purpose
the purpose of this lab activity is to analyze the affect of exercise on cellular
respiration.
background
cells normally contain small amounts of atp produced during the glycolysis reaction
of cellular respiration. whenever the body needs lots of energy in a hurry, its cells
quickly burn this stored atp (in about 10 seconds). after this point, the cells of the
bodys muscles are producing most of their atp by lactic acid fermentation, the slow
process by which glucose is converted to lactic acid. this process supplies around 2
atp energy molecules for approximately 90 more seconds of activity. for exercise
longer than 90 seconds, the cell has to complete two more reactions for energy.
these two reactions are called the krebs cycle and the electron transport chain.
these two reactions are the only way to generate a continuing supply of atp. this is
because the two reactions release energy much faster than glycolysis and/or lactic
acid fermentation. for the first 15 minutes of prolonged activity, your body uses
energy stored in glycogen (this is a stored form of glucose). after using the available
glycogen, the body begins to burn energy stored as fat. this is one reason why
aerobic exercise is so beneficial to weight control - it helps you burn off those extra
calories!
materials
1 beaker
2 straws
bromothymol blue solution
stop watch
pre - lab
1. what is the equation for cellular respiration? label the reactants and the
products.
2. following glycolysis, what are the 2 possible pathways for respiration depending
on the presence of absence of oxygen?
3. in what part(s) of the cell does cellular respiration occur?
4. after which reaction in aerobic respiration is co₂ released?
5. if you continued to run for longer than a couple of minutes, you would eventually
start to sweat. which reaction of cellular respiration is responsible for releasing
h₂o which produces sweat?

Question

Accepted Answer

### Question 1
# Brief Explanations:
The equation for cellular respiration (aerobic) is $ \ce{C6H12O6 + 6O2 -> 6CO2 + 6H2O + ATP} $. Reactants are glucose ($ \ce{C6H12O6} $) and oxygen ($ \ce{O2} $); products are carbon dioxide ($ \ce{CO2} $), water ($ \ce{H2O} $), and ATP (energy).
# Answer:
Equation: $ \boldsymbol{\ce{C6H12O6 + 6O2 -> 6CO2 + 6H2O + ATP}} $; Reactants: Glucose ($ \ce{C6H12O6} $) and Oxygen ($ \ce{O2} $); Products: Carbon Dioxide ($ \ce{CO2} $), Water ($ \ce{H2O} $), and ATP

### Question 2
# Brief Explanations:
After glycolysis, if oxygen is present, the pathway is **aerobic respiration** (Krebs Cycle + Electron Transport Chain). If oxygen is absent, the pathway is **anaerobic respiration (fermentation)**, like lactic acid fermentation (in muscle cells) or alcoholic fermentation (in yeast).
# Answer:
1. Aerobic Respiration (with $ \ce{O2} $): Krebs Cycle + Electron Transport Chain
2. Anaerobic Respiration (without $ \ce{O2} $): Fermentation (e.g., Lactic Acid Fermentation)

### Question 3
# Brief Explanations:
- **Glycolysis**: Occurs in the **cytoplasm** (cytosol).
- **Krebs Cycle (Citric Acid Cycle)**: Occurs in the **mitochondrial matrix** (of mitochondria).
- **Electron Transport Chain (ETC)**: Occurs in the **inner mitochondrial membrane** (of mitochondria).
So cellular respiration occurs in the cytoplasm and mitochondria.
# Answer:
- Glycolysis: Cytoplasm (cytosol)
- Krebs Cycle: Mitochondrial matrix (mitochondria)
- Electron Transport Chain: Inner mitochondrial membrane (mitochondria)
Overall, cellular respiration occurs in the **cytoplasm** and **mitochondria**.

### Question 4
# Brief Explanations:
In aerobic respiration, $ \ce{CO2} $ is released during the **Krebs Cycle (Citric Acid Cycle)**. During this cycle, acetyl - CoA (from pyruvate oxidation) is broken down, and carbon atoms are released as $ \ce{CO2} $.
# Answer:
$ \ce{CO2} $ is released after the **Krebs Cycle (Citric Acid Cycle)** in aerobic respiration.

### Question 5
# Brief Explanations:
In the **Electron Transport Chain (ETC)** of aerobic respiration, oxygen acts as the final electron acceptor. As electrons pass through the ETC, protons are pumped across the inner mitochondrial membrane, and when protons flow back through ATP synthase, water ($ \ce{H2O} $) is formed as a by - product (from the combination of electrons, protons, and oxygen). This water can be released as sweat during prolonged exercise.
# Answer:
The **Electron Transport Chain (ETC)** of cellular respiration is responsible for releasing $ \ce{H2O} $ (which contributes to sweat).

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