cells Flashcards
eukaryotic cell is…
cell with membrane bound organelles
can become specialised by process of differentiation
cell surface membrane
phospholipid bilayer
controls entry and exit of substances, sometimes requires active transport or membrane proteins
nucleus
double membrane
contains chromosomes
mitochondria
double membrane
fold called cristae (large SA)
site of aerobic respiration
chloroplasts
plants only
double membrane
site of photosynthesis
geranium (stack) individually called thylakoids
geranium connected by lamella
stroma (fluid)
Golgi apparatus/body
modifies proteins
role in ‘packaging’ and secretion of proteins
made of flattened sacs called cisternae
circles pf diagrams are Golgi vesicles which take proteins and get them ready for export
lysosomes
small membranous vesicles
breaks down ‘unwanted’ cells/organelles
contain lysozymes (enzymes that kill pathogens)
ribosomes
round shaped organelles that synthesise protein
some attach to surface of rough ER
rough endoplasmic reticulum
large no. of ribosomes attached to surface
synthesise and ‘make changes’ to proteins
smooth endoplasmic reticulum
no. of ribosomes on surface
lipid synthesis
toxin modification
glycogenesis
cell wall
plants only
determines strength, shape and support
composed of cellulose
controls tutor pressure
vacuole
membranous sacs
store water, nutrients and waste products
prokaryotic cells
no membrane bound organelles
smaller than eukaryotes
smaller ribosomes
DNA is not encoded in nucleus
DNA= singular circular molecule, not associated with proteins
may have plasmids, capsule and flagella
basic structure of a virus is…
genetic material can be DNA or RNA
capsid coats material, protects it
attachment proteins- attach to receptors on host cells and allow the virus to enter and inject genetic material
magnification is…
how large an image is compared to real life
resolution is…
the minimum distance where two objects are distinguishable as two objects
features of an optical microscope
light focused through condenser lens, then through specimen where certain wavelengths are filtered
light passes through objective sense, then to eye piece sense to provide visible images
max mag= x1500
max res= 200um
can view live specimens and observe processes
features of transmission electron microscope
electrons pass through specimen, denser parts absorb more electrons so appear darker ]max mag= x500000 max res= 0.1nm
cannot view live specimens or processes as interior is a vacuum so specimen has to be sliced very thinly
requires extensive staining process that can lead to artefacts
features of scanning electron microscope
produces 3D image
electrons ‘bounce off’ specimen and are detected at multiple detectors
max mag= x100000
mag res= 20nm
how is actual size measured
using eye piece graticule, calibrated using a micrometer
1. line up graticule with micrometer
2. count no. of graticule division that correspond with a set measurement on stage micrometer
3. calc. distance in um of one division on eye piece graticule
ultracentrifugation is…
used to separate cell components or to get s cell-free liquid
how to ultracentrifuge
- cells homogenised to break open cells
- places in cold (prevents enzyme activity), isotonic (prevents osmosis) and buffered solution (prevents pH changes that could denature proteins)
- filter to get rid of debris
- centrifuge at low speed, separates nuclei as pellets at bottom of tube, solution called supernatant
- centrifuge at high speed, separates mitochondria and chloroplasts as pellets and the bottom
- repeat again and again, ER and Golgi next
- ends up as cell free solution
cell cycle includes…
G1, S phase, and G2
mitosis is…
nuclear division, eukaryotic cell divides to produce 2 genetically identical daughter cells
division of the nucleus is mitosis, and division of the cell is cytokinesis
stage 1 of mitosis is…
interphase=
G1- proteins synthesis and cell grows large
S phase- DNA replication
G2- additional growth
stage 2 of mitosis is…
prophase=
chromosomes condense and become visible
nuclear envelope breaks down
mitotic spindle forms
stage 3 of mitosis is…
metaphase=
chromosomes line up at the equator
mitotic spindles attach to the centromeres
stage 4 of mitosis is…
anaphase=
sister chromatids separate at the centromere and are pulled to opposite poles of the celery the mitotic spindle
stage 5 of mitosis is…
telophase=
spindle fibres disappear and nuclear envelope reformed
chromosomes start to de-condense
cytokinesis occurs
what happens if mitosis goes wrong?
mutations cause uncontrolled cell division, forming tumours and caner
many cancer treatments directed at controlling rate of cell division
most prokaryotes don’t undergo mitosis, they…
undergo binary fission
circular DNA and plasmids are replicated
cytoplasm divides, so a single copy of circular DNA and variable plasmid copy numbers
structure of a cell surface membrane
phospholipid bilayer
glycoproteins and glycolipids (aid in cell attachment)
channel proteins and carrier proteins (allow large/polar/water soluble molecules past the membrane
cholesterol (restricts movement to provide stability)
simple diffusion is…
movement of small, non polar particles through the phospholipid bilayer
facilitated diffusion is…
movement of larger molecules through channel proteins or carrier proteins
channel proteins= molecules pass through
carrier proteins= molecules move in, tertiary structure of protein changes, allows molecule to enter the cell
active transport is…
movement against concentration gradient using carrier proteins, requiring ATP hydrolysis
co-transport is…
2 molecules transported together, one going down conc. gradient, other going up
e.g. small intestine= Na+ and glucose transported from lumen to epithelium
Na+ actively transported into blood, K+ goes into epithelium from blood, glucose goes into blood via facilitated diffsuion
osmosis is…
movement of water molecules across selectively permeable membrane from high water potential to low water potential (relative tendency of water to move from one place to another)
adaptations of cell membranes are…
increases SA (folds)
increased no. of channel/carrier proteins
what does each type of cell have on their surface
specific molecules to identify things like pathogens, abnormal body cells, toxins
antigens are…
foreign proteins on cell-surface membrane that stimulate an immune response
phagocytosis and its steps are…
engulfment of pathogen by a phagocyte
1. phagocyte attracted to pathogen and binds to receptors
2. pathogen engulfed by phagocyte via endocytosis, phagosome formed (visible containing pathogen)
3. lysosomes fuse with pathogen, lysozymes break down pathogen into soluble materials
lymphocytes= B (mature in bine marrow, involved in humeral response) + T cells (mature in thymus gland, involves in cell-mediated response)
the cell-mediated response is…
T cell receptors binds to antigen presenting cell, stimulates differentiation of T cells, Helper T cells formed, cytoxic T cells (produce perforin which makes holes in cell membrane) can also stimulate phagocytosis
the humoral response is…
Helper T cells stimulate B cells to rapidly divide by mitosis to form clones of plasma checks (clonal selection)
plasma cells produce antibodies that have specific shape to antigen so they attach and destroy the pathogen
agglutination= antigen-antibody complex all stick together, allows for easier digestion via phagocytosis
antibodies are…
proteins with complementary binding sites to antigens, and destroy the pathogens
involved in humoral response
features of vaccination…
dead/inactive pathogen
initiates a primary response
leading to formation of memory B cells
upon reinfection, secondary response is stimulated
provides herd immunity
ethical issues of vaccination are…
should they be compulsory?
who should they test on?
are they 100% effective long-term?
active and passive immunity is…
active= results from production by immune system in response ti presence of antibody
passive= results from introduction of antibodies from another person/animal
monoclonal antibodies are…
type of antibody isolated from a single clone of B cells
used in drug testing (specific ti the target if the drug)
ethical issues= use mice to produce them
ELISA is and its steps are…
test used in detection of antigens
1. antigen of interest immobilised
2. monoclonal antibodies added + bind to appropriate antigen
3. apparatus washed to remove unbound antigens
4. more monoclonal antibodies added, linked to colour changing enzymes and bind to antigens
5. washed again
6. complementary substrate to enzyme added, triggering colour change upon binding, thus showing presence of antigen
features of HIV…
spikes on the edge called glycoproteins
capsid to protect the genetic material
HIV replication
attaches to CD4 receptors on the Helper T cells
RNA + enzymes enter host T cell
viral RNA copied to cDNA by reverse transcriptase
cDNA moves into T cell nucleus where it is transferred and translated using host machinery to produce viral proteins
that makes new viruses
new virus particles break off T cell membranes
how does HIV cause AIDs?
helper T cell dies when new HIV particles break off membrane
decreased B cell stimulation= decreased immunity
vulnerable to infection that are fatal
HIV drugs often target reverse transcriptase
antibiotics are…
ineffective against viruses
kill bacteria
