Cell Biology (1)
pros and cons of lighg microscopes
cheap to make
allow you to see outline of cells
why do electron microscopes allow you to see sub-cellular structures?
they have greater resolving power and higher resolution
magnification equation
magnification : image size / object size
what types of cells are eukaryotic cells
plant and animal cells
what type of cells are prokaryotic cells?
bacteria cells
features of a eukaryotic cell
- semi permeable cell membrane
- nucleus storing dna
- mitochondria for respiration
- cytoplasm
- ribosomes for protein synthesis
features of a prokaryotic cell
dna strand in the cytoplasm
ribosomes
flagellum
what does a plant cell contain that an animal cell doesn't
chloroplasts containing chlorophyll for photosynthesis
permanent vacuole storing sap
cell wall made of cellulose
how do bacteria multiply
Binary fission: they divide every 20 minutes
making cultures with aseptic practical
- lift lid of petri dish towards flame to sterilise air by moving microbes away/killing them
- put a drop of culture on agar and spread evenly
- put drops of antibiotics on culture
- add tape to allow aerobic respiration and incubate at 25°C
- measure size of areas with no bacteria with pi r squared
how many chromosomes do we have?
all human cells have 23 pairs of chromosomes (diploid cells) except gametes (eggs/sperm) that have just 23 chromosomes [not pairs] (haploid cells)
mitosis process
- genetic material is duplicated
- nuclear membrane dissolves
- two sets of chromosomes line up along the centre of the cell
- both sets of chromosomes are pulled to opposite sides of the cell
- new nuclei are formed (or the nucleus divides)
- other organelles are also duplicated and the cell divides producing two genetically identical diploid cells
what are stem cells
cells that are not yet specialised to a function
where are stem cells found
- animal embryos
- plant meristems
- bone marrow, however those can only specialise into blood cells
diffusion
movement of particles from a high concentration to a low concentration "down the concentration gradient" this is passive as it requires no energy and can happen through semi permeable membranes
osmosis
the diffusion of water across a semi permeable membrane to balance the concentrations of solution inside and outside a cell. water must move as larger molecules cant diffuse across a semi permeable membrane, so water moves to the higher concentration to balance it
osmosis practical
- weigh and place identical cylinders from the same vegtable (potato) in sugar solutions of varying concentrations
- after set time remove excess water and re weigh , calculate :% change in mass = final mass - initial mass / initial mass ]x100
- plot % change in mass against concentration, using line of best fit the concentration at 0% change in mass is the same as that inside the vegtable
active transport
the movement of particles through a membrane via carrier proteins, this requires energy so can move against the concentration gradient
example of active transport
moving mineral ions into plant root hair cells