Cells and microscopes Flashcards
what are eukaryotic cells
have a nucleus and organelles enclosed within membranes (e.g. mitochondrion)
can become specialised for specific functions
cell membrane
phospholipid bilayer is partially permeable so can control substances going in and out of the cell
nucleus
enclosed by a double membrane
contains chromosomes consisting of protein bound li near DNA and one or more nuclei
what does DNA control
protein synthesis
what do nucleoli make
ribosomes
mitochondria
rod shaped cell consisting of outer and inner membrane
inner membrane folds to form cristae containing ribosomes, enzymes and circular DNA molecule
increases the SA for enzymes and other proteins of respiration
site of aerobic respiration
produces ATP
chloroplasts
surrounded by two highly selective membranes containing a stroma
what does the stroma of a chloroplast contain
a system of membranes, circular DNA molecule, ribosomes, starch grains and enzymes of photosynthesis
what do the stacked membranes of a chloroplast form and what do they do
forms grana containing chlorophyll
provides a high SA for chlorophyll, electron carrier and enzymes of photosynthesis
Golgi apparatus
stack of flattened membrane bound sacs of cytoplasm
receives and prepares proteins synthesised on the endoplasmic reticulum to be secreted out of the cell
makes glycoproteins = carbohydrates + proteins
Golgi vesicle
transport glycoproteins and release its contents when fused with cell membrane
lysosomes
type of Golgi vesicle which contains digestive enzymes called lysozymes
lysozymes hydrolyse cell walls of bacteria
breaks down old organelles and cells and digests contents of vacuole to reuse useful chemicals
ribosomes
not bound by a membrane and made up of RNA and protein
consists of a large and small subunit
uses information in nucleic acid to synthesise proteins
endoplasmic reticulum
network of flattened membrane sacs called cirsternae forming a system of channels for transporting materials through the cytoplasm and storing glycoproteins and proteins
rough ER
transports proteins and contains ribosomes on the cytoplasmic side
provides high SA for glycoprotein and protein synthesis
smooth ER
does not contain ribosomes
synthesises and transports lipids and carbohydrates
cell wall
made up of cellulose microfibrils and other polysaccharides
provides mechanical support and protection (prevents cell from bursting from turgor pressure)
allows water to pass along it through the plant
vacuole
sac bounded by a single membrane (tonoplast) containing cell sap made up of a solution of mineral salts, pigments and organic acid
stores waste products
changes in its volume affects the turgidity of the cell
contains pigments resulting in colour petals which attract pollinating insects
centriole
spindle-shaped structure of protein fibres on which the chromosomes move during nuclear division
how are prokaryotic cells different to eukaryotic cells (8)
smaller and contains smaller ribosomes
does not contain membrane bound organelles
no nucleus
contains circular DNA not associated with proteins called a plasmid
cell wall is made of a glycoprotein called murein
contains a capsule - an outer mucilaginous layer
may have one or more flagellum
virus (5)
acellular and non-living
contains genetic material in the form of RNA or DNA
has a protein coat called a capsid enclosing nucleic acids
can only multiply in living host cells
have attachment proeins
what do attachment proteins do
identifies and attaches to a host cell
magnification definition
how many times bigger the image is compared to the real object
magnification equation (objects)
= apparent size of image/ actual size of object
magnification equation (scale bar)
= length of scale bar/ length scale bar represents
resolution definition
minimum distance apart that two objects can be in order to appear as separate items
how many lens systems does a optical (light) microscope have
3
eye piece
objective lens
condenser
properties of an image from a optical (light) microscope
coloured, inverted, low resolution
why do optical (light) microscopes have a low resolution
light has a relatively long wavelength
transmissions electron microscope (TEM)
parts of the specimen absorb the electrons from below and some let it pass through
limitations of transmissions electron microscope (TEM)
high energy electrons may destroy the specimen so limits resolution
vacuum so unable to observe living things
specimen needs to be thin to allow electrons to penetrate areas
properties of an image from a transmissions electron microscope (TEM)
flat, 2D, no colour
scanning electron microscope (SEM)
beam of electrons from above are passed back and forth at a specific portion so specimen does not need to be thin
contours of specimen scatters the electrons forming a pattern producing a monochromatic, 3D image
limitations of scanning electron microscope (SEM)
vacuum so no living specimens
has a lower resolution that TEM but higher than optical microscope
what is cell fractionation
process where cells are broken up and organelles are separated out
what are the three processes of cell fractionation
placing the tissue in a specific solution
homogenisation
ultracentrifugation
what solution is the tissue placed in for cell fractionation
cold, buffered, isotonic
why is the tissue placed in a cold solution
reduces enzyme activity which might break down organelles
why is the tissue placed in a buffered solution
keeps pH constant so there are no changed in structures of organelles which affect their function
why is the tissue placed in an isotonic solution
prevents cells from bursting (osmostic gain) or shrinking (water loss)
what is homogenisation
cells are broken up by a homogenizer (blender)
releases organelles from cells
homogenate is filtered to remove any complete cells
what is ultracentrifugation
filtered homogenate is put into a centrifuge where the organelles separate
centrifuge spins tubes of homogenate at a high speed to create a centrifugal force
heaviest organelles such as nuclei sink down to form the sediment pellet
lightest organelles make up the fluid at the top called the supernatant
how to measure cells
Calibrate an eye piece graticule using a stage micrometer
Measure length with eye piece graticule
Each unit on the micrometer scale is 10 µm
