B1 - Cells

What is 1 benefit and 1 disadvantage of light microscopes

Benefit - cheap to make

Disadvantage - only allow you to see the outline of cells

What is 1 benefit and 1 disadvantage of electron microscopes?

Benefit - allow you to see small details including organelles

Disadvantage - expensive

What is the equation to find magnification?

magnification = image size / object (actual) size

How do you convert from micrometres to milimetres?

Divide by 1000

What happens in the ribosomes?

Protein synthesis

Where is DNA found in prokaryotic cells?

In the cytoplasm as a singular strand

How many pairs of chromosomes do all human cells have (apart from gametes)

23 pairs, gametes only have 23 individual chromosomes

What are new cells made through mitosis used for?

Growth and repair

What are the six stages of mitosis?

1. Genetic material is duplicated

2. The nuclear membrane dissolves

3. The two sets of chromosomes line up along the centre of the cell

4. Both sets of chromosomes are pulled to opposite ends of the cell

5. New nuclei are formed (or ‘the nucleus divides)

6. Other organelles are also duplicated, and the cell divides, producing two genetically identical diploid cells

What is the first stage of mitosis?

Genetic material is duplicated

What is the second stage of mitosis?

The nuclear membrane dissolves

What is the third stage of mitosis?

The two sets of chromosomes line up along the centre of the cell

What is the fourth stage of mitosis?

Both sets of chromosomes are pulled to opposite ends of the cells

What is the fifth stage of mitosis?

New nuclei are formed (or ‘the nucleus divides’)

What is the sixth stage of mitosis?

Other organelles are also duplicated and the cell divides producing two gentically identical diploid cells

What is a stem cell?

A cell that can specialise to perform a specific function

Where can stem cells be found?

Animal embryos, plant meristems and bone marrow

What is special about the stem cells found in bone marrow?

They can only specialise into blood cells

What can embryo clones be used for?

Harvest stem cells to be used to treat conditions without them being rejected by the body

Or in plants can be used to preserbe species and produce crops with desired traits

Diffusion

The movement of particles from an area of high concentration to that of a lower concentration ( down the concentration gradient) this is passive and requires no energy

How can the rate of diffusion be increased?

Increasing: the difference in concentrations or surface area or concentration

Osmosis

The movement of water molecules from a solution with a high concentration to a lower concentration through a cell's partially permeable membrane

Osmosis practical (4 steps)

1. Weigh, and place identical cylinders from same vegetable in sugar solutions of varying concentrations

2. After set time, remove excess water and reweigh, then calculate the percentage change in mass

3. Plot the percentage change in mass against the concentration

4. Using a line of best fit, you can see the concentration at 0% change in mass is the same as inside the vegetavle

What is the equation to calculate percentage change in mass

% change in mass = ((final mass - initial mass) / initial mass) x100

Active transport

The movement of particles against the concentration gradient (low to high) via carrier proteins. This requires energy