Concept 8.1 Photosynthesis uses light energy to make food

Key Terms

• chloroplast: organelle found in some plant cells and certain unicellular organisms where photosynthesis takes place
  
• chlorophyll: pigment that gives a chloroplast its green color; uses light energy to split water molecules during photosynthesis 
  
• stroma: thick fluid contained in the inner membrane of a chloroplast
  
• thylakoid: disk-shaped sac in the stroma of a chloroplast; site of the light reactions of photosynthesis
• light reactions: chemical reactions that convert the sun's energy to chemical energy; take place in the membranes of thylakoids in the chloroplast
  
• Calvin cycle: cycle in plants that makes sugar from carbon dioxide, H+ ions, and high-energy electrons carried by NADPH

Photosynthesis feature:

• Photosynthesis takes place chloroplast
  
• Chlorophast contain chlorophyll, make green
  
• Leaves are major site of photosynthesis
  

Structure of a leaf:

• In a leaf, chloroplast concentrated in mesophyll
  
• Stomata (stoma) on surface of leaf
  
• CO2 enter and O2 exit through stomata
  
• Veins branch in leaf, deliver produce of leaf to other parts
  

Structure of chloroplast:

• Inner and outer membrane
  
• Inner holds thick fluid, stroma
  
• Stroma suspend thylakoid, disk-shaped stacked in grana (granum)
  
• Chemical reactions in thylakoid membrane or stroma
  

Photosynthesis:

• Cellular respiration of falling e-
  
• Photosynthesis rise of e-, by energize sunlight
  
• Chloroplast use excited e- and p+ to produce glucose
  
• Of light reactions and Calvin cycle

Light reactions:

• Convert energy of sunlight to chemical energy, NADPH and ATP
  
• Need molecules in membrane thylakoid
  
• Chlorophyll molecules in membrane capture light energy
  
• Chloroplast use energy remove e- from H2O, waste O and p+
  
• O2 leave through stomata
• Left e- and p+ used make NADPH, e- carrier similar NADH
  
• Chloroplast also use energy make ATP
  

Calvin cycle:

• Make sugar from CO2, p+, e- from NADPH
  
• Enzymes for Calvin cycle outside thylakoid, dissolved in stroma
  
• ATP made by light reaction used make sugar
  
• AKA "light-independent reactions," not directly need light
  

Concept check:

1. Draw and label a simple diagram of a chloroplast that includes the following structures: outer and inner membranes, stroma, thylakoids.

2. What are the reactants for photosynthesis? What are the products?

Reactants CO2 and H2O, products glucose and O2.

3. Name the two main stages of photosynthesis. How are the two stages related?

Light reactions and Calvin cycle, supply chain. Calvin cycle requires energy produced during the light reactions. Both work together to make glucose for cellular respiration.