11: Photosynthesis Flashcards
Where is the site of photosynthesis?
Chloroplasts within the leaf
What are the structures in the chloroplast?
Grana - stacks of thylakoid membranes
Stroma - fluid-filled matrix
Thylakoid membranes - contain photosynthetic pigments
Intergranal lamella - tubular extensions that connect grana
Chloroplast envelope - double plasma membrnae
What are the rough dimensions of a chloroplast?
2-10μm long
1μm diameter
How is the structure of the leaf adapted to photosynthesis?
Large SA:V to absorb most sunlight
Leaves arrange so minimal overlapping and shadows
Thin - short diffusion pathway & more light absorbed
Transparent cuticle/epidermis - most light onto chlorophyll underneath
Many stomata - short diffusion pathway to outside
Air spaces - rapid diffusion to cells in gas phase
Mesophyll cells - densely packed and contain many chloroplasts
What is the overall equation of photosynthesis?
6CO2 + 6H2O -> C6H12O6 + 6O2
What are the three main stages of the photosynthesis?
Capturing of light energy
Light-dependent reaction (LDR)
Light-independent reaction(LIR)
What does the stroma contain?
Enzymes
Starch grains
DNA
70S ribosomes
Why is DNA and ribosomes in the chloroplast more efficient?
Proteins needed in photosynthesis are made in the organelle so they don’t have to be retrieved from the cytoplasm
Define oxidation
Loss of electrons could gain oxygen
Define reduction
Gains electrons could lose oxygen
What is a photosynthetic pigment?
Different chemicals which absorb different λ of light
What are the dominant photosynthetic pigments?
Chlorophyll a (dominant pigment)- absorbs best in red & blue, least in green
What is a photosystem?
Clusters of different photosynthetic pigments
Allows for absorption of as many different λ of light possible
What is photosystem (PS) I and II?
Photosystem I - inter-granal lamellae (p700)
Photosystem II -thylakoid membranes (p680)
What are primary and accessory pigments?
Primary - chlorophyll a absorbs most of the light
Accessory - carotene etc. which absorbs other λ of light
What are the three main stages of the light-dependent reaction?
Photophosphorylation
Photolysis
Reduction of NADP to reduced NADP
What occurs in photophosphorylation?
Light absorbed by chlorophyll a (PSII)
Electrons promoted to higher energy level then removed
Electrons passed along electron carriers to PSI
Energy released as transferred allowing for the reaction: ADP + Pi -> ATP
What is the precise mechanism by which ATP is produced?
Chemiosmotic theory