Photosynthesisand

Cellular Respiration

Matter is recycled; energy is not.

Energy from the sun arrives on earth in the form of visible light, a type of

electromagnetic radiation

How objects appear different colors

White light is a mixture of all wavelengths (and colors) of light

Whitelight

Green lightIs reflected and transmitted

Red and blue lightIs absorbed

We see the Plant as green

Figure 10.6 Why leaves are green: interaction of light with chloroplasts

The wavelength of light a compound absorbs can be determined by a spectrophotometer

Energy Pathway: The Big Picture

Light energy from the sun

Chemical energy stored in glucose, fats, or carbohydrates

Chemical energy for use in the form of ATP

photosynthesis cellular respiration

Catabolism

Anabolism

Overview of Cellular Respiration

Glucose oxygen carbon waterdioxide

+ 6O2 6CO2 + +C6H12O6 6H2O energy

In mitochondria, the energy released from the catabolism of glucose is used to make ATP from ADP and Pi .The process is called phosphoryllation.

ADP + Pi + energy

ATP

Overview of Photosynthesis

Carbon water Glucose oxygen dioxide

+6CO2 + +C6H12O612H2O Solarenergy

+6O2 6H2O

In photosynthesis, energy from the sun (in packets called photons) is absorbed by pigment molecules (primarily chlorophyll) and used to produce glucose from CO2

Photoautotrophs: Use sunlight to produce food molecules; includes plants and cyanobacteria

Leaves contain millions of chloroplasts

Leaf cross-section Cells containing chloroplasts

Photosynthesis takes place in the chloroplasts of plant cells

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DAY TWO

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Photosynthesis Review

• Occurs in the chlorplast

• Chlorophyll and accessory pigments capture electromagnetic energy by absorbing photons of light.

• The energy from light is captured and converted to chemical energy which is stored in the bonds of a biomolecule.

• Chemical energy is harvested to make ATP during cellular respiration.

Am

ou

nt

of

lig

ht

abso

rbed

Chlorophyll a

400 600500 700

Chlorophyll b

Carotenoids

Wavelength of light (nm)

Different plant pigments absorb different wavelengths of light.

Pigments include chlorophyll (a and b), carotenoids, xanthophylls and anthocyanins.

Figure 10.9 Location and structure of chlorophyll molecules in plants

OutermembraneInnermembrane

Stroma

Thylakoids

Granum

Outer membrane Inner membrane Stroma

Granum Thylakoid

Pigments are found in chloroplasts.

Factors affecting the rate of photosynthesis

*LIGHT INTENSITY *TEMPERATURE *CO2 LEVEL

Photosynthesis: The Big Picture

• Light Dependent Reactions– Occur in thylakoid membranes of grana– Energy from the high energy electron of chlorophyll

is used to make ATP and NADPH

• Light Independent Reactions (Calvin Cycle)– Occur in enzyme-rich stroma– ATP and NADPH are used to make glucose

from CO2 (carbon fixation)

12 H2O6CO2 + ++ Lightenergy

C6H12O6 6O2 6 H2O+

Photosynthesis Equation

Two components:

Lightenergy

H2O O2

Light-dependent reactions

Chemical energy(ATP, NADPH)

Chemical energy(ATP, NADPH)

CO2

Light-independent reactions

Chemical energy(C6 H12O6)

Energy Harvest Synthesis

e–

e–

Photons

0 1 2

Energy state of electrons in chlorophyll

Electrons can be promoted to discrete high-energy states:

Blue photons excite electrons to ahigher energy state

Red photons excite electrons to a high-energy state

When a photon of light strikes chlorophyll, an electron can be

promoted to a higher energy state

Light excites e- in chl.a in PSII

e- move to electron acceptor

e- transferred along electron transport chain; as they lose energy, H+ protons move into thylakoid

Light excites e- in chl a of PSI.

E- from PSI enter second e.t.c. which ends by making NADPH

Moving Electrons

• LEO = lose electrons “oxidized”

• GER = gain electrons “reduced”

OR

OIL RIG

Oxidized is lost ……….Reduced is gained

Replacing electrons

• Water molecules inside the thylakoid membranes are split by an enzyme

• Process is called photolysis

• Results:

• 2H2O 4H+ + 4e- + O2

Chemiosmosis

The movement of protons (H+) into the stroma releases energy which is used to phosphoryllate ADP + Pi to form ATP.

SUMMARY

Alternative Carbon Pathways

• C3 plants = Fix carbon exclusively through the Calvin cycle (see previous slide)

• C4 plants = used when CO2 levels are low (hottest part of the day, stomates closed)– Includes corn, sugar cane, grasses– Can produce same amount of carbs with half the water

loss

• CAM plants = “crussulacean acid metabolism”– CO2 incorporated into organic acids at night and released

for fixation during the day– Includes cacti, pineapples

Cellular Respiration Overview

Glycolysis

• Occurs in the cytoplasm• Use 2 ATP to break 6-carbon sugar into two 3-carbon

pyruvate; produces 4 ATP (net gain of 2) and 2 NADH• If oxygen present, pyruvates continue to Krebs cycle• If no oxygen present, pyruvates continue to fermentation

(lactic acid or alcohol)

Alcohol fermentation: no oxygen present

• Pyruvate is converted to ethanol and CO2 is released.

• Glycolysis is believed to have been what ancient prokaryotes used for energy production long before oxygen levels were high enough to support electron transport chain.

Lactic Acid fermentation

• Pyruvate is directly reduced by NADH to form lactate. (NADH becomes NAD+)

• Used in human muscle cells when there is not enough oxygen getting to the muscles such as during strenuous exercise. A chemical pathway removes lactic acid as oxygen becomes available.

The Krebs cycle is the first part of cellular respiration.

• Pyruvate is oxidized to form acetyl CoA– carbon dioxide released– NADH produced– coenzyme A (CoA)

bonds to two-carbon molecule

The Krebs cycle

• Produces energy-carrying molecules includingATPNADH andFADH2

• Citric acid is formed and CO2 is released

Electron Transport Chain

• The second part of cellular respiration when protein carriers are used to make NADH and FADH2 and ATP.

– high-energy electrons enter electron transport chain

– energy is used to transport hydrogen ions across the inner membrane

– hydrogen ionsflow through achannel in themembrane

– One glucose nets up to 36 ATP

– Water is released as a waste product.