Biology 121 Lab
Biology 121 Lab. 1. A. Briefly, outline the main steps of the photosynthetic pathway. Be sure to indicate how the light-dependent and light-independent reactions are coupled.
B. Why is Chlorophyll-a central to the light-dependent reactions? AND – What important role(s) do accessory pigments play in this process?
2. Consider last week’s laboratory exercise concerning carbon-fixation in an aquatic plant. Recall, we used BTB to monitor pH of the surrounding medium as a proxy for CO2 concentration. Why might we expect to see a DECREASE in pH in the plant/dark tube? (i.e., What metabolic process might contribute to this result?)
3. If a farm pond, stocked with fish and plants, were measured for pH at sunrise and sunset what would be the results? Why?
4. Describe the redox reaction that was the subject of the “Hill reaction”. What is normally the final electron acceptor and what did we use as a substitute? Why did we use what we used?
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Order Paper NowCELLULAR RESPIRATION
What is CELLULAR respiration?
chemical E (glucose) + O2 → “biochemical currency” (ATP)
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + E
Oxygen (O2) is ESSENTIAL for AEROBIC respiration…
4 main steps…1 is common to both aerobic AND anaerobic respiratory pathways…
Aerobic vs. Anaerobic Respiration
Aerobic requires O2 4 main steps yields up to 38 ATP glucose-1 obligate aerobes, facultative anaerobes
Anaerobic NO O2 required 1 main step yields 2 ATP glucose-1 obligate anaerobes
The Mitochondrion
• Glucose is broken down in the cytoplasm • Kreb’s Cycle occurs in the matrix • Electron transport occurs in/on the cristae
(envelope)
Aerobic Respiration
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + E
Step 1: Glycolysis (“glyco” “lysis”; cytoplasm)*
glucose → 2 pyruvate + 2 ATP + 2 NADH2 (6C) (3C)
cytoplasm
glycolysis
Step 2: Pyruvate Oxidation (mito matrix)
2 pyruvate → 2 Acetyl CoA + 2 CO2 + 2 NADH2 (3C) (2C)
pyruvate oxidation
matrix
Step 3: Kreb’s Cycle (aka TCA Cycle or Citric Acid Cycle; mito matrix)
2 Acetyl CoA + 2 Oxaloacetic Acid (2C) (4C)
2 Citric Acid + 4 CO2 + 2 ATP + 6 NADH2 + 2 FADH2 (6C)
Kreb’s Cycle
matrix
Step 4: Oxidative Phosphorylation (aka e- transport; mito cristae)
NADH2 + FADH2 are involved with e – transport
donate e- to carriers in the transport chain pumping of H+ ions → [ ] gradient generation of ATP
O2 is the final e- acceptor oxidative phosphorylation
cristae
out
in
mito matrix
intermembrane space
NADH2 & FADH2
ATP synthase
Summary 3 ATP per NADH2 (x 10) (= 30; steps 1-3) 2 ATP per FADH2 (x 2) (= 4; step 3) 4 “substrate-level” ATP (= 4; steps 1 & 3)
38 TOTAL glucose-1
Theoretical maximum = 38 ATP…no system is perfect!
∴ this number is rarely [if ever] achieved…
Anaerobic Respiration
glucose → 2 pyruvate + 2 ATP + 2 NADH2 (6C) (3C)
2 lactate 2 ethanol + 2 CO2 (= fermentation) (3C) (2C)
– animals – plants – microbes – microbes
demand > O2 release of metabolic poison
5.1 Respiration in Peas Protocol 5.1: Germinating vs. Non-germinating
⇒ Atmospheric/background CO2 level = 350-400 ppm
1. Obtain 25 germinating peas & blot dry 2. Place the peas in the respiration chamber 3. Place the CO2 sensor in the chamber 4. Wait 1 minute → begin collecting data for 5 minutes 5. Measure & record the weight (g) of the peas 6. Place the germinating peas in a beaker and place on ice for 5 minutes 7. Follow the instructions on pg. 4
determine the rate of respiration (slope, m = rate; ppm CO2 min-1) store the data for comparison with other measurements
15. Rinse and dry chamber 16. Place the CO2 sensor in the chamber with non-germinating peas 17. Wait 1 minute → begin collecting data for 5 minutes 18. Follow the instructions on pg. 4
Use a notebook to “fan” (i.e., clear) the sensor for 1 minute, returning the CO2 level to 300-400 ppm between EACH measurement!
5.2 Respiration in Peas Protocol 5.2: Room vs. Cold Temperature
1. Empty the chamber by PUTTING THE NON-
GERMINATING PEAS BACK ON THE SIDE BENCH, and “clear” it…
2. Rinse and dry chamber
3. Repeat steps 1-7 (Protocol 5.1) using COLD germinating peas
5.3 Respiration in Crickets Protocol 5.3: Room vs. Cold Temperature
1. Obtain 5-8 crickets & place in the respiration chamber 2. Place the CO2 sensor in the chamber 3. Wait 1 minute → begin collecting data for 5 minutes 4. Measure & record the weight (g) of the crickets 5. Place the crickets in the chamber on ice for 5 minutes (or until static) 6. Follow the instructions on pg. 4
determine the rate of respiration (slope, m = rate; ppm CO2 min-1) store the data for comparison with other measurements
7. Repeat steps 1-6 using COLD crickets 8. Rinse & dry the respiration chamber when finished
Use a notebook to “fan” (i.e., clear) the sensor for 1 minute, returning the CO2 level to 300-400 ppm between EACH measurement!
Do the results support your predictions? Peas Germinating vs. Non-Germinating
germinating > non-germinating WHY?
Room vs. Cold Temperature room > cold WHY?
Germinating
Germinating/COLD
Non-germinating
Do the results support your predictions?
Crickets Room vs. Cold Temperature
room > cold WHY?
What about PEAS vs. CRICKETS?? Why is it important to “normalize” by some
biological parameter (= fresh weight) for comparison?
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