mitochondria and chloroplasts 2 Flashcards
Function of chloroplasts
Harvest energy from sunlight, convert it to chemical energy to fix carbon from the atmosphere (CO2) into sugars
Features of phosphorylation
Electrons passed along ETC are from water, but unlike NADH, H2O is a poor donor of electrons, so requires energy input from light to extract electrons
How does light raise energy of electrons
Sunlight absorbed by chorophyll and electrons interact with photons, raising them to higher energy level
What does chlorophyll look like
Haem, except metal ion at the centre is Mg not Fe
in depth explanation of electron transfer from panopto
When chlorophylls in antenna complex absorb light they channel it into electrons in special pair of chlorophylls- get excited to higher energy level, can be donated to electron acceptor
If electrons are low energy can’t be passed onto electron acceptor (See diagram)
Mobile electrons carriers: Plastoquinone
resembles ubiquinone of mitochondria
Plastocyanin
small copper containing protein
Ferredoxin
Small protein containing a Fe-S centre
How is ATP generated
BY proton gradient across thylakoid membrane, same as in mitochondria
What are high energy electrons passed onto form at the end of the ETC
high energy NADPH, strong reducing agent
What are high energy electrons passed onto form at the end of the ETC
high energy NADPH, strong reducing agent
What are the NADPH and ATP generated by light dependent PS used for?
Energy sources to fix carbon from CO2 into sugars (by calvin cycle)
RUBISCO
Ribulose biphosphate carboxylase
Function RUBISCO
Catalyses initial reaction in carbon fixation
Very slow enzyme, so a lot is required to fix a lot of carbon
Catalyses addition of one carbon (CO2) onto a 5C (ribulose biphosphate) molecule to make a 6C intermediate, then cleaved to produce 2 3C molecules
Calvin cycle overview (add to from panopto)
For every three carbons that are fixed a 3C molecule can be removed from the cycle
glyceraldehyde 3-phosphate
For every 3 carbon sugar produced what is required
9 ATP and 6 NADPH
Thylakoid contents
PS I and II, ATP synthases and NADP reductase
Stroma processes
ATP synthesised, NADPH synthesised, carbon fixation, DNA
Similarities between processes in mitochondria and chloroplasts
Both use proton gradients across membranes to make ATP using ATP synthase
Electron transport along an ETC drives proton pump
Some components of ETC same- cytochrome bc and b6f similar and ubiquinone and plastoquinone resemble one another
Photosystems
Antenna complex and reaction centre
What do electrons extracted from water replace
electrons lost from PSII
Other products of splitting of water
O2
H+- contributes to proton gradient across thylakoid membrane
order in thylakoid membrane
PS II, cytochrome b6-f, (similar to bc-1) PS I, NADP reductase
What is energy lost from electrons used for
pumping protons
