Topic 5 Flashcards
(28 cards)
What are inside chloroplasts?
Stroma
Granum
Thylakoid
DNA
Lamella
Outer membrane
Inner membrane
What are thylakoids?
Folded membranes containing the photosynthetic pigments (chlorophyll) and electron carrier proteins.
What is a Granum?
A stack of thylakoids
Why are thylakoids folded membranes?
To give a large surface area to increase the number of LDRs that can happen
A large number of pigment molecules
What are the Lamella in chloroplasts?
Membrane channels that connect and distance the grana
What is the stroma?
The fluid centre of a chloroplast that contains enzymes involved in the light independent reaction and contains the loop of DNA and 70 S ribosomes.
What are photosystems?
Collections of pigment that absorb light.
What are the two stages of photosynthesis?
Light dependent reaction
Light independent reaction
What is oxidation?
The loss of electrons or protons/gained oxygen
What is a reduction?
Gain of electrons or protons/lost oxygen
What are the key steps in the light dependent reaction?
Photoionisation
Photophosphorylation
Photolysis
NADPH production
What is photoionisation?
Chlorophyll molecules in PS11 absorb light and electrons become excited to high energy level.
They leave the chlorophyll on accepted by electron carriers.
The chlorophyll becomes a positively charged ion and unstable.
What is photophosphorylation?
The electrons are transferred along the electron carriers which form an electron transport chain located in the thylakoid membrane.
The electrons lose energy as they pass from one carrier to the next as each carrier is at a lower energy level involved on the previous. Eventually, they are passed to PS1.
The energy released is used to pump hydrogen ions into the thyroid across the membrane. This forms an electrochemical gradient.
The hydrogen ions can only diffuse back down the gradient through ATP synthesis embedded in the membrane.
The energy release when this happens is used to form ATP from ADP and PI.
What is photolysis?
This is when water is split using light energy into hydrogen ions, electrons, and oxygen in PS11.
What are the products of photolysis used for?
The electrons replaced those lost in PS11
Oxygen is released as a waste product
Why can photolysis only happen in PS 11?
Because it has the correct enzyme complex
What happens in PS1?
The electrons are still excited and passed through electron carriers however no ATP is synthesised.
Be excited electrons are accepted by the electronic accepted NADP.
Every time the NADP accepts an electron also takes a hydrogen ion from photolysis.
The NADP becomes an NADPH
What are the products of the light dependent reaction?
NADPH and ATP
What is the first step of the light independent reaction?
Carbon dioxide entering the leaf via the stomata and diffusing down a concentration gradient into the stroma of the chloroplast.
What is the second step of the light independent reaction?
Carboxylation
What is carboxylation?
When CO2 combines with RuBP (5C) to create a 6C compound that immediately split into two molecules of GP. This reaction is catalysed by Rubisco.
What happens after carboxylation in the LIR?
GP is reduced into a 3C compound called triose phosphate. Energy from the LDR provides energy for this and NADPH from the LDR provides electrons to reduce it.
What happens after triple phosphate is formed in the LIR?
Using ATP, 5/6 molecules of TP are used to regenerate RuBP and 1/6 is converted into glucose and other organic molecules such as polysaccharides, amino acids and glycerol
