Transcript
v Enzyme Discussion (cont.):
? Most enzymes are globular proteins (glob like structure). Proteins are made of amino acids. They have high specificity. They only interact with one substrate each.
§ A transmembrane protein that works as a pump.
§ The goal of an enzyme is to speed up reactions by stressing bonds/causing bonds of the substrate to break and then reforming the peroxisome. If you get all the right place hit, the enzyme changes shape and basically "eats" the substrate.
? Induced fit- when the enzyme and a substrate interact, a shape change of the enzyme induced by interaction between an active site and a substrate.
§ Active site- interact with some specific molecule called a substrate. The place where the enzyme physically makes contact with the substrate.
? What makes the substrate able to interact with the active site are the specific amino acids that make up the active site because those amino acids will have particular R groups that can interact with specific atoms on the substrate.
® Atoms of the substrate interact with the R groups of the amino acid that make up the active site.
? Substrate- the thing that connects to the active site of an enzyme.
? Enzyme Cycle (Catalytic Cycle) of an Enzyme (MAY BE A SHORT ANSWER QUESTION!)
§ 1.) The substrate interacts with enzyme active site and we get induced fit.
§ 2.) The substrate is held by weak interactions such as hydrogen/ionic bonds and then the energy of activation is going to be lowered because of the activity of the active site. Active site lowers energy of activation by one or a combination of:
? Substrate orientation- when you have more than one substrate.
? Stressing the substrate bonds.
? Stabilizing the transition state.
? Creating a favorable microenvironment.
? Participating directly in the reaction.
§ 3.) Substrate converted to products.
? The active site no longer has an affinity for these products so the products are released and the enzyme is then available again to catalyze the same chemical reaction.
® Catalysts are not consumed in a reaction.
§ Things that impact the speed/function of an enzyme (affect the way a protein folds):
? pH.
? Temperature.
? Substrate and enzyme concentrations.
? Salinity- changes in the ionic strength of the solution.
? Cofactors- nonprotein helpers of an enzyme.
® Example: magnesium ions are really important for enzymes that copy your DNA or carry out transcription (making RNA from DNA).
® If you mess with the concentrations, you can mess with the enzyme function.
? Coenzymes- organic helpers/cofactors, have a carbon base to them.
® Example: vitamins.
? Inhibitors- two types, inactivate function.
® Reversible inhibitor- weak associations, they can attach to the enzyme and can be removed from the enzyme without having to destroy it, two types.
? Competitive- competes for the active site directly.
? Noncompetitive- may bind somewhere else (anywhere other than the active site) which causes the protein to change shape and it won't be able to interact with its substrate. Allosteric effector (causes a shape change).
® Irreversible inhibitor- covalent attachment of something to an enzyme that renders it nonfunctional.
? Once it is attached, it is not coming off and the whole protein would have to be destroyed.
v Cellular Respiration and Photosynthesis
? Cellular Respiration- has three pathways/parts, one big redox reaction.
§ Glucose oxidized to CO2.
§ 6O2 reduced to water (H2O).
§ Glycolysis
? Oxidation/reduction reactions (redox reactions)
® Oxidation- losing electrons, loses hydrogens.
? Oxidizing agent- what caused something to be oxidized.
® Reduction- gaining electrons, gains hydrogens.
? Reducing agent- what caused something to be reduced.
® Something can take an electron from something else because of differences in electronegativity.
? When an electron is moved from something electronegative to something more electronegative, it becomes more stable and it gives up energy in the process.
® NAD/FAD- high energy electron shuttles (they transfer high energy electrons from one location in the cell to another to be used to make ATP).
? Oxidized forms: NAD+, FAD.
? Reduced forms: NADH, FADH2.
? Glycolysis occurs in the cytosol and is anaerobic (occurs without oxygen). Its goal is to take glucose and convert it to two pyruvates plus a little bit of energy. Has ten steps.
® Two parts of glycolysis:
? Energy investment phase- we are going to use 2 ATP in the first half of this.
} Starts with glucose (6-C sugar).
} Step 1: Glucose is going to be converted to something called glucose-6-phosphate.
– The sixth carbon of glucose has a phosphate covalently attached to it from the ATP.
– We used an ATP and it became an ADP.
– Enzyme that does this: hexokinase (a 6-C enzyme that catalyzes a phosphorylation).
w Kinase- an enzyme that transfers phosphates groups in something called phosphorylation.
} Step 2: We are going to convert glucose-6-phosphate into fructose-6-phosphate.
– Glucose and fructose are structural isomers.
– Enzyme that does this: phosphoglucoisomerase.
w Isomerase- something that converts something from one to another isomer.
} Step 3: Fructose-1, 6 bisphosphate.
– Fructose now has a phosphate on the first carbon and the sixth carbon.
– An ATP is used. We have now used 2 ATPs.
– Enzyme that does this: phosphofructokinase.
} Step 4: Glyceraldehyde-3-phosphate (3-C molecule).
– We have two of these.
– Phosphate is on the third carbon.
– 3 carbons long.
– Fructose-1, 6 bisphosphate essentially got cut in half.
– Enzyme that does this: aldolase.
? Energy payoff phase- makes 4 ATP.
} Net: 2 ATP.
§ Krebs Cycle/Citric Acid Cycle/TCA (Tricarboxylic acid) Cycle
§ Oxidative phosphorylation (includes the electron transport chain and chemiosmosis)
Photosynthesis
