Photosynthesis Flashcards
What are the adaptations of a leaf for photosynthesis?
- Large surface area of leaves for absorbing light
- Thin leaves so short diffusion distance + can absorb light
- Transparent cuticle so can absorb light
- Many stomata for gas exchange of carbon dioxide and oxygen
Where is light dependant reaction?
Thylakoid membrane
What is photoionisation
Where chlorophyll absorbs light and electrons are excited to a higher energy level and electrons lost as move down electron transport chain
What is photolysis of water?
Where water is split producing: oxygen, protons and electrons
What is chemiosmosis?
Where protons are actively transported into the thylakoid space via proton pumps in the stroma and they move down electrochemical gradient via ATP Synthase to produce ATP
Describe light dependant reaction:
- Electrons are excited and raised to a higher energy level
- Electrons move down electron transfer chain through series of redox reactions via electron carriers releasing energy
- Energy used to actively transport protons into thylakoid space via proton pumps in the stroma
- Build up of protons in thylakoid space creates concentration gradient and protons move down electrochemical gradient via ATP Synthase to produce ATP
- Photolysis of water results in the splitting of water into oxygen, electrons and protons
- NADP is reduced by protons and electrons to produce NADPH
What are the products of light dependant reaction?
NADPH, oxygen and ATP
Where is the light independent reaction?
Stroma
Describe light independent reaction
- Carbon dioxide reacts with RuBP, catalysed by Rubisco
- Forming 2 x Glycerate-3-Phosphate
- ATP (hydrolysed) and NADPH (oxidised) used to reduce Glycerate-3-Phosphate into Triose Phosphate
- Triose Phosphate regenerates into RuBP
- Triose Phosphate converts into organic molecule eg: sucrose/ amino acid
Why do weed killers cause plants to
give off heat? (2)
- Energy released from excited electrons, which is meant to be used to pump protons across membrane
- Can’t happen as weed killers block electron transfer chain so energy released as heat
What is chromatography?
- Method of separating soluble molecules
Describe chromatography method:
- Crush leaves to obtain pigment
- Draw a pencil line 2 cm away from end on chromatography paper
- Use pigment to create spot on pencil line
- Put paper into beaker containing solvent so that solvent is below pencil line
- Allow pigment to be carried by solvent and remove before reaches top
- Allow to dry
- Measure distance travelled by solvent and distance travelled by pigment to work out Rf
If substance moves up chromatography paper more what does that mean?
- Substance is more soluble
What is the formula for Rf value?
(Distance travelled by pigment) / (Distance travelled by solvent)
Why do we use pencil for origin rather than ink?
- Ink would mix with pigment and contaminate results
