2.1 Cells Flashcards
How big are prokaryotic cells?
0.1 - 10 micrometeres
How big are eukaryotic cells?
10-100 micrometeres
What are the key features of a prokaryotic cell?
- DNA is free in the cytoplasm
- DNA is not associated with proteins
- smaller ribosomes (70S)
- No memrane bounded organelles
- cell wall is made of glycoprotein = murein
- slime capsule around cell wall
- plasmids are present
- No mitochondra present
- 0.1-10 micrometres
What are the key features of a Eukaryotic cell?
-DNA bound by nuclear membrane
- DNA associated with proteins
- has membrane bounded organelles
- larger ribosomes (80S)
- no plasmids present
- mitochondria are site of respiration
- no slime caspsule around cell wall
- cell wall made of cellulose/ chitin
- 10-100 micrometeres
What kinds of cells make up animals/ larger organisms?
Eukaryotic
What kind of cells makes up bacteria and viruses?
Prokaryotic
What is the prokaryotic cell wall made of in bacteria?
murein
How do bacteria protect themselves?
secreting a capsule of mucilaginous slime
What is the cell-surface membrane?
alipid bilayer that is semipermeable, biological membrane that separates and protects the interior of a cell from the outside environment.
It controls the entry and exit of chemicals
What are bacteria’s food reserves?
glycogen granuales and oil droplets
What is the capsules function?
protects bacterium from other cells and helps groups of bacteria stick together for further protection
What are plasmids?
possesses genes that may aid the survival of bacteria in adverse conditions eg. produces enzymes that bread down antibiotics
they are responsible for an antibiotic resistance or any resistances
What are the features of a virus?
-non-living
- smaller than bacteria = 20-300 nm
- contains nucleic acids such as DNA or RNA as genetic material
- can only reproduce in the hosts cell
- nucleic acid is enclsed within a protein coat called the capsid
- HIV = further surrounded by a lipid envelope
- capsid/ lipid envelope have attachment proteins to identify the virus and to attach to host cell
What is chromitin?
DNA wrapped around proteins = DNA protein complex
What does envelope mean?
has two membranes
Why aren’t there mitochondria present on a diagram from a light microscope?
they are too small to be seen on a light microscope
What is the middle lemella?
the sticky layer between the cell wall and the cell membrane
Where do new cells come from?
existing cells in mitosis, meiosis and binary fission (in bacteria)
Why aren’t viruses living?
it is not made up of cells
What processes in a cell need energy?
protein synthesis, cell division, DNA replication
Where does a cell get its energy from?
respired glucose in mitochondria in the form of ATP
What are cell membranes made of?
Phospholipid bilayers
What is a selectively permeable membrane?
it SELECTS what enters and exits the cell
What is an organelle?
a sub-cellular structure that carries out a particular function
Why do cells need membranes?
- the functions are carried out in the organelles which are membrane bounded
- seperates the organelle from the cytoplasm
- increases surface ares for reactions, diffusion and transport
What is the function of a neurone and its specialisation?
function= transport electrical implulses
specialisation = long conducting fibres, has many dendrities to from synapses with other neurones
What is the root hair cells function and specialisation?
function = apsorption of water and mineral ions
specialisation = large surface area, has a lot of mitochondria for ATP for apsorption
What is the function of a xylem vessel cell and its specialisation?
function = transport water through plants
specialisation = lignin present in cell walls to provide structual support, cell are dead and empty to allow transport of water
What is the sperm cells specialisations?
- flagella for motility
- packed with mitochondria for ATP
- head contains enzymes to digest tissues surrounding egg cell
What is the function and specialisation of an epithilial cell in the ileum (the final portion of the small intestine)?
function = apsorbtion of produce of digestion
specialisation = membrane folded to form microvilli for more surface area for apsorbtion , many mitochondria present
What is the function and the specialisation of the skeletal muscle cell?
function = contracts to move skeleton
specialisation = contains protein filaments which can move and cause contraction
Where is chromatin stored?
in the nucleoplasm
What parts are present in an animal cell?
-cytoplasm
- cell membrane
- mitochondria
- nucleus = nucleolus, nuclear envelope, nucleoplasm
What is present in a plant cell?
-Cell wall
-middle lamella
- chloroplasts
- vacuole sap
- cytoplasm
- vacuole membrane (tonoplast)
- cell membrane
- nucleus = nucleolus, nuclear envelope, nucleoplasm
What is a tonoplast?
a single membrane that bounds the vacuoles and separates it from cytoplasm
What is present in a chloroplast?
- envelope = inner and outer membranes
- Thylakoid
- granum
- stalked particles
- starch grain
- stroma
-lamella
What is the Thylakoid in a chloroplast?
where the chlorophyll is stored
What is a granum in the chloroplast?
a stack of thylakoids
What are stalked paticles?
where ATP syntesis takes place
What is a starch grain in a chloroplast?
used to store starch which will provide food for the plant
What is the stroma in a chloroplast?
the plasm = has DNA and ribosomes
Where is sap stored in a plant cell?
vacuole membrane
How does the mitochondria have more surface area?
membrane folds
What is the golgi body’s function?
chemically modifys proteins
packages proteins for exocytosis
What is a vesicle?
animals cell temporary vacuole
What does exocytosis mean?
process by which the contents of a cell vacuole are released to the exterior through function of the vacuole membrane with the cell membrane
What is the function of the smooth endoplasmic recticulum?
lipid synthesis and transport
What is the function of the rough endoplasmic recticulum?
protein synthesis and transport
What are the endoplasmic recticulums made of?
cisternae - lipids
What is cisternae?
membrane bound sacs
What are the difference between the smooth and rough endoplasmic recticulum?
rough has ribosomes
What is present in a golgi body?
lysosome / secretary vesicle
maturing face
cistene
lumen
transport vesicle
forming face
What is the function of the cell wall?
provides strength and rigidity to the cell
prevents osmotic lysis
What is osmotic lysis?
when a cell bursts due to an osmotic imbalance that has caused excess water to diffuse into the cell
What is present in the cell wall?
cell wall
cell membrane
middle lemella
plasmodesma
cytoplasm
What does hyrdrophylic mean?
attracted to water molecules
What are the function of the centrioles?
they form spindal fibres in animal cells that are needed for cell division
What is the structure of the centrioles?
they are at right angles to each other
made of microtubles
9 triplets of microtubles
What is a lysosome made of?
membrane
hydrolytic enzymes
What are the functions of a lysosome?
phagocytosis
autophagy (self-eating)
autolysis (cell bursts and is digested from the inside)
What is the structure of a ribosome?
large subunit
mRNA
small unit
sub-units come together around mRNA
made of protein and rRNA
What are the functions of a ribosome?
protein synthesis
What is mRNA?
carries the code for protein syntesis
What is present in a vacuole?
tonoplast
sap
What is the function of a vacuole?
stores sap (sugars and amino acids and water) which maintains turgility
prevents wilting
What is the function of the nucleus?
stores DNA and holds the code for protein synthesis
What is the nucleus made of?
chromatin
nuclear pore
nucleus plasm
nucleur envelope
nucleolus
What is the nuclear pore function?
transport of substances
nucleotides can transport in
rRNA transport out
What does the nucleolus do?
synthesises rRNA
What is present in a cell membrane?
phospholipid bilayers
phosolipid head
intrinsic protein
extrinsic protein
channel protein
cholesterol
surface protein
glycolipid
glycoprotein
fatty acid tails
Where is the protein code stored in the nucleus?
in the nuclear plasm that contains the cells DNA which is the genetic code for the proteins to be synthesised by the cell
Why is DNA transcribed into mRNA during protein synthesis?
DNA is too lage to leave via the nucleus pore
mRNA is small enough
What is the purpose of the nucleus in protein synthesis?
where the protein code is stored on the DNA
What is the role of the ribosomes during protein synthesis?
they synthesise the proteins
once the proteins have been synthesised they can pass intothe cistene and leave the RER, enclosed in a membrane
What is the role of the transport vesicle during protein synthesis?
budded off the cistene of the RER
transports the synthesised proteins through the cytoplasm to the golgi body
fuses with the membrane of the cistene of the golgi body = transferring proteins inside the golgi body’s cistene ( the forming face)
What is the role of the golgi body in protein synthesis?
where proteins are chemically modified into more complex molecules
at the end of the golgi body, proteins are packeged into secretary vesicles of lysosomes
What do secretary vesicles do during protein synthesis?
exocytosis:
move towards the celll membrane and fuse with it, releasing the proteins out of the cell
What is the role of the lysosomes during protein synthesis?
contain hydrollytic enzymes
they fuse with temporary vacuoles and digest the contents of the vacuole
they can burst, releasing the hydrollytic enzymes into the cytoplasm = the cell will start to digest itself = autolysis
what does release mean?
made somewhere else and is leaving
What does secrete mean?
made there and released in same place
what does cell agrigation mean?
to combine/ group cells
What is a tissue?
group of simular cells working together to perfrom the same function
What is an organ?
a group of different tissues working together to perfrom the same function
What is a muscle?
tissue/ organ if backed up with evidence
What plant tissue transports nutirents?
phloem
What is the function of a lysosome?
digestion and removal of cell parts and toxins
What is an object?
the material you put under the mircoscope
What is the image?
the appearance of material when viewed with a microscope
What is the magnifictaion?
how many times bigger the image is when compared to the object
What is the resolution?
the minimum distance apart two objects can be in order for them to appear seperate in the image
Why does the electron microscope have a higher resolution?
a wavelength of the electron beam is shorter than a light wave
What is 1 micrometer in nanometers?
1000 nm
What is 1mm in micrometers?
1000 micrometers (um)
How many mm in a m?
1000
What does km measure?
ecosystems
what do metres measure?
larger organisms
What do mm measure?
tissues
What do micrometres measure?
cells and organelles
What do nm measure?
molecules
How do you calculate the object size from an image?
- measure image in mm
- x1000 to convert to um
- divide by magnification
length(mm) x 1000/ magnification
How do you calculate the magnification of an image?
- measure length of scale in mm
- x1000 to convert to um
- divide by scale value
length of scale(mm) x 1000 / scale value (um)
How do you work out image size? (equation)
image = magnifcation x object size
How does a light (optical) microscope work?
long wavelengths of light go through through the specimen
What must be done to the specimen to view it under an electron microscope?
must be viewed in a vacuum
and it must be dried out and dead as water boils at room tempreture in a vacuum
What is a photomicrograph?
photography of objects under a microscope
What is an artefacts?
anything that appears in the photomicrograph that is not present in the cell
How does a transmission electron microscope work?
electron beams goes through the specimen
darker areas = more elctrons have been absorbed
How does a scanning electron microscope work?
electron beams pass over the objects surface
What type of mounting slide do each type of microscope use?
optical = glass
electron = metal grid
How are are the specimens viewed on each type of mircroscope? (living/dead)
optical = living/dead
electron = dead
What staining techniques are used on each type of microscope?
optical = coloured dyes or stains
electron = heavy metal salts/ ions
What are the colour of the images produced on each type of microscope?
optical = coloured
electron = black and white
What magnification is acheived on each type of microscope? (high/low)
optical = low
electron = high
What is the focusing mechanism for each type of microscope?
optical = glass lenses
electron = electromagnetic lenses
What is the resolution on a optical microscope?
low = 250 nm
What is the resolution on a TEM ?
very high = 0.1 nm
What is resolution on SEM?
high = 2nm
What microscope produces 3D images?
SEM
Where in prokarytic are the enzymes that carry respiration?
cytoplasm
Why can’t virues carry metabolic processes?
non-living
no enzymes
no way of synthesising enzymes
What is a bacteriophage?
a virus which only infects prokarkyotic cells
a virus parasitizes (infest as a parasite) a baterium by infecting it and repreducing inside it
What is ths the purpose of the flagellum?
helps with motility = ability to move through water
What molecules make up the caspid?
proteins
How does a virsus protect itself?
enters the host’s cell and wraps their caspid with the host’s cells membrane
it protects itself by creating a lipid envelope which protects the DNA/RNA from the environment and it hides the viral antigens
How do you work out the total magnification?
eyepiece magnification x objective lens magnification
What is the ultrastructure?
fine structure like sub-cellular structures and organelles within a cell that can only can seen with a high resolution electron microscope
How do you calibrate a microscope?
- line up the stage micrometer and the eyepiece graticule whilst looking through the eyepiece
- count how many divisions on the eyepiece graticule fit into 1 division on the micrometer scale
- Work out coversion factor
- remove stage micrometer and insert slide of choice
How do you work out the coversion factor for 1 eyepiece unit?
no of divisions on stage micrometer x length of each division (um) (100)
divided by = no of divisions on eyepiece graticule
What is cell fractionation?
the process where cells are broken up and the different organelles are seperated
What does cell fractionation enable us to do?
isolate cell components
study structure and functions of organelles
What is the order in which cell fractionation takes place?
homogenise
cold solution
isotonic solution
buffered solution
filter
ultracentrifugation
Why are tissues placed in a cold solution for cell fractionation?
to reduce enzyme activity that might damage or break down organelles
Why are tissues placed in a buffered solution for cell fractionation?
so that the pH is constant and doesn’t alter the structure of the organelles or affect enzyme activity
Why are tissues placed in a isotonic solution for cell fractionation?
to prevent organelles bursting or shrinking due to osmotic gain or loss (osmosis)
What is homogenation?
cells are broken up by a homogeniser (blender) to release organelles
What is the homogenate?
resultant fluid from homogenation
Why is the homogenate filtered?
to remove any complete cells and unwanted/large debris
What is the process of ultracentrifugation?
break open cells/tissues and filter = homogenate
placed in cole, buffered and isotonic solution
the homogenate is placed in a centrifuge and first spun at a low speed
this removes the heaviest organelles (nuclei) from the solution at the bottom of the tube this is called the pellet
the fluid at the top of the tube is transferred into a different tube and respun again at a higher speed
this repeats increasing speeds until all organelles are seperated out
What are the heaviest to lightest organelles?
heaviest:
nuclei
mitochondria/chloroplasts
lysosomes
endoplasmic reticulum
ribosomes
lightest
What is ultracentrifugation?
fragments in homogenate are seperated by spinning them in a centrifuge
Why is the resolution too low on an optical microscope?
the wavelength of light is too long
Why is the resolution too low on an optical microscope?
the wavelength of light is too long
What are features of a cell that allow protein synthesis?
DNA or ribosomes
What are the advantages of using a TEM than a SEM?
high resolution from TEM
can view the internal structures
