B1 Cell Biology

Question 1

What are the differences between light and electron microscopes?

Answer 1

Light - cheap to make, outlines of cells can be seen.
electron - see finer details including organelles. Higher resolution, resolving power.

Question 2

Equation of Magnification

Answer 2

Magnification = image size / real cell size

Question 3

how to convert from micrometres to millimetres

Answer 3

divide by 1000

Question 4

Eukaryotic cells (characteristics)

Answer 4

nucleus which stores genetic material, cell membrane (semi-permeable), cell wall, cytoplasm, mitochondria, ribosomes, chloroplasts, permanent vacuole.

Question 5

Prokaryotic cells (characteristics)

Answer 5

Plasmid (loop of DNA) stores genetic material, flagella, ribosomes, cell membrane.

Question 6

how do bacteria reproduce?

Answer 6

Binary fission - divide every 10 mins.

Question 7

how many chromosomes do humans have?

Answer 7

23 pairs (46). Chromosomes are DIPLOID.

Question 8

How many chromosomes have gametes got?

Answer 8

23 chromosomes. These are HAPLOID.

Question 9

What is mitosis?

Answer 9

Mitosis occurs for growth and repair of cells

Question 10

How does mitosis occur?

Answer 10

1. Nucleus dissolves, and genetic material is duplicated.
2. The two sets of chromosomes move to different sides.
3. Mitochondria, ribosomes and other organelles are duplicated.
4. The cell divides, producing two genetically identical diploid cells (daughter cells)

Question 11

What are examples of specialised cells?

Answer 11

muscle cells, nerve cells, root hair cells, xylem and Phloem, sperm cells.

Question 12

What are stem cells?

Answer 12

stem cells are cells which have not yet specialised for a specific function. They are found in animal embryos and plant meristems.

Question 13

where are stem cells made in humans?

Answer 13

bone marrow but these can only specialise into blood cells.

Question 14

What are embryo clones?

Answer 14

can be made of a person to harvest stem cells from. These can be used to treat conditions without them being rejected by the patient.

Question 15

What is diffusion?

Answer 15

The movement of particles from an area of high concentration to low concentration down the conc gradient. This is passive.

Question 16

What is osmosis?

Answer 16

The diffusion of water across a semi-permeable membrane to balance the concentrations of solution inside and outside a cell. Water moves in if the concentration is higher outside.

Question 17

How can diffusion and osmosis rates being altered?

Answer 17

temperature, surface area and conc gradient.

Question 18

Equation for change in mass %

Answer 18

% change in mass = final mass - initial mass / initial mass x 100

Question 19

What is active transport?

Answer 19

the movement of particles through a membrane. this requires energy and so can move against a conc gradient.