Photosynthesis Flashcards
How are leaves adapted for photosynthesis?
- Large surface area for maximum sunlight absorption
- Minimised overlapping of leaves
- Thin to reduce diffusion distance
- Transparent cuticle and epidermis that let light light through to the photosynthetic mesophyll.
- Long, narrow upper mesophyll packed with chloroplasts
- numerous stomata for gaseous exchange
- Many air spaces in the lower mesophyll to allow diffusion of CO2 and O2
- A network of xylem that brings water to the leaf cells, and phloem that carries away sugars produced in photosynthesis.
Equation of photosynthesis
6CO2 + 6H2O > C6H12O6 + 6O2
3 Main stages to photosynthesis
- Capturing of light energy
- The light- dependent reaction
- The light- independent reaction
The light- dependent reaction
Light energy is converted into chemical energy. During the process an electron flow is created by the effect of light on chlorophyll and this causes photolysis (water split into protons, electrons and oxygen). The products of this reaction are NADP, ATP and oxygen.
ATP is then used to form more ATP by adding Pi to ADP.
The light- independent reaction
Protons (hydrogen ions) are used to reduce CO2 to produce sugars and other organic molecules.
Structure and role of chloroplasts in photosynthesis
- Typically disc shaped
- Surrounded by a double membrane
- Contain GRANA which are stacks of up to 100 disc- like structures called THYLAKOIDS where the light- dependent stage takes place.
- Within the thylakoids is the pigment called chlorophyll.
- Some thylakoids have tubular extensions called inter-granal lamellae.
- The STROMA is a fluid-filled matrix where the light-independent stage of photosynthesis takes place. Within the storm are a number of other structures, such as starch grains.
Oxidation
When a substance combines with oxygen- loses electrons.
Reduction
When a substance loses oxygen- gains electrons.
