Unit 2 Nucleic Acids & Movement Of Substances PDF

**Unit 2** **Nucleic Acids & Movement of substances within the body** **Learning Objectives:** At the end of this unit the students should be able to: 1. State the role of nucleic acids. 2. State the composition and function of nucleic acids. 3. Classify nucleic acids into DNA and RNA. 4....

**Unit 2** **Nucleic Acids & Movement of substances within the body** **Learning Objectives:** At the end of this unit the students should be able to: 1. State the role of nucleic acids. 2. State the composition and function of nucleic acids. 3. Classify nucleic acids into DNA and RNA. 4. State the difference between DNA and RNA. 5. Explain the importance of synthesis of ATP. 6. Define diffusion and list the factors, which affect it. 7. Explain diffusion across membranes. 8. Define the term osmosis. 9. Explain isotonic, hypotonic and hypertonic solution. 10. Explain bulk flow. **Unit-2** **Nucleic Acids & Movement Of Substances Within The Body** **Nucleic acids** **They are the building blocks of living organisms.** The role of nucleic acids is fundamental: They make up the genes, which provide the basic blueprint of life. They not only determine what type of organism one would be but also directs ones growth and development. They do this entirely by dictating protein structure. The difference between two individuals is due to the difference between the proteins they can make and protein synthesis is under genetic control. **Composition of Nucleic Acids** Nucleic acids are composed of oxygen, carbon, hydrogen, nitrogen and phosphorous atoms. They are the largest biological molecules in the body. **Function** The main function of nucleic acids is the storage, transmission and use of genetic information upon which the continuation of cell structure depends. The two major kinds of nucleic acids are: 1. Deoxyribonucleic acid (DNA). 2. Ribonucleic acid (RNA). DNA and RNA differ in many respects. DNA is the genetic material found within the cell nucleus (the control center of the cell). It has two fundamental roles: 1. **It replicates itself exactly before a cell divides, ensuring that the genetic information in every body cell is identical.** 2. **It provides the instructions for building every protein in the body.** RNA is located outside the nucleus and can be considered as the \"molecular slave\" of DNA, that is **RNA carries out orders for protein synthesis issued by DNA.** **Adenosine Triphosphate (ATP)** The synthesis of adenosine triphosphate (ATP) is important because it provides a form of chemical energy that is usable by all body cells. Without ATP, molecules cannot be made or broken down, cells cannot maintain their boundaries and all life processes grind to a halt. **Principles of Diffusion and Osmosis** **Diffusion** Diffusion refers to the movement of a chemical substance from an area of high concentration to an area of low concentration, and occurs mainly in gases, liquids and solutions. Sugar cube at the bottom of a cup of coffee which was not been stirred well, was evenly distributed throughout the liquid by diffusion. The process of diffusion is speeded up if the temperature rises and / or the concentration of the diffusing substance is increased. The process of diffusion has many applications in body function. E.g. Absorption of nutrients, exchange of oxygen and carbon dioxide, kidney function and dialysis. Diffusion across Membranes -------------------------- To better understand how diffusion accounts for the movement of various molecules through a cell membrane, imagine a container of water that is separated into two compartments by a permeable membrane This membrane has numerous pores that are large enough for water and sugar molecules to pass through. Sugar molecules are placed in one compartment (A) not in the other (B). Although the sugar molecules will move in all directions, more will diffuse from compartment A (where they are in greater concentration) through the pores in the membrane and into compartment B (where they are in lesser concentration) than will move in the other direction.  At the same time, water molecules will tend to diffuse from compartment B (where they are in greater concentration) through the pores into compartment A (Where they are in lesser concentration). Eventually, equilibrium will be achieved when there are equal amounts of water and sugar molecules in each compartment. Similarly, oxygen molecules diffuse through cell membranes and enter cells if these molecules are more highly concentrated on the outside than on the inside. Carbon dioxide molecules, too, diffuse through cell membranes and leave cells if they are more concentrated on the inside than on the outside. Thus it is by diffusion that oxygen and carbon dioxide molecules are exchanged between the air and the blood in the lungs and between the blood and the cells of various tissues. OSMOSIS AND BODY FLUID BALANCE Principles of Osmosis A large proportion of a human body consists of water. The diffusion of water is an important component of normal cell function and this diffusion is referred to as osmosis. **Osmosis** is the net movement of water through a semi- permeable membrane from an area of high water concentration to an area of low water concentration. A semi permeable membrane is a membrane, which allows the movement of water but not other substances, through it. When a semi- permeable membrane separates solutions of different concentrations, water will diffuse from the region of high water concentration to the region of low water concentration. HYPERTONIC SOLUTIONS If cells were put into a water solution that had a greater concentration of solute particles (higher osmotic pressure) than did the cells, the cells would begin to shrink and are said to become crenated. **The solution whose concentration is more than that of the concentration of the fluid inside the blood cell is called Hypertonic solutions.** Water will flow out of the cells and they would shrink. Hypertonic solutions are sometimes given to patients who have edema (swollen feet and hands) because of fluid retention. Such solutions draw water out of the tissue spaces into the blood stream so that the excess fluid can be eliminated by the kidney. **HYPOTONIC SOLUTION** If there is a greater concentration of solute particles inside a cell than in the water around it, water will diffuse into the cell. As this happens, water accumulates within the cell, and it begins to swell. The solution whose concentration is less than that of the concentration of the fluid inside the blood cell is called Hypotonic solutions. In this case, water will flow into the cells if placed in this solution and they would swell. E.g. Tea, colas, apple juice and sports drinks are hypotonic. Hypotonic solutions are sometimes infused intravenously (slowly and with care) to rehydrate the tissues of extremely dehydrated patients. In less extreme cases of dehydration, drinking hypotonic fluids usually does the trick. **Isotonic solution** A solution that contains the same concentration of solute particles as a cell is said to be isotonic to that cell. In such a solution, water enters and leaves the cell in equal amounts, so the cell size remains unchanged. **Definition: Two solutions are said to be isotonic, when they have the same concentration of dissolved substances.** **When isotonic solutions are separated by semipermeable membrane no osmosis occurs between them.** Most intravenous solutions are isotonic solutions.  Bulk flow It is the movement of a fluid ( liquid or gas ) from a region of higher pressure to one of lower pressure. It applies to the movement of mass of molecules rather than to the movement of individual molecules, thus the term "bulk". In the human body blood flows through the blood vessels by bulk flow and air flows in and out of the lungs by bulk flow.***\ *Unit 2** **Nucleic Acids & Movement Of Substances Within The Body** Worksheet **Fill in the blanks** 1. Nucleic acids make up the \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_,which provides the basic blueprint of life. 2. Nucleic acids directs one's \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ and \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_. 3. Nucleic acids are the largest \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ molecules in the body. 4. \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ are the building blocks of nucleic acids. 5. DNA \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ itself exactly before a cell divides ,ensuring that the genetic information in every body cell is identical. 6. DNA provides the \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ for building every protein in the body. 7. RNA is located \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_the nucleus. 8. RNA carries out \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ for protein synthesis issued by DNA. 9. DNA is \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ in function. 10. RNA takes part in \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ synthesis. 11. ATP provides a form of \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_energy that is usable by all body cells. 12. \_\_\_\_\_\_\_\_\_\_\_is the net movement or flow of particles independent of metabolic energy from one region to another. 13. \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_is the net movement of water through a semi-permeable membrane from an area of high water concentration to a region of low water concentration. 14. Two solutions are said to be \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_when they have the same concentration of dissolved substances. 15. Most intravenous solutions are \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_solutions. 16. \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_solutions causes the normal cells to swell. 17. Hypotonic solutions are sometimes infused \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_to rehydrate the tissues of extremely dehydrated patients. 18. \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_solutions have a lower water concentration than cells. 19. \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_solutions are sometimes given to patients who have edema because of fluid retention. 20. In human body blood flows through the blood vessels by \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_. 21. In human body air flows in and out of the lungs by\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_. **Answer the following questions** ================================== 1. State the role of nucleic acids? 2. State the building blocks of nucleic acids ? What do they consist of? 3. Explain in what way does DNA differ from RNA with respect to its function? 4. Why is the synthesis of ATP important? 5. What would have happened if there was no ATP? 6. Define Diffusion ? 7. Define Osmosis? 8. What do you understand by Semi -- permeable membrane? 9. Illustrate with the help of examples what happens when the red blood cells are placed in : a. Isotonic b. Hypotonic and c. Hypertonic solutions. 10. What is bulk flow? Give examples.