experimental procedures - SAC 2

Question 1

photosynthesis prac: hypothesis and aim

Answer 1

hypothesis: If the light source is closer to the beaker, then the rate of the leaf disks floating will increase.

Aim: to determine how light intensity affects the rate of photosynthesis.

Question 2

photosynthesis prac: variables

Answer 2

independent: light distance or colour of light
dependent: the time taken for the disks to rise
controlled variables: type of solution, type and size of spinach leaves, sodium bicarbonate solution.

Question 3

photosynthesis prac: trend

Answer 3

• As light intensity increases, the rate of photosynthesis increases up to a point where a maximum rate is reached. This maximum is typically due to another factor (e.g.,
  temperature or carbon dioxide concentration) limiting the rate of photosynthesis.

Question 4

photosynthesis prac: limitations and errors

Answer 4

• difficult to determine actual time disks rose as measurements were taken every minute (decreases accuracy and validity)
• inconsistency between trials such as using the syringe differently (decreases repeatability and reproducibility)
• spinach leaves containing veins

Question 5

photosynthesis prac: other experiments

Answer 5

• temperature
• light intesity
• light colour
• pH

Question 6

photosynthesis prac: increasing accuracy and precision

Answer 6

• record the time each disk rises
• ## increased trials

Question 7

photosynthesis prac: repeatability and reproducibility

Answer 7

• more consistent use of the syringe

Question 8

yeasty boys: hypothesis and aim

Answer 8

hypothesis: ‘If yeast are provided with a usable substrate (sucrose) and optimal conditions (32°C water bath, absence of shampoo), then the rate of cellular respiration will be highest as measured by the greatest balloon diameter.’

aim: to determine the effect of varying food sources and conditions on the rate at which yeast respire anaerobically.

Question 9

yeasty boys: variables

Answer 9

independent: conditions and food source
dependent: rate of cellular respiration measured by the balloons diameter
controlled variables: amount of liquid, amount of yeast, the time left

Question 10

yeasty boys: trend

Question 11

yeast boys: limitations and errors

Answer 11

• it is difficult to ensure the balloons are places on each beaker at the same time

Question 12

yeasty boys: increasing accuracy and precision

Answer 12

• increased trials to reduce the risk of random errors
• using the same amount of liquid in each tube

Question 13

yeasty boys: increasing repeatability and reproducibility.

Answer 13

• improving the method of determining the balloon diameter

Question 14

to seed or not to seed: hypothesis and aim

Answer 14

hypothesis: if the temperature of the water baths increases, then the rate of aerobic cellular reparation will increase, indicated by higher carbon dioxide production and a lower pH

Question 15

to seed or not to seed: variables

Answer 15

independent: temperature of the water bath
dependent: pH of the solutions

Question 16

to seed or not to seed: trend

Answer 16

as the temperature increases, the rate of cellular respiration increases

Question 17

to seed or not to seed: limitations and errors.

Answer 17

• the subjective data collection (colour of the indicator could vary between experimenters, decreasing reproducibility)
• heat exchange between the water baths and internal environment

Question 18

to seed or not to seed: increasing accuracy and precision

Answer 18

• using more accurate equipment such as carbon dioxide sensors or a digital pH probe.

Question 19

to seed or not to seed: increasing reproducibility and repeatability.

Answer 19

• using more accurate equipment such as carbon dioxide sensors or a digital pH probe. therefore results won’t vary as much between experiments.

Question 20

anaerobic vs aerobic cellular respiration

Answer 20

similarities:
- both break glucose down to release energy

differences
- aerobic uses oxygen, anaerobic does not
- aerobic respiration releases a much higher ATP yield
- aerobic cellular respiration occurs much faster
- anaerobic only occurs in the cytosol

Question 21

advantages/disadvantages of each type

Answer 21

• aerobic respiration occurs much slower than anaerobic
• it does however produce much more ATP over.
• aerobic respiration requires oxygen, anaerobic allows for survival in low oxygen conditions