Photosynthesis and Cell Respiration Unit 5

Energy in the Cell All cells require energy Adenosine triphosphate (ATP) is the “energy currency” in the cell. ATP is usable energy that the cell can use to do work.

ATP Enzymes break high energy bond between phosphates to release energy This creates ADP and phosphate (P) ATPADP

Photosynthesis Autotrophs capture light energy from the sun and store it as chemical energy in bonds of glucose. Carbon dioxide + water + light  glucose + oxygen CO 2 + H 2 O + light  C 6 H 12 O 6 + O 2

Chloroplast Structure Photosynthesis is carried out in the chloroplast. Thylakoids – folded stacks of inner membrane Stroma – fluid around thylakoids

Step 1: Light Dependent Reactions In the thylakoids, the pigment chlorophyll absorbs light energy. This process splits a water molecule into H and O. The H from water is added to a low-energy molecule of NADP+, which converts it into high-energy NADPH. The O 2 is released as a byproduct. NADPH is an electron carrier – it will take energy to the next step.

Step 2: Light Independent Reactions (aka Calvin Cycle) In the stroma, energy from the NADPH is used to put together carbon dioxide molecules into a high-energy glucose molecule. This is called carbon fixation. The NADPH loses its H and NADP+ is cycled back to the light dependent reactions

Carbon fixation – taking low energy inorganic molecules and putting them together into high energy organic sugar molecules – makes all life on earth possible!!!!

0 Light Energy H 2 O CO 2 Thylakoids Light Dependent Reactions Light Independent (Dark) Reactions Glucose O2O2 Stroma NADPH NADP+

How much energy does glucose contain? Gummy Bear Video

Cell Respiration C 6 H 12 O 6 + O 2  CO 2 + H 2 O + ATP Carbon dioxide glucose + oxygen  + water + ATP Cells break down glucose to create usable energy – ATP

Mitochondria Structure Cell Respiration occurs in the mitochondria, which has a specialized structure. The outer membrane surrounds the organelle The inner membrane is folded into deep folds called cristae The space between the two membranes is called the inter- membrane space. The space inside the inner membrane is called the matrix.

Step 1: Glycolysis Occurs in the cytoplasm The 6-carbon sugar glucose is broken in half to form two 3-carbon sugar pyruvate molecules Breaking this bonds creates 2 ATP and 2 NADH (electron carriers)

Step 2: Kreb’s Cycle In the mitochondrial matrix, pyruvate molecules are broken down into CO 2 molecules. The energy is used to make many NADH and FADH 2, which carry energy to the next step. The CO 2 molecules are released as waste.

Step 3: Electron Transport Chain Energy from NADH and FADH 2 is used to pump H+ into the inter-membrane space. This sets up a concentration gradient where H+ is more concentrated in the inner- membrane space than the matrix.

Step 3: Electron Transport Chain H+ flows down its concentration gradient from the intermembrane space into the matrix. This powers the ATP Synthase enzyme, which combines ADP and P into ATP molecules. Produces 34 ATP ATP Synthase Animation

2 Pyruvate Glucose O2O2 CO 2 H2OH2O Glycolysis Electron Transport Chain NADH 32 ATP 2 ATP Kreb’s Cycle 2 ATP

34 ATP ATP SYNTHASE O2O2 CO 2 H2OH2O 2 ATP

Anaerobic Respiration Occurs when there is no O 2 available. The purpose is to use NADH to regenerate NAD+ so that glycolysis can continue occurring. Only makes 2 ATP. Also called fermentation Types: – Lactic Acid – burning feeling in muscles during exercise – Alcoholic – yeast make bread, wine, beer Glycolysis Fermentation Glucose Pyruvate 2 ATP Lactic Acid OR Alcohol

Photosynthesis and Cell Respiration Complementary processes for cycling carbon dioxide and oxygen and transferring energy. O 2, GlucoseCO 2, Water ATP sunlight Photosynthesis Cell Respiration

Recap The whole point of these processes is to create ATP to use energy in the cell The series of energy conversions link the ultimate source of energy (the sun) to the energy needs of living things

Glucose