Supplysing The Cells Flashcards
Write down the name of the type of cell division that occurs when body cells divide.
Mitosis
A salt marsh is a large, muddy area of land where a river joins the sea.
When the tide comes in, the salt marsh gets covered with seawater.
Suggest one reason why salt marshes are difficult places for plants to grow
Due to the high concentration of salt, water is drawn out if the plants
Scientists want to use stem cells as a treatment for this condition.
Why might stem cells be able to repair the retina?
-> stem cells are not yet differentiated
-> can specialise into retina cells
This method is used:
• A petri dish is used that has the bacteria growing evenly over the surface.
• A disc of filter paper is soaked in erythromycin.
• The disc is placed on the agar in the centre of the petri dish using sterile forceps.
• The dish is incubated at 37°C.
i. Why did the scientists incubate the dish at 37°C rather than at higher or lower temperature
(2 marks)
-> any higher temperature means that the enzymes in the bacteria denature, which leads to bacteria dying
-> any lower temperature means that the erythromycin would diffuse slower
Each chip is left in a different concentration of sucrose solution for two hours.
Explain why the chip in the 0.0M solution increased in length.
-> chip had absorbed water
-> water went via osmosis form an area of high water potential to low water potential
- water went into the chip because it was more concentrated
Each chip is left in a different concentration of sucrose solution for two hours.
Explain why the chip in the 0.5M solution stayed the same length.
-> same water potential inside and outside the potato
-> No loss or gain of water
How to describe active transport
-> only occurs across a membrane
-> can move substances from high to low concentration
->uses atp
The experiment was the one where there are three cubes (Q23 in supplying the cell F)
Use the results and your calculations in parts (i) and (ii)
Explain why most single celled organisms do not need a transport system (e.g. the circulatory
system of multi cellular organisms).
-> smalles cube has fastest rate kf colour change
-> diffusion is able to take place in small organisms due to high SA to volume ratio
A plant cell is placed in a solution with a higher solute concentration than the cell contents.
What will happen to the plant cell?
Lose water and become flaccid.
Which is a function of carrier proteins in a cell membrane
Transfer molecules by active transport
Scientists are using human embryonic stem cells to grow cells to treat type 1 diabetes.
Explain why scientists use embryonic rather than adult stem cells.
-> can differentiate into more varied types of cells
-> insulin producing cells are easier to develop
At the start of the experiment starch suspension was white and surrounded by orange coloured iodine solution
At the end of the experiment the starch suspension became blue black.
Explain the results of this experiment.
Use ideas about molecules in your answer.
-> iodine molecules moved into the starch suspension bag
-> starch molecules are unable to diffuse out of the bag
-> this means that starch molecules are larger than iodine molecules
Retinitis pigmentosa is a genetic condition that affects the eyes.
It is caused by a mutation to a gene. This mutation produces a recessive allele.
The condition causes rod cells in the retina to break down.
Explain why stem cells could be used as a treatment for this condition.
-> stem cells are not yet differentiated
-> can specialise into rod cells
Katie cuts two chips from a potato.
She puts one of the chips into a test tube of distilled water.
Katie puts the other chip into an empty test tube.
Water enters the cells of the potato chip that has been left in distilled water by osmosis, Explain why
-> the potato chip absorbed water went via
-> higher concentration of solute inside potato chip than outside, meaning that water moved into the chip via osmosis
The stem cells used by the Japanese scientists were different from normal mouse stem cells.
How were these stem cells different from normal mouse stem cells?
-> mouse stem cells were made from the skin
-> Whereas the humans were made from embryos
