Cell structure and Microscopy Flashcards
Why cant you identify the structures of organelles with an optical microscope [2]
- Light’s wavelength is too long
- Resolution is too low
Role of named organelle in digesting bacteria [3]
- Lysosomes
- Fuse with vessicle
- Releases hydrolytic enzymes
Two structures found in all prokaryotic and eukaryotic cells
- Cytoplasm
- DNA
- Ribosomes
- Cell surface membrane
Suggest one explanation for the faster rate of plasmid replication in cells growing in a culture with a high amino acid concentration [2]
- Amino acids are used in proteinsynthesis
- Allows more proteins responsible for DNA replication to be made
OR - Amino acids used in respiration
- More energy
Describe how a sample of chloroplasts could be isolated from leaves [4]
- Break open cells (homogenise) and filter
- In cold, isotonic, buffered solution
- Centrifuge at a low speed to remove cell debris and heavier organelles
- Centrifuge again at a higher speed to let chloroplasts settle out
Give one feature of the chloroplast that allows protein to be synthesised inside the chloroplast and describe one difference between this feature in
the chloroplast and similar features in the rest of the cell. [2]
- DNA
- Chloroplast DNA is not histone bound but nuclear DNA is
OR - Ribosomes
- Smaller than cytoplasmic ribosomes
Eukaryotic cells produce and release proteins.
Outline the role of organelles in the production, transport and release of proteins from eukaryotic cells. [4]
- DNA contains code for proteins
- Ribsomes produce proteins
- Golgi modifies and packages proteins
- Vesicle transports out of cell by fusing cell-surface membrane (exocytosis)
Give one advantage of viewing a biological specimen using a transmission
electron microscope compared with using a scanning electron microscope. [1]
- Higher resolution
OR - View internal structures
She prepared a suspension of the organelles in a solution that prevented damage to the organelles.
Describe three properties of this solution and explain how each property prevented damage to the organelles. [3]
- Isotonic - organelles aren’t damaged due to lysis or bursting
- pH buffered - stop enzymes from denaturing
- Ice cold - reduce enzyme activity
Contrast how an optical microscope and a transmission electron microscope work and contrast the limitations of their use when studying cells. [6]
- TEM uses focused beams of electrons and Optical uses light
- TEM focuses with electromagnets and Optical focuses with glass lenses
- TEM has a higher resolution than Optical as electrons have a shorter wavelength
- Can only view dead samples in a TEM and you can observe both in Optical
- Can view smaller organelles with TEM
- TEM requires thinner samples, Optical does not
- Optical shows colour, TEM does not
Give two ways in which the nucleotides in DNA are different from the nucleotides in RNA. [2]
- DNA contains thymine, RNA contains uracil
- DNA contains deoxyribose, RNA contains ribose
No organelles are visible in the cytoplasm of this red blood cell.
Suggest why. [1]
- RBC cytoplasm is filled with haemoglobin
Describe how you could make a temporary mount of a piece of plant tissue using a optical
(light) microscope. [4]
- Place droplet of water onto slide
- Obtain a thin slice of plant tissue and place onto slide
- Stain with iodine in potassium iodide
- Place a coverslip ontop using a mounted needle
