Respiration and Photosynthesis Flashcards
(21 cards)
Why is ATP useful as energy carring molecule?
Energy released in small amounts
Release in single step reaction
Soluble in water
Quiclky broken and resynthesisable
Example of ATP requiring process?
Active transport
Synthesis reaction
Muscle contraction
Cell division
Light independent reaction
Glycolysis
Equation for aerobic respiration?
C6H12O6 + 6O2 → 6CO2 + 6H2O + -38 ATP
Equation for ethanol?
C2H5OH
Steps of respiration and their location?
Glycolysis, cytoplasm
Link reaction, matrix
Kerb’s cycle, matrix
Oxidative phosphorylation, cristae
Describe glycolysis?
In cytoplasm
2ATP phosphorylate a glucose making it more reactive
Forms fructose 1,6 - bisphosphate
Then became 2 triose phosphate
TP is oxidised by NAD (forming NADH also) forming pyruvate
This release energy, that can be used to form 4 ATP through substrate level phosphorylation
Describe link reaction?
Pyruvate diffuse into matrix
Then pyruvate gets oxidised by NAD and gest CO2 removed, becoming acetate
This also form NADH
Acetate and coenzyme A gets combined and form Acetyl CoA
Describe kerb’s cycle?
Acetyl CoA combines with a 4C molecule and Coenzyme A is removed to form 6C molecule entering cycle
Then 6C molecule become again 4C molecule as it gets oxidised by NAD and FAD
Reduced coezyme A pass H throgh ETC producing ATP
Therefore it produces 3NADH, 1FADH and 1ATP per cycle
Describe oxidative phosphorylation?
NADH and FADH are oxidised, releasing H atom
H atom ia split into H+ and e-
e- pass down carriers at decreasing energy level, releasing energy, that pump protons into inter membrane space
Due to gradient of proton, it diffuse across ATP synthase into matrix
ATP synthase gets energy form protons, forming ATP from ADP and Pi
At end of chain e- and proton combine with oxygen forming water
Total of 34 ATP forms through 1 oxidative phosphorylation
Anaerobic respiration in animals?
Pyruvate + NADH + H+ -> Lactate + NAD
Anaerobic respiration in fungi e.g. yeast?
Pyruvate + NADH + H+ -> Ethanol + Carbon dioxide + NAD
Respiration quotient?
Volume of CO2 produced/volume of O2 absorbed (from direct observation)
light-dependent reaction produces?
ATP
Reduced NADP
Oxygen
light-independent reaction?
CO2 combine with RuBP using rubisco and turn in GP
NADP and ATP energy is used to reduce GP to form triose phosphate
Describe non-cyclic light dependent reaction
occurs in the grana of chloroplasts
Light energy is absorbed by the chlorophyll in PSII
This excites electrons to a higher energy level, the chlorophyll becomes positively
charged
The electrons are passed from one carrier to another in the ETC in thylakoid membranes
During each transfer, energy is released
This energy is used to actively pump protons from the stroma into the thylakoid interior space
A proton gradient is established and protons then diffuse into the stroma via the enzyme ATP synthase
The energy transferred by the movement of protons is used to phosphorylate ADP
to form ATP
The electrons are transferred to the PSI
Light energy absorbed in PSI excites electrons to a higher energy level
The electrons are accepted by NADP and is reduced
NADP also accepts protons (H+) from the splitting (photolysis) of water
Water is split (photolysis) releasing electrons, protons (H+) and oxygen.
Electrons from the water replace the electrons lost from the chlorophyll in PSII
Cyclic phosphorylation
Light energy is absorbed, excites
electrons to a higher energy level
The electrons are taken up by a high energy electron acceptor, which is
reduced
The electrons release energy as they are passed down a series of electron
carriers (including the cytochromes) at decreasing energy levels
This energy is used to actively transport protons from the stroma into the
thylakoid
protons then diffuse into the stroma via the enzyme ATP synthase
The energy transferred by the movement of protons is used to phosphorylate
ADP to form ATP
The electrons eventually return to chlorophyll in photosystem I
Describe light Independent Reaction?
CO2 are fixed by combining with the carbon dioxide acceptor RuBP (5C)
This reaction is catalysed by Rubisco
This forms two molecules of glycerate-3-phosphate (GP)
The GP then is reduced using reduced NADP to produce triose phosphate
ATP supplies the energy required for this reaction
How is TP used?
Form all photosynthetic products e.g. glucose, fatty acids, glycerol, amino acids
Regenerate the CO2 acceptor molecule RuBP (5C) in the Calvin cycle
C3 plants?
The first metabolic pathway deduced concerning the synthesis of sugars in photosynthesis was the Calvin cycle
It was initially discovered in algae and later
found in other plant species.
The light independent reaction involves the fixation of CO2 by Ribulose bisphosphate (RuBP)
to produce a 3 carbon compound Glycerate - 3 – phosphate (G3P)
Photorespiration?
RuBP fixes O2 and results in the production of glycolate which is broken down to release CO2 but no ATP
Photorespiration generally occurs in the light when photosynthesis reduces the CO2 concentration in the air spaces of the leaf and increases the O2 concentration
C4 plants?
C4 photosynthesis enhances the ability of certain plants to fix CO2 under harsh condition
This is called the C4 pathway because a 4 carbon compound is formed following the fixation
The CO2 acceptor is a 3C compound called PEP
All C4 plants are characterised by having a unique cell anatomy
The CO2 is first fixed in the mesophyll cells and then shuttled to the bundle-sheath cells for conventional C3 fixation
The carbon is shuttled in the form of a 4C acid which releases CO2
This is fixed by RuBP and the resulting 3C compound produced is shuttled back to the mesophyll cells for
conversion into the CO2 acceptor
Metabolically the advantage to the plant is that this reaction is much more efficient
It is not inhibited by oxygen.
The enzyme PEP carboxylase has a higher affinity for CO2 so can continue to fix CO2
even at low concentrations e.g. when it is hot and dry and stomata are partially closed
