Chapter 2 Test - Biology

The negatively charged particle in an atom is called the electron. Protons are positively charged particles, neutrons are neutral particles, and positrons are positively charged antiparticles. Electrons orbit around the nucleus of an atom and are responsible for the chemical behavior of the atom. They are much smaller and lighter than protons and neutrons, and their movement determines the electrical conductivity and other properties of the atom.

Hydrogen bonding is the phenomenon that explains water's high cohesion, adhesion, and heat capacity. Cohesion refers to the attraction between water molecules, which is due to the hydrogen bonds formed between them. Adhesion refers to the attraction between water molecules and other substances, which is also facilitated by hydrogen bonding. Additionally, hydrogen bonding allows water to have a high heat capacity, meaning it can absorb and retain a large amount of heat without a significant increase in temperature. This is because the energy is used to break the hydrogen bonds rather than increasing the kinetic energy of the water molecules.

The statement "a molecule is made of only ionic bonds" is false. A molecule can be made up of different types of bonds, including covalent, polar covalent, and metallic bonds. Ionic bonds occur between atoms with significantly different electronegativities, resulting in the transfer of electrons, while covalent bonds involve the sharing of electrons between atoms. Therefore, molecules can have a combination of different types of bonds, not just ionic bonds.

Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons. This means that isotopes have the same atomic number (which is determined by the number of protons) but different mass numbers (which is determined by the total number of protons and neutrons). Isotopes can have slightly different physical properties due to their different mass numbers, but they still belong to the same element because they have the same number of protons.

A covalent bond is formed by the sharing of electrons between two atoms. In a covalent bond, the atoms involved share one or more pairs of electrons in order to achieve a stable electron configuration. This sharing of electrons allows both atoms to fill their outermost energy levels and achieve a more stable state. The transferring of electrons or neutrons is not involved in the formation of a covalent bond.

A buffer is a solution that resists changes in pH when small amounts of acid or base are added. It consists of a weak acid and its conjugate base (or a weak base and its conjugate acid) that can react with any added acid or base to maintain the pH within a certain range. Therefore, using a buffer is an effective way for a scientist to stabilize the pH of a solution.

Starch is a complex carbohydrate, which means it is made up of many repeating units called monomers. The monomer of starch is glucose. Glucose is a simple sugar that is commonly found in many foods and is an important source of energy for the body. When multiple glucose molecules join together through chemical bonds, they form starch molecules. Therefore, glucose is the correct answer as it is the building block of starch.

An ionic bond is formed by the transferring of electrons. In an ionic bond, one atom donates electrons to another atom, resulting in the formation of positively charged ions (cation) and negatively charged ions (anion). These oppositely charged ions are attracted to each other and form a strong bond. The transfer of electrons allows both atoms to achieve a stable electron configuration, similar to that of noble gases. This type of bonding is commonly observed between metals and non-metals.

Water molecules are composed of two hydrogen atoms and one oxygen atom. In a container full of water molecules, the hydrogens are attracted to the oxygen atoms of other water molecules. This attraction is due to the difference in electronegativity between hydrogen and oxygen, which creates a partial positive charge on the hydrogen atom and a partial negative charge on the oxygen atom. This polarity allows for hydrogen bonding to occur, with the positive hydrogen being attracted to the negative oxygen.

Enzymes are proteins that act as catalysts in biological reactions. They speed up the rate of chemical reactions by lowering the activation energy required for the reaction to occur. Enzymes are made up of amino acids and have a specific three-dimensional structure that allows them to bind to substrates and facilitate the conversion of reactants into products. Therefore, enzymes are normally considered as part of the group of proteins.

In an enzyme catalyzed reaction, the reactants that bind to the active site of the enzyme and undergo a chemical transformation are called substrates. Enzymes are biological catalysts that speed up reactions by lowering the activation energy required for the reaction to occur. The substrates bind to the enzyme's active site, where they are held in a specific orientation and undergo a reaction to form products. Therefore, the correct answer is substrates.

The pH scale depends upon the hydrogen ion concentration of a solution. The pH scale is a measure of the acidity or alkalinity of a solution, with a pH of 7 being neutral. The concentration of hydrogen ions determines whether a solution is acidic (higher concentration of hydrogen ions) or alkaline (lower concentration of hydrogen ions). Therefore, the correct answer is hydrogen ion.

The term used to describe the combination of substrates bound to the enzyme is the enzyme-substrate complex. This refers to the temporary association between the enzyme and its substrate(s) during a chemical reaction. The enzyme-substrate complex is formed when the substrate(s) bind to the active site of the enzyme, allowing the reaction to occur. Once the reaction is complete, the products are released and the enzyme can bind to new substrates.

A false substrate does not change the shape of an enzyme's active site. The active site of an enzyme is the region where the substrate binds and the chemical reaction takes place. A false substrate is a molecule that resembles the substrate but cannot undergo the same reaction. When a false substrate binds to the active site, it does not cause any conformational changes in the enzyme's active site. Therefore, it does not alter the shape of the active site and does not affect the enzyme's activity.

In an element, all of the atoms are of the same type. This means that they have the same number of protons in their nucleus, which determines their atomic number and defines the element. Each element on the periodic table is made up of atoms that have the same number of protons, giving them unique properties and characteristics. Therefore, the correct answer is that all atoms in an element are of the same type.

An isotope is a variant of an element that has the same number of protons but a different number of neutrons. This means that isotopes have the same number of protons (which determines the element's identity) and different numbers of neutrons. The number of electrons in an atom is equal to the number of protons, so it remains the same in isotopes.

The beading of water is due to cohesion. Cohesion is the attractive force between molecules of the same substance, in this case, water molecules. This force causes water molecules to stick together, forming droplets. The cohesive forces are stronger than the adhesive forces between water and other surfaces, which is why water tends to bead up rather than spread out.

In a suspension, the particles are often unable to completely mix and will drift to the bottom of the container. This is because suspensions consist of larger particles that are not soluble in the solvent. Due to their size and weight, these particles settle down over time, causing them to separate from the mixture and accumulate at the bottom. This characteristic of suspensions is commonly observed in various mixtures such as muddy water or sand in water.

Enzymes speed up the rate of reaction by lowering the activation energy. Activation energy is the energy required for a reaction to occur. Enzymes act as catalysts, reducing the amount of energy needed for the reaction to start. They do this by binding to the reactants and bringing them closer together, which increases the likelihood of a successful collision and formation of the product. By lowering the activation energy, enzymes enable reactions to occur more quickly and efficiently.

Bases produce hydroxide ions in a solution. When a base is dissolved in water, it dissociates to release hydroxide ions (OH-) which can react with hydrogen ions (H+) from an acid to form water. This reaction is known as neutralization. Bases have a pH greater than 7 and can be identified by their bitter taste and slippery feel. Examples of bases include sodium hydroxide (NaOH) and ammonia (NH3).

A radioactive isotope is characterized by having an unstable nucleus, meaning that the number of protons and neutrons in the nucleus is not balanced. This instability causes the isotope to undergo radioactive decay, where it emits radiation in the form of particles or energy in order to achieve a more stable state. The instability of the nucleus is what distinguishes radioactive isotopes from stable ones, which have a balanced and stable nucleus. An unstable electron, unstable personality, or stable electron cloud do not accurately describe the characteristics of a radioactive isotope.

Lipids are not considered true polymers because they do not consist of repeating units like nucleic acids, proteins, and carbohydrates do. While lipids are composed of smaller molecules, they do not exhibit the same level of repeating structure as true polymers. Lipids include substances such as fats, oils, and waxes, which serve various functions in the body but do not fit the definition of a polymer.

Hormones, steroids, and sterols are often made from lipids. Lipids are a diverse group of biomolecules that include fats, oils, hormones, and steroids. Hormones are chemical messengers that regulate various physiological processes in the body. Steroids are a type of lipid that have a specific structure and function, including hormone regulation. Sterols are another type of lipid that are important components of cell membranes and are also precursors for the synthesis of hormones and steroids. Therefore, all three options - hormones, steroids, and sterols - can be made from lipids.

In an acidic solution, hydrogen ions (H+) are released. These hydrogen ions can combine with water molecules to form hydronium ions (H3O+). Therefore, another name for the hydrogen ion in an acidic solution is hydronium.