Prentice Hall Biology (California)
1st Edition
ISBN: 9780132013529
Textbook solutions
All Solutions
Page 57: Chapter 2 Assessment
Exercise 1
Solution 1
Solution 2
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$textbf{Neutron}$ is a particle present in the atom with $text{underline{no net electrostatic charge}}$.
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$textbf{Ion}$ is the term called to a charged atom or molecule. It is charged since the number of electrons is not equal to the number of protons.
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$textbf{Proton}$ is a subatomic particle having $text{underline{positive net electrostatic charge}}$.
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$textbf{Electron}$ is a subatomic particle with a $text{underline{negative net charge}}$ that moves around the nucleus of an atom.
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Hence, among the given choices the correct answer is $textbf{C}$.
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$c.$ proton
The answer is c, proton. This is because a neutron is a particle with no charge, an electron is a particle with a negative charge, and an ion is an atom that has a positive or negative charge. This leaves the proton, which is a particle with a positive charge.
Result
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$c.$ proton
Exercise 2
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$textbf{Symbol}$ in chemistry is the abbreviation or short notation assigned in a chemical element.
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$textbf{Isotopes}$ are atoms of the same element that have similar number of protons and electrons but $text{underline{different number of neutrons}}$.
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$textbf{Element}$ is the term to describe a pure substance composed of only atoms that have the same numbers of protons in their nucleus. Elements cannot be broken down into simpler substances as compared to chemical compounds.
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$textbf{Compounds}$ are chemical substances consist of two ore more various atoms combined in specific proportions. Compounds can be broken down into simpler substances.
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Hence, among the given choices the correct answer is $textbf{D}$.
Result
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D
Exercise 3
Solution 1
Solution 2
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These two kinds of bonds hold the atoms to form a compound.
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$textbf{Ionic bonding}$ is the total transfer or transport of valence electrons between atoms. This type of chemical bond gives two oppositely charged ions.
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$textbf{Covalent bonding}$ is a type of chemical bond in which sharing of electron pairs occur between the atoms. The electron pairs are known to be bonding pairs and they generate stable balance of attractive and repulsive forces between the atoms.
Step 4
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Hence, the correct answer is $textbf{B}$
Result
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B
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$b.$ sharing of electrons
Covalent bonds are formed when electrons are shared between atoms.
Result
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$b.$ sharing of electrons
Exercise 4
Solution 1
Solution 2
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$b.$ mixture
Sugar and sand create a mixture because they are physically mixed together but are not chemically combined.
Result
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$b.$ mixture
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Compounds are substances that consist of two or more different elements. An example of a compound would be table salt, which consists of the elements sodium and chloride.
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Solutions and suspensions consist of a mixture of a solid and a liquid substance. The difference between the two is that solutions are homogeneous while suspensions are heterogeneous.
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Therefore, when you mix sugar and sand (two solid substances) together in a container, you cause them to form a **mixture**. However, they do not form a solution nor a suspension.
Result
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B
Exercise 5
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A compound that produces H$^{+}$ ions in a solution is called an acid. Acids have a pH value of below 7.
Result
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B. acid
Exercise 6
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The term polymerization is defined as the process of producing polymers or macromolecules that are formed by joining smaller units called monomers.
Result
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D. monomers
Exercise 7
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An amino acid is an organic compound formed by a carboxyl group (-COOH) and an amino group (-NH$_{2}$).
Result
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C
Exercise 8
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A protein is classified as a polymer because it has subunits or monomers which are called amino acids.
Result
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C. amino acids
Exercise 9
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Enzymes affect the reaction rate by lowering the activation energy needed for molecules to react. As a result, the reaction rate speeds up or increases.
Result
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A. lowering the activation energy
Exercise 10
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Active site is the region on an enzyme wherein the reactants bind during a chemical reaction.
Result
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D. active site
Exercise 11
Result
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The atom is the smallest unit of matter. It is made up of three particles which are protons, neutrons, and electrons. Atoms make up an element. An element is a pure substance which cannot be broken down using chemical reactions. An example of an element is the hydrogen. When you combine two or more elements together, a compound is formed. An example of a compound is the pure water, which is a combination of hydrogen and oxygen.
Exercise 12
Result
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A radioactive isotope has an unstable nucleus. This isotope decays or rearranges itself until it reaches a stable state. Radioactive isotopes are used in the field of medicine. Radioisotope technetium-99 is used as a medical tracer that is injected into the body which shows on x-rays. Another use of radioisotope is for dating fossils and rock layers. Uranium-235 can date fossils and rocks that range from 10 million to 4.6 billion years old.
Exercise 13
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Atoms can form compound through the process of chemical bonding.
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There are two kinds of bonds hold the atoms to form a compound: $textbf{Ionic bond}$ and $textbf{Covalent bond}$
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$textbf{Ionic bonding}$ is the total transfer or transport of valence electrons between atoms. This type of chemical bond gives two oppositely charged ions.
Step 4
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$textbf{Covalent bonding}$ is a type of chemical bond in which sharing of electron pairs occurs between the atoms. The electron pairs are known to be bonding pairs and they generate a stable balance of attractive and repulsive forces between the atoms.
Exercise 14
Solution 1
Solution 2
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$textbf{Covalent bonding}$ is a type of chemical bond in which sharing of electron pairs occurs between the atoms. The electron pairs are known to be bonding pairs and they generate a stable balance of attractive and repulsive forces between the atoms.
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In a $textbf{single covalent bond}$ only two electrons are shared between the atoms. While in $textbf{double covalent bond}$ four electrons are being shared. Lastly, in $textbf{triple covalent bon}$, six electrons are being shared together
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Single bond is formed by the sharing of one electron pair, (two electrons); a double bond is formed by the sharing of two electron pairs, (four electrons), whereas a triple bond involves sharing of three electron pairs, (six electrons).
Exercise 15
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Cohesion is the term used to describe the attraction that happens between the molecules of the same substance. The reason why you see water beads on the hood of a car is because the water molecules are pulling each other using cohesive forces. On the other hand, adhesion is the attraction between different substances. An example of adhesion is the capillary action. This occurs when adhesive forces draw the water out of the roots of the plants so it can go up into its stems and leaves.
Exercise 16
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$textbf{Solution}$ is a mixture composed of two or more substances in which the molecules are $text{underline{evenly distributed}}$. A solution is composed of a $textbf{solvent}$ and $textbf{solute}$
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A $textbf{solvent}$ is a substance, usually a liquid that is used to dissolved a solute.
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A $textbf{solute}$ is a subtance that is being dissolved in a mixture.
Exercise 17
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A compound that produces H$^{+}$ ions in a solution is called an acid. Acids have a pH value of below 7. On the contrary, a base is a compound that contains a low concentration of H$^{+}$ ions. In a solution, a base produces hydroxide or OH$^{-}$ ions. It has a pH value that is above 7.
Exercise 18
Solution 1
Solution 2
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$textbf{Polymers}$ are large molecules composed of many smaller molecules called $textbf{monomers}$ that are joined together.
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One example of a polymer is a $text{underline{polysaccharide}}$.
A polysaccharide is sugar macromolecule consists of many smaller monosaccharides (simple sugars) bounded together by glycosidic linkages.
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Polymers are many monomers combined.A polysaccharide is a macromolecule(giant molecule) comprising many monomer units(monosaccharides).for example:many glucose monomers combine to form a polysac(either starch glycogen or cellulose).
Exercise 19
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**Proteins** are large biomolecules composed of nitrogenous organic compounds called ***amino acids***
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It is an essential compound in living organisms since it forms structural components in the body, controls the rate of cellular reactions, and regulates the different cell processes. In addition, it also helps in the transport of substances in the cell and fights diseases or infections.
Exercise 20
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A nucleic acid is a polymer that is formed by smaller units called nucleotides. Nucleotides have three parts that include a 5-carbon sugar, which can either be a ribose or deoxyribose; a phosphate group (PO$_{4}$ $^{3-}$); and a nitrogenous base, which can be a purine or a pyrimidine.
Exercise 21
Solution 1
Solution 2
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RNA and DNA, while thymine is possible only in DNA and uracil is possible only in RNA. the sugar for DNA is dioxyribose and RNA is ribose.
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There are two basic kinds of nucleic acids. One of them is **deoxyribonucleic acid** (DNA), while the other is **ribonucleic acid** (RNA). Each type of nucleic acid has its own properties.
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DNA is usually double-stranded and contains thymine as one of its bases. On the other hand, RNA is usually single-stranded and contains uracil as one of its bases. Both of these nucleic acids can store genetic information.
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Another main difference between DNA and RNA is their sugars. DNA contains **deoxyribose** sugar, while RNA contains **ribose** sugar. These sugars are both known as pentose (5-carbon) sugars, but their chemical structures are slightly different as shown below.
Exercise 22
Solution 1
Solution 2
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A chemical reaction is a process that leads to the transformation of one set of chemical substances to another.
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A *chemical reaction* is a process that results in changes in the chemical or ionic structure of a particular substance or a set of substances, as opposed to a change in physical form.
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One defining feature of a chemical reaction is that chemical bonds may be broken and/or formed between substances. Some chemical reactions require energy, while others release energy.
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As an example, cutting a piece of paper into small pieces is not a chemical reaction. In contrast, burning a piece of paper in a fire (combustion) is considered as a chemical reaction.
Exercise 23
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. The two types of energy changes can occur in a chemical reaction. A chemical reaction can either $text{textcolor{#c34632}{absorb}}$ or $text{textcolor{#19804f}{release}}$ energy.
. A chemical reaction that release energy, occurs spontaneously. A chemical reaction that absorb energy will not happen spontaneously and will not occur without a source of energy.
. A chemical reaction that release energy, occurs spontaneously. A chemical reaction that absorb energy will not happen spontaneously and will not occur without a source of energy.
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A chemical reaction can either $textbf{absorb}$ or $textbf{release}$ energy.
Exercise 24
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Catalysts are agents that speed up the rate of reaction by lowering the activation energy during a chemical reaction. A catalyst is inorganic in nature. On the other hand, an enzyme is a biological or natural catalyst which is in the form of complex proteins. All enzymes are known as catalysts because it speeds up the chemical reaction in organisms. However, not all catalysts are enzymes because enzymes are considered as organic catalysts.
Exercise 25
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Enzymes are biomolecules usually composed of polypeptide chains that act as a catalyst of reaction in living organisms.
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It regulates the rate at which chemical reactions take place and proceed within the cells by binding in the target molecules without itsefl being altered in the process.
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There are many factors that can affect the activity of an enzyme including **pH, temperature**, and **regulatory molecules** present in the system which may result in its “on or off” switch when needed.
Exercise 26
Solution 1
Solution 2
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To increase the pH of a solution, we would need to add something with a high pH.
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Bases have a pH of above 7.
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To increase the pH of the solution, we would need to add a base. Examples of bases are bleach and soap.
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In order to increase the pH of a solution, one must need to add a substance that increases the relative concentration of OH$^-$ ions as compared to the concentration of H$^+$ ions.
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Bases are substances that have a relatively higher concentration of OH$^-$ ions than H$^+$ ions. When a base is added to a solution, it would increase the relative concentration of OH$^-$ ions.
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Because of their high OH$^-$ ion concentration, bases are known to have a high pH. Therefore, adding an adequate amount of **base** (such as bleach) to the solution would increase its pH.
Exercise 27
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Energy-releasing reactions are called **exothermic reactions**. It is a kind of reaction where more energy is released when the chemical bonds are formed in the products compared to when they are broken down back as reactants. This reaction is accompanied by an elevated value of temperature in a reaction mixture
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**Exothermic reactions** are important in living things since they help to carry different life processes such as in metabolism which needs the released energy for it to initiate the process.
Exercise 28
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The graph shows the result from an experiment about the effect of different temperatures in the formation of the total product using only one enzyme.
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The total product generated was doubled when the temperature of the reaction was set to 25$degree$C to 35$degree$C. However, it suddenly dropped to almost zero when the temperature was set at 45$degree$C.
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We can say that the optimal range of temperature for the generation of products can be from 25-35$degree$C, with being 35$degree$C the best temperature. A much higher value of temperature inhibits the function of the enzyme.
Exercise 29
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An experiment involving mixing the sample with water as solvent. Since lipids are non-polar and it is **not generally water-soluble** you will be able to see traces of the sample in the mixture. As opposed if the sample is a carbohydrate, it will be mixed well in the solution.
Exercise 30
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The optimal way to remove the sodium chloride out of the mixture is to dissolve it by adding water. Silica does not interact with water because of the layer of silicon dioxide on its surface. Later we can filtre the mixture to remove the silica and get the salt dissolved in water.
Sodium chloride can be finally separated by evaporating the water.
Result
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To remove sodium chloride out of the mixture we can add water as dissolvent.
Exercise 31
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Carbohydrate is a biomolecule that serves as a source of energy in living things. It is made up of carbon, hydrogen, and oxygen. The general formula for carbohydrate is CH$_{2}$O wherein a carbon atom is combined with two hydrogen atoms and one oxygen atom. It usually occurs in a ratio of 1:2:1. Carbohydrates are classified into simple sugars and complex sugars. An example of a simple sugar is the monosaccharide in the form of glucose. It has a chemical formula of C$_{6}$H$_{12}$O$_{6}$. This means that there are six units of CH$_{2}$O in glucose.
Exercise 32
Solution 1
Solution 2
Step 1
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Result
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Hydrogen Chloride
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A sample diagram of the chemical structure of hydrogen chloride (HCl) is shown below. Hydrogen (H) contains 1 electron (purple) while chloride (Cl) contains 17 electrons (orange).
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When forming hydrogen chloride, hydrogen and chloride are bound together by a single covalent bond. In a covalent bond, electrons are unequally shared between the two atoms.
Exercise 33
Solution 1
Solution 2
Step 1
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**Enzymes** are biomolecules usually composed of polypeptide chains that act as a catalyst of reaction in living organisms. It regulates the rate at which chemical reactions take place and proceed within the cells by binding in the target molecules without itself being altered in the process.
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Enzymes provide the site where reactants (substrates) can be combined together for reaction. The substrates bind to the site on the enzyme called the ***active site***, this eventually forms the “enzyme-substrate complex”. This causes a reduction in the activation energy needed for the given reaction
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There are many factors that can affect the activity of an enzyme including pH, temperature, and regulatory molecules present in the system which may result in its “on or off” switch when needed.
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Hence, if the change in the temperature of pH changes the shape of an enzyme, the ***enzyme might also lose its ability to bind with the substrates and its complex will not be formed***. As a result, it will not be able to speed up or regulate the reaction it usually catalyzed.
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By changing the temperature or pH, the enzyme’s structure will also change. Since the enzyme’s structure is important in how it works with other chemicals, if it is changed it might not be able to function as it should when pH or temperature get too high or too low.
Result
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See solution explanation.
Exercise 34
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Since hydrochloric acid (HCl) is a strong acid with a pH level of 3, a strong base is also needed to neutralize the acidity. This is why magnesium hydroxide or Mg(OH)$_{2}$ is used to reduce the acid in the stomach because it will produce hydroxide or OH$^{-}$ ions which counteracts the high concentration of H$^{+}$ ions in the acid.
Exercise 35
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The formation of the “enzyme-substrate complex” is based on the precise fit of the enzyme and the substrate, you can imagine that the substrates are like key and the enzyme is like a lock. Similar to the concept of lock and key, only the substrate of a specific shape can fit into the active site of an enzyme.
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The analogy is not that perfect since inserting the key into a lock is a physical process, compared to the binding of the substrates at the active site of an enzyme which is a chemical process. In addition, the way substrates fit in the enzymes is not an inflexible process.
Exercise 36
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A forensic scientist would use her knowledge of biology in her work in several ways. If she was given a sample of someone’s DNA she would need to know how to add chemicals to it so that she could try and see if she could identify who it belongs to. Another example is if there was a red liquid found at a crime scene her knowledge of blood pH and consistancy would help her determine if the red liquid is actually blood.
Result
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See solution explanation.
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