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