Where It Starts: Photosynthesis

Chapter 5

Sunlight and Survival

• Autotrophs use nonliving sources to build their own food

• Heterotrophs feed on living organisms or their remains

Sunlight and Survival

• Photoautotrophs use sunlight and CO2 to produce sugar in the process of photosynthesis

• plants, algae and photosynthetic bacteria

Visible Light

• Wavelengths humans perceive as different colors

• Violet (380 nm) to red (750 nm)

• Longer wavelengths, lower energy

Pigments

• Color you see is the wavelengths not absorbed

So, Why do we see plants as green?

Why do we see plants as other colors in fall and winter?

Variety of Pigments

Chlorophylls

Carotenoids

Anthocyanins

Phycobilins

Fig. 5-2, p.74

Photosynthesis Equation

12H2O + 6CO2 6O2 + C6H12O6 + 6H2O

water carbon dioxide

oxygen glucose water

LIGHT ENERGY

Two-Step Process

Light-dependent reactions

• formation of ATP

Light-independent reactions

• Synthesis part of photosynthesis (synthesis of glucose)

• Can proceed in the dark using energy stored in the light reactions

• Calvin-Benson cycle

sunlightenergy

H2O(water)

ATP

O2 H2O (metabolic water)

light-dependentreactions

light-independent

reactions

glucose

ADP + Pi

CO2

(carbon dioxide)

Chloroplast

two outer membranes

inner membrane system(thylakoids connectedby channels)

stroma

Organelle of photosynthesis in plants and algae

Summary of Photosynthesis

12H2O

sunlight

Calvin-Benson

cycle

6O2

LightDependentReactions

LightIndependent

Reactions

NADP+ADP + Pi

6 RuBP 12 PGAL

P

end products (e.g., sucrose, starch, cellulose)

phosphorylated glucose

6H2O

6CO2

ATP NADPH

• Photoautotrophs

– Carbon source is carbon dioxide

– Energy source is sunlight

• Heterotrophs

– Get carbon and energy by eating

autotrophs or one another

Carbon and Energy Sources

How Cells Release Chemical Energy

Chapter 6

• Photosynthesizers get energy fromthe sun

• Animals get energy second- or third-hand from plants or other organisms

• Regardless, the energy is converted to the chemical bond energy of ATP

ATP Is Universal Energy Source

Making ATP

• Plants make ATP during photosynthesis

• Cells of all organisms make ATP by

breaking down carbohydrates, fats, and

protein

Main Types of Energy-Releasing Pathways

Aerobic pathways

• Require oxygen

Anaerobic pathways

• No Oxygen required

Summary Equation for Aerobic Cellular Respiration

C6H1206 + 6O2 6CO2 + 6H20 + ATP

glucose oxygen carbon water dioxide

• A monosaccharide or simple sugar

(C6H12O6)

• Why is Glucose so important in the blood of animals?

Glucose

Overview of Aerobic Respiration

CYTOPLASM

Glycolysis

Electron Transfer

Phosphorylation

Krebs Cycle ATP

ATP

2 CO2

4 CO2

2

32

water

2 NADH

8 NADH

2 FADH2

2 NADH 2 pyruvate

e- + H+

e- + oxygen

(2 ATP net)

glucose

Typical Energy Yield: 36 ATP

e-

e- + H+

e- + H+

ATP

H+

e- + H+

ATP2 4

Fermentation Pathways

• Begin with glycolysis

• Are anaerobic: don’t require oxygen

• Yield only the 2 ATP from glycolysis

Lactate Fermentation

C6H12O6

ATP

ATPNADH

2 lactate

electrons, hydrogen from NADH

2 NAD+

2

2 ADP

2 pyruvate

2

4

energy output

energy input

GLYCOLYSIS

LACTATE FORMATION

2 ATP net

Alcoholic Fermentation

C6H12O6

ATP

ATPNADH

2 acetaldehyde

electrons, hydrogen from NADH

2 NAD+

2

2 ADP

2 pyruvate

2

4

energy output

energy input

GLYCOLYSIS

ETHANOL FORMATION

2 ATP net

2 ethanol

2 H2O

2 CO2

Linked Processes

Photosynthesis

• Energy-storing pathway

• Releases oxygen

• Requires carbon dioxide

Aerobic Respiration

• Energy-releasing pathway

• Requires oxygen

• Releases carbon dioxide