Unit 2 - Cells Flashcards

Question

what is the structure of mitochondria?

Answer 1

oval-shaped double membrane (outer & inner mitochondrial membrane) outer membrane regulates entry & exit of substances intermembrane space inner membrane is folded into cristae & matrix that contains enzymes for link reaction & Kreb's cycle (large sa to hold the electron transfer chain & the enzyme ATPsynthase) large sa maintained by sausage-shape & short diffusion distance so quick diffusion in & out 70s ribosomes DNA loops

Answer 2

site of photosynthesis light dependent reaction on thylakoid membrane light independent reaction in stroma

Answer 3

small, flattened smooth double membrane (chloroplast envelope) stroma (fluid-filled) where the synthesis of sugars happens - light independent reaction (calvin cycle) thylakoid: where light dependent reaction happens - (fluid-filled membrane sacs) in stacks called grana that contain chlorophyll (photosynthetic pigment) + intergranal/stromal lamellae that link grana contains 70s ribosomes & loops of chloroplast DNA contains ATPsynthase (makes ATP)

Answer 4

to provide mechanical strength to prevent cell lysis (bursting) due to osmotic entry of water to allow plants to develop turgor pressure/become turgid to allow water to pass along it (from cell wall to cell wall by apoplast pathway) so helps water move through plant freely permeable

Answer 5

made of cellulose molecules - polymers of b-glucose cellulose is bundled into microfibrils with multiple h-bonds microfribrils form mesh lattice which is freely permeable thin middle lamella that marks the boundary b/w2 cells & join adjacent cells together with Ca pectate plasmodesmata channels for exchanging substances with adjacent cells in fungi, the cell wall is made of chitin

Answer 6

to change volume to maintain turgidity, giving support to store substances e.g. minerals, pigments, sugars contains enzymes for breaking down molecules isolates unwanted chemicals inside the cell

Answer 7

large, fluid-filled (water) & membrane-bound (tonoplast) the tonoplast is selectively permeable contains hydrolytic enzymes to break down molecules all mature plant cells have a vacuole contains cell sap in cytoplasm

Answer 8

a group of similar, specialised cells that work together to perform a particular function

Answer 9

a group of tissues that work together to perform a particular function

Answer 10

a group of organs that work together to perform a particular function make up an organism

Answer 11

hair-like structure rotates to allow the cell to move

Answer 12

not attached to histone proteins code for polypeptides & genetic information for replication

Answer 13

contains simple, non-membrane-bound organelles aqueous stage where reactions occur

Answer 14

70s site of protein synthesis

Answer 15

protect bacterium from other cells e.g. from immune system allow bacteria cells to stick to each other for protection surrounds cell wall

Answer 16

made of murein/peptidoglycan (glycoprotein) freely permeable supports cell & prevents osmotic lysis

Answer 17

phospholipid bilayer selectively permeable controls movement of substances into & out of the cell

Answer 18

small rings of DNA in the cytoplasm contain several genes e.g. antibiotic resistance that can be transferred to other bacteria cells via pili

Answer 19

distinct nucleus w nuclear envelope vs no true nucleus (DNA as nucleoid in cytoplasm) DNA associated with histone proteins, forming chromatin vs DNA not associated with histone proteins there are no plasmids & DNA is linear vs some DNA might be in circular strands called plasmids contain complex, membrane-bound organelles (RER, SER, mitochondria, GA) vs no membrane-bound organelles chloroplasts might be present vs no chloroplasts, sometimes bacterial chlorophyll associated with CSM 10-100 micrometres vs 1-10 micrometres 80s & 70s ribosomes vs 70s ribosomes only cell wall of cellulose vs cell wall of murein/glycoprotein no outer capsule vs may have slime capsule

Answer 20

acellular/non-living particles they have no metabolism & cannot replicate outside of a host cell

Answer 21

nucleic acids e.g. DNA & RNA (single-stranded) as genetic material but can only reproduce inside living host cells nucleic acid is enclose in a protein coat (capsid), which protects nucleic acid from being digested by host enzymes attachment proteins attach to host cell's receptor protein e.g. gp120 on HIV some viruses (e.g. HIV) have PL bilayer membrane HIV has enzyme called reverse transcriptase

Answer 22

cells of multi-cellular organisms are specialised in different ways to perform a specific function each specialised cell has evolved more or fewer specific organelles & structures to suit its function

Answer 23

muscle cells have many mitochondria to produce ATP needed for powerstroke b/w actin & myosin phagocytes (neutrophils) have many lysosomes root hair cells have many mitochondria for active uptake of minerals via protein pump & H+ co-transporters

Answer 24

1. all cells in an organism e.g. humans are produced by mitotic divisions from the fertilised egg (zygote) so they are genetically identical 2. every cell contains all the genes needed for it to develop into any type of cell, but only some of the genes are expressed in a cell at one time 3. different genes are switched on in each type of specialised cell & the rest of the genes are switched off 4. the cells of a multi-cellular organism have therefore evolved to become more suited to their specific function & perform it more efficiently so the organism functions more efficiently

Answer 25

the number of times larger the image is compared to the actual object

Answer 26

the ability to distinguish b/w 2 separate points that are close together

Answer 27

uses light to form an image uses glass lenses to focus the image the specimen can be alive & held in water/wax/oil light passes through 10-50 micrometre specimen coloured stains are used to give contrast

Answer 28

uses a beam of electrons to form an image uses electromagnets to focus the beam of electrons the specimen is held in a vacuum (to allow e-s to flow) heavy metals are used to stain specimen specimen is dead or dehydrated

Answer 29

electrons pass through a very thin section (50nm) heavy metals (e.g. lead) give contrast denser parts of the specimen absorb more electrons so they appear darker 2d image produced

Answer 30

a beam of electrons is scattered off a gold-covered specimen surface & gathered in a detector to form an image shows the surface of the specimen & 3d image

Answer 31

image can be in colour can view living specimens easier to prepare easier to use cheaper quicker more portable

Answer 32

lower max. resolution of 0.2 micrometres lower max. magnification of x1500 cannot see detail of organelles/ultrastructure

Answer 33

higher max. resolution: TEM 1nm & SEM 20nm higher max. magnification of x500,000 can see detail of organelles/ultrastructure SEM forms 3d image

Answer 34

more expensive more complex & time-consuming preparation (e.g. dehydration) more difficult to use specimens must be dead forms black & white image may create artefacts TEM: sections must be very thin - 50nm only produces 2d image SEM: lower resolution & magnification than TEM

Answer 35

1. epg is placed in eyepiece lens 2. epg calibrated against a known scale (e.g. micrometre slide) for each magnification at low power 1 epg unit = 25 micrometres at medium power 1 epg unit = 10 micrometres at high power 1 epg unit = 2.5 micrometres

Answer 36

1. make solution ice cold, ensure it is isotonic & add buffer solution 2. homogenise the cells to break the CSM & release organelles 3. filter the solution through gauze to remove large cell or tissue debris 4. put solution in centrifuge for ultracentrifugation, starting at low speed 5. heavier organelles are forced to the bottom of the test tube while lighter organelles stay at the top 6. nuclei is separated first bc it is the heaviest organelle, forming a pellet. the supernatant is poured off for the next round of ultracentrifugation 7. the process is repeated at higher speed and for longer until all organelles are separated 8. the order of separation is: nucleus, chloroplasts, mitochondria & lysosomes, ER & ribosomes

Answer 37

ice-cold: reduce enzyme activity/digestion isotonic: no water potential gradient so no net osmosis so cell not damaged by bursting or shrinking buffered: maintain pH so proteins are not denatured

Answer 38

the division of the nucleus into 2 genetically identical nuclei then, the cytoplasm & csm divide to form 2 genetically identical daughter cells

Answer 39

growth - increase in cell number repair & replacement of damaged/worn out cells e.g. skin cells asexual reproduction e.g. cloning plants producing genetically identical daughter cells to maintain the genome

Answer 40

to ensure cell division happens when needed & to prevent it from happening when it is not needed

Answer 41

1. interphase 2. mitosis 3. cytokinesis

Answer 42

cell increases in size/biomass DNA replicates, chromosomes are copied cell actively synthesises proteins & organelles ATP produced to release energy for cell division

Answer 43

nucleus divides sister chromatids separate pmat: prophase, metaphase, anaphase, telophase

Answer 44

chromosomes condense & become visible each chromosome is in the form of 2 identical sister chromatids joined at the centromere nuclear envelope breaks down & nucleolus disappears so chromosomes are free in cytoplasm centrioles move to opposite poles & form spindle fibres that extend to the equator of the cell

Answer 45

chromosomes move to equator spindle fibres attach to centromere of the chromosomes (the kinetochore)

Answer 46

spindle fibres shorten & poles move apart centromeres divide sister chromatids separate & are pulled to opposite poles of the cell (v shape) there is complete set of chromosomes at each pole ATP required - mitochondria around spindle fibres

Answer 47

chromatids at the poles uncoil into chromatin & are not visible each pole has identical copies of each chromosome spindle fibres break down nuclear envelope & nucleolus reform around chromosomes @ each pole so 2 nuclei formed

Answer 48

contractile ring forms cytoplasm divides csm divides in plant cells, new cell wall plates form *to form 2 genetically identical daughter cells*

Answer 49

p: random arrangement m: lined up on equator a: v shape - pulled apart t: at 2 poles

Answer 50

measure of how fast a tissue is dividing/growing = ratio of cells undergoing mitosis useful for cancer calculations cells in mitosis/total number of cells

Answer 51

group of diseases caused by uncontrolled division & growth of cells bc of mutation of genes that regulate mitosis & cell cycle so a group of abnormal cells forms a tumour that constantly expands in size

Answer 52

non-cancerous localised in one area grow slowly cells resemble the tissue they originate from often harmless unless *see other card can be surgically removed

Answer 53

cancerous cells break off primary tumour & travel through bloodstream to form secondary tumours in other parts of the body = metastasis difficult to treat/find& remove cells do not resemble tissue they originate from cells do not die catabolic

Answer 54

invade healthy tissue which causes: pressure on surrounding cells (e.g. brain tumours) which affects normal function pressure on blood vessels/nerves supplying healthy tissues pressure on airways in lungs

Answer 55

exposure to radiation - x-ray, gamma ray, uv age - increased cell division w age so increased chance of mutation lifestyle - smoking & alcohol ingesting carcinogens e.g. tar & asbestos viruses e.g. HPV, hep B & C

Answer 56

environment of the cell growth factors controlled by 2 types of regulatory genes checkpoints of the cell cycle are closely regulated - g1, s & g2 e.g. proto-oncogenes & tumour-suppressor genes

Answer 57

killing dividing cells by blocking part of the cell cycle chemotherapy - drugs used to treat cancer disrupt cell cycle by: preventing DNA replication inhibiting metaphase by interfering w spindle formation targeting rapidly dividing cells so also kills healthy cells

Answer 58

binary fission 1. single loop of DNA replicates both copies attach to csm plasmids replicate 2. csm grows & elongates b/w the 2 DNA molecules it pinches inwards, dividing cytoplasm into 2 3. new murein cell wall forms b/w 2 DNA molecules forming 2 nearly genetically identical daughter cells each w single copy of DNA & variable # of plasmid copies

Answer 59

bacterial population = # at start x 2^# of divisions

Answer 60

1. attach to host cell using attachment proteins on their surface 2. inject their nucleic acid (RNA or DNA) into host cell 3. genetic information on injected viral nucleic acid provides gene instructions for host cell to make new viruses by producing viral components (proteins & nucleic acid)

Answer 61

a molecule recognised as foreign by the immune system, which stimulates a specific immune response - the production of antibodies

Answer 62

on the surface of: pathogens e.g. bacteria csm, cell wall or virus' capsid viral infected cells - (apc) cell will present viral antigens on its csm to signify distress transplant organs - tissue matching & immunosuppressant drugs needed cancer cells - DNA mutations may create antigens toxins produced by bacteria

Answer 63

pathogens cells from other organisms of the same species abnormal body cells toxins

Answer 64

non-specific defence system: gives immediate, initial response/barrier to infection 1. physical (skin, mucus) & chemical (acid, enzymes) barriers 2. phagocytosis specific defence system can distinguish b/w antigens slower to act during the first infection by a pathogen/ag bc cell division takes time faster responses to reinfection by the same pathogen/ag so host does not suffer symptoms - so immune 1. cell-mediated response by t lymphocytes (t helper cells & t cytotoxic cells) 2. humoral response by b lymphocytes (antibody production in bloodstream)

Answer 65

lymphocytes phagocytes

Answer 66

phagocyte attracted to pathogen by chemicals & recognise ag (stimulated by cytokines) attachment to ag with receptors endocytosis/engulfing pathogen the pathogen is enclosed in a phagosome lysosomes containing lysozyme fuse with phagosome (to become a phagolysosome) enzymes hydrolyse/digest pathogen ag presented on phagocyte csm (apc)

Answer 67

the pathogen has antigens on its surface the pathogen is engulfed by a phagocyte in phagocytosis phagocytes present antigens to b cells cytokines activate complementary b cells & stimulate phagocytosis clonal selection of b lymphocytes with receptors complementary to antigens & b cells divide by mitosis to form clones (clonal expansion) differentiate into plasma cells that produce monoclonal antibodies (stim. by cytokines) the antibodies are specific & complementary to the antigen & bind to destroy the pathogen many b cells become memory cells, remain in lymph nodes/blood & give immunity

Answer 68

the pathogen has antigens on its surface the pathogen is engulfed by a phagocyte in phagocytosis phagocytes present antigens th cells release cytokines that stimulate other parts of the specific immune response clonal selection of specific th & tc cells with receptors complementary to antigens th & tc cells divide by mitosis to form clones (clonal expansion) tc cells activated tc cells attach their complementary receptor to the antigen (in csm of ag presenting or infected cell) tc cells produce a protein (perforin) that creates holes in csm so it becomes freely permeable - therefore the infected cell dies & viruses inside are destroyed many th & tc cells become memory cells, remain in lymph nodes/blood & give immunity

Answer 69

stimulate & activate other parts of the immune response by releasing cytokines e.g. to stimulate phagocytosis & to activate B cells & killer T cells

Answer 70

present antigens of the pathogen on csm tc cells bind to apc to kill them

Answer 71

proteins with specific binding sites to a particular antigen, which are synthesised by plasma b cells

Answer 72

antibody binding sites are complementary to a specific antigen 4 polypeptide chains (2 short, 2 long) - quaternary structure joined by disulfide bonds each antibody has 2 variable regions, which are determined by a unique primary structure complementary to each antigen 2 specific ag binding sites that form antibody-antigen complexes different primary structure on different antibodies constant regions act as markers for phagocytosis every antibody has constant regions with the same primary structure

Answer 73

form ab-ag complex agglutination - cluster apc together so easier to engulf in phagocytosis constant regions act as markers that phagocyte receptor proteins bind to, which triggers endocytosis of the pathogen antitoxin antibodies bind to bacterial toxins to neutralise them, making them harmless

Answer 74

primary response is slow, weak & short-lasting low conc. of abs in blood host suffers symptoms b, th & tc memory cells formed secondary response to reinfection by the same pathogen is faster, stronger & longer-lasting higher conc. of abs in blood bc memory b cells & plasma cells produce more antibodies & faster

Answer 75

dead or inactive form of the pathogen or antigens stimulate specific immune response production of b, th & tc memory cells active immunity upon reinfection by the same pathogen, the immune response is faster, stronger & longer-lasting

Answer 76

if a sufficient number of the people/proportion of the population are vaccinated against a disease, the pathogen will not be transmitted from one host to another

Answer 77

production & testing may be done with animals risks/side effects vs benefits must be tested on humans to test toxicity vaccines are expensive - should they be made free on the NHS? should vaccines be compulsory?

Answer 78

active involves memory cells vs passive does not active involves production of antibodies by plasma memory cells passive involves antibody being introduced from another source active is long term bc antibody is produced in response to antigen passive is short term bc antibody is broken down active can take time to develop vs passive is fast acting

Answer 79

retrovirus - RNA & genes non-living - does not metabolise, acellular 2 RNA strands - code for 13 proteins capsid - protein coat membrane derived from host th cell reverse transcriptase converts RNA into viral DNA attachment proteins of surface e.g. gp120

Answer 80

1. binding of attachment protein gp120 to receptor protein on Th cells 2. triggers fusion of viral envelope to csm 3. viral RNA enters cytoplasm 4. reverse transcriptase converts RNA into viral DNA 5. viral DNA is inserted into host DNA by integrase 6. viral mRNA is made & exits nucleus 7. host ribosomes translate viral mRNA into viral proteins 8. new viral assembly & host cell lysis

Answer 81

reverse transcriptase uses HIV RNA to make DNA copy viral DNA is joined to host cell’s DNA viral DNA is used to make HIV RNA copies & HIV capsid proteins/enzymes made at host ribosomes assembly of new virus particles budding off from host cell membrane host cell is destroyed

Answer 82

not enough T-cells to activate B-cells so reduced antibody production & less effective immune response memory cells destroyed person more prone to opportunistic infections or cancer e.g. pneumonia

Answer 83

antibiotics stop metabolism but viruses do not have a metabolism viruses are within host cells so antibiotics cannot access them antibiotics work against cell components e.g. ribosomes which viruses do not have

Answer 84

medical diagnosis targeting medication to specific cell types by attaching a therapeutic drug to an antibody

Answer 85

1. urine passes through reaction zone 2. HCG hormone binds to the mobile mAb that is specific to it 3. (it passes up the stick) HCG binds to the immobilised HCG antibodies in the result window 4. mobile HCG antibodies which DO NOT attach to HCG 5. bind to immobilised antibodies in the control window 6. blue dye appears in both the control & result windows, showing a +ve result

Answer 86

expensive side effects use of animals in production

Answer 87

1. HIV antigens are attached to a test well in a dish 2. a sample of blood plasma is added to the well. if HIV antibodies are present, they bind to the HIV antigens 3. the well is washed to remove unbound HIV Abs. a second antibody with an enzyme attached is then added (made by injecting mouse w HIV antibody) & enzyme-linked Ab binds to anti-HIV Abs 4. the well is washed again to remove unbound enzyme-attached Abs. a yellow substrate solution is added, which changes to blue if the enzyme is present. a blue colour shows the person has HIV antibodies

Answer 88

AIDS is the symptom so would need a different test must look at Th cell count, which would be low in a person with AIDS

Answer 89

1. known antibody is absorbed (stuck) to the test well in a dish 2. the patient’s sample is added detection of unknown antigen/pathogen due to ag-ab complex 3. sample washed to remove unbound antigens 4. enzyme-linked ab is added (complementary to ab-ag complex so will bind) then washed to remove unbound enzyme-linked abs 5. substrate added, which will bind to enzyme-linked ab & cause colour change to blue = antigen is present

Answer 90

use calibration curve & colorimeter

Answer 91

controlling entry & exit of substances into/out of organelles separating cell components from cytoplasm so specific reactions can take place in specific organelles - isolation & creating optimum conditions holding components of some reaction in place e.g. ribosomes on RER, ETC regulating the transport of materials into & out of cells - transport medium e.g. Golgi vesicles provide an internal transport system e.g. RER, SER isolate potentially damaging enzymes from other cellular content e.g. hydrolytic enzymes in lysosomes

Answer 92

fluid: components can move laterally & membrane is flexible/self-sealing mosaic: pattern of proteins of varying size as seen on SEM

Answer 93

water hydrophilic phosphate head hydrophobic fatty acid tails cholesterol intrinsic channel protein (spans bilayer) intrinsic carrier protein extrinsic protein glycocalyx - glycoprotein & glycolipids

Answer 94

see booklet

Answer 95

not lipid-soluble/polar so cannot pass through phospholipid bilayer too large to pass through channels in the membrane same charge as the charge on protein channels so are repelled charged ions so cannot pass through non-polar hydrophobic FA tails in PL bilayer

Answer 96

1. ethanol - lipid-soluble ethanol dissolves lipid so damages membrane increases membrane permeability 2. temperature increased temp. = increased KE = increased movement of phospholipids & other components = increased fluidity & permeability of the membrane --> affects membrane proteins' position & sometimes function 3. channel & carrier proteins - selectively permeable how many of a certain type of molecule is let through

Answer 97

diffusion is the random movement of particles from a region of higher concentration to a region of lower concentration, down a conc. grad. no carrier or channel protein

Answer 98

rate of diffusion α SA x difference in conc. (conc. grad.) ---------------------------------------------------- diffusion distance fast = big/small rate of diffusion is proportional to SA & diffusion gradient rate of diffusion is inversely proportional to diffusion distance

Answer 99

movement of particles down conc. grad. (passive), but requires intrinsic transport proteins 1. channel proteins form hydrophilic channels across the membrane that allow water-soluble/polar/charged ions & molecules e.g. glucose & AAs to pass through membrane channels are selective & specific - each channel only opens in the presence of a specific molecule 2. carrier proteins these change shape when a specific molecule binds to it, allowing molecules to move from higher to lower conc. no external energy is needed (passive) increased # transport proteins = increased permeability of membrane

Answer 100

the movement of molecules or ions into or out of a cell from a region of lower conc. to region of higher conc. using ATP hydrolysis & carrier proteins (conformational change in shape) against conc. grad.

Answer 101

1. molecule or ion binds to receptor sites on the carrier protein 2. on the inside of the cell/organelle, ATP binds to the protein & ATP is hydrolysed into ADP + Pi 3. this causes the protein to change shape (3y structure) & opens to the opposite side of the membrane 4. the molecule/ion is released to the other side of the membrane 5. ADP + Pi is released (recombines --> ATP) from the protein so protein reverts to original shape & process is repeated