Photosynthesis and Cellular Respiration

Energy Use in Living Organisms  Step 1  Convert sunlight energy into chemical food energy  Ends in Glucose  Step 2  Convert chemical food energy into chemical energy that the cell can use  Ends in ATP

Adenosine Triphosphate (ATP) Adenine Three phosphate groups Ribose

Energy Cycle ATP is a charged battery for cell Made during cellular respiration Used up to complete activities for cell Energy in ATP is stored in high energy bonds between phosphate groups ADP is a used battery for cell one phosphate has been removed Phosphate must be added back on to recharge battery ADP ATP

ATP and ADP

What do Plants do?  Plants do step 1 with chloroplasts  Plants do step 2 with mitochondria  Because plants make their own food and then eat it, they are called autotrophs

What do Animals do?  Only do step 2 with mitochondria  Because animals must eat food that others have made, they are called heterotrophs

Step 1: Photosynthesis  Convert sunlight energy into glucose  Chloroplast performs photosynthesis  Plants, algae, some bacteria, and some protists all perform photosynthesis  Overall reaction  6CO 2 + 6H 2 O → C 6 H 12 O 6 + 6O 2  Occurs in two stages  Light dependent reactions  Light independent reactions

Chloroplast  Found only in Plant cells  Thylakoid- coin-shape structure containing chlorophyll and proteins; also called photosystems  Grana- stacks of thylakoids  Stroma- fluid inside chloroplast (similar to cytoplasm)

Light Dependent Reactions  Energy from sunlight is absorbed by chlorophyll and other pigments in the thylakoid membrane  Water is split into oxygen (given off as waste), H +, and electrons  Electrons go through a series of proteins in the membrane called the electron transport chain  Electrons provide energy for hydrogen protein pumps to pump H + into the thylakoid  More sunlight energy is absorbed  Electrons are added to NADP + to create NADPH  Hydrogen ion diffuse through another membrane protein  The diffusion fuels the production of ATP by the enzyme ATP synthase

Light Dependent Reactions

Light Independent Reactions  Occurs in the stroma  Also called the Calvin cycle  Is a series of reactions controlled by enzymes  The ATP and NADPH made during the light dependent reactions are used to fuel the reactions  CO 2 provides the carbon used to make the sugars  Simple sugars (primarily glucose) are made during the cycle

Light Independent Reactions

Factors that Affect Photosynthesis  Water  Water shortages can slow or stop photosynthesis  Plants in dry climates  Waxy coating  Thin leaves (needles on cactus)  Temperature  Low temps slow or stop photosynthesis  Enzymes do not work well at low temps

Factors that Affect Photosynthesis (cont)  Light Intensity/Amount  Increase in light, increase in photosynthesis until at maximum level  Plants still perform photosynthesis in periods without light  Density of Other Plants  Crowded plants complete for light and resources  Reduces photosynthesis

Cellular Respiration  Convert glucose into ATP  Mitochondria performs cellular respiration  All organisms  Process is called aerobic because it requires oxygen  Overall reaction  C 6 H 12 O 6 + 6O 2 → 6CO 2 + 6H 2 O

Mitochondria  Found in animals and plants  Outer and Inner membrane  Cristae- folding of inner membrane  Matrix- area inside of inner membrane

Glycolysis  Occurs in cytoplasm of cell  Anaerobic (oxygen not needed)  2 ATP’s are used to start the process  Glucose (a 6 carbon sugar) is broken into two three carbon sugars  4 ATP’s, 2 NADH’s, and 2 pyruvates are made

What comes next?  With oxygen  Other processes of cellular respiration occur in the mitochondria  Without oxygen  Fermentation occurs in the cytoplasm

Krebs Cycle  Occurs in the matrix  Pyruvate is broken into a 2 carbon molecule producing 2 NADH and CO 2  Coenzyme A attaches to the 2 carbon molecule and enters the Krebs cycle  It is converted into citric acid  Citric acid is broken down through a series of steps producing 3 more NADH’s. one ATP, one FADH 2, and two more CO 2 ’s  Two turns of the cycle are needed to process the 2 pyruvates from glycolysis

Krebs Cycle

Electron Transport Chain  Occurs along the inner membrane of the mitochondria  Electrons from NADH and FADH 2 are used  Electrons fuel hydrogen protein pumps which pump H + out of the matrix  H + diffuses through a membrane protein and fuels ATP production by ATP synthase  Oxygen picks up the electrons and H + to form water

Summary of Cellular Respiration

Fermentation  Occurs when oxygen in unavailable  In humans occurs as lactic acid fermentaion (some yeast and plants do alcohol fermentation)  Pyruvates are converted to lactic acid and NAD + is formed  No more ATP are produced

Comparison PsRs Function Make food for plants Make energy for ALL organisms Location in cell ChloroplastMitochondria Uses what? Water, CO2, Sunlight Oxygen, Food/Glucose Makes what? Oxygen, Food/glucose Water, CO2, Energy/ATP