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TOPIC 5: GASEOUS EXCHANGE AND RESPIRATION
Parts of the Respiratory System
Identify parts of the respiratory system
The gaseous exchange in mammals takes place in the lungs.
The Features of Different Parts of the Respiratory System and their Adaptive Features
Describe the features of different parts of the respiratory system and their adaptive features
The Features of Different Parts of the Respiratory System include the following:
- Nose and nasal cavity: It has mucus and hair which trap dust and microorganisms
- Glottis: It is situated in the epiglottis which closes the trachea during swallowing to prevent food from entering the respiratory system
- Trachea, Bronchus, and Bronchioles: They have blood vessel which have ring cartilage and mucus which warm hair and prevent collapse of respiratory track also they trap and fitter dust and micro organisms
- Lungs:They are sponge with air space (alveoli) which is the main organ of mammalian gaseous exchange
- Ribs: They are made up of hard bone tissues which protect the lungs from injury.
- Intercostal muscles: They more antagonistically to allow expansion and relaxation of the thoraic cavity
- Diaphragm: is the muscular sheet of tissue which separate thorax from abdomen
- Alveoli: they are numerous in number; they are moist and thin membranes
Functions of alveolus
- Provide surface area for gaseous exchange
- Reduce distance for diffusion of gaseous
- Enable gaseous to dissolve into solution before diffusing
- Transport oxygen from the alveoli to the tissues and carbon dioxide to the alveoli
- Maintain the shape and avoid collapsing
The Mechanism of Gaseous Exchange in Mammals
Describe the mechanism of gaseous exchange in mammals
Gaseous exchange in mammals happens as a result of inhalation and exhalation. Inhalation is breathing in air in to the lungs. Exhalation is the breathing out of air from the lungs. During inhalation the muscle of the diaphragm contract pulling the diaphragm downwards. As this happens, the external inter costal muscle contract and pull the rib cage upward and outwards. This increase volume and decreases pressure in the thorax. This makes air rush in the lungs.
During exhalation the muscles of the diaphragm resumes its dome shape. The external intercostal muscles relax pulling the rib cage inwards and downwards. This decreases volume and increases pressure. This forces air out through the bronchioles, trachea and nostrils
Gaseous Exchange Across the Alveolus
Describe gaseous exchange across the alveolus
The actual exchange of oxygen and carbon dioxide takes place in the alveoli. One mammalian lung has millions of alveoli. When we breathe air in it accumulates in the alveoli. There is higher concentration of oxygen in the alveoli than in the blood stream. The oxygen combines with hemoglobin to form oxy hemoglobin. Oxygen is then transported to the tissues
The tissue use oxygen and release carbon dioxide which diffuses in blood capillaries and combine with hemoglobin to form carbon hemoglobin. Capillaries transform this form to alveoli as it is then transported through the bronchioles trachea, glottis, pharynx, and finally nostrils into the atmosphere.
Factors Affecting Gaseous Exchange in Mammals
Outline factors affecting gaseous exchange in mammals
Factors affecting gaseous exchange in mammals include the following:
- Exercise or physical activities
- Age
- Emotions
- Temperature
- Health
- Carbon dioxide concentration
- Hemoglobin concentration
In plants gaseous exchange takes place through the stomata on the leaves and lenticels on the stem. But some plants such as mangrove also carry out gaseous exchange through breathing roots.
Parts of Plant Responsible for Gaseous Exchange
Identify parts of plant responsible for gaseous exchange
In plants gaseous exchange takes place through the stomata on the leaves and lenticels on the stem. But some plants such as mangrove also carry out gaseous exchange through breathing roots.
The Process of Gaseous Exchange in Plants
Describe the process of gseous exchange in plants
Gaseous exchange in leaves: Through stomata, atmospheric air moves in and out of the leaf. Gaseous exchange mostly takes place in the air spaces in the spongy mesophyll.
During the day, green plants carry out photosynthesis to produce glucose and this takes place within the guard cells that surround the stomata then the cell sap of the guard cells becomes hypertonic and draws in water from the neighboring cells by osmosis.
The guard cells become turgid and the stomata open whereby the air from the atmosphere such as carbon dioxide enters into the air spaces in the spongy mesophyll.
In this case carbon dioxide (CO2) is more in the air within the air space but oxygen is less. Then the carbon dioxide and oxygen diffuse in opposite direction depending on their concentration gradients (such as oxygen out and carbon dioxide in). The carbon dioxide diffuses into neighboring cells until it reaches the site for photosynthesis and oxygen moves out through the open stomata to the atmosphere.
During the night there is no light so that photosynthesis ceases and there is no production of glucose. Therefore the guard cells do not absorb water by osmosis hence the stomata remain partially closed.
However respiration process takes place at night in plants. The partially open stomata allow small amount of air to enter and accumulate in the air spaces. In this case there is more oxygen and less carbon dioxide in the air spaces compared to plant cells.
Oxygen moves into the plant cells while carbon dioxide moves into the air spaces and eventually into the atmosphere through the partially open stomata. This explains why green plants produce carbon dioxide at night and oxygen during the day.
Importance of Gaseous Exchange in Plants
Explain the importance of gaseous exchange in plants
Importance of Gaseous Exchange in Plants include the following:
- It enables the plants to eliminate excess carbon dioxide at night of which if left will harm the plants
- It enables plants to obtain carbon dioxide which is one of the raw materials necessary for photosynthesis
- Plants obtain oxygen which is necessary for production of energy which is produced during respiration through gaseous exchange
The Concept of Aerobic Respiration
Explain the concept of aerobic respiration
This is the combustion reaction. This means that oxygen is required in order to generate ATP. The simplified reaction of respiration of carbohydrates is C6H12O6.
Aerobic respiration – In the presence of oxygen glucose molecules are broken down into carbon dioxide water and energy
Equation of Aerobic respiration
C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy (38ATP)
The Mechanism of Aerobic Respiration
Outline the mechanism of aerobic respiration
Respiration starts with glucose (usually). In aerobic and anaerobic respiration initial reactions are common as a result of which pyruvic acid is formed by breakdown of glucose.
The process is called Glycolysis or EMP Pathway (Embden-Meyerhof-Parnas Pathway). This process does not require O2 although this can take place in the presence of oxygen. After this stage, the fate of pyruvic acid is different depending upon the presence or absence of oxygen.
If oxygen is present there is complete oxidation of pyruvic acid into H2O and CO2 and chemical reactions through which this occurs is called Tri-Carboxylic Acid cycle (TCA Cycle) or Krebs Cycle. This cycle occurs in mitochondria. If oxygen is absent, pyruvic acid forms ethyl alcohol (C2H5OH) and CO2 without the help of any cell organelle. This process is called anaerobic respiration.
Experiments on Aerobic Respiration
Carry out experiments on aerobic respiration
Respiration by living organisms can be investigated by carrying out experiments to show the production of carbon dioxide and heat.
Investigating carbon dioxide production
Limewater turns milky in the presence of carbon dioxide. It can be used to show that exhaled air contains more carbon dioxide than inhaled air.
Carbon dioxide dissolves in water to form a weakly acidic solution. Hydrogen carbonate indicator is used to show the presence of carbon dioxide in solution. It is:
- red at neutralpH (no carbon dioxide)
- yellow at low pH (carbon dioxide present)
Investigating heat production
The release of heat can be shown by carrying out an experiment using germinating seeds. Two vacuum flasks are used:
- one containing living plant material
- one containing dead plant material (the control)
| Contents | Start temp (°C) | End temp (°C) | Temp change (°C) |
|---|---|---|---|
| Living plant material | 21 | 29 | 8 |
| Dead plant material | 21 | 21 | 0 |
Factors which Affect the Rate of Respiration
Describe factors which affect the rate of respiration
The rate of respiration in organisms is rarely constant. There are several factors in that affect rate of respiration. These apply equally to aerobic and anaerobic respiration although the examples given here refer to aerobic respiration
- Temperature: Respiration is a chemical process therefore its rate increases with increasing body temperature as an increasing in temperature increases the rate of chemical change.
- Activity: All body activity requires energy. When an organism becomes active it requires more energy than when it’s inactive. Since respiration provides energy required for the activity the rate of respiration will correspondingly increase.
- Body Size: Small organisms have high surface area to volume ratio. Heat loss occurs at the surface; therefore small organisms tend to lose heat more rapidly than larger ones. Small animals e.g. shrews, have to maintain higher rate of respiration than larger ones to maintain their body temperature.
- Age: Young organisms are growing and as a result require more energy than older mature individual whose growth may slow down or stopped. Younger individual tend to be more physically active also. Both of these rate factors lead to increased rates of respiration in younger organism
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