Copyright © 20 20 McGraw -Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw -Hill Education Biology , 5th edition by Brooker et. al. Suggested Answers to Collaborative Questions Chapter 1 1. Most biologists would say that theori es are true, but maybe students who are new to the discipline
don’t feel the same way. There are a variety of ways to decide if things are true: exp erimentation, logic,
hearing it from experts, faith, etc. Thi s discussion may be useful, because it may help you decide h ow you
determine whether or not things are true. Maybe you’ve never thought about this before.
2. The male and female alligators don’t h ave different genomes. Somehow, temperature affects the
proteo me. There are a lot of possible things that could happen. For ex ample, higher temperature could
cause a protein that is needed for f emale development to unfold and not work properly. The main idea is
that temperature affects protein structure and function and thereb y influences the proteome. Some
proteins regulate genes and control the genome. If these regulatory proteins were affected by
temperature, they could control which other proteins are made at high and low temperatures.
Chapter 2 1. Protons —These are positively charged particles that are found in the center of the atom , which is
referre d to as the nucleus. The number of protons an atom has is called t he atomic number, and this
defines each type of element. This particle makes up approximately half of the mass of an atom, which is
referred to as the atomic mass.
Neutrons —These are neutral (uncharg ed) particles that are found in the nucleus of the atom. For most atom s of biological importance, the number of neutrons is equal to the nu mber of protons in an atom, but this is not always the case. Atoms with the same number of protons but different numbers of neutrons are called isotopes of each other. Electrons —These are negatively charged particles that are found in orbitals around the nucleus. For atoms, the number of protons is equal to the number of electrons. Th erefore, an atom has no overall net charge. If electrons are added to a n atom or taken away, this will change the charge of the atom, which is now called an ion, thereby changing its properties and reactivity. 2. The partial electric charges aroun d the hydrogen and oxygen atoms in a water molecule make water a
good solvent for many of the chemicals important for life in organisms, such as ions and polar
compounds.
Water can directly participate in typ es of chemical reactions called hydrolysis reactions, which are important in the conversion of certain large molecules into smal ler units that are biologically important. Water has a high heat of vaporizati on, which means that it takes a great deal of heat to change its state from a liquid to a gas. As a result of this, most of the water in our pla net is in liquid form, which is required to support life. Water also has a high heat of fusi on and requires a great deal of energy to be removed from it to turn it from a liquid to a solid. As a result of this, liquid water is very stab le and resistant to temperature change, making it ideal for living organisms. Also see Figure 2. 19. Chapter 3 1. Monosaccharides —These are mono mers and the most simple of the sugars, carbohydrates that often,
but n ot always, taste sweet. A prime example of this type of sugar is glucose, which is used by many
organisms in the production of ATP. Collaborative Questions_Answers For Biology 5th Edition By Robert Brooker, Eric Widmaier, Linda Graham, Peter Stiling (All Chapters, 100% Original Verified, A+ Grade) Copyright © 20 20 McGraw -Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw -Hill Education Disaccharides —These consist of two monosaccharides covalently bonded together. Sucrose is an example of this type of sugar. This is accomplished through a dehydratio n reaction by removing hydrogen from one monosaccharide and a hydroxyl from the other, resulting in the formation of a molecule of water. Polysaccharides —These are polymers that consist of many monosaccharides bonded together. Some examples of polysaccharides are • Glycogen —this is the storage form of glucose in animals. • Starch —this is the storage form of glucose in plants. • Cellulose —this molecule serves as a support molecule in plants. 2. Protection —protect organisms from at tack against disease. Organisms produce specific proteins to fight against specific diseases. Enzymes —increase the rates of chemical r eactions. Without these proteins, metabolism would be very slow. Gene expression and regulation —involved in transcribing genes (converting DNA into RNA), regula ting the activity of genes, and synthesizing polypeptides. Cell signaling —needed for a cell to c ommunicate with other cells and with the environment. Motor proteins —allow cellular movements. Transporters —allow the movement of ion s and molecules across cellular membranes. Chapter 4 1. The term genome refers to the entire genetic complement of a cell, which codes for all of the proteins that a cell can produce. If a cell needs to synthesize a protein, it m ust get the instructions on how to build it from the DNA, which i s found inside the nucleus. The proteome is the entire collection of prot eins that a cell can make. The production of proteins inside the cell is very dynamic and constantly changing based on curre nt conditions in and out of the cell. During different times of a cell’s li fe, it will be required to make different proteins based on the curren t function of the cell. This is accomp lished by accessing different genes from the DNA of the cell. Within each cell is the entire genetic complement of the organism, yet each individual cell will use only part of it to produce the collection of proteins it needs. 2. See Figures 4. 9 and 4. 11 for how the nucleus, ER, and Golgi are arranged relative to each other. Th e nucleus and ER are continuous with each other. The two membranes of the nuclear envelop meet at the nuclear pores. The ER and Go lgi share material via membrane vesicles. Chapter 5 1. Perhaps the main reason why pl asma membrane proteins are good targets for drugs is because the drug do esn’t have to get into the cell to affect the protein’s function. Also, plasma membrane proteins p lay a variety of important roles in the s tructure and function of cells, making them good targets for drugs. To determine if any particular plasma membrane protein is the targe t of a drug, you need to have a method to determine if the protein is working pr operly. For example, if a protein transports glucose in to the cell, you need to have a method to measure glucose uptake. In this c ase, you could add radiolabeled glucose outside the cell and m onitor its uptake over time. If you thought a drug was affecting such a glucose transporter, the rate of glucose uptake would be determined in the presence and absence of the drug. If the glucose transpor ter was the target of the drug, you would expect the drug to have a n effect on the rate of glucose transport. Copyright © 20 20 McGraw -Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw -Hill Education 2. Simple d iffusion: The main advantage is tha t a cell doesn’t have to expend any energy to transport the solute. The disadvantages are that it’s not very specifi c, and it cannot achieve active transport. Facilitated diffusion: The advantage is that it can spe cifically move solutes across the membrane down their gradients. The disadvantage is that it cannot achieve active transport. Active transport: The advantages ar e that it can specifically move solutes across a membrane and it can move them against a gradi ent. A disadvantage is that it uses energy in the process. Endocytosis: The main advantage i s that it can move large things across the membrane. A disadvanta ge would be that it is a pretty complicated process, which uses a lot of cellular components. Chapter 6 1. Living cells acquire energy to main tain their internal order. This energy comes in different forms. Ligh t energy powers photosynthesis, which then supplies organic m olecules that store and release energy. Living cells are not defying the secon d law of thermodynamics because the law applies to the whole universe. Although cells are highly ordered, the maintenance of cell order increases the net entropy of the universe. For example, cel ls give off heat, which affects the disorder of their surroundings. 2. Having a common energy source allow s a cell to make fewer proteins and thereby keep its biochemical compo sition simpler. It would take a lot of energy to make a Na+/K+-ATPase, a Na+/K+-glucosase, a Na+/K+-sucrase, and a Na+/K+-fatty acidase. Also , having fewer proteins allows a species to have a smaller genome, which improves efficienc y. Chapter 7 1. Compared to most forms of anaerobi c respiration and fermentation, an advantage of aerobic respiration is that it generates more ATP. However, a disadvantage is that i t requires oxygen which may not be available or, in the case of muscl e exertion, may be used up very quickly. The main advantage of anaerob ic respiration and fermentation is that cells can keep making ATP even if oxygen is not available. 2. Solid tumors, such as those found i n lung cancer and liver cancer, are most readily detected via PET scans . The level of hypoxia within a solid tumor is thought to affect the det ection. The center regions of a tumor are often hypoxic, which means they are deficient in oxygen. This hypoxia occurs because of an inade quate blood supply. The hypoxia tends to induce the genes that encode th e enzymes of glycolysis, which, in turn, increases the level of glycolysis of these hypoxic areas. Therefore, the hypoxic areas tend to be very bright on a PET scan. Chapter 8 1. A heterotroph does not have to live in a sunny location. Many heterotrophs have a wide variety o f foods they can eat to sustain their life. However, photoautotrophs can rely on light for their ene rgy needs, which is oftentimes plentiful . On the other hand, when light is not plentiful, phototrophs have trouble staying alive. 2. Under hot and dry conditions, C4 o r CAM plants have the advantage of not requiring as much water, and also they are more ef ficient because they avoid photorespiration. Wi th regard to genes, introducing the gene that encodes PEP carb oxylase would be helpful. Also, adding genes that change leaf struc ture so that both mesophyll and bundle sheath cells would be formed might be po ssible, though that would be more complicated. Chapter 9 1. Direct intercellular signaling —In multicellular organisms, there is usually some form of direct contact between adjacent cells so they can communicate with each other and exchange chemicals between cells.
