Cell bio Exam 3 Chapter 3 energy catalysis biosynthesis 2nd law of thermodynamics Entropy lack or order is always increasing Energy input is needed to created order Life is built on chemical rxns Anabolic and catabolic pathways exist Catabolism Breakdown of larger molecules Anabolism synthesis of larger molecules Respiration breaks down sugars for energy catabolic process Photosynthesis in Plants turns light energy into sugar oxygen anabolic process Respiration and photosynthesis are complimentary processes 2 Kinds of Energy Potential Energy Stored energy ability to do work Kinetic Energy The energy in motion ATP is the main energy carrier in Cells Free Energy Change A living systems free energy is energy that can do work Reactants have more energy than product G 0 Reactants have less energy than products G 0 Exergonic and Endergonic Rxns in metabolism Exergonic Proceeds with a net release of free energy and is spontaneous Endergonic absorbs free energy from its surroundings and is nonspontaneous G 0 What drives Rxns If some rxns are downhill why don t they happen spontaneously Because covalent bonds are stable bonds Downhill exergonic rxns require a push Activation Energy EA o Stable bonds need to ABSORB energy to break Enzymes reduce activation energy is a catalytic protein It is a Catalyst A chemical agent that speeds up or facilitates a rxn without being consumed by the rxn Enzymes physically react with substrates to facilitate the rxn EX Sucrase is an enzyme that catalyzes the hydrolysis of sucrose In cells enzymes can couple a rxn with a G to another that has a G This allows non spontaneous rxns to occur in a way that is overall energetically favorable Activated energy carriers In cells energy release from rxns is stored on special molecules that release energy for other rxns ATP NADH NADPH FADH2 Acetyl CoA are energy carriers ATP is an activated energy carrier The transfer of a phosphate group from ATP is used to drive less energetically favorable rxns How ATP drives chemical work Energy coupling using ATP hydrolysis A high energy intermediate is formed in this coupled rxn Nicotinamide adenine dinucleotide NAD is an important electron carrier molecule in cells NADH NADPH and FADH2 cycle between oxidized and reduced states OIL RIG Oxidation Is Loss of e Reduction Is Gain of e NADH NADPH are very similar Chapter 13 Cellular respiration Cellular respiration Turning food into energy ATP Aerobic respiration Uses oxygen Most eukaryotes do this high yield of ATP Sugar respiration is one of the several interconnected metabolic pathways Outside of a living cell you can heat up a food surce and release all of its energy at once Inside living cells Glucose is broken down in small steps Energy is stored on activated carrier molecules like ATP Cellular respiration The Need for ATP A typical cell contains 109 molecules of ATP All of this is consumed and replaced every 1 2 mins How do cells make ATP Stage I Break food into basic building blocks Digestion It occurs in stomach and intestines in animals In plants it occurs in food vacuoles Stage II Glycolysis Occurs in the cytoplasm Glucose 6C is broken into 2 pyruvates G P P Each pyruvate is shuttles into the mitochondria Sage III Acetyl CoA is broken down into H2O CO2 and large amounts of ATP Occurs within the mitochondria Net gain is 30 32 ATP Cellular Respiration Key Features Overall rxn is catabolic energy is released Every carbon from glucose reactant is given off as CO2 product and gas Some energy from these exergonic rxns are used to make ATP immediately but most of the energy is transferred to the activated carriers NADH and FADH2 At the very end of the process the energy stored in NADH and FADH2 are used to make a lot of ATP The mitochondria is essential to the process Stage 3 part A of Cellular Respiration is The Citric Acid Cycle Chapter 13 The citric acid cycle also called the Krebs cycle completes the breakdown of the remaining components of glucose to CO2 The cycle releases the remaining 2 carbons brought in by Acetyl CoA into CO2 generating 1 ATP GTP 3 NADH and 1 FADH2 per turn Overview of The Citric Acid Cycle Also known as the TCA cycle or the Krebs Cycle Occurs within the mitochondrial matrix Breaks down each acetyl CoA into CO2 Acetyl CoA is handed off to a 4 carbon molecule oxaloacetate which is recycled at the end of the process Plants make ATP here Animals make GTP Citric Acid Cycle Yields From 1 Acetyl CoA made from 1 pyruvate o 3 NADH o 1 FADH2 o 1 GTP o 2 CO2 o 6 NADH o 2 FADH2 o 2 GTP o 4 CO2 But we have 2 Acetyl CoA from the original glucose so total yield is Glucose CO2 Energy Yield Totals From Glycolysis Citric Acid Cycle Did You See Oxygen as a Reactant in the Citric Acid Cycle Notice that amino acids and fatty acids can also participate in respiration Acetyl CoA is made in the mitochondrial matrix from sugars pyruvate and fats Fat Droplets Contain Triacylglycerol Fatty Acids from Triacylglycerol Can Be Used to Make Fatty Acyl CoA This occurs in the mitochondrial matrix Yield from 1 Fatty Acyl CoA o 1 acetyl CoA enters Citric acid cycle o 1 NADH o 1 FADH2 Glycolysis Citric Acid Cycle Produce Important Precursor Molecules Glucose storage in plants and animals Animal Glycogen for energy Plant Starch energy less branched than glycogen cellulose structural support Insect chitin structural support In Plants Lipids and Starch are Stored Within Chloroplasts In animals glycogen is stored in the liver and other tissues Glycogen is Broken Down to Release Glucose for Glycolysis Glycogen Holds a Lot of Water Glycogen reserves are minimal because they occupy a lot of space An average human stores enough glycogen for about 1 day of activity Fat Storage is More Efficient Fat storage takes up less space than glycogen More energy is released per gram of Fat than for Glycogen Chapter 14 Stage 3 part B of Cellular Respiration is Oxidative Phosphorylation This is the big energy producing step of the entire process Oxidative Phosphorylation Process Will Convert Energy from NADH and FADH2 into ATP Electrons are Harvested During Cellular Respiration Onto NADH and FADH2 Electron Transport ATP Synthesis Involves transmembrane protein complexes on Cristae of the Mitochondria Structure Function Mitochondria Oxidative phosphorylation Overview NADH and FADH2 pass high energy electrons to the electron transport chain O2 pulls electrons down the chain in an energy yielding tumble The 2e are passed down the electron transport chain to one