Biology Form Two Notes – Gaseous Exchange

These Biology Form Two notes cover Gaseous Exchange. The material is organised in clear sections for easier reading, understanding and revision.

Gaseous Exchange

The Concept of Gaseous Exchange

Organs Responsible for Gaseous Exchange in Living Organisms Identify organs responsible for gaseous exchange in living organisms

Organs responsible for gaseous exchange in living organisms include the following:

ORGANISM RESPIRATORY SURFACE

Amoeba Cell membrane

Insects Tracheal system

Spider Book lung

Fish Gills

Plants Leaves, stems, roots Amphibians Skin, gills and lungs Mammals Lungs

Birds Lungs

reptiles Lungs

Features of Respiratory Surface

They are thin to reduce diffusion distance

They are moist to dissolve gaseous so that they dissolve and diffuse in solution form

They are highly braced, folded or flattened in order to increase the surface area for gaseous

exchange

4. They are close to efficient transport and exchange easily by the cells

5. They are well ventilated so that gaseous passes easily

The Concept of Gaseous Exchange

Explain the concept of gaseous exchange

Gaseous exchange refers to the movement of oxygen and carbon dioxide across the respiratory surface. Is the process through which respiratory gaseous are passed through the respiratory surface. Respiratory surface are specialized organs for gaseous exchange. Gaseous exchange

takes place through a process of diffusion.

Gaseous Exchange in Mammals

Parts of the Respiratory System Identify parts of the respiratory system

The gaseous exchange in mammals takes place in the lungs.

7 Paranasal sinuses Nasal cavity

Oral cavity ae Nostrils Pharynx

Epiglottis Larynx

• i
• 3
• i
• 5

Trachea (Windpipe) – Left primary bronchus

• Right primary bronchus. nN Alveoli
• Superior lobe- Bronchl
• Superior lobe
• Middle lobe-
• ‘Bronchioles

Inferior lobe ——————-— Inferior lobe

Lower Respiratory Tract

Diaphragm

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.

Gaseous Exchange in the Alveolus

• Carbon dioxide to be
• exhaled
• Oxygen-rich blood
• Inhaled oxygen (which will go
• S back to the
• alveolus. ry heart and enter
• 4 the systemic

Deoxygenated blood circulation)

carrying carbon dioxide

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

Altitude

Gaseous Exchange in Plants 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

cuticle upper epidermis cells

palisade mesophyll cells

spongy mesophyll cells. sub-stomatal air space

lower epidermis cells

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 (CO-) 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

3. Plants obtain oxygen which is necessary for production of energy which is produced during

respiration through gaseous exchange

Respiration

The concept of Respiration

Explain the concept of respiration Respiration: Is the metabolic activity or reaction in which complex food substances are broken

down step by step to release energy within a cell

Cellular Respiration:Is a set of metabolic reaction and process that takes place in the cell of

organisms to convert biochemical energy from nutrients into ATP.

NB: The reaction involved is catabolic reaction, which breaks larger molecules into smaller ones to release energy. Cellular respiration is considered as exothermic reaction. Exothermic reaction

is the process whereby energy is released out.

Types of Respiration

Mention types of respiration

There are two types of respiration

Aerobic Respiration

Anaerobic Respiration

Aerobic Respiration

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 C6Hi20.,

Aerobic respiration — In the presence of oxygen glucose molecules are broken down into carbon

dioxide water and energy

.

Equation of Aerobic respiration

CoH120¢ + 602 6CO> + 6H20 + 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-Pamas Pathway). This process does not require O2although 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 CO2and 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 (C2HSOH) and CO2without 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 tums 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)

9 Airin >

ti

a tT

Sodium hydroxide [i Indicator Respiring Indicator solution (absorbs turns red organisms turns yellow

carbon dioxide)

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

Dead plant material 21

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

An Aerobic Respiration

The Concept of Anaerobic Respiration

Explain the concept of anaerobic respiration

This is the process whereby energy is released in absence of oxygen although the energy outcome in anaerobic respiration is much less than aerobic respiration. Anaerobic respiration differs in plant and animal

Anaerobic Alcoholic fermentation in plant cell and yeast

Anaerobic lactic fermentation

The Mechanism of Anaerobic Respiration Outline the mechanism of anaerobic respiration

Anaerobic respiration differs in plant and animal. Anaerobic Alcoholic fermentation in plant cell and yeast

Anaerobic lactic fermentation

Anaerobic Alcoholic fermentation in plant and yeast

In the presence of Alcoholic fermentation glucose molecule is broken down into ethanol and

carbon dioxide and energy. Glucose — Ethanol + Carbon dioxide + Energy C6H1206 — 2C2HsOH + 2CO2 + 2 ATP

Raw Material — End Product Anaerobic Lactic Fermentation

If there is lack of oxygen carbohydrate molecule is broken down to lactic acid and energy

outcome only 2ATP.

C6H120¢ (Gtucosey—> C3603 + 2ATP Energy (Lactic Acid)

Raw Material — End Product

‘A more common occurrence of lactic acid fermentation is in muscles; during exercise. During this period the respiratory surface is incapable of supplying oxygen to the molecule, which is requirement. Hence due to this lactic acid is produced. Accumulation of lactic acid will cause

muscle cramp and so prevent muscles from operating.

The End Products of Anaerobic Respiration

Mention the end products of anaerobic respiration

The following are the End Product of Anaerobic Respiration: In plants

Ethanol

Carbon dioxide

Energy

In Animals

Lactic Acid

Energy (2ATP) Importance of Anaerobic Respiration

This process brings about fermentation. Fermentation occurs when simple sugar (glucose) is

broken down by bacterial in absence of oxygen Bacteria break down milk sugar to reduce lactic acid Production of composite manure

Oxygen debt

During heavy exercise, oxygen supply is less than what is required by the body. As a result of

anaerobic respiration taking place and lactic acid accumulates. This creates oxygen deficit

Oxygen debt refers to the amount of oxygen required to convert lactic acid into carbon dioxide,

water and energy.

An Experiment to Demonstrate the Application of Anaerobic Respiration Carry out an experiment to demonstrate the application of anaerobic respiration

Application of Anaerobic respiration in industry and home Alcohol brewing e.g. making beer and wine

Production of acetic acid and other acid such as citri Production of biogas from cooking and lighting

Bread making process

Production of composite manure

The Difference Between Aerobic Respiration and Anaerobic Respiration

Distinguish between aerobic respiration and anaerobic respiration

Differences between Aerobic Respiration and Anaerobic Respiration include the following

Aerobie Respiration

Oxygen is used up

Larger amount of energy is released Water molecules are produced

Takes place in mitochondria

Anaerobic Respiration

Oxygen is not used

Less amount of energy is released

Water molecules are not produced

Takes place in cytoplasm

Products produced are not harmful Products produced are harmful example lactic acid

Infection and Diseases of the Respiratory System Common Airborne Infections and Diseases which Affect the Respiratory System

Mention common airborne infections and diseases which affect the respiratory system There are several airborne infections, which affect the human respiratory system. The common

ones are influenza, pneumonia, common cold and tuberculosis.

Most of the airborne infections are a result of close contact with an infected person. When the

sick person breathes out, coughs or sneezes, the pathogens are released into the air

Airbome infections can be controlled by isolation of the infected patients, proper disposal of infected secretion such as sputum, living in a well-ventilated house and avoiding overcrowding

especially in bedrooms.

The Causes, Symptoms, Effects and Control Measures of Common Infections

and Diseases of the Respiratory System

Explain the causes, symptoms, effects and control measures of common infections and diseases of the respiratory system

Airborne infections can be controlled by isolation of the infected patients, proper disposal of infected secretion such as sputum, living in a well-ventilated house and avoiding overcrowding

especially in bedrooms.

Disorders of the Respiratory System

Disorders of the Respiratory System

Mention disorders of the respiratory system

Disorders of the Respiratory System include the following: PNEUMONIA

Bronchitis

Asthma

Lung Cancer

Emphysema

Tuberculosis

Causes, Symptoms and Effects of the Disorders of the Respiratory System

Explain causes, symptoms and effects of the disorders of the respiratory system

Pneumonia

Pneumonia is inflammation of the lung. It is caused by bacteria, viruses, fungi or by inhaling chemical toxins or irritants. Pneumonia is normally followed by other illnesses such as cold or

flu.

SIGNS AND SYMPTOMS OF PNEUMONIA

Fever

Chills

Shortness of breath associated with pain Increase of mucus production

Cough

Prevention And Treat! 'T Of Pneumonia

Staying warm

Avoiding overcrowded areas

Avoiding cold food and drinks, hot drinks are preferred more as they loosen secretions

Get treatment as early as possible since it is curable by antibiotics

Bronchitis

Bacteria, viruses and inhaling of irritating substances can cause the lining of the respiratory system to become inflamed. This causes an infection called bronchitis. Bronchitis can be acute or

chronic.

ACUTE BRONCHITIS

This is caused by whooping cough or recurrent attacks of influenza; smoking can also cause

acute bronchitis.

SIGNS AND SYMPTOMS OF ACUTE BRONCHITITS

Pain in the chest

Rapid breathing

Fever

Coughing

Headache CHRONIC BRONCHITIS

Heavy smoking and recurrent acute bronchitis cause chronic Bronchitis.

SIGNS AND SYMPTOMS OF CHRONIC BRONCHITIS

Coughing with the production of thick sputum

Breathing difficulties PREVENTION AND TREATMENT OF CHRONIC BRONCHITIS

Avoiding smoking

Avoid very smoky or dusty areas

Live in a well-ventilated house

Keep your body warm

Seek medical help

Asthma

Asthma is characterized by inflamed and constricted airways. The narrowing of the airways restricts the flow of air into the lungs.

Asthma can be caused by:

Allergic reactions to dust, pollen, spores or animal fur Herediroty diseases of the respiratory system Extremely cold weather

Frequent viral or bacteria lung infection

Signs And Symptoms Of Asthma

Narrowing of bronchioles resulting in breathing difficulties and a wheezing or hissing sound

when breathing

Coughing

Shortness of breath

Excessive production of mucus

Dilation of blood vessels leading to low blood pressure, low blood pressure can be fatal

Chest tightness PREVENTION AND TREATMENT OF ASTHMA

Avoid allergens (things that cause allergenic reaction)

Get treatment for respiratory infections as early as possible Keep the body warm

Muscle relaxants in the form of sprays, pills and injections are used to prevent the narrowing of

bronchitis

Lung Cancer

The main cause of lung cancer is smoking. The nicotine in cigarette smoke stops the cilia in the

trachea from expelling foreign materials leading to respiratory infection. SIGNS AND SYMPTOMS OF LUNG CANCER

Chest pain

Breathing difficulty

Weight Loss

Persistent Cough

Abnormal Production of Mucus PREVENTION AND TREATMENT OF LUNG CANCER

Stop smoking

There is no cure for cancer. However chemotherapy and physiotherapy are used to control the

disease

Emphysema

This is a lung disease, which results from destruction of the structure supporting the alveoli

leading to these collapse. This significantly reduces the surface area available for gaseous

exchange. CAUSES OF EMPHYSEMA Mainly cigarette smoke

Air pollution

Hereditary Old age

SIGNS AND SYMPTOMS OF EMPHYSEMA

Shortness of breath

Coughing

Obstructive lung disease

Difficulties when breathing especially during exercise

Wheezing during breathing PREVENTION AND TREATMENT OF EMPHYSEMA

Avoid cigarette smoking and exposure to smoke Lung surgery is usually done to relieve the symptoms Use of medical drugs

In severe cases, lung transplant is necessary

Tuberculosis

Tuberculosis is highly infections disease. The causal organism for TB is one of the strains of bacteria belonging to the Mycobacterium tuberculosis. Tuberculosis can be spread from one

person to another person, when the bacteria become airborne. 'S AND SYMPTOMS OF TUBERCULOSIS

Cough

Fever

Weight Loss

Loss of appetite

Disorders of the Respiratory System and HIV/AIDS

Relate disorders of the respiratory system and HIV/AIDS

Tuberculosis is the most common opportunistic infection associated with HIV worldwide. Tuberculosis is an infection by the tuberculosis bacterium that predominantly affects the lungs, but it can spread through the blood and lymph nodes to the rest of the body in people with HIV.

The disease can strike people with HIV no matter what the level of the CD4 count, which means

that TB can often occur years before other problems associated with HIV develop. Pneumocystis Carinii Pneumonia (PCP)

This is the most common opportunistic infection that occurs with AIDS the fungus that causes the PCP infection is spread through breathing or coughing. Symptoms include cough, fever,

trouble breathing and loss of weight.

Cryptococci Meningitis

This is caused by fungus and it is the most common central nervous system infection associated with HIV. Meningitis is an inflammation of the membranes and fluid surrounding the brain and

spinal cord.