Cell structure Flashcards
Complete the table by giving the letter labelling the organelle that matches the function.
- L
- H
- N
Use the scale bar in the diagram above to calcualte the magnification of the drawing.
Show your working.
- 1800 - 2200
Describe and explain how centrifuging the culture allowed the scientist to obtain a cell - free liquid.
( Table shows different strains of bacteria ( A, B and C ), A and C produce a toxin and A and B have an enzyme that neutralises acid )
( A bar graph of A, B and C, A has the highest result and B has the lowest, the standard deviations of the graphs B and C cross each other in range )
- Dense cells
- Form a pellet when centrifuged
- Supernatant can be removed
The scientists measured cell damage by measuring the activity of lysosomes.
Give one function of lysosomes.
- break down cells
H. pylori cells produce an enzyme that neutralises acid.
Suggest one advantage to the H. pylori of producing this enzyme.
- to reduce them from being damaged
- by stomach acid
What do these data suggest about the damage caused to human cells by the toxin
and by the enzyme that neutralises acid?
Explain your answer.
- More cells are damaged when toxin and enzyme is produced
- Some cells are damaged by B and C
- Standard deviation doesn’t overlap for A with B and C so difference is real
The scientists carried out a further investigation.
They treated the liquid from strain A with a protein-digesting enzyme before adding it to a culture of human cells.
No cell damage was recorded.
Suggest why there was no damage to the cells.
- Neutralising enzyme is broken down
- No toxin is produced is produced
- So toxin is the protein
Describe how you could use cell fractionation to isolate chloroplasts from leaf tissue.
- Cells are broken open and debris is removed
- Solution is cold / isotonic / buffered
- Second pellet is chloroplast
The figure below shows a photograph of a chloroplast taken with an electron
microscope.
Name the parts of the chloroplast labelled A and B.
- A - Stoma
- B - Granum
Calculate the length of the chloroplast shown in the figure above.
- ( Length of chloroplast / length of bar )
- 8.3 / 1.8 = 4.6 mircro metres ( ??? )
Name two structures in a eukaryotic cell that cannot be identified using an optical
microscope.
- Ribosome
- Cell surface membrane
Starch and cellulose are two important plant polysaccharides.
The following diagram shows part of a starch molecule and part of a cellulose molecule.
Explain the difference in the structure of the starch molecule and the cellulose molecule shown in the diagram above.
- Starch is composed of alpha glucose while cellulose is composed of beta glucose
- Position of hydrogen and hydroxyl groups on carbon atom 1 is inverted
Starch molecules and cellulose molecules have different functions in plant cells.
Each molecule is adapted for its function.
Explain one way in which starch molecules are adapted for their function in plant
cells.
- Insoluble
- so doesn’t effect water potential
Explain how cellulose molecules are adapted for their function in plant cells.
- Long and straight chains
- Become linked together by many hydrogen bonds to form fibrils
- Provide strength
Silkworms secrete silk fibres, which are harvested and used to manufacture silk fabric.
Scientists have produced genetically modified (GM) silkworms that contain a gene from a spider.
The GM silkworms secrete fibres made of spider web protein (spider silk), which is
stronger than normal silk fibre protein.
The method the scientists used is shown in the figure below.
( Shows steps of how a gene from a spider is inserted into the silkworm )
Suggest why the plasmids were injected into the eggs of silkworms, rather than into
the silkworms.
- Gene gets into most cells of the silkworm
- So gets into cells that make silk
Suggest why the scientists used a marker gene and why they used the EGFP gene.
- Not all eggs will successfully take up the plasmid
- Silkworms that have taken in the gene will glow
The scientists ensured the spider gene was expressed only in cells within the silk
glands.
What would the scientists have inserted into the plasmid along with the spider gene
to ensure that the spider gene was only expressed in the silk glands of the
silkworms?
- Promoter gene
Suggest two reasons why it was important that the spider gene was expressed only
in the silk glands of the silkworms.
- So that the protein can be harvested
- Fibres in other cells might cause harm
Describe how you could make a temporary mount of a piece of plant tissue to observe
the position of starch grains in the cells when using an optical (light) microscope.
- Add a drop of water into the glass slide
- Obtain a thin section of tissue and place it on the slide
- Stain with iodine in potassium iodide
- Lower cover slip using mounted needle
The figure below shows a microscopic image of a plant cell.
Give the name and function of the structures labelled W and Z.
- W - Chloroplast
- Function - Photosynthesis
- Z - Nucleus
- Function - Contain genetic information
A transmission electron microscope was used to produce the image in the figure
above.
Explain why.
- High resolution
- Can see internal structure of the organelles
Calculate the magnification of the image shown in the figure in part (a).
- ( Length of bar in mm × 1000 )
- 14 x 1000 = 14 000
Describe how phospholipids are arranged in a plasma membrane.
- Bilayer
- Hydrophobic tails inside
- Hydrophilic heads outside
( Max 2 )
Cells that secrete enzymes contain a lot of rough endoplasmic reticulum (RER) and
a large Golgi apparatus.
Describe how the RER is involved in the production of enzymes.
- Contains ribosomes
- to make proteins
