cells - key points Flashcards
(30 cards)
what is the function of the ribosomes
site of protein synthesis
what is the function of the nucleus
- contains genetic material/DNA
- controls cell activity
what is the function of the mitochondria
- site of aerobic respiration
- ATP production
what is the function of the rough endoplasmic reticulum
- encrusted in ribosomes
- site of protein synthesis
- transports and stores proteins within the cell
what is the function of the smooth endoplasmic reticulum
site of lipid synthesis
what is the function of the cell surface membrane
- made of phospholipid bilayer
- controls what enters the cell/is selectively permeable
- can be folded to increase SA
what is the function of the chloroplast
- contain thylakoids, stacked into granum
- site of photosynthesis
what is the function of capsule
- protects cell from immune system
- aids bacteria sticking together
what is the function of plasmid
- circular DNA
- contains antibiotic resistance genes
what is the function of the cell wall
- provides rigid shape/structure
- stops osmotic lysis
what is the function of flagellum
allows movement/propulsion
Eukaryotic cells produce and release proteins. Outline the role of organelles in the production, transport and release of proteins from eukaryotic cells.
- DNA in nucleus codes for protein
- Ribosomes/RER produce protein
- Mitochondria produce ATP for protein synthesis
4 Golgi apparatus package/modify proteins
5 Vesicles transport OR RER transports - Vesicles fuse with cell-surface membrane
Compare and contrast Eukaryotic and Prokaryotic DNA
Comparisons
1. Nucleotide structure is identical
2. Nucleotides joined by phosphodiester bond
3. DNA in mitochondria/chloroplasts similar to DNA in prokaryotes
Contrasts
4. Eukaryotic DNA is longer
5. Eukaryotic DNA contain introns, prokaryotic DNA does not
6. Eukaryotic DNA is linear, prokaryotic DNA is circular
7. Eukaryotic DNA is associated with histones, prokaryotic DNA is not
State three differences between DNA in the nucleus of a plant cell and DNA in a prokaryotic cell.
Plant v prokaryote
1. Associated with histones v no histones
2. Linear v circular
3. No plasmids v plasmids
4. Introns v no introns
5. Longer v shorter
The structure of a cholera bacterium is different from the structure of an epithelial cell from the small intestine. Describe how the structure of a cholera bacterium is different
- Cholera bacterium is prokaryotic
- Does not have a nucleus/ nuclear envelope / has DNA free in cytoplasm/has loop of DNA;
3 and 4 Any two from: [No membrane-bound organelles / no mitochondria / no golgi / no endoplasmic reticulum]
5 70s ribosomes only
6 and 7 Any two from [Capsule / flagellum / plasmid / cell wall]
Give three advantages of using a TEM rather than a SEM.
- Higher resolution;
- higher magnification / higher detail
OR - Allows internal structures within cells to be seen
Give one advantage of using a SEM rather than a TEM.
Thin sections do not need to be prepared / shows surface of specimen / can have 3-D images;
Scientists use optical microscopes and transmission electron microscopes to investigate cell structure. Explain the advantages and limitations of using a TEM to investigate cell structure.
Advantages:
1 Small objects can be seen;
2 TEM has high resolution;
3 Electron wavelength is shorter;
Limitations:
4 Cannot look at living cells;
5 Must be in a vacuum;
6 Must cut section / thin specimen;
7 Preparation may create artefact;
Scientists isolated mitochondria from liver cells. They broke the cells open in an ice-cold, buffered isotonic solution. Explain why the solution was:
a) Isotonic
b) Ice cold
c) buffered
a) Prevents osmosis so organelle does not burst
b) Reduce/prevent enzyme activity so organelles are not damaged
c) Maintains constant pH so proteins do not denature
Describe and explain how cell fractionation and centrifugation can be used to isolate mitochondria from a suspension of animal cells.
- Cell homogenisation to break open cells and release organelles;
- Filter to remove debris/whole cells;
- Use isotonic solution to prevent osmotic damage to organelles;
- Keep cold to prevent damage to organelles by enzyme;
- Use buffer to maintain pH and prevent protein denaturation;
- Use differential Centrifuge (at high speed) to separate nuclei;
- Re-spin (after nuclei pellet removed) at higher speed to get mitochondria in pellet;
- Observe pellet with a microscope to identify mitochondria;
Name 2 structures found within a eukaryotic cell that cannot be identified using an optical microscope
(any 2 from)
mitochondrion
ribosome
SER
RER
lysosome
cell-surface membrane
A student viewed impressions of stomata using an optical microscope. She then determined the mean diameter of the stomata.
Describe how the student could have used an eyepiece graticule to determine the mean diameter of stomata (3)
- Measure each stomata using an eyepiece graticule
- Calibrate the eyepiece graticule against a stage micrometer
- Take at least 5 measurements and calculate a mean
A student viewed impressions of stomata using an optical microscope. She then determined the mean diameter of the stomata.
Describe how the student could have used an eyepiece graticule to determine the mean diameter of stomata (3)
- Measure each stomata using an eyepiece graticule
- Calibrate the eyepiece graticule against a stage micrometer
- Take at least 5 measurements and calculate a mean
Describe the principles of using a TEM to investigate cell structure
- Electrons pass through specimen
- Denser parts absorb more electrons
- Denser parts appear darker
- Electrons have short wavelength so give high resolution
