Cells

Question 1

Cell Theory

Answer 1

1. all organisms consist of one or more cells
2. the cell is the basic unit of organisms
3. all cells arise from pre-existing cells

Question 2

Sub-Cellular fractionation purpose

Answer 2

isolation and purification of cellular organelles and macromolecules using centrifugation  if you want to study a certain part of cells, like mitochondria

Question 3

Sub-Cellular fractionation principle/how it works

Answer 3

when particle is subjected to centrifugal force, rate of movement of the particle though a specific solution depends on its size and density as well as solution’s density and viscosity

Question 4

sedimentation rate

Answer 4

rate of movement through the solution  large and dense = higher rate

Question 5

ultracentrifuge

Answer 5

100 000 rpm and up to 60 000 g

Question 6

sub cellular fractionation: combination of steps

Answer 6

Homogenization (4 ways) >Isolation (1 way) > Purification (2 ways

Question 7

homogenization

Answer 7

aka disruption: breaks plasma membrane to release cell contents without destroying them. leaves most of the membrane enclose organelles intact and results in a homogenate: suspension of organelles

Question 8

four ways of homogenization

Answer 8

Break cells with high frequency sound/Use mild detergent to make holes in plasma membrane/Force cells through a small hole using high pressure/Shear cells between a close fitting rotating plunger and thick walls of a glass vessel

Question 9

isolation (sub cellular fractionation)

Answer 9

Differential centrifugation: separates cell components according to whether they sediment or not - based on size/density

Question 10

Two layers after isolation

Answer 10

Top: supernantant – smaller and less dense components sediment slowly. Bottom: pellet – larger and more dense components sediment rapidly

Question 11

Different speeds of centrifugation

Answer 11

Low: 1000g 10 mins -Whole cells, nuclei, cytoskeletons. Medium: 20 000g, 20 min -mitochondria, lysosomes, peroxisomes
High: 80 000g, 60 min - microsomes, other small vesicles. Very High: 200 000g, 120 min - ribosomes, viruses, large macromolecules

Question 12

purification: two methods

Answer 12

velocity or equilibrium centrifugation

Question 13

Velocity Centrifugation

Answer 13

purifies cell components according to sedimentation rate - top is slow, bottom is fast

Question 14

Equilibrium Centrifugation

Answer 14

purifies cell components according to buoyant density - top is low density, bottom is high