Recall Questions Flashcards
(73 cards)
Using your knowledge of cell ultrastructure, identify the structures visible in the micrograph below. State with reasons, whether the cell is a plant or animal cell.
- Cell wall (1)
- chloroplast (1)
- plant cell (1)
- presence of, chloroplast/cell wall.
Many different organisms have cell walls including fungi and bacteria. What is unique about plant cell walls?
A plant cell walls contain cellulose.
Describe the similarities and differences between an human cell and plant root cell.
- Both have three named organelles (e.g. nucleus, cell surface membrane, mitochondria, ribosomes, Golgi body, endoplasmic reticulum)
- only plants have two named organelles (e.g. chloroplasts, cell wall, large (central) vacuoles)
- centrioles present in animal cells but not flowering plants (1).
What is a lysosome and why is the membrane that surrounds it so important?
- Lysosomes are specialised vesicles that contain hydrolytic enzymes for breaking down waste material.
- The membrane that forms lysosomes has an important role in compartmentalising these enzymes away from cell structures that could be damaged by activity of the enzyme.
Explain why cells need to be compartmentalised, and describe three examples within an animal cell.
- Incompatible reactions
- catabolic and anabolic reactions require different conditions
- damage due to hydrolytic enzymes
Three named examples:
- e.g. nucleus, vesicle, lysosome, mitochondrion, Golgi body, endoplasmic reticulum, chloroplast
List 3 differences between eukaryotic and prokaryotic cells.
Prokaryotic = no membrane bound organelles, no nucleus, smaller ribosomes, murein cell wall.
What is a plasmid?
A loop of DNA not part of main chromosomal DNA e.g genes for antibiotic resistance. Not in all bacterial cells.
Why might bacterial cells have a slime capsule?
To give protection against the cells of the immune system.
What is found in the cytoplasm in prokaryotic cells?
No membrane bound organelles and has smaller ribosomes than in eukaryotic cells.
What is the flagellum?
A long hair like structure that rotates to make the prokaryotic cells move.
Not all prokaryotes have a flagellum and some have more than one.
What is circular DNA?
Long coiled up strand of DNA that is not attached to any histone proteins.
Read the information in the table and for each object, state the type of microscope it could be resolved by.
1. E. coli bacterium - 2.0 um
2. Nuclear pore - 0.05 um
3. Human egg cell - 100 um
4. DNA helix - 0.002 um
5. Mitochondrion - 0.7 um
6. Influenza virus - 0.1 um
- Light, SEM, TEM
- SEM and TEM
- Light, SEM and TEM
- SEM and TEM
- Light, SEM and TEM
- SEM and TEM
Two teams of scientists are studying HIV. HIV has a diameter of 0.12μm. Team 1 are focused on HIV surface proteins and how they bind to immune system cells. Team 2 are studying the internal structure of the virus. Suggest what specific type of microscope each team might use during their studies. Explain your answer.
- Team 1: SEM – Need to use an electron microscope to ensure high resolution. SEM provides a 3D image of surface which is what Team 1 are focused on.
- Team 2: TEM – Would allow them to view the internal structure as thin slices of the specimen can be used and a higher maximum resolution than light microscope or SEM.
A team of researchers are investigating the function of a particular set of proteins within a tissue. In a thick sample of tissue they have tagged the different types of protein with fluorescent dyes so that they can identify them.
Suggest the type of microscope that the team could use to gain an understanding of what is happening at different depths of the sample.
Explain why your suggestion is suitable.
Laser scanning confocal microscope as it uses a laser beam that would cause the dyes to give off fluorescence to show where the different proteins are located. This microscope is also suitable for thicker samples as images can be taken at different depths within the tissue sample.
What kind of radiation are used in electron microscopes?
X-rays
Describe why you would use a TEM
To study thin specimens through which electrons can generate a projected image.
Why is a stain used when preparing a slide?
To enhance visualisation of the cell, or certain cellular components under a microscope.
Why does the specimen need to be thin when preparing a slide?
In order for light coming from the light source to pass up through so that they can be viewed
What is the maximum resolution power of TEM?
0.050 mm
2 advantages of using a TEM.
- powerful microscopes
- high magnification solution
3 disadvantages of the TEM
- Limited sampling
- Complex image interpretation
- Possibility of electron beam damage
In what 2 ways is the SEM better than the TEM?
- costs less
- take less time to produce an image
which type of microscope would be used to study replication of E.coli bacteria?
- Light
- SEM
- TEM
List the 3 main stages involved in cell fractionation.
- homogenising
- filtration
- centrifuging
