B1 - Cell Biology

Question 1

What do LIGHT MICROSCOPES do ? and How much do they COST ?

Answer 1

They Allow you to see the Outlines of Cells

Cheap to Make

Question 2

What do ELECTRON MICROSCOPES allow you to do and WHY ?

Answer 2

Allow you to Visualize Finer Details eg. Organelles

Due to their Greater Resolving Power and higher resolution

Question 3

EQUATION FOR MAGNIFICATION ?

Answer 3

Image Size / Real Size

Question 4

µm to mm

Answer 4

Dividing by 1000

Question 5

MICROSCOPY PRACTICAL

Answer 5

1. Peel a one-cell layer of onion skin using a scalpel and tweezers
2. Place this on a microscope slide Add a drop of iodine to stain the cells place a cover slip on top and place on the microscope stage
3. Turn on the light
4. Use the lowest magnification objective lens
5. Use the coarse and fine focus knobs to focus
6. Increase magnification and refocus if needed
7. A graticule on the slide can allow you to measure the length of cells in µm

Question 6

DIPLOID CELLS ARE

Answer 6

23 pairs of chromosomes

Question 7

MITOSIS PROCESS

Answer 7

1. Nucleus dissolves → genetic material is duplicated
2. The two sets of chromosomes move to different sides
3. Organelles are duplicated eg. Mitochondria , Ribosomes
4. The cell divides, producing two genetically identical diploid cells

Question 8

What can STEM CELLS SPECIALISE to do and WHERE are they found ?

Answer 8

Specialise to perform specific functions

They are found in animal embryos and plant meristems

Question 9

SOME STEMS CELLS ARE STILL

Answer 9

made in your bone marrow

These can only specialise into blood cells

Question 10

EMBRYO CLONES CAN BE MADE and USED…

Answer 10

Made of a person to harvest stem cells from
AND
Used to treat conditions without them being rejected by the patient’s body

Question 11

CLONING CAN BE USED TO

Answer 11

preserve species

produce crops with desired traits

Question 12

What is DIFFUSION ?

Answer 12

The movement of particles from an area of high concentration to that of a low concentration
( Down the concentration gradient )

It is Passive as it requires no energy

Question 13

What is OSMOSIS ?

Answer 13

The diffusion of water across a semi-permeable membrane to balance the concentrations of solution inside and outside a cell

Water must move as larger molecules cannot fit through the holes

Question 14

IF CONC IS HIGHER OUTSIDE

Answer 14

Water moves in

Question 15

RATE OF OSMOSIS/DIFFUSION IS INCREASED BY INCREASING…

Answer 15

Difference in concentrations.

Surface area.

Temperature

Question 16

OSMOSIS PRACTICAL -
INDEPENDENT V ?DEPENDENT V?
CONTROLS ?

Answer 16

Independent Variable : Concentration of Sugar Solution
Dependent Variable : Percentage Change in Mass
Controls :
Size/Shape of Cylinders
Same Vegetable
Volume of solution
Time

Question 17

OSMOSIS PRACTICAL

Answer 17

1. Cut equal size cylinders from potato and remove any skin
2. Remove excess water from surface and weigh using top-pan balance
3. Place each in a test tube with different concentrations of sugar solution and leave for a set time
4. Water will move in and out of cells due to osmosis
5. Remove cylinders, dab off excess water , reweigh and calculate : change in mass (%) = final mass - initial mass / initial mass × 100, plot this against concentration
6. Where LOBF meets x-axis : concentration in potato, as there would be no movement of water in/out

Question 18

What is ACTIVE TRANSPORT ?

Answer 18

The movement of particles through a membrane via carrier proteins.

This requires energy, and so can move them against the concentration gradient.