Bioenergetics Lecture 5 summary 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 F o in inner membrane F 1 in matrix Lower 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 water used 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 PHOTOSYNTHESIS

Respiration vs photosynthesis Mitochondria –All aerobic eukaryotes Oxidation of CHO to CO 2 Generation of NADH and FADH 2  ATP synthesis Chloroplasts –Plants, algae Energy harvest from sunlight Generation of NADPH  Reduction of CO 2 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 O 2

Red and Blue light are absorbed from the incident (white) light, leaving Green to be reflected or transmitted

Photosynthesis produces oxygen Are all wavelengths photosynthetically active? Spirogyra Photosynthetic Active 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 reaction phaeophytin 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