Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

aqa bio > 3.2 cells > Flashcards

3.2 cells Flashcards

You may prefer our related Brainscape-certified flashcards:
Biology 101 flashcards
1
Q

State the sub-cellular structures inside a eukaryotic cell

A

Cell surface membrane
Nucleus
Mitochondria
Chloroplast
Golgi apparatus and Golgi vesicles
Lysosomes
Ribosomes
Rough er (endoplasmic reticulum)
Smooth er (endoplasmic reticulum)
Cell wall
Cell vacuole

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Structure of nucleus

A

Nuclear envelope - double membrane surrounding nucleus
Nuclear pores - large protein complexes that allow molecules in and out of nucleus
Nucleoplasm - granular, jelly like material that is similar to the cytoplasm but inside nucleus
Nucleolus - smaller sphere inside, site of rRNA production and makes ribosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Structure of cell wall

A

3 main sections of cell wall:
Middle Lamella - contains polysaccharides which help bind cell together
Primary cell wall - with cellulose microfibrils that provide strength and flexibility for growth
Secondary cell wall - may contain lignin, which strengthens cell and aids water conductivity

in plants: made of microfibrils of the cellulose polymer
in fungi: made of chitin, a nitrogen containing polysaccharide

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Function of nucleus

A

Controls cell growth and division. (also carries genetic code of the cell when it divides)
site of DNA replication and transcription (making mRNA)
contains genetic code for each cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Function of cell wall

A

Provides mechanical strength in order to prevent the cell bursting under the pressure created by the osmosis of water entering the cell
To allow water to pass along it and therefore to contribute to the movement of water through the plant

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

structure of plasma membrane

A

found in all cells
phospholipid bilayer - molecules embed within and attached on the outside (proteins, carbohydrates, cholesterol)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

function of plasma membrane

A
  • controls the entrance and exit of molecules
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Structure of cell vacoule

A

Fluid filled sac
surrounded by single membrane: tonoplast

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Function of cell vacuole

A

makes cells turgid and therefore provides support
temporary food store of sugars and amino acids
Pigments may colour petals to attract pollinators

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

structure of mitochondria

A

double membrane - controls what goes in and out
inner membrane - cristae
fluid centre called mitochondrial matrix - space containing lipids, proteins, enzymes and circular DNA to make own proteins
loop of mitochondria DNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

function of mitochondria

A

site of aerobic respiration
site of ATP production
DNA to code for enzymes needed in respiration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

chloroplasts structure

A

surrounded by double membrane
thylakoids - folded membranes embedded with pigment
fluid filled stroma - contains enzymes for photosynthesis
found in plants

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

chloroplasts function

A

site of photosynthesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

virus facts

A

non living
have receptor proteins which attach to proteins on other cells and infect them

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

magnification equation

A

magnification = size of image/ size of a real object

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

define magnification

A

how many times bigger the image is than the specimen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

define resolution

A

minimum distance apart that two objects can be in order for them to appear as separate items

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what is cell fractionation

A

its used to collate different organelles so they can be studied

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

how does cell fractionation work

A

cells are broken down to release content and organelles are then separated
must be prepared in a cold, isotonic, buffered solution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

why does the cell need to be prepared in a cold isotonic buffered

A

cold - reduces enzyme activity
isotonic - dont want organelles to be damaged so must be in the same concentration
buffered - has a buffer to prevent damage to the organelles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

steps for fractionation

A
  1. homogenization
    - cells must be broken open so in order to do that we use a blender to blend it into a cold, isotonic buffered solution
  2. ultracentrifiguration
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

structure of ribosomes

A

free in cytoplasm or attached to ER
two types : small and large
made up of two subunits of protein and rRNA
large ribosome found in eukaryotic cells
smaller ribosome found in prokaryotic cells, mitochondria and chloroplasts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

function of ribosomes

A

site of protein synthesis (where amino acids are joined together to form a polypeptide)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

structure of smooth and rough er

A

both have folded membranes called cisternae
rough = membranes on the cisternae
rough ER - protein synthesis
smooth ER - synthesis and store lipids and carbohydrates

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

function of smooth and rough er

A

synthesis, storage and transport of proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

function of nuclear pores

A

allows passages of large molecules e.g RNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

structure of golgi apparatus

A
  • folded membranes making cisternae
  • secretary vesicles pinch off from the cisternae
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

function of nuclear envelope

A

controls entry and exit of materials in and out of nucleus and reactions taking place within it

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

function of golgi vesicle

A

stores lipids and proteins made by golgi apparatus and transports them out of the cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

functions of golgi apparatus

A
  • adds carbohydrates to proteins to form glycoproteins
  • produce secretory enzymes
  • secrete carbohydrtes
  • transport, modify and store lipids
  • form lysosomes
  • molecules are ‘labelled’ with their destination
  • finished products are transported to cell surface in Golgi vesicles where they fuse with the membrane and the contents in released
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

strucure of lysosome

A

tiny bag of digestive enzymes, surrounded by single membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

function of lysosomes

A
  • hydrolyse phagocytic cells
  • completely breaks down dead cells
  • exocytosis - releases enxymes to outside of cell to destroy material
  • digests worn out organelles for reuse of materials
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

structure of plasmid

A

small loops of DNA which only carry a few genes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

structure of capsule

A

slimy layer made up of protein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

function of capsule

A

prevents bacteria from desiccating (drying out) and protects the bacteria against the host’s immune system

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

calculate the length of time in a stage of cell division

A

length of time in stage= (observed number of cells in this stage/total number of cells) x total length of cell cycle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

in what stage of the cell cycle does DNA replication occur

A

interphase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

what part of the cell is mitosis

A

when a eukaryotic cell divides to produce two daughter cells, each with identical copies of DNA produced by the parent cell during DNA replication

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

order of stages in mitosis

A

interphase
prophase
metaphase
anaphase
telophase
(cytokinesis)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

what happens in interphase

A
  • cell grows
  • DNA replicates
  • prepares for cell division
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

what happens in prophase

A
  • chromosomes become visible by shortening and thickening
  • centrioles replicate and move to opposite ends of cells (called poles)
  • spindle fibres develop and collectively they’re called spindle apparatus
  • nucleolus disappears
    -nuclear envelope breaks down
  • chromosomes now free in cytoplasm
  • chromosomes drawn towards equator by spindle fibres that are attached to the centromere
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

what happens in metaphase

A
  • chromosomes made up of two chromatids
  • each chromatid is an identical copy of DNA from the parent cell
  • chromatids joined by centromere
  • spindle fibres (microtubules) from poles attach to the centromere
  • chromosomes pulled along spindle apparatus and arrange themselves across the equator of the cell
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

what happens in anaphase

A
  • centromeres divide into 2 and spindle fibres pull individual chromatids apart
  • chromatids move to their respective sides of the cell
  • now referred to as ‘chromosomes’
  • energy to separate them comes from ATP (respiration)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

what happens in telophase

A
  • chromosomes reach their respective poles and become longer and thinner
  • this makes them invisible again
  • the spindle fibres disintegrate
  • nuclear envelope and nucleolus reform
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

what happens in cytokinesis

A
  • cytoplasm divides forming two identical cells
  • parent cell separate into two genetically identical daughter cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

importance of mitosis

A
  • growth
  • repair: if cells become damaged or die, it’s important for the new cells produced to have an identical structure and function to those that have been lost
  • reproduction: single celled organisms divide by mitosis to give two new organisms. each new organism is genetically identical to parent organism
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

difference between mitosis and meiosis

A
  • mitosis: produces 2 daughter cells that have the same number of chromosomes as the parent cell
  • meiosis: produces 4 daughter cells, each with half the number of chromosomes of the parent cell.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

what can happen if mitosis goes wrong

A
  • mitosis is a controlled process
  • if the cell division becomes uncontrolled then it can lead to formation of tumours and cancers. many cancer treatments are directed at controlling the rate of cell division
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

reproduction in prokaryotic cells

A

binary fission:
- circular DNA replicates and both copies attach to the cell membrane
- plasmids also replicate
- cell membrane begins to grow between the 2 DNA molecules and begin to pinch inward, which divides the cytoplasm into 2
- new cell wall forms between the molecules of DNA, which divides the original cell wall into two identical daughter cells
- each have a single copy of the circular DNA and variable number of copies of the plasmids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

cell replication in viruses `

A
  • viruses don’t undergo cell division because they’re non living.
  • if the viruses inject a host cell with their infected nucleic acid, the host cell becomes infected and replicates the virus particles
51
Q

what is the cell membrane composed of

A
  • transport proteins
  • phospholipid heads
  • glycolipids
  • cholesterol
  • cytoskeleton filaments
52
Q

structure of phospholipds in the cell- surface membrane

A
  • hydrophillic heads of both layers point to the outside of the membrane as it’s attracted to the water on both sides
  • hydrophillic tails point to centre of membrane, repelled by water on both sides
53
Q

function of phospholipids in the cell- surface membrane

A
  • allow lipid soluble substances to enter and leave the cell
  • prevents water-soluble substances entering and leaving the cell
  • makes the cell flexible and self sealing
54
Q

structure of proteins in the cell-surface membrane

A
  • interspersed throughout the cell-surface membrane
  • some proteins occur in the surface of the bilayer, they act as mechanical support to the membrane
  • other proteins completely span the phospholipid bilayer from one side to the other. some are protein channels, which form water-filled tubes to allow water-soluble ions to diffuse across the membrane.
  • others are carrier proteins that bind to ions or molecules like glucose etc, then change shape in order to move these molecules across the membrane.
55
Q

function of proteins in the cell- surface membrane

A
  • provides structural support
  • acts as channels transporting water-soluble substances across the membrane
  • allow active transport across the membrane through carrier proteins
  • form cell-surface receptors for identifying cells
  • helps cells adhere together
56
Q

structure of cholesterol in the cell-surface membrane

A

-occur within the phospholipid bilayer of the cell-surface membrane
-they add strength to the membranes
- cholesterol molecules are very hydrophobic- play a role in preventing loss of water and dissolved ions from the cell
- also pull together fatty acid tails of the phospholipid molecules, limiting their movement and that of other molecules without making the membrane too rigid

57
Q

function of cholesterol in the cell-surface membrane

A
  • reduce lateral movement of other molecules including phospholipids
  • make the membrane less fluid at high temperatures
  • prevent leakage of water and dissolved ions from the cell
58
Q

structure of glycolipids in the cell-surface membrane

A
  • extends from the phospholipid bilayer into the watery environment outside the cell.
59
Q

function of gylcolipids in the cell-surface membrane

A
  • acts as recognition sites
  • help maintain the stability of the membrane
  • helps cells to attach to one another and so form tissues
60
Q

structure of glycoproteins in the cell-surface membrane

A
  • outer surface of membrane
  • acts as cell surface receptors for more specifically hormones and neurotransmitters
61
Q

function of glycoproteins in the cell-surface membrane

A
  • acts as cell-cell recognition sites
  • helps cells to attach to one another and so form tissues
  • allows cells to recognise one another, e.g lymphocytes can recognise an organism’s own cells
62
Q

why is the model for the cell surface membrane called the fluid mosaic

A
  • ‘fluid’ cause the molecules move around each other in the membrane and gives it a flexible structure that is constantly changing in shape
  • ‘mosaic’ cause the molecules of different shapes and sizes fit together to form a pattern like a mosaic
63
Q

functions of membranes within cells

A
  • control entry and exit of materials in discrete organelles e.g mitochondria
  • separate organelles from cytoplasm so that specific metabolic reactions can take place within them
  • provide an internal transport system e.g E.R
  • isolate enzymes that might damage the cell e.g lysosomes
  • provide surfaces on which reactions can occur e.g protein synthesis on ribosomes on rough E.R
64
Q

why don’t some molecules pass through the membrane

A
  • not soluble in lipids and therefore cannot pass though the phospholipid layer
  • too large to pass through the channels in membrane
  • are the same charge as the charge on the protein channels so they are repelled
  • electrically charged (polar) and therefore have difficulty passing through the non-polar tails in the phospholipid bilayer
65
Q

diffusion definition

A

the net movement of molecules or ions from a region of high concentration to a region of lower concentration until a dynamic equilibrium is achieved. (down a concentration gradient)

66
Q

what type of process is facilitated diffusion

A

passive

67
Q

why is diffusion a passive process

A
  • cell doesn’t use its ATP to move molecules or ions - they move due to kinetic energy
68
Q

what type of molecules pass between the phospholipids in simple diffusion

A
  • small, uncharged molecules
    e.g oxygen, carbon dioxide

exception = water

69
Q

why don’t some molecules pass through the cell membrane in facilitated diffusion

A
  • they aren’t lipid soluble
  • too large
  • have a charge e.g ions and polar molecules
70
Q

how can molecules pass through the membrane in facilitated diffusion

A
  • they will only pass across the membrane if there is a complementary shaped protein to facilitate its transport e,g channel proteins and carrier proteins
71
Q

two types of proteins that are in the plasma membrane

A
  • carrier proteins
  • channel proteins
72
Q

role of channel proteins

A
  • have a water filled hydrophilic channel through which ions can pass
  • allow specific water-soluble ions to pass through, if specific ion isn’t present, the channel remains closed.
73
Q

role of carrier proteins

A
  • can change shape when a specific molecule binds and the molecule is then released on the other side of the membrane
74
Q

osmosis definition

A

passage of water from a region of higher water potential to a region of lower water potential through a partially permeable membrane until a dynamic equilibrium is reached

75
Q

pure water, water potential =

A

0

76
Q

how will addition of a solute to pure water affect the water potential

A

lower its water potential (into negatives)

77
Q

how will water move in osmosis - in terms of water potential

A

from a region of higher (less negative) water potential to a region of lower (more negative) water potential
e.g -20kPa –> -30kPa

78
Q

the higher the value of the water potential…

A

the more pure the solution is (means there is more solute in the solution)

79
Q

what do antigens allow the immune system to identify:

A

pathogens
abnormal body cells
toxins
cells from other organisms of the same species e.g organ transplant, blood transplant

80
Q

antigen definition

A

a molecule that triggers an immune response by lymphocytes

81
Q

what is antigenic variation

A
  • when a pathogen mutates frequently, so its antigens change suddenly rather than gradually.
  • this means that new antigens on the pathogen are no longer recognised by the immune system and therefore new strains of pathogens become created
82
Q

how does antigenic variation effect disease prevention

A
  • mutations mean that antigens on the pathogen change suddenly.
  • this means that vaccines become ineffective because the new antigens on the pathogens are no longer recognised by the immune system
  • so the immune system cannot produce the antibodies needed to destroy the pathogens
83
Q

examples of a virus that experiences antigenic variability

A

influenza virus (flu) and HIV

84
Q

process of phagocytosis

A
  • phagocyte moves towards pathogen along a concentration gradient
  • pathogen engulfed by endocytosis
  • pathogen now contained within phagosome (phagocytic vacuole)
  • lysosomes fuse with phagosome to form a phagolysosome
    -lysozymes break down pathogen
  • waste products excreted by cell via exocytosis
  • phagocytes can then present the pathogens antigens by sticking it to its own cell surface becoming an antigen presenting cell.
85
Q

role of lysozymes in the destruction of pathogens

A
  • lysozymes are present within the lysosome and they destroy ingested bacteria by hydrolysis of their cell walls.
86
Q

how are antigen presenting cells formed

A
  • when a phagocyte engulfs a pathogen, it doesn’t always fully digest it
    -antigen from surface of the pathogen is saved and moved to a special protein complex on surface of cells
  • cell is now an APC
  • exposes antigen on surface so that other cells of immune system recognise the antigen
  • special protein complex ensures that APC isn’t mistaken for foreign cell and attacked.
87
Q

specific immune response definition

A

specific or adaptive immune response can target a specific pathogen slower than a non specific response

88
Q

what does the cell mediated (cellular) response involve

A
  • involves specialised T-cells and other immune cells that they react with e.g phagocytes - target pathogens inside cells
89
Q

process of a cell mediated response

A
  1. once a pathogen has been engulfed and destroyed by a lysozmes, the antigens get positioned on the cell surface. this is now an APC
  2. T helper cells have receptors on their surface which can attach to the antigens on APC
  3. once attached, this activates the helper T cells to divide by mitosis to replicate and make large numbers of clones
  4. cloned helper t cells differentiate into different cells. some become cytotoxic T cells
  5. t helper cells release cytokines to stimulate cytoxic t cells
  6. cyotoxic t cells detect antigen on surface of infected cell, and once detected, they release perforin which creates pores in the cell membrane
  7. in addition enzymes are also released which get into the cell and destroy the infected cell
90
Q

role of cytotoxic T cells

A

to destroy abnormal or infected cells by releasing perforin. this protein creates pores in the cell surface membrane which causes the cell to shrivel or lyse

91
Q

purpose of helper t cells

A

they divide by mitosis to become more helper T cells which stimulate B cells and phagocytosis, or T memory cells or cytotoxic T cells

92
Q

examples of APCs

A
  • infected body cells will present the viral antigen on their surface
  • a macrophage which has engulfed and destroyed a pathogen will present the antigen on their surface.
  • cells fo a transplanted organ will have different shaped antigens on their surface compared to your self-cell antigens
  • cancer cells will have abnormal shaped self-cell antigens
93
Q

structure of an antibody

A
  • consists of 4 polypeptide chains - 2 identical light chains and 2 identical heavy chains
  • disulphide bonds hold the 4 polypeptide chains of antibody together
  • constant region is the long part that isn’t on the end
    -antigen binding site enables antibody to bind to specific antigen on a pathogen
    -quarternary structure protein
94
Q

formation of an antigen-antibody complex

A
  • An antigen and its complementary antibody have complementary molecular shapes
  • when antibody collides with a foreign cell that posesses ‘non-self’ antigens with a complementary shape, it binds with one of the antigens
  • therefore, 2 molecules combine (Antigen + antibody) to form an antigen-antibody complex
95
Q

what is involved in the humoral response

A

b cells and antibodies

96
Q

humoral immune response process

A
  • b cell binds to specific antigen on antigen presenting cell
  • t helper cell releases cytokines to stimulate b cells to divide by mitosis ( clonal expansion)
  • b cells differentiate into plasma cells which secrete antibodies with complementary variable region to the antigen
  • plasma cells develop memory cells
97
Q

memory b cells

A
  • can live for decades inside body
  • memory b cells don’t make antibodies, rather they will divide by mitosis and make plasma cells rapidly if they collide with an antigen they have previously encountered.
  • this results in large numbers of antibodies being produced so rapidly that the pathogen is destroyed before any symptoms can occur.
98
Q

clonal expansion

A
  • APC stimulates helper T cell to produce chemical message. Message activates the B cells - called clonal selection
  • activated B cells divide to form plasma cells
  • plasma cells undergo rapid division, called clonal expansion then produces required antibody in large quantities
99
Q

what is a monoclonal antibody

A

a single type of antibody that can be isolated and cloned

100
Q

primary immune response

A
  • when an antigen enters the body for the first time, the immune system is activated (primary response)
  • primary response is slow and weak cause there aren’t many B-cells that can make the antibody needed to bind to the specific antigen
  • after 1st infection, T and B cells produce memory cells that remain in the body
  • person is now said to be immune cause immune system has the ability to respond quickly to pathogen
101
Q

secondary immune response

A
  • if the same pathogen enters the body again, the immune system will produce a quicker and stronger immune response (secondary response)
  • clonal selection happens faster
  • memory B cells activated, divide into plasma cell to produce specific antibody to antigen
  • secondary response often gets rid of pathogen before you display any symptoms
102
Q

role of cytotoxic t cells

A

produces perforin that causes pathogen infected cells to lyse

103
Q

role of plasma cell

A

generates large quantities of antibodies

104
Q

agglutination definition

A

when antigens bind to other antigens on surface of several pathogens, clumping them together
phagocytes can now easily recognise and easily destroy pathogen by phagocytosis

105
Q

cellular vs humoural immune response

A

cellular:
- targets pathogens in host cell
- involves cytotoxic T cells
- perforin causes cell to lyse

humoral:
- produces antibodies
- involves plasma cells
- can neutralise pathogens

both:
- coordinated bt helper t cells
- interleukin acts as cell signaller
- involves APC

106
Q

passive immunity definition

A

produced by introduction of antibodies into individuals from an outside source

107
Q

active immunity definition

A

produced by stimulating the production of antibodies by the individual’s own immune system

108
Q

examples of natural active and artificial active immunity

A

natural active: chicken pox
artificial active: vaccinations

109
Q

examples of natural passive and artifical passive immunity

A

natural passive: acquiring antibodies from their mother e.g breast milk and across the placenta
artificial passive: injection of rabies antibodies after potential exposure

110
Q

how can antigens be used to produce a vaccine

A
  • same antigens that are found on the surface of a known pathogen and stimulate the primary response, resulting in production of memory B cells
  • may contain attenuated (less virulent) form of the pathogen
111
Q

how are vaccinations used to protect against diseases caused by particular pathogens

A
  • vaccinations are the introduction of the appropriate disease antigens into the body.
  • intention is to stimulate an immune response against a particular disease
  • vaccine contains one or more types of antigen from the pathogen
  • antigens stimulate immune response
  • memory cells are then produced and these remain in the blood and allow a quicker and stronger response to a future pathogen of this same pathogen
  • the result is that there is a rapid production of antibodies and the new infection is rapidly overcome before it can cause any harm and with few symptoms or none at all
112
Q

herd immunity concept

A

if enough people in a population are vaccinated against a disease, it’s not possible for the disease to spread amongst the population, so everyone is protected
reduced chance of passing it on if more people are vaccinated

113
Q

importance of herd immunity

A

it isn’t ever possible to vaccinate the entire population e.g babies and very young children aren’t vaccinated because their immune system aren’t fully functional
could also be dangerous to vaccinate those who are ill or have compromised immune systems.

114
Q

ethical issues associated with use of vaccines

A
  • production of existing vaccines and development of new ones often involving the use of animals. how acceptable is this
  • on whom should vaccines be tested on
115
Q

structure of HIV

A
  • core of genetic information, RNA, and some proteins
  • outer coating of protein called a capsid
  • capsid encloses 2 single strands of RNA and some enzymes (one enzyme is reverse transcriptase - catalyses production of DNA to RNA)
  • extra outer layer called a (lipid) envelope
  • attachment proteins on surface
116
Q

HIV replication

A
  1. Attachment proteins attach to receptors on helper T cell/lymphocyte;
  2. Nucleic acid/RNA enters cell;
  3. Reverse transcriptase converts RNA to DNA;
  4. Viral protein/capsid/enzymes produced;
  5. Virus (particles) assembled and released (from cell);
117
Q

difference between being HIV positive and developing AIDS

A
  • once infected with HIV, a person is said to be HIV positive.
  • however, the replication of HIV often goes into dormancy and only recommences leading to AIDS many years later
  • HIV develops into AIDS when the helper t-cell numbers in their body reach a critically low level
118
Q

how does HIV cause the symptoms of AIDS

A
  • HIV specifically attacks helper T cells. HIV causes AIDS by killing or interfering with the normal functioning of helper T cells.
  • without a sufficient number of helper T cells, the immune system cannot stimulate B cells to produce antibodies or the cytotoxic T cells that kill cells infected by pathogens .
  • memory cells also become infected and destroyed
  • as a result, the body is unable to produce the adequate immune response and becomes susceptible to other infections or cancers
119
Q

why are antibiotics ineffective against viruses

A
  • viruses don’t have their own enzymes and ribosomes - they use the ones in the host cells
  • antibiotics disrupt cell structures and metabolic mechanisms so because viruses use human enzymes, ribosomes etc to replicate, antibiotics can’t inhibit them
  • viruses also have a protein coat rather than a murein cell wall and so do not have the sites where antibiotics can work.
  • most antiviral drugs are designed to target the few virus specific enzymes that exist
    e.g HIV uses reverse transcriptase to replicate. Human cells don’t have this enzyme so drugs can be designed to inhibit it without affecting human cells - reverse transcriptase inhibitors
120
Q

how are monoclonal antibodies used in medical diagnosis

A

cancer drug delivery:
- cancer cells have antigens called tumour markers that aren’t on normal body cells
- monoclonal antibodies can be made that are specific to the antigens on the cancer cells (tumour markers) and will bind to them
- these antibodies are given to a patient and attach themselves to the receptors on their cancer cells
- attach to the surface of their cancel cells and block the chemical signals that stimulate their uncontrolled growth

121
Q

use of monoclonal antibodies in pregnancy tests

A
  • this test detects the hormone hCG that is found in urine of pregnant women
  • application area contains antibodies that are complementary to the hCG protein, which are bound to the coloured bead
  • when urine is applied to the application area, hCG will bind to the antibodies on the beads, forming an antigen- antibody complex
  • urine moves up the test strip, carrying any beads with it
  • test strip contains antibodies to hCG that are immobilised
  • if theres hCG present, strip turns blue, immobilised antibody binds to any hCG concentrating the hCG - antibody complex with the blue beads attached
122
Q

use of ELISA

A
  • allows you to see if a patient has any antibodies to a certain antigen or any antigen to a certain antibody
  • can be used in medical diagnosis to test for pathogenic infection e.g HIV or for allergies and anything else
  • if a colour change is present in an ELISA test, it demonstrates that the antigen or antibody of interest is present
123
Q

process of indirect ELISA

A
  • HIV antigen bound to the bottom of the well
  • plasma sample is added
  • if any HIV specific antibodies in plasma, these will bind to the HIV antigen stuck to the bottom of the well
  • well is then washed to remove unbound antibodies
  • secondary antibody is added
  • secondary antibody can bind to the HIV specific antibody
  • well washed again which removes secondary unbound antibody
  • if no primary antibody is present, all of the secondary antibody is washed away
  • substrate added
  • this is able to react with the enzyme attached to the secondary antibody and produce a coloured product
  • if solution changes colour, it indicates patient has HIV specific antibodies in blood
124
Q

ethical considerations of using monoclonal antibodies

A
  • monoclonal antibody therapy, animal rights issue
  • animals used to produce cells from which monoclonal antibodies are produced

aqa bio (5 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions