Grade 10 Biology - Respiration PDF

/ Kuala Lumpur, Malaysia TERM: I NAME: _______________________ REF: 2024-25/ BIO/ T1/ STD 10/ HO-03 CLASS: ___________________ SUBJECT: Biological Science DATE: 1...

/ Kuala Lumpur, Malaysia TERM: I NAME: _______________________ REF: 2024-25/ BIO/ T1/ STD 10/ HO-03 CLASS: ___________________ SUBJECT: Biological Science DATE: 19.04.2024 TOPIC: Life Processes - Respiration RESPIRATION The process by which a living being utilizes the food to get energy is called respiration. Respiration is an oxidation reaction in which carbohydrate is oxidized to produce energy. The energy released is stored in the form of ATP (Adenosine triphosphate). ATP is stored in mitochondria and is released as per need of the cell. STEPS OF CELLULAR RESPIRATION: 1. Glycolysis (Break down of glucose into pyruvate): This step happens in the cytoplasm of a cell. Glucose molecule is broken down into pyruvic acid. Glucose molecule is composed of 6 carbon atoms, while pyruvic acid is composed of 3 carbon atoms. There is a net gain of 2 ATP molecules in the process. 2. Fate of Pyruvic Acid: Further break down of pyruvic acid or pyruvate produced during Glycolysis depends on the type of respiration in a particular organism. Respiration is of two types, viz. aerobic respiration and anaerobic respiration. TYPES OF RESPIRATION: 1. Aerobic Respiration: This type of respiration happens in the presence of oxygen, and in mitochondria of eukaryotic cells. In the Kreb’s cycle or TCA (Tricarboxylic acid cycle), Pyruvic acid formed in Glycolysis is completely oxidized in presence of O2 to CO2, H2O and with a release of energy in the form of 36 ATP molecules. So, net energy gain during Aerobic respiration is 38 ATP molecules. 2. Anaerobic Respiration: This type of respiration happens in the absence of oxygen in the cytoplasm of the cell. Pyruvic acid is either converted into ethyl alcohol or lactic acid. [i] Ethyl alcohol is usually formed in case of anaerobic respiration in microbes; like yeast or bacteria. [ii] Lactic acid is formed in some microbes as well as in our muscle cells when we do rigorous exercise. Net gain of ATP in both cases of Anaerobic respiration is 2 ATP molecules. Respiration In Plants Plants use oxygen of air for respiration and release carbon dioxide.The respiration in plants differs from the animals in three respects: Plants have a branching shape, so they have quite a large surface area in comparison to their volume. Therefore, diffusion alone can supply all the cells of the plants with as much oxygen as they need for respiration. Diffusion occurs in the roots, stems and leaves of plants. Respiration in Roots: Air occurs in soil interspaces. Root hairs of the roots are in direct contact with them. Air diffuses through root hair and reaches all internal cells of the root for respiration. Carbon dioxide produced by root cells is expelled by diffusion. Extra information In water-logged conditions, soil spaces are filled with water. In the absence of oxygen, metabolic activity of the root declines and the plant may wither. Mangrove trees have adaptive roots called breathing roots or pneumatophores which come out of the soil and help these trees to breathe in oxygen from air. Respiration in Stems and leaves: The stems of herbaceous plants and in general leaves have stomata. The exchange of gases for respiration happen when air diffuses into or out of the stomata. In woody stems, the bark has lenticels for gaseous exchange. Net gaseous exchange in the leaves of the plant: During day time, when photosynthesis occurs, oxygen is produced. The leaves use some of this oxygen for respiration and rest of the oxygen diffuses out into air.  Again, during the daytime, carbon dioxide produced by respiration is all used up in photosynthesis by leaves. Even more carbon dioxide is taken in from air. Thus net gas exchange in leaves during day time is: O2 diffuses out ; CO2 diffuses in. At nighttime, when no photosynthesis occurs and hence no oxygen is produced, oxygen from air diffuses into leaves to carry out respiration. And carbon dioxide produced by respiration diffuses out into air. Thus, net gas exchange in leaves at night is: O2 diffuses in; CO2 diffuses out. Respiration in Animals Different animals have different modes of respiration. Animals Respiratory organ Unicellular animals like Cell membrane Amoeba, Planaria Earthworm Moist Skin Aquatic animals like Fish, Gills Prawns Insects like Grasshopper, Spiracles and tracheae Cockroach Land animals like Humans, Lungs birds All the respiratory organs in animals have three common features: They have a large surface area to get enough oxygen. They have thin walls and must be kept moist in order for gases to dissolve and diffuse across cell membrane. Respiratory organs like skin, gills, and lungs have a rich supply of blood vessels for transporting respiratory gases. Terrestrial animals can breathe the oxygen in the atmosphere, but animals that live in water (aquatic animals) needs to use the oxygen dissolved in water. Since the amount of oxygen dissolved in water is fairly low as compared to the amount of oxygen in the air, the rate of breathing in aquatic organisms is much faster than that seen in terrestrial organisms. Respiration in Amoeba: Amoeba is a unicellular microscopic organism. It breathes by simple diffusion of gases through its cell membrane. Amoeba lives in water. It breathes in oxygen dissolved in water, uses it for respiration and the carbon dioxide produced diffuses out through the membrane of Amoeba into surrounding water.  Respiration in Earthworm: The earthworm exchanges the gases through its moist skin. The oxygen is then transported to all the cells of the earthworm by its blood where it is used in respiration. The carbon dioxide produced during respiration is carried back by the blood. This CO 2 is expelled from the body of the earthworm through its skin. Respiration in Fish: The fish has special organs for breathing called ‘gills’. The fish has gills on both the sides of its head. The fish lives in water and this water contains oxygen dissolved in it. The fish breathes by taking in water through its mouth and sending it over the gills. When water passes over gills, the gills extract dissolved oxygen from this water. The water then goes out through the gill slits. The extracted oxygen is absorbed by the blood and carried to all the parts of the fish. The carbon dioxide produced by the respiration is brought back by the blood into the gills for expelling into the surrounding water. Respiration in Insects: Insects have openings called spiracles or air holes. They have a network of air tubes called tracheae for gas exchange. Oxygen rich air through spiracles rush into the tracheal tubes, diffuses into the body tissue, and reaches every cell of the body. Similarly, carbon dioxide from the cells goes into the tracheal tubes and moves out through spiracles. These air tubes or tracheae are found only in insects and not in any other group of animals. Note: diffusion is insufficient to meet the oxygen requirements of large multicellular organisms like humans because the volume of human body is so big that oxygen cannot diffuse into all the cells of the human body quickly. Respiratory system in Humans The main organs of human respiratory system are: Nose, Nasal passage, Trachea (wind pipe), Bronchi, Lungs and Diaphragm. The human respiratory system begins from the nose. The air then goes into nasal passage. The nasal passage is lined with fine hair and mucus. When air passes through the nasal passage, the dust particles and other impurities present in it are trapped by nasal hair and mucus so that clean air goes into lungs. The part of throat between the mouth and wind pipe is called pharynx, a portion of which is the common passage for food and air. The pharynx opens through the larynx region into the trachea. Larynx is a cartilaginous box which helps in sound production and hence called the sound box. During swallowing glottis can be covered by a thin elastic cartilaginous flap called epiglottis to prevent the entry of food into the larynx. Trachea does not collapse even when there is no air in it because it is supported by rings of cartilage. The trachea runs down the neck and divides into two smaller tubes called bronchi at its lower end. The bronchi are connected to the two lungs. The lungs lie in the chest cavity or thoracic cavity which is separated from abdominal cavity by a muscular partition called diaphragm. They are found next to the heart. They are protected by the rib cage and the muscles associated with the ribs. There are 12 pairs of ribs and two sets of muscles called the outer and inner intercostal muscles in the chest wall. Each bronchus divides in the lungs to form a large number of still smaller tubes called bronchioles. The pouch-like air sacs at the ends of the smallest bronchioles are called alveoli. The walls of alveoli are very thin and are richly supplied with blood capillaries. It is in the alveoli that gaseous exchange takes place. Exchange of gases at the alveolar surface in our lungs: The alveoli are adapted to exchange gases in lungs easily and efficiently. Here are some features of the alveoli that allow this: 1. They give the lungs a really big surface area 2. They have moist, thin walls (just one cell thick) 3. They have a lot of tiny blood vessels called capillaries The gases move by diffusion from where they have a high concentration to where they are at a low concentration: Oxygen diffuses from the air in the alveoli into the blood. Carbon dioxide diffuses from the blood into the air in the alveoli. EXCHANGE OF GASES ACROSS ALVEOLAR SURFACE Mechanism of Breathing: Breathing involves two stages: inspiration or inhalation during which atmospheric air is drawn in and expiration or exhalation by which the alveolar air is released out. Inhalation: 1. Begins by the contraction of diaphragm which increases the volume of thoracic cavity. 2.The contraction of external inter-costal muscles lifts up the ribs and the sternum causing an increase in the volume of the thoracic cavity. 3. In response, the air pressure inside the lungs decreases below that of air outside the body. Because gases move from regions of high pressure to low pressure, air rushes into the lungs. Exhalation: 1. Occurs when the diaphragm and external intercostal muscles relax. 2. In response, the elastic fibers in lung tissue cause the lungs to recoil to their original volume. The pressure of the air inside the lungs then increases above the air pressure outside the body, and air rushes out. Note: 1. During the breathing cycle, when air is taken in and let out, the lungs always contain a residual volume of air so that there is sufficient time for oxygen to be absorbed and for the carbon dioxide to be released. 2. Residual Volume (RV): Volume of air remaining in the lungs even after a forcible expiration. This averages 1100 ml to 1200 ml. 3. Carbon dioxide is more soluble in water than oxygen is and hence is mostly transported in the dissolved form in our blood. Composition of Inhaled and Exhaled air: Mechanism of gaseous exchange between tissues and blood: Gaseous exchange in humans at tissue level, occurs by diffusion. In lungs oxygen from alveolar air diffuses into capillaries and CO2 from blood is given out into lungs. This oxygen is carried to the tissues and it diffuses from blood vessels into the tissues. The carbon dioxide produced in the tissues diffuses into the blood capillaries supplying blood to the tissues, from where it is carried to the lungs. Differences Between Inhalation and Exhalation: Point of Inhalation Exhalation Difference Meaning The process of intake of air into The process of letting air out from lungs lungs. Event As muscles contract, inhalation is As muscles do not actively an active process contract, exhalation is a passive process.  Chest size Increases Decreases Role of The diaphragm contracts during It relaxes during exhalation and diaphragm inhalation and flattens by moving assumes its dome-shape by down. moving up. Role of The internal intercostal muscles In the exhalation process internal intercostal relax and external intercostal intercostal muscles contract and muscles muscles contract in the inhalation external intercostal muscles relax. process. Volume of The volume of lungs increases It decreases during exhalation Lungs during inhalation it means it gets means it gets deflated. inflated. Air Pressure Inhalation results in a decrease in In exhalation, there is an increase air pressure (below atmospheric in air pressure in the lungs. pressure) in the lungs. Rib cage Due to the effect of intercostal While in exhalation the rib cage muscles rib cage moves upward moves downward. and outward in inhalation How are the respiratory gases carried in our blood? Respiratory pigment, hemoglobin, is present in Red blood cells or erythrocytes. At the alveolar surface when the alveolar sac is filled with inhaled air, hemoglobin in RBC binds to oxygen molecule to form oxyhemoglobin. At the tissue level, where the cells are continuously respiring and producing CO 2 then the oxyhemoglobin loses O2 to tissue by diffusion and the CO2 moves into the blood and forms carbaminohemoglobin when CO2 binds with the hemoglobin molecule. Sometimes we burn firewood at a fireplace or angithi in a closed room/ house during winters. When combustion happens in limited supply of oxygen, carbon monoxide (CO) is produced due to incomplete combustion. Carbon monoxide has a high affinity for hemoglobin than CO2 and O2. Hemoglobin binds to carbon monoxide and carboxyhemoglobin is formed. Carboxyhemoglobin is a very stable molecule, so it does not dissociate from hemoglobin easily. So, the hemoglobin available to bind O2 in our blood goes down. This leads to Carbon monoxide poisoning. People in the closed room can become senseless or die due to this poisoning. Majority of the oxygen is transported as oxyhemoglobin in our blood. Only 1.5 percent of oxygen in the blood is dissolved directly into the blood itself. 70-75% of Carbon dioxide is transported in the blood as bicarbonate ions and 20- 25% as carbaminohemoglobin and the rest 7% of CO2 is dissolved in blood plasma. Breathing rate in humans: On an average, a healthy human breathes 12-16 times/minute. Tidal Volume (TV): Volume of air inspired or expired during a normal respiration. It is approx. 500 ml, i.e., a healthy man can inspire or expire approximately 6000 to 8000 ml of air per minute. Extra Information: A ventilator is a machine that delivers oxygen to the lungs and removes carbon dioxide from the lungs. It uses a tube that goes through the nose, mouth, or a surgical opening in the windpipe. The ventilator can control the pressure, volume, temperature, and humidity of the air. The ventilator also helps to prevent the lungs from collapsing by maintaining positive air pressure. The ventilator can be programmed to pump air in and out of the lungs at a certain rate or let the patient exhale on their own. The ventilator is connected to a monitor that can adjust the oxygen level and send alarms if needed. A ventilator can help a patient who has trouble breathing or who cannot breathe on their own. Practice Questions 1. What are the characteristics of an ideal respiratory 2 surface? 2. What are lenticels? 1 3. How does exchange of gases take place in fish? 1 4. How aerobic respiration different from anaerobic 2 respiration? 5. Explain the process of breathing in man. 3 6. How does exchange of gases take place in the alveoli? 3 7. What is oxyhemoglobin and how is it formed? 2 8. How does carbon dioxide get transported in the blood? 2 9. What are the major steps of cellular respiration? 3 10. Which type of respiration is more efficient- aerobic or 2 anaerobic? Why? 11. What are the uses of fermentation? 2