Cells Flashcards

Question

compare the ribosomes in a prokaryote vs in a eukaryote

Answer 1

- prokaryotes contain 70s ribosomes whereas eukaryotes contain 80s ribosomes - 70s ribosomes are smaller and a found in prokaryotic cells, mitochondria and in chloroplasts - 80s ribosomes are larger ribosomes found in eukaryotic cells and they usually measure around 25nm in length

Answer 2

- prokaryotic cells don't contain a nucleus instead contain a single circular DNA molecule free in cytoplasm which is not protein bound - nucleus in eukaryotic cell made of a nuclear envelope (a double membrane), nuclear pores. nucleoplasm ( a granular, jelly-like material, chromosomes (which are protein-bound, linear DNA), + a nucleolus (a smaller sphere which is the site of rRNA production and makes ribosomes.

Answer 3

- prokaryotic cell wall made of murein (a glycoprotein) - eukaryotic cell wall is made up of microfibrils of the cellulose polymer (plants) or chitin (a nitrogen-containing polysaccharide, fungi) - all prokaryotic cells contain a cell wall whereas only plants or fungi eukaryotic cells do

Answer 4

small loops of DNA which only carry a few genes

Answer 5

- thick slimy layer made of protein - prevents bacteria from desiccating (drying out) - protects the bacteria against host's immune system by covering antigens on outside of cell

Answer 6

tail-like structure that rotates to enable the bacteria to move

Answer 7

- used to isolate different organelles so they can be studied - enables individual organelle structures and functions to be studied

Answer 8

1) homogenisation: cell must be homogenised (broken open) using a blender. The cells are blended in a cold, isotonic + buffered solution. The solution is then filtered to remove large cell debris 2) ultracentrifugation: filtered solution is spun at different speeds in a centrifuge. organelles separate according to their density. this is done by differential centrifugation

Answer 9

- centrifuge spins and the centrifugal forces cause the pellets of the most dense organelles to form at the bottom - the centrifuge is first spun at a low speed and the process is repeated at increasingly faster speeds - each time the supernatant (liquid) is removed leaving behind a pellet of organelles - the supernatant is then put back and spun at a faster speed to remove the next pellet of organelles

Answer 10

reduces enzyme activity when the cell breaks open, enzymes are released which could damage the organelles

Answer 11

to prevent osmosis as water moving in/out could cause the organelles to burst/shrivel

Answer 12

prevent damage to organelles

Answer 13

- nuclei - chloroplasts (if plant) - mitochondria - lysosomes - endoplasmic reticulum - ribosomes

Answer 14

- light microscope - transmission electron microscope - scanning electron microscope

Answer 15

how many times larger an image is compared to an object

Answer 16

the minimum distance between 2 objects in which they can still be viewed as separate

Answer 17

the wavelength of light determines light microscope resolution, whilst the wavelength of the beam of electrons determines electron microscope resolution

Answer 18

a beam of light is condensed to create the image

Answer 19

- poorer resolution due to light having a longer wavelength - lower magnification

Answer 20

they have a poor resolution due to the long wavelength of light

Answer 21

- colour images - living samples can be examined - can be used by almost anyone

Answer 22

a beam of electrons is condensed using electromagnets to create the image

Answer 23

- higher resolution - higher magnification

Answer 24

- images produced are black and white - non-living samples only - must be in a vacuum

Answer 25

- extremely thin specimens stained + placed in vacuum - electron gun produces beam of electrons that pass through specimen - some parts absorb the electrons more + appear darker - 2D detailed image produced, shows internal structure of cells

Answer 26

- electrons are beamed onto the surface and the electrons are scattered in different ways, depending on the contours - a 3D image is produced

Answer 27

-better resolution than the SEM which only has a resolution of 2nm and the TEM has a resolution of 0.2nm - can see internal structures rather than just the surface

Answer 28

- specimens do not need to be thin as the electrons are not transmitting through - 3D image produced - cost less - require less preparation

Answer 29

electrons are absorbed or deflected by molecules in the air, and this prevents them from reaching the specimen

Answer 30

makes organelles more visible + improves contrast so can distinguish between different types of cells and different organelles

Answer 31

multiply (usually by 1000, unless converting m to cm which is x100 or cm to mm which x10)

Answer 32

divide (usually by 1000, unless converting cm to m which is divide by 100 or mm to cm which is divide by 10)

Answer 33

a scale on a glass disc inside of a light microscope can be used to measure the size of the object you are viewing under the microscope

Answer 34

glass slide with a scale on it which you place on the stage used to calibrate the eyepiece graticule

Answer 35

1) line up the stage micrometer and eyepiece graticule whilst looking through the eyepiece 2) count how many divisions on the eyepiece graticule fit into one division on the micrometer 3) each division on the stage micrometer is 10um, so this can be used to calculate what 1 division on the eyepiece graticule is at that magnification: 10um / (how many divisions fit into 1 division of stage micrometer) 4) count how many divisions long the object is and multiply by answer from step 3

Answer 36

mitosis or meiosis

Answer 37

binary fission

Answer 38

they are non-living

Answer 39

inside the host cells they invade by injecting their nucleic acid into the cell to replicate the virus particles

Answer 40

- interphase (G1, S, G2) - nuclear division (mitosis/meiosis) - cytokinesis

Answer 41

organelles double, cell grows and DNA replicates

Answer 42

- can either be mitosis (2 identical diploid cells created) or meiosis (4 genetically different haploid cells created) - mitosis creates cells with identical DNA for growth + repair, whereas meiosis creates gametes

Answer 43

division of the cytoplasm to create new cells

Answer 44

- mRNAs and proteins synthesised - cell grows larger + some organelles are copied - cellular checks made to ensure DNA is in a good enough condition to be replicated - if DNA damaged then cell division is terminated at this stage

Answer 45

- DNA is replicated - generates sister chromatids, (identical pairs of chromosomes) - sister chromatids are attached to each other by a centromere

Answer 46

- cell undergoes additional growth - organelles are copied - components of microtubules (which will move chromosomes during mitosis) are synthesised - G2 ends when mitosis begins

Answer 47

a specialised sequence of DNA that links the sister chromatids

Answer 48

- prophase - metaphase - anaphase - telophase

Answer 49

- chromosomes condense + become visible - in animals, the centrioles separate + move to opposite poles of cell - nucleolus disappears

Answer 50

- chromosomes align along the equator of the cell - the spindle fibres released from the poles now attach to the centromere + chromatids

Answer 51

- spindle fibres retract + pull the centromere + chromatids they are bound to to opposite poles - causes centromere to divide in 2 - requires energy in form of ATP

Answer 52

- chromosomes become longer and thinner again - spindle fibres disintegrate and nucleus starts to reform - final stage in the cell cycle (cytokinesis) takes place : cytoplasm splits in two to create 2 new genetically identical cells

Answer 53

the proportion of cells which are undergoing mitosis

Answer 54

(number of cells in mitosis/total number of cells) x100

Answer 55

chromosomes are visible

Answer 56

the mixture and movement of the phospholipids, proteins, glycoproteins and glycolipids the membrane is made of

Answer 57

- fluid: has a phospholipid bilayer in which individual phospholipids can move = membrane has flexible shape - mosaic: proteins, glycoproteins and glycolipids are embedded on both the inside and outside of the membrane

Answer 58

- phospholipid bilayer - cholesterol - proteins - partially permeable membrane

Answer 59

- phospholipids align as a bilayer due to the hydrophilic heads being attracted to the water and the hydrophobic tails being repelled by the water

Answer 60

- is present in some membranes - will restrict the lateral (sideways) movement of other molecules in the membrane - useful as it makes the membrane less fluid (more rigid) at high temperatures and prevents water + dissolved ions leaking out of the cells which in turn prevents dehydration/bursting of cell

Answer 61

- peripheral protein (do not extend completely across the membrane) - integral ( span across from one side of the bilayer to the other)

Answer 62

- provide mechanical support - connect to proteins/lipid to make glycoproteins which in turn are used as receptors (for example) for cell recognition

Answer 63

protein carriers or channel proteins involved in the transport of molecules across the membrane

Answer 64

they form tubes that fill with water to enable water-soluble ions to diffuse

Answer 65

they bind with larger molecules, e.g. glucose or amino acids, and change shape to release the molecule to the other side of the membrane (transport them to the other side of the membrane)

Answer 66

- lipid-soluble substances (e.g. some hormones) - very small molecules (e.g. CO2, O2, H2O)

Answer 67

- water-soluble (polar) substances (e.g. sodium ions) - large molecules (e.g. glucose)

Answer 68

net movement of molecules from an area of higher concentration to an area of lower concentration (until equilibrium is reached)

Answer 69

passive (does not require ATP)

Answer 70

lipid-soluble and small

Answer 71

- in facilitated diffusion, proteins are used to transport molecules - ions and polar molecules which cannot simply diffuse can be transported across membranes by facilitated diffusion using protein channels and carrier proteins - this is still selective as the channel proteins only open in the presence of specific ions when they bind to the protein

Answer 72

net movement of water from an area of high water potential to an area of lower water potential across a partially permeable membrane

Answer 73

- the pressure created by water molecules - measured in kPa - symbol is Ψ

Answer 74

the water potential will become more negative

Answer 75

water potential is the same in the solution and the cell within the solution

Answer 76

water potential of a solution is more positive that in the cell, causing water to move into the cell (cell may swell/burst)

Answer 77

water potential of a solution is more negative that the cell, causing water to move out of the cell (cell may shrink/shrivel)

Answer 78

- a lot of water will move into the animal cell by osmosis - due to the lack of a cell wall the pressure will cause the cell to burst - plant cells do not burst because of the strengthened cell wall + instead become turgid

Answer 79

both animal and plant cells will shrivel if placed in a hypertonic solution due to large volumes of water leaving the cell by osmosis

Answer 80

movement of molecules + ions from an area of lower concentration to an area of higher concentration (Against a concentration gradient) using ATP + carrier proteins

Answer 81

only certain molecules which are complementary in shape to the protein can bind to the carrier proteins to be pumped

Answer 82

- ATP will bind to the protein on the inside of the membrane + is then hydrolysed into ADP + Pi, causing a small amount of energy to be released - energy is used to change the shape of the protein which causes it to open towards the inside of the membrane and therefore the molecule is released to the other side of the membrane - the Pi (inorganic phosphate) molecule is then released from the protein so the protein reverts back to its original shape - process can now continue to happen as long as there is a supply of ATP available

Answer 83

to absorb glucose from the lumen to the gut there must be a higher concentration of glucose in the lumen compared to the epithelial cell (for facilitated diffusion) however there is usually more glucose in the epithelial cell so active transport and cotransport are required

Answer 84

1) sodium ions are actively transported out of the epithelial cell into the blood (reduces the sodium ion concentration in the epithelial cell) 2) sodium ions can then diffuse from the ileum down their concentration gradient into the epithelial cell 3) the proteins the sodium ions diffuse through is a cotransporter protein (2 different molecules attach before either of them are transported to the other side), so either glucose or amino acids also attach and are transported into the epithelial cell against their concentration gradient 4) glucose then moves by facilitated diffusion from epithelial cell to blood

Answer 85

the concentration of glucose in the blood is lower than in the epithelial cells because the blood flows and is carried away

Answer 86

increase surface area for cotransporter proteins so sodium ions can diffuse through

Answer 87

non-specific - any non-self cell (e.g. a pathogen) that is detected will trigger the same response to destroy it

Answer 88

a macrophage (type of white blood cell) that carries out phagocytosis

Answer 89

1) chemicals/debris released by pathogens/abnormal cells attract phagocytes + they will move towards the cells 2) phagocytes attach to chemicals/antigens via receptors 3) phagocytes change shape to move around + engulf pathogen 4) once engulfed pathogen is contained within a phagosome vesicle 5) a lysosome within the phagocytes will fuse with the phagosome and release its contents 6) the lysozyme enzyme is released into the phagosome 7) pathogen is destroyed 8) the soluble products are absorbed + used by the phagocyte

Answer 90

rate = (surface area x difference in concentration)/length of diffusion path

Answer 91

larger surface area = faster rate of diffusion

Answer 92

larger difference in concentration = faster rate of diffusion

Answer 93

longer diffusion path = slower rate of diffusion

Answer 94

- the movement of a substance into cell by a vesicle - vesicle = form of packaging used by cells

Answer 95

the movement of a substance out of the cell by a vesicle

Answer 96

white blood cells involved in the specific immune response

Answer 97

bone marrow

Answer 98

T lymphocyte

Answer 99

T cells respond to specific antigens on the surface of cells

Answer 100

any cell that present a non-self antigen on their surface

Answer 101

- infected body cells will present the viral antigens on their surface - a macrophage which has engulfed + destroyed a pathogen will present the antigens on their surface - cells of a transported organ will have differently shaped antigens on their surface compared to self-cell antigens - cancer cells will have abnormal shaped self-cell antigens

Answer 102

T cells only respond to antigens which are present on cells (APC) and not antigens detached from cells within body fluids e.g. the blood

Answer 103

1) once a pathogen has been engulfed + destroyed by a phagocyte, the antigens are positioned on the cell surface - it is now an antigen-presenting cell (APC) 2) helper T cells have receptors on their surfaces which can attach to the antigens on APCs 3) once attached, this stimulates the helper T cells to divide by mitosis, producing large numbers of clones 4) cloned helper T-cells differentiate into different cells

Answer 104

- some remain as helper T cells + activate B lymphocytes - some stimulate macrophages to perform more phagocytosis - some become memory cells for that specific antigen - some become cytotoxic T cells (killer T cells)

Answer 105

destroy abnormal or infected cells

Answer 106

- they release perforin (a protein) which embeds in the cell surface membrane and makes a pore so that any substances can enter/leave the cell which causes cell death

Answer 107

when there is a viral infection, as viruses infect body cells

Answer 108

bone marrow

Answer 109

B cells antibodies

Answer 110

1) antigens in blood collide with complementary antibody on B cell 2) B cell takes in antigen by endocytosis + then presents it on cell surface membrane 3) when B cell collides with helper T cell receptor, activates B cell to go through clonal selection 4) B cells undergo mitosis to make large numbers of cells - differentiate into memory/plasma cells 5) plasma cells make antibodies 6) B memory cells can divide rapidly into plasma cells when reinfected with same pathogen to make large numbers of antibodies rapidly

Answer 111

- involved in the primary immune response - secrete antibodies directly into body fluids - only survive for a few days but produce 2000 antibodies per second - response is slow and person will get ill before pathogen destroyed

Answer 112

- involved in the secondary immune response - circulate in the blood and tissue fluid - remain in body fluids for decades - when they encounter the antigen from the primary response they divide rapidly - response is rapid and person will not get ill.

Answer 113

- during primary response to a pathogen (natural) or to a vaccination (artificial), antibody concentration in blood takes 1-2 weeks to increase. - If body invaded by same pathogen again or by pathogen that person was vaccinated against then, during the secondary response, the antibody concentration in blood takes much shorter period of time to increase + is higher than after vaccination or first infection

Answer 114

quaternary structure 4 polypeptide chains

Answer 115

- antibodies are flexible + can bind to multiple antigens which causes the clumping together of cells or particles which assists phagocytosis as it makes it easier for phagocytes to locate + destroy the pathogens

Answer 116

- antibodies introduced to body (e.g. by injection) - pathogen doesn't enter body so plasma cells and memory cells are not made - no long term immunity

Answer 117

- antibodies passed to s fetus through a placenta - antibodies passed through breast milk to a baby

Answer 118

immunity created by your own immune system following exposure to the pathogen or its antigen

Answer 119

the creation of own antibodies and memory cells following an infection

Answer 120

the creation of antibodies and memory cells following the introduction of a weakened version of the pathogens via a vaccination

Answer 121

1) small amounts of weakened or dead pathogens/antigens introduced into body 2) activates B cells to go through clonal selection 3) B cells undergo mitosis to make large numbers of cells - these differentiate into plasma cells or memory B cells 4) plasma cells make antibodies 5) B memory cells divide rapidly into plasma cells when reinfected with same pathogen to make large numbers of antibodies rapidly - this means person will not feel symptoms when naturally exposed to the pathogen

Answer 122

- if enough of the population is vaccinated the pathogen cannot easily spread amongst the population - this provides protection for those who are not vaccinated, e.g. those who are too young, already ill, or those with a compromised immune system

Answer 123

a pathogen's DNA can mutate frequently

Answer 124

- if a mutation occurs in the gene which codes for the antigen then the shape of the antigen will change

Answer 125

- any previous immunity to a pathogen (either naturally through prior infection or artificially through vaccination) will no longer be effective, as all the memory cells in the blood will have a memory of the old antigen shape

Answer 126

have unique 3D tertiary structures

Answer 127

a response will be triggered to destroy the cell

Answer 128

- lymphocytes made when fetus and in the womb it is unlikely to be exposed to anything other than self cells - the lymphocytes complementary to the antigens on self cells will die/production will be suppressed which prevents lymphocytes from attacking own cells - the only remaining lymphocytes are complementary t pathogenic and nonself cells - the same process occurs after birth in the bone marrow - any new lymphocytes made in the bone marrow which are complementary in shape to antigens on self cells will be destroyed

Answer 129

sometimes lymphocytes that attack self-cells are produced instead of destroyed and so they attack the person's own immune system leaving them more susceptible to infections and cancer

Answer 130

- molecules that generate an immune response by lymphocyte cells when detected in the body - they are usually proteins and are located on the surface of cells

Answer 131

viruses are non-living, meaning they have to replicate inside of cells - this makes it difficult destroy them without harming host cells

Answer 132

viruses have different mechanisms to replicate than bacteria, as well as no cell wall. antibiotics often work by interfering with the mechanisms of replication in a bacterial cell, e.g protein synthesis

Answer 133

- core = genetic material (RNA) and the enzyme reverse transcriptase, which are needed for viral replication - capsid = outer protein coat - envelope - extra outer layer made out of membrane taken from the host's cell membrane - protein attachments - on the exterior of the envelope to enable the virus to attach to the host's helper T cells

Answer 134

1) HIV is transported around in the blood until it attaches to a CD4 protein on the helper T cells 2) the HIV protein capsule then fuses with the helper T cell membrane, enabling the RNA and the enzymes (reverse transcriptase) from HIV to enter 3) the HIV enzyme reverse transcriptase copies the viral RNA into a DNA copy and moves to the helper Tcell nucleus 4) here, mRNA is transcribed, and the helper T-cell starts to create viral proteins to make new virus particles

Answer 135

when they are infected with HIV

Answer 136

- when the replicating viruses in the helper T cells interfere with their normal functioning of the immune system - with the helper T cells being destroyed by the virus, the host is unable to produce an adequate immune response to other pathogens and is left vulnerable to infections and cancer - eventually the destruction of the immune system will lead to the patient's death (not the HIV/AIDS itself)

Answer 137

a single type of antibody that can be isolated and cloned

Answer 138

a protein which has a binding site complementary in shape to certain antigens

Answer 139

- medical diagnosis - targeted medication - pregnancy testing - transplant surgery

Answer 140

- some cancer can be treated using MABs, which are designed with a binding site complementary to the antigens on outside of cancer cells - antibodies given to cancer patient + attach to cancer cells - as antibodies are bound to cancer antigens, this prevents chemicals from binding to cancer cells which enable uncontrolled cell division - therefore MABS prevent the cancer cells from growing and as they as designed to only attach to cancer cells, they do not cause harm to normal cells

Answer 141

- MABS complementary in shape to cancer cells antigens with cytotoxic drugs attached are delivered directly to cancer cells - reduces the harmful side effects that traditional chemotherapy and radiotherapy cause

Answer 142

ELISA test - MABs used to detect amount of certain substances in blood by binding to them - used to detect range of diseases inc influenza, chlamydia + prostate cancer

Answer 143

- MABS + colour particles are attached to the test strip of home pregnancy testing kits - pregnant women produce high levels of hCG in urine - hCG attaches to the antibodies and as the hCG-antibody-colour complex moves along the testing strip they become trapped to form a coloured line

Answer 144

1) virus proteins (antigens) are added to wells of a 96-well plate 2) the antigens bind to the plastic, coating the bottom of the wells 3) the primary antibody is added to the well- these are from the patient’s serum sample 4) excess antibody is washed away, leaving only antibodies bound to the antigens behind. this wash removes excess antibodies that are unbound and prevents non-specific binding. 5) a secondary antibody which is complementary to the first is added to the wells. the secondary antibody also has an enzyme attached 6) excess secondary antibody is washed away, removing any inbound antibodies and leaving only secondary antibodies bound to the first antibodies 7) substrate is added to the wells 8) secondary antibody containing an enzyme will cause a colour change when exposed to the substrate. a colour change indicates a positive reaction 9) presence of colour indicates presence of antibodies in test sample, meaning the patient will have been exposed to the antigen - the intensity of the colour indicates the quantity of antibodies present

Answer 145

- requires mice to produce MABs (spleen gets removed and mice die) - guidelines in place to minimise suffering of mice - successful in treating cancers - caused deaths in MS sufferers - informed consent required before treatment - drug trials may harm healthy human volunteers

Answer 146

- responsible for creating spindle fibres - spindle fibres released from both poles to create spindle apparatus - spindle apparatus will attach the centromere and chromatids on the chromosome during mitosis