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Cells Flashcards

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1
Q

what is a tissue?

A

a group of cells working together to perform a particular function

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2
Q

what is an organ?

A

a group of tissues to carry out a particular function

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3
Q

what is an organ system?

A

a group of organs which carry out a particular function

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4
Q

what is a eukaryotic cell?

A

a cell that has a nucleus that is membrane-bound

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5
Q

label this animal cell

A
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6
Q

label this mitochondria and give its function

A

the mitcohondria is the site of aerobic respiration which forms atp- note mitochondria have 70s ribosomes unlike eukaryotic cells which have 80s ribosomes

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7
Q

label this plant cell

A
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8
Q

label this chloroplast

A
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9
Q

label this algal cell

A

lol no point same as plant cell but different shaped and sized chloroplasts

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10
Q

label this fungal cell

A

lol no point same as plant cell but cell wall is made of chitin not cellulose and no chloroplasts

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11
Q

what is the structure and function of the nucleus?

A

it contains the genetic material in the form of chromatin made of dna wrapped around histone proteins. when chromatin’s condensed, it forms chromosomes.
it has a nuclear envelope with nuclear pores which allows passage of molecules eg. rna in and out. the nucleolus makes ribosomes

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12
Q

what is the difference between dna in eukaryotes and prokaryotes?

A

dna in eukaryotes is long, linear, associates with histone proteins, contains introns and forms chromosomes

dna in prokaryotes is short, circular, doesn’t associate with histone proteins, doesn’t contain introns or form chromosomes

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13
Q

what is the structure and function of mitochondria?

A

mitochondria carry out aerobic respiration producing atp. they have a double membrance, and the inner membrane folds in to form cristae which increases surface area for the attachment of enzymes and proteins involved in aerobic respiration.

the matrix contains enzymes involved in aerobic respiration.

mitochondria have their own dna and ribosomes used to make enzymes for aerobic respiration

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14
Q

what is the structure and function of chloroplasts?

A

they absorb light for photosynthesis.
they have a double membrane and also have membranes called thylakoids which contain chlorophyll.
the thylakoids are stacked up to form grana which increase surface area of light absorption.
stroma is a fluid which contains photosynthesis enzymes.
chloroplasts contain their own dna and 70s ribosomes to make photosynthesis enzymes.
chloroplasts contain starch grains which store photosynthesis products (glucose) as starch.

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15
Q

what is the structure and function of ribosomes?

A

they carry out protein synthesis using mRNA and tRNA.
they’re made of ribosomal RNA (rRNA) and protein- each one is made of 2 sub-units.
they’re found in the cytoplasm or attached to the R.E.R
eukaryotic cells contain 80s, prokaryotes contain 70s

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16
Q

what is the structure and function of rough endoplasmic reticulum?

A

they’re made of membranes and form a series of flattened sacs called cisternae.
the R.E.R has ribosomes on its outer surface, they synthesise proteins which are transported through the cell by the R.E.R

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17
Q

what is the structure and function of smooth endoplasmic reticulum?

A

they’re made of membranes and form a series of flattened sacs called cisternae.
they synthesise and transport lipids

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18
Q

what is the structure and function of golgi apparatus?

A

it processes, modifies and packages proteins into vesicles, for transport out of the cell.
the membrane sacs are fluid filled and bud off smaller sacs (vesicles) which contain modified proteins. they can form lysosomes.
also modifies, processes, transports proteins

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19
Q

which is the structure and function of lysosomes?

A

they are vesicles containing enzymes called lysozymes which hydrolyse old organelles/ cells that aren’t needed any more.
some types of white blood cells contain many lysosomes, as they hydrolyse foreign pathogens

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20
Q

what is structure and function of the cell-surface membrane?

A

also referred to as plasma membrane.
it controls passage of molecules in and out of cell
it’s made of phospholipids, proteins and carbohydrates arranged into a fluid mosaics model.

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21
Q

what is the structure and function of microvilli?

A

they’re formed by the folding of the cell-surface membrane which increases surface area.
only certain cell types have microvilli eg epithelial cells on small intestine

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22
Q

what is the structure and function of centrioles?

A

they spindle fibres used in cell division

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23
Q

what is the structure and function of vacuole?

A

only in plant cells, it contains cell sap. its surrounding membrane is the tonoplast.
it helps maintain pressure keeping the cell turgid and stops the plant wilting.
it’s also involved in the isolation of unwanted chemicals inside the cell

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24
Q

give examples of specialised cells

A

epithelial cells in the small intestine:
contain microvilli to increase sa for abrosption
have many mitochondria to provide atp for active transport

red blood cells:
no nucleus so more room for haemoglobin so more oxygen carried

sperm cells:
lots of mitochondria to large amounts of atp to propel them to egg

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25
Q

label this prokaryotic cell

A

note only SOME prokaryotic cells contain plasmids, slime capsule and flagella

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26
Q

what is the cell wall of prokaryotes made of?

A

murein

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27
Q

what is the function of the slime capsule?

A

helps to protect bacteria from attack by cells in the immune system

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28
Q

what is the function of plasmids?

A

they’re small dna loops that aren’t part of the main circular bit.
they contain genes for stuff like antibiotic resistance

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29
Q

what is the function of the flagellum?

A

rotates, thingy can move lol

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30
Q

label this virus

A

genetic stuff in viruses can be either dna or rna BUT in hiv its only rna do not ever say oh it might contain dna becuase it doesnt rna only

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31
Q

what are the principles and limitations of optical microscopes?

A

principles:
specimens are illuminated with light focussed using lenses
specimens can be living / dead, often need to be stained eg methylene blue binds to dna making nuclei visible, or potassium iodide to see chloroplasts

limitations:
lower resolution because light has a longer wavelength than electrons, and max magnification of x1500, so only large organelles eg nuclei can be viewed, not smaller like ribosomes

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32
Q

what are the principles and limitations of electrons microscopes?

A

principles:
uses abeam of electrons to see specimen
much higher resolution so can see small shtuff like E.R and ribosomes

limitations:
specimens must be dead becuase they’re in a vacuum
more complex staining process with electron-dense chemical eg gold
very thin specimen
artefacts are common

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33
Q

describe a transmission electron microscope

A

transmits a beam of electrons through specimen
highest resolution
only produces 2d image

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34
Q

describe a scanning electron microscope

A

scans beam of electrons onto specimen surface
lower resolution than tem but higher than light
gives 3d image

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35
Q

what is the equation for magnification?

A

mag= image length/ actual length

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36
Q

explain cell fractionation and ultracentrifugation

A

1) homogenise the tissue to break open the cells and release the organelles. do this in a cold (reduce enzyme action due to reduced kinetic energy that could damage organelles), isotonic (prevent water movement into organelles via osmosis so organelles don’t lyse), buffered (maintain pH so don’t denature organelle proteins) solution.

2) filter proteins to remove cell debris and unbroken cells

3) centrifuge the solution at low speed, nuclei are separated and form a pellet. remove the pellet and transfer the supernatant into another tube.

4) centrifuge faster and longer

5) order of pellets:
nuclei
chloroplasts (plants only)
mitochondria
ribosomes

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37
Q

what is a chromosome?

A

one dna molecule folded into a condensed form, wrapped around histone proteins in eukaryotes, made of 2 genetically identical sister chromatids attached at the centromere

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38
Q

how does dna fit into every cell?

A

the dna condenses by wrapping itself around histone proteins. they are known together as chromatin. the dna supercoils into a chromosome

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39
Q

what kinda cells have homologous chromosomes?

A

all cells except gametes

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40
Q

what are homologous chromsomes?

A

they have the same genes but different alleles.

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41
Q

what are diploid cells?

A

cells with homologous pairs of chromosomes- diploid is represented as 2n.

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42
Q

are gametes haploid or diploid/

A

haploid- they only have one copy of each homologous pair of chromosomes

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43
Q

can specialised or unspecialised cells divide?

A

unspecialised cells can divide- when a cell is fully differentiated it can’t divide

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44
Q

what are the 3 stages the cell cycle consists of?

A

1) interphase, 2) mitosis (prophase, metaphase, anaphase, telophase), 3) cytokinesis

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45
Q

describe the interphase + draw a diagram (remember chromsomes aren’t visible in interphase, only the chromatin)

A

the interphase is the time when the cell isn’t dividing. during interphase: 1) new proteins are synthesized eg enzymes, 2) dna replicates, 3) new organelles made

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46
Q

what is mitosis?

A

the process which the cell undergoes to produce two genetically identical cells with identical copies of dna produced by the parent cell during interphase

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47
Q

why is mitosis important?

A

1) it allows the organism to grow
2) it allows the organisms to replace cells in order to repair tissues
3) results in genetically identical cells
4) asexual reproduction in some organisms (not prokaryotes)

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48
Q

describe prophase + draw a diagram

A

1) the nuclear membrane breaks down
2) centrioles move to the poles of the cells + make spindle fibres
3) the chromosomes condense and become visible.

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49
Q

describe metaphase + draw a diagram

A

1) spindle fibres attach to the centromere of each chromosome
2) the chromosomes are moved to the equator of the cell by the spindle fibres

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50
Q

describe anaphase + draw a diagram

A

1) the centromere divides
2) the spindle fibres contract, sister chromatids are pulled apart to opposite poles of the cells
3) the chromatids were identical, so we end up with identical chromosomes at each poles

51
Q

describe telophase + draw a diagram

A

1) chromosomes have reached the poles and the spindle fibres break down
2) a new nuclear membrane forms around each group of chromosomes
3) the chromosomes un-condense and begin to form chromatin again
4) the cell begins to divides

52
Q

describe cytokinesis + draw a diagram

A

the cytoplasm divides, producing 2 genetically identical daughter cells

53
Q

what is cancer (basic definition)?

A

uncontrolled cell division, caused by mutations in genes that disrupt mitosis

54
Q

name 4 properties of cancerous cells

A

1) divide uncontrollably
2) have a shorter cell cycle
3) divide more often
4) are unspecialised and have no function

55
Q

how do tumours cause damage?

A

by damaging organs or blocking blood vessels to organs

56
Q

many cancer treatments targets parts of the cell cycle, name 3 parts that would be lit to target imo

A

1) dna replication (disrupts interphase)
2) spindle formation/ contraction (prevents metaphase/ anaphase)
3) cytokinesis

57
Q

how could cancer treatments cause side effects?

A

they can’t always distinguish tumour cells from normal lit ones, so can also kill healthy body cells HOWEVER tumour cells divide very frequently so treatments target tumour cells more

58
Q

what is a tumour?

A

a mass of cells that is created because of uncontrolled cell division, can be benign or malignant

59
Q

how to prokaryotic cells divide + describe the process?

A

binary fission
1) the circular dna + plasmids replicate
2) copes of circular dna move to opposite poles of the cell
3) the cytoplasm divides to produce 2 daughter cells
4) each cell contains a single copy of the circular dna but a variable number of plasmids (if cell contains plasmids)

60
Q

how do viruses replicate?

A

bc they’re acellular, they don’t undergo cell division, instead they use a specific host cell:
1) the virus attachment protein binds to a specific complementary protein on a specific host cell
2) the viral dna/ rna is injected into the host cell
3) the host cell uses the viral dna/ rna to synthesise its own ribosomes and enzymes to synthesise viral proteins
4) the viral proteins are formed and released from the host cell

61
Q

what is the host cell of hiv?

A

the human helper t cell

62
Q

how do you calculate mitotic index?

A

number of cells with visible chromosomes (in mitosis) / total number of cells

63
Q

how do phospholipids form a bilayer?

A

the hydrophilic phosphate heads face in contact with water.
the hydrophobic fatty acid tails face inside, away from water

64
Q

what is the other name for the cell-surface membrane?

A

plasma membrane

65
Q

what are the components of the plasma membrane?

A

the phospholipid bilayer plus proteins, glycoproteins, glycolipids and cholesterol

66
Q

why is the membrane called the fluid-mosaic model?

A

fluid- the components can move around within the membrane
mosaic- due to the pattern produced by the proteins embedded through the membrane

67
Q

is the plasma membrane fully or partially permeable?

A

partially

68
Q

which molecules can diffuse straight through the phospholipid bilayer?

A

small, non-polar, lipid-soluble molecules (eg CO2, O2)

69
Q

which proteins are in the plasma membrane?

A

1)transport proteins- channel and carrier
2) enzymes eg disaccharidases
3) receptor proteins (bind complementary molecules to cause a response)
4) antigens (determine if a cell is foreign to initiate an immune response)

70
Q

what is the function of cholesterol in the plasma membrane?

A

reduced the fluidity of it by restricting movement of the other molecules, makes it more rigid

71
Q

what is the function of channel proteins?

A

used in facilitated diffusion- forms a water filled channel for molecules like ions to move through

72
Q

what is a function of carrier proteins?

A

used in facilitated diffusion and active transport- amino acids and glucose bind specifically to a carrier protein binding site .
sometimes need atp energy to change shape so involved in active transport

73
Q

what is diffusion in terms of the plasma membrane?

A

the passive net movement of small, non-polar, lipid-soluble molecules from a higher concentration to a lower concentration down a concentration gradient

74
Q

what is facilitated diffusion?

A

the passive net movement of larger, charged, water-soluble molecules from a higher concentration to a lower concentration down a concentration gradient, using channel or carrier proteins

75
Q

which factors affect the rate of diffusion?

A

1) size of concentration gradient
2) surface area the diffusion is occurring across
3) thickness of of diffusion pathway
4) number of channel/carrier proteins for FD

76
Q

what is active transport?

A

the movement of substances against their concentration gradient using extra energy from the hydrolysis of ATP and a carrier protein

77
Q

what is osmosis?

A

the passive net movement of water molecules from an area of high water potential to an area of low water potential down a water potential gradient, across a partially permeable membrane, through aquaporins

78
Q

what is the water potential of pure water?

A

0

79
Q

what happens to the water potential of pure water when solutes are added?

A

it becomes more negative

80
Q

what is water potential measured in?

A

kPa

81
Q

what is an isotonic solution?

A

has same water potential as inside the cell- no net movement of water in or out of cells

82
Q

what is a hypertonic solution?

A

lower water potential than inside the cell- water moves out of cell-in animal cells the cells crenates, in plant cells the cell becomes flaccid then plasmolyses when cell wall starts pulling away

83
Q

what is a hypotonic solution?

A

higher water potential than inside the cell- water moves out of cell- in animal cells the cell lyses, in plant cells the cell is turgid

84
Q

what is co-transport?

A

1) Na+ ions are actively transported out of the epithelial cells into the blood, using a carrier protein and energy from the hydrolysis of ATP
2) lowers the concentration of Na+ ions in the cell
3) Na+ and glucose move into the cell at the same time from the lumen of the small intestine into the epithelial cells down a Na+ ion concentration gradient using a carrier protein.
4) glucose moves into the blood by facilitated diffusion, using a carrier protein, down a concentration gradient

85
Q

what is an pathogen?

A

an organism that causes disease

86
Q

give examples of pathogens

A

viruses, bacteria, fungus

87
Q

how do pathogens cause disease?

A

destroying cells and tissue/ producing toxins

88
Q

what is an antigen?

A

a molecule, usually protein, with a specific tertiary structure, found on the surface of cells that stimulate an immune response

89
Q

which 4 things are antigens allow the immune system to identify?

A

1) pathogens
2) abnormal body cells eg cancer cells
3) toxins (molecules not cells)
4) cells from other individuals of the same species

90
Q

describe the process of phagocytosis

A

1) a phagocyte recognises foreign antigens on a pathogen
2) the phagocyte engulfs the pathogen, forming a vesicle called a phagosome
3) lysosomes fuse with the phagosome, releasing lysozymes which hydrolyse the molecules of the pathogen to destroy it
4) the antigens of the pathogen are presented on the cell surface membrane of the phagocyte, it has now become an antigen presenting cell

91
Q

what are lymphocytes?

A

they are white blood cells that carry out specific immune responses

92
Q

describe the cellular response (T cells)

A

1) an antigen on the cell surface membrane of an antigen presenting phagocyte binds to a complementary receptor on a specific helper T cell
2) this stimulates: more phagocytes, B-cells and cytotoxic T cells (which kill infected cells)

93
Q

describe the humoral response (B cells)

A

1) B cells clone/ divide by mitosis into plasma cells and memory B cells.
2) Plasma cells secrete many identical antibodies which bind to complementary antigens and agglutinate pathogens

94
Q

what is agglutination?

A

where antibodies bind to 2 antigens on different pathogens, causing them to clump and be held in one area. this makes pathogens more easily engulfed and hydrolysed by phagoctyes

95
Q

what are monoclonal antibodies?

A

antibodies with the same tertiary structure which are complementary to and bind to one type of antigen, and come from the same type of B cell

96
Q

what is the purpose of memory B cells?

A

if re-infected with the same antigen, they bind to the antigen, clone into plasma cells and produce many more antibodies much more quickly.

97
Q

draw and label the structure of an antibody

A
98
Q

how many polypeptide chains do antibodies have, and how are the held together?

A

4 polypeptide chains, 2 light, 2 heavy. they are held together by disuplhide bonds

99
Q

what are the constant regions and variable regions in antibodies?

A

the constant region has the same tertiary structure in all antibodies.
the variable region contains the binding site and differs in all antibodies making them complementary to only on type of antigen

100
Q

what is the name for an antibody binded to an antigen?

A

an antibody-antigen complex

101
Q

what is the primary immune response?

A

when the antigen infects the body for the first time. antibodies are produced more slowly and there are less of them because it takes time for B cells to clone into plasma cells. symptoms occur

102
Q

what is the secondary immune response?

A

when the same antigen re-infects. it is bigger and faster because the specific memory B cells with complementary antibody, clone much faster and produce antibodies much more quickly. no symptoms occur.

103
Q

what is a vaccine?

A

they make an individual immune to an antigen.

104
Q

how do vaccinations work?

A

1) vaccines contain antigens of pathogen, which are presented on the cell surface membrane of a phagocyte
2) specific helper t cells activate specific helper b cells, which clone into plasma cells and memory b cells
3) plasma cells make antibodies which bind to the antigen and cause its destruction
4) when re-infected, specific memory B cells with complementary antibodies to the antigen they recognise. they then clone into plasma cells, which produce many more antibodies much more quickly

105
Q

what is herd immunity?

A

if most people are vaccinated, this provides protection for the whole population. those who aren’t vaccinated are still protected because they are less likely to come into contact with infected individuals

106
Q

name ethical issues with vaccines

A

1) development and testing involves animals
2) human testing may put people in harm
3) vaccine may have side effects
4) who should receive the new vaccine first

107
Q

describe antigenic variability

A

due to dna mutations, the tertiary structure of the antigen changes. if a pathogen re-infects the body, the antibody binding sites from memory cells may not be complementary and a secondary response will not occur

108
Q

describe active immunity

A

primary immune response stimulated by an antigen leading to antibody production. this takes more time than passive.
a natural form is from infection, an artificial form is from a vaccine

109
Q

describe passive immunity

A

antibodies are introduced to the body from outside source, this is quicker than active because the immune system doesn’t make the antibodies.
a natural form is when babies receive antibodies from their mother’s milk.
an artificial form is an injection of pre-formed antibodies

110
Q

name advantages and disadvantages of active immunity

A

adv- long term protection as memory cells are made

dis- artificial can only be given before getting the disease, takes more time, natural will get symptoms

111
Q

name advantages and disadvantages of passive immunity

A

adv- can be given after exposure to antigen + works straight away

dis- doesn’t last long as antibodies broken down, no memory cells produced

112
Q

describe how monoclonal antibodies are used in treating cancer + why they have minimal side effects

A

monoclonal antibodies can be made to have specific variable regions, which are complementary to and bind to specific antigens on the cancer cells. the antibody is linked to a toxin which kills the cancer cell.
they have minimal side effects because the antibody will bind to antigens on cancer cells, and won’t bind to or damage healthy cells

113
Q

describe how monoclonal antibodies are used in pregnancy tests

A

hcg is a protein found only pregnant women’s urine
1) the test strip contains an hcg monoclonal antibody with a coloured dye attached
2) an hcg in the urine will bind to the monoclonal antibody
3) the hcg antibody complexes in the dye binds to the fixed hcg antibodies and cause the colour to appear
4) if there is no hcg, the hcg antibodies don’t bind to the fixed antibodies
5) fixed antibodies show it worked

114
Q

describe how monoclonal antibodies diagnose disease using tissue samples

A

monoclonal antibodies complementary to the antigens on cancer cells can be used in cancer diagnosis on biopsy tissue samples. the complementary antibody for the cancer antigen has a fluorescent tag which shows on a microscope. the dark cells show where antibodies have bound to cancer cell antigens

115
Q

describe how ELISA detect HIV antibodies

A

1) HIV antigen is bound to a well bottom
2) a patient’s blood plasma is added
3) any HIV antibodies will bind to the HIV antigens stuck to the bottom of the well (primary antibodies)
4) the well is washed to remove any unbound antibodies
5) secondary antibodies with a specific enzyme attached to it is added
6) the secondary antibody can bind to the HIV-specific antibody
7) well is washed out to remove any unbound secondary antibodies
8) if there are no primary antibodies, the secondary antibodies won’t bind and be washed away
9) a solution is added and contains a substrate which can react with the enzyme on the secondary antibody + produces a colour

116
Q

what are ethical to do with using monoclonal antibodies?

A

1) involves inducing tumours in mice
2) mice can sometimes be genetically engineered to produce human antibodies
3) there have been some examples of human volunteers suffering unexpected side effects

117
Q

what is HIV?

A

human immunodeficiency virus is a retrovirus which infects and kills helper t-cells, reducing effectiveness of immune response

118
Q

draw the structure of hiv

A

attachment protein- attaches virus to complementary receptor on host helper t cell
rna- genetic material
reverse transcriptase- enzyme which converts rna into dna in host cell
capsid- made of protein
lipid envelope- outer layer of membrane taken from previous host cell

119
Q

how does hiv replicate?

A

1) attachment protein on hiv binds to a complementary receptor on the helper t cell
2) capsid enters the cell and releases rna into the cytoplasm
3) reverse transcriptase makes dna from the hiv rna
4) using the host cells enzymes and ribosomes for protein synthesis, viral proteins made
5) new virus particles formed from proteins which bud from the cell and infect more helper t cells

120
Q

how does hiv lead to aids, and how this leads to patient death?

A

hiv kills helper t cells, when helper t cell numbers drop significantly the immune system starts to fail. first minor infections occur, then more serious infections. when t cell numbers become seriously low, serious infections can kill the patient.

specific b cells aren’t activated, don’t clone into plasma cells and antibodies aren’t produced. cytotoxic b cells aren’t activated and don’t kill infected cells. pathogens aren’t destroyed so continue to divide

121
Q

why are antibiotics not given for viral infections?

A

they only treat bacterial infections, because they target things like bacterial cell wall

122
Q

why don’t antibiotics kill human cells?

A

bacterial enzymes + ribosomes are different to human ones

123
Q

why are viruses described as acellular and non-living?

A

acellular: no cell-surface membrane
non-living: don’t undergo metabolic reactions

Biology A-Level (17 decks)

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