Biol 121, Fall 2010, Tom Buckley 06 Oct 2010

capture: photosynthesis

use: respiration

Bioenergetics: energy and carbon flow

Q: Which direction will water move?

(a) from left to right

(b) from right to left

s = -3.6s = -0.5

p = +2.6p = +0.5

Cell #1(LEFT)

Cell #2(RIGHT)

we have: light, CO2 , H2O

Photosynthesis

we want: carbohydrate

Chloroplast

Thylakoid

leafmesophyllcells

}

Photosynthesis: steps 1. water splitting

chlorophyll

photon is absorbed electron is ejected

++ charge makes chlorophyll

a strong oxidant

Photosynthesis: steps 1. water splitting

chlorophyll

++ charge makes chlorophyll

a strong oxidant

reductant: donates electrons

oxidant: takes electrons away

Photosynthesis: steps

H-O-H

1. water splitting

chlorophyll

+ charge makes chlorophyll

a strong oxidant

electron is strippedfrom water

H+ O2

+

Photosynthesis: steps 2. electron transport

electron is ejected electron transport chain

NADP HNADP+

Photosynthesis: steps 2. electron transport

electron transport chain

electron transport chain

Photosynthesis: steps 2. electron transport

Concentration gradients are a form of energy

H+

ADP ATP

Photosynthesis: steps 2. electron transport

elec

tron

is e

ject

edADP

ATP

electron transport chain

NADP+

NADPH

Q: Where do the electrons that reduce NADP+

originally come from?

(a) water

(b) CO2

(c) oxygen

(d) sunlight

ADPATP

NADP+

NADPH

Q: Is water reduced or oxidised in photosynthesis?

(a) reduced

(b) oxidisedADP

ATP

NADP+

NADPH

StomaCO2

photosynthesis

Photosynthesis: steps

CO2

Calvincycle

3. Calvin cycle

NADPH

ATP

NADP+

ADPsugar

Photosynthesis: steps

3x CO2

3x RuBP(5C) 6x PGA

(3C)

3. Calvin cycle

6 NADPH

6 ATP

6x PGal(3C)

6 NADP+

6 ADP

sucrose& starch

3 ATP

3 ADP

1/65/6

Photosynthesis: steps side note: fluorescence

NADPHNADP+

X

photon

Calvincycle

Photosynthesis: steps carbon fixation

CO2

RuBP 2x PGA

enzyme:

Rubisco

most abundant protein on Earth

~half of N in leaves

big, slow

Calvincycle

CO2

RuBP 2x PGA

Photosynthesis: steps photorespiration: O2 fixation

enzyme:

Rubisco

most abundant protein on earth

~half of N in leaves

big, slow

also fixes oxygen

O2

RuBP PGlyc + PGA

carbonlost

energyconsumed

Photosynthesis: overview

1. water splitting: provide energetic electrons

2. electron transport: generate ATP & reductant (NADPH)

3. carbon fixation: attach (fix) CO2 to organic molecule

4. carbon reduction: use NADPH to reduce the fixed carbon

Photosynthesis: overview

Light reactions

Calvin cycle

1. water splitting: provide energetic electrons

2. electron transport: generate reductant (NADPH) & ATP

3. carbon fixation: attach CO2 (from air) to organic molecule

4. carbon reduction: use NADPH to reduce the fixed carbon

Photosynthesis: importance

All the energy that fuels nearly all life

All the carbon that nearly all life is built from

Group exercise

H2O

O2

H+

e-

NADPHNADP+

e-

ADP ATPH+H+H+

e-

pH is a measure of H+ concentration.

Low pH means high H+ concentration.

If we isolated thylakoids and put them inlow and high pH solutions, in which solutionwould thylakoids produce more ATP?

photon

Jagendorf experiment

H+

H+H+

H+

H+H+

H+

H+H+

low pH

H+H+H+H+ H+

H+

H+

H+

H+ H+

H+

H+H+

H+

H+H+

H+

H+H+

low pH

H+

high pH+ ADP, Pi

H+H+H+H+ H+

H+

H+

H+

H+ H+

H+

ADPADP

ADP

ADP

Pi

Pi

Pi

Pi

H+

H+

H+H+ H+

H+

H+

H+ H+

H+

H+ATP

ATP

ATP

ATPATP formed!

Q: What is the enzyme responsible forCO2 fixation called?

(a) Nabisco

(b) Rubisco

(c) ConAgra

(d) Viagra

(e) Beatrice

CO2

RuBP 2x PGA

ATPADP

Respiration

electron transport chain

in mitochondria

NAD+

CO2

sugars

NADH

H2O O2

Krebscycle

ADP

Photosynthesis

electron transport chain

elec

tron

is e

ject

edATP

NADP+

NADPH CO2

sugars

in chloroplasts

H2O O2

Calvincycle

Aerobic respirationPhotosynthesis

CO2 CH2O

oxidation

ATP ADP

energy

electrons

O2H2O

ATP ADP

CO2 CH2Oreduction

solarenergy

electrons

O2H2O

ATP ADP

Aerobic respirationPhotosynthesis

CO2 CH2O

oxidation

ATP ADP

O2H2O

CO2 CH2Oreduction

O2H2O

Preparing for next test

Online Quiz: available soon

Ch 10 Self-Quiz (# 1, 2, 5, 7, 9)

Ch 29 Self-Quiz (# 3, 4, 8, 9, 11)

Ch 35 Self-Quiz (# 3, 4, 6, 8)

Ch 36 Self-Quiz (# 2, 3, 7)