Year 12 - Cells Flashcards
Describe the function of the nucleus
Stores genetic information for polypeptide production.
Site of DNA replication.
Site of production of mRNA (transcription) and tRNA.
Site of production of rRNA/ribosomes (Nucleolus)
Describe the function of the mitochondria
Site of ATP production by aerobic respiration
Describe the function of the rough endoplasmic reticulum
Synthesis and transport of proteins throughout cell.
Describe the function of the smooth endoplasmic reticulum
- Recombines glycerol and fatty acids to make triglycerides
- Packages triglycerides into vesicles and transports them to the golgi apparatus
Describe the function of ribosomes
Site of protein synthesis from amino acids
Describe the function of the golgi apparatus
- Sorts, modifies, and packages proteins and triglycerides into vesicles.
- Golgi vesicles used to form lysosomes
Describe the function of lysosomes
Contain hydrolytic enzymes that hydrolyse pathogens/damaged organelles once released into vesicles.
Describe the function of centrioles
- Form a network of spindle fibres which attach to the centromere of chromosomes.
- Pull sister chromatids apart during mitosis.
Compare and contrast structures found in a plant and animal cell.
- Cellulose cell wall vs no cell wall
- Chloroplasts vs no chloroplasts
- Large central vacuole vs no large central vacuole
- Carbohydrates stored as starch vs carbohydrates stored as glycogen
- No centrioles vs centrioles
Describe the function of chloroplasts
Site of photosynthesis
Compare and contrast chloroplasts and mitochondria
Compare:
- both have a double membrane
- both contain circular DNA
- both contain 70s ribosomes
Contrast:
- Chloroplasts have thylakoids whereas mitochondria have cristae
- Chloroplasts have stroma whereas mitochondria have matrix
- Chloroplasts have pigments (chlorophyll) whereas mitochondria have no pigments (chlorophyll)
- Chloroplasts have starch grains whereas mitochondria have no starch grains.
Define acellular
- No cell surface membrane, organelles or cytoplasm
- No metabolic reactions (eg no respiration)
Describe and explain how cell fractionation and ultracentrifugation can be used to isolate named organelle from a suspension of cells.
- Cell homogenisation to break open cells and filter to remove whole cells/debris
- Solution must be:
- Isotonic – keep water potential the same to stop organelles bursting.
- Ice cold – prevent enzyme activity
- Buffered – pH kept constant preventing enzyme denaturation. - Centrifuge at low speed to separate nuclei (densest organelles go the bottom)
- Remove supernatant containing less dense organelles
5. Re-spin supernatant at higher speeds to get mitochondria/chloroplasts in second pellet
Describe the principles of an electron microscope
- Electrons pass through / enter (very thin) specimen;
- Denser parts absorb more electrons;
- (So) denser parts appear darker;
- Electrons have short wavelength so give high resolution;
Describe the advantages/disadvantages of TEM over a light microscope
Advantages:
1. Small objects can be seen (ultrastructure’s/smaller organelles);
- TEM has higher resolution;
- Wavelength of electrons shorter;
Limitations:
4. Cannot look at living cells;
- Must be in a vacuum;
- Must cut section / thin specimen;
- Preparation may create artefacts (false image);
Describe how you could use an eyepiece graticule to determine the mean diameter of stomata
Measure using eye piece graticule
Calibrate eyepiece graticule against stage micrometre
Take a large number of repeat measurements to calculate mean
