Energy

1. Energy nz.srichinmoycentre.org LECTURE #8

2. Energy is Central to Life • Energy = the capacity for work • All life requires a constant supply Solar energy  chemical energy We “burn” sugar (chemical energy) to get our usable energy. the-plant-directory.co.uk

3. Energy is Central to Life • Sugars possess energy because they contain “high energy electrons” • Electrons perched on the top of an energy hill • When these electrons “roll down the hill,” this energy is released • Released energy can be used jepoyguapo.blogspot.com

4. Energy is Central to Life • Energy released from chemical reactions can be converted into a nucleotide called ATP. Adenosine triphosphate = “The energy transfer molecule”

5. Energy is Central to Life • ATP can store energy that has been released during chemical reactions • ATP can release this energy when it is needed for some activity • e.g., muscle movement, active transport, etc. • $$$$$$$$$$$$$$$$

6. The First Law of Thermodynamics Energy cannot be created or destroyed Energy can only be transformed i.e. convertedfrom one form to another • Coal contains energy in its chemical bonds • A steam engine converts this energy into heat • This heat is converted into mechanical energy • This mechanical energy is used to move a train

7. Note: There is no absolute lossof energy in this process, but energy is transformed from an ordered form (chemical bonds of coal) to a less-ordered, more dispersed form (heat).

8. The Second Law of Thermodynamics Energy transfer always results in a greater amount of disorder (“entropy”) in the universe • Energy transformations run spontaneously in one direction • With each energy transformation, a portion of the energy is converted to heat • Sometimes a very large portion!

9. Efficiency of energy systems, as measured by the proportion of energy they receive relative to what they then make available to perform work. In each system, most of the energy not available for work is lost to heat.

10. Entropy • An increase in entropy is responsible for many of the “normal” things we see every day Salt dissolves in water Bicycles roll downhill Messy bedrooms… It costs energy to counteract the chaos! en.wikibooks.org hyperboleandahalf.blogspot.com popularwealth.com

11. Metabolism • Metabolism = All the chemical reactions within living organisms that produce complex macromolecules AND break down those molecules into smaller molecules and usable energy. • Anabolic reactions = Create complex molecules • Catabolic reactions = Break down molecules  usable energy

12. Energy is Central to Life • Study: Arctic people produce more heat • Mitochondria release more energy as heat  people feel warmer • Heat production is result of inefficient energy harvest • Leaves less energy for other uses

13. Storing energy • Some of the sugars you eat can be stored for later use… • Sugars are combined to form glycogen Building a complex molecule“costs” energy (ATP) zimbio.com

14. Releasing energy • Sugars can later be released from glycogen to get energy

15. The Energy Molecule: ATP • ATP = adenosine triphosphate • Nucleotide triphosphate Remember me?

16. ADP • ADP = adenosine diphosphate • Three parts • Sugar (ribose) • Nitrogen-containing base (adenine) • Phosphate groups (two of them) • Lowerin energy than ATP

17. The Energy Molecule: ATP • ADP and ATP can be interconverted • ADP + P  ATP This requiresenergy • ATP  ADP + P This releases energy

18. The Energy Molecule: ATP • A cell spends ATP like you spend money • $$$ pays your rent, buys lunch, etc. • ATP pays for active transport, etc.

19. Active transport Active transport = movement up concentration gradient; requires a transport protein and energy • ATP  ADP provides this energy • EXAMPLE: Active transport of calcium ions (Ca2+) out of cellduring muscle contraction.

20. Active transport By transferring a phosphate group to the transport protein, ATP causes the protein to change shape in a manner that transports calcium ions across the cell membrane. 

21. The Energy Molecule: ATP • Energy is stored in the form of ATP for only briefperiods of time (1 min) but it is made/used constantly. • Long-term energy storage is accomplished by glycogen and fat • These molecules are broken down and “burned” to generate ATP for immediate use. family.go.com

22. Which organelle in the cell is responsible for energy harvest?

23. Harnessing energy in cells The “burning” of sugar in the mitochondria is highly regulated, unlike the combustion of wood or gas. nsf.gov nz.srichinmoycentre.org

25. Enzymes • Enzymes regulate virtually every chemical process that takes place in living things. • Catalysts = Accelerate reactions that normally occur. • Reactions occur at a higher rate = 10,000 per second • Enzymes are not damaged in process

26. Enzymes: The regulators • Lactose (“milk sugar”) is a disaccharide • Glucose and galactose • Lactose breakdown • Imperceptibly slow in a milk jug • Expedited by lactase in cells (x109)

27. Enzymes • Lactose intolerance is due to the inability to break down lactose • Why are some people are lactose intolerant? • Reduced production of the enzyme lactase after childhood. • Evolution of increased tolerance in adults in northern climates… conversationinfaith.wordpress.com

28. Enzymes • The production of enzymes is encoded by genes • One gene for each protein (polypeptide) • Damaged gene  no enzyme produced

29. Enzymes • Many inherited disorders are caused by the inability to produce a specific enzyme: • Tay-Sachs disease (accumulate galactose-lipids in brain/nerves) • Congenital adrenal hyperplasia (secretion of adrenal hormones) • Lactose intolerance (can’t metabolize lactose)

30. Enzymes • We possess thousands of enzymes • Each enzyme facilitates a specific reaction • Lactase: lactose  glucose + galactose • Sucrase: sucrose  glucose + fructose • RNA polymerase: nucleotides  RNA • _____-ase: substrate  product

31. Metabolism • Metabolism = All the chemical reactions within living organisms that produce complex macromolecules AND break down those molecules into smaller molecules and usable energy. This process is facilitated by enzymes. • Anabolic reactions = Create complex molecules • Catabolic reactions = Break down molecules  usable energy

32. Metabolic pathway • Many activities are multi-step processes • e.g., Blood clotting, leaf growth, digestion, etc.

33. Metabolic pathway • Many activities are multi-step processes • e.g., Blood clotting, leaf growth, digestion, etc. • Each step requires a different enzyme Substrate 1  Substrate 2 substrate 3  product This series of reactions is termed a metabolic pathway Enzyme 1  Enzyme 2  Enzyme 3 

34. Like baking a cake… Substrate 1 (eggs) Substrate 2 (whisked eggs) Substrate 3 (dough) Enzyme 1 (whisk)  Enzyme 2 (flour sifter)  Enzyme 1 changes the chemical properties of the substrate Enzyme 2 brings two substrates together (Substrate 2 and Flour)

35. EXAMPLE: Enzyme A combines two substrates, enzyme B removes part of the substrate, and enzyme C changes the shape of its substrate. Product of each enzyme-facilitated reaction = substrate for the next reaction.

36. How do they do it? • For any chemical reactions to occur, an initial input of energy is required. • “Activation energy” • Enzymes reduce that required energy input.

39. Activation Barriers & Enzymes • Enzymes bind to their substrates • Lock-and-key fit • Substrate binds to an enzyme’s “active site” • Note: Only a few amino acidsinvolved in bond at active site

40. Activation Barriers & Enzymes • Binding to an enzyme makes a substrate molecule more vulnerable to chemical alteration • Example: Bending a molecule to expose bonds decreases the amount of energy it takes to hydrolyze.

41. Activation Barriers & Enzymes Example: The enzyme chymotrypsin(ki–muh-trip-sun) • Digestive enzyme in small intestine • Chymotrypsin binds to ingested protein • Protein shape is distorted • Protein now vulnerable to hydrolysis by water molecules • Protein chain is lysed via hydrolysis • Repeat…

42. In the absence of chymotrypsin, this process would take a billion times longer. 

43. Activation Barriers & Enzymes • Accessory molecules help enzymes • Coenzyme= Non-protein substance that binds with an enzyme to help it function • These coenzymes “sit” at or near the active site and attract or repel substrates. • Can be organic or inorganic constituents • Main function of vitamins!