Understand enzyme structure and purpose - AP Biology

GLUT1 is a protein that allows glucose to pass into a cell through the membrane. Glucose is a large polar molecule, meaning that it will require a protein in order to diffuse across the membrane. GLUT1 must span the entire length of the plasma membrane in order to provide a "passage" for glucose to diffuse. As a result, GLUT1 is classified as an integral protein, or a protein that fully transverses the membrane.

Peripheral, or extrinsic proteins, are situated on the surfaces of membranes, and do not span across the bilayer. Enzymes catalyze biological reactions; GLUT1 is a transport protein, and does not catalyze any reactions.

Enzymes are biological catalysts that increase the rate of a chemical reaction. This is accomplished by lowering the activation energy for the reaction. Enzymes increase the rate of a reaction, but do NOT increase the amount of products formed in the reaction. They simply cause the products to be formed faster.

A catalyst speeds up the rate of a reaction by lowering the activation energy, which is caused by the high energy transition state. Enzymes are a class of catalyst specific to biological processes, accelerating these processes by lowering activation energy and transition state energy. Catalysts and enzymes may help reactions move faster, but they do not affect the final equilibrium amounts of reactants and products.

While some proteins (such as histones) can pass down information from generation to generation, typically DNA is the macromolecule associated with encoding information.

Proteins commonly catalyze reactions. When these reactions occur in a biological organism, the proteins are considered enzymes. Proteins can also be embedded in cellular membranes, acting as channels or receptors to allow molecular transport. One protein, tubulin, is used to build cilia and flagella (as well as microtubules) that are essential to cell motility.

Proteins are organic molecules made of amino acids that are capable of interfacing with certain substrates and facilitating cellular activities. Enzymes are a sub-group of proteins that are used to speed up reactions within the body. Enzymatic proteins are essential to many biological and cellular processes, such as cellular respiration, transcription, and DNA replication.

Pepsin is an enzyme in the stomach that digests proteins. Because it is active in the stomach, which is highly acidic, pepsin best functions at a low pH between 2 and 2.5.

Pepsinogen is secreted by chief cells and converted into active pepsin after catalyzation by hydrochloric acid. The acid is secreted by parietal cells in response to gastrin secretion by G cells. After the stomach contents enter the duodenum of the small intestine, the acid is neutralized by bicarbonate secretions from the pancreas. This prevents the acid from damaging the walls of the small intestine.

You should immediately realize that amylase is an enzyme because it ends in "-ase". Remember that enzymes are proteins; therefore they are made up of amino acids. All amino acids contain a carboxylic acid (-COOH), an amine (-NH2), and a hydrogen (-H) attached to the central carbon. Phosphate groups (-PO3) are more commonly found in lipids and nucleic acids, not in proteins. No amino acids contain phosphate groups, though phosphates can be added to certain amino acids to activate certain proteins and enzymes (phosphorylation).

Catalysts are molecules that are capable of increasing reaction speed. Enzymes are a particular subset of catalysts; enzymes are proteins that can aid in biological reactions and are crucial to many metabolic processes that occur in cells. Enzymes lower the activation energy of a given reaction, allowing the reaction to proceed faster. The active site of an enzyme is the region of the enzyme that can bind a substrate, when a substrate collides into the enzyme molecule. Joining of an enzyme and substrate results in a chemical reaction whereby the substrates are converted into products. The active site of an enzyme is specific to the substrate's shape, like a lock-and-key mechanism.

Enzymes are catalysts that function to increase the rate of a reaction. All enzymes are proteins and they are never consumed in a reaction. Another form of biological catalyst is ribozymes, which are made of protein and RNA, but are not classified as enzymes.

Enzymes work by lowering the activation energy of a reaction, which can occur either by bringing reactants closer together or by destabilizing the transition state. They do not affect the equilibirum of the reaction, meaning they do not affect the amount of reactants or products. They simply increase the speed at which products can be formed by reducing the amount of energy needed to power the reaction.

Enzymes are biological catalysts that bind to specific substrates. Enzyme activity is tightly regulated by activators and/or inhibitors. Enzymes will change shape as a result in an induced fit when bound to their substrates, activators, and/or inhibitors. Since enzymes are proteins, environmental changes will affect their activity. For example, high temperatures will denature the protein, rendering the enzyme inactive. Isozymes are a group of enzymes that do not have the exact same amino acid sequence, yet they catalyze the same reactions. Enzymes need cofactors, such as prosthetic groups and/or coenzymes in order to function properly. The precursors to coenzymes are vitamins in the diet.

An organism's metabolism is the sum of its chemical processes. Catabolism and anabolism are different aspects of metabolism. Catabolism refers to the breakdown of organic molecules, producing useable forms of energy, such as ATP. Anabolism refers to the use of energy to build macromolecules such as proteins, nucleic acids and carbohydrates.

A catalyst is a substance that can change the rate of a reaction without being consumed by the reaction. Catalysts only affect the speed of the reaction. If a reaction would not occur naturally then the addition of a catalyst will have no effect.

Enzymes are proteins that act as catalysts for reactions. Enzymes are essential in enabling the proper function of human metabolism. If enzymes were absent then chemical traffic throughout the metabolic pathways would become backed up.

Enzymes are catalytic proteins. Enzymes are essential in proper functioning of metabolism because without them chemical traffic throughout the metabolic pathways would become backed up.

Enzymes are proteins that act as catalysts for metabolism. Enzymes are essential in proper functioning of metabolism because without them chemical traffic throughout the metabolic pathways would become backed up.

The investment of energy required to start a reaction is called the free energy of activation or activation energy. Activation energy is usually in the form of heat from the surrounding area that molecules in the reaction absorb.

Temperature and pH can affect enzyme activity because they may alter the shape and effectiveness of the enzyme through protein denaturation. Likewise, the availability of reactants and substrates controls the amount of product that the enzyme can catalyze during the reaction. If they are present in low concentrations, then they will inhibit the enzyme’s activity.

The stomach is an acidic environment; therefore, one would expect pepsin to be most active at an acidic pH. The answer choice “2” is the most acidic pH. It is also the pH that is generally found in the stomach. Although a pH of 6 is slightly acidic, it is not the pH found in the stomach.