Photosynthesis and Cellular Respiration

How do cells obtain organic compounds for energy? Heterotrophs: Cannot make their own food Autotrophs: Can make their own food – Photoautotrophs: Use energy from the sun (photosynthesis) to produce organic compounds (glucose) Plants, algae and some bacteria – Chemoautotrophs: Use energy stored in inorganic compounds (chemosynthesis) to produce organic compounds Some bacteria found at the hydrothermal vents of the seafloor

Photosynthesis Method of converting light energy from the sun into chemical energy that cells can use – Divided into the light-dependent and light-independent reactions Photosynthesis takes place in chloroplasts – The parts of a chloroplast are as follows: Thylakoids- disk-shaped structures that contain the pigment chlorophyll (absorbs the sunlight) Grana- A stack of thylakoids Stroma- Liquid between grana

Draw a Chloroplast

Overall Photosynthesis Reaction 6CO H 2 O + light energy → C 6 H 12 O 6 + 6O 2 On the left of the arrow are the reactants (the components that “react” together). On the right of the arrow are the products. Identify how a plant obtains the reactants.

Photosynthesis Practice You and a partner need: – 6 orange circles = C – 12 light green triangles = H – 18 pink squares = O – 1 large dark green oval = thylakoid – 1 small dark green rectangle = ATP – 1 small dark green rectangle = NADPH – 1 yellow circle = sun

Light-dependent Reactions Chlorophyll (in thylakoids) absorbs the light energy – Plants have 2 types: Chlorophyll A and Chlorophyll B Water molecules are split apart producing H and O 2 Electrons flow throughout the thylakoid membrane (electron transport chain) Energy compounds ATP and NADPH are produced

Light-independent Reactions (Dark Reactions) Occur in the stroma ATP and NADPH from the light reactions are used to fuel the break down of CO 2 and the reassembling of the atoms to produce glucose. This reassembling is called “carbon fixation”. Carbon fixation occurs in a series of reactions called the Calvin Cycle.

Getting energy out of food Plants and animals both use glucose from photosynthesis for cell fuel. Glucose (or other carbs), proteins, and fats are not a form of energy that our cells can use. Cellular respiration converts glucose into a usable energy form (ATP) for cells.

Cellular Respiration Overview The reactions of cellular respiration occur the same way in plants and animals. Overall Reaction: C 6 H 12 O 6 + 6O 2 → 6CO 2 + 6H 2 O How is this compared to the photosynthesis equation?

Glycolysis Glycolysis is the first process of cellular respiration. It occurs in the cytosol. Glucose (C 6 H 12 O 6 ) is partially broken down to produce 2 pyruvate (C 3 H 3 O 3 ) compounds This process yields 2 ATP and 2 NADH for every glucose molecule.

Aerobic Cellular Respiration Oxygen required=aerobic Aerobic respiration follows glycolysis. It occurs in the mitochondria. There are 2 main parts to aerobic respiration: – Kreb’s Cycle – Electron Transport Chain

Kreb’s Cycle Completes the breakdown of glucose – Takes the 2 pyruvate (C 3 H 3 O 3 ) and completely breaks them down. – The carbon and oxygen atoms of pyruvates end up in CO 2 and H 2 O This is where the CO 2 that we exhale is produced! – 3 NADH and 1 FADH 2 and 2 ATP get produced

Electron Transport Chain Here is where most of the energy is produced! Electron flow ultimately produces 32 ATP! The oxygen that we inhale is the electron acceptor at the end of the ETC. This acceptance of electrons is what produces the ATP.

Photosynthesis

Cellular Respiration

Cellular Respiration Practice You and a partner need: – 5 NADH (dark orange) – 4 ATP (red) – 1 FADH 2 (green) – 1 mitochondria (blue)

Anaerobic Cellular Respiration Some organisms (some bacteria) thrive in environments with little or no oxygen No oxygen used= anaerobic Anaerobic organisms experience anaerobic cellular respiration after glycolysis. This produces NO ATP! Depending on the type of cell, the end products of this are alcohol or lactic acid.

Energy Tally Anaerobic organisms can’t be too energetic but are important for global recycling of carbon AerobicAnaerobic Glycolysis Kreb’s Cycle Electron Transport Chain Total ATP per glucose