5.1.5 Photosynthesis Flashcards
What is the equation for photosynthesis?
6Co2 + 6H20 —> C6H12O6 + 6O2
What is autotrophic nutrition
Photosynthesis turns light energy into chemical energy, which organisms, use to make larger organic molecules from simple inorganic molecules such as water and Co2
What do photosynthetic yutes use to respire?
They use the organic molecules from photosynthesis to release energy
What do non photosynthetic (heterotrophs) yutes use to respir?
They digest complex organic molecules and use these products to get energy
Plants respire all the time but only photosynthesise during the day. What is the compensation point and period?
When the rate of respiration and photosynthesis are balanced and the compensation period is the time it takes to reach this compensation point
What does the waxy cuticle do?
Thin layer above the epidermis that Reduces water loss from leaf.
What is epidermis
Has epidermal cells that have no chloroplasts. They prevent water getting out and unwanted substances and organisms getting in like
What is the palisade mesophyll layer
Where most of the photosynthesis occurs. Palisade cells have a lot of chloroplast to help them perform this photosynthesis. They are also packed close together to maximise light absorption
What does the spongy mesophyll do?
Not as closely packed so they can create airspaces inside the lead to enable gases to move in and out. They don’t have as many chloroplast but photosynthesis can still occur here.
What are stomata?
Holes in the leaves that allow gases to diffuse in and out of the leaves. The opening and closing of this is controlled by guard cells. It is also through these stomata that water leaves leaf in process called transpiration
Where does photosynthesis take place?
It’s a two,stage process that takes place all in the chloroplasts
What does the chloroplast contain that is responsible for photosynthesis
Stroma - fluid containing enzymes which catalyse the reactions of the light independent stage
Grana - stacks of thylakoids. In the thylakoid membranes, the photosynthetic pigments are there which are responsible for the light dependent stage
What’s arranged in a funnel shape?
Light harvesting pigments are arranged in a funnel shape called an antennae complex
What are the antennae complexes arranged as
Photosystems I and II
What happens when a pigment receives the appropriate energy level of light?
It boosts the e- to a higher energy level. So in order to drop the e- back into the stable position, it must pass its excess energy on to another pigment molecule. When this happens and e- in the other pigment is excited and the same happens. Eventually the energy gets passed onto the reaction centre
What are the three different types of chlorophyll pigments
Chlorophyll A - p680
Chlorophyll A - p700
Chlorophyll B - p420 - 480
What are accessory pigments
Accompany the primary chlorophylls and they are called carotenoids and xanthophylls. They absorb some of the wavelengths of light that the main ones don’t.
What is the process of photosynthesis (light dependent stage)
- Light hits photosystem II which contains an enzyme that splits water in the presence of light in a process called photolysis: 2H20 - 4H+ + 4e- + O2
- The electrons release from photolysis of water replace the electrons that got excited when light hit photosystem II.
- Electrons that got released from photosystem II get carried down the electron transport chain by electron carriers. These electrons lose their energy along the transport chain to make ATP.
- These electrons then replace the electrons lost when light hits photosystem I and electrons gets excited.
- H+ ions pumped across via chemiosmosis which also makes atp due to atp synthase.
- The electrons along with the H+ ions made from PSII then will arrive at the enzyme NAPD reductase. NADP will receive 2 electrons and the two protons which bind together to reduce NAPD to produce reduced NADP
