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Biology 111 Ch 6 Energy Definitions • Ultimately ALL energy comes from the sun Bioenergetics • The study of how living organisms use energy to perform activities of life Energy – ability to do work (change or move something) – can be converted from one form to another – Radiant to chemical • Wind to electrical – Chemical to heat • Solar to heat Energy moves from molecule to molecule through electrons Calorie – amount of energy required to raise the temperature of 1 gram of water 1 degree Celsius Kilocalorie – unit for measuring energy in food and output of organisms – must raise 1000 g of water 1 degree C. 1kilo cal = 1000 calories Photosynthesis – energy requiring stage of energy acquisition Cellular Respiration – energy releasing stage Organisms receive energy from the sun, the earth and other living things • Direct from sun, indirect from other organisms • Photons – packets of light energy – Absorbed by electrons (temporarily) Sun’s annual output- 3.8 sextillion megawatts of electricity • Earth gets 2 billionths of this – Most doesn’t reach living organisms – 1/3 reflected back into space – ½ absorbed by planet (converted to heat and returned to space – 19% used to power wind and weather and drives photosynthesis • Of this, .05% - 1.5% is incorporated into plant material – 1/10th of this makes it way into bodies of animals that eat plants - How many Mw is this? Most species depend on autotrophes for energy A few species get energy from geothermal sources Bacteria at vents provide hydrogen sulfide – called Chemoautotrophes Aerial view of Yellowstone hot springs Energy at rest is potential Energy. Energy in motion is kinetic energy. Potential – STORED in chemical bonds Kinetic- chemical bonds BREAK – energy released – moves objects (atoms) Laws of Thermodynamics – regulate energy conversion for life and non-life • Open system- exchanges energy with surroundings • Closed system – no exchange outside the system Opened or Closed?? 1st Law: Energy is neither created nor destroyed, but changes form • Energy in Universe is constant • Living systems continually change • Amount of energy an organisms used cannot exceed the amount of energy it takes in through chemical bonds in nutrients All energy transformations increase entropy • Entropy – tendency toward randomness – Energy transformations are inefficient – reactions result in increased entropy and loss of energy as heat – All energy can convert to heat, but not viceversa – Energy proceeds in one direction – Spontaneous – processes that occur without an energy input Cell energetics from 2nd Law: Inefficient reactions lead to metabolism and produce heat • Most cells extract about half of the energy in nutrients • Organisms remain organized because they are NOT a closed system – Coupled reactions – one reaction occurs at the expense of another • Organisms can increase in complexity as long as something else decreases in complexity by greater amounts • The sun always decreases in energy. Metabolism – chemical reactions that change or transform energy in cells Fatty Acid Metabolism Metabolic pathways – step by step sequences of metabolism – ex: photosynthesis and cellular respiration Anabolism– constructs large molecules from small – USES energy Catabolism - Large molecules into small – RELEASES energy FORMING bonds takes energyBREAKING bonds releases energy • Bond energy – amount of energy stored in the electrons of a chemical bond ( • Free Energy – amount of energy potentially available to form new bonds • Energy of activation – start up energy (kindling temp for fire) Endergonic and Exergonic • Endergonic- products contain more energy than the reactants – Ex: glucose + fructose = sucrose (Anabolism is endergonic • Exergonic reaction- products contain less energy than the reactants – Ex Glucose Carbon dioxide + water (catabolism is exergonic) – Hyperlink on picture Reactions halt when equilibrium is met • Chemical equilibrium – when reactions go back and forth at the same rate – Energy not gained or lost In living systems, electrons move through oxidation/reduction (Redox) chains • Oxidation – loss of electrons from a molecule – Usually oxygen takes a molecules electrons – Ex. Oxidation of glucose • Reduction – gain of electrons ( therefore energy) – Usually are anabolic and require energy • Redox – linked reactions – ex. Electron transport chains – the more reduced they are the more energy they contain. ATP- Energy Currency in the Cell • Adenosine Triphosphate- stored useable energy – made in the mitochondria during cellular respiration. Loss of phosphate group = energy release. Provides almost twice as much energy as necessary to energize mot biological reactions (extra energy is given as heat Cells couple ATP formation and breakdown to other reactions • Cells use ATP 2 ways – To energize a molecule – To change the shape of a molecule – Both transfer phosphate to another molecule – process called phosphorylation • Phosphate is released after reaction occurs • 7 kilocalories are released in splitting 1 mole (1023 molecules) of ATP Cofactors – non protein helpers enable some reactions to proceed They are often trace minerals (Mg2+) cofactor enzyme or protein Zn++ carbonic anhydrase Zn++ alcohol dehydrogenase Fe+++ or Fe++ cytochromes, hemoglobin Fe+++ or Fe++ ferredoxin Cu++ or Cu+ cytochrome oxidase K+ and Mg++ pyruvate phosphokinase Coenzymes – carry protons Vitamin or electrons (NAD+) •May be a nucleotide like ATP •Depends on it’s ability to donate or receive an electron (not phosphorylation) •Vitamins are source •Examples: NAD+ and others niacin riboflavin Coenzyme Function nicotinamid e adenine dinucleot ide (NAD+) oxidation or hydrogen transfer flavin adenine dinucleot ide (FAD) oxidation or hydrogen transfer pantothenic acid coenzyme A (CoA) Acetyl group carrier vitamin B-12 coenzyme B-12 Methyl group transfer thiamin (B1) thiaminpyro phosphat e (TPP) Aldehyde group transfer Enzymes: Life’s Catalysts Activation energy may come from environment Enzymes speed biochemical reactions Enzymes decrease the energy of activation Enzymes sensitive to denaturation Cells control metabolic pathways • Negative feedback- when too much product is made, cells need to turn process off. Final product binds to an enzyme – turns process off (aka feedback inhibition) • Competitive inhibition – product binds to enzyme active site (competition for site) • Noncompetititive inhibition – product binds to a a site other than active site – changes shape of enzyme Positive Feedback