CH 2 Flashcards
Explain opening mechanism of stoma due to K+ ions// sucrose concentration
K+ ions enter the guard cell by active transport OR Photosynthesis occur
Concentration of solutes in guard cell become high OR concentration of sucrose in guard cells become high
Water potential in guard cell decreases
water diffused into guard cell by osmosis from adjacent cells
Guard cells become turgid and curve outwards
Stoma opens
Explain closing mechanism of stoma due to K+ ions// sucrose concentration
K+ ions move out of guard cells by active transport OR Photosynthesis does not occur without light and sucrose is converted into starch
Concentration of solutes//starch in guard cells decrease
Water potential of guard cell increase
water diffuses into adjacent cells out of the guard cells by osmosis
Guard cells become flaccid
Stoma close
Importance of transpiration
Allow roots to absorb water and mineral salts from soil
Produce cooling effect
Produce pulling force that moves water and mineral salts in xylem
Factors that increase rate of transpiration
High light intensity; high rate of photosynthesis and stoma is open
Low relative air humidity; concentration of water vapour in spaces between cells is higher then in atmospher
High temperature; high kinetic energy of water vapout
faster air movement; more water vapour around stomata is blown away
Adaptations of leaf for photosynthesis
Transparent cuticle and epidermal cells to allow sunlight to reach palisade mesophyl
Palisade mesophyl cells are arranged tightly together and packed with chloroplast to absorb maximum sunlight
Spongy mesophyl contain air spaces to allow efficient gaseous exchange during photosynthesis
Stoma are present in lower epidermis to open in the presence of light and allow gaseous exchange to occur
3 Structure of a chloroplast
Thylakoid, contain chlorophyll & site for light-dependent reaction
Granum, a stack of thylakoid
Stroma, colorless fluid around granum & site for light-independent reaction
Light dependent reaction of photosynthesis
Photolysis occur; water molecule is broken down to form Hydrogen ions and Hydroxide ions in the presence of light energy/and chlorophyll
Light energy absorbed by chlorophyll in thylakoid excites electrons in the chlorophyll and raise the electrons to a higher energy level
Excited electrons go through a series of electron carriers
Energy from the electron is used to produce ATP molecules
The electrons is received by the last electron recipient which is NADP+
NADP+ combines with H+ to form NADPH, a reducing agent
Hydroxide ions loses electrons to form water and oxygen gas
Light-independent reaction of photosynthesis
5 Carbon organic compound fix carbon dioxide to form 6-Carbon organic compound
NADPH and ATP reduces 6-carbon organic compound to glucose monomers
Factors that increase rate of photosynthesis
Increasing light intensity; More sunlight can be absorbed
Increasing//optimum temperature
Increasing concentration of carbon dioxide
