Topic 2 Flashcards
name the organelles of eukaryotic cells
cell surface membrane
cell wall
lysosomes
nucleus
Golgi apparatus
rough endoplasmic reticulum
smooth endoplasmic reticulum
mitochondria
chloroplasts
ribosomes
vacuole
structure of nucleus
nuclear envelope > double membrane
nuclear pores
nucleoplasm > granular, jelly like material
chromosomes > protein-bound linear DNA
nucleolus > smaller sphere
what is the function of nucleus
- site of DNA replication and transcription (making mRNA)
- contains genetic code for each cell
structure of smooth endoplasmic reticulum
folded membranes called cisternae
function of smooth endoplasmic reticulum
synthesis and stores lipids and carbs
what are the membranes of the endoplasmic reticulums called
cisternae
structure of rough endoplasmic reticulum
folded membranes called cisternae with ribosomes on the cisternae
function of rough endoplasmic reticulum
protein synthesis
structure of Golgi apparatus and vesicles
- folded membranes called cisternae
- vesicles bud off from cisternae
function of Golgi apparatus and vesicles
- add carbs to proteins to form glycoproteins
- form lysosomes
- secret carbs
- produce secretory enzymes
- transport, modify and store lipids
- molecules are ‘labelled’ with their destination
structure of lysosomes
bag of digestive enzymes (up to 50 different enzymes)
function of lysosomes
- hydrolyse phagocytic cells
- autolysis (breaking diwn cells)
- exocytosis (release enzymes to outside of cell to destroy material)
- digest worn out organelles
structure of mitochondria
double membrane
inner membrane > cristae
mitochondrial matrix > fluid centre
loop of mitochondria DNA
function of mitochondria
site of aerobic respiration
site of ATP production
DNA > to enable coding for enzymes needed during respiration
structure of ribosomes
made of protein and rRNA
eukaryotes > 80s
prokaryotes, mitochondria and chloroplasts > 70s
function of ribosomes
protein synthesis
structure of vacuole
filled with fluid surrounded by single tonoplast membrane
function of vacuole
makes cell turgid
temporary store of sugars and amino acids
pigments colour petals > attracting pollinators
structure of chloroplasts
double membrane
thylakoids > folded membranes embedded with pigment
fluid filled stroma contains enzymes for photosynthesis
function of chloroplasts
site of photosynthesis
thylakoids > light dependant reactions
structure of cell wall in plants
made of microfibrils of cellulose
structure of cell wall in fungi
made of chitin
function of cell wall
provides structural strength to the cell
structure of plasma membrane
found in all cells
phospholipid bilayer > molecules embedded within and attached on the outside
(proteins, carbs and cholestrol)
function of plasma membrane
controls entrance and exit of molecules
outline key differences between eukaryotes and prokaryotes
- prokaryotes are smaller
- prokaryotes have no membrane bound organelles
- prokaryotes have no nucleus
- prokaryotes have smaller ribosomes
- prokaryotes cell wall made of murein
structure of viruses
genetic material, capsid and attachment proteins
function of viruses
replicate inside of host cells making it difficult to destroy them harming host cells
why are viruses considered non-living
- they cant replicate independantly > require a host cell because they dont have their own organelles
- do not produce their own energy > no mitochondria
why are viruses considered acellular
they lack membrane bound organelles and a cytoplasm
what are the three methods of studying cells
microscopy
cell fractionation
ultracentrifugation
what are three types of microscopes
optical light ms
transmission electron ms
scanning electron ms
define magnification
refers to how many times larger the image is compared to the object
define resolution
the minimum distance between two objects making them seen as seperate
how do optical light microscopes work
a beam of light is condensed to create the image
why does optical light microscopes have a poorer resolution
light wavelength is longer
how do electron microscopes work
beam of electrons is condensed to create the image
- electromagnets used to condense the beam
compare magnification of optical and electron microscopes
optical has a lower magnification than electron
compare resolution of optical and electron microscopes
optical has lower resolution than electron because light has a longer wavelength than electrons
compare colour of images between optical and electron microscopes
optical produces colour images whereas electron produces black and white images
compare the conditions of the specimen used between optical and electron microscopes
optical microscopes allow for living specimen to be used but with electron sample must be in a vacuum and non-living
summarise advantages and disadvantages of optical light microscopes
+ colour images
+ live specimen sample
- poorer resolution
- poorer magnification
summarise advantages and disadvantages of electron microscopes
+ higher resolution
+ higher magnification
- specimen must be dead
- black and white images
what is the impact of using optical light microscopes and therefore having a poorer resolution
smaller organelles arent visible
explain how transmission electron microscopes work
- thin specimen prepped in vacuum is stained
- electron gun produces beam of electrons which pass through specimen
- some parts of specimen absorb electrons
- darker areas on image show electron absorption
explain how scanning electron microscopes work
electrons beamed onto the surface of specimen and then are scattered in diff ways depending on the contours > producing 3D images
what is cell fractionation
isolating of organelles so that they can be studied
what are the two steps of cell fractionation
- homogenisation
- ultracentrifugation
describe homogenisation
cell is broken down and blended in a cold isotonic buffer solution
why is the solution filtered after homogenising
to remove large debris
describe ultracentrifugation
the filtered solution is placed in a centrifuge and spun at different speeds
- organelles form pellets at the bottom of test tube depending on its density
why is the cell blended in a cold solution
to prevent enzyme activity and prevent damage to the organelles
why is the cell blended in an isotonic solution
to prevent osmosis > could burst/shrivel the organelles
why is the soltuion that the cell is blended in buffered
to prevent damage to organelles > could be too acidic / alkaline
what is differential centrifugation
centrifuge spins and centrifugal forces causes pellets of the most dense organelles to form at the bottom
- speed of centrifuge increases each time
- supernatant is removed and spun again
what is the order of differential centrifugation of the organelles
nuclei
chloroplast s(plants only)
mitochondria
lysosomes
endoplasmic reticulums
ribosomes
compare cell division between eukaryotes and prokaryotes
eukaryotes > mitosis or meiosis
prokaryotes > binary fission
why do viruses not undergo cell division
they are non-living
how do viruses replicate
by injecting their nucleic acid into a host cell and invading them
what are the three key stages of the cell cycle
Interphase (G1, S, G2)
Nuclear division > mitosis / meiosis
Cytokinesis
what is the longest stage of the cell cycle
Interphase
what happens in interphase
organelles double, cell grows and DNA replicates
what are the two types of nuclear division
mitosis and meiosis
what does mitosis create
two identical diploid cells
what does meiosis create
four genetically different haploid cells
what is cytokinesis
division of the cytoplasm to create new cells
what is G1
growth stage
what is S phase
DNA synthesis
what is G2
growth and preparation for nuclear division
what are the 4 stages of mitosis
prophase
metaphase
anaphase
telophase
how many rounds of division are there for mitosis
one
describe prophase
- chromosomes condense and become visible
- nucleolus disappears
(animal cells) - centrioles separate to opposite poles of the cell
what do centrioles do
create spindle fibres which attach to the chromatids to pull them to opposing poles of the cell
describe metaphase
- chromosomes align at equator
- spindle fibres released from poles and attach at the centromere to the chromatid
where do the spindle fibres attach on the chromosomes
at the centromere
describe anaphase
- spindle fibres retract and pull centromere and chromatids to opposing poles
- causing centromere to divide into two and pull the individual chromatids away
where is the energy needed for anaphase produced from
mitochondria
describe telophase
- chromosomes at each pole become long and thin again
- spindle fibres disintegrate and nucleus reforms
- cytokinesis occurs > two genetically identical cells are formed
how do you calculate mitotic index
(number of cells in mitosis / total number of cells) x 100
what cell division occurs in prokaryotic cells
binary fission
what model describes the structure of all membranes
fluid mosaic model > mixture and movement of phospholipids, glycoproteins, proteins and glycolipids
why do the phospholipids align as a bilayer
hydrophilic heads and hydrophobic tails
why are the phospholipid heads hydrophilic
the negative charge on the phosphate group is attracted to water
why are phospholipid tails hydrophobic
because they repel water
what is the impact of the prescense of cholesterol
restricts lateral movement of other molecules > prevents fluidity of the membrane at high temperatures
why is the reduced fluidity of the membrane due to the presence of cholesterol an advantage
prevents water and dissolved ions from leaking out of the cell
what is osmosis
movement of water from an area of higher water potential to an area of lower water potential across a partially permeable membrane
what is water potential
the pressure created by water molecules and is measured in kPa
what is the water potential of pure water
0
what happens to the water potential of water when solutes are dissolved in it
becomes negative
what is an isotonic solution
water potential is the same in the solution and the cell within the solution
what does hypotonic mean
water potential of solution is more postive (closer to 0) than the cell
what does hypertonic mean
when water potential of a solution is more negative than the cell
whats active transport
movement of substance from a low conc area to high conc area using metabolic energy via carrier proteins
explain active transport
- molecule binds to complementary receptor cells onto the carrier protein
- ATP binds to carrier protein from inside of the cell an =d its hydrolysed into ADP+Pi
- this causes carrier protein to change shape and release molecule to the other side
- phosphate ion is released and protein returns to og shape
what type of transport is co transport
active
outline the steps of co-transport of glucose and sodium ions in the ileum
- sodium ions are actively transported out of the epithelial cell into the blood
- this reduces the sodium ion concentration in the epithelial cell
- sodium ions can then diffuse down their conc gradient from the ileum into the epithelial cell via a co transporter protein
- glucose / amino acids co transport against their conc gradient from the ileum into the epithelial cell with the sodium ion
- the glucose/amino acid can then move from the epithelial cell into the blood capillary via facilitated diffusion
how can cells be adapted for rapid transport
- increased surface area > e.g. microvilli
- increased number of protein channels and carriers in their membranes
what are lymphocytes
the cells that can identify whether a cell is a self cell or a non-self cell and then destroy it if its a non-self cell
examples of non-self cells
pathogens
cells from other organisms
toxins
abnormal body cells
whats an antigen
molecules (usually proteins) that trigger an immune response
what is antigen variability
- DNA of pathogens can mutate frequently meaning a mutation in the gene which codes for the antigen will result in a different shaped antigen
what is the impact of antigen variability to the human body
any previous immunity against the pathogen is no longer effective since the shape of the antigen has changed so any of the memory cells in the body will not be able to bind to the new shape
why does a new influenza virus vaccine have to be created every year
because the virus mutates and changes its antigens very quickly
what is the bodys first line of defence
chemical and physical barriers
e.g. skin, stomach acid, nails, mucus
what is the bodys second line of defence
white blood cells
what are the two types of white blood cells involved in immune response
phagocytes and lymphocytes
which type of WBC is responsible for a non-specific immune response
phagocyte
what type of immune response is a lymphocyte used for
specific
what is phagocytosis
the destruction of any non-self cell carried out by phagocytes
where are phagocytes found
blood and tissue
outline steps of phagocytosis
- chemicals / debris released by pathogen attracts the phagocyte to itself
- receptors on the phagocyte bind to the antigens on the pathogen
- phagocyte starts to change shape and engulfs the pathogen in a phagosome vesicle
- lysosome within phagocyte fuses with the phagosome and release its contents (enzymes)
- the lysozymes released hydrolyse the pathogen
- this destroys the pathogen and any soluble products are absorbed and used by phagocyte
where are lymphocytes made
bone marrow
where do t cells mature
thymus
what is the cell-mediated response
the response involving t cells and body cells
what are antigen presenting cells
cells which present non-self antigens on their surface
examples of APC
- infected body cells
- macrophage which has engulfed and destroyed a pathogen
- transplanted organ cells
- cancer cell
outline steps of cell mediated response
- helper t cell receptors bind to APC
- this activates the helper t cells to divide by mitosis and clone themselves
- cloned helper t cells differentiate into different cells
what do t helper cells differentiate into
- some remain as t helper cells to activate B lymphocytes
- stimulators of macrophages for phagocytosis
- memory cells for that antigen
- cytotoxic t cells > destroy abnormal / infected cells
what do cytotoxic t cells do
destroy abnormal or infected cells
how do cytotoxic t cells destroy abnormal cells
release a protein called perforin which embeds in the c.s.m and creates a pore allowing for substances to enter and leave the cell > causing cell death
what does the humoral response use
B cells and antibodies
outline the steps of the humoral response
- B cells have Ab on their c.s.m
- These Ab will bind to Ag when they collide with them
- B cell will engulf the Ag (endocytosis) and then present the Ag on its self
- t helper cells have receptors which are going to attach to the B cell and activate it to go under clonal expansion and differentiation
- B cells undergo mitosis and differentiate into memory B cells or plasma cells
- the plasma cells can then secrete Ab which can then bind to their specific Ag
can B cells produce antibodies
no, but they can differentiate into plasma cells which can
what type of immunity is the humoral response
active
compare memory B cells and plasma cells
- mBcells cant produce Ab but plasma cells can
- plasma cells are short lived whereas mBcells can live in the body for decades
what is the structure of an antibody
quaternary proteins
how many chains make an antibody
4
2 long
2 short
what is agglutination
clumping of Ab-Ag complexes
what is the advantage of agglutination
makes it easier for phagocytes to locate and destroy the pathogens
what is passive immunity
when the Ab are introduced to the body and not naturally made and so plasma cells and memory cells arent made > therefore theres no long term immunity
examples of passive immunity
Ab passed through the placenta to the fetus or through breast milk to a baby
what is active immunity
immunity created by your own natural body systems from exposure to the pathogen or its antigen
outline the differences between natural and artificial active immunity
natural > following infection
artificial > following introduction of a weakened version of pathogen or antigens via a vaccine
how do vaccines work
- small amounts of weakened or dead pathogen or antigens are introduced into the mouth or by injection
- exposure to the antigens activates the B cells to go through clonal expansion and differentiation
- B cells undergo mitosis and differentiate > plasma cells and mBcells
- plasma cells produce Ab
how does herd immunity work
if enough of the population are protected against the pathogen, it cant easily spread
what is the structure of HIV
- core > genetic RNA material + reverse transcriptase
- capid
- envelope
- protein attachments > enables attachment to the hosts helper t cells
how does HIV replicate in helper t cells
- HIV attached to CD4 protein on helper t cells
- HIV protein capsule fuses with helper t cell membrane so RNA and enzyme can enter
- HIV enzyme RT copies viral RNA into a DNA copy and then moves to the t helper cell nucleus
- mRNA is transcribed and helper t cell starts to create viral proteins to make new viral particles
difference between HIV and AIDS
HIV is when the person is infected with the virus
AIDS is when the replicating virus is interfering with the functioning of the immune system
how does AIDS interfere with the functioning of the immune system
helper t cells are destroyed so host is unable to produce an effective immune response to other pathogens > leading to infections and cancer
whats a monoclonal Ab
type of Ab which can be isolated and cloned
uses for mcAb
medical treatment
medical diagnosis
pregnancy tests
explain how direct mcAb therapy can treat some cancer
- mcAb is given to patient
- mcAb complementary to the antigens on cancer cells bind to cancer cells
- this prevents other chemicals binding to the cancer cell and prevents uncontrolled cell division
- stops the growth of the cancer cell and doesnt harm other cells
explain how indirect mcAb therapy can treat cancer
- mcAb is complementary to cancer cells antigens and the mcAb has a drug attached
- this drug will kill the cancer cells upon binding
> “bullet drugs”
what type of test do medical diagnosis use
ELISA test
what is ELISA
enzyme linked immunosorbent assay
how does ELISA test strip kit work
- a mobile Ab which is complementary to the
Ag being tested for and has pigment attached to it will drive up the test strip - if the Ag being tested for is present, the mobile Ab with the Ag binded to it, will bind to an immobilised Ab which is also complementary to the Ag being tested for > a coloured line will show up due to the pigment
- the Ab will continue travelling up the test strip and bind to another immobilised Ab which is complementary to the first Ab > a colour line will show
why is there a third Ab used in an ELISA test which is complementary to the first Ab
so we know the Ab is present and is moving up along the test strip
how does the ELISA test in a beaker work
- add patient test sample to beaker
- wash to remove unbound test sample
- add Ab which is complementary to Ag being tested for
- wash to remove unbound Ab
- add second Ab which is complementary to first Ab and has an enzyme attached
- wash again
- add colourless substrate for enzyme to beaker
> if Ag is present, coloured products formed due to enzyme-substrate complex
> intensity of colour indicates prescence of Ag
what are the ethical issues surround mcAb
- requires mice
> is it justified to use animals for the better treatment of humans
