Back to B1 Home
B1 O) Exchanging Substances – Part 2
B1 O) Exchanging Substances – Part 2
The content in this section builds on the content that was discussed in the previous section – click here to be taken to the content in the previous section.
Plants
Leaves are adapted for the efficient exchange of certain substances. The diagram below shows the structure of a leaf.
Leaves are adapted for the efficient exchange of certain substances. The diagram below shows the structure of a leaf.
Plants undertake photosynthesis which is where they reaction carbon dioxide and water to produce glucose and oxygen (the equation for photosynthesis is: carbon dioxide + water –> glucose + oxygen). The majority of photosynthesis in plants takes place in the leaves. In order for photosynthesis to take place, the plant needs carbon dioxide and water. The water for photosynthesis comes from the roots to the leaves via the xylem vessels. The carbon dioxide for photosynthesis enters leaves through tiny holes on the bottom of leaves called stomata. The carbon dioxide enters leaves by diffusion (diffusion is where particles move from an area of high concentration to an area of low concentration).
Oxygen (the waste product of photosynthesis) and water vapour diffuse from the inside of leaves to the outside of leaves through the stomata. This happens because oxygen and water vapour are in a higher concentration inside the leaves compared to outside the leaves. The loss of water from leaves is known as transpiration.
Each stoma is surrounded by two guard cells, which change their shape to change the size of the stoma. The size of the stomata depends on a variety of different factors such as light intensity, time of day and quantity of water. Larger stomata results in a greater amount of gas exchange of the three gases (carbon dioxide, oxygen and water vapour). Smaller stomata results in a lower amount of gas exchange.
Leaves contain air pockets. The air pockets increase the surface area of the plant cells with the air pockets, which means that a greater amount of gas exchange takes place as there is a greater surface area for gases to exchange. This means that there will be a greater rate of diffusion of carbon dioxide into plant cells from the air pockets, which can allow more photosynthesis to take place.
Oxygen (the waste product of photosynthesis) and water vapour diffuse from the inside of leaves to the outside of leaves through the stomata. This happens because oxygen and water vapour are in a higher concentration inside the leaves compared to outside the leaves. The loss of water from leaves is known as transpiration.
Each stoma is surrounded by two guard cells, which change their shape to change the size of the stoma. The size of the stomata depends on a variety of different factors such as light intensity, time of day and quantity of water. Larger stomata results in a greater amount of gas exchange of the three gases (carbon dioxide, oxygen and water vapour). Smaller stomata results in a lower amount of gas exchange.
Leaves contain air pockets. The air pockets increase the surface area of the plant cells with the air pockets, which means that a greater amount of gas exchange takes place as there is a greater surface area for gases to exchange. This means that there will be a greater rate of diffusion of carbon dioxide into plant cells from the air pockets, which can allow more photosynthesis to take place.
Fish Gills
There are two gas exchanges that take place in gills. The first is that oxygen enters the bloodstream from water – the oxygen is then used for respiration reactions. The second is that carbon dioxide leaves the bloodstream and enters water – carbon dioxide is a waste product of respiration. Water enters fish through their mouths and passes out of them through their gills; the gills are where gas exchange takes place
There are two gas exchanges that take place in gills. The first is that oxygen enters the bloodstream from water – the oxygen is then used for respiration reactions. The second is that carbon dioxide leaves the bloodstream and enters water – carbon dioxide is a waste product of respiration. Water enters fish through their mouths and passes out of them through their gills; the gills are where gas exchange takes place
The gills are made up of many gill filaments and each of these gill filaments are covered in lamellae. The gills and the lamellae give the fish a very large surface area for efficient exchange of gases. Capillaries pass very close to all of the lamellae. There are only a few cells between the lamellae and the capillaries, which means that the distances that the gases have to travel is short, thus resulting in a fast rate of diffusion.
Water and blood flow in opposite directions to each other when they pass through the gills. This ensures that there is a large concentration difference for oxygen and carbon dioxide between the bloodstream and water.
There is a wide variety of different fish in oceans and lakes. Faster moving fish tend to have more gills than slower moving fish. This is because faster moving fish will be undertaking more respiration reactions and will therefore need more oxygen. Oxygen is taken into the bloodstream through the gills, so as faster moving fish need more oxygen, they will have more gills/ longer gills than slower moving fish.