Worksheet on cellular respiration and cell energy, featuring questions and a diagram of the process.

Worksheet: Cellular Respiration & Cell Energy

#### Directions: Answer the following questions using your class notes and textbook.

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1. What is a calorie?

A calorie is a unit of energy. Specifically, it is the amount of energy required to raise the temperature of 1 gram of water by 1 degree Celsius. In biological contexts, calories are often used to measure the energy content of food or the energy released during cellular processes like cellular respiration.

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2. How many calories make up 1 Calorie?

In nutritional contexts, the term "Calorie" (with a capital "C") refers to a kilocalorie (kcal). Therefore:
- 1 Calorie = 1000 calories.

This distinction is important because food labels typically use Calories (kcal) to indicate the energy content of food.

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3. Cellular respiration begins with a pathway called _________.

Cellular respiration begins with a pathway called glycolysis. Glycolysis is the first stage of cellular respiration, where glucose is broken down into pyruvic acid in the cytoplasm of the cell.

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4. Is the following sentence true or false? Glycolysis releases a great amount of energy.

False.

Glycolysis releases only a small amount of energy. During glycolysis, one molecule of glucose is broken down into two molecules of pyruvic acid, producing a net gain of 2 ATP molecules. While this is the start of cellular respiration, most of the energy from glucose is not released until later stages, such as the Krebs cycle and electron transport chain.

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5. What is cellular respiration?

Cellular respiration is the process by which cells convert glucose and oxygen into energy in the form of adenosine triphosphate (ATP). It is an aerobic process that occurs in the presence of oxygen and involves three main stages: glycolysis, the Krebs cycle (also known as the citric acid cycle), and the electron transport chain. The overall purpose of cellular respiration is to harvest energy stored in glucose and other organic molecules to produce ATP, which powers cellular activities.

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6. What is the equation for cellular respiration, using chemical formulas?

The general equation for cellular respiration is:

\[
\text{Glucose} + \text{Oxygen} \rightarrow \text{Carbon Dioxide} + \text{Water} + \text{Energy (ATP)}
\]

Using chemical formulas:

\[
\text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \rightarrow 6\text{CO}_2 + 6\text{H}_2\text{O} + \text{Energy (ATP)}
\]

This equation shows that glucose (\(\text{C}_6\text{H}_{12}\text{O}_6\)) reacts with oxygen (\(\text{O}_2\)) to produce carbon dioxide (\(\text{CO}_2\)), water (\(\text{H}_2\text{O}\)), and energy in the form of ATP.

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7. Label the three main stages of cellular respiration on the illustration of the complete process.

The diagram provided shows the three main stages of cellular respiration:

1. Glycolysis: Occurs in the cytoplasm. Glucose is broken down into pyruvic acid.
2. Krebs Cycle (Citric Acid Cycle): Occurs in the mitochondrial matrix. Pyruvic acid is further broken down, releasing electrons carried by NADH and FADH₂.
3. Electron Transport Chain: Occurs in the inner mitochondrial membrane. Electrons from NADH and FADH₂ are passed through a series of protein complexes, generating a proton gradient that drives ATP synthesis via oxidative phosphorylation.

Labeling the diagram:
- The box labeled "Glucose" represents the starting point of glycolysis.
- The box labeled "Pyruvic acid" represents the product of glycolysis.
- The box labeled "Mitochondrion" represents the location of the Krebs cycle and electron transport chain.

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8. Where does glycolysis take place?

Glycolysis takes place in the cytoplasm of the cell. This is the first stage of cellular respiration, where glucose is broken down into pyruvic acid without requiring oxygen.

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9. Where do the Krebs cycle and electron transport take place?

- The Krebs cycle takes place in the mitochondrial matrix. This is where pyruvic acid is further broken down, releasing electrons that are carried by NADH and FADH₂.
- The electron transport chain takes place in the inner mitochondrial membrane. Here, the electrons from NADH and FADH₂ are used to generate a proton gradient, which drives ATP synthesis through oxidative phosphorylation.

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Final Answers:

1. A calorie is the amount of energy required to raise the temperature of 1 gram of water by 1 degree Celsius.
2. 1 Calorie = 1000 calories.
3. Glycolysis.
4. False.
5. Cellular respiration is the process by which cells convert glucose and oxygen into energy in the form of ATP.
6. \(\text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \rightarrow 6\text{CO}_2 + 6\text{H}_2\text{O} + \text{Energy (ATP)}\).
7. Label the diagram as follows:
- First box: Glycolysis (Cytoplasm)
- Second box: Krebs Cycle (Mitochondrial Matrix)
- Third box: Electron Transport Chain (Inner Mitochondrial Membrane)
8. Glycolysis takes place in the cytoplasm.
9. The Krebs cycle takes place in the mitochondrial matrix, and the electron transport chain takes place in the inner mitochondrial membrane.

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Final Boxed Answers:

\[
\boxed{
\begin{aligned}
1. & \text{ A calorie is the amount of energy required to raise the temperature of 1 gram of water by 1 degree Celsius.} \\
2. & \text{ 1 Calorie = 1000 calories.} \\
3. & \text{ Glycolysis.} \\
4. & \text{ False.} \\
5. & \text{ Cellular respiration is the process by which cells convert glucose and oxygen into energy in the form of ATP.} \\
6. & \text{ C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \rightarrow 6\text{CO}_2 + 6\text{H}_2\text{O} + \text{Energy (ATP)}. \\
7. & \text{ Label the diagram as follows:} \\
& \text{ - First box: Glycolysis (Cytoplasm)} \\
& \text{ - Second box: Krebs Cycle (Mitochondrial Matrix)} \\
& \text{ - Third box: Electron Transport Chain (Inner Mitochondrial Membrane)} \\
8. & \text{ Glycolysis takes place in the cytoplasm.} \\
9. & \text{ The Krebs cycle takes place in the mitochondrial matrix, and the electron transport chain takes place in the inner mitochondrial membrane.}
\end{aligned}
}
\]