Topic 8 Test Flashcards
Effects of rate of reaction with enzymes/importance of enzymes
Activation energy is the initial input of energy that is required to trigger a chemical reaction. Enzymes lower the activation energy of the chemical reactions that they catalyze. Enzymes benefit organisms by speeding up the rate at which reactions occur, they make them happen millions of times faster.
How do enzymes lower the activation energy of a reaction?
- The substrate binds to the enzymes’ active site and the active site is altered to reach
the transition state.
- Due to the binding the bonds in the substrate molecule are stressed/become less
stable.
- The binding lowers the overall energy level of the transition state.
- The activation energy of the reaction is therefore reduced.
- n.b. the net amount of energy released by the reaction is unchanged.
Competitive and non-competitive inhibitors
An inhibitor is a molecule that binds to an enzyme and slows down or stops the enzyme’s function. Inhibition can either be competitive or non-competitive.
A competitive inhibitor blocks the active site, preventing the substrate from entering. The higher the concentration of the inhibitor, the slower the rate of reaction. Overcoming alcoholism is an example of competitive inhibition. Antabuse is an example of a competitive inhibitor.
Non-competitive inhibitors bind to an allosteric (other) site on the enzyme. The active site is altered and the substrate cannot attach and react.
The competitive inhibitor binds to the active site and prevents the substrate from binding there. The noncompetitive inhibitor binds to a different site on the enzyme; it doesn’t block substrate binding, but it causes other changes in the enzyme so that it can no longer catalyze the reaction efficiently.
Allosteric sites/active sites
An allosteric site is a region of an enzyme where activator or inhibitor molecules can bind and either activate or decrease enzyme activity.
- only found in allosteric enzymes
- substrate
do not have two separate websites
An active site of an enzyme is the area where the substrate molecules bind and the enzyme catalyzes the reaction, which results in the creation of specific products
- all enzymes contain it
- effector molecules
- binding and catalytic sites are two different sites
Process of end product inhibition
End-product inhibition prevents a large build-up of products
1. Bacteria synthesize isoleucine from threonine in a series of five enzyme-catalyzed steps
2. As the concentration of isoleucine increases, some of it binds to the allosteric site of threonine deaminase
3. Isoleucine acts as a non-competitive inhibitor to threonine deaminase
4. The pathway is then turned off, regulating isoleucine production
5. If the concentration of isoleucine later falls (as a result of its use) then the allosteric sites of threonine deaminase are emptied and the enzymes recommence the conversion of threonine to isoleucine takes place.
Oxidation vs Reduction
When a reactant loses electrons during a reaction, it is called oxidation. When a reactant accumulates electrons during a reaction, it is called reduction.
OXIDATION
- Electrons are lost
- Oxygen is gained
- Hydrogen is lost
REDUCTION
- Electrons are gained
- Oxygen is lost
- Hydrogen is gained
Role of oxygen in cellular respiration
Cellular respiration:
1. It is a metabolic process that takes place in the cells of organisms by which they use oxygen to break down glucose and produce ATP.
2. It provides the chemical energy required for the functioning of cells.
Importance of oxygen in cellular respiration:
1. Oxygen is required in cellular respiration in the electron transporter chain.
2. It serves as the final electron acceptor of the electron transport chain facilitating the movement of electrons down the chain hence producing the ATP or adenosine triphosphate.
3. Oxygen combines with the electrons and the hydrogen ions to form water which is a byproduct of the process.
Breakdown of what is made in each step of CR and the location of where it is all going down
- Glycolysis. In glycolysis, glucose—a six-carbon sugar—undergoes a series of chemical transformations. In the end, it gets converted into two molecules of pyruvate, a three-carbon organic molecule. In these reactions, ATP is made, and NAD+ is converted to NADH.
- Pyruvate oxidation. Each pyruvate from glycolysis goes into the mitochondrial matrix—the innermost compartment of mitochondria. There, it’s converted into a two-carbon molecule bound to Coenzyme A, known as acetyl CoA. Carbon dioxide is released and NADH is generated.
- Citric acid cycle. The acetyl CoA made in the last step combines with a four-carbon molecule and goes through a cycle of reactions, ultimately regenerating the four-carbon starting molecule. ATP, NADH, and FADH2 are produced, and carbon dioxide is released.
- Oxidative phosphorylation. The NADH and FADH2 made in other steps deposit their electrons in the electron transport chain, turning back into their “empty” forms (NAD+ and FAD). As electrons move down the chain, energy is released and used to pump protons out of the matrix, forming a gradient. Protons flow back into the matrix through an enzyme called ATP synthase, making ATP. At the end of the electron transport chain, oxygen accepts electrons and takes up protons to form water.
Significance and movement of H+ ions in chemiosmosis in animals
Chemiosmosis is the diffusion of ions across a semi-permeable membrane, through a carrier protein. In this case, the ions are hydrogen protons and the carrier is ATP Synthase. The flow of H+ through ATP Synthase generates ATP.
Photolysis
Photolysis is the splitting or decomposition of a chemical compound by means of light energy or photons. For example, the photolysis of the water molecule in photosynthesis occurred under the influence of light. When photons are absorbed, it causes the hydrogen to bind to an acceptor, subsequently releasing oxygen.
Conversion of light energy to usable energy in plants
During the process of photosynthesis, light penetrates the cell and passes into the chloroplast. The light energy is intercepted by chlorophyll molecules on the granal stacks. Some of the light energy is converted to chemical energy. During this process, phosphate is added to a molecule to cause the formation of ATP.
Drawing and annotation of mitochondrion and justification of how its shape is efficient to create energy
The folding of the inner membrane increases the surface area inside the organelle. Since many of the chemical reactions happen on the inner membrane, the increased surface area creates more space for reactions to occur. If you have more space to work, you can get more work done.
Significance and movement of H+ ions in chemiosmosis in plants
CHEMIOSMOSIS – the ability of the cell to use the proton-motive force to do work
- Chemiosmosis can refer to ATP synthesis, but can also refer to other energy-consuming activities, such
as the rotation of flagella that prokaryotes use for motion.
- ATP synthesis is carried out by oxidative phosphorylation, which relies on a large multiprotein
complex called ATP synthase
- ATP Synthase
- A large multiprotein complex that spans the IMM
- The proton-motive force moves H+ through the protein down the concentration gradient, and into the matrix (because the cell wants to be balanced)
- ATP Synthase has specialized components that catalyze the formation of one ATP from ADP + Pi
- 3 H+ are required to form 1 ATP molecule
- And that’s how ATP is made!
