3 cell structure Flashcards
how do you calculate magnification?
size of image/size of real object
how do you calculate the size of the object under a microscope?
size of image/magnification
what is resolution for a microscope?
the minimum distance apart 2 objects can be in order for them to be visible as 2 different items
what does cell fractionation do?
breaks up cells so it’s different organelles are separated out
before cell fractionation can begin, what does the tissue need to be placed in?
a cold buffered solution
why is the solution that the tissue has to put in before cell fractionation cold and buffered?
cold- to reduce enzyme activity that might break down the organelles
buffered- so the pH doesn’t change and alter organelles/enzymes
what are the 2 steps of cell fractionation?
- homogenation
- ultracentrifugation
what happens during homogenation?
- cells are broken up by a homogeniser (blender) which releases the organelles
- the remaining fluid (homogenate) is filtered to remove complete cells/debris
what is magnification?
how many times bigger the image is compared to the object
explain ultracentrifugation
- filtered homogenate is spun in a centrifuge at a low speed- forcing the heaviest organelles to the bottom of the tube
- fluid at the top of the tube is removed and transferred into another tube and spun at a faster speed in the centrifuge- forcing the next heaviest organelles to the bottom of the tube
- continued at higher speeds each time
rank these 3 organelles in order of weight, heaviest first:
mitochondria, nucleus, lysosome
nucleus, mitochondria, lysosome
what is the layer of heaviest organelles called at the bottom of the tube after ultracentrifugation?
pellet
what are the two types of electron microscope?
transmission electron microscope
scanning electron microscope
compare a light microscope and an electron microscope (4)
LIGHT: can view living samples
ELECTRON: sample must be in a vacuum so cannot be living
LIGHT: lower magnification
ELECTRON: higher magnification
LIGHT: colour images
ELECTRON: black and white images
LIGHT: poorer resolution as light has a longer wavelength
ELECTRON: higher resolution as electrons have a short wavelength
what is not visible in a light microscope?
small organelles such as parts of the mitochondria
what is the difference between a TEM and SEM?
TEM: extremely thin specimens are stained and placed in a vacuum where an electron gun produces a beam of electrons that pass through producing a 2D image
SEM: specimens do not need to be thin as electrons do not pass through- electrons beamed onto the surface and scattered creating a 3D image
what 11 organelles are in eukaryotic cells?
- cell surface membrane
- nucleus
- mitochondria
- ribosomes
- lysosomes
- rough endoplasmic reticulum
- smooth endoplasmic reticulum
- golgi body and vesicles
- chloroplasts
- cell wall
- cell vacuole
what is the structure of the nucleus?
nuclear envelope (double membrane)
nuclear pores
nucleolus
chromosomes
what is the function of the nucleus?
- site of DNA replication and transcription
- contains the genetic material of the cell
what is the structure of the RER?
- folded membranes called cisternae
- ribosomes on outer surface
what is the function of the RER?
site of protein synthesis
what is the structure of the SER?
folded membranes called cisternae
what is the function of SER?
synthesise, store and transport carbs and lipids
what is the structure of the golgi apparatus?
- folded membranes making cisternae
- vesicles
what is the function of the golgi apparatus?
- modify proteins into glycoproteins
- produce secretory enzymes
- transport and modify lipids
- form lysosomes
- “label” molecules
what are lysosomes?
bags of digestive enzymes
what is the function of a lysosome?
- hydrolyse phagocytic cells
- exocytosis- release enzyme
- digest worn out organelles
what is the structure of mitochondria?
- double membrane
- cristae
- matrix
- circular DNA, ribosomes in matrix
what is the function of mitochondria?
site of aerobic respiration and ATP production
what type of ribosomes are found in eukaryotic cells?
80s
what type of ribosomes are found in prokaryotic cells?
70s
what are ribosomes made up of?
a large and a small sub unit made up of rRNA and proteins
what is the function of a ribosome?
site of protein synthesis
what is the vacuole made up of?
fluid filled sac with a single membrane called tonoplast
what is the function of a vacuole?
- makes cells turgid
- stores sugars and amino acids for food store
- pigments colour petals
what is the structure of a chloroplast?
- double membrane
- grana (stacks of thylakoids)
- lamellae
- stroma (contains enzymes)
what is the function of a chloroplast?
site of photosynthesis
what are cell walls in plants made up of?
microfibrils of cellulose
what are cell walls in fungi made of?
chitin
what is the function of a cell walls?
strengthen cell and prevents cell from bursting
what is the cell wall made up of in bacterial cells?
murein
what is a capsule on a prokaryotic cell?
capsule of slime that coats and protects the cell
contrast prokaryotic and eukaryotic cells
PRO: no nucleus
EUK: nucleus present
PRO: circular DNA
EUK: linear DNA
PRO: no membrane bound organelles
EUK: membrane bound organelles
PRO: cell wall made of murein
EUK: cell wall made of cellulose or chitin
PRO: DNA not associated with proteins
EUK: DNA associated with histones
what is the structure of a virus?
- genetic material
- attachment proteins
- capsid
- matrix
- lipid envelope (on HIV)
how do viruses replicate?
inside of cells
how do viruses attach to host cells?
through attachment proteins
how do eukaryotic cells replicate?
mitosis and meiosis
how do prokaryotic cells replicate?
binary fission
how do viruses replicate?
inside a host cell- invading the cell by injecting their nucleus acid in cell to replicate virus particles
what are the stages of the cell cycle?
G1 (interphase)
S (interphase)
G2 (interphase)
mitosis
what is G1 phase?
the cell increases in size
what is the S phase?
where semi conservative DNA replication takes place
what is G2 phase?
organelle growth
what is mitosis?
division of a cell resulting in 2 identical daughter cells
what happens during interphase?
replication of DNA
2 copies joined at centromere
what happens during prophase?
chromosomes condense and become visible
what happens during metaphase?
chromatids joined by the centromere arrange themselves in the equator of the cell
what happens during anaphase?
the centromeres divide into 2 and spindle fibres pull the chromatids apart.
chromatids move to opposite poles of the cell
what pulls the chromatids apart?
spindle fibres at opposite poles of the cell
what happens during telophase?
chromosomes reach their poles and become longer and thinner
spindle fibres disintegrate
what happens during cytokinesis?
cytoplasm splits
what is a tissue?
a collection of similar cells that group together perform a specific function
explain binary fission
- circular DNA replicates and both copies attach to cell membrane
- plasmids also replicate
- cell membrane begins to grow and DNA molecules pinch inwards- dividing the cytoplasm
- a new cell wall forms between two molecules producing two identical daughter cells
how is cancer treated?
by disrupting the cell cycle by:
- preventing DNA from replicating
- inhibiting the metaphase stage of mitosis by interfering with spindle formation
what is a pro and con of the treatment of cancer?
con: disrupt the cell cycle of normal cells
pro: more effective against rapidly dividing cells
