Cells Flashcards
Eukaryotic cells
plants, algae, animals and fungi
this means that all cells have a nucleus and membrane bound organelles
The nucleus
contains DNA arranged in chromosomes
within chromosomes there are genes that code for the primary structure of polypeptide
the nuclear envelope-double membrane that surrounds the nucleus, controls exit and entry of substance in nucleus and compartmentalises reactions
nuclear pores- allow passage of large molecules out of nucleus e.g. mRNA
Chromatin- linear DNA protein bound that condenses into visible chromosomes in division
the nucleolus- small but inside nuclearplasm, manufactures rRNA and ribsomes may be more than 1
function of the nucleus
1.stores genetic info codes for primary structure
2.protein synthesis requires mRNA production via transcription
3.also requires rRNA production to make ribsomes
4.where semi Conservative dna rep occurs
The mitochondrion
Where ATP is synthesised by aerobic respiration
double membrane- control entry and exit of molecules in and out of mitochondria
cristae- extentions form fold of inner membrane, provide Large SA for enzymes in aerobic respiration
The intermembrane space-space between inner and outer
The matrix- contains proteins,lipids, Mitochondrial DNA and 70s ribsomes
endoplasmic reticulum
RER- has ribsomes on its outer surface membrane
provide Large SA for protein synthesis
packages proteins into vesicles + transports them to golgi apparatus to be modified
SER- lacks ribsomes
synthesis, store and transport lipids
synthesis, store and transport carbs
packages triglycerides and carbs into vesicles and transport to the golgi
The golgi apparatus
sorts and modifies proteins by adding carbs or lipids on to them
modified proteins are packaged into vesicles, pinched off from the ends of the cisternae
exocytosis- vesicle moves to and fuses with cell surface membrane releasing contents to the outside
also forms lysosomes
Lysosomes
contain and release hydrolytic enzymes also contain lysozymes, enzymes that hydrolyse walls of certain bacteria
single membrane forms a sphere , isolate hydrolytic enzymes from rest of cell , prevents any unwanted breakdown of cells ultrastructure
functions-
fuse with foreign material ingested by phagocytic cells and release enzymes
release enzymes to outside of cell in order to hydrolyse and breakdown molecules outside of cell
the breakdown damaged and worn out organelles so molecules can be reused
completely breakdown cells after they have died- autolysis
ribsomes
made up of rRNA and proteins needed to synthesis proteins.May be found in cytoplasm or attached to membrane of RER
80s- larger and eukaryotic
70s- smaller and prokaryotic
cell surface membrane
controls the passage of molecules in and out of the cell
made of phosolipid bilayer and fluid mosaic model
differences between animal and plant cells
plant cells have
cell wall
chloroplast
vacuole
carbs stored as starch
don’t have-
glycogen
chloroplast
carry out photosynthesis
chloroplast envelope- double membrane that surrounds organelle controls what enters and exits
grana- stack of up to 100 discs called thylakoids which are also made from membranes, within membrane is the photosynthetic pigment called chlorophyll
stroma- fluid filled matrix, synthesisnof sugar
large SA for more chlorophyll
contain circular DNA and own 70s ribsomes
cellulose cell wall
consist of microfibrils, adds strength and overall rigidity
prevents cell from bursting under pressure
vacuoles
fluid filled sack bound by a single membrane
support cells
sugar and A acid storage
pigments stored here
cell specialisation
specialised cells form tissues
different tissues grouped into organs
different organs grouped into organ systems .
cells become specialised by gene expression
prokaryotic cell
don’t have nuclei or other membrane bound organelles
pro vs eukaryotic cell
pro have circular DNA not linear
pro DNA isn’t associated with histone and contains no intorns
pro don’t contain membrane bound organelles
pro has no true nucleus
pro has smaller ribsomes
pro can have capsules, one or more flagella and plasmids
pro have cell wall made of murine
viruses
acellular
very small and require living cells to replicate inside
contain DNA or RNA
genome surrounded by a protein coat called a capsid
envelope contains attachment proteins- bind to host cells
had an enzymes that replicates genetic info and inserts it into host DNA
viruses have no organelles so can’t replicated independently
light microscopes
specimens are illuminated by light and focused with a glass lense
can be living or dead
often have to be stained
limited to 1500x as at higher mags it loses resolution max res of 200nm
only see large organelles
eye peice graticule and stage micrometer
graticule- fits onto eyepiece like a ruler with numbers but no units
stage micrometer is a microscops slide with an accurate scale
use stage micrometer to calibrate eye peice graticule at certain mags
line them up
each division of stage is 10 micrometer is 24 is 240ųm in total
so if 90 divisons sit in this space
240/90= 2.67 ųm per eyepiece graticule divisions
then u can measure stuff
electron microscope
use a beam of electrons to illuminate specimens
has a very short wavelenght and so has a high resolving power 0f 1 NM and a mag of 500000×
can observe small organelles
have to be dead
TEM- go through specimen and enable veiw of internal structures
fixed in resin and sliced thin, thicker areas absorb more so it is darker
in a vacuum
stained using heavy metal
can create artifacts
SEM-
electrons bounce of surface
produce 3d image
light vs electrons
light-
illumination-light rays
focused by- lens
mag-x1500
res-200nn
can see large organelles
specimens- living
staining process- easy
electron-
beam of electrons
electromagnets
500000×
1nm
smaller organelles
dead
complex
magnification equation
actual size= image size/ mag
cell fractionation and ultracentrifugation
step 1) homogenised tissue in blender in a ice cold, isotonic and buffer solution
step2) filter to remove large peices producing a supernatant
3) differential centrifugation carried out, on a low speed the densest organelles are removed first and form pellets at the bottom which are remiver
4) then at a higher speed and less dense form pellet
5) repeat many times
nucleus is densest then chloroplast and mito then ribsomes
cell cycle
interphase (growth and semi Conservative replication)
nuclear division (mitosis)
cell division (cytokinesis)
movement from one phase to another is triggered by group of chem signals called cyclins
interphase
when cell increases in mass and size preps cell for division by synthesising proteins and replicating its DNA
G1 phase- cells make RNA enzymes and proteins required for growth, in this phase a signal is received telling cell to divide again
S phase- Repicated DNA semi Conservatively resulting In 2 sister chromatids
G2 phase- continues to grow I’m prep for mitosis e.g. form mitotic spindles and DNA is checked for errors
prophase
prophase-
chromosomes condense and are visible
these consist of 2 identical sister chromatids that are joined at centrometer
2 centrioles moved towards opp poles of cell
nuclear membrane breaks down into small vesicles
spindle fibres begin to emerge from centrioles
metaphase
chromosomes line up at the equator of the cell
chrosomes attach to spindal fibres by their centeomeres
anaphase
spindle fibres shorten and centromere splits
this pulls the sister chromatids to the opp poles of the cell
telephase
chromosomes arrive at opp poles and begin to uncoil
the spindle fibres break down
nuclear envelope begin to reform around each set of chromosomes
cytokinesis
final step in cell cycle
cytoplasm divides forming 2 genetically identical daughter cells
After mitosis( propahse metaphase anaphase and telophase)