Cell structure Flashcards
What is a eukaryotic cell (key definition)
a cell with MEMBRANE BOUND ORGANELLES
in plant and animal cells
structure and function of cell membrane
It is a phospholipid bilayer and its function is to allow extracellular substances to enter and for waste to exit the cell
structure and function of nucleus
is has a double membrane ( more efficient control of transport in and out )
contains chromosomes which consist of protein bound DNA (histones)
One or more NUCLEOLI which is for rRNA synthesis
Nuclear pores are there to transport transcribed mRNA into the cytoplasm
Structure and function of mitochondria
Has a double membrane
has cristae folds for a large surface area
site of aerobic respiration(ATP)
Structure and function of chloroplasts
Site of photosynthesis in plants
Stroma, thylakoids(granum) , lamella ( connects granum)
double membraned
Structure and function of the golgi body
Modification of proteins
Packaging and secretion of proteins (in Golgi vesicles)
made of cisternae
Structure and function of lysosmes
Small membranous vesicles
get rid of unwanted cells or organelles
contain lysozymes which destroy pathogens
Structure and function of ribosomes
Organelles that synthesise protein
some are attached to rough endoplasmic reticulum
structure and function of rough endoplasmic reticulum
has a large number of ribosomes attached to surface
synthesise and modify proteins
smooth endoplasmic reticulum
doesn’t have ribosomes attached
for lipid synthesis, toxin modification and glycogenesis
Cell wall structure and function
for strength and shape of cell
made of cellulose
controls turgidity ( regulates water content)
Vacuole structure and function
membranous sacs
stores water nutrients and waste products
much larger in plant cells
what type of cells can become specialised
eukaryotic cells
what is a prokaryotic cell and how are they different to eukaryotic
a cell with no membrane bound organelles
smaller than eukaryotes
they have smaller ribosomes
they have plasmids (rings of DNA for extra genetic material)
Where is prokaryotic DNA found
It is free in the cytoplasm as there is no nucleus
it is a singular circular molecule
also found in plasmids
what surrounds a prokaryotic cell and why
a capsule that is for attachment and protection from phagocytosis
why can prokaryotes move
as they have one or more flagella on the exterior of the cell
Full structure of viruses
Has genetic material (either DNA or RNA) encased in a CAPSID to protect it
have attachment proteins to attach to receptors of host cells to allow the virus to inject genetic material in for it to be replicated and produce more viruses
What is magnification
How large the image is compared to real life
What is resolution
the minimum distance where two objects can be clearly distinguished
3 types of microscopes
Optical light microscope
transmission electron microscope
scanning electron microscope
How do optical microscopes work and what is max mag and max resolution
light is focused through the objector lens on the bottom through the specimen
light passes through the objective lens to the eyepiece lens to produce an image
Magnification = 1500x
Resolution = 200 nm
How do TEMs work and max mag and res
electrons pass through specimen
and are focused by electromagnets to produce and image
denser parts absorb more electrons so appear darker
magnification = 500000x
resolution = 0.1 nm
Limitations of transmission electron microscopes
cant view live specimens as interior is a vacuum
specimen has to be sliced very thinly
requires expensive staining process that can lead to artefacts
why is the resolution of electron microscopes higher than light microscopes
electrons have a shorter wavelength than light
How do SEMs work and max mag and res
produce a 3D image as electrons bounce off the specimen and are detected at multiple detectors
magnification = 100,000 x
resolution = 0.1 nm
Formula for magnification
Mag = image size / actual size
How do you measure the actual size of an image through a microscope
use a eyepiece graticule and a stage micrometer
- line up graticule with micrometer
- count number of graticule divisions that correspond with the stage micrometer
- calculate distance in micrometres of one division on the graticule
What is ultracentrifugation used for and what is the process
- to separate cell components or to get a cell free liquid
- centrifuge your prepared solution at a low speed (separates nuclei into a pellet at the bottom) to leave a SUPERNATANT LIQUID
- Re spin the supernatant at a higher speed to separate mitochondria and chloroplasts
- Keep repeating at higher speeds to separate endoplasmic reticulum and Golgi body and eventually leaves a cell free liquid
How do you prepare a solution for ultracentrifugation
- homogenise(squash) cells to break them open
- place in a COLD, ISOTONIC and BUFFERED solution (prevent enzyme activity which could affect results)(prevents osmosis)
(prevents pH changes which could denature proteins) - Filtered to get rid of cell debris
what are artefacts in microscopes
excess staining that appear through transmission electron microscopes
Stages of the cell cycle
Growth 1 (
S phase (DNA replication)
Growth 2 (
(ALL PART OF INTERPHASE)
Mitosis
What is mitosis and what is division of the cell
A nuclear division
cell division is cytokinesis ( leaves 2 genetically identical daughter cells)
Stage 1 of cell cycle
Interphase
G1 - proteins are synthesised and cells grow larger
S phase - DNA replication occurs
G2 - additional growth
Stage 2 of cell cycle
Prophase
Chromatin supercoils so chromosomes condense and become visible
Nuclear envelope breaks down
spindle fibres form
Stage 3 of cell cycle
Metaphase
chromosomes line up on the equator
spindle fibres attach at the centromere
Stage 4 of cell cycle
Anaphase
sister chromatids are separated at the centromere
and pulled to opposite poles of the cell by spindle fibres contract
Stage 5 of cell cycle
Telophase
Nuclei are formed at both poles of the cell
and cytokinesis occurs leaving 2 genet iden daughter cells
How do prokaryotes divide
binary fission
circular DNA and plasmids are replicated and the cytoplasm divides
