Unit 8 Flashcards
How is the chloroplast adapted for its function of photosynthesis? (4 Marks)
- Thylakoids have small internal volumes, allowing for a high H+ concentration to be maintained
- There are many grana in the chloroplast, maximising its surface area.
- Grana contain many photosynthetic pigments to carry electrons
- Chlorophyll (photosynthetic pigments) allows for maximum amount of light to be absorbed
- Stroma has optimal pH conditions for enzymatic activity in Calvin Cycle
What are metabolic reactions that intake energy and excrete energy?
Endergonic, exergonic.
What are non-competitive inhibitors?
they bind to allosteric sites, causing conformational shape change of enzyme’s active site, meaning substrates can’t bind; not a similar shape any more. they do not get affected by substrate concentration.
What is water used for in photosynthesis?
Photolysed by light, creates an electron, replaces electron lost in chlorophyll A in photosystem II, moves down ETC. Also provides H+ ions in thylakoid space to create a high concentration gradient (proton motive force).
What are the consequences of phosphorlyation?
It creates a less stable molecule.
Outline the stages of glycolysis
Glucose is phosphorylated twice by two ATP molecules. this then creates a less stable molecule splitting it into two triose phosphates. these molecules are then oxidised by electron carries NAD+ which are reduced into NADH + H+ and are used in the electron transport chain. The triose phosphates then produce 2 ATP molecules each then become pyruvate which is transported from the cytosol to the mitochondria.
What occurs in the link reaction?
in the mitochondrial matrix pyruvate attaches to coenzyme-A, which then causes an oxidative decarboxylation, creating CO2, removing one of three carbons, then the molecule is oxidised which reduces NAD+ into NADH + H+, this overall creates acetyl-CoA which is used in the Krebs cycle.
Explain the Krebs cycle
The Krebs cycle is a metabolic cycle which is dependent on acetyl-CoA and oxaloacetate to commence. As these 4C and 2C molecules join they produce citrate, this is then oxidatively decarboxylated into a 5C molecule, this reduces NAD+ into NADH + H+ as it is oxidised. this is then oxidatively decarboxylated into a 4C molecule, this reduces NAD+ into NADH + H+ as it is oxidised. Then the 4C molecule is modified into oxaloacetate, creating energy to bind an ADP + Pi into ATP, also oxidising itself allowing NAD+ to be reduced into NADH + H+ and FAD into FADH2.
Explain electron transport chain in cell respiration.
NADH + H+ is oxidised release 2e- and 2H+, 2e- moves into the electron carrier membrane proteins allowing proton pump of H+ ions to maintain high concentration gradient allowing chemiosmosis. electrons move down ETC until ATP synthase. Second carrier oxidises FADH2 creating 2e- and 2H+, same occurrence. H+ ions move down ATP synthase due to high proton motive force and chemiosmosis which creates torsional energy allowing ADP to form a bond with a Pi creating ATP. Oxygen in the matrix then associates with the electrons creating a negatively charged ion which then associates with 2 positively charged hydrogen ions creating water. This occurs in the mitochondria and between the mitochondrial inner membrane (intermembrane space and matrix).
Explain end-product inhibition with an example.
Threonine into Isoleucine. Threonine dehydrogenase is non-competitively inhibited by isoleucine, as isoleucine binds to an allosteric site of the enzyme making the active site undergo a conformational shape change meaning threonine cannot bind and therefore undergo the reaction necessary to produce isoleucine, decreasing the concentration intermediates in the metabolic chain.
Explain light dependent photosynthesis.
Light charges chlorophyll A in PS2 to release an electron, which allows for H+ to be proton pumped into the thylakoid space maintaining a high proton motive force, this electron moves down the thylakoid membrane into PS1 where it then is used to reduce NADP+ into NADPH in NADP+ reductase enzyme protein in memrbrane. ATP synthase then utilises the H+ ions chemiosmosis due to high proton motive force allowing ADP to create a bond with Pi to form ATP used in light independent reaction (along with NADPH) this is called photophosphoryhlation. Photolysis of water to replenish chlorophyll A’s electron and create H+ ion concentration in thylakoid space. This occurs in the chloroplasts in the thylakoid space and stroma.
Compare and contrast cyclic and non-cylic photophosphorylation
Cylic: doesn’t need to replenish electron as it stays in photosystem 1 and is charged by light whilst not being used to reduce NADP+, so it only needs to maintain a high proton motive force so it pumps H+ ions into thylakoid space and undergoes chemiosmosis down ATP synthase. only creates energy when it is needed in excess (NADPH is needed for light independent), doesn’t create oxygen, doesn’t create NADPH.
Non-cyclic: utilises both photosystems, requires photolysis of water, creates energy for light dependent reaction, creates oxygen as a byproduct, creates NADPH.
State the necessary products needed for the Calvin cycle
Ribulose Bisphosphate, Rubisco, carbon dioxide, NADPH and ATP.
