Bio 10: Intro to Biology Instructor: Paul Nagami Laney College Sept. 18, 2013 Harvesting Chemical Energy from Sugar, Part 1

Agenda Administrative Stuff A Quick Review: Energy, Entropy, Calories, ATP Getting Waste out of the Cell, and Nutrients in Glycolysis Breaking Down Sugar Enzymes and Activation Energy NAD + and NADH Fermentation (and muscle burn) Wrap-up

Entropy (or, Not All Energy Is Equally Useful)

ATP: A Cellular “Battery” ADP can then be recycled into ATP by putting the phosphate back on, starting the cycle over. Can this cycle simply be repeated over and over to generate energy? Explain on your index card.

Getting Waste out and Nutrients in Exocytosis Exo = outside/out of Cyto = cell Endocytosis Endo = inside/into Cyto = cell

Two Challenge Statements: 1) “Cells need mitochondria to make ATP.” 2) “Plants have chloroplasts to perform photosynthesis, unlike animals, which have mitochondria to perform respiration.” On your card: Do you agree or disagree with each of these? Why? Talk it over with a neighbor.

Not Everything Has Mitochondria! Prokaryotes don’t have any organelles at all. Mitochondria need free oxygen, and the earth didn’t always have oxygen!

Breaking Down Sugar: First Steps Even organisms without mitochondria can break down sugar! The process of breaking down sugar is called glycolysis. This happens before the rest of respiration Glycolysis does not require oxygen. Eukaryotes perform glycolysis and respiration. Bacteria perform glycolysis.

Understanding Glycolysis But what’s actually going on here? What do these arrows and circles really mean?

What Do Those Arrows Mean? Arrows in the glycolysis diagram represent chemical reactions that are made possible by enzymes. (Proteins) What goes in = reactant/substrate What comes out = product Enzymes lower the activation energy needed for the reaction to happen!

The Induced Fit Model On your index card: Name another enzyme and its substrate(s).

Glycolysis Needs Many Enzymes! Hexokinase Enzymes make metabolism possible.

Reactions in Context Hexokinase Breaking down sugar requires an initial investment of energy! ATP is broken down to stick phosphate on the sugar. Energy released as heat. Not all reactions release energy; some take it in!

Understanding Glycolysis

Make a Guess How many enzymes are needed to break glucose into two molecules of pyruvic acid in glycolysis? The book lists 3 major steps, but how many chemical reactions are needed?

Do NOT Memorize

Understanding Glycolysis What went in? What came out? On your index cards in two columns, write a list of the inputs and outputs of glycolysis, based on this diagram. Check with your neighbor.

Glycolysis: Inputs and Outputs Input (molecules) Output (molecules) 1 Glucose2 Pyruvic Acid 2 ATP2 ADP 4 ADP4 ATP 2 NAD + 2 NADH 4 P2 P ?????

NAD + : An Electron Carrier NAD + is a molecule that can be used to carry electrons and store chemical energy. Not as generally useful as ATP, though. Two electrons are transferred together with an H + to turn NAD + into NADH. FYI: The “A” in NADH is adenine, the “A” DNA base (in GTAC) and the A in ATP! Evolution re-uses chemicals a lot!

What Do We Do with All those High- Energy Electrons? When oxygen is available, organisms with mitochondria can use them in respiration. But what about bacteria? And what about our own muscles when we’re low on oxygen? To get rid of extra NADH and pyruvic acid without using oxygen, organisms perform fermentation.

Lactic Acid Fermentation: A Source of “Muscle Burn” Fermentation turns pyruvic acid into lactic acid and recycles NADH.

Other Uses of Fermentation What other organisms perform fermentation?

Review!