Biology unit 6 Flashcards
Unit 6
Definition of photosynthesis
the process by which plants manufacture carbohydrates from raw materials using energy from light
Word and symbol equation of photosynthesis
Carbon dioxide + water ➡️ glucose + oxygen
Chlorophyll
Chlorophyll is the protein found within chlorophlasts that catalyses the reaction. It is also what causes plants to be green.
1 uses of glucose in plants
Glucose is commonly stored in plants as starch (long chains of glucose)
2 uses of glucose in plants
Glucose can be used in cellulose to build cell walls
3 uses of glucose in plants
Glucose can be used for respiration
4 uses of glucose in plants
Glucose can be converted and transported through phloem vessels from SOURCE to SINK
5 uses of glucose in plants
Glucose can be converted to nectar and used to attract pollinators
Leaf adaptations
Large surface area
Very thin- air diffusion
Parts of the leaf - guard cells
Guard cells - open and close stomata
Parts of the leaf - waxy cuticle
Waxy cuticle - allows light to pass whilst protecting leaf surface
Parts of the leaf - epidermal cells
Offers protection but thin to allow light through
Palisade cells
Contain many chloroplast
Packed tightly together
Large surface area
Large vacuole pushes chloroplast to edges of cell
Thin cell walls to aid gaseous exchange
Sponges mesophyll
Irregular shaped
Fewer chloroplasts
Smaller than palisade cells
Spaced out with air pockets in between
Vascular bundle
Xylem - carries water up the plant
Phloem - carries nutrients all around the plant
Definition of limiting factor
A limiting factor is something that is in short supply that restricts a process
Limiting factors of photosynthesis
When a process depends on two or more factors (variables), the rate of that process is determined by the factor which is in shortest supply ( aka bottleneck)
Limiting factors of photosynthesis
Light intensity
Carbon dioxide concentration
Temperature
Effect of light intensity
The rate of photosynthesis increase with light intensity
When the intensity of light increases to a certain point, photosynthesis cannot go any faster
The actual max varies depending on the plant 🌱 type
Effect of carbon dioxide concentration
Increasing the carbon dioxide concentration, increases rate of photosynthesis
But, there is a max rate, where adding more co2 will have no effect anymore
Effect of temperature
Too much heat damage enzymes and causes them to denature
Too much heat also evaporates water out of leaves and forces stomata to close
Too little heat can reduce enzymes reaction rate by reducing number of collisions between the enzyme’s active site and substrate
Magnesium deficient plants
Magnesium is required for chlorophyll
Yellowing between the veins of leaves (aka chlorosis) due to lack of chlorophyll production
Nitrate deficient plants
Stunted growth
Leaves (usually near growing tip) start to turn yellow
Ratio of photosynthesis to respiration
The ratio of photosynthesis to respiration in plants changes over the day cycle
Plants are constantly respirating and releasing carbon dioxide
Plants only photosynthesise during the day when sunlight is available taking in carbon.
Net carbon dioxide day vs night
During the day plants photosynthesise faster than they respire, resulting in a net intake of carbon dioxide
During night plants respire more than they photosynthesis, resulting in a net release of carbon dioxide
Hydrogen carbonate indicator
Hydrogen carbonate
indicator is a pH indicator
that changes colour
depending on the pH of a
solution
Carbon dioxide is acidic.
Higher carbon dioxide
concentration = more
acidic
