymes can be found.
- ciliated epithelial and goblet cells secrete mucus which pathogens a re caught in. cilia waft the mucus and pathogen up to be swallowed to stomach
- hydrochloric acid in the stomach has a low pH which denatures pathogen's enzymes
116
what two cells carry out phagocytosis
neutrophils and macrophages
117
what are neutrophils
a short lived cell which can be found in the blood. they combat small infections or the intial infection
attacks the pathogen itself
118
what are macrophages
they are larger than neutrophils and live longer. they are better at combating larger infections. can be found in organs rather than blood.
helps pathogen to present antigens which means that lympohocytes can recognise them
119
