Biology Chapter 4 Flashcards

Chemical Energy and ATP

• All organisms require chemical energy for cellular processes, primarily carried by ATP (Adenosine triphosphate).
• ATP transfers energy from food breakdown to cellular activities, similar to a wallet carrying money.
• Carbohydrates are commonly broken down for ATP, while lipids yield the most energy when metabolized.

ADP and Its Role

• ADP (Adenosine diphosphate) is a lower-energy molecule which can be converted back to ATP by adding a phosphate group.
• The conversion of ADP to ATP requires complex proteins, and any defects can lead to ATP production issues.

Chemosynthesis

• Some organisms utilize chemosynthesis, using chemical energy instead of light to create carbon-based molecules.
• Similar to photosynthetic organisms, chemosynthetic organisms produce their own food, differing only in raw materials used.

Producers and Energy Flow

• Producers generate the source of chemical energy, serving as a primary energy source for other organisms.
• Plants are the main producers; consuming plants allows for direct energy intake, while eating meat relays energy indirectly through animals consuming plants.

Photosynthesis Overview

• Photosynthesis converts sunlight into chemical energy, producing sugars.
• The process involves several steps: absorbing sunlight, breaking down water, generating oxygen, and using carbon dioxide to synthesize sugars.
• The overall reaction for photosynthesis:
  • 6 CO2 + 6 H2O ➔ C6H12O6 + 6 O2

Chlorophyll and Its Role

• Chlorophyll, found in chloroplasts, absorbs energy from visible light, primarily red and blue wavelengths, and not green (which is reflected, giving plants their color).
• Two main types of chlorophyll exist: chlorophyll a and chlorophyll b.

Chloroplast Structure

• Chloroplasts are membrane-bound organelles where photosynthesis occurs, mainly located in leaf cells.
• Key components include grana (stacked thylakoids) and stroma (the surrounding fluid).

Thylakoids and Grana

• Thylakoids are coin-shaped compartments within chloroplasts, containing chlorophyll and other light-absorbing molecules.
• Grana are stacks of thylakoids, facilitating light-dependent reactions.

Light-Dependent Reactions

• These reactions capture sunlight energy and take place within the thylakoid membranes.
• Water and sunlight are essential for initiating the first steps of photosynthesis.

Light-Independent Reactions (Calvin Cycle)

• Utilize energy from light-dependent reactions to produce sugars and occur in the stroma.
• Carbon dioxide is a critical input during specific steps of the process.

Photosystems

• Energy capture and transfer during light-dependent reactions occur via photosystems in thylakoid membranes.
• Two distinct photosystems play a pivotal role in the light-dependent reactions.