Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Explain the process of...

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

• Explain the process of aerobic cellular respiration.

• (Total 8 marks)


• glucose is broken down to pyruvate in the cytoplasm;with a small yield of ATP / net yield of 2 ATP;and NADH + H+ / NADH;aerobic respiration in the presence of oxygen;pyruvate converted to acetyl CoA;acetyl CoA enters Krebs cycle;Krebs cycle yields a small amount of ATP / one ATP per cycle;and FADH2 / FADH + H+ / NADH / NADH + H+ / reduced compounds / electron collecting molecules;these molecules pass electrons to electron transport chain;oxygen is final electron acceptor / water produced;electron transport chain linked to creation of an electrochemical gradient;electrochemical gradient / chemiosmosis powers creation of ATP;through ATPase;

• [8]


PowerPoint Lectures forBiology: Concepts and Connections, Fifth Edition – Campbell, Reece, Taylor, and Simon

Lectures by Chris Romero

Chapter 7Chapter 7Chapter 7Chapter 7

Photosynthesis: Photosynthesis:

Using Light to Make Using Light to Make FoodFood


• Photosynthesis is the process by which certain organisms use light energy

– To make sugar and oxygen gas from carbon dioxide and water

Lightenergy

PHOTOSYNTHESIS

6 CO2 6+ H2O

Carbon dioxide Water

C6H12O6 6+ O2

Glucose Oxygen gas


• As the human demand for energy grows

– Fossil fuel supplies are dwindling

• Energy plantations

– Are being planted to serve as a renewable energy source


AN OVERVIEW OF PHOTOSYNTHESIS

7.1 Autotrophs are the producers of the biosphere

• Plants are autotrophs

– Producing their own food and sustaining themselves without eating other organisms


• Plants, algae, and some bacteria are photoautotrophs

– Producers of food consumed by virtually all organisms

Figure 7.1A–D


7.2 Photosynthesis occurs in chloroplasts

• In plants, photosynthesis

– Occurs primarily in leaves, in chloroplasts, which contain stroma, and stacks of thylakoids called grana

Figure 7.2

Leaf Cross Section

Leaf

Mesophyll Cell

Mesophyll

VeinStoma

CO2O2

Chloroplast

Chloroplast

Grana Stroma

TE

M 9

,750

Stroma

Granum Thylakoid Thylakoidspace

OutermembraneInnermembrane

Intermembranespace

LM 2

,600

http://media.pearsoncmg.com/bc/bc_campbell_concepts_5/media/assets/interactivemedia/activityshared/ActivityLoader.html?c6e&10&01&7A%20The%20Sites%20of%20Photosynthesis


7.3 Plants produce O2 gas by splitting water

• The O2 liberated by photosynthesis

– Is made from the oxygen in water

Reactants:

Products:

6 CO2 12 H2O

C6H12O6 6 H2O 6 O2

Labeled

Experiment 1

Experiment 2

6 CO2 12 H2O

6 CO2 12 H2O

C6H12O6 6 H2O 6 O2

Notlabeled

C6H12O6 6 H2O 6 O2

+

+

+

+

+

+

Figure 7.3A–C


7.4 Photosynthesis is a redox process, as is cellular respiration

• In photosynthesis

– H2O is oxidized and CO2 is reduced

Figure 7.4A, B Reduction

Oxidation

6 O2 6 H2O

Reduction

Oxidation

6 O26 CO2 6 H2O C6H12O6

C6H12O6 6 CO2


7.5 Overview: Photosynthesis occurs in two stages linked by ATP and NADPH

• The complete process of photosynthesis consists of two linked sets of reactions

– The light reactions and the Calvin cycle

http://media.pearsoncmg.com/bc/bc_campbell_concepts_5/media/assets/interactivemedia/activityshared/ActivityLoader.html?c6e&10&02&7B%20Overview%20of%20Photosynthesis


• Light-dependent reactions

– Convert light energy to chemical energy and produce O2

• Light-independent (Calvin cycle) assembles sugar molecules from CO2

– Using ATP and NADPH from the light reactions

Figure 7.5

Light

CO2H2OChloroplast

LIGHTREACTIONS

(in thylakoids)

CALVINCYCLE

(in stroma)

NADP+

ADP+ P

ATP

NADPH

O Sugar

Electrons


7.7 Photosystems capture solar power

• Thylakoid membranes contain multiple photosystems

– absorb light energy, which excites electrons

Figure 7.7A


• Each photosystem consists of

– Light-harvesting complexes of pigments

– A reaction center with a primary electron acceptor that receives excited electrons from a reaction-center chlorophyll

Figure 7.7B, C

Ene

rgy

of e

lect

ron

Photon

Excited state

Heat

Photon(fluorescence)

Ground state

Chlorophyllmolecule

e–

Photosystem

Light-harvestingcomplexes

Reactioncenter

Primary electronacceptor

e–

To electrontransport chain

Pigment molecules

Chlorophyll a moleculeTransfer of energy

Photon

Thy

lako

id m

embr

ane

Online Lab: Chromatography


7.8 In the light-dep. reactions, electron transport chains generate ATP and NADPH

• Two connected photosystems absorb photons of light

– transfer energy to chlorophyll P680 and P700

http://media.pearsoncmg.com/bc/bc_campbell_concepts_5/media/

assets/interactivemedia/activityshared/ActivityLoader.html?c6e&10&04&7D%20The%20Light

%20Reactions


• excited electrons

– passed from primary e- acceptor to electron transport chains

Figure 7.8A

Thylakoidspace

Photon

Stroma

Th

yla

koid

me

mb

ran

e

1

Photosystem II

e–

P680

2

H2O 12

+ 2O2 H+

3

ATPElectron transport chainProvides energy for synthesis of

by chemiosmosis

4

Photosystem I

Photon

P700

e–

5

+NADP+ H+ NADPH

6


• Electrons shuttle from photosystem II to I

– Providing energy to make ATP

• Electrons from photosystem I

– Reduce NADP+ to NADPH

Figure 7.8B

e–

ATP

MillmakesATP

Pho

ton

Pho

ton

Photosystem II Photosystem I

NADPHe–

e–e–

e–

e–

e–


• Photosystem II regains electrons by splitting water

– Releasing O2


7.9 Chemiosmosis powers ATP synthesis in the light reactions

• The electron transport chain

– Pumps H+ into the thylakoid space from the stroma


Chloroplast

Stroma (low H+ concentration)

Light Light

NADP+ + H+ NADPH

H+

H+

H+H+

ATPPADP +

Thylakoidmembrane

H2O 12

O2 2 H+ H+H+

H+ H+

H+

H+

H+ H+

H+

H+

Photosystem II Electrontransport chain

Photosystem I ATP synthase

Thylakoid space(high H+ concentration)

+

• diffusion of H+ back across the membrane through ATP synthase

– Powers phosphorylation of ADP to produce ATP (photophosphorylation)

Figure 7.9


THE CALVIN CYCLE: CONVERTING CO2 TO SUGARS7.10 ATP and NADPH power sugar synthesis in the Calvin cycle

• Calvin cycle (Light-Independent Reactions)

– Occurs in the chloroplast’s stroma

– Consists of carbon fixation, reduction, release of G3P, and regeneration of RuBP

Figure 7.10A

InputCO2

ATPNADPH

CALVINCYCLE

G3POutput:

http://media.pearsoncmg.com/bc/bc_campbell_concepts_5/media/

assets/interactivemedia/activityshared/ActivityLoader.html?c6e&10&05&7E%20The%20Calvin

%20Cycle


• Using carbon from CO2, electrons from NADPH, and energy from ATP

– The cycle constructs G3P, which is used to build glucose and other organic molecules

Figure 7.10B

CALVINCYCLE

3

3 P

CO2

Step Carbon fixation. An enzymecalled rubisco combines CO2 with a five-carbon sugar called ribulose bisphosphate (abbreviated RuBP). The unstable product splits into two molecules of the three-carbon organic acid, 3-phosphoglyceric acid (3-PGA). For three CO2 entering, six 3-PGA result.

1 Input:In a reactioncatalyzed by rubisco,CO2 is added to RuBP.

P 6 PRuBP 3-PGA

1

G3P

6 P

2Step Reduction. Two che-mical reactions (indicated by the two blue arrows) consume energy from six molecules of ATP and oxidize six molecules of NADPH. Six molecules of 3-PGA are reduced, producing six molecules of the energy-rich three-carbon sugar, G3P

6 ATP

6 ADP + P

6 NADPH

6 NADP+

2

3Step Release of one molecule of G3P. Five of the G3Ps from step 2 remain in the cycle. The single molecule of G3P you see leaving the cycle is the net product of photosynthesis. A plant cell uses two G3P molecules to make one molecule of glucose.

Output: 1 PG3P

Glucoseand othercompounds

3

3

3 ADP

ATP

4Step Regeneration of RuBP. A series of chemical reactions uses energy from ATP to rearrange the atoms in the five G3P molecules (15 carbons total), forming three RuBP molecules (15 carbons).These can start another turn of the cycle.

5 P

G3P

4


PHOTOSYNTHESIS REVIEWED AND EXTENDED7.11 Review: Photosynthesis uses light energy to make food molecules

Figure 7.11

Light

H2O CO2

NADP+

Photosystem II

Photosystem I

Electrontransport

chains

ADPP+

RUBP

CALVINCYCLE

(in stroma)3-PGA

Stroma

G3PNADPH

ATP

O2

LIGHT REACTIONS CALVIN CYCLE

Sugars

Cellular respiration

Cellulose

Starch

Other organiccompounds

Thylakoidmembranes

Chloroplast


7.12 C4 and CAM plants have special adaptations that save water

• In C3 plants a drop in CO2 and rise in O2 when stomata close on hot dry days

– Divert the Calvin cycle to photorespiration


• C4 plants first fix CO2 into a four-carbon compound

– That provides CO2 to the Calvin cycle

Figure 7.12 (left half)

Sugarcane

C4 plant

CALVINCYCLE

3-C sugar

CO2

4-C compound

CO2Mesophyll cell

Bundle-sheath cell


• CAM plants open their stomata at night

– Making a four-carbon compound used as a CO2 source during the day

CO2

Figure 7.12 (right half) CAM plant

Day

CALVINCYCLE

3-C sugar

CO2

4-C compound

Night

Pineapple

CO2


Discovery Video: Space Plants

http://media.pearsoncmg.com/bc/bc_campbell_essentials_3/discvids/_html/index.htm?info_text=cc5_space_plants


Boy, I’d like to jump out and go

swimming. Oh wait, I don’t like to

swim…Hmmm.


THE LIGHT REACTIONS: CONVERTING SOLAR ENERGY TO CHEMICAL ENERGY

7.6 Visible radiation drives the light reactions

• Certain wavelengths of visible light, absorbed by pigments

– Drive the light reactions of photosynthesis

Figure 7.6A, B

Increasing energy

10–5 nm 10–3 nm 1 nm 103 nm 106 nm 1 m 103 m

Gammarays

X-rays UV Infrared Micro-waves

Radiowaves

Visible light

400 500 600 700 750

650nm

Wavelength (nm)

Transmittedlight

Absorbedlight

Reflectedlight

Light

Chloroplast

380


PHOTOSYNTHESIS, SOLAR RADIATION, AND EARTH’S ATMOSPHERE CONNECTION

7.13 Photosynthesis moderates global warming

• Greenhouses used to grow plants

– Trap solar radiation, raising the temperature inside

Figure 7.13A


• Excess CO2 in the atmosphere

– Is contributing to global warming

Figure 7.13B

Sunlight

ATMOSPHERE

Some heatenergy escapesinto space

Radiant heattrapped by CO2

and other gases


• Photosynthesis, which removes CO2 from the atmosphere

– Moderates this warming


TALKING ABOUT SCIENCE

7.14 Mario Molina talks about Earth’s protective ozone layer

Figure 7.14A


• Solar radiation converts O2 high in the atmosphere to ozone (O3)

– Which shields organisms on the Earth’s surface from the damaging UV radiation


• Industrial chemicals called CFCs have caused dangerous thinning of the ozone layer

– But international restrictions on CFC use are allowing recovery

Figure 7.14B

Southern tip ofSouth America

Antarctica

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