9th Class Biology Chapter 7 Notes
Important Notes of Chapter No.7: Bioenergetics or 9th Class Biology Chapter 7 Notes written by Honorable Sir Adnan Haider Suib. These notes are very helpful in the preparation of 9th Class Biology Chapter 7 Notes for students of the 9th class Biology Urdu Medium and these are according to the paper patterns of all Punjab boards.
Summary and Contents:
Topics which are discussed in the notes are given below:
- Very Important Multiple Choice Questions (MCQs) of Chapter No.7: Bioenergetics Urdu Medium.
- Bioenergetics And The Role Of ATP: Bioenergetics is the study of energy relationships and energy transformations (conversions) in living organisms. Organisms obtain energy by metabolizing the food they eat or prepare. Food contains potential energy in its bonds. When these bonds are broken down, a large amount of kinetic energy is usually released. Some of this energy is stored in the form of potential energy in the bonds of ATP molecules while the rest escapes as heat. The potential energy stored in ATP is again transformed into kinetic energy to carry out life activities.
- Plants and some microorganisms (e.g. photosynthetic bacteria and algae) prepare their own food from carbon dioxide and water in the presence of light by a process called photosynthesis. Whereas animals, fungi and many microorganisms (non-photosynthetic bacteria and protozoans) get the prepared food.
- Oxidation-Reduction Reaction: Various life processes in organisms involve constant flow of energy. This energy flow comprises the acquisition, transformation and use of energy for various life processes like growth, movement, reproduction etc.
- For all life processes, oxidation-reduction reactions (redox reactions) are the direct source of energy. Redox reactions involve exchange of electrons between atoms. The loss of electrons is called oxidation while the gain of electrons is called reduction.
- Electrons can be an energy source. It depends upon their location and arrangement in atoms. For example; when they are present in oxygen, they make stable association with oxygen atom and are not good energy source. But if electrons are dragged away from oxygen and attached to some other atom e.g. carbon or hydrogen, they make unstable association. They try to move back to oxygen and when this happens, energy is released.
- In living organisms redox reactions involve the loss and gain of hydrogen atoms. We know that a hydrogen atom contains one proton and one electron. It means that when a molecule loses a hydrogen atom, it actually loses an electron (oxidation) and similarly when a molecule gains hydrogen atom, it actually gains an electron (reduction).
- ATP was discovered in 1929 by Karl Lohmann, and was proposed to be the main energy-transfer molecule in the cell by the Nobel prize winner, Fritz Lipmann in 1941.
- ATP: The Cell’s Energy Currency: The major energy currency of all cells is a nucleotide called adenosine triphosphate (ATP). It is the main energy source for majority of the cellular functions like synthesis of macromolecules (DNA, RNA, and proteins), movement, transmission of nerve impulses, active transport, exocytosis and endocytosis etc.
- The ability of ATP to store and release energy is due to its molecular structure. Figure 7.3 shows a simplified diagram of ATP. Each ATP molecule has three subunits: (a) adenine - a double-ringed nitrogenous base; (b) a ribose - a five-carbon sugar; and (c) three phosphate groups in a linear chain.
- Photosynthesis: Photosynthesis is the synthesis of glucose from carbon dioxide and water in the presence of sunlight and chlorophyll, with oxygen as a by-product. Photosynthesis is an anabolic (building) process and is an important component of bioenergetics in living systems.
- It is the most important biochemical pathway and nearly all life depends on it. It comprises many coordinated biochemical reactions that occur in plants, some protists (algae), and some bacteria. A simple general equation for photosynthesis is as follows:
- 6CO2 + 12H2O + Light energy --------> C6H12O6 + 6O2 + 6H2O