Upload
agustin-addison
View
233
Download
2
Tags:
Embed Size (px)
Citation preview
Bioenergetics Lecture 5 summary• [email protected]• Last time –integrating catabolic
metabolism, review catabolism• This time
– similarities and differences between cellular respiration and photosynthesis
– chlorophyll, photosystems II and I (in that order)
• But first….!
Electron transport chain pumps H+, making a gradient
Fo in inner
mem
brane
F1 in
matrixLower H+ concentration = higher pH
Mitochondrial matrix
Higher H+ concentration = lower pH
Intermembrane space
ATP synthase uses the H+ gradient to generate ATP
Potential energy of falling waterused to grind grain
Potential energy of ‘falling’ H+ used to generate ATP
ATP synthase uses the H+ gradient to generate ATP
Cellular Respiration
A series of redox reactions ….
PHOTOSYNTHESIS
RESPIRATION
RESPIRATION
PHOTOSYNTHESIS
Respiration vs photosynthesis
• Mitochondria– All aerobic eukaryotes
• Oxidation of CHO to CO2
• Generation of NADH and FADH2
ATP synthesis
• Chloroplasts– Plants, algae
• Energy harvest from sunlight• Generation of NADPH
Reduction of CO2 to CHO
Note NADH (respiration) vs NADPH (photosynthesis)P photosynthesis
CHO = carbohydrate
Photosynthesis is an endothermic redox process
Energy source?
Useful byproducts? Sunlight
Glucose and O2
Red and Bluelight are absorbed from the incident (white) light, leaving Green to be reflected or transmitted
Photosynthesis produces oxygen
Are all wavelengths photosynthetically active?
Spirogyra
PhotosyntheticActive spectrum
First, light energy must be captured
Illuminated chlorophyll fluoresces (gives off light) if captured light energy is not transferred to another acceptor
Capture is not enough!
Isolated chlorophyll fluoresces if newly captured energy is not transferred
In a leaf, the reaction centre transfers the captured energy to a relatively stable intermediate chemical
The reaction centre is the heart of the photosystem
Energy transfer between pigment molecules to a special central pair of chlorophylls (reaction centre) and thence to the primary electron acceptors
Two parts to the light reaction
Chemiosmosis can make ATP
Two parts to the light reactionphaeophytin
ferredoxin
Source and fate of carbon and oxygen in carbohydrates formed by photosynthesis
Photosystem II makes ATP
Photosystem I makes NADPH
NADH vs NADPH
• NADH catabolism
• NADPH anabolism
(P photosynthesis)
• For each, the reduced form stores ~ 3 times more energy than ATP