TOPIC 5: GASEOUS EXCHANGE AND RESPIRATION | BIOLOGY FORM 2
The Concept of Gaseous Exchange
Gaseous Exchange in Mammals
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
- 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
- Altitude
Gaseous Exchange in Plants
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.
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.
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.
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.
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.
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 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
Aerobic Respiration
is the combustion reaction. This means that oxygen is required in order
to generate ATP. The simplified reaction of respiration of
carbohydrates is C6H12O6.
C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy (38ATP)
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 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
(C2H5OH) and CO2without the help of any cell organelle. This process is
called anaerobic respiration.
by living organisms can be investigated by carrying out experiments to
show the production of carbon dioxide and heat.
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 weaklyacidicsolution.
Hydrogencarbonate indicatoris 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 usinggerminatingseeds. Twovacuum flasksare used:
- one containing living plant material
- one containing dead plant material (thecontrol)
| 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
YOU MUST ALSO READ THIS
