biology chapter 6 Flashcards
define photosynthesis
Photosynthesis is the process by which green plants use the energy from sunlight to synthesize nutrients from carbon dioxide and water. Photosynthesis in plants generally involves the green pigment chlorophyll and generates oxygen as a by-product.
what are the inputs of photosynthesis
carbon dioxide and water
what are the outputs of photosynthesis
glucose and oxygen
what is the word equation of photosynthesis
carbon dioxide + water —–> glucose + oxygen
what is the balanced equation for photosynthesis
6CO2 + 6H2O → C6H12O6 + 6O2
how do we test for the presence of starch
to test for the presence of starch in a leaf
- remove the green leaf from a plant that has been exposed to sunlight for a few hours.
- immediately put the leaf in boiling water for two minutes
- put the boiled leaf in a boiling tube containing some alcohol or ethanol. place the boiling tube in a beaker of hot water
- the leaf is now very brittle. gently remove the leaf and put it back into the hot water. this softens the leaf and makes it more permeable to iodine solution
- remove the leaf and spread it evenly on a white tile. add a few drops of iodine solution to the leaf
how do we find whether sunlight is necessary for photosynthesis
to find out whether sunlight is necessary for photosynthesis
- destarch a potted plant by placing it in the dark for two days
- remove the leaf and test it for starch
- place a leaf, which is still attached to the plant, between two pieces of black paper. each piece of paper has a certain pattern cut out from it. fasten the pieces of paper using paper clips. place the plant in strong sunlight.
- after a few hours, remove the leaf and test it for starch.
- make a drawing of the leaf to show the regions that are stained blue-black
how do plants absorb sunlight
chlorophyll is a green pigment found in the chloroplasts of plants. it absorbs sunlight, the green colour in the leaves is due to the presence of chlorophyll
how to we find out whether chlorophyll is necessary for photosynthesis
- destarch the plant with variegated leaves, such as a Duranta, placing it in the dark for two days
- expose the plant to strong sunlight for a few hours
- remove one leaf. make a drawing to show the distribution of the green parts, which are the parts that contain chlorophyll
- decolourise the leaf and test it for starch
- make a drawing of the leaf to show the distribution of your black-blue colour. compare this with your drawings in step 3
how do we find out whether carbon dioxide is necessary for photosynthesis
- destarch two plotted plants by placing them in the dark for two days
- enclose the pot in polythene bags. secure the bags to the plant stems
- place one pot in the bell jar. the plant does not have a supply of carbon dioxide from the air because the soda lime and potassium hydroxide solution rapidly absorb carbon dioxide
- set up a control using pebbles and water in place of soda lime and potassium hydroxide solution respectively
- leave both set ups in strong sunlight for a few hours
- remove a leaf from each plant. test the leaves for starch
what are essential for photosynthesis
sunlight, carbon dioxide, chlorophyll
what are some conditions that are also needed for photosynthesis
suitable temperature and water
what are some of the factors that affect the rate of photosynthesis
- light intensity
- the concentration of carbondioxde
- temperature
what happens to the glucose that is formed during photosynthesis
- used immediately to provide energy source for respiration
- energy is used to turn sugars, nitrates and other nutrients into amino acids which build up proteins
- to make cellulose, the main structural material in cell walls
- energy stored as starch in leaves, seeds, roots and tubers
- energy stored as sucrose
- to make fats and oils
- raw materials fro growth, repair and replacement of the damaged parts
why is photosynthesis important
- photosynthesis makes chemical energy available to animals and other organisms
- photosynthesis removes carbon dioxide and removes oxygen
- energy is stored in fossil fuels through photosynthesis
state some facts about chlorophyll
- the green pigment involved in photosynthesis
- traps light and passes high energy electrons into photosynthesis
- gives a green colour to chloroplasts
state some facts about chloroplasts
- the organelle involved in photosynthesis
- organised into chloroplasts which provide space for both light and dark reactions of photosynthesis
- gives a green colour to plants
how to guard cells control the size of the stomata
in sunlight: the guard cells contain chloroplasts, but epidermal cells do not. in daylight, the guard cells manufacture glucose by photosynthesis, they absorb water from nearby epidermis cells. they become turgid and more curved. this is because the cell wall around the stomatal pore is thicker than the other parts of the cell. hence the cell curves around the stoma and the stoma opens
on a hot sunny day: when the leaf loses too much water in strong sunlight, the stomata close. this prevents excessive loss of water by the leaf. in this way, the guard cells can regulate the rate of diffusion of gases into and out of the leaf.
how do carbon dioxide and water enter the leaf
- in daylight when photosynthesis occurs, the carbon dioxide in the leaf is rapidly used up. the carbon dioxide concentration in the leaf becomes lower than that in the atmospheric air, so a diffusion gradient exists. therefore, carbon dioxide diffuses from the surrounding air through the stomata into the air spaces in the leaf
- the surfaces of the mesophyll cells are always covered by a thin film of water. this is so that carbon dioxide can dissolve in it
- the dissolved carbon dioxide then diffuses into the cells
how does xylem transport water and mineral ions to the leaf
- the xylem transports water and dissolved mineral ions to the leaf from the roots.
- once out of the veins, the water and mineral ions move from the cell right through the mesophyll of the leaf
describe the waxy cuticle
PROTECTIVE LAYER ON TOP OF THE LEAF, PREVENTS WATER FROM EVAPORATING
describe the upper epidermis
THIN AND TRANSPARENT TO ALLOW LIGHT TO ENTER PALISADE MESOPHYLL LAYER UNDERNEATH IT
describe the palisade mesophyll
COLUMN SHAPED CELLS TIGHTLY PACKED WITH CHLOROPLASTS TO ABSORB MORE LIGHT, MAXIMISING PHOTOSYNTHESIS
describe the spongy mesophyll
CONTAINS INTERNAL AIR SPACES THAT INCREASES THE SURFACE AREA TO VOLUME RATIO FOR THE DIFFUSION OF GASES (MAINLY CARBON DIOXIDE)
