Forms and Laws of Energy

Forms of Energy

• Energy flows into ecosystems as sunlight and leaves as heat, while essential chemical elements are recycled.
• Electromagnetic waves (sunlight) are the energy capacity to cause change in matter rearrangements.
• Energy exists in different forms in the environment.
• Heat can be converted from mechanical energy to electrical energy.
• Kinetic energy, thermal energy (heat), light energy, potential energy, and chemical energy are forms of energy.
• Thermodynamics studies energy transformations in systems (collections of matter).
• Living systems are open systems, exchanging energy and matter with surroundings.
• Systems include the system and surroundings; the universe includes both.
• There are different types of systems.

Laws of Energy Transformations

• Thermodynamics considers heat (therme) and transformations (dynamis).
• The first law of thermodynamics states that energy in the universe is constant; it can be transferred and transformed but not created or destroyed.
• The first law has two types of changes: transfer and transformation.
• Transfer includes conduction (solid-to-solid heat), convection (liquid-to-liquid heat), and radiation (gas).
• The second law of thermodynamics states that every energy transfer increases disorder (entropy), and living organisms are open systems with these energy transfers.
• Entropy describes energy unavailable for work; it increases in every transformation.
• An example is the food chain with varying energy transformation efficiency at each trophic level (production percentages).

ATP-ADP Cycle

• ATP (adenosine triphosphate) is the energy currency of cells.
• GTP is another energy form that powers cellular work.
• ATP has three phosphate groups, a ribose, and an adenine structure.
• ATP performs three types of cellular work (transport, mechanical, and chemical).
• ATP is regenerated by phosphorylation of ADP; ADP is two phosphates.
• Hydrolysis (using water to break bonds) releases energy from ATP to ADP
• This energy is used for cellular processes (chemical work, mechanical work, and transport work).

Photosynthesis

• Plant cells use chloroplasts, grana, thylakoids, and chlorophyll (alpha and beta) to capture sunlight's energy for photosynthesis.
• Carotenoids are pigments that absorb energy and provide color.
• Chlorophyll absorbs all colors of light accept green which is reflected.
• Carotenoids are light-absorbing pigments that assist in photosynthesis.

Photoexcitation

• Chlorophyll molecules absorb light energy and excite electrons (causing electrons transition levels) to higher energy levels.
• The excited electrons are transferred to other molecules, moving energy.
• This process occurs in photo systems.