Topic 2-cell biology Flashcards
Glucose
Less dense than 1.9
nucleus: most dense
Differentiating endoplasmic reticulum
Use smaller intervals of sucrose solution as RER is more dense
Bacteria in antibiotic
-gram pos have thicker walls
-some antibiotics inhibit formation of peptidoglycan so affective in gram pos
-some can’t cross peptidoglycan layer so affective in gram neg
Electron microscope
-higher resolution
-shorter wavelength
-things not too close together
Comparing gram pos and neg
Both:
peptydoglycan
Pos:
-thicker peptidoglycan
-teichoic acid
Neg:
-outer membrane
-more lipids and lypoplysaccharide
Exposure to radiation
-only if more than 4h
-not all species tested
-toxins still remain in food
Stains
Ensure that some organelles are clearly visible
Microscopy
-locate sample using low objective lens
-focus using objective lens
-fine focus with high objective lens
Liver and pancreas comparison
-liver has less cell membrane as more organelles
-liver has less RER-less protein made
-more mitochondria as more metabolically active
Golgi apparatus
-vesicles fuse with golgi
-proteins move Golgi in vesicles
-vesicles fuse with membrane
lysosome
produce enzymes to digest old organelles
Protein synthesis
-mrna leaves through nuclear pores
-to RER ribosomes
-trna brings amino acid
-peptide bonds
-enters Golgi and modified
-exocytosis
Golgi apparatus structure
-membrane bound flattened sacks
-cisternae
Crossover
-between chromatids
-so half of the chromosomes will be recombinant
-but doesn’t always occur
Root tip squash improvements
-conc acid to separate layers of cells
-heat to intensify the effect of acid
-squash the coverslip to see individual layers of cells and prevent evaporation
-tease with needle to separate individual layers
-add stain and acid separately
Why mitotic index is different for 2 different root tips
-hard to determine the correct stage of mitosis
-variation due to chance could have an effect
Microtubulin formation
-centrioles are needed as microtublins didn’t grow without them
-concentration of tubulin is important
-conc affected rate as collision theory
-graph not linear so third factor involved
Mitosis
-DNA replication
-sister chromatids equally distributed
-so no genetic variation
Mitosis time practical
- Prepare slide like root tip
- Count the no. of cells in insert stage
- Find the proportion of cells in that stage
- Calculate time relative to 24h
Chromosomes throughout mitosis
- Chromatids join at centromere to form chromosomes
2.DNA content returns to normal at cytokinesis as cell divides into 2
Haploid and diploid
haploid-23
diploid-46
Microtubule
-shortened as they would in cell division
-shortened/broken by centriole
Colchicine
-No effect at interphase
-affects prophase and spindle formation
Importance of centrioles in sperm
-source of centriole in zygote so it make spindle fibres for mitosis
