1. Cell Energy
Part 6

2. Plants and Cell Respiration
Plants use cell respiration to generate more ATP
Why does a plant need so much ATP?
Active transport
Cell division
Cell respiration requires oxygen
Roots get oxygen from the oxygen in air pockets in the soil
Drowning plants
Leaves gave plenty from photosynthesis
Leaves take in carbon dioxide
Not possible if leaves are submerged in water
Gas diffuses more slowly in water than air

3. Plant Adaptations for Cell Respiration
Conditions to grow Rice
Wet or Dry
Rice grows in “paddies”
Fields where soil is purposefully flooded
Water-tolerant plant
Weeds cannot compete b/c they are not water tolerant
Rice paddies are muddy
Contain microorganisms that use aerobic respiration and take up all available oxygen
Rice needs to adapt to survive in wet conditions

4. Rice Adaptations to Flooding
Growing taller
Top parts of leaves and flower spikes above water
Oxygen and carbon dioxide exchanged through stomata

5. Rice Adaptations to Flooding
2. Aerenchyma Tissue
Tissue in stems made of loosely packed cells
Air space AND cells of the cortex
Enable gas to diffuse through it to other parts of plant, even underwater parts
Supplemented by air trapped in between ridges of underwater leaves
Leaves Hydrophobic & corrugated
Holds thin layer of air in contact with leaf surface

6. Rice Adaptations to Flooding
3. Alcohol Fermentation
Used by cells of submerged roots
Part of the time
Ethanol= toxic to plant
Rice plants have more of the enzyme ALCOHOL DEHYDROGENASE (breaks down ethanol)
Rice plants have high tolerance for ethanol
Rice can actively grown when oxygen is scarce using ATP from Glycolysis and alcohol fermentation

8. Measuring Oxygen Uptake
Use respirometer
Measures oxygen uptake
Suitable for measuring the rate of oxygen consumption of seeds or small terrestrial invertebrates

10. We only want to measure decrease in oxygen consumption…
Carbon dioxide is produced during respiration so that will increase the gas in the chamber so….
Use chemical to absorb carbon dioxide produced
Soda-lime
Potassium-hydroxide solution
Sodium Hydroxide
Use cotton or wool to prevent contact between this chemical and organisms
Now we are only measuring decreasing in volume of oxygen in the tube (which is because of the oxygen consumption of organism)
To measure the rate of oxygen consumption, use a MANOMETER
Fluid filled scale
No air bubbles
Same quantity of fluid in both manometers (important!)

11. Other Variables to Monitor
Both of the following alter air volume in apparatus:
Changes in Temperature
Changes in Pressure
Ensure temperature is kept constant throughout use of respirometer
Use water bath maintained at stable temp (thermostatically controlled warm water bath ideal)
Use a control tube
Place in a dead organism or object of same mass (but not respiring)
Helps compensate for changes in atmospheric pressure
Subtract the distance moved in the control tube (without respiring organism) from the distance moved and recorded in the experimental manometer

12. Converting Distance Moved to Volume
Must know diameter of the capillary tube
Volume of liquid in tube = length x ∏r2
Answer will be the value for the volume of oxygen absorbed by the organism

13. Using a respirometer to investigate temperature
Place respirometers in water baths of different temperatures
2 options:
Use same respirometer throughout whole experiment
Use different respirometers during each experiment (think about variables to control)
Each temperature would require a control respirometer
Compare rates of respiration at different temperatures by simply measuring the distance the fluid moves in the manometer at various times during the experiment (this will give you the rate)

14. Using a Respirometer to Measure RQ
Two things to determine:
Oxygen consumed
Carbon Dioxide given off
Set up 2 respirometers (see figure)
First respirometer: living organism at bottom, cotton wool, carbon dioxide absorbing material (soda lime)
Second respirometer: should also contain mass of living organism but should NOT contain chemical to absorb carbon dioxide (like our previous control tubes)
Maintain a controlled experiment by putting unreactive, inert material, like glass beads, where the chemical used to be (same mass and volume of carbon dioxide absorbing material)
2nd tube identical to 1st tube minus the soda lime/carbon dioxide absorbing chemical

15. Using a Respirometer to Measure RQ
The difference between the distance moved by the manometer fluid in the experimental tube and the distance moved in the control tube is therefore due to the carbon dioxide output
When more carbon dioxide is produced than oxygen….the volume of air in the respirometer will increase (by y cm3 min-1)
If the respiratory substrate is carbohydrate:
the amount of carbon dioxide given out will equal the amount of oxygen taken in. The fluid in the control tube will not move, so y=O.

16. When Less Carbon Dioxide is Produced….
Less CO2 produced than O2 absorbed = volume of air in respirometer will decrease (by z cm3 min-1)
Calculation will be:
RQ = CO2 = x - z
O X
This will lead to a respiratory quotient LESS than 1
(possibly a lipid or protein as a substrate)

17. Alternate ways of Measuring Rate of Respiration
Use redox dye ( act as NAD or NADP)
DCPIP (dichlorophenolindophenol)
Methylene Blue
DO not damage cells
When reduced (accepting electrons and hydrogen ions), they change from blue to colorless
Rate of change from blue  colorless = rate of respiration
Use to investigate various factors influencing respiration
Temperature
Concentration
substrates