Honors Biology Unit 4 - 4.1 Intro to Photosynthesis and Cellular Respiration

Energy from the sun is the source of all life on Earth. Plants use photosynthesis to convert sunlight into glucose, a high-energy sugar. Animals then eat the plants to obtain the energy they need.

Autotrophs are organisms that can produce their own food using photosynthesis. Examples of autotrophs include plants, algae, and cyanobacteria.

Heterotrophs are organisms that must consume other organisms to obtain energy. Examples of heterotrophs include animals, fungi, and bacteria.

ATP (adenosine triphosphate) is the energy currency of the cell. It is a molecule that stores energy in its phosphate bonds. ATP is used to power all cellular processes, including muscle contraction, protein synthesis, and active transport.

Photosynthesis is the process by which plants use sunlight to convert carbon dioxide and water into glucose and oxygen. The equation for photosynthesis is:

6CO2 + 6H2O + sunlight → C6H12O6 + 6O2
Carbon dioxide + water + sunlight → glucose + oxygen

Photosynthesis consists of two main reactions: the light-dependent reactions and the Calvin cycle.

Light-dependent reactions:

The light-dependent reactions use sunlight to split water molecules into hydrogen and oxygen. The hydrogen atoms are used to create NADPH, a high-energy electron carrier. ATP is also produced in the light-dependent reactions.

Image: [Diagram of the light-dependent reactions of photosynthesis]

Calvin cycle:

The Calvin cycle uses carbon dioxide and the energy from ATP and NADPH to produce glucose.

Image: [Diagram of the Calvin cycle]

Cellular respiration is the process by which cells release energy from glucose. The equation for cellular respiration is:

C6H12O6 + 6O2 → 6CO2 + 6H2O + energy (ATP)
Glucose + oxygen → carbon dioxide + water + energy (ATP)

Cellular respiration consists of three main reactions: glycolysis, the Krebs cycle, and the electron transport chain.

Glycolysis:

Glycolysis breaks down glucose into pyruvate. Glycolysis occurs in the cytoplasm of all cells, both aerobic and anaerobic.

Krebs cycle:

The Krebs cycle breaks down pyruvate into carbon dioxide and water. The Krebs cycle occurs in the mitochondrial matrix and requires oxygen.

Electron transport chain:

The electron transport chain uses electron carriers to produce ATP. The electron transport chain occurs on the inner mitochondrial membrane and requires oxygen.

Image: [Diagram of cellular respiration]

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