Cell Structure

Question 1

Describe how you would use cell fractionation and ultracentrifugation to obtain a sample of mitochondria from muscle tissue [4]

Answer 1

.use cold ,buffered solution with same water potential
.Homogenise tissue+ then filter
.Centrifuge spun at LOW SPEED to remove supernatant
.Supernatant re-spun at higher speed to pellet increasingly lighter organelles

Question 2

Why is it important that the piece of leaf tissue observed was very thin under an optical microscope. [2]

Answer 2

.few layers of cells/tissue
.so light can penetrate through leaf tissue sample

Question 3

Describe ways a student could ensure they produce a correct biological drawing of the leaf tissue

Answer 3

.draw to same scale
.do not shade in organelles
.use continuous lines
.do not use sketching
.draw only outline of tissues
.show labels/annotations/titles
.show magnification

Question 4

Describe and explain how you would use cell fractionation and ultracentrifugation to obtain a sample of nuclei from muscle tissue [6]

Answer 4

.homogenise tissue-break open cells-
.filter-remove tissue/cells
cold solution-prevent enzyme activity
.solution with equivalent water potential-prevent osmosis
buffered solution-stop enzymes denaturing
.centrifuge spun at LOW SPEED

Question 5

Describe the role of organelles in the production and release of enzymes by animal cells [5]

Answer 5

.DNA in nucleus codes for protein/enzyme production
.ribosomes produce enzyme/protein
.RER transports/modifies/processes enzymes/protein
.Mitochondria produce ATP
.Golgi apparatus modifies/processes/packages/transport enzymes/protein
.Vesicles move protein to cell-surface membrane

Question 6

.Describe the structure of ATP
.Outline how named enzymes break down and resynthesise ATP [4]

Answer 6

.Consists of 3 phosphates, adenine and ribose
.ATP synthase turns ADP to ATP
ATP hydrolase turns ATP to ADP
.In a condensation reaction