Chapter 8 Cellular Energy Section 1 How Organisms

Chapter 8: Cellular Energy Section 1: How Organisms Obtain Energy Ms. Diana and Ms. Su’ad

Transformation of energy • Energy is the ability to do work. • Energy is required for cellular activities like: – Chemical reactions – Assembling and breaking down macromolecules – Transportation of substances – Transmission of genetic information • Thermodynamics – the study of the flow and transformation of energy in the universe.

Thermodynamics • The study of heat and its transformation into mechanical energy is called thermodynamics. OR “movement of heat. ” The foundation of thermodynamics is the conservation of energy and the fact that heat flows from hot to cold.

Laws of Thermodynamics • There are two laws of thermodynamics. • Law of Conservation of Energy – states that energy can be converted from one form to another, but it cannot be created nor destroyed.

Laws of Thermodynamics • Second law of thermodynamics - states that energy cannot be converted without the loss of usable energy. The energy that is ‘loss’ is converted to thermal energy. • Entropy – the measure of disorder, or unusable energy in a system. ( the measure of randomness or disorder within a system. High entropy means high disorder • The 2 nd Law of Thermodynamics is usually referred to as ‘entropy increases’.

Autotrophs and Heterotrophs • All organisms need energy to live. All of this energy comes directly or indirectly from the Sun. • Autotrophs – organisms that make their own food. – Chemoautotrophs – use inorganic substances such as hydrogen sulfide as a source of energy. • Heterotrophs – organisms that need to ingest food to obtain energy.

Autotrophs vs. Heterotrophs

Metabolism • Metabolism – all of the chemical reactions in a cell. A series of chemical reactions in which the product of one reaction is the substrate ( input/ reactant) for the next reaction is called a metabolic pathway. Anabolism ( constructive ) A process where by living organisms use simpler substances to put together, or build complex substances such as carbohydrates, proteins and fats for storage. Such an activity is known as an anabolic activity. Energy is required for this pathway. • • Catabolism ( Destructive) This is when the cells in living organisms, breakdown complex substances and molecules into simpler substances, often to release energy for use. The relationship between catabolic and anabolic pathways is what makes the flow of energy continuous within an organism. • The metabolism is a continuous process. The moment metabolism stops, the living organism will die.

Catabolic vs. Anabolic

Photosynthesis • Energy is continually flowing between the metabolic reactions of organisms. • Photosynthesis – the anabolic pathway in which light energy from the Sun is converted to chemical energy for use by the cell. • Autotrophs use light energy, carbon dioxide, and water to form glucose and oxygen. The energy stored in the glucose can then be transferred to other organisms when they consume the molecules as food.

Cellular Respiration • Cellular Respiration – the catabolic pathway in which complex organic molecules are broken down to release energy for use by a cell. • In cellular respiration, oxygen is used to break down organic molecules, resulting in the production of carbon dioxide and water. • Both photosynthesis and cellular respiration are in a cyclical process where the products of one reaction are the reactants for the other.

Cycle of anabolic and catabolic pathways

Photosynthesis and Cellular Respiration • Photosynthesis: • Cellular Respiration:

ATP: The Unit of Cellular Energy • Energy exists in many forms (light energy, mechanical energy, thermal energy, chemical energy). • In living organisms, energy is stored in biological molecules that can be converted to other types of energy. • ATP (Adenosine Triphosphate) – the most important biological molecule that provides chemical energy.

ATP Structure • ATP is a storehouse of chemical energy that can be used by cells in different ways. • ATP is the most abundant energy carrier molecule in cells. • ATP is found in all types of organisms

ATP Function • When ATP breaks apart, it releases energy and loses a phosphate group. • That means that it is now ADP (adenosine diphosphate) and a free phosphate group. • Most of the energy reactions in the cell involve ATP and ADP.