1. Metabolism Chapter 6

2. 2-Week Agenda Today: Lab #4 part 1, Lab #6, Metabolism Part 1 Thursday: Lab #4 part 2, Metabolism Finish, Begin Photosynthesis Tuesday: Finish Photosynthesis, then do either (a) cell respiration or (b) photosynthesis lab Thursday: TEST 2 –Chapter 6 (Plasma Membrane) –Chapter 9 & 10 (Mitosis & Meiosis) –Chapter 7 (Metabolism / Energy / Enzymes) –Chapter 8 (Photosynthesis) –No cell respiration Test 3 will be on November 20 th as in the syllabus, and will cover material covered in lecture up to this point. YOU WILL BE TESTED ON ALL MATERIAL NOT COVERED IN TEST 3 ON YOUR FINAL EXAM AND QUIZZES.

3. Chapter 6 Energy Entropy Metabolism & Energy ATP Metabolic Pathways & Enzymes

4. Concepts & Vocab “Energy” –Kinetic vs Potential –Chemical energy as a form of potential energy Converted from chemical to other kinds. –Activation Energy –Metabolic Pathway –Reactants, Products –Enyzmes, Substrates “Work”: “useful” energy transfers. “Heat”: Energy transfer that only changes the microscopic vibrations of the recipient (can’t do anything useful with it) “Entropy”

5. “Work”: Energy transfer that changes the physical aspect of the recipient (something “useful”, e.g. a volume changes, an object moves or changes shape, etc.) – the key here is the transfer in energy does NOT result in higher entropy (chaos).

6. Temperature is a measure of the AVERAGE amount of energy each member of a system has. Individual members can have more or less energy than average.

7. Energy goes downhill, but why? Ball Rolls down hill (why? Gravity) Potential energy (mass + gravity) is turned into kinetic energy of motion (work is being done in the form of changing an object’s position).

8. Energy goes downhill, but why? Ball Rolls down hill (why? Gravity) When the ball reaches equilibrium (it rolls to a stop), it has no more potential energy. 10 units of work

9. Energy goes downhill, but why? Why not just put it back to roll again? Because it costs MORE energy to put it back. You have to go against gravity, and put MORE work (in the form of changing the objects position) into changing its position than the amount it gave off! 12 units of work

10. Heat Moo. 2 nd Law: It all goes downhill

11. Laws of Thermodynamics First Law The total amount of energy in the universe is constant. Another way of saying it: Energy can be neither created nor destroyed

12. 2 nd Law Read it here: http://en.wikipedia.org/wiki/Second_law_of_thermodynamics http://en.wikipedia.org/wiki/Second_law_of_thermodynamics “In simple terms, the second law is an expression of the fact that over time, differences in temperature, pressure, and density tend to even out in a physical system that is isolated from the outside world. Entropy is a measure of how far along this evening-out process has progressed.” Phrasing: –“Systems tend to increase their entropy.” –“Heat cannot itself pass from a colder to warmer body” –My phrasing: “everything’s going downhill from here.” Entropy = disorder, chaos. Clean room vs. messy room A house on a 20 year old lot High Entropy = very stable (easy to keep a room messy!) High Order = very unstable (easy to break an egg!)

13. “Free” Energy It’s “Free” to do work. Like you’re “free” on a lunchbreak to each lunch. “Free Energy” is simply the energy that’s available to do something useful. –Glucose has free energy inside it’s bonds. When those bonds are broken, the energy used to hold the atoms together is now put to work to form new chemical bonds.

14. Gibb’s Free Energy Explained The guy who discovered it’s name was “Gibb”. So we don’t just call it Free Energy, it’s his energy. “Gibb’s Free Energy” is “G”. When we talk about free energy, we need to talk about where it’s coming from and where it’s going (e.g. we’re making ATP from sunlight (autotroph) or glucose (heterotroph)). Because we’re interested in both an amount and a ‘direction’, Gibb’s Free energy is a vector quantity (vectors have magnitude and direction, e.g. 5 steps north, -4 degrees, etc.)

15. Gibb’s Free Energy Explained Energy is never “negative” in the same way money is never “negative”. There’s no such thing as a negative dollar bill. We talk about energy being lost or gained; mathematically, we use negative and positive. So “negative” free energy (-G) is when a system losses energy, and positive free energy (+G) is when a system gains energy Everything has some energy already (recall Brownian Motion). That means that when we consider “positive” and “negative” energy, we’re really talking about changing the amount of energy a system has. Therefore, we talk about changes in free energy of a system. In math, “change” is symbolized by a “delta”,  In And thus, we write “change in Gibb’s Free Energy”,  G

16. Chemical Reactions in the Cell All substances are constantly moving inside the cell For a chemical reaction to occur, what has to happen? –1: The molecules have to physically collide. –2: They need to collide at exactly the correct orientation –3: They need to have enough energy to push past the repulsion of their electron clouds

17. Wrong orientation, not enough velocity To overcome the electron cloud repulsion.

18. Right orientation, not enough velocity To overcome the electron cloud repulsion.

19. Right orientation, AND enough velocity to overcome the electron cloud repulsion.

20. A hydrolytic enzyme reaction

21. Heating up the reaction gives the average molecule more velocity

22. If these 2 reactants were floating around a cell, it would take a very long time for them to come together by chance, in exactly the right orientation and with enough velocity… This is where enzymes come into play.

23. So what do enzymes do? They: 1.take care of the orientation 2. Bring them close enough together so they will spontaneously reaction

24. Back to  G The stored up (potential) energy inside a bond between two atoms (chemical energy) is released (becomes moving, kinetic energy that is free to do work). This is a chemical reaction. If the reactants have more energy to start with than the products have after the reaction is finished, is this a positive or negative change in Gibb’s Free Energy? It’s negative. We’ve rolled downhill. The products can’t do as much work as the reactants. These kinds of reactions, which give off energy, are called “exergonic” reactions. They are also “spontaneous”.

25. Can the products still do work? If they have enough energy left in them, sure These products can go on to react and create something with even less energy than they had. The reaction is still spontaneous, we’re still heading downhill. This is the idea behind an electron transport chain… a high energy electron is sent downhill, through a series of organized reactions. The energy given up by the electron is used to perform work (e.g. make a new chemical bond). Remember that some energy is always wasted as heat (2 nd law). There is NEVER 100% efficienciency. Summary: reactions in which energy is going dowhill are described as: –Spontaneous –Have a negative change in Gibbs Free Energy –Are Exergonic

26. So how do we go uphill? ALL life on earth starts at the same “mountaintop” of energy. –This is where photosynthesis comes into play (more on that later). The energy from sunlight is physically captured by an antennae-like structure inside plant cells, and handed off down the chain. Here’s the trick: An exergonic reaction, which GIVES OFF ENERGY, is coupled to a reaction that REQUIRES energy to happen. –This kinds of reactions build things. –They are NOT spontaneous. The “building” reaction uses some amount of the energy given off by the exergonic reaction (SOME) to perform work. –Example: an exergonic reaction within the electron transport chain donates it’s free energy (that’s it is giving off) to an enzyme, which performs the task of building a bond between ADP and inorganic Phosphoate, Pi.

27. ENERGY FROM AN EXERGONIC REACTION ENERGY PROVIDED FOR AN ENDERGONIC REACTION (MUSCLE CONTRACTION) (+HEAT)

28. Next Presentation is “Metabolism II”