Ground Rules of Metabolism CHAPTER 6

Ground Rules of Metabolism CHAPTER 6

Antioxidants You ve heard the term. What s the big deal?

Found naturally in many fruits and vegetables Added to many products What do they actually do? Antioxidants

Free Radicals are highly reactive molecules Example: Oxidants like O 2 - Formed by natural reactions in our bodies to break down fats & amino acids. Very destructive to macromolecules (proteins, lipids, DNA) Major contributor to the aging process and diseases like: Cancer Heart Disease Failing Immune System Antioxidants help us get rid of Free Radicals!

Cells deal with O 2- by using a series of reactions. A series of reactions is a pathway The pathway for the removal O 2- from a cell uses two enzymes: Superoxide Dismutase Catalase Dealing with Free Radicals

Reactant substance that enters a metabolic reaction or pathway; also called an enzyme s substrate. Intermediate Substance formed between reactants and end products of a reaction or pathway. Product Substance left at end of reaction or pathway. Cofactors Coenzyme or metal ion; assists enzymes or taxis electrons, hydrogen, or functional groups between reaction sites. Metal Ions, NAD +, FAD 2+, NADP + Reaction Basics

Energy carrier Mainly ATP in cells; couples energy-releasing reactions with energy-requiring ones. Transport Protein Protein that passively assists substances across a cell membrane or actively pumps them across. AB + CD à AD + CB Reaction Basics

Metabolism: Cell s capacity to acquire energy and to use it to build, degrade, store, & release substances in controlled ways. Metabolic Pathway: Enzyme-mediated series of reactions Catabolism = metabolic pathways that release energy by breaking down compounds Anabolism = metabolic pathways that consume energy to build compounds Metabolism- Pathways

Equilibrium = state of maximum stability Metabolism as a whole is never at equilibrium because of the constant flow of materials in & out of the cell Equilibrium

Kinetic Energy energy of motion Potential Energy stored energy Chemical Energy the potential energy available for release in a chemical reaction Thermal Energy kind of energy that is related to and/or caused by heat Energy Cells utilize chemical & electrochemical energy, and often release thermal energy

First Law of Thermodynamics energy can be transferred & transformed, but it cannot be created or destroyed Second Law of Thermodynamics energy transfer or transformation increases the entropy (disorder or randomness) of the universe Laws of Energy Transformation (Thermodynamics)

Energy Flow through Ecosystem

Free Energy (G) portion of a system s energy than can perform work -when temperature and pressure are uniform throughout the system measure of a system s instability (tendency to change to a more stable state) Chemical reactions that lose free energy (DG < 0) are spontaneous or exergonic absorb free energy (DG > 0) are endergonic

Chemical reactions that lose free energy (DG < 0) are spontaneous or exergonic Ex: Cellular respiration absorb free energy (DG > 0) are endergonic Ex: Photosynthesis

Immediate source of cellular energy Common to ALL living things Responsible for mediating most energycoupling reactions (use of exergonic reaction to drive an endergonic reaction) 10 million consumed & regenerated per second per cell ATP (Adenosine Triphosphate)

The hydrolysis of ATP powers cellular work the bond between the 2 nd & 3 rd phosphate groups breaks the phosphate group is transferred to another molecule (=phosphorylation) Phosphate group is easily lost due to the concentration of negative charges in phosphate tail.

3 Kinds of Cellular Work: Mechanical ex: beating of cilia, muscle contraction, movement of chromosomes during cell division Transport ex: active transport Chemical ex: endergonic reactions Cellular Work

ATP synthesis requires energy ATP hydrolysis yields energy ATP Cycle

Many chemical reactions in the cell are slow (even spontaneous reactions) Cells use enzymes (catalytic proteins) to speed up reactions Enzymes lower the energy required to start a reaction (activation energy E A ) Enzymes

The active site of an enzyme has a specific shape that is specific to the shape of the substrate that binds to it Induced Fit Hypothesis substrate induces a change in the shape of the active site to create a snug fit Enzymes Show Specificity

Enzymes emerge from reactions in their original form Enzymes can catalyze both the forward & reverse reactions How Enzymes Work

1. Active site can help substrates come together in the proper orientation for a reaction to occur 2. Enzyme may stretch substrates toward their transition-state conformation 3. Active site may provide a microenvironment that is more conducive to a particular type of reaction 4. Active site may participate directly in the chemical reaction How Enzymes Lowering E A

As substrate concentration increases, reaction rate will increase to a point When enzyme becomes saturated (all enzymes have their active sites engaged), the rate of the reaction will be determined by the rate at which the active site can convert substrate to product Substrate Concentration

Enzyme reaction rate increases with an increase in temperature to a point Initially, an increase in temperature makes substrates move faster and they are more likely to collide with the active sites of enzymes When temperatures get too high, the enzyme denatures and the reaction stops Most human enzymes have optimal temperatures between 35-40 C Temperature

The optimal ph for most enzymes is between 6-8 When the ph deviates from the optimum, the enzyme denatures and the reaction stops 2 exceptions: pepsin & trypsin ph

Competitive mimics the substrate; binds to & blocks the active site Noncompetitive binds away from the active site; causes the enzyme to change shape which changes the shape of the active site Inhibitors can play a regulatory role Enzyme Inhibitors

Allosteric regulation binding of an activator or inhibitor molecule to a regulator site on an enzyme which stabilizes the functional or inactive form of the enzyme, respectively Ex: ADP acts as an activator & ATP acts as an inhibitor for several catabolic enzymes Cooperativity one substrate binds to an enzyme and primes the enzyme to accept additional substrates Feedback inhibition product of a metabolic pathway binds to & inhibits an enzyme that acts early in the pathway Regulation of Enzyme Activity

Enzyme Videos http://www.youtube.com/watch?v=pilzvt3spcq&feature=related (General Function and Competitive Inhibition) http://www.youtube.com/watch?v=mpcnkbe6fs0 (student made claymation to Pac Man theme - watch smile turn to frown) http://www.youtube.com/watch?v=czd5xsokres&feature=related (student made - quirky but good) http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter2/animation how_enzymes_ work.html (MCGraw Hill shows conformation change leading to product formation) http://www.youtube.com/watch?v=ms_ehuvvkkk&feature=related (Interleukin-1 bindng to surface protein receptor, leads to conformational change - good 3D shapes) http://www.youtube.com/watch?v=urbdpyeagbs&feature=related (shows protein structure and stick figure molecular binding)

Enzyme E.C.!!!!!! By yourself or with a group, create and film an enzyme video, post it on YouTube and send me the link. Amount of E.C will be based on Mr. Newton s SUBJECTIVE opinion on the quality of the video AND the sheer number of YouTube hits!