Properties of Gas exchange+ adaptations of the human lung and fick's law

Question 1

Surface area to volume ratio

Answer 1

-A larger surface area to volume ratio allows more space for substances e.g oxygen and CO2 to diffuse in at the same time, therefore increasing the efficiency of gas exchange
-Organisms that rely on diffusion increase their surface area through structural adaptations
-For example in the human lungs; there are millions of alveoli (tiny sacs) that increase the surface area for gas exchange
-This is particularly important in single-celled organisms, as they solely rely on diffusion through their outer membrane for the exchange of substances

Question 2

Thickness of exchange surface

Answer 2

-Diffusion is a slow process across a long distance
-Thin exchange surfaces create short diffusion paths which allow gas molecules to reach their destination quicker, increasing the efficiency of gas exchange
-Gas exchange surfaces are often one cell thick; for example in the lungs, the alveolar and capillary walls are one cell thick, which allows oxygen to diffuse out of the lungs and into the blood quickly and allows CO2 to diffuse out of the blood and into the lungs quicky

Question 3

Concentration gradient

Answer 3

-The greater the difference in concentration between two areas, the faster the rate of diffusion
-A steep concentration gradient maintains a continuous diffusion of gas
-For example in the lungs; alveoli have a higher oxygen concentration than the blood- oxygen diffuses from the lungs into the blood
-The blood has a higher concentration of CO2 than the lungs- CO2 diffuses out of the blood and into the lungs
-Steep gradient is maintained by ventilation (breathing) which constantly replenishes the alveoli with oxygen, and blood flow; where capillaries carry gases away to maintain the concentration gradient

Question 4

Diffusion

Answer 4

-Diffusion is the net movement of particles from a region of high concentration to a region of low concentration through a partially permeable membrane
-Diffusion is a passive process, meaning it does not need metabolic energy to take place

Question 5

Other factors affecting diffusion

Answer 5

-PARTICLE SIZE/CHARGE
-Very small particles can easily diffuse across a membrane
-Non-polar molecules can easily diffuse across a membrane
-TEMPERATURE
-In warmer conditions, particles have more kinetic energy and diffuse across a membrane faster than in cold conditions

Question 6

Fick’s Law of diffusion

Answer 6

Fick’s law of diffusion states that a steep concentration gradient, a short diffusion distance, and a high surface area, all maximise the rate of diffusion
-FORMULA
-Rate of diffusion = surface area x concentration gradient/ diffusion distance

Question 7

Adaptations of the mammalian lung

Answer 7

HIGH SURFACE AREA
-There are millions of alveoli (tiny sacs) in the lungs, which provide a large surface area for gas exchange
-Large surface area = faster rate of diffusion
SHORT DIFFUSION DISTANCE
-Alveoli and capillary walls are just one cell thick
-This provides a short diffusion distance for oxygen to diffuse out of the lungs and into the blood and for the removal of CO2 from the blood
-Short diffusion distance = faster rate of diffusion
STEEP CONCENTRATION GRADIENT
-Steep concentration gradient in the lungs is maintained by ventilation (breathing) as the alveoli are constantly replenished with oxygen, and blood flow, where capillaries carry oxygen away from the lungs and bring CO2 from the tissues, maintaining the concentration gradient
-Steep concentration gradient= faster rate of diffusion
RICH BLOOD SUPPLY
-In the lungs, there is a rich blood supply, as the alveoli are surrounded by a dense network of capillaries
-Blood flow is constant, helping to maintain the concentration gradient
-This ensures that oxygen is constantly delivered to tissues and the removal of CO2