Cells

Question 1

Isolation of cell organelles

Answer 1

Cell homogenisation to break open cells
Filter to remove whole cells
Use isotonic solution to prevent osmotic damage to organelles
Cold to prevent damage of organelles by enzymes
Buffer to prevent protein and enzyme denaturation
Centrifuge at lower speed to separate nuclei
Re-spin supernatant (after nuclei pellet removed) at higher speed
Mitochondria in pellet
Re-spin supernatant at higher speed
Ribosomes in pellet

Question 2

Electron Microscope

Answer 2

Can see organelle structure
Electrons pass through/over specimen
Denser parts absorb more electrons and appear dark
Electrons have short wavelength so give high resolution High magnification
Scanning- 3D image produced
Transmission- 2D image produced

Question 3

Limitations of Electron microscope

Answer 3

Limitations:
Cannot look at living material as in a vacuum
Specimen must be very thin
Preparation may create artefacts
Does not produce a coloured image
Complex staining method

Question 4

Diffusion

Answer 4

Movement down concentration gradient (high to low concentration)
Small, non-polar molecules pass through phospholipids
Large, polar molecules go through channel/carrier proteins – facilitated diffusion

Question 5

Osmosis

Answer 5

Water moves by osmosis from high water potential to low water potential
Through channel proteins

Question 6

Active transport

Answer 6

Movement against concentration gradient (low to high concentration)
Uses specific carrier proteins
Requires ATP

Question 7

Co-transport of glucose

Answer 7

Glucose moves into epithelium cell with sodium ion
Using a carrier protein
Sodium ions moves down concentration gradient
Sodium ions actively transported out of epithelium cell into blood
Potassium ions move in opposite direction
Maintaining low concentration of sodium ions in epithelial cell
Glucose diffuse into blood using a protein