Photosynthesis Flashcards
What is photosynthesis
The process in which light is trapped by chlorophyll and used to convert carbon dioxide and water into glucose and oxygen
What 4 conditions are essential for photosynthesis
Light
Chlorophyll
Carbon dioxide
Water
What are factors which limit photosynthesis rate
Light Intensity - the brighter the light faster photosynthesis
Plentiful Supply of water - plentiful water = increased photosynthesis rate
CO2 concentration - increased CO2 = increased photosynthesis
Colour of light - chlorophyll absorbs red orange blue indigo and violet light most effectively so photosynthesis occurs faster in these colours
The temperature - as temperature rises rate if photosynthesis increased above 35 degrees it decreases as enzymes are denatured
Why do plants need minerals
For healthy growth they are absorbed through the food dissolved in soil water
Nitrate
For making amino acids which are used to make protein without it plant will suffer from stunted growth
Magnesium
For making chlorophyll without this plants leaves will turn yellow
How are leaves adapted for photosynthesis
Large surface area to absorb light rays
A thin shape si gases can diffuse In and out easily
Chloroplasts which contain chlorophyll to absorb light energy
Veins to support the leaf and carry substances to and from all of the leafs cells
Testing a leaf for starch
Drop leaf in boiling water to remove waxy cuticle and soften the leaf
Out the leaf into ethanol in a boiling tube and heat this to extract green chlorophyll so you can see the results
Wash the white leaf in hot water then add a few drops of iodine solution
If photosynthesis has occurred leaf will turn black because starch is present
What color does iodine turn in presence of starch
From brown to blue black
Where is starch made in plants
Only where it’s green - places that contain chlorophyll
What does placing a plant with soda lime in a bell jar do
Deprives it of carbon dioxide so it’s unable to make starch
How does the plant make starch
Produces glucose from photosynthesis , its then joined in chains to make starch molecules ( a polysaccharide )
What does chlorophyll do
Absorbs the light energy needed for ohtosyntheis
How does the cuticle help te leaf
Reduces water loss by evaporation and acts as a barrier to enterance of disease microorganisms
Upper and lower epidermis have few chloroplasts and are covered by the cuticle
How do stomata help leaf
In lower epidermis m
Allows carbon dioxide to diffuse into leaf to reach the photosynthetic tissues . Allow oxygen and water vapour to diffuse in . Each stomata is formed as a gap between two guard cells . In sunlight they become Turgud this opens the stomata which increases gas exchange . Low light causes them to become flaccid this closes the stomata and decreases water loss
What is the mesophyll
Two layers of photosynthetic cells in the middle of the leaf mist photosynthesis takes place here
Made up of the Palisade layer- densely packed for lost of photosynthesis contain many chloroplasts and close to light source as the upper epidermis is transparent
Below the pallaside layer is the spongy layer
Loosely packed cells with air spaces between them they photosynthesise but have less chloroplasts than the palisade layer .gas exchange occurs here and air spaces allow oxygen and water vapour to exit the mesophyll and carbon dioxide to come in
Why Is starch more useful than glucose
Storage substance insoluble so can be stored in leads and roots also takes up less space than glucose
What’s the vein
Contains xylem to bring water and salts and phloem to transport sucrose to other respiring parts of the plants that cannot photosynthesis
How is leaf adapted for gas exchange
Stomata allow CO2 in and oxygen out
Air spaces in the spongy layer allow circulation of air
Guard cells determined when photosynthesis can occur and
How do plants use glucose
Some is used for respiration
Some is turned into starch for storage by polymerisation
Some is turned into sucrose for transport
Some is turned into cellulose for plant walls
By polymerisation
Sugar can be converted into lipids which are stored in seeds
Sugars can be combined with nitrates to make proteins and DNa
Sugars can be combined with magnesium to make chlorophyll
Phosphate
Making DNA deficiency leads to poor root growth younger leaves go purple
Potassium
Needed for enzymes of respiration and photosynthesis to work
Deficiency is yellow leaves with dead spots
