2.40B -2.50 - Gas Exhange Flashcards
What is diffusion?
Diffusion is the movement of molecules from a region of its higher concentration to a region of its lower concentration
Molecules move down a concentration gradient, as a result of their random movement
What process does gas exchange occour by?
Diffusion is the process by which gas exchange occurs
Single celled organisms, such as amoeba, can exchange gases sufficiently by simple diffusion through the cell membrane
How does gas exchange take place in plants and animals?
Multicellular organisms (such as plants and animals), however, have exchange surfaces and organ systems that maximise the exchange of materials
Gills are the gas exchange organs in fish, lungs in humans and leaves or roots in plants
These organs increase the efficiency of exchange in a number of ways:
Having a large surface area to increase the rate of transport
A short diffusion distance for substances to move across. This short distance is created because the barrier that separates two regions is as thin as possible
What adaptions do animals have for Gas exchange?
Gas exchange surfaces that are well ventilated to maintain steep concentration gradients
How Gas Exchange occour during photosynthesis?
Plant cells photosynthesize when there is enough sunlight
The process requires the uptake of carbon dioxide and the release of oxygen
The carbon dioxide diffuses down the concentration gradient from a region of high concentration (outside the leaf) to a region of low concentration (inside the leaf)
The cells use carbon dioxide in photosynthesis so the concentration is always low inside the photosynthesizing cells
The oxygen diffuses down the concentration gradient from a high concentration (inside the leaf) to a low concentration (outside the leaf)
Gas exchange in photosynthesis, downloadable IGCSE & GCSE Biology revision notes
How is the leaf structure adapted to photosynthesis?
The structure of the leaf is adapted to carry out both photosynthesis and gas exchange
The different cell types (palisade mesophyll, spongy mesophyll etc.) and tissues are arranged in a specific way to facilitate these processes
What are the 3 key gases involved in Gas exchange?
Carbon dioxide - released in respiration but used in photosynthesis
Oxygen - released in photosynthesis but used in respiration
Water vapour - released in respiration and transpiration
What are the adaptions of the whole leaf for gas exchange?
They are thin which gives a short diffusion distance
They are flat which provides a large surface area to volume ratio
They have many stomata which allow movement of gases in and out of the air spaces inside the leaf to maintain a steep concentration gradient
Other adaptations of the internal leaf structure/tissues include:
Air spaces to allow gas movement around the loosely packed mesophyll cells
Many stomata in the lower epidermis open in sunlight to allow gas movement in and out of the leaf
Thin cell walls allow gases to move into the cells easily
Moist air which gases can dissolve into for easier movement into and out of cells
The close contact between the cells and the air spaces allows efficient gas exchange for photosynthesis and respiration
What are stomate and what their functions?
Stomata are spaces found between two guard cells predominantly on the lower epidermis of the leaf
The guard cells are responsible for the opening and closing of the stomatal pore which controls gas exchange and water loss
Stomata open when water moves (by osmosis) into the guard cells causing them to become turgid
This allows gases to diffuse in and out of the leaf through the stomatal pore
Stomata tend to open when there is plenty of water and sunlight
Stomata close when the guard cells lose water (by osmosis) to the neighbouring epidermal cells and they become flaccid
This prevents any diffusion into or out of the leaf
Stomata tend to close due to low water availability or low sunlight
How does Gas exchange occour during the day in plants?
During the daytime plants both respire and photosynthesize
The rate of photosynthesis tends to be higher than the rate of respiration (unless there is a low light intensity)
Therefore there is net diffusion of carbon dioxide into the plant and net diffusion of oxygen out of the plant during the day
How does Gas exchange occour in a plant at nighttime?
During the nighttime, plants only respire
This means that there is a net movement of oxygen into the plant and net diffusion of carbon dioxide out of the plant during the night time
At low light intensities, the rate of photosynthesis is equal to the rate of respiration
This means that there is no net movement of oxygen or carbon dioxide in either direction
What is the gas exchange surface in humans?
The lungs are the gas exchange surface in humans
All gas exchange surfaces have features in common which allow the maximum amount of gases to be exchanged across the surface in the smallest amount of time
What are the adaptions of the Lung for gas exchange?
Large surface area to allow faster diffusion of gases across the surface
Thin walls to ensure diffusion distances remain short
Good ventilation with air so that diffusion gradients can be maintained
Good blood supply to maintain a high concentration gradient so diffusion occurs faster
What is the breathing structure in the human body?
What are the Cilia and the mucus
The passages down to the lungs are lined with ciliated epithelial cells
Cilia cells have tiny hairs on the end of them that beat and push mucus up the passages towards the nose and throat where it can be removed
The mucus is made by special mucus-producing cells called goblet cells because they are shaped like a goblet, or cup
The mucus traps particles, pathogens like bacteria or viruses, and dust and prevents them from getting into the lungs and damaging the cells there
Show how the body changes during breathing in?
Show how the body will change during breathing out?
