2. Cells Flashcards
Nucleus
- chromosomes
- protein-bound, linear DNA
- one or more nucleoli
Lysosomes
Membrane-bound organelle that releases hydrolytic enzymes (‘biochemical catalysts that use water to break a chemical bond, which typically results in dividing a larger molecule into smaller molecules’)
Differences between prokaryotic and eukaryotic cells.
- X nucleus- single, circular DNA molecules free in cytoplasm, X associated w/ proteins
- Smaller ribosomes
- Lack membrane-bound organelles in cytoplasm
- Cell wall made of murein (glycoprotein)
- one or more plasmids
- one or more flagella
- capsule
Key features of viruses
- genetic material
- capsid
- attachment protein
Outline 2 main advantages of an electron microscope.
- High resolution ∵ e- short wavelength
- e- beam can be focused w/ electromagnets ∵ -ve charged
Why does a near-vacuum have to be created within the chamber of an electron microscope?
e- are absorbed/ deflected by air molecules
∴ prevents e- from reaching specimen
Explain why the homogenate was filtered before spinning at low speed in the centrifuge. (2)
- Remove debris
- Which may contaminate pellet 1
Outline the 2 types of centrifugation techniques.
- Differential centrifugation
** nuclei > mitochondria > lysosomes > ER > ribosomes
———————————————————————— - Density gradient centrifugation
- supernatant pipetted into sucrose solution
- density gradient ∵ diff. conc. of sucrose (most dilute= least dense)
- centrifuged
- organelles settle at a level in density gradient that matches w/ their own
- hole at the bottom- organelles collected in separate tubes
** cell debris > nuclei > chloroplasts > mitochondria > ribosomes
Mitotic index
No. of actively-dividing cells in field of view
______________________________________________
Total no. of cells in field of view
Describe cytokinesis of animal cell
- microfilament ring in the middle of the cell
- cleavage of cell membrane
- cytoplasm divides
Describe cytokinesis for plant cells
- cell plate forms across equator
- new cell wall is laid
What is cancer?
- uncontrolled growth of cells –> formation of tumour
- ∵ damage/ mutation to genes that regulate mitosis + cell cycle
Malignant tumours
- grow rapidly
- ↓ compact
- spread –> secondary tumours
3 main stages of cell cycle
- interphase
- nuclear division
- cytokinesis
Explain why chemotherapy drugs are not given more frequently/ higher dose.
Frequency:
- frequency ↑ healthy cells x time to ↑ no. to near normal again between treatments
- no. declines rapidly after a few treatments–> kills the patient
Dose:
- kill ↑ healthy cells each time
- no. declines rapidly
