NB CH17 Flashcards
(23 cards)
What is central carbon metabolism and what is part of it?
Includes glycolysis, the TCA cycle, and the pentose phosphate pathway which contain all the chemical precursors required for the synthesis of nearly all other biomolecules
What does the pentose phosphate pathway produce?
Pentose phosphates (ribose-5-phosphate); other key 3, 4, and 7 carbon intermediates; and NADPH
What happens in the pentose phosphate pathway (PPP)?
What can the products of this pathway be used for?
Glucose is oxidized and decarboxylated to form a ribose (ribose-5-phosphate)
Products from this pathway can also be used for anabolic reactions, nucleotide biosynthesis, and glycolysis
Difference between NAD+ and NADP+
NADP+ has a phosphate attached to the ribose sugar, while NAD+ has a hydroxyl attached to the ribose sugar
Is NADP+ –> NADPH an endergonic or exergonic reaction?
It is neither because it is a half reaction. But once coupled with another half reaction it can be exergonic or endergonic overall
What are the three types of ATP phosphorylation?
Substrate-level phosphorylation
Oxidative phosphorylation
Photophosphorylation
What does surface level phosphorylation require?
A phosphate from a substrate
What is the overall ∆G° for photosynthesis?
6CO2 + 6 H2O –> C6H12O6 + 6 O2
+2,879 kJ/mol
Which is highly unfavorable, but driven by light
What is the general equation for photosynthesis?
CO2 + 2 H2A –> CH2O + H2O + 2A
What plant organelle does photosynthesis occur in?
Chloroplasts
Stroma
The fluid in chloroplasts
Thylakoid
The membrane-bound compartment of the chloroplast where photosynthesis occurs
Thylakoid membrane
The part of the thylakoid that contains the proteins necessary for light-dependent reactions
Differences between oxygenic and anoxygenic photosynthesis
Oxygenic uses photosystem I and II, uses water as e- donor, produces O2 during light rxn
Anoxygenic only uses photosystem I, uses H2/H2S/ferrous ions as e- donor, doesn’t produce O2 during light rxn
Cyclic vs. Noncyclic photophosphorylation
- Which photosystem is involved?
- Why is it called cyclic or noncyclic?
- Where do the electrons originate from?
- Where do they end up?
- Is the photolysis of water required?
- Is ATP generated?
- Is NADPH generated?
- Is oxygen a by-product of the reaction?
Cyclic
1. PS I
2. e- comes from chlorophyll and returns to chlorophyll
3. chlorophyll
4. chlorophyll
5. No
6. Yes
7. No
8. No
Noncyclic
1. PS I/II
2. e- comes from chlorophyll and is transferred to NADP+
3. chlorophyll
4. NADP+
5. Yes
6. Yes
7. Yes
8. Yes
Calvin cycle
- What is it also known as?
- Where does it occur?
- What products of light rxns are used in the Calvin cycle?
- Light-independent cycle/dark reactions
- Stroma of chloroplasts
- NADPH and ATP
What is the key enzyme used in the Calvin cycle?
Ribulose-1,5-bisphosphate carboxylase oxygenase (RuBisCo)
What are the inputs and outputs of the Calvin cycle?
Inputs: ATP, NADPH, CO2, H2O, RuBP
Outputs: glucose (after 6 turns of the Calvin cycle)
Smaller steps of the Calvin cycle
- What is produced by one turn of the cycle?
- What are those products used for?
- How many turns does it take to make one extra G3P?
- How many G3Ps does it take to make a glucose molecule?
- 2 G3P molecules
- 5 out of 6 of the carbons from two G3P molecules are recycled to make RuBP, leaving 1 extra carbon
- It takes 3 turns
- It takes 2 G3Ps
GTP is made up of 3 carbons
What three events occur in dark reactions?
CO2 is reduced (eventually forms glucose)
NADPH is oxidized to NADP+
ATP is hydrolyzed
What three events occur in the light reactions of photosynthesis?
Water is oxidized (hydrolyzed)
NADP+ is reduced to NADPH
ATP is synthesized
What are the end products of cyclic and noncyclic photosynthesis?
Cyclic: ATP only
Noncyclic: oxygen, ATP, NADPH
What is the order of photosynthesis?
ETC (light reactions) then dark reactions
