Cell Biology Flashcards
What are plasmids in prokaryotic cells?
They are small rings of DNA.
Why are electron microscopes better than light microscopes?
They have a higher magnification and a higher resolution
What is the formula for magnification?
Magnification = image size / real size
Explain the steps of how to prepare onion cells on a slide.
1) Cut up an onion and use tweezers to peel off some epidermal tissue from the bottom of the layer.
2) Add a drop of iodine solution. Stains are used to highlight objects in a cell by adding colour to them.
3) Place a cover slip by carefully tilting and lowering it. This gets rid of any air bubbles.
Explain the steps to view onion cells under a light microscope.
1) Clip the slide onto the stage.
2) Start with the lowest powered objective lens and use the coarse adjustment knob to move the stage up to just below the objective lens.
3) Adjust the focus with the fine adjustment knob until you get a clear image of what’s on the slide.
4) swap to a higher powered objective lens if a greater magnification is needed.
What are cells that differentiate in mature animals used for?
Repairing and replacing cells, such as skin or blood cells.
How are sperm cells specialised for reproduction?
Long tail and a streamlined head to help swim to the egg.
There are a lot of mitochondria in the cell to provide the energy needed.
Carries enzymes in its head to digest through the egg cell membrane.
How are nerve cells specialised for rapid signalling?
Long to cover more distance.
Have branched connections at the ends to connect to other nerve cells and form a network throughout the body.
How are muscle cells specialised for contraction?
Long so that they have space to contract.
Contain lots of mitochondria to generate the energy needed for contraction.
How are root hair cells specialised for absorbing water and minerals?
Large surface area for absorbing water and mineral ions from the soil.
How are phloem and xylem cells specialised for transporting substances?
Phloem – very few sub cellular structures, so that food substances can flow through them.
Xylem – hollow in the centre, so that water and mineral ions can flow through them.
What do multicellular organisms use mitosis for?
To grow or replace cells that have been damaged.
At the end of the cell cycle, what does it result in?
Two new cells identical to the original cell
What are the five stages of mitosis?
1) the cell grows and increases the amount of sub cellular structures such as mitochondria and ribosomes.
2) the DNA then duplicates and forms X-shaped chromosomes.
3) the chromosomes line up at the centre of the cell and cell fibres, pull them apart.
4) membranes, form around each of the sets of chromosomes. These become the nuclei of the two new cells.
5) lastly, the cytoplasm and cell membrane divide.
Where are stem cells found?
In early human embryos and bone marrow in adults.
