Energy in Living Organisms: From Sun to ATP

1. Biology 111Ch 6

2. Energy Definitions • Ultimately ALL energy comes from the sun

3. Bioenergetics • The study of how living organisms use energy to perform activities of life

4. Radiant to chemical Chemical to heat Wind to electrical Solar to heat Energy – ability to do work (change or move something) – can be converted from one form to another

5. Energy moves from molecule to molecule through electrons

6. Calorie – amount of energy required to raise the temperature of 1 gram of water 1 degree Celsius

7. Kilocalorie – unit for measuring energy in food and output of organisms – must raise 1000 g of water 1 degree C. 1kilo cal = 1000 calories

8. Photosynthesis – energy requiring stage of energy acquisition

9. Cellular Respiration – energy releasing stage

10. 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)

11. 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?

12. Most species depend on autotrophes for energy

13. A few species get energy from geothermal sources Bacteria at vents provide hydrogen sulfide – called Chemoautotrophes Aerial view of Yellowstone hot springs

14. Energy at rest is potential Energy.Energy in motion is kinetic energy.

15. Potential – STORED in chemical bondsKinetic- chemical bonds BREAK – energy released – moves objects (atoms)

16. 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??

17. 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

18. 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 vice-versa • Energy proceeds in one direction • Spontaneous – processes that occur without an energy input

19. 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.

20. 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

21. Anabolism– constructs large molecules from small – USES energyCatabolism - Large molecules into small – RELEASES energy

22. FORMING bonds takes energy- BREAKING bonds releases energy • Bond energy – amount of energy stored in the electrons of a chemical bond (

23. Free Energy – amount of energy potentially available to form new bonds • Energy of activation – start up energy (kindling temp for fire)

24. 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

25. Reactions halt when equilibrium is met • Chemical equilibrium – when reactions go back and forth at the same rate • Energy not gained or lost

26. 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.

27. ATP- Energy Currency in the Cell • Adenosine Triphosphate- stored useable energy – made in the mitochondria during cellular respiration.

28. 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

29. 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

30. Cofactors – non protein helpers enable some reactions to proceedThey are often trace minerals (Mg2+)

31. Coenzymes – carry protons 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

32. Enzymes: Life’s CatalystsActivation energy may come from environmentEnzymes speed biochemical reactions Enzymes decrease the energy of activation Enzymes sensitive to denaturation

33. 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

34. Positive Feedback