Science Science

Energy flows between organisms in living systems 

  • directly/indirectly almost all energy comes from the sun

  • Sunlight is captured and used to make compounds (carbohydrates/glucose)

Building molecules that store energy

  • Photosynthesis - the process by which light energy is converted to chemical energy

  • Autotrophs - organisms that use energy from sunlight or inorganic substances to make organic compounds

Breaking down food for energy

  • Heterotrophs - organisms that must get energy from eating other plants/animals

  • cellular respiration - the process in which living things break down food (glucose) for energy

Cells transfer energy from food to APT

  • When cells break down food, some energy is released as heat; much is stored temporarily in ATP

  • ATP - adenosine triphosphate - energy currency of the cell (ADP)

Atp stores and releases energy

  • Energy is released when ATP bonds break

  • Breaking of bond takes a small amount of energy, but more energy is released by the breaking of the bond

  • ATP → ADP + P + energy

Photosynthesis chapter 5.2

The 2 stages of photosynthesis

  • Light dependent reactions:

     -convert light energy to chemical energy (ATP + NADPH) and produce oxygen gas as a waste product 

  • Light independent reactions (calvin cycle) : 

  • Make sugar using carbon dioxide and the energy containing products of the light reactions (ATP + NADPH)

light reactions

  • Must have sunlight and H2O

  • Occurs in the thylakoid of the chloroplast

  • Oxygen and ATP/NADPH is made 

Production of oxygen waste 

  • Sunlight strikes thylakoid and excite electrons

  • Electrons jump to different part of thylakoid to be used in the light independent reactions 

  • Water molecules are split by an enzyme and electrons are taken from hydrogen atoms, leaving H*, and oxygen is produced as waste

The creation of ATP/NADPH

  • Excited electrons (from oxygen production) are passed through the thylakoid membrane in a structure called the electron transport chain

Production of ATP/ NADPH….

  • As electrons are passed in the ETC - they lose energy - the energy goes to pumping H+ into the thylakoid

  • Creates a concentration gradient of H+

  • As H+ diffuses back out of the thylakoid, creating ADP into ATP

  • Another electron transport chain takes H+ and attaches it to another electron receptor NADP+, making NADPH

Light independent reactions (dark reactions/ calvin cycle)

  • Carbon atoms from carbon dioxide are used to make organic compounds where energy is stored called carbon dioxide fixation

Calvin cycle/light independent 

  • Occurs in the stroma

  • Most common method for carbon fixation is the calvin cycle 

  • Produces a three carbon sugar

Factors that affect photosynthesis

  • Light - up to the point of using all the pigments (saturated level)

  • Concentration of CO2 available 

  • temperatures