Cells Flashcards
(93 cards)
1
Q
structure of cell surface membrane
A
found in all cell
made up of a phospholipid bilayer
has embedded molecules and molecule attached on the outside - proteins, carbohydrates, cholesterol
2
Q
function of cell surface membrane
A
controls the entrance and exit of molecules
3
Q
structure of nucleus
A
surrounded by a nuclear envelope which is a double membrane
it has nuclear pores
filled with the nucleoplasm which is a granular, jelly-like substance
contains chromosomes - protein-pound linear DNA
has a nucleolus - smaller sphere in the nucleoplasm which is the site of rRNA production and ribosome synthesis
4
Q
function of nucleus
A
site of DNA replication and transcription
contains the genetic code for each cell
5
Q
structure of the mitochondria
A
has a double membrane
the inner membrane folds into extensions called cristae
the fluid centre is called the matrix
it contains 70s ribosomes and circular DNA
6
Q
function of the mitochondria
A
site of stages of aerobic respiration and ATP production
7
Q
structure of chloroplast
A
has a double membrane
contains thylakoids - folded membranes embedded with pigment
fluid filled storm contains enzymes for photosynthesis
found in plants
contains 70s ribosomes and circular DNA
8
Q
function of chloroplast
A
site of photosynthesis
9
Q
structure of Golgi apparatus
A
folded membranes which form cisternae
secretory vesicles pinch off from the cisternae
10
Q
function of the Golgi apparatus
A
add carbohydrates to proteins to form glycoproteins
produce secretory enzymes
secretes carbohydrates
transports, modifies, and stores lipids
forms lysosomes
molecules can be ‘labelled’ to reach their destination
finished products are transported to the cell surface in Golgi vesicles where they fuse with the membrane and the contents are released by exocytosis
11
Q
structure of lysosomes
A
bags of digestive enzymes
12
Q
function of lysosomes
A
hydrolyse pathogens in phagosomes
completely break down dead cells (autolysis)
exocytosis - release enzymes outside the cell to destroy material
digest worn out organelles for the reuse of materials
13
Q
structure of ribosomes
A
small granules made up of two sub units of protein and rRNA
80s - large ribosomes in eukaryotic cells
70s - smaller ribosomes found in prokaryotic cells, mitochondria, and chloroplasts
14
Q
function of ribosomes
A
site of protein synthesis
15
Q
structure of the RER
A
has folded membranes called cisternae
has ribosomes on the cisternae
16
Q
function of RER
A
protein synthesis
17
Q
structure of SER
A
has folded membranes called cisternae
18
Q
function of SER
A
synthesises and stores lipids and carbohydrates
19
Q
structure of cell wall
A
in plants an fungal cells
in plants it is made of microfibrils of cellulose
in fungi it is made of chitin - a nitrogen containing polysaccharide
20
Q
function of cell wall
A
provides structural strength to the cell
21
Q
structure of vacuole
A
filled with fluid surrounded by a single membrane called a tonoplast
22
Q
function of vacuole
A
makes cells turgid - provides support
temporary store of sugars and amino acids
the pigments are responsible for coloured petals which can attract pollinators
23
Q
key differences between prokaryotic and eukaryotic cells
A
p are smaller
p doesn’t have membrane bound organelles
p has smaller ribosomes
p has no nucleus
p has a cell wall made of murein
p has circular naked DNA, e has linear DNA associated with histones
24
Q
plasmids
A
ring od DNA containing genes linked to survival e.g. antibiotic resistance
found in bacteria
25
capsule
bacteria
surrounds the cell wall and provides protection from other cells and helps bacteria agglutinate (stick together)
26
flagella
tail structure used for locomotion
27
structure of a virus
non-living and acellular
smaller than bacteria
contain genetic material, a capsid, and attachment proteins
28
how is HIV structure different from the generic virus structure
has a further lipid envelope which has attachment proteins on the outside
this means the virus can identify which host cells to enter
29
magnification
how many times larger the image is compared to the actual object
30
resolution
the minimum distance between two objects in which they can still be viewed as separate
31
key features of an optical microscope
beam of light condensed to create the image
glass lens used to condense the light
poorer resolution due to light having a longer wavelength
lower magnification
can produce coloured images
can view living samples
32
key features of an electron microscope
beam of electrons condensed to create the image
electromagnets used to condense the beam
higher resolving power as electrons have shorter wavelength
higher magnification
black and white images
samples must be in a vacuum so non-living
33
how do transmission electron microscopes work
extremely thin specimen stained and placed in vacuum
electron gun produces beam that passes through the specimen
some parts absorb and appear dark
image is 2D and detailed
34
how do scanning electron microscopes work
specimen does not need to be thin as electrons are not transmitted through
electrons are beamed onto the surface and are scattered in different ways depending on the contours
this produces a 3D image
35
calculation for magnification
image = actual x magnification
36
how is an eyepiece graticule used
can be calibrated using a stage micrometer
line up the stage micrometer and the eyepiece graticule whilst looking through the eyepiece
count how many divisions on the eyepiece graticule fir into one division on the micrometer scale
one the graticule is calibrates, you can measure the size of cells or organelles
37
cell fractionation
cells broken downing a homogeniser
the solution must be:cold - reduces enzyme activity to prevent the hydrolysis of organellesisotonic - prevents any movement of water by osmosis which could cause organelles to swell/shrivelbuffered. -resistant to pH changes to prevent damage to organelles and enzymesafter it is homogenised, the solution is filtered to remove large debris
38
ultracentrifugation
solution placed into centrifuge and spun at high speed to separate organelles by their density
the first pellet at a low speed will contain the nuclei
spin supernatant fluid
this pellet will contain mitochondria and chloroplasts
spin supernatant fluid again
the pellet will contain lysosomes and SER/RER
spin again
pellet contains ribosomes
39
binary fission
circular DNA and plasmids are replicated
more organelles
cytoplasm splits to create two daughter cells
each has one copy of the circular DNA but a variable number of plasmid copies
40
stages of the cell cycle
interphase (G1, S, G2) - longest stage, organelles duplicate, cell grows, DNA replicates
nuclear division - either by mitosis (creating two identical diploid cells) or meiosis (contains four genetically different haploid cells)
cytokinesis - division of the cytoplasm to create new daughter cells
41
what is mitosis for
growth and repair
e.g. clonal expansion of B cells in humeral response
42
mitosis
prophasechromosomes condense and become visible nuclear envelope disintegrates centrioles separate and move to opposite poles of the cellmetaphasechromosomes align along the equator of the cellspindle fibres are released from the poles and attach to the centromeres of the chromatidsanaphasespindle fibres retract and pull the centromere, separating the chromatids to each pole of the cellseparated chromatids now referred to as chromosomes this stage requires energy in the form of ATPtelophasechromosomes at each pole become longer and thinnerspindle fibres disintegrate and nucleus reforms
43
mitotic index equation
number of cells in mitosis/total number of cells x 100
44
why is the cell surface membrane model described as the fluid-mosaic model
mosaic mixture of molecules - phospholipids, proteins, glycoproteins, glycolipidsfluidnature of the bilayer means it can move
45
how do phospholipids align as a bilayer
due to hydrophilic heads being attracted to water and hydrophobic tails repelled by water
creates a selectively permeable membrane
46
function of cholesterol in phospholipid bilayer
restricts the lateral movement of other molecules in the membrane
means the membrane are less fluid at high temperatures
prevents water and dissolved ions from leaking out the cell
47
peripheral proteins in the phospholipid bilayer
don't extend completely across the membrane
provide mechanical support
glycoproteins/glycolipids can function as cell receptors for recognition
48
integral proteins in the phospholipid bilayer
span across from one side of the bilayer to the other
carrier proteins - bind to large molecules like glucose/amino acids and change shape to transport them to the inside of the cell/organelle
channel proteins - fill with water and enable water soluble ions to diffuse
49
which molecules can pass through the plasma membrane
lipids soluble substances like some hormones
very small molecules like CO2, H2O, or O2
50
which molecules can't pass through the plasma membrane
water-soluble (polar) substances like sodium ions
large molecules like glucose
51
diffusion
net movement of molecules from an area of higher conc to an area of lower conc until equilibrium is reached
it is a passive process
movement of molecules is due to kinetic energy
for molecules to diffuse across the membrane they must be small and non-polar/lipid soluble
52
facilitated diffusion
passive process like diffusion
involves the net movement of molecules from an area of high conc to low conc
membrane proteins are used to transport molecules
ions and polar molecules can be transported across membranes by facilitated diffusion using protein channels and carrier proteins
53
how do channel proteins carrier out facilitated diffusion
they are water filled tubes which allow water soluble ions to pass through
still selective as channel proteins only open in the presence of certain ions when they bind to the protein
54
how do carrier proteins carrier out facilitated diffusion
bind to a molecule
changes the shape of the protein
this enable the molecule to be released on the other side
protein reverts back to its original shape
55
osmosis
the net movement of water from an area of higher water potential to an area of lower water potential across a selectively permeable membrane
56
what is water potential
the pressure created by water molecules
it is measured in kPA
pure water has a water potential of zero
when solutes are dissolved, the water potential becomes more negative
57
isotonic solution
water potential of the solution is the same as the water potential of the cell
58
hypotonic solution
water potential of the solution is more positive than the cell
in animal cells, water will move into the cell and it will burst (lyse)
plant cells don't burst and instead become turgid
59
hypertonic solution
water potential of the solution is more negative than the cell
both animal and plant cells will lose water and shrivel
60
active transport
movement of molecules/ions from an area of lower conc to higher conc against a concentration gradient
uses ATP and carrier proteins
61
how do carrier proteins carry out active transport
molecules bind to receptor sites on the carrier protein
ATP binds to the protein on the inside of the membrane and it is hydrolysed into ADP and Pi
this causes the protein to change shape and open towards the inside of the membrane
this causes the molecule to be released on the other side of the membrane
the Pi molecule is then released from the protein, resulting in the protein reverting back to its original shape
62
how is active transport selective
only certain molecules can bind to the carrier proteins to be pumped
63
co transport of glucose/amino acids
sodium ions are actively transported out of the epithelial cell into the blood in the capillary
this reduces the sodium ion concentration of the epithelial cell
sodium ions can then diffuse in from the lumen down the conc gradient into the epithelial cell
the protein the odium ions diffuse through is a co-transport protein so glucose/amino acids also attach and are transported into the epithelial cell against their conc gradient
glucose then moves by facilitated diffusion from the epithelial cell to the blood stream
64
how are lymphocytes prevented from attacking body cells
they are made when you are a foetus and unlikely to be exposed to any other cells other than self cells
lymphocytes complementary to the antigens on self cells will die or their production will be suppressed
the only remaining lymphocytes are complementary to pathogenic and non-self cells
65
antigens
foreign proteins that generate an immune response by lymphocytes when detected in the body
they are located on the surface of cells
66
antigenic variability
pathogenic DNA can mutate frequently, if this occurs on a gene that codes for the antigen, then the shape of the antigen can change
any previous immunity is no longer effective as memory cells will have memory of the old antigen shape
67
non specific vs specific response
non specific - phagocytes - any non-self cell will trigger the same response
specific - lymphocytes - have specialised responses
68
phagocytosis
phagocytes are in the blood and tissues - any chemicals/debris released by pathogens or abnormal cells attract the phagocytes to move towards these cells
there are many receptor binding points on the surface of phagocytes - these attach to chemicals or antigens on the pathogen
the phagocyte changes shape to move around and engulf the pathogen
once engulfed, the pathogen is contained within a phagosome vesicle
a lysosome within the phagocyte fuses with the phagosome and releases its contents
lysozymes released from the lysosome hydrolyse the pathogen
this destroys the pathogen
the soluble products are absorbed and used by the phagocyte
the phagocyte can then present the pathogen antigens on its cell surface membrane
69
where are T cells locates
made in the bone marrow but mature in the thymus
70
where are B cells found
made and mature in the bone marrow
71
antigen presenting cells
infected body cells presenting viral antigens on their surface
a macrophage which has engulfed and destroyed a pathogen presenting the antigens on their surface
cells of a transplanted organ which has different shaped antigens on its surface compared to self antigens
cancer cells have abnormal shaped self-antigens
72
why is cell-mediated response described as cell-mediated
because T cells only respond to antigens which are presented on cells and not antigens detached from cells and within bodily fluids like the blood
73
cell mediated response
a pathogen is engulfed and destroyed by a phagocyte and the antigens are positioned on the cell surface (it is an antigen presenting cell)
helper T cells have receptors on their surface which can attach to the antigens on the APC
this activates the helper T cell to divide by mitosis to replicate and make large number of clones
cloned helper T cells differentiate into different cells helper T cells that activate B lymphocytes stimulate macrophages to phagocytosismemory cells complementary to that antigencytotoxic T cells
74
cytotoxic T cells
they destroy abnormal/infected cells by releasing a protein called perforin which embeds in the cell surface membrane and makes a pore so substances leave/enter the cell, resulting in cell death
75
why is humoral response named humoral
the response involves B cells and antibodies which are soluble and transported in bodily fluids
76
humoral response
antigens in the blood collide with their complementary antibody on a B cell
the B cell takes in the antigen by endocytosis and then presents it on its cell surface membrane
when this collides with a helper T cell receptor, this activates the B cell to go through clonal expansion and differentiation (clonal selection) via mitosis
these result in plasma cells or memory B cells
plasma cells make antibodies whereas memory B cells divide rapidly into plasma cells when reinfected with the same pathogen
77
structure of an antibody
quaternary proteins made up of four polypeptide chains
Y shaped
each antibody has a different shaped bonding site (on the end of each branch) which is the variable region
it also has a light chain (the branches of the Y)
and a heavy chain (the base stalk of the Y)
78
agglutination
antibodies are flexible and can bind to multiple antigens to clump them together
the makes it easier for phagocytes to locate and destroy pathogens
79
passive immunity
antibodies are introduced into the body
the pathogen doesn't enter the body so plasma cells and memory cells are not made
no long-term immunity
e.g. antibodies passed to a foetus through the placenta or through breast milk to a baby
80
active immunity
when the immunity is created by your own immune system following exposure to the pathogen or its antigen
81
natural active immunity
following infection and the creation of the body's own antibodies and memory cells
82
artificial active immunity
following the introduction of a weakened form of the pathogen/antigens via a vaccine
83
how does a vaccine work
small amounts of weakened/dead pathogen/antigen are introduced to the body
exposure to the antigen stimulates B cells to go through clonal expansion and clonal selection
B cells undergo mitosis to make large amounts of cells which differentiate into plasma cells and memory cells
plasma cells make antibodies
memory cells divide rapidly into plasma cells when reinfected with the same pathogen to make large numbers of antibodies rapidly
84
herd immunity
if enough of the population is vaccinated, the pathogen cannot spread easily
this provides protection for those who are no vaccinated
85
monoclonal antibodies
single type of antibody that can be isolated and cloned
they can be used for medical treatment, medical diagnosis, or pregnancy tests
86
direct monoclonal antibody therapy
monoclonal antibodies are designed with a binding site complementary in shape to the antigens on the outside of cancer cells
the antibodies are given to the patient and attach to the cancer cell antigens
this prevents chemicals from binding to the cancer cells which enables uncontrolled cell division
the monoclonal antibodies prevent the cancer cells from growing and do not cause harm to normal cells
87
indirect monoclonal antibody therapy
monoclonal antibodies are designed complementary in shape to the antigens on the outside of cancer cells, and have drugs attached
these cancer drugs are delivered directly to the cancer cells and kills them
this reduces the harmful side effects that traditional chemotherapy and radiotherapy can produce
88
how does a pregnancy test work
first mobile antibody is complementary to the antigen being tested for and has a coloured dye attached
a second antibody, complementary in shape to the antigen is immobilised in the test - this gives the second line that only appears if the antigen being tested for is present
a third antibody is immobilised and is complementary in shape to the first antibody - this gives the control line
89
ELISA test
enzyme linked immunosorbent assay
test sample is added to a dish and washed to remove any unbound test sample
an antibody complementary in shape to the antigen you're testing for is added
wash to removed unbound antibody
a second antibody complementary in shape to the first antibody is added (it has an enzyme attached to it)
it is again washed to remove any unbound second antibody
the substrate for the enzyme is added - the substrate produces coloured products in the presence of the enzyme
the presence of colour indicates the presence of the antigen in the test sample - colour intensity indicates quantity present
90
ethical issues with monoclonal antibodies
requires mice to produce the antibodies and tumour cells
91
why is it difficult to get rid of viruses
they replicate inside of cells, making it difficult to destroy them without harming the host cell
they have different replication mechanisms and no cell wall and therefore aren't destroyed by antibiotics
92
HIV replication
HIV attaches to a CD4 protein on helper T cells
the HIV protein capsule fuses with the helper T cell membrane, enabling RNA and enzymes from the HIV to enter
reverse transcriptase copies the viral RNA into a DNA copy and moves to the helper T cell nucleus
mRNA is transcribes and the helper T cell creates viral proteins to make new viral particles
93
symptoms of AIDS
AIDS is when the replicating viruses in the helper T cells interfere with the normal functioning of the immune system
the host cannot produce an adequate immune response to other pathogens
