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Cellular Energetics

Bioluminescence Bioluminescence by a fungus (Panellus stipticus) Bioluminescence created by some species of fungi present in decaying wood. The bluish green glow is attributed to luciferase, an oxidizing agent, which emits light as it reacts with luciferin. Cells of fungus convert energy stored in certain organic molecules to light, a process called bioluminescence. Bioluminescence and all other metabolic activities carried out by a cell are precisely coordinated and controlled. This property of fungi is attributed to metabolism for that particular species. The concepts of metabolism that you learn in this topic, will help you understand how matter and energy flow during life's processes and how that flow is regulated.

Learning Objectives

After completing the topic, the student will be able to:

  • Predict what happens if cell does not undergo metabolism and appreciate the importance of this phenomenon.
  • Define and describe the terms – anabolism and catabolism.
  • Define, describe and co–relate the terms metabolism, cell respiration, and fermentation.
  • Analyze the relationship between energy and work.
  • Co–relate the concept of work and energy to the daily activities we perform.
  • Describe the forms of energy found in an apple as it grows on a tree, falls and is digested by some one who eats it.
  • Explore how ATP transfer energy from exergonic to endergonic processes in the cell.
  • Define enzymes and describe why enzymes act only on very specific substrates.
The Source of Energy Sunlight as the Source of Energy. For photosynthetic cells, the main energy source is Sun.
Cellular Energetics

The cell is the basic unit of life. All organisms are made of cells. In the hierarchy of biological organization, the cell is the simplest collection of matter that can live. There are diverse forms of life existing as single–celled organisms. More complex organisms, including plants and animals, are multicellular; their bodies are cooperatives of many kinds of specialized cells that could not survive for long on their own. However, even when they are arranged into higher levels of organization, such as tissues and organs, cells can be singled out as the organism's basic units of structure and function.

The contraction of muscle cells moves your eyes as you read this sentence; when you decide to turn to next page, nerve cells will transmit that decision from your brain to the muscle cells of your hand. Everything an organism does occurs fundamentally at the cellular level. Life at the cellular level arises from structural order, reinforcing the themes of emergent properties and the correlation between structure and function. For example, the movement of an animal cell depends on an intricate interplay of the structures that make up a cellular skeleton. The study of energy through living systems begins with the cell and how energy is obtained and used. In this unit we study major ideas: metabolism, respiration and photosynthesis.

Cells manage a wide range of functions in their tiny package – growing, moving, housekeeping, and so on – and most of those functions require energy. Cells get this energy and use it in the most efficient manner. Cells, like humans, cannot generate energy without locating a source in their environment. However, whereas humans search for substances like fossil fuels to power their homes and businesses, cells seek their energy in the form of food molecules or sunlight. In fact, the Sun is the ultimate source of energy for almost all cells, because photosynthetic prokaryotes, algae, and plant cells harness solar energy and use it to make complex organic food molecules. Other cells rely on these food molecules for the energy required to sustain growth, metabolism, and reproduction.

Concept of Metabolism Chemical reactions in Metabolism Metabolism refers to all chemical reactions occuring in living organisms, including digestion and the transport of substances into and between different cells to sustain life. These processes allow the living organisms to grow and reproduce, maintain their structures, and respond to their environments.
Metabolism

Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. The word metabolism can also refer to all chemical reactions that occur in living organisms, including digestion and the transport of substances into and between different cells.

Metabolism is usually divided into two categories – catabolism and anabolism. Catabolism breaks down organic matter, for example to harvest energy in cellular respiration. Anabolism uses energy to construct components of cells such as proteins and nucleic acids.The chemical reactions of metabolism are organized into metabolic pathways, in which one chemical is transformed through a series of steps into another chemical, by a sequence of enzymes.

Enzymes are crucial to metabolism because they allow organisms to drive desirable reactions that require energy and will not occur by themselves, by coupling them to spontaneous reactions that release energy. As enzymes act as catalysts they allow these reactions to proceed quickly and efficiently. Enzymes also allow the regulation of metabolic pathways in response to changes in the cell's environment or signals from other cells.

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