Cellular Respiration: Basic Vocabulary & Key Equations

Part 1 of Key Concepts

What is an Autotroph (or Producer)?

An organism that produces its own food, usually through photosynthesis using the sun's energy (e.g., plants, some bacteria).

What is a Heterotroph (or Consumer)?

An organism that cannot produce its own food and must consume other organisms to get energy (e.g., animals, fungi).

Define Photosynthesis.

The process by which plants use sunlight, water, and carbon dioxide to create oxygen and energy in the form of sugar (glucose).

Define Cellular Respiration.

The metabolic process in all living organisms where glucose is broken down to produce ATP (usable energy) and carbon dioxide.

What is ATP?

Adenosine Triphosphate; the molecule that stores energy for the cell to use for processes like growth and reproduction. It is often called the "energy currency" of the cell.

What is a Pigment?

A molecule that absorbs some wavelengths of light and reflects others; they are used to capture light energy for photosynthesis.

What is Chlorophyll?

The primary green pigment found in chloroplasts that absorbs light energy for photosynthesis.

What are Stomata?

Pores located on the underside of a leaf that allow for gas exchange (Carbon Dioxide enters, Oxygen and water vapor exit).

What is the function of Guard Cells?

Cells surrounding the stomata that swell with water to open the pore or shrink to close it, regulating gas exchange.

What is Aerobic Respiration?

A form of cellular respiration that REQUIRES OXYGEN to break down sugars to make ATP.

What is Anaerobic Respiration (Fermentation)?

A form of cellular respiration that DOES NOT REQUIRE OXYGEN to break down sugars.

What is Lactic Acid Fermentation?

An anaerobic process occurring in bacteria and animal muscles (during strenuous exercise) that produces lactate and causes muscle cramps.

What is the difference between a Food Chain and a Food Web?

A Food Chain shows a single path of energy transfer (who eats who), while a Food Web shows multiple food chains linked together to represent an entire ecosystem.

What is a Trophic Level?

The specific position an organism occupies in a food chain (e.g., producer, primary consumer, secondary consumer).

What is the "10% Rule"?

Only about 10% of the energy from one trophic level is passed up to the next level; the rest is lost, mostly as heat.

Write the balanced chemical equation for Photosynthesis.

6CO2 + 6H2O + Sunlight -> C6H12O6 + 6O2 (Carbon Dioxide + Water + Sun -> Sugar + Oxygen)

Write the balanced chemical equation for Cellular Respiration.

C6H12O6 + 6O2 -> 6CO2 + 6H2O + ATP (Sugar + Oxygen -> Carbon Dioxide + Water + Energy)

What is the basic purpose of Photosynthesis?

To convert light energy from the sun into chemical energy stored in glucose (food).

What is the basic purpose of Cellular Respiration?

To break down stored energy (glucose) into usable energy (ATP) for the cell.

Why do plants appear green?

Chlorophyll reflects green light and absorbs other colors (like red and blue). We see the light that is reflected.

What are the inputs and outputs of the Light Dependent Reactions?

Inputs: Sunlight, Water. Outputs: Oxygen, ATP, NADPH.

What are the inputs and outputs of the Calvin Cycle?

Inputs: Carbon Dioxide, ATP, NADPH. Outputs: Glucose (Sugar).

How are Photosynthesis and Cellular Respiration related?

The products of one are the reactants of the other. Photosynthesis makes the Glucose and Oxygen that Respiration needs; Respiration makes the Carbon Dioxide and Water that Photosynthesis needs.

Why do ecosystems rarely have more than 4 or 5 trophic levels?

Because of the 10% Rule, energy is lost at each step. By the 4th or 5th level, there isn't enough energy left to support another level of predators.