Cells Flashcards
What are the differences between eukaryotic cells and prokaryotic cells
.Eukaryotes have no membrane bound organelles
.Smaller ribosomes in prokaryotes
.Prokaryotes have an unbound loop of DNA
Describe the function of ribosomes
The site where proteins are synthesised in the cell.
Describe the function of mitochondria
Produce ATP ( adenosine triphosphate ) for respiration etc.
Describe the function of both variations of ER
Rough: folds and processes proteins that have been made by the ribosomes.
Smooth: synthesises and processes lipids.
Name the constituents of the nucleus of a cell
Nuclear envelope
Nucleolus
Chromatin
Name the organelle that contains digestive enzymes that hydrolyse invading cells or worn out components of the cell.
Lysosomes
Describe the function of Golgi and how it transports substances.
Processes and packages lipids and proteins which are transported elsewhere by vesicles.
Describe how epithelial cells are adapted for their function.
Large surface area which means greater diffusion of molecules into the cell due to villi that line the surface of the cell.
Large quantities of mitochondria due to high levels of respiration which requires ATP.
Villi have cells on them called micro villi to further increase the surface area.
How are red blood cells adapted for transporting oxygen?
No nucleus so more space to bind oxygen
What adaptation do sperm cells have in terms of transporting themselves?
They contain large amounts of mitochondria which produces ATP so the sperm cell can manouvre and propel its way through the female reproductive organs.
How do you calculate magnification?
Magnification=length of image/length of actual specimen
Name the three types of microscope
Light microscope
Transmission electron microscope
Scanning electron microscope
Name the benefits for each type of microscope
Light: specimen image is in colour and if small enough can be live too.
TEM: higher resolution than the other microscopes
SEM: 3-D imaging
How does a TEM work?
A beam of electrons is fired at the specimen using electromagnets to focus the beam. Denser parts of the specimen produce a darker image as they absorb more of the electrons. The image can then be viewed by a computer. Unfortunately it has to be done in a vacuum so no live specimens and it only works with a thin sample.
How does a SEM work?
In a similar way to the TEM, the SEM scans the specimen using electrons to knock the electrons of the specimen. These are then received by a cathode ray to produce an image ( usually 3-D ). They are good for thick specimens but render lower resolution images and the specimen still can’t be alive.
Describe homogenisation in cell fractionisation
Homogenisation: brakes up the cells in a very cold isotonic solution. Can be done by a vibrating the cells or in a blender to break down the plasma membrane to release the organelles into the solution. Has to be kept cold to reduce enzyme activity Which would break the organelles down. The isotonic solution stops organelles from shrinking or bursting as it has the same concentration of chemicals as the organelles.
Describe filtration in cell fractionation
The homogenised solution is filtered through a gauze to separate large cell debris or tissue debris from the organelles. The organelles are small enough to pass through the gauze.
describe ultracentrifugation in cell fractionation
The cell fragments that were collected from filtration are poured into a tube which is placed in the centrifuged and spun at different speeds. Lower speeds separate out the heavier organelles like the nucleus and mitochondria and faster speeds separate out the smaller organelles like ribosomes.
When each organelle is separated out the rest of the organelles are suspended in a liquid above the pellet known as the supernatant. This poured into another tube and then centrifuges again until all the organelles are separated out.
