Overview of Photosynthesis

photosynthesis basics

equation for photosynthesis: 6CO2 + 6H2O = C6H12O6 + 6O2

• H2O provides the hydrogen for glucose and excess oxygen to be put out into the atmosphere
• CO2 provides the carbon and oxygen for the glucose
• sunlight is the ultimate source of energy that powers cells

basics of photosynthesis

• plants use carbon dioxide, water, and energy from sunlight to produce glucose through light and dark reactions of photosynthesis
• examples of pigments include chlorophylls, xanthophylls, anthocyanins and carotenoids

there are two steps in photosynthesis: the light and dark reactions

• light (sunlight-dependent) reaction
• takes place in the thylakoids of each granum
• must occur in the light
• sunlight is absorbed by chlorophyll and the rest of the pigments
• water is absorbed by the roots + root hairs
• energy from the sunlight is harnessed and used to split up the water molecule
• oxygen is released into the atmosphere, the hydrogen is stored in NADP which now becomes NADPH
• during this process, ATP is generated to be used later
• light energy is converted to chemical energy in the form of 2 compounds: NADPH and ATP
• NADPH is a source of energized electrons (H)
• ATP is the versatile energy currency of cells
• chlorophyll absorbs photons of light
• dark reaction (calvin cycle)
• takes place in the stroma of a chloroplast
• this can occur regardless of weather as long as the products of the light reactions (NADPH and ATP) are present
• carbon fixation occurs - incorporating carbon dioxide from the air into molecules already present in the chloroplast
• enzyme: rubisco → grabs CO2 and lets hydrogen attach to it; → prepares carbon to make sugar
• glucose is formed by the C and O from CO2 and the H from NADPH
• ATP provides the energy needed to put the ingredients together
• ultimately, glucose is produced

key terms

parts of the cell / parts of the chloroplast

• chloroplast: organelle containing chlorophyll
• chlorophyll: green pigment that traps light during photosynthesis; does not absorb green light
• thylakoids: flattened disks within chloroplasts in which light reactions occur
• granum: stacks of thylakoids in the cytoplasm

reactants + products of photosynthesis

• reactants -
  • carbon dioxide: provides the carbon and oxygen in glucose
  • water: provides oxygen for humans to breathe and hydrogen for glucose
• products -
  • glucose: simple sugar; the end product of photosynthesis
  • oxygen: produced for consumption of humans and animals to breathe
• other
  • pigments: substances that absorb sunlight

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