Photosynthesis Flashcards
Define photosynthesis.
It is the process by which green plants manufacture their food in the presence of sunlight and co2 from the atmosphere and water provided by the roots from the soil.
What is the significance of photosynthesis?
- It provides food for all
- It provides oxygen for us to breathe in
What are the two most abundant types of chlorophyll?
- Chlorophyll A
- Chlorophyll B
What is Chlorophyll?
Chlorophyll is the green pigment that is found in plants. It is contained in the microscopic organelles known as Chloroplasts.
State the avg no. Of chloroplasts found in a cell. State avg number of chloroplasts found on a leaf too.
40 - 50
500,000 chloroplasts per sq.mm
Why does the chloroplast appear as green?
It appears green because it absorbs light at both ends of the spectrum i.e. red and blue. It reflects back green hence the green color. The absorbed red and blue lights are most effective for photosynthesis.
Some imp terms related to chloroplasts:
- Chloroplasts are oval bodies bounded by double membrane.
- Thylakoids are flattened sacs inside that are piled
- The piles are known as grana/granum
- Chlorophyll is contained in the walls of the thylakoids.
- It is made of H,O, C, N, Mg
- Found in the guard cells, upper epidermis of leaves (palisade and spongy cells) and outer layers of young green stems.
State the balanced chemical reaction of photosynthesis:
6CO2 + 12H2O (chlorophyll^ sunlight)———> C6H12O6 + 6H2O + 6O2 ^
What are the two main phases of Photosynthesis?
- Light-Dependent Phase. (photochemical phase)
- Dark or light-independent phase (Biosynthetic phase)
What are the 2 steps of light phase?
- Activation of chlorophyll by absorbing photons
- Splitting of water and releasing electrons (photolysis) 2h2o—energy of 4 photons—> 4H+ +4e- +O2
What is Photolysis?
Photolysis occurs in the grana of chloroplast and is defined as the splitting of H2O molecules into hydrogen ions and oxygen in the presence of light.
What is the end result of photolysis?
- H ions + Nicotinamide Adenine Dinucleotide phosphate + e- ——> NADPH
- 2O—>O2 (molecular)
- Photo phosphorylation of ADP(adenosine diphosphate) to form ATP
Define Photophosphorylation
It is the process of converting ADP to ATP by adding inorganic phosphate group using the energy provided by the chloroplast.
Define Polymerisation
It is the combination of many glucose molecules together to form one molecule of starch.
State some adaptations in leaf to perform photosynthesis
Large surface area
Leaf arrangement
Cuticle and upper epidermis are transparent
Numerous Stomata
Thin leaves
Chloroplasts are concentrated in upper layers of leaf
Extensive vein system
What are the four uses of glucose?
- Immediately consumed by plant cells
- Stored as insoluble starch
- Converted to sucrose
- Used in synthesizing fats and proteins
What are the external and internal factors that affect photosynthesis?
External factors:
1. Intensity of light
2. Carbon dioxide conc.
3. Temperature
4. Water content
Internal Factors:
1. Chlorophyll
2. Protoplasm
3. Structure of leaf
What effect does iodine have on a leaf?
The leaf turns blue-black in color indicating the presence of starch.
Name some aquatic plants
Hydrilla and Elodea
Name a chemical that absorbs co2
Potassium Hydroxide (KOH)
What is Carbon Cycle?
It is a series of chemical reactions in which the CO2 of the air is used by living organisms and finally returned into air. Its 6 steps are as follows:
1. Photosynthesis
2. Food chain- from herbivores to carnivores
3. Respiration
4. Decaying dead plants and animal remains by decomposers
5. Burning of organic fuel like wood, coal, petroleum,
6. Heating of limestone
