Cells A1 Flashcards
What’s the difference between a eukaryotic and prokaryotic cell?
(give examples of both)
- eukaryotes have a nucleus (plants, algae, animal, protozoan, fungi)
- prokaryotes do not have a nucleus (bacteria, blue-green algae, archaea)
What is the function of the ribosomes?
protein synthesis (70s and 80s)
What is the function of nucleus?
- contains DNA
- controls cell activity
What is the function of the mitochondria?
- site of respiration (folder to form cristae)
- ATP production (matrix is its cytoplasm)
What is the function of smooth endoplasmic reticulum?
site of lipid synthesis
What is the function of rough endoplasmic reticulum?
- encrusted in ribosomes
- site of protein synthesis
What is the function of Golgi apparatus?
- modifies/packages/sorts proteins
- modifies/processes triglycerides
- combines triglycerides with proteins
- packages for release/forms vesicles
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 surface area
What is the function of lysosomes?
- contains digestive enzymes
- digests worn out organelles (autolysis) (phagocytes contain them)
Function of chloroplasts?
- contain thylakoids, staked into granum
- site of photosynthesis
- traps light energy and converts it to chemical energy
Function of capsule?
- protects from immune system
- aids bacteria sticking together
Function of plasmid?
- circular DNA
- contains antibiotic resistant genes
Function of cell wall?
- provides structure
- stops osmotic lysis
Function of flagellum?
allows movement / propulsion
Describe the difference between eukaryotic and prokaryotic cells.
Eukaryotic cells have:
1. DNA is linear and associated with proteins
2. contains membrane bound organelles eg.(mitochondria, Golgi apparatus, RER, SER, lysosomes)
3. Has nucleus / DNA contained within nuclear membrane
4. contains larger / 80s ribosomes
5. do not have capsule or flagella
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 prokaryote
- does not have nucleus / has free DNA in cytoplasm / has loop of DNA
3 and 4 any two from:
- no membrane bound organelles / no mitochondria / no Golgi / no ER - small ribosomes only
6 and 7 any two from
- capsule / flagellum / plasmid / cell wall etc
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 3D images
Explain the advantages and limitations of using a TEM to investigate cell structure.
advantages:
1. small objects can be seen
2. TEM has a high resolution
3. wavelength of electrons shorter
limitations:
1. cannot look at living cells
2. must be in a vacuum
3. must cut section / thin specimen
4. preparation may create artefact
Explain why a solution was made…
- isotonic
- ice cold
- buffered
isotonic - prevent osmotic (no net movement of water so organelle does not burst (lysis) or shrivel)
ice cold - reduce / prevent enzyme activity so organelles are not digested/damaged
buffered - maintain constant PH so proteins don’t denature
Describe and explain how cell fractionation can be used to isolate mitochondria from a suspension of animal cells.
Any 5 from…
1. cell homogenisation to break open cells and release organelles
2. filter to remove large debris/whole cells
3. use isotonic solution to prevent damage of mitochondria/organelles by osmosis
4. keep cold to reduce damage to organelles by enzymes
5. use buffer to maintain PH and prevent protein/enzyme denaturing
6. use differential centrifuge (at lower speed/1000g) to separate nuclei/cell fragments/heavy organelles
7. re-spin supernatant after nuclei pellet removed, at higher speed to get mitochondria pellet at bottom
8. observe pellet with microscope to identify mitochondria
List the order of organelles in a cell from densest to least dense, for cell fractionation experiment.
- nucleus (1st pellet)
- mitochondria, chloroplast (2nd pellet)
- ribosomes (3rd pellet - least dense)
What is homogenisation?
breaking apart the tissue/cell to release organelles into solution
What are microvilli?
- finger like projections
- which increase SA of a cell membrane
- found in the epithelial cells in the small intestine
What are centrioles?
- function in mitosis
- from a network of spindle fibres across the cell onto which the chromosomes attach
- these fibres pull the chromosomes/chromatids apart
- these are ONLY found in animal cells
