Cells Flashcards
Explain the mitosis + cell cycle
[4 marks]
(stage 1)
Sub-cellular structures such as mitochondria or ribosomes increase in number,DNA is replicated, protein synthesis occurs
(stage 2)
one set of chromosomes is pulled to each end of the cell
(stage 3)
the cytoplasm and cell membrane divides to form two identical daughter cells
Explain why the rate of water loss is lower at night.
[2 marks]
-Stomata are almost completely closed
-Because it is cooler and there is no light
When placed into a beaker of water:
* a red blood cell bursts
* a plant cell does not burst.
Explain why the red blood cell bursts but the plant cell does not burst.
[2 marks]
-water enters the cells by osmosis
-plant cell has a cell wall which prevents it from bursting
Red blood cells are specialised animal cells.
Compare the structure of a red blood cell with the structure of a plant cell.
[6 marks]
DIFFERENCES:
* red blood cell has no nucleus or plant cell has a nucleus
* red blood cell has no cell wall or plant cell has a cell wall
* red blood cell is a biconcave disc or there are many different
shapes of plant cell
* red blood cell contains haemoglobin or plant cells do not contain
haemoglobin
* red blood cells do not contain chlorophyll or plant cells (may)
contain chlorophyll
* red blood cell has no chloroplasts or plant cell has chloroplasts
* red blood cell has no (permanent) vacuole or plant cell has
(permanent) vacuole
* red blood cells are (much) smaller than plant cells
SIMILARITIES:
both have:
* cytoplasm
* cell membrane
* pigments (although they are different)
Leaf mesophyll cell
Cuticle
Upper Epidermis-MOST transparent
Palisade Mesophyll
Spongy Mesophyll -large air spaces
Vein:
Lower Epidermis:
Stomata-controlled by guard cells
Which cell structure in a leaf mesophyll cell is not found in a root hair cell?
[1 mark]
Chloroplast
Explain why an axolotl may die in water with a low concentration of oxygen. [4 marks]
-concentration gradient of
oxygen is less steep
-(therefore) less oxygen diffuses into blood / cells / gills
-(so) less (aerobic) respiration occurs so less energy is released / available
or
-(so more) anaerobic respiration occurs so less energy is released / available
-(so) less metabolism
or
-(so when) anaerobic respiration occurs, lactic acid is produced (and is toxic)
If a gill of an axolotl is removed, a new gill will grow in its place.
Scientists hope to use information on how axolotls grow new gills to help with regenerating human tissue.
Name the type of cell that divides when a new gill grows.[1 mark]
Stem cells
Name one condition that could be treated using regenerated human tissue.
[1 mark]
- paralysis
- diabetes
E.I:
-Cancer
Suggest one reason why an axolotl is a suitable animal for research in the laboratory. [1 mark]
(same answer for any small animal e.g mice)
- easy to breed
- easy / cheap to keep / rear (as are small)
- don’t take up much space
An axolotl may not be a suitable animal to study when researching regeneration in human tissue.
Suggest one reason why.
[1 mark]
- it’s not a mammal or it is an amphibian
- regeneration in gills may be different to that in other organs
- metabolism / body processes are too different to humans
The body cells of a person with untreated diabetes lose more water than the body cells of a person who does not have diabetes.
Explain how diabetes can cause the body cells to lose more water.
[3 marks]
-the blood is more concentrated (than the solution
in the cells)
-(so) water moves out of cells by osmosis
-water moves through a partially permeable membrane
What is the function of stomata?
-Control water loss
-Oxygen in
-Carbon dioxide out
Why is exchange of gases in fish efficient?
-the large surface area of the gills
-the large surface area of the blood capillaries in each gill filament
-the short distance required for diffusion – the outer layer of the gill filaments and the capillary walls are just one cell thick
-the efficient ventilation of the gills with water - there is a counter current flow of water and blood
-High concentration gradient is maintained
Why is mitosis important in living organisms?
-To repair tissues
