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Definition: Respiration is a biochemical process in which glucose (a readymade source of energy) is oxidized or broken down to liberate energy.Basic Equation:
Key Features:Food acts as the primary source of energy.Oxygen is required for the oxidation of food.Energy released is trapped inside cells as ATP (Adenosine Triphosphate).Carbon dioxide ( 
) and water ( 
) are produced as end-products.Some energy produced during oxidation is lost as heat.ATP (Energy Currency): ATP is called the energy currency of the cell because it acts as the immediate source of energy for carrying out various life-sustaining activities.
Definition: The complete oxidation and breakdown of glucose into carbon dioxide and water inside cells using oxygen.Location: Occurs inside the mitochondria of cells.Organisms: Carried out by aerobes (includes the majority of plants and animals).Equation:
Definition: The incomplete breakdown of glucose without utilizing oxygen.Location: Completed entirely within the cell cytoplasm; mitochondria are not involved.Organisms: Carried out by anaerobes (e.g., yeast, certain bacteria, and parasitic flatworms).Yield: Produces very little energy compared to aerobic respiration.Equation:
Lactic Acid Fermentation: The breakdown of glucose in muscles under a deficiency of oxygen, producing lactic acid as an end-product.Yeast Fermentation: Anaerobic respiration in yeast where sugars break down into ethyl alcohol and carbon dioxide. Because of this alcohol production, yeast is used to manufacture wine and beer.
Breathing (External Respiration): A physical/mechanical process involving the exchange of respiratory gases ( 
and ) between the atmosphere and the cells via stomata and lenticels. No energy is released.Cellular Respiration (Internal Respiration): A biochemical process occurring inside the cells where glucose is oxidized in the presence of oxygen using enzymes, releasing energy stored as ATP.
Gaseous transport occurs entirely through simple diffusion.Each plant part (leaves, stems, roots) independently absorbs oxygen and expels carbon dioxide.
Leaves: Gaseous exchange occurs through tiny pores called stomata. Each stoma opens into an air cavity where oxygen diffuses in and carbon dioxide diffuses out.Stems: Young stems utilize stomata. Old woody stems develop specialized pores called lenticels underneath the bark to facilitate gaseous exchange.Roots: Root hairs extend into the air spaces between soil particles to absorb trapped oxygen.
During Daytime: Plants perform both photosynthesis and respiration. The carbon dioxide released during respiration is immediately consumed by photosynthesis. A portion of the oxygen produced in photosynthesis is used for respiration, and the rest is released. Thus, plants do not take in oxygen from the atmosphere during the day.At Night: Photosynthesis stops due to the lack of sunlight. Plants absorb oxygen from the atmosphere and release carbon dioxide.Note: Sleeping under a tree at night is discouraged because the accumulation of released carbon dioxide increases nearby concentration levels.
Photosynthesis is an endergonic process (stores solar energy in chemical bonds).Respiration is an exergonic process (releases chemical energy from glucose bonds).
Materials: Wide-mouthed bottle, two-holed cork, thistle funnel, double-bent delivery tube, test tube, water, limewater, germinating seeds, and black paper.Procedure:Place germinating seeds at the bottom of a wide-mouthed bottle.Seal the bottle with a two-holed cork. Fit a thistle funnel into one hole (closed with a cork) and a double-bent delivery tube into the other.Place the other end of the delivery tube into a test tube of water. Wrap the bottle in black paper and place it in a dark corner.Replace the water test tube with one containing limewater.Pour water slowly through the thistle funnel to displace the air in the bottle into the limewater test tube.Observation: The limewater turns milky.Conclusion: Germinating seeds release carbon dioxide gas during respiration.
Aerobes: Organisms that use oxygen to break down glucose during respiration.Anaerobes: Organisms capable of surviving and producing energy in the complete absence of oxygen.Fermentation: The anaerobic breakdown of sugars into ethyl alcohol and carbon dioxide, typically carried out by yeast.Lactic Acid: The product formed during anaerobic respiration in animal muscle cells due to oxygen deficiency.Exergonic Reaction: A chemical or biochemical reaction that produces or releases energy.Endergonic Reaction: A chemical or biochemical reaction that absorbs or consumes energy.
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Prepared by: learnloophq@gmail.com
Chapter: 05. Respiration In Plants
Chapter 5: Respiration in Plants — Crash Course Revision Material
1. Basics of Respiration
2. Aerobic vs. Anaerobic Respiration
Depending on whether oxygen is utilized or not, respiration is classified into two types:
Aerobic Respiration
Anaerobic Respiration
Special Pathways
Table 5.1: Differences between Aerobic and Anaerobic Respiration
Aerobic Respiration
Anaerobic Respiration
1. Occurs in the presence of oxygen.
1. Occurs in the absence of oxygen.
2. Glucose is completely oxidised.
2. Glucose is oxidised incompletely.
3. Carbon dioxide and water are formed as end-products.
3. End-products are ethyl alcohol (in plant cells) and carbon dioxide, or lactic acid (in animal cells).
4. More energy is produced.
4. Very little energy is produced.
5. Occurs in most plants and animals.
5. Occurs in a few organisms like yeast, some bacteria, and parasitic flatworms.
6. Mitochondria are needed.
6. Mitochondria are not needed.
3. Major Steps in Aerobic Respiration
Aerobic respiration consists of two primary stages:
Table 5.2: Differences between Breathing and Cellular Respiration
Breathing
Cellular Respiration
1. It is a mechanical process.
1. It is a biochemical process.
2. It involves exchange of respiratory gases ( and ) between atmosphere and organism.
2. It involves oxidation of glucose and production of and inside the cell.
3. It takes place by simple diffusion.
3. It takes place with the help of enzymes.
4. No energy is released during breathing.
4. Energy is released during cellular respiration.
4. Respiration in Plants
Unlike animals, plants do not possess specialized respiratory organs.
Gaseous Exchange by Plant Part:
Day vs. Night Gas Exchange:
5. Respiration vs. Photosynthesis
Photosynthesis and respiration are complementary, opposite biological processes.
Table 5.3: Differences between Respiration and Photosynthesis
Respiration
Photosynthesis
1. It takes place in all living cells of the body.
1. It takes place only in green parts of the plants.
2. It occurs all the time (day and night).
2. It occurs only in the presence of sunlight, i.e., during daytime.
3. It uses oxygen and releases carbon dioxide.
3. It uses carbon dioxide and releases oxygen.
4. It involves breakdown of glucose.
4. It involves synthesis of glucose.
5. It occurs in mitochondria.
5. It occurs in chloroplasts.
6. Chlorophyll is not needed.
6. Chlorophyll is necessary.
6. Experimental Demonstration
Aim: To show that carbon dioxide is produced by germinating seeds during respiration
7. Important Terms to Remember
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