2-A: Cell Structure And Division Flashcards
(17 cards)
Describe cell fractionation
- homogenisation
- filtration
- ultracentrifugation
- supernatent, pellet
- nuclei, chloroplasts, mitochondria, lysosomes, ER, ribosomes
- ice (reduce enzyme activity)
Describe the structure of a chloroplast.
Bound by a double membrane and filled with grana, which are stacks of thylakoid membranes and linked by lamellae
Describe the structure of prokaryotic cells (bacteria)
- circular free floating DNA
- plasmids (sometimes)
- ribosomes (70s)
- flagellum (sometimes)
- capsule (sometimes)
- cell wall (murein)
What are fungal cell walls made of?
Chitin
How do you prepare a microscope slide?
- drop of water (temporary mount)
- tweezers to place specimen
- drop of stain
Cover slip: upright then carefully tilt to avoid air bubbles
Describe the stages of mitosis: IPMAT
I: DNA unravels and copies, organelles copy, ATP imcreases
P: chromosomes condense, centrioles move to poles forming spindle, nuclear envelope breaks down
M: equator, centromeres attach to spindle
A: centromeres divide, spindle fibres contract, pull to poles
T: chromatids uncoil= chromosomes again, nuclear envelope, cytokinesis
Describe interphase
G1: cell grows, new organelles/ proteins made
S: DNA replication
G2: cell growth and division proteins are made
Root tip cell squash practical
- cut root tip from growing end (auxin)
- place root tip in 1M HCl, 5 minutes
- tweeze out of tube, rinse in cold water, dry on paper towel
- cut 2mm from very tip of root
Place on slide - use mounted needle to break tip and spread cells/ squash
- stain, leave for few minutes
- cover slip- thin enough
- view
Describe how you would use an optical microscope to view a slide
- clip slide onto stage
- select lowest objective lense
- course focus to bring stage high
- look down eyepiece
- course to lower stage until rough focus
- Fine focus
- increase objective lense and refocus
How do you calculate mitotic index?
No. cells with visible chromosomes/
Total cells observed
How do you calculate the actual size of cells ( technical)
- line up eyepiece graticule (in eyepiece, no units) and stage micrometer (on stage with scale, o.1mm)
- 0.1 (SM divisions)/ no. Graticule divisions
- count no. Divisions for cells, x by previous no.
Why can optical microscopes not view sub cellular organelles?
Resolution is too low because wavelength of light is too long
What are the 3 conditions needed to keep homogenate?
- ice cold: reduce enzyme activity
- buffered: prevent proteins denaturing
- same WP: prevent organelles lysis
Advantages/ disadvantages of TEM
- greater res
- smaller organelles can be observed
- dead due to vacuum
- no colour
-thinner specimens - complex prep
- uses electrons beams and focusing magnets
- TEM and optical use light
Describe 3 ways to count cells for the notification index accurately
- examine large field of view to ensure representative sample
- repeat count to ensure figures are correct
- count only whole cells to standardise counting
What are homologous chromosomes?
Two chromosomes that carry the same genes
Describe how chromosomes change during mitosis
- prophase: condense, appear as 2 sister chromatids
- metaphase: line up at equator, attached to spindal fibres at their centromeres
- anaphase: centromere splits, chromatids/ chromosomes are pulled to opposite poles
- telophase: chromatids/chromosomes lengthen and thin
