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Cells Flashcards

1
Q

what are the distinguishing features of a Eukaryote

A
  • So DNA enclosed in a nucleus
    -cytoplasm containing membrane bound organelles.
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2
Q

describe the structure of a cell surface membrane

A

-hydrophilic phosphate heads
-hydrophobic fatty acid tails
-protein channels
which form a phospholipid bilayer

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3
Q

describe the function of the cell-surface membrane

A

-partially permeable so enables the control of passage of substances in and out the cell
-molecules, receptors and antigens on surface which allows for cell recognition and signaling

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4
Q

describe the structure of the nucleus

A

-nuclear envelope- double membrane and has nuclear pores
-histone bound linear DNA

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5
Q

what is the function of the RER

A

-ribosomes on surface synthesise proteins and then are processes and transported to RER. Proteins are then packaged into the vesicles for transport

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6
Q

describe the function of the SER

A

synthesise and processes lipids

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7
Q

What is the function of the gogli body?

A

Golgi apparatus processes and packages proteins and lipids and also produces lysosomes.

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8
Q

Define Eukaryote

A

DNA is contained within the nucleus, and contains membrane-bound specialised organelles.

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9
Q

what are distinguishing features of Prokaryotic cells

A

cytoplasm lacks membrane bound organelles so genetic material is not enclosed in a nucleus

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10
Q

compare and contrast the structure of a Prokaryotic cells and Eukaryotic cells

A

Eukaryotic Cells-
*have membrane bound orgaelles
*has a nucleus
*DNA is long and linear
*80s ribosomes
*large
*capsule and plasmid never present

Prokaryotic Cells-
*no membrane bound organelles
*no nucleus
*DNA is short and circular
*70s ribosomes
*smaller
*plasmid, flagella and capsule sometimes present

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11
Q

describe why viruses are described as a cellular and non-living

A

They are not made of cells and cell membranes and they are classed as non living as they cannot independently move

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12
Q

describe the general structure of a virus particle

A

Has nucleic acid which is surrounded by a capsid with attachment protein on the surface allowing attachment to specific host cells. some are surrounded by lipid envelopes

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13
Q

describe the difference between magnification and reslolution

A

magnification is the number of times greater image is than the real size whereas the resolution is the minimum distance apart 2 objects can be to be dististinguised as separate

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14
Q

describe the function of a optical microscope

A

-light is focused using glass lenses
-light passes through specimen
-2D image is generated of a cross section
-low resolution due to long wavelength
-low magnification
-can show colour

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15
Q

describe the function of transmission electron microscope

A

-electrons focused using electromagnets
-generated a 2D image of a cross section
-very high resolution due to short wavelength
-high magnification
-does not show colour

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16
Q

describe the function of scanning electronic microscope

A

-electrons focused using electromagnets
-generates a 3D image of surface
-high resolution due to short wavelength
-high magnification
-does not show colour

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17
Q

describe how the size of an object viewed with an optical microscope can be measured

A

1, line up eyepiece with stage micrometer
2, calibrate eyepiece graticule
3,take micrometer away and measure how many dividisions make up the object
4,calculate the size of the object by multiplying number of divisions by size of division
5, recalibrate eyepiece at different magnification

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18
Q

describe the principles of cell fractionation and ultracentrifugation

A

1.homogenised tissue
2.place is cold, isotonic, buffered solution
3.filter supernatant
4.ultracentrifugation

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19
Q

What is an antigen?

A

A protein that triggers an immune response

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20
Q

how are cells identified by the immune system?

A

each cell has specific molecules on its cell surface membrane that identify them

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21
Q

describe phagocytosis.

A

1- pathogen is recognised as having non-self antigens and attaches to the phagocyte by surface receptors
2- pathogen is engulfed by phagocyte by endocytosis forming a phagosome
3- lysosome fuse forming phagolysosome releasing digestive enzymes
4- harmless products are excreted or are used by the phagocyte

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22
Q

describe the response of T lymphocytes to a foreign (cellular responce)

A

t lymphocytes recognise antigens on cell surface membrane of antigen presenting cells, due to complimentary receptors on cell surface that bind to antigen on antigen presenting cell.

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23
Q

describe the response of B lymphocytes to a foreign antigen. (humoral responce)

A

b lymphocytes can recognise free antigens.
1-clonal selection = specific b lymphocyte with complimentary receptors on antibody cell surface binds to antigen then is stimulated by T Helper cells which release cytokines then divide to form differentiate into B plasma and memory

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24
Q

what are antibodies?

A

quaternary proteins secreted by B lymphocytes that specifically bind to antigens

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25
explain how antibodies lead to the destruction of pathogens?
antibodies bind to antigens on pathogens forming an antigen antibody complex (have a specific tertiary structure),binds to two pathogens at time causing agglutination. antibodies attract phagocytes
26
what is a primary responce?
First exposure to antigen and antibodies are produced slowly, and b plasma cells are slowly stimulated to produce specific antibodies. memory cells are produced.
27
what is the secondary immune responce?
second exposure and antibodies are produced fasted and b memory cells rapidly undergo mitosis to produce plasma cells which produce specific antibodies
28
what is a vaccine?
injection of antigens from dead or weakened pathogens
29
explain how vaccines provide protection against disease?
specific b lymphocytes with complimentary receptors bind to antigen and specific t Helper cells bind to APC stimulating b cells. the b lymphocytes divide forming clones some differentiate into b plasma and memory.
30
explain how vaccines provides protection for populations against disease
herd immunity- large proportion is vaccinated which reduces the spread of pathogen so fewer are infected and pass it on
31
what’s active immunity?
the body makes antibodies after being exposed natural-immune after catching artificial-immune after vaccine
32
what is passive immunity
body is given the antibodies natural-breast milk artifical-injected with antibodies
33
explain the effects of antigen variability on disease and diseas prevention
antigens on pathogens change tertiary structure due to gene mutation so no longer immune and b memory cells can no longer bind and recognise antigen on second exposure and specific antibodies are not complimentary.
34
describe the replication of HIV in T helped cells
HIV attachedment proteins attach to receptors on Helper t cells and the lipid envelope fuses with the cell surface membrane releasing capsid info cell this releases HIV RNA and reverse transcriptase. viral DNA is inserted to Helper t cell DNA and viral enzymes are produced. virus particles assemble and released from cell via budding
35
explain how HIV causes the symptoms of AIDS
HIV infects and kills t helper cells as it multiplies rapidly so they can no longer stimulate cytotoxic t cells, b cells and phagocytes, so antibodies can not be released so there’s little angglutination and destruction of pathogens so they reproduce releasing toxins and damage cells
36
what is a monoclonal antibody
is an antibody produced from genetically identical clonned b lymphocytes and plasma cells so they have the same tertiary structure
37
Explain the role of antigen presenting cells (APC)
Macrophages present antigen from pathogen on its surface, which enhances the recognition by T-helper cells which cannot interface with pathogens
38
Explain the differences between specific and non-specific immune responce.
Non-specific (phagocytosis)- same for all pathogens specific (B&T lymphocytes)- complimentary to pathogens Non-specific- immediate responce Specific- slow responce
39
Explain the cell-mediated responce.
-Complimentary T lymphoctes bind to foreign antigen on APC -Release cytokines which stimulate: complimentary T cells wich differentiate to memory cells or triggers an immune responce/ cytotoxic T cells
40
Explain the humoral responce.
-Complimentary T lymphocytes bind to antigens on antigen presenting T cells -Which release cytokines that stimulate complmentry B lymphocytes -B cells differentiate into plasma cells -Plasma cells secrete antibodies
41
What causes antigen variability?
-Random mutation in the DNA base sequence -Resultng in different sequence of codons on mRNA -Different primary structure due to change in hydrogen bonds, ionic bonds, and disulfide bridges forming in different places in tertiary structure -Results in a different shape of antigen (memory cells ae no longer complimentary, so individuals can catch a disease more than once)
42
What is herd immunity?
Vaccinating a large proportion of the population, which reduces the avalibitlity or pathogens to be carried- protects those who havent been vaccinated
43
Suggest some ethical issues regarding vaccinations
-could have potentially dangerous side effects - clinical tests could be fatal
44
Describe the structure of HIV
genetic material, viral enzymes surrounded by capsid. Which is surrounded by a viral envelope
45
How does HIV result in AIDS?
Attachement proteins bind to complimentary receptors on T cells, HIV cells replicate inside the T cells which kills or damages them. AIDS develops when the T cells reach a critical level.An indivduals immne system is weakend and so cannot fight off any diseases.
46
Why are antibiotics inafectve against viruses?
Antibiotics work by damaging the murin cell walls, viruses have no cell walls. Viruses replicate inside host cell- difficult to desroy them without damaging body cells
47
describe the stages of the cell cycle in Eukaryotic cells
interphase- s phase, DNA is replicated semi-conservatally leading to 2 chromatids joined at a centromere g1/g2, number of organelles increase and vol of cytoplasm increases mitosis- nucleus divides to produce 2 nuclei with identical copies of DNA produced by a parent cell cytokinesis- cytoplasm and cell membrane divides to form 2 genetically identical daughter cells
48
describe the behaviour of chromosomes and spindel fibres during prophase
chromosomes condense becoming shorter and thicker becoming visible (sister chromatids joined by a centromere). the nuclear envelope breaks down and the centrioles move too opposite poles forming spindel network
49
describe the behaviour of chromosomes and the role of spindel fibres in metaphase
spindel fibres attach to chromosomes by their centromeres and the chromosomes align along the metaphase plate
50
describe the behaviour of chromosomes and role of spindel fibres in anaphase
the spindel fibres contract and the sentromere divides pulling chromosomes to opposite poles of the cell
51
describe the behaviour of chromosomes and the role of spindel fibres in telophase
chromosomes uncoil becoming longer and thinner, the nuclear envelope starts to reform and the centroles break down
52
why do some eukaryotic Cells not undergo the cell cycle?
not all cells retain the ability to divide
53
explain the importance of mitosis in the life of an organism
-growth of multicellular organisms by increasing cell number -replacing cells to repair damaged cells -asexual reproduction
54
describe how tumours and cancers form
-mutations in DNA / genes controlling mitosis can lead to uncontrolled cell devision -tumours form in result of mass of abnormal cells
55
suggest how cancer treatments controlled the rate of division
-some disrupt dpindel fibre activity so chromosomes can’t attach to spindle by their centromere slowing mitosis -DNA replication is prevented during interphase so cannot make 2 copies of each chromosome slowing mitosis
56
describe how Prokaryotic cells replicate
Binary Fission: 1,replication of circular DNA 2,Replication of plasmid 3,divisolion of cytoplasm to produce 2 daughter cells
57
Describe how viruses replicate
attachment proteins attach to complimentary receptors on host cell and inject viral nucleic acid (DNA/RNA) and infected host cell replicates
58
What is the deffinition of simple diffusion?
The net movement of molecules from an area of higher concentration to an area of lower concentration until equilbrium is reached, without requiring ATP
59
Define Faccilitated diffusion?
The passive process but differs from simple diffusion as proteins are used to transport molecules, from a higher concentration to a lower concentration
60
Define osmosis
The movement of water from an area of higher water potential to an area of lower water potential across a partially perimiable membrane.
61
What does Isotonic mean?
When the water potential is the same in the soloution and the cell within the solution
62
What does Hypotonic mean?
when the water potential of a solution is more positive than the cell
63
What does hyertonic mean?
when the water potential of a slolution is more negative than the cell
64
What is active transport?
The movement of molecules and ions from an area of lower concentation to an area of higher concentration, against the concentration gradient, using ATP and carrier proteins which act as a pump to move substances across the membrane
65
Describe the principles of an optical microscope.
-light focused using glass lenses -light passes through specimen- different structures absorb different amounts & wavelengths -Generates a 2D image of a cross section -low resolution -cannot see internal structures -low magnification
66
Describe the principles of a transmission electron microscope.
-electron focused using electromagnets -electrons pass through specimens -generates a 2D image of a cross-section -very high resolution -high magnification -can see internal structures -specimen must be very thin
67
Describe the principles of the scanning electron microscope
-electron focused using electromagnets -electrons are deflected off the specimens surface -generates a 3D image -high resolution -high magnification -cannot see internal structures -can only veiw dead or dehydrated specimens as a vacuum is used
68
Describe how the size of an object viewed with an optical microscope can be measured
1. Line up (scale of) eyepiece graticule with (scale of) stage micrometre 2. Calibrate eyepiece graticule - use stage micrometre to calculate size of divisions on eyepiece graticule 3. Take micrometre away and use graticule to measure how many divisions make up the object 4. Calculate size of object by multiplying number of divisions by size of division 5. Recalibrate eyepiece graticule at different magnifications
69
Describe how prokaryotic cells replicate
1. Replication of circular DNA 2. Replication of plasmids 3. Division of cytoplasm to produce 2 daughter cells ● Single copy of circular DNA ● Variable number of copies of plasmids
70
Describe how viruses replicate
1. Attachment proteins attach to complementary receptors on host cell 2. Inject viral nucleic acid (DNA/RNA) into host cell 3. Infected host cell replicates virus particles: a. Nucleic acid replicated b. Cell produces viral protein / capsid / enzymes c. Virus assembled then released
71
Describe the fluid-mosaic model of membrane structure
● Molecules free to move laterally in phospholipid bilayer ● Many components - phospholipids, proteins, glycoproteins and glycolipids
72
Describe the arrangement of the components of a cell membrane
● Phospholipids form a bilayer - fatty acid tails face inwards, phosphate heads face outwards ● Proteins ○ Intrinsic / integral proteins span bilayer eg. channel and carrier proteins ○ Extrinsic / peripheral proteins on surface of membrane ● Glycolipids (lipids with polysaccharide chains attached) found on exterior surface ● Glycoproteins (proteins with polysaccharide chains attached) found on exterior surface ● Cholesterol (sometimes present) bonds to phospholipid hydrophobic fatty acid tails
73
Explain the role of cholesterol (sometimes present) in cell membranes
● Restricts movement of other molecules making up membrane ● So decreases fluidity (and permeability) / increases rigidity

Biology (8 decks)

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