Bio2

• concept of gas exchange is movement of gases across a cell membrane
• concept of gas exchange is essential prerequisites of life
• concept of gas exchange is taking in O2, producing CO2
• Respiration is the process by which organisms acquire oxygen for metabolism
• Diffusion across a moist membrane is the basic mechanism of gas exchange. From low to high gradient concentration
• green plants need a supply of carbon dioxide and a means of disposing oxygen
• in aquatic plants water passes among the tissues providing a medium for gas exchange
• in terrestrial plants air enters the tissues and the gases diffuse into the moisture bathing the internal cells
• leaves are specific plant organ where gas exchange happens in plants
• stomata allow gas exchange between surrounding air and photosynthetic cells inside the leaf
• stomata regulates CO2 uptake and avenues for evaporative loss of water
• stomata is flanked by two guard cells that regulate its opening and closing
• mesophyll is the lower and upper epidermal layer of leaves
• mesophyll consists of parenchyma cells that are for photosynthetic functions
• parenchyma cells have labyrinth of air spaces where CO2 and O2 circulate
• air spaces of parenchyma cells are in the vicinity of the stomata
• palisade mesophyll is one or more layers of elongated parenchyma cells on the upper part
• spongy mesophyll is below the palisade
• roots take O2 from the air present in soils
• Root hair is the root epidermal cell extension which contacts indirectly with the soil
• Respiration occurs by diffusion of o2 and CO2 through root hairs
• Diffusion of o2 and disposal of CO2 happens in root hair
• stems consists of lenticels
• lenticels are found in small area of a bark which allows gas exchange between air and living cells of the woody stem
• Leaves use water and mineral nutrients from the roots in photosynthesis to produce food in the form of glucose
• roots absorb water and minerals through root hairs
• plants have pipe that allow transport of these absorb nutrients through vascular tissues
• types of vascular tissues: xylem and phloem
• xylem is the continuous network of channels connecting roots to leaves through stem
• xylem transport water and nutrient to the entire plant
• phloem are tissues that transport sugars from leaves down to the rest of the plant
• transpiration is the release of water
• evaporation of water exist through stomata in the leaves
• transpiration generates a suction pull pulling the water to great heights in tall trees
• transpiration cools the plants
• homeostasis is theself-regulating mechanism that ensures that an organism’s body is at equilibrium
• goal of homeostasis is maintenance of equilibrium (set point)
• stimulus is the change in either internal or external environment which is detected by a receptor
• response of the body is usually moving back the internal state to its set point
• homeostasis is related to the concept of osmoregulation