Where It Starts: Photosynthesis
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Transcript of Where It Starts: Photosynthesis
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