Lesson 5 Flashcards
Describe the process of inspiration
• External intercostal muscles contract, raising ribs up and out
• Outer pleural membrane pulled outwards, reducing pressure in pleural cavity
• Lung surface also drawn out, causing alveoli to expand
• Air moves into body and eventually to alveoli as pressure in alveoli is lower than atmosphere
Describe what happens during expiration
• External intercostal muscles relax, moving ribs down and in
• Outer and inner pleural membrane move inwards
• Lungs move in and alveoli deflate so air moves out
Explain how alveoli are adapted for gas exchange
• Many alveoli - Large SA
• Moist - So gasses dissolve and diffuse more easily
• One-cell thick walls - Short diffusion distance
• Extensive capillary network - conc. grad. is maintained
What adaptations does the leaf have?
• Leaf blade is flat and thin - light can pass through
• Lots of open space is spongy mesophyll cells for diffusion of gases
• Mesophyll walls are moist - Gases can diffuse
• Stomatal pores can open to let gases in
How is leaf adapted for photosynthesis?
• Leaves can orientate themselves toward sunlight
• Thin to allow sunlight to pass through
• Has densely packed palisade cells meaning it can fit many cells in leaf and each cell has many chloroplasts, making light absorbed efficiently used
• Chloroplasts can also rotate and move
Why do turgid guard cells open the stomata?
Inner cell wall is thicker and outer cell wall thinner
Describe mechanisms for stomata opening
• Potassium ions actively transported into guard cells
• Starch in guard cells converted to malate which is soluble
• All these processes lower water potential so water enters via osmosis
