CHAPTER 4 READING QUESTIONS 4.1 ENERGY IN BIOLOGICAL SYSTEMS 1. What are the properties of living organisms? (Tbl. 4.1) 1. Have a complex structure whose basic unit of organization is the cell. 2. Acquire, transform, store, and use energy. 3. Sense and respond to internal and external environments. 4. Maintain homeostasis through internal control systems with feedback. 5. Store, use, transmit information. 6. Reproduce, develop, grow, and die. 7. Have emergent properties that cannot be predicted from the simple sum of the parts . 8 . Individuals adapt, and species evolve. 2. Contrast the energy capture and storage processes of plants and animals. (Fig. 4.1) All cells use energy from their environment to grow, make new parts, and reproduce. Plants trap radiant energy from the sun and store it as chemical-bond energy through the process of photosynthesis. They extract carbon and oxygen from carbon dioxide, nitrogen from the soil, and hydrogen and oxygen from water to make biomolecules such as glucose and amino acids. Animals cannot trap energy from the sun or use carbon and nitrogen from the air and soil to synthesize biomolecules. They import chemical-bond energy by ingesting the biomolecules of plants or other animals. Energy trapped by photosynthesis is the energy source for all animals, including humans.
Animals extract energy from biomolecules through the process of respiration , which consumes oxygen and produces carbon dioxide and water. If animals ingest more energy than they need for immediate use, the excess energy is stored in chemical bonds, just as it is in plants. Glycogen and lipid molecules are the main energy stores in animals. These storage molecules are available for use at times when an animal’s energy needs exceed its food intake. Energy Is Used to Perform Work 3. Define energy. The capacity to do work 4. List three kinds of work in biological systems and give an example of each. Chemical work – making and breaking of chemical bonds. It enables cells and organisms to grow, maintain a suitable environment, and store information needed for reproduction and other activities. o EX: forming the chemical bonds of a protein is an example of chemical work. Transport work – enables cells to move ions, molecules, and larger particles through the cell membrane and through the membranes of organelles in the cell. o Transport work is particularly useful for creating concentration gradients : distributions of molecules in which the concentration is higher on one side of the membrane than on the other.
o EX: certain types of endoplasmic reticulum use energy to import calcium ions from the cytosol. Mechanical work – used for movement. At the cellular level, movement includes organelles moving around in a cell, cells changing shape, and cilia and flagella beating. Most mechanical work is mediated by motor proteins that make up certain intracellular fibers and filaments of the cytoskeleton.
- Fall '16
- Adenosine triphosphate