Where It Starts: Photosynthesis

1
Where It Starts Photosynthesis

• Chapter 5

2
Sunlight and Survival

• Autotrophs use nonliving sources to build their
  own food
• Heterotrophs feed on living organisms or their
  remains

3
Sunlight and Survival

• Photoautotrophs use sunlight and CO2 to produce
  sugar in the process of photosynthesis
• plants, algae and photosynthetic bacteria

4
Visible Light

• Wavelengths humans perceive as different colors
• Violet (380 nm) to red (750 nm)
• Longer wavelengths, lower energy

5
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?

6
Variety of Pigments

• Chlorophylls
• Carotenoids
• Anthocyanins
• Phycobilins

7
Fig. 5-2, p.74
8
Photosynthesis Equation
LIGHT ENERGY
12H2O 6CO2
6O2 C6H12O6 6H2O
water
carbon dioxide
oxygen
glucose
water
9
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

10
sunlight energy
H2O (water)
CO2 (carbon dioxide)
ATP
light- dependent reactions
light- independent reactions
ADP Pi
glucose
O2
H2O (metabolic water)
11
Chloroplast
Organelle of photosynthesis in plants and algae
two outer membranes
stroma
inner membrane system
(thylakoids connectedby channels)
12
Summary of Photosynthesis
sunlight
Light Dependent Reactions
6O2
12H2O
ATP
NADP
ADP Pi
NADPH
6CO2
Calvin- Benson cycle
Light Independent Reactions
6 RuBP
12 PGAL
6H2O
phosphorylated glucose
P
end products (e.g., sucrose, starch, cellulose)
13
Carbon and Energy Sources

• Photoautotrophs
• Carbon source is carbon dioxide
• Energy source is sunlight
• Heterotrophs
• Get carbon and energy by eating autotrophs or
  one another

14
How Cells Release Chemical Energy

• Chapter 6

15
ATP Is Universal Energy Source

• 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

16
Making ATP

• Plants make ATP during photosynthesis
• Cells of all organisms make ATP by breaking down
  carbohydrates, fats, and protein

17
Main Types of Energy-Releasing Pathways

• Aerobic pathways
• Require oxygen

• Anaerobic pathways
• No Oxygen required

18
Summary Equation for Aerobic Cellular Respiration

• C6H1206 6O2 6CO2 6H20 ATP
• glucose oxygen carbon
  water dioxide

19
Glucose

• A monosaccharide or simple sugar
• (C6H12O6)
• Why is Glucose so important in the blood of
  animals?

20
Overview of Aerobic Respiration
CYTOPLASM
glucose
ATP
4
2
ATP
Glycolysis
(2 ATP net)
e- H
2 pyruvate
2 NADH
e- H
2 CO2
2 NADH
e- H
4 CO2
8 NADH
Krebs Cycle
e- H
2
ATP
2 FADH2
e-
Electron Transfer Phosphorylation
32
ATP
water
H
e- oxygen
Typical Energy Yield 36 ATP
21
Fermentation Pathways

• Begin with glycolysis
• Are anaerobic dont require oxygen
• Yield only the 2 ATP from glycolysis

22
Lactate Fermentation
GLYCOLYSIS
C6H12O6
ATP
2
energy input
2 NAD
2 ADP
NADH
2
ATP
4
2 pyruvate
energy output
2 ATP net
LACTATE FORMATION
electrons, hydrogen from NADH
2 lactate
23
Alcoholic Fermentation
GLYCOLYSIS
C6H12O6
ATP
2
2 NAD
energy input
2 ADP
NADH
2
ATP
4
2 pyruvate
energy output
2 ATP net
ETHANOL FORMATION
2 H2O
2 CO2
2 acetaldehyde
electrons, hydrogen from NADH
2 ethanol
24
Linked Processes

• Photosynthesis
• Energy-storing pathway
• Releases oxygen
• Requires carbon dioxide

• Aerobic Respiration
• Energy-releasing pathway
• Requires oxygen
• Releases carbon dioxide