Chapter 6 – Energy flow in the life of a cell

1. Chapter 6 – Energy flow in the life of a cell • What is energy? • What principles govern energy? • How is energy utilized in biochemical reactions? • How is energy carried in cells? • How do cells control chemical reactions?

2. What is energy? • Potential energy—stored energy • 2. Kinetic energy—energy of movement

3. What is energy?

4. What principles govern energy? • First law of thermodynamics • Total energy remains constant in a closed system • b. Energy cannot be created or destroyed

5. Second law of thermodynamics • In an isolated system, any change causes the quantity of concentrated, useful energy to decrease • Energy is converted from more useful to less useful forms • Organization of matter and energy • 1) Concentrated energy is more ordered (complex) chemically • 2) Entropy—all processes in an isolated system result in an increase in randomness and disorder

6. How is energy utilized in biochemical reactions? • A. Uses of energy in living things • 1. Movement, metabolism, response to stimuli • B. Energy flow in ecosystems

7. How is energy utilized in biochemical reactions? • A. Energy is stored in the chemical bonds of biological molecules

8. How is stored chemical bond energy released so work can be accomplished?

9. How is energy utilized in biochemical reactions? • Energy releasing chemical reactions are exergonic • High energy reactants → Low energy products

10. How is energy utilized in biochemical reactions? • Endergonic reactions • Low energy reactants → high energy products

11. Chemical reactions and activation energy • Why does a match not spontaneously burn?

12. How is energy utilized in biochemical reactions?

13. Endergonic chemical reactions • Do endergonic reactions create energy? • How can the product(s) of an endergonic reaction have more energy than the reactants?

14. How is energy utilized in biochemical reactions? • Exergonic reaction provides energy to drive endergonic reactions

15. How is energy utilized in biochemical reactions? • How is the energy that is released from an exergonic reaction harnessed and directed to drive its associated endergonic reaction? • Energy carrier molecules • a. ATP and electron carrier molecules

19. How is energy utilized in biochemical reactions?

21. In exergonic chemical reactions, • reactants have more energy than products. • energy is destroyed by the reaction. • reactants have less energy than products. • reactant and product molecules possess equal amounts of energy. • Both 1 and 2 are correct.

22. Why is photosynthesis considered an endergonic reaction in an isolated plant? • The sun provides the activation energy necessary to drive the reactions of photosynthesis. • Energy is created during photosynthesis. • Sugar has less energy than the sun. • Energy is released during photosynthesis. • Low-energy reactants are converted into high-energy products.

23. Body fat is composed of lipids created by dehydration synthesis reactions to store energy. Which of the following statements concerning the energy in this system is true? • Creating body fat violates the 1st law of thermodynamics since energy is being created • Creating body fat violates the 2nd law of thermodynamics as complex lipids are more ordered than the fatty acids they are made from • Creating body fat violates both the 1st and 2nd laws of thermodynamics • The laws of thermodynamics do not apply to body fat, because these laws deal with energy, not body fat • None of these statements are true

24. How do cells control chemical reactions? • A. Activation energy requirements for all the chemical reactions occurring in an organism are too high • B. Catalysts reduce activation energy requirements

25. How do cells control chemical reactions? • Enzymes catalyze reactions in living organisms • Bring reactant molecules close together • 2. Make bonds easier to break

26. How do cells control chemical reactions? • Enzymes are synthesized by cells • Most enzymes are proteins

28. How do cells control chemical reactions? • Enzymes are very specific • a. Specificity is based on shape of enzyme and substrate

29. How do cells control chemical reactions? • 4. Most enzymes function as parts of complex, regulated biochemical pathways

30. Enzyme activity is regulated How do cells control chemical reactions?

32. Lipitor Lipitor and cholesterol

33. Enzyme activation

34. Rate of catalyzed chemical reactions • Environmental factors influence the “rate” of enzyme activity • pH, temperature

35. Rate of catalyzed chemical reactions • Environmental factors influence the “rate” of enzyme activity • Concentration of enzymes, substrates, activation factors, inhibition factors

36. Most enzymes are proteins • Mutation and loss of enzyme function Why do mutated enzymes result in biochemical disorders? -Lysosomal diseases

37. Which of these statements regarding enzymes is FALSE? • Enzymes are proteins that function as biological catalysts. • Enzymes display specificity for certain molecules to which they attach. • Enzymes provide energy for the reactions they catalyze. • The activity of enzymes can be regulated by factors in their environment. • An enzyme may be used many times over for a specific reaction.

38. The hydrolysis of sucrose to glucose and fructose occurs spontaneously in human cells. However, if you dissolve sucrose in water and keep the solution overnight at room temperature, there is no detectable conversion to glucose and fructose. Why? • The energy of the reactant is higher than the energy of the products. • The energy of the products is higher than the energy of the reactant. • The activation energy of the reaction increases. • The reaction is endergonic. • The reaction requires a catalyst.

39. HSP Cellular methionine (an amino acid) concentrations are regulated by feedback inhibition. Which enzyme is most likely the target of feedback inhibition in methionine synthesis? • 1) AK • 2) DS • 3) HSDH • 4) HSP • 5) CS