Photosynthesis and Cellular Respiration
Outline I. Energy and Carbon Cycle II. Photosynthesis A. Introduction B. Reactions II. Cellular Respiration A. Introduction B. Reactions
Carbon Cycle All organisms require energy to maintain life The primary form of cellular energy is in ATP adenosine triphosphate adenosine diphosphate -- carrier
Carbon Cycle ATP is generated in a process called cellular respiration Cellular respiration requires glucose molecules (a carbohydrate commonly called sugar)
Carbon Cycle Glucose is an organic compound, which means it contains carbon Glucose must be made by organisms Organisms that make glucose are called autotrophs (auto = self; troph = nourishment) Autotroph means self-feeding, or an organism that can make its own food Autotrophs are called producers because they produce their own food
Carbon Cycle Producers create glucose in a process called photosynthesis Producers include plants, algae, and some bacteria and protists Once glucose is created, it can be used to make the ATP that supplies energy
Carbon Cycle Plants get the carbon they need to make glucose (C 6 H 12 O 6 ) from carbon dioxide (CO 2 ) This carbon is cycled through photosynthesis and cellular respiration through a perpetual process that reuses the carbon to create new energy Thus, it is called the Carbon Cycle and is also known as the Energy Cycle
Carbon Cycle
Human Influence Human civilization has a very significant influence on the carbon cycle. Burning of fossil fuels (oil, coal, natural gas) releases CO 2 into the atmosphere. CO 2 is a greenhouse gas and traps heat in the atmosphere. This has a warming effect on the earth.
Human Influence Human activity began releasing CO 2 into the atmosphere in unprecedented amounts starting with the Industrial Revolution In the last 150 years, the amount of CO 2 in the atmosphere has increased by more than 30%. This is causing global warming. 2014 set a new record high for global temperatures only to be shattered by the new record set in 2015 which looks like it will again be beat once the information from 2016 is fully analyzed.
Human Influence Impacts of human caused global warming: Temperatures rise glaciers melt oceans warm more glaciers melt temperatures rise further Sea levels rise New Orleans, Miami, Boston, L.A., and New York City are among the U.S. cities predicted to be underwater in the coming decades Ocean currents disrupted Superstorms, hurricanes and blizzards, become more common and more severe
Photosynthesis Method of converting sun energy into chemical energy usable by cells Autotrophs: self feeders, organisms capable of making their own food Photoautotrophs: use sun energy e.g. plants photosynthesis-makes organic compounds (glucose) from light Chemoautotrophs: use chemical energy e.g. bacteria that use sulfide or methane chemosynthesis-makes organic compounds from chemical energy contained in sulfide or methane
Photosynthesis Photosynthesis takes place in specialized structures inside plant cells called chloroplasts Light absorbing pigment molecules e.g. chlorophyll
Why Plants are Green Light is composed of photons Photon energy is measured in wavelengths Different wavelengths generate different colors of light
What is Seen All wavelengths (colors) together appear as white light The white light can be separated into the visible spectrum the rainbow. ROYGBIV Other wavelengths are not visible to humans Infrared (IR) and Ultraviolet (UV)
Why Plants are Green What is seen is what is reflected back All other detectable colors are absorbed Chloroplasts contain pigments The dominant pigment is chlorophyll, which absorbs red and blue while reflecting green and yellow The absorbed wavelengths provide the energy needed to power photosynthesis
Photosynthesis Most easily understood in two parts: 1. Light dependent reactions make the energy needed to connect carbons 2. Light independent reactions use the energy to connect the carbons
Chloroplast Structure
Overall Reaction 6CO 2 + 12 H 2 O + light energy C 6 H 12 O 6 + 6O 2 + 6H 2 O Water appears on both sides because 12 H 2 O molecules are required and 6 new H 2 O molecules are made Important carrier molecules are used ADP ATP NADP NADPH
Light Dependent Reactions Three important components 1. Harnesses sunlight 2. Splits water 3. Creates energy molecules Composed of two separate processes 1. Photosystems creates NADPH 2. Chemiosmosis creates ATP Both of these occur in the thylakoid membrane Both use peripheral and integral proteins
Splitting Water Water is split into H +, e -, and O 2 H + and e - are used elsewhere O 2 is a waste product
Photosystems Light energy is absorbed by chlorophyll molecules Energy boosts e - to high energy states As the e - fall back down to low energy states, NADPH is created *The H + and e - come from the split water
Chemiosmosis Photosystems also create H + concentration gradient H + diffuses back through ATP synthase to create ATP
Light-dependent Reactions Overview
Calvin Cycle (light independent or dark reactions) ATP and NADPH generated in light reactions used to fuel the reactions which take CO 2 and break it apart, then reassemble the carbons into glucose. Called carbon fixation: taking carbon from an inorganic molecule (atmospheric CO 2 ) and making an organic molecule out of it (glucose) Simplified version of how carbon and energy enter the food chain
Calvin Cycle Takes place in stroma Single C m-cules cycled through to create C 3 m-cules C 3 m-cules made into glucose later
Harvesting Chemical Energy Energy enters the food web via autotrophs when they convert light energy into chemical energy. All organisms use this chemical energy (glucose) to create energy molecules (ATP) that fuel their metabolism. Heterotrophs unlike autotrophs they don t create the fuel they use; they must consume it.
Cellular Respiration Overview Transformation of chemical energy in food (glucose and other macromolecules) into chemical energy cells can use: ATP These reactions proceed the same way in plants and animals CELLULAR RESPIRATION Overall Reaction: C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O
Hint Reverse Photosynthesis Cellular Respiration is like photosynthesis in reverse sort of. The products become reactants and the reactants the products Just switch light energy for ATP And don t get any dumb tattoos it s not that hard to remember.
Cellular Respiration Overview Breakdown of glucose begins in the cytoplasm -- the liquid matrix inside the cell There are two pathways: Anaerobic cellular respiration (aka fermentation) Aerobic cellular respiration OR
C.R. Reactions Glycolysis Series of reactions which break the 6-carbon glucose molecule down into two 3-carbon molecules called pyruvate Process is an ancient one-all organisms from simple bacteria to humans perform it the same way Yields 2 ATP molecules for every one glucose molecule broken down (net) Yields 2 NADH per glucose molecule
Glycolosis C 6 H 12 O 6 2 ATP 2 ADP 2 NAD 2 NADH 4 ADP 4 ATP 2 pyruvate (3C) NET GAIN: 2 ATP 2 NADH
an = without aerobic = oxygen anaerobic = without oxygen Anaerobic Cellular Respiration Some organisms thrive in environments with little or no oxygen Marshes, bogs, gut of animals, sewage treatment ponds Results in no more ATP: final steps in these pathways serve ONLY to regenerate NAD+ so it can be recycled to be used in gycolosis again. Ferment yeast, make ethanol, get beer. Work your muscles, make lactic acid, get sore.
Aerobic Cellular Respiration Oxygen present 3 more steps, which occur in the mitochondria 1. Link Reaction 2. Kreb s Cycle 3. Oxidative Phosphorylation
Mitochondrial Strucure
Link Reaction Preps the 3C pyruvate for the Kreb s cycle and brings it into the mitochondria Happens in matrix Coenzyme A used, CO 2 given off NADH produced
Kreb s Cycle Overview Completes the breakdown of glucose Takes the Acetyl CoA (2-carbons) and breaks it down, the carbon and oxygen atoms end up in CO 2 Hydrogens and electrons are stripped and loaded onto NAD + and FAD to produce NADH and FADH 2 Occurs in the mitochondrial matrix Production of only 1 more ATP (per Acetyl CoA) but loads up the carriers NAD+ and FAD to produce large quantities of ATP in the final stage.
Kreb s Cycle YIELD*: 1 ATP 3 NADH 2 FADH 2 *REMEMBER: 2x Acetyl CoA (2C) 1 FAD CO 2 1 FADH 2 1 ADP 1 ATP Kreb s Cycle 3 NAD 3 NADH
Oxidative Phosphorylation The temporary carriers (NADH and FADH 2 ) enter the ETC (electron transport chain) in the cristae. Their high energy e - are used to pump protons (H + ) across the cristae membrane to create a concentration gradient. The H + then diffuse back through ATP synthase to create ATP. (chemiosmosis again!) In the process, the extra electrons and protons are joined to oxygen to create water.
Electron Transport Chain 1 NADH creates 3 ATP 1 FADH 2 creates 2 ATP
BIG PICTURE
Energy Yield Anaerobic Yields only 2 ATP (net) organisms that use this can t be too energetic important microorganisms for carbon recycling fermentation lactic acid
Energy Yield --Aerobic Respiration Gycolosis 4 ATP -2 ETC 2 ATP 2 NADH x3 6 ATP Acetyl CoA 1 NADH x2 x3 6 ATP Kreb s Cycle 1 ATP x2 2 ATP 1 FADH 2 x2 x2 4 ATP 3 NADH x2 x3 18 ATP 1 C 6 H 12 O 6
Energy Cycle photosynthesis 6CO 2 + 6H 2 O + light C 6 H 12 O 6 + 6O 2 cellular respiration C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O + ATP