Cells and Transport

Question 1

How do we calculate surface area to volume ratio?

Answer 1

surface area / volume

Question 2

What are the units of measurment in microscopy and how do we convert between them?

Answer 2

picometre
nanometre
micrometre
milimetre
metre
kilometre
To go to a greater unit of measurment, x1000
To go to a smaller unit of measurment, /1000

Question 3

What is binary fission?

Answer 3

The process by which prokaryotic cells, such as bacteria, divide and reproduce.

Question 4

What are the two mediums that can grow cultures of microorganisms?

Answer 4

• Agar gel plate/petri dish
• Nurtient broth

Question 5

Why do we use the aseptic technique?
Outline the aspetic technique.

Answer 5

To kill any harmful microorganisms that may interfere with the culturing process.
- inoculating loops are passed through a flame
- the agar/petri dish must be stored upside down with a taped on lid
- agar or nutrient broth solution must be boiled.

Question 6

Why should a Petri dish be stored upside down before being put into an incubator?

Answer 6

To prevent condensation from forming on the lid and then dripping onto the agar, contaminating the sample.

(it is also secured using adhesive tape)

Question 7

Why is bacteria incubated at 25 degrees celcius?

Answer 7

• it decreaces the chance that harmful bacteria will grow on it as it may be colder than it’s optimum temperature.

Question 8

Outline the process to test the effect of antibiotics on bacterial growth

Answer 8

Steralisation
1. Clean the bench with disinfectant solution
2. Steralise the innoculating loop by passing it through a bunsen burner flame
3. Open a now sterile agar gel plate near a bunsen burner flame to kill the bacteria in the air surrounding it
Preparing
4. Use the loop to evenly spread the bacteria over the plate
5. Place sterile filter paper discs that contain the antibiotic onto the plate. Use 1 test paper disc containing water to eliminate placebo.
6. Use adhesive tape to secure the agar gel plate but so as to still allow oxygen to come in
6. Incubate the plate upside down at 25 degrees Celcius
Observing
7. You will obeserve that circular areas where the antibiotic was contain no bacteria - this is the zone of inhibition
8. The antibiotic responsible for the largest area in the zone of inhibition is the most effective treatment.

Question 9

Outline the process of using a light microscope to observe a prepared slide

Answer 9

1. Place the slide onto the stage and use the clips to secure it
2. Select the lowest power objective lense, and slowly turn the coarse focosing dial so as to nearly touch the slide
3. Look down through the eyepiece and now slowly turn the coarse focusing dial so as to increace the distance between the objective lense and the slide
4. Turn the fine focusing dial so as to bring the cells into a clearer focus
5. To observe smaller structures, increace the magnification of the objective lense and repeat the above process

Question 10

What is the formula for total maginification?

Answer 10

eyepiece lense x objective lense

Question 11

What is the formula for image size?

Answer 11

image size = actual size x magnification

Question 12

What is theraputic cloning?
Outline its pros and cons.

Answer 12

• The process of producing stem cells with the same genetic make-up as the patient.
• An egg cell has its nucleus removed, and the patient’s nucleus replaces it.
  Advantages
• Won’t be rejected by patient’s body as it is from the patient’s body. Therefore immunosuppresents are not needed.
• it eliminates the need for second-party surgery
  Drawbacks
• ethical issues on whether it is right to bring an embryo into the world, only to destroy it’s potential as a baby
• can pass on viruses through the genetic information

Question 13

What are the 3 stages of the cell cycle?
What are the 4 stages of the cell cycle?

Answer 13

When they say 3 stages:
- Interphase
- DNA replication
- Mitosis
When they say 4 stages
- Interphase
- DNA synthesis
- Mitosis
- Cell division

Question 14

Recite the definition of the following words:

Isotonic
Hypotonic
Hypertonic
Turgid
Flaccid

Answer 14

Isotonic - Has the same concentration of solutes than another solution
Hypotonic - The solution that is less concentrated (has less dissolved solute and more water)
Hypertonic - The solution that is more concentrated (has more dissolved solute and less water)
Turgid - Swolen and hard
Flaccid - floppy or loose

Question 15

Describe how having a large number of blood capillaries at the alveoli increases the rate of gas exchange.

(2 marks)

Answer 15

it increaces the concentration gradient (1)

of oxgen into the blood and co2 into the lungs which increaces the rate of diffusion (1)