BIOL1050 Gas exchange

week 5 SDL

Why is gas exchange important?

It is neccessary for respiration and photosynthesis in autotrophs (plants) and heterotrophs (animals).

what are the main gases in earth’s atmosphere?

nitrogen (79%), oxygen and a small amount of Co2

What is nitrogen used for

Nitrogen supports plant growth through the nitrogen cycle, which is how nitrogen moves through the world. nitrogen fixation, nitrogen is turned into ammonia or ammonium which is then turned into nitrates

importance of oxygen

oxygen is vital for respiration

importance of co2

co2 is vital for photosynthesis to create oxygen and glucose

define ‘diffusion’

the movement of particles from high to low conc. Driven by random motion and does not require ATP

define ‘partial pressure’

the proportion of pressure in a mixed gas coming from a single gas

define ‘gradient’

the different conc. Of molecules from one place to another,  gradient is the difference in something between two places

how do pressure gradients drive the movement of gases?

molecules will move from areas of higher conc to lower conc, so for example when blood returns for the muscles it has a lower concentration of oxygen, so oxygen is diffused down the conc gradient till the blood reaches equalibrium with oxygen levels in the alveoli

what are the challenges with aquatic respiration?

although partial pressure remains the same, there is a lot less oxygen molecules available underwater, so it is more difficult for sea creatures to consume enough oxygen.

what are specialised systems that make this easier?

Gills: ram ventilation (swimming with mouth open), coordinated movement of jaw and gill cover to pump water over the gills

Function of lamellae"?

lamellae line gill filaments, and are lined with capillaries which create a large surface area for gas exchange. Water flows over lamellae in the opposite direction of blood flow maintaining a concentration gradient

Nasal cavities function

filter air

Pharynx

shared space for food and air

Larynx

voice production

Trachea

tube connecting larynx and bronchi

bronchi

airway before lung

Bronchioles

muscular tubes that constrict/dilate

Alveoli

site of gas exchange, covered in capillaries

Lungs

organs that facilitate gas exchange

Diaphragm

muscles underneath lungs to facilitate breathing

how does the alveoli contribute to gas exchange?

The alveoli has a high surface area and is thin so gas can diffuse easily, also covered in water molecules which help diffusion

role of surfactant?

Water molecules on alveoli can be create surface pressure which causes them to be attracted to each other and cause the alveoli to fall inwards - surfactant (made of proteins and phospholipids) stops this by breaking hydrogen bonds

what is negative pressure breathing?

when air is pulled into the lungs - inhalation, when the pressure inside the chest drops below the pressure of the outside air

positive pressure breathing

when air is pushed into the lungs e.g. mechanical ventilators - pressure inside the lungs is higher than outside

Lung Volume

the amount of air in your lungs during different stages of breathing

Lung volume includes:

Tidal volume: air moved in and out in normal breathing, Inspiratory reserve volume: Extra air you can forcefully inhale after a normal quiet inspiration

Expiratory reserve volume: Extra air you can forcefully exhale after a normal quiet expiration

Residual volume: Air left in the lungs after a maximal, forceful expiration

Lung capacity defintion

The total amount your lungs can hold during different stages of breathing

Lung capacity includes:

Vital capacity: max amount of air that can be exhaled after a maximal inhalation

Total lung capacity: max amount of air that the lungs can contain following max inhalation

Describe the movement of oxygen and carbon dioxide

gas is exchanged between atmosphere and the blood,  between blood (alveolar wall) and tissue cells of the body (capillary wall). This movement is determined by the partial pressure gradient.

Movement of oxygen in the blood?

02 moves down the partial pressure gradient from alveoli (high partial pressure) to tissue cells, and then vice versa and then back to the atmosphere.

Movement of co2 ?

Co2 moves from tissues to the blood to lungs to atmosphere.

How does blood arrive at capillaries?

Blood arriving at capillaries is deoxygenated blood, which means it is low in 02 and higher in co2. Once the blood reaches equalibrium, it moves through pulmanory veins to the heart and then through systemic arteries to the rest of the body.

importance of haemoglobin?

02 has low water solubility, so it is transported by haemoglobin in red blood cells. As Po2 decreases, haemoglobin releases 02 into the tissues.

how does co2 relate to bicarbonate?

Some co2 is moved by haemoglobin, but majority is converted in bicarbonate, this also produces H+, which decreases blood ph.

what is the bohr effect?

is a physiological phenomenon where an increase in carbon dioxide (\(\text{CO}_{2}\)) or a lower blood pH (higher acidity) reduces hemoglobin's affinity for oxygen, helping to release oxygen into active tissues