CHAPTER 2 - CELLS Flashcards

Question

describe the appearance and function of the ribosome

Answer 1

appearance - very small organelle - floats free in cytoplasm OR attached to RER - made of proteins and RNA - NOT surrounded by membrane function - site of protein synthesis

Answer 2

appearance - system of membranes enclosing a fluid filled space - surface is covered with ribosomes function - folds and processes proteins that have been made at ribosomes

Answer 3

appearance - similar to RER, but no ribosomes function - synethesises and processes lipids

Answer 4

appearance - rigid structure that surrounds cells in plants, algae and fungi - in plants and algae its mainly made of cellulose - in fungi its made of chitin function - supports cells and prevents them from changing shape

Answer 5

appearance - membrane bound organelle - found in cytoplasm - contains cell sap, a weak solution of sugar and salts - membrane surrounding it is called a 'tonoplast' function - helps to maintain pressure inside cell - keeps cell rigid - stops plant from wilting - involved in isolating unwanted chemicals in the cell

Answer 6

specialisation

Answer 7

in the small intestine and are adapted to absorb food efficently - walls of small intestine have lots of villi (finger like projections) = increase SA for absorption - villi have folds called microvilli = further increase SA - lots of mitochondria = provide energy for transport of digested food molecules into cell

Answer 8

adapted to carry oxygen around the body no nucleus = more room for haemoglobin, which carries oxygen

Answer 9

have to propel themselves to an egg have lots of mitochondria to provide energy to travel

Answer 10

specialised cells -> tissues tissues -> organs organs -> organ system tissues = group of cells working together to perform a certain function

Answer 11

epithelial cells -> epithelial tissue epithelial tissue, muscular tissue and glandular tissue work together to form the stomach, which is an organ stomach is part of the digestive system - organ system made of all organs involved in digestion and absorption of food, includes small and large intestine and liver

Answer 12

they are single celled organisms

Answer 13

bacteria like E. Coli

Answer 14

murein glycoprotein, protein with carbohydrate attached

Answer 15

appearance - long hair like structure - not all prokaryotes have one, some have multiple function - makes prokaryotes move

Answer 16

- dont have a nucleus - DNA floats free in the cytoplasm - circular DNA presents as one long coiled up strand - DNA not attached to any histone proteins

Answer 17

appearance - small loops of DNA that aren't part of the main circular DNA molecule - not present in all prokaryotes, while some have multiple function - contain genes for things like antibiotic resistance - can be passed between prokaryotes

Answer 18

appearance - capsule around the cell wall - made of secreted slime - only some have it function - helps to protect the bacteria from attack by cells of immune system

Answer 19

- extremely small - less than 2 hm in diameter - 0.002 mm - eukaryotes can be up to 50x bigger

Answer 20

binary fission cell replicates and makes 2 copies of its genetic material, before splitting into 2 daughter cells

Answer 21

- circular DNA and plasmid/s replicate - main DNA loop only replicated once - plasmid/s can be replicated many times - cells gets bigger - DNA moved to opposite poles/ends of the cell - cytoplasm begins to divide - new cell walls begin to form - cytoplasm divides and 2 daughter cells are produced - each daughter cell has 1 copy of the circular DNA but a variable number of copies of the plasmids

Answer 22

- aceullar = not cells - nucleic acids surrounded by protein - not alive

Answer 23

HIV, causes AIDS influenza, causes the flu rhinoviruses, causes colds

Answer 24

invade and reproduce inside the cells of organisms the cells they invade and reproduce in are called HOST CELLS

Answer 25

core of genetic material, either DNA or RNA (the nucleic acid) attachment proteins capsid/protein coat

Answer 26

even smaller than bacteria 0.1 hm across

Answer 27

magnification = size of image / size of real object

Answer 28

how well a microscope can distinguish between 2 points that are close together

Answer 29

- use light to form an image - max resolution : 0.2 hm - cant use a microscope to see organelles smaller than 0.2 hm : ribosomes, both ER, lysosomes - may be able to see mitochondria, but not in perfect detail - can see nucleus - max magnification : x1500

Answer 30

- use electrons to form an image - have a higher resolution than optical microscopes, therefore gives a more detailed image - max resolution : 0.0002 hm - max magnification : x1500000 - produce black and white images, but this can be turned into coloured by a computer

Answer 31

transmission electron microscope - TEM scanning electron microscope - SEM

Answer 32

- use electromagnets to focus a beam of electrons, which is then transmitted through the specimen - denser parts of the specimen absorb more electrons and therefore those parts look darker on the image produced

Answer 33

- scan a beam of electrons across the specimen - knocks off electrons from the specimen, these are gathered in a cathode ray tube to form an image

Answer 34

- gives high resolution images, so shows small objects

Answer 35

- can be only used on thin specimens - can only be used on non-living specimens

Answer 36

- can be used on thick specimens - can produce 3D images

Answer 37

- gives lower resolution than images from TEMs - can only be used on non-living specimens

Answer 38

- start by pipetting a small drop of water onto the centre of the slide - use tweezers to place a thin section of the specimen on top of the water drop - add a drop of stain, used to highlight objects in a cell - add the cover slip, do this by standing the slip upright on the side next to the water droplet and then carefully tilt and lower it so it covers the specimen - when trying to add the cover slip, try not to get any air bubbles underneath as they obstruct the view of the specimen

Answer 39

eosin - makes cytoplasm show iodine in potassium iodide solution - used to stain starch grains in plant cells

Answer 40

they are things that you can see down at the microscope, they are not a part of the cell/speciment looked at usually made during the preparation of the specimen and should not be there

Answer 41

- dust - air bubbles - fingerprints - inaccuracies caused by squashing and staining the sample

Answer 42

electron micrographs because specimens need a lot of preparation before you can view them under a microscope

Answer 43

by repeatedly preparing specimens in different ways if an object could be seen with one preparation technique, but not another, it was more likely to be an artefact than an organelle

Answer 44

- homogenisation = breaking up the cells - can be done in different ways, ex - vibrating the cells OR grinding up the cells in a blender - this breaks up the plasma membrane and releases the organelles into solution - the solution must be kept ice cold : reduces activity of enzymes which break down organelles - solution must be isotonic : should have the same concentration of chemicals as the cells being broken down BECAUSE it prevents damage to organelles through osmosis - solution must be buffered : to maintain pH

Answer 45

- involves getting rid of the big bits - homogenised cell solution is filtered through a gauze to separate any large cell debris, ex connective tissue, from the organelles - organelles are much smaller than the debris, so they pass through the gauze

Answer 46

- involves separating the organelles - cell fragments are poured into a tube - tube is put into a centrifuge, a machine that separates material by spinning - initially, it is spun at a low speed - the heaviest organelles, like nuclei, get flung to the bottom of the tube by the centrifuge : these form a thick sediment at the bottom called the PELLET - the SUPERNATANT contains the rest of the organelles suspended in the fluid - the supernatant is drained off and poured into another tube and spun in the centrifuge at a higher speed - heaviest organelles form a pellet at the bottom of the tube - the supernatant containing the rest of the organelles are drained off and poured into another tube and spun at an even higher speed - this process continues to repeat at a higher and higher until all organelles are separated - Mach time the pellet at the bottom is made of lighter and lighter organelles - order of organelles being separated : nuclei, mitochondria, lysosomes, ER, ribosomes order of organelles being separated in plants : nuclei, chloroplasts, mitochondria, lysosomes, ER, ribosomes

Answer 47

- for growth and replacement of damaged tissue

Answer 48

the cell cycle

Answer 49

2 genetically daughter cells are produced

Answer 50

gap phase 1/ G1 synthesis gap phase 2/ G2

Answer 51

- the cell grows - new organelles and proteins are made

Answer 52

- cell replicates its DNA - cell is ready to divide by mitosis

Answer 53

- cell keeps growing - proteins needed for cell division are made

Answer 54

- cell carries out normal functions, but also prepares to double its genetic content - cells DNA is unravelled and replicated = genetic content is doubled - organelles are replicated, so there are spare ones - ATP content s increased, as ATP provides the energy for cell division to take place

Answer 55

mitosis AND meiosis

Answer 56

- form of cell division that occurs during the cell cycle - parent cell divides to produce 2 genetically identical daughter cells - needed for the growth of multicellular organisms AND to repair damaged tissues - actually one continous process, but its described as being split up into prophase, metaphase, anaphase and telophase PMAT

Answer 57

- made of 2 strands joined together in the middle by a CENTROMERE - one strand = chromatid - 2 strands on the same chromosome = sister chromatid

Answer 58

- chromosomes condense = get shorter + fatter - centrioles = tiny bundles of protein, start moving to opposite ends of the cell AND they form a network of protein fibres across the cell called THE SPINDLE - nuclear envelope, membrane around the nucleus, breaks down AND chromosomes lie free in the cytoplasm

Answer 59

- chromosomes line up along the spindle equator, in the middle of the cell - the chromosomes become attached to the spindle by their centromere metaphase = middle = equator

Answer 60

- centromeres divide, separating the sister chromatids - spindles contract which pulls the chromatids to opposite poles (ends) of the spindle - chromatids appear v shaped summary - sister chromatids move to opposite poles of the spindle due to the centromeres dividing and spindle contracting anaphase = 'aaaaaa' = sound of sister chromatids separating

Answer 61

- chromatids reach the opposite poles on the spindle - chromatids uncoil and become long and thin again = called chromosomes again - nuclear envelope forms around each group of chromosomes = 2 nuclei - division of the cytoplasm, cytokinesis, finishes (started in anaphase) - now 2 daughter cells that are genetically identical to the original parent cell and to each other - mitosis is finished and each daughter cell starts interphase to get ready for another round of mitosis - Telophase = cyTokinesis

Answer 62

- mitosis and the cell cycle are controlled by genes and when enough division of cells takes place, they stop - if there is a mutation in the gene, the cells can grow out of control AND these cells will keep on dividing to make more and more cells, forming a TUMOUR - cancer = a tumour which invades surrounding tissue

Answer 63

- some treatments for cancer are designed to control the rate of cell division in tumour cells by disrupting the cell cycle = kills the tumour cells - these treatments are unable to differentiate between the tumour cells and the normal cells, so they kill the normal cells that are dividing - tumour cells divide more frequently than normal cells, so the treatments are more likely to kill tumour cells

Answer 64

- chemotherapy targets the G1 phase - chemo prevents the synthesis of enzymes needed for DNA replication - if these aren't produced, the cell is unable to enter the S phase - this disrupts the cell cycle, and the cell kills itself - radiation and some drugs are able to damage DNA - DNA in the cell is checked for damage at multiple points in the cell cycle - if severe damage is detected, the cell will kill itself = preventing further tumour growth

Answer 65

- cell membranes are the boundaries of cells - all cells are surrounded by membranes - in eukaryotic cells, many of the organelles are surrounded by membranes

Answer 66

- surround cells - barrier between the cell and its environment, controlling which substances enter and leave the cell - they are partially permeable, they let some molecules through but not others - substances can move across the cell surface membrane by diffusion, osmosis, active transport - sometimes the cell surface membrane is called the plasma membrane

Answer 67

- membranes around organelles divide the cell into different compartments = act as barrier between organelle and the cytoplasm - also partially permeable and control what substances enter and leave the organelle

Answer 68

- substances needed for respiration, like enzymes, are kept together inside a mitochondrion by the membrane surrounding the mitochondrion - RNA leaves the nucleus via the nuclear membrane/nuclear envelope - DNA is too large to pass through the partially permeable membrane, so it remains in the nucleus

Answer 69

- basic structure of all cell membranes is pretty much the same - they are composed of lipids, mainly phospholipids, proteins and carbohydrates

Answer 70

- 1972 = 'fluid mosaic model' suggested to describe the arrangement of molecules in the membrane - in the model phospholipid molecules form a continuous double layer - bilayer - the bilayer was fluid because the phospholipids are constantly moving - proteins are scattered through the bilayer, like tiles in a mosaic - include channel and carrier proteins, these allow large molecules and ions to pass through the membrane - receptor proteins on the cell surface membrane allow the cell to detect chemicals released from other cells - the chemicals signal to the cell to respond in some way, ex : insulin (hormone) binds to receptor proteins on liver cells, which tells the cells to absorb glucose - some proteins are able to move sideways through the bilayer, while others are in a fixed position - some proteins have a carbohydrate attached = glycoproteins - some lipids have a carbohydrate attached = glycolipids - cholesterol molecules are also present within the bilayer

Answer 71

- phospholipids molecules form a barrier to dissolved substances - they have a 'head' and a 'tail' - head = hydrophilic = attracts water - tail = hydrophobic = repels water - molecules automatically arrange themselves into a bilayer - heads face out towards water on both sides of the membrane - centre of the bilayer is hydrophobic so the membrane doesn't allow water soluble substances, ex - ions and polar molecules, to diffuse through - small, non polar substances, ex - carbon dioxide, and water can diffuse through the membrane

Answer 72

- gives membrane stability - type of lipid that is present in all cell membranes, except bacterial cell membranes - fits between the phospholipids - binds to the hydrophobic tails of the phospholipids, causing them to pack more closely together - restricts the movement of the phospholipids, making the membrane less fluid and more rigid - cholesterol helps to maintain the shape of animal cells (as they dont have cell walls) - important for cells that aren't supported by other cells, ex - red blood cells which float free in the blood - also has hydrophobic regions, so its able to create a further barrier to polar substances moving through the membrane

Answer 73

yes, they are affects how much the phospholipids in the bilayer can move = affects membrane structure and permeability

Answer 74

- phospholipids dont have much energy, so they cant move much - packed closely together and the membrane is rigid - channel and carrier proteins in the membrane denature = increases the permeability of the membrane - ice crystals may form and pierce the membrane, making it highly permeable when it thaws

Answer 75

- phospholipids can move around and aren't as tightly packed together - membrane = partially permeable - as temp increases, the phospholipids move more as they have more energy = increases permeability of the membrane

Answer 76

- phospholipid bilayer starts to melt = membrane becomes more permeable - water in cell expands, putting pressure on the membrane - channel and carrier proteins in the membrane denature = cant control what enters or leaves the cell = increasing permeability of the membrane

Answer 77

simple diffusion and facilitated diffusion

Answer 78

the net movement of particles (molecules or ions) from an area of HIGHER concentration to LOWER concentration

Answer 79

they do move both ways the net movement will be to the area lower concentration

Answer 80

until the particles are evenly distributed throughout the liquid or gas

Answer 81

the path from an area of higher concentration to an area of lower concentration

Answer 82

down the concentration gradient

Answer 83

it is a passive process, meaning no energy is required for it to take place

Answer 84

they can, as long as they can move freely through the membrane

Answer 85

when molecules can diffuse directly through a cell membrane

Answer 86

oxygen and carbon dioxide can diffuse easily through cell membranes they can do this because they are SMALL and NON POLAR small = so they can pass through spaces between the phospholipids non polar = makes them SOLUBLE in lipids, so they can DISSOLVE in the hydrophobic bilayer

Answer 87

- the concentration gradient - the thickness of the exchange surface - the surface area

Answer 88

higher the conc gradient = faster the rate of diffusion as diffusion takes place, the diff in conc between the 2 sides of the membrane decreases UNTIL it reaches an equilibrium = diffusion slows down over time

Answer 89

the thinner the exchange surface = the faster the rate of diffusion the thiner the exchange surface = the shorter the distance the particles have to travel

Answer 90

the larger the surface area = the faster the rate of diffusion ex of SA would be the SA of the cell surface membrane

Answer 91

ex of specialised cells - epithelial cells in the small intestine they have MICROVILLI, which are projections formed by the cell surface membrane folding up on itself = increases the cells SURFACE AREA larger SA = more particles can be exchanged in the same amount of time = increases rate of diffusion

Answer 92

as some larger molecules would diffuse very slowly through the phospholipid bilayer as they are very big in size charged particles would diffuse slowly because the centre of the bilayer is HYDROPHOBIC and they WATER SOLUBLE

Answer 93

- amino acids - glucose

Answer 94

- ions - polar molecules

Answer 95

the large or charged particles diffuse through CARRIER or CHANNEL proteins in the cell membrane = facilitated diffusion

Answer 96

moves particles down a concentration gradient = from a higher to lower concentration it is a passive process = doesn't require energy

Answer 97

a carrier protein

Answer 98

- moves large molecules across a membrane, down their concentration gradient - a large molecule attaches to a carrier protein in the membrane - the protein changes shape - the molecule is released on the opposite side of the membrane

Answer 99

channel proteins

Answer 100

the channel proteins form pores in the membrane for the charged particles to diffuse through/ down their concentration gradient different channel proteins facilitate the diffusion of different charged particles

Answer 101

- the concentration gradient - the number of channel or carrier proteins

Answer 102

the higher the conc gradient = the faster the rate of facilitated diffusion, until a certain point when equilibrium is reached, the rate of facilitated diffusion will level off

Answer 103

once all the proteins are in use, facilitated diffusion cant happen any faster EVEN if the concentration gradient is increased the higher the number of channel or carrier proteins in the cell membrane, the faster the rate of facilitated diffusion

Answer 104

aquaporins they are special channel proteins that allow the facilitated diffusion of water through cell membranes some kidney cells are adapted to have lots of aquaporins the aquaporins allow the cells to reabsorb a lot of the water that would have otherwise been excreted by the body, through urination

Answer 105

the diffusion of water molecules across a partially permeable membrane from an area of higher WP to an area of lower WP

Answer 106

the likelihood/potential of water molecules to diffuse out to into a solution

Answer 107

water molecules can because they are small and can diffuse easily through the cell membrane large solutes are unable to

Answer 108

it lowers the WP

Answer 109

it means the solution contains a high concentration of solutes more negative the WP = stronger the concentration of solutes in the solution

Answer 110

if 2 solutions have the same WP

Answer 111

they wont lose or gain any water , there is no net movement of water molecules BECAUSE there is no net movement of water molecules BECAUSE there is NO difference in WP between the CELL and the SURROUNDING SOLUTION

Answer 112

solutions with a higher WP compared with the inside of the cell

Answer 113

it will swell as water moves into the cell via osmosis

Answer 114

a solution that has a lower WP than the cell

Answer 115

the cell may shrink as water moves of the cell via osmosis

Answer 116

- WP gradient - thickness of the exchange surface - SA of the exchange surface

Answer 117

the higher the WP gradient, the faster the rate of osmosis as osmosis takes place, the difference in WP on either side of the membrane decreases, so the rate of osmosis levels off over time

Answer 118

the thinner the exchange surface, the faster the rate of osmosis

Answer 119

the larger the SA, the faster the rate of osmosis

Answer 120

- active process = uses energy to move molecules and ions across plasma membranes - usually against the conc gradient - carrier proteins and co-transporters are involved in active transport

Answer 121

- a molecule attaches to the carrier protein - protein changes shape, which moves the molecule across the membrane = releases it on the other side

Answer 122

- AT moves solutes from a low concentration to a high concentration, compared to FD which always moves from a high to a low concentration - AT requires energy while FD doesn't

Answer 123

- ATP is a common source of energy in the cell and its needed for AT - ATP undergoes a hydrolysis reaction, splitting into ADP and Pi = releases energy so solutes can be transported

Answer 124

- co-transporters are a type of carrier protein - they bind 2 molecules at the same time - the conc gradient of one of the molecules is used to move the other molecule against its own conc gradient, ex : the co-transport of glucose

Answer 125

- glucose is absorbed into the bloodstream in the small intestine - in the mammalian ileum, final part of a mammals small intestine, the conc of glucose is too low for glucose to diffuse out INTO the blood - glucose is absorbed from the lumen (middle of the ileum) by co-transport - step 1 - Na+ ions are actively transported out of the epithelial cells in the ileum INTO the blood, by the sodium potassium pump - creates a conc gradient, now a HIGHER conc of sodium ions in the LUMEN than in the CELL - step 2 - causes Na+ ions to diffuse from the LUMEN into the EPITHELIAL CELL, down the concentration gradient via the sodium-glucose co transporter proteins - the co transported carries glucose into the cell along with Na+ - results in the concentration of glucose in the cell increasing - step 3 - glucose diffuses out of the cell, into the BLOOD, down its concentration gradient through a protein channel by facilitated diffusion

Answer 126

- speed of individual carrier proteins - number of carrier proteins present - rate of respiration in the cell and availability of ATP

Answer 127

the faster they work, the faster the rate of AT

Answer 128

the more proteins there are, the faster the rate of active transport

Answer 129

if respiration is inhibited, AT can't take place respiration produces ATP, which is needed for AT as AT is an active process

Answer 130

- molecules, usually proteins, that can generate an immune response when detected the body - usually found on the surface of cells, including all your body cells - antigens that aren't normally found in the body are referred to as 'foreign antigens' - these antigens are the ones the immune system usually responds to - antigens allow the immune system : pathogens, abnormal body cells, toxins and cell from other individuals of the same species

Answer 131

- cell surface membrane contains proteins that act as antigens - these antigens allow the immune system to tell the difference between the bodys healthy cells (self cells) and 'foreign invaders'

Answer 132

- organisms that cause disease - all pathogens have antigens on their surface - these are identified as foreign by cells in the immune system and this leads to the immune response to destroy the pathogen

Answer 133

- bacteria - viruses - fungi

Answer 134

- cancerous or pathogen infected cells - have abnormal antigens on their surface, these trigger an immune response

Answer 135

- posions - molecules, NOT cells - some toxins are produced by bacteria - ex : clostridium botulinum (bacteria) releases a protein toxin which affects the nervous system, causing the system of botulism - the immune system is able to respond to toxins and the pathogens that release them

Answer 136

- when you receive cells from another person, those cells will have some different antigens to your own cells - this would be done through an organ transplant or blood transfusion - the foreign antigens trigger an immune response, this leads to the rejection of transplanted organs if the drugs aren't taken to suppress the recipients immune system (anti-rejection meds) - for blood transfusions, the most important antigens are the ABO blood group antigens - if the blood contains A or B antigens that aren't recognised by the recipients immune system, they WILL generate a immune response

Answer 137

if the donor is genetically identical to you

Answer 138

phagocytosis

Answer 139

- a type of white blood cell - it carries out phagocytosis, the engulfment of pathogens - found in the blood and in tissues - they are the first cells to respond to an immune system trigger in the body

Answer 140

a macrophage

Answer 141

- a phagocyte recognises the foreign antigen on a pathogen - cytoplasm of the phagocyte moves around the pathogen, engulfing it - the pathogen is now contained in a phagocytic vacuole (bubble) in the cytoplasm of the phagocyte - a lysosome, an organelle which contains lysozymes, fuses with the phagocytic vacuole - the lysozymes break down the pathogen - the phagocyte presents the pathogens antigens, it sticks the antigens on its surface to activate other immune system cells - the phagocyte is now acting an antigen presenting cell

Answer 142

- also called a t lymphocyte - another type of white blood cell - has receptor proteins on its surface that bind to complementary antigens presented to it by phagocytes : this activates the t cell - different types of t cells respond in different ways

Answer 143

- helper t cells/ Th cells - cytotoxic t cells/ Tc cells

Answer 144

- release chemical signals - these activate and stimulate phagocytes and cytotoxic t cells - activate b cells

Answer 145

- kill abnormal and foreign cells

Answer 146

- also called b lymphocytes - type of white blood cell - covered with antibodies, which bind to antigens to form AN ANTIGEN-ANTIBODY COMPLEX

Answer 147

- each B cell has a different shaped antibody on its membrane, so different ones bind to their complementary antigen - when the complementary antigen binds to the antibody on the B cell, the B cell is activated BUT this is also done with the substances released from helper T cells = clonal selection - the activated B cell divides into plasma cells

Answer 148

- plasma cells are clones of B cells = exact same - plasma cells secrete lots of antibodies which are specific to the antigen = MONOCLONAL ANTIBODIES - MA bind to the antigens on the surface of the pathogen, forming many antigen-antibody complexes

Answer 149

- an antibody has 2 binding sites = can bind to 2 pathogens at the same time - causes pathogens to become clumped together = AGGLUTINATION - phagocytes bind to the antibodies and phagocytose many pathogens at once, allows the destruction of pathogens which carry this antigen in the body

Answer 150

- they are proteins as they are made of chains of amino acids - the specificity of antibodies is dependent on its VARIABLE regions = they form the antigen BINDING SITES - each antibody has a var region with a unique tertiary structure that is complementary to ONE specific antigen - all antibodies have the SAME CONSTANT REGIONS - variable region = varies from one antibody to another - constant region = constant amongst all antibodies

Answer 151

- cellular - humoral - both types of response are needed to remove a pathogen from the body and the responses interact with each other - ex, T cells help to activate B cells

Answer 152

- T cells and other immune system cells that they interact with, ex : phagocytes

Answer 153

- B cells - clonal selection - production of monoclonal antibodies

Answer 154

- when an antigen enters the body for the first time - slow as there aren't many B cells that can make the antibody needed to bind to the antigen - eventually the body will produce enough of the right antibody to overcome the infection, meanwhile the infected person will display symptoms of the disease - after exposure to the antigen, both T and B cells produce MEMORY CELLS, which remain in the body for a long time - memory cells remember the specific antigen and will recognise it if there is another infection from the same pathogen with the same antigens - memory T cells : remember the specific antigen and will recognise it a second time around - memory B cells : record the specific antibodies needed to bind to the antigen - after the primary response, the person is immune and their immune system has the ability to respond quickly to a second infection

Answer 155

remember the specific antigen and will recognise it a second time around

Answer 156

record the specific antibodies needed to bind to the antigen

Answer 157

- happens if the pathogen enters the body again - immune system will produce a quicker, stronger immune response - clonal selection happens faster - memory B cells are activated and divide into plasma cells which divide into the right type of antibody for the antigen - memory T cells are activated and divide into the correct type of T cells to kill the cell which carries the antigen - secondary response usually gets rid of the pathogen before any symptoms begin to show

Answer 158

vaccinations

Answer 159

active immunity and passive immunity

Answer 160

type of immunity that you get when your immune system makes its own antibodies after being stimulated by an antigen

Answer 161

natural artificial

Answer 162

when you become immune after catching a disease

Answer 163

this is when you become immune after you have been given a vaccination exposing you to a harmless dose of antigen

Answer 164

this is the type of immunity you get from being given antibodies made by a different organism - your immune system doesn't produce any antibodies of its own

Answer 165

- this is when a baby becomes immune due to the antibodies it receives from its mother - through PLACENTA and BREAST MILK

Answer 166

- this is the you become immune after being injected with antibodies from someone else - ex, when you become immune after being injected with antibodies against the tetanus toxin, collected from blood donations

Answer 167

- active immunity requires exposure to the antigen, while passive doesn't require exposure to the antigen - active immunity takes a while for protection to develop, while passive immunity has immediate protection - in active immunity, memory cells are produced but in passive immunity memory cells aren't produced - in active immunity, protecting is long term because the antibody is produced in response to a complementary antigen being present in the body, passive immunity is short term because the antibodies given are broken down

Answer 168

- contain antigens which may be free or attached to a dead or weakened pathogen - while your B cells divide to increase their amount for their response against a pathogen, you suffer from the disease and VACCINATIONS can help avoid this - antigens in vaccines cause your body to produce memory cells against a particular pathogen, without the pathogen causing disease = immunity with no symptoms - vaccines protect individuals that have them and those who aren't vaccinated BECAUSE they reduce the occurrence of the disease BECAUSE there are less people to catch it from = HERD IMMUNITY

Answer 169

orally injected

Answer 170

- could be broken down by enzymes in the gut - molecules in the vaccination may be too large to be absorbed into the blood

Answer 171

booster vaccines given to ensure more memory cells are produced

Answer 172

- all vaccines are tested on animals before being tested on humans - some people disagree with animal testing AND animal based substances may be used to produce a vaccine which people disagree with - testing vaccines on humans can be risky as volunteers may put themselves at unnecessary risk of contracting the disease as they believe they are fully protected, ex - may have unprotected sex because they have had a new HIV vaccine and believe they are protected and the vaccine may not work - some people dont want to take the vaccine due to the risk of side effects, but they are still protected because of herd immunity - other people think this is unfair - if there was an epidemic of a new disease there would be a rush to receive a vaccine and difficult decisions would have to be made about who would be the first to receive the vaccine

Answer 173

- they are on the surface of pathogens and activate the primary response - when you are infected for a second time with the SAME pathogen, which has the same antigens on its surface, they activate the secondary response and you don't get ill

Answer 174

- when pathogens change their surface antigens - due to changes in the genes of a pathogen

Answer 175

- when you are infected for a second time, the memory cells produced from the first infection will not recognise the different antigens - immune system has to carry out a primary response against these new antigens - primary response takes time to get rid of the infection and you get ill again and feel the symptoms

Answer 176

- makes it difficult to develop vaccines against some pathogens due to antigenic variation - examples of pathogens that show antigenic variation is HIV and influenza virus

Answer 177

- antibodies that are produced from one/a single group of genetically identical B cells/plasma cells - they are all identical in structure

Answer 178

because their binding sites have a unique tertiary structure, which only an antigen with a complementary shape can fit into

Answer 179

- the fact that you can make monoclonal antibodies bind to anything you want - useful for treating illness and in medical diagnosis

Answer 180

- different cells in the body have different surface antigens - cancer cells have antigens called tumour markers, these are not found on normal body cells - MA can be made so they can bind to the tumour markers - anti cancer drugs can be attached to the MA and then when the MA come into contact with the cancer cells they will bind to the tumour markers - the drug will only accumulate in the body where there are cancer cells - side effects of an antibody based drug are lower than other drugs BECAUSE they accumulate near specific cells

Answer 181

- pregnancy tests detect the hormone hCG which is found in the urine of pregnant women - application area contains antibodies that are complementary to the hCG protein, these are bound to a coloured bead - when urine is applied to the application area, any hCG will bind to the antibody on the beads = forms an antigen-antibody complex - the urine moves up the stick to the test strip, this carries any beads with it - the test strip contains antibodies to hCG which are immobilised (stuck in place) - if there is any hCG present the test strip will turn the colour of the coloured bead, because the immobilised antibody binds to any hCG - if no hCG is present, the beads will pass through the test area without binding to anything, therefore there will be no colour change

Answer 182

- ex, malaria - the test strip will detect malaria antigens in the blood

Answer 183

- ELISA = enzyme linked immunosorbent assay - allows you to see if a patient has any antibodies to a specific antigen or any antigen to a certain antibody - can be used in medical diagnosis to test for pathogenic infections, allergies etc - in a ELISA test, an antibody is used and it has an enzyme attached to it - the enzyme attached can react with a substrate to produce a coloured product - causes solution to change colour - a colour change presents the antigen or antibody being tested for IS PRESENT in the sample being tested - ex of a sample being tested = blood plasma - in some types of ELISA, the quantity of this antigen/antibody can be worked out from the intensity of colour change

Answer 184

direct and indirect

Answer 185

direct ELISA

Answer 186

- uses a single antibody which is complementary to the antigen being tested for - antigens from a patient sample are bound to the inside of a well in a well plate - a detection antibody, with an attached enzyme, that is complementary to the antigen of interest is added - if the antigen of interest is present in the patient sample, it will be immobilised on the inside surface of the well AND the detection antibody will bind to it - the well is washed to remove any unbound antibody and a substrate solution is added - if the detection antibody is present, the enzyme reacts with the substrate to give a colour change = positive result for the presence of the antigen, means the person being tested for is positive for what they are being tested for as they have the antigens

Answer 187

- uses 2 different antibodies - can be used to see if a patient possesses antibodies to HIV - the HIV antigen is bound to the bottom of a well in a well plate - a sample of the patients blood plasma, this may contain different antibodies, is added to the well - any HIV specific antibodies in the plasma will bind the to the HIV antigen which is stuck to the bottom of the well - the well is washed to remove any unbound antibodies - a secondary antibody, that has a specific enzymes attached to it, is added to the well = this antibody can bind to the HIV specific antibody/primary antibody - well is washed out again to remove any unbound secondary antibodies - if there is no primary antibody in the sample, all of the secondary antibodies will be washed away as there will be nothing for them to bind to - a solution is added to the well and this solution contains a substrate, this is able to react with the enzyme attached to the secondary antibody and produce a coloured product - if the solution changes colour, it indicates that the patient has HIV specific antibodies in their blood = the patient is infected with HIV

Answer 188

- MA therapy has issues around animal rights as animals are used to produce the cells from which MA are made from/ produced - some people disagree with the use of animals in this way

Answer 189

- they arent living things - they are only able to reproduce inside the cells of another organism

Answer 190

- human immunodeficiency virus - virus that affects the human immune system

Answer 191

- acquired immune deficiency syndrome - condition where the immune system deteriorates and eventually fails - makes the sufferer more vulnerable to other infections, ex pneumonia

Answer 192

- HIV infects and eventually kills helper T cells - the helper T cells act as host cells for the virus - helper T cells have a significant role in the immune response as they activate phagocytes, cytotoxic t cells and B cells - without enough T helper cells the immune system wont be able to provide an effective response to infections because other immune system cells dont behave how they should - people with HIV develop AIDS when their helper T cell count is critically low

Answer 193

- HIV replicates rapidly - the infected person may experience severe flu like symptoms - after this period, HIV replication drops to a lower level = latency period - during the latency period the infected person wont experience any symptoms = can last for years

Answer 194

- people with HIV are classed as having AIDS when symptoms of their failing immune system appear OR their T helper cell count drops below a certain level - the length of time between infection of HIV to the development of AIDS varies between individuals, without treatment it is usually 10 years - people with AIDS usually develop diseases that would not cause serious problems for those who have healthy immune systems

Answer 195

- minor infections of the mucous membranes, ex inside the nose, ears and genitals - recurring respiratory infections - as AIDS progresses, the number of immune system cells decreases further and patients become susceptible to more serious infections, ex chronic diarrhoea, severe bacterial infections and tuberculosis - during the late stages of AIDS, patients have a very low number of immune system cells and can develop a range of serious infections like toxoplasmosis of the brain (parasite infections), candidiasis of the respiratory system (fungal infection) - these types of serious infections kill AIDS patients, not HIV itself

Answer 196

- factors that affect the progression of HIV -> AIDS and survival time with AIDS = existing infections, the strain of HIV they are infected with, their age AND their access to healthcare

Answer 197

- spherical structure - made of a core of viral RNA - enzyme reverse transcriptase - capsid - envelope, made from membrane stolen from previous host cell - attachment proteins, help HIV attach to host T helper cell

Answer 198

- HIV and all other viruses can only reproduce inside the cells of the organism it has infected - HIV replicates inside the T helper cells of the host BECAUSE it doesn't have the equipment (enzymes and ribosomes) to replicate on its own, so it uses the host cells

Answer 199

- the attachment proteins attaches to a receptor molecule on the cell membrane of the host T helper cell - the capsid is released into the cell, this is where it uncoats and releases the RNA into the cells cytoplasm - in the cell, reverse transcriptase is used to make a complementary strand of DNA from the viral RNA template - the double stranded DNA is made and inserted into the human DNA - host cell enzymes are used to make viral proteins from the viral DNA found in the human DNA - the viral proteins are assembled into new viruses, these bud from the cell and go on to infect other cells

Answer 200

- antibiotics kill bacteria by interfering with their metabolic reactions - they target bacterial enzymes and ribosomes used in these reactions - the bacterial enzymes and ribosomes are different from human enzymes and ribosomes - antibiotics are designed only to target bacterial enzymes and ribosomes SO they dont damage human cells - viruses dont have their own enzymes and ribosomes and therefore they use the host cells - antibiotics are unable to inhibit the enzymes and ribosomes that the virus uses, because they use human viruses use human enzymes and ribosomes, therefore dont target human processes

Answer 201

- designed to target the few virus specific enzymes that exist - virus specific enzymes = enzymes that only the virus uses

Answer 202

- HIV uses reverse transcriptase to replicate - human cells dont use the enzyme reverse transcriptase = drugs can be used to inhibit it without affecting the host cell - these drugs are called reverse transcriptase inhibitors

Answer 203

- currently no cure or vaccine for HIV but antiviral drugs can be used to slow down the progression of HIV infection and AIDS in an infected person - the best way to control HIV infection in a population is controlling its spread

CHAPTER 2 - CELLS Flashcards

- eukaryotic cells - prokaryotic cells - cell contents - cell division - cell membranes - movement within cells