Biochemistry in Medicine

Contents Preface............................................................................................................................................. 8 Chapter 1: Water and Biochemistry .............................................................................................. 10 Structure of Water ..................................................................................................................... 10 Chemical Properties of Water ................................................................................................... 10 Density as it Relates to Water ................................................................................................... 12 Water as a Universal Solvent .................................................................................................... 13 Water and Hydrogen Bonding .................................................................................................. 15 Key Takeaways ......................................................................................................................... 15 Quiz ........................................................................................................................................... 15 Chapter 2: Proteins and Amino Acids ...........................................Error! Bookmark not defined.

Amino Acids ..............................................................................Error! Bookmark not defined.

Amino Acid Structure ................................................................Error! Bookmark not defined.

Amino Acids in Biochemistry ...................................................Error! Bookmark not defined.

Non-proteinogenic Amino Acids ...............................................Error! Bookmark not defined.

Proteins ......................................................................................Error! Bookmark not defined.

Biochemistry of Proteins............................................................Error! Bookmark not defined.

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Chapter 3: Carbohydrates and Sugars ............................................Error! Bookmark not defined.

Sugars .........................................................................................Error! Bookmark not defined.

Types of Sugars..........................................................................Error! Bookmark not defined.

Health Effects of Sugar ..............................................................Error! Bookmark not defined.

Carbohydrates ............................................................................Error! Bookmark not defined.

Carbohydrate Structure ..............................................................Error! Bookmark not defined.

Classifying Monosaccharides ....................................................Error! Bookmark not defined.

Classifying Disaccharides ..........................................................Error! Bookmark not defined.

Carbohydrates in Nutrition ........................................................Error! Bookmark not defined.

Carbohydrate Metabolism ..........................................................Error! Bookmark not defined.

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Chapter 4: Lipids and Fatty Acids .................................................Error! Bookmark not defined.

Fatty Acids .................................................................................Error! Bookmark not defined.

Types of Fatty Acids ..................................................................Error! Bookmark not defined.

Fatty Acid Synthesis ..................................................................Error! Bookmark not defined.

Hydrogenation and Oxygenation of Fatty Acids .......................Error! Bookmark not defined.

Digestion and Metabolism of Fatty Acids .................................Error! Bookmark not defined.

Essential Fatty Acids..................................................................Error! Bookmark not defined.

Lipids .........................................................................................Error! Bookmark not defined.

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Biosynthesis and Degradation of Lipids ....................................Error! Bookmark not defined.

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Chapter 5: DNA, RNA, and Nucleotides .......................................Error! Bookmark not defined.

Nucleotides ................................................................................Error! Bookmark not defined.

Nucleotide Structure ..................................................................Error! Bookmark not defined.

Nucleotide Synthesis ..................................................................Error! Bookmark not defined.

Deoxyribonucleic Acid or DNA ................................................Error! Bookmark not defined.

DNA Chemical Properties .........................................................Error! Bookmark not defined.

Function of DNA .......................................................................Error! Bookmark not defined.

Proteins associated with DNA ...................................................Error! Bookmark not defined.

Ribonucleic Acid or RNA ..........................................................Error! Bookmark not defined.

Structure of RNA .......................................................................Error! Bookmark not defined.

Synthesis of RNA ......................................................................Error! Bookmark not defined.

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Chapter 6: Enzymes and Enzymology ...........................................Error! Bookmark not defined.

Enzymes .....................................................................................Error! Bookmark not defined.

Naming Enzymes .......................................................................Error! Bookmark not defined.

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Enzyme Inhibition ......................................................................Error! Bookmark not defined.

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Enzymes and Diseases ...............................................................Error! Bookmark not defined.

Enzymology ...............................................................................Error! Bookmark not defined.

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Chapter 7: Aerobic Metabolism .....................................................Error! Bookmark not defined.

Cellular Respiration ...................................................................Error! Bookmark not defined.

Glycolysis ..................................................................................Error! Bookmark not defined.

Krebs Cycle................................................................................Error! Bookmark not defined.

Total Sources of ATP.................................................................Error! Bookmark not defined.

Aerobic Metabolism on a Large Scale .......................................Error! Bookmark not defined.

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Chapter 8: Anaerobic Metabolism .............................................Error! Bookmark not defined.

Fermentation ..............................................................................Error! Bookmark not defined.

Gut Fermentation Syndrome ......................................................Error! Bookmark not defined.

Anaerobic Exercise ....................................................................Error! Bookmark not defined.

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Chapter 9: Glucose Catabolism .....................................................Error! Bookmark not defined.

Carbohydrate Catabolism...........................................................Error! Bookmark not defined.

Glycolysis ..................................................................................Error! Bookmark not defined.

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Chapter 10: Citric Acid Cycle........................................................Error! Bookmark not defined.

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Oxidative Phosphorylation.........................................................Error! Bookmark not defined.

Electron and Proton Transfer Molecules ...................................Error! Bookmark not defined.

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Chapter 10: Gluconeogenesis and Glycogenesis ...........................Error! Bookmark not defined.

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Cori Cycle ..................................................................................Error! Bookmark not defined.

Glycogenesis ..............................................................................Error! Bookmark not defined.

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Glycogen Phosphorylase ............................................................Error! Bookmark not defined.

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Chapter 12: Biochemistry in Medicine ..........................................Error! Bookmark not defined.

Biochemistry and other Disciplines ...........................................Error! Bookmark not defined.

Blood Testing and Biochemistry ...............................................Error! Bookmark not defined.

Biochemical Nutrition ................................................................Error! Bookmark not defined.

Biochemistry and Pharmacology ...............................................Error! Bookmark not defined.

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Welcome to Biochemistry, a Medical School Crash Course written by our team of medical content developers and narrated by (your name) Presented by AudioLearn Written by experts and authorities in the field and professionally narrated for easy listening, this crash course is a valuable tool both during school and when preparing for the USMLE, or if you’re simply interested in the subject of human Biochemistry.

The audio is focused and high-yield, covering the most important topics you might expect to learn in a typical Medical school Biochemistry course. Included are both capsule and detailed explanations of critical issues and topics you must know to master Medical School Level Biochemistry.

The material is accurate, up to date and broken down into bitesized sections.

There is a Q&A and a “key takeaways” section following each topic to review questions commonly tested and drive home key points.

Also included is a comprehensive test containing the top 100 most commonly tested questions in Biochemistry with the correct answers.

To get the most out of this course, we recommend that you listen to the entire audio once while taking notes, then go back and listen to areas you had difficulties with.

AudioLearn's Medical School Crash Courses support your studies, help with USMLE preparation and provide a comprehensive audio review of the topic matter for anyone interested in what medical students are taught in a typical medical school Biochemistry course.

In this course, we'll cover the following topics:

Water and Biochemistry Proteins and Amino Acids Carbohydrates and Sugars Lipids and Fatty Acids DNA, RNA and Nucleotides Enzymes and Enzymology Aerobic Metabolism Anaerobic Metabolism Glucose Catabolism Citric Aid Cycle Gluconeogenesis and Glycogenesis and Biochemistry in Medicine

Now, let's get started.

Conclusion: This concludes our lesson on Biochemistry Now would be a good time to go back and re- visit areas you found challenging. We hope you found this to be a great learning experience and invite you to check out our other titles in this series including: Human Anatomy Cell Biology and Histology Embryology Psychiatry Genetics Microbiology and Immunology Behavioral Sciences Pharmacology Pathology Human Physiology Nutrition Internal Medicine

Pediatrics Obstetrics Gynecology Surgery Preventive Medicine Thank you for listening and good luck!

This has been Biochemistry, a Medical School Crash Course written by our team of medical content developers and narrated by (your name) Presented by AudioLearn

Introduction to Biochemistry Preface This course is to be intended to involve a basic discussion of biochemical principles, the various molecules involved in biochemistry, and how they work together to create and degrade biochemical molecules. The first chapter focuses primarily on the biochemistry of water, which is the universal solvent because it dissolves most of the molecules in the body.

The second chapter presents amino acids, which are the building blocks of proteins. There are some amino acids that are essential, meaning the human body cannot manufacture them but they must be consumed in the diet to be incorporated into proteins In the third chapter of the course, simple sugars, disaccharides, and polysaccharides will be the focus of the discussion. Different organisms have storage polysaccharides, including glycogen (in humans), starches, and cellulose (which can’t be metabolized by humans.

Chapter four of the course will involve a discussion of fatty acids and lipids. Like certain essential amino acids, there are specific omega-3 and omega-6 fatty acids that cannot be made by the body but must be incorporated as part of the diet in order to make longer chain fatty acids and triglycerides.

Chapter five of the course will involve a basic focus on nucleotides, which are the building blocks of nucleic acids, such as RNA and DNA. Both long-chain biochemical molecules are important to gene expression, transcription, and translation of proteins from genetic material.

In chapter six of the course, enzymes and enzymology will be discussed. Most enzymes are protein-based and are translated/made in the ribosomes. There are some enzymes, called ribozymes, that are made from RNA that act in the ribosomes of the body to create proteins.

The seventh chapter of the course will focus on most aspects of aerobic metabolism. Aerobic metabolism is the main form of metabolism that occurs in the human body as we have oxygen to drive this form of metabolism.

The eighth chapter of the course will mainly focus on anaerobic metabolism, which is the type of metabolism that occurs in anaerobic organisms that don’t utilize oxygen or by muscle cells during intense activity when there isn’t enough oxygen to fuel the muscle cells.

In the ninth chapter of the course, the main discussion will be on the topic of glucose catabolism. Glucose gets broken down first in glycolysis into pyruvate, lactic acid, and other products. The breakdown products can stay that way or can go into further oxygen-based reactions to further oxidize the sugar.

The tenth chapter of the course will focus mainly on the citric acid or Krebs cycle, which is the way in which glycose metabolites get further oxidized into CO2 and water, with preservation of most of the intermediary products.

The eleventh chapter of the course will be a discussion of gluconeogenesis and glycogenesis. In gluconeogenesis, the main outcome is the creation of glucose from other types of molecules. In some cases, the glucose is then metabolized while, in other cases, the glucose gets stored as glycogen in liver, fat, and muscle cells.

The last and twelfth chapter of the course will present the ways biochemistry interacts with various aspects of medicine, including normal physiological processes, disease states, food biochemistry, and the pharmacology of drugs as it applies to the biochemistry of medicines and drugs developed and taken by the human body at all times.

Altogether, most aspects of the biochemistry of the human body will be discussed in this course so that students understand the processes that go on in the body’s cells to drive the synthesis and breakdown of molecules using energy in some processes and creating energy in other processes.

Chapter 1: Water and Biochemistry This course is designed to be a discussion of the basics of biochemistry. All of biochemistry begins with a discussion of water, which is the basis behind many biochemical reactions. Water has many biochemical properties that make it important in almost all biochemical functions of the body. In this first chapter, we will discuss the biochemistry of water and how it is important in biochemical reactions, cellular biochemistry, and in metabolism.

Structure of Water Water has the molecular formula of H2O, meaning that it contains two hydrogen molecules and one oxygen molecule--which together make the entire water molecule. Water makes up about seventy percent of the weight of most living organisms. Polar covalent bonds connect the different ions that make up the molecule. Water is considered the universal solvent because it can dissolve many types of biochemical molecules. There are many unique properties of water that make it an important biochemical molecule.

The water molecule consists of two pairs of electrons around an oxygen molecule. The attachment is via a covalent bond that form a tetrahedral arrangement around the oxygen atom having a predicted bond angle of 109.5° between each electron. Because electron pairs repel one another, the actual bond angle between the hydrogen atoms is slightly closer than that at approximately 104.5°. This gives the geometry of a molecule of water as being angular or bent, which gives water its polar trait in biochemical reactions.

The partial charges on both the hydrogen ions and oxygen ion allow the water molecule to participate in many biochemical reactions. The oxygen atom is electrically negatively charged, while the hydrogen ions are positively charged. Together, this gives the oxygen an affinity to other water molecules as well as the ability to ionize. The ability of hydrogen ions to covalently bond to other molecules makes the water molecule have strong interactions with other molecules. Water also has a high melting point and they high boiling point. It has a high heat of vaporization and a high surface tension.

Chemical Properties of Water

As mentioned, some of the unique properties of water include a high surface tension, a high heat capacity, a high boiling point, and a high melting point. This means that the bonding between water and many other molecules is extremely high.

The high melting point and the high heat of vaporization are basically caused by the attraction between two molecules of water that are adjacent to one another. Each hydrogen ion inside a water molecule shares an electron pair with the central oxygen atom in the water molecule.

The result is that each hydrogen molecule has a slightly positive charge, which is attracted to the electronegative charge of the oxygen molecule. This type of bonding is what allows for the molecular process of water called hydrogen bonding.

The specific heat of a molecule is the amount of heat required to raise the temperature of one gram of water by one degree Celsius. Water has an extremely high heat capacity, meaning that it changes temperature very slowly after gaining or losing physical energy. After ammonia, water has the highest specific heat capacity of any other molecule. This is because of the hydrogen bonding between the molecules. When heat is absorbed, the hydrogen bonds break, allowing the molecules of water to flow freely. When the temperature drops, the hydrogen bonds re-form and energy is released. This resistance to a sudden temperature change makes water a good substrate for organisms to survive in without having to suffer extremes in temperature fluctuation. Because most organisms are made from water, they are able to regulate their internal body temperature.

Compared to other hydride molecules, water or H2O, has a high melting point as well. This is also due to the high hydrogen bonding between the water molecules. When water is solid (as in ice), there are four different hydrogen bonds involved. Two hydrogens are each capable of bonding as a bond donor and one oxygen molecule is able to accept two hydrogen bonds from nearby molecules.

Water has a higher boiling point than one would expect. The reason for this is the same as is true for the melting point. There is such a strong intermolecular force between the molecules of water that much more force is required to break the molecules apart so they can turn into gaseous form. Water boils at about 100 degrees Celsius or about 212 degrees Fahrenheit.

The definition of heat of vaporization is the amount of heat needed to change a gram of water in liquid form into its gaseous form. The heat of vaporization of water is high because of the hydrogen binding between the molecules. If you think about it, the world is covered almost entirely in water, giving it a higher ability to retain heat and giving it a more stable climate than other planets, giving it the ability to support life. Evaporative cooling of water happens when the liquid molecules that have the greatest amount of kinetic energy leave the water form to turn into gaseous form, stabilizing the temperature around bodies of water, such as lakes and ponds. It also keeps animals and plants from being overheated when being heated up.

There is a property of molecules called “a colligative property”. This is the collection of properties of a solution that correlate to how many molecules exist in a given volume of solvent rather than what the actual molecules in the solution are. An example of this a colligative property in relationship to water is the osmotic pressure, the freezing point, and the boiling

point. Water has a collection of colligative properties because it acts as a solution that dissolves solutes, such as sodium chloride in the extravascular tissues of the human body. When sodium chloride is added as a solute to water in solution, the boiling point will increase even further.

When NaCl is structured like a lattice around water molecules, the structure will often break down because of the strong solute to solution interaction when compared to the solute to solute interaction. This leads to fewer freely-floating water molecules in the solution, which causes a decrease in entropy of the system. This means that a higher enthalpy change (energy change) is required to break the forces between the molecules to force them into gaseous form.

The freezing point of water is decreased when it acts as a solvent. This is because the solute doesn’t fit into the watery crystalline structure and less free space is given to other molecules when the water turns into a crystalline state. More enthalpy or energy change is necessary to balance the entropy loss required to freeze the water. Salt is added to snow in winter to melt it faster at a lower freezing temperature. The colligative property of water is determined by the solute added to the solution rather than the amount of solute added to the solution.

Density as it Relates to Water Water is a rare substance that is actually less dense as a solid when compared to its liquid form.

Once again, it is the hydrogen bonding of water that is the reason behind this. This allows animals, plants, and humans to survive in sub-zero temperatures because a lake or pond will freeze from the top down instead of from the bottom up and ice floats on the water surface. As the ambient temperature drops below the freezing point of water, the molecules of water form a lattice with four neighboring water molecules. The hydrogen molecules separate these molecules further apart than they would be in their liquid state, making solid water less dense than liquid water. As the temperature increases, this crystalline structure breaks down and the hydrogen bonds become denser, making liquid water. Water is in its densest state at about four degrees Celsius.

The property of cohesion involves having individual water molecules sticking together secondary to the property of hydrogen bonding that we have already discussed. Hydrogen bonding is very fragile when water is in its liquid form but, because of cohesion, water is better structured as a liquid when compared to other organic liquids. The bonds break and reconnect at a high frequency when water is in its liquid phase, leading to both a strong capillary action and a high surface tension. This cohesive property of water is more important to plants than it is to animals and, without the property of cohesion, plants would be dehydrated and could not undergo the photosynthetic process.

Cohesion results in a high surface tension of water. Water has the highest surface tension of most other liquid substances (other than mercury) because of the hydrogen bonding between the various molecules. This property allows for the ability of water to act like a stretchable film that can support objects that are extremely heavy. Some aquatic organisms have evolved to

have a large surface area compared to their body weight so they can float without breaking the surface tension of water.

Water is amphoteric, meaning it can be an acid or a base. When water is part of a solution, it will change the equilibrium of the solution. When it interacts with a highly acidic solute, it will act as a base and, when it interacts with a highly basic solute, it will act as an acid. Because it has two single hydrogen ions as part of the molecule, it can act as an electron pair donor in biochemical reactions.

Water as a Universal Solvent Water is considered a universal solvent because it can dissociate or dissolve most organic compounds. This is because it is a highly polar molecule, with a great deal of electronegativity associated with its oxygen component when compared to its hydrogen component. The positive electric charge of the molecule (the hydrogen side) is attracted to the negative parts of the solute being dissolved, while the positive charge of the molecule (the oxygen side) is attracted to the positive parts of the solute. This makes water able to dissociate and break ionic compounds into separate, dissolvable components.

There is a chemical term known as the dielectric constant. It refers to the ability of electrons to migrate toward the pole of a positively charged molecule and away from the negatively charged molecules. When this happens, the molecule is called “polarized”. Water has a dipole moment of 6.17 x 10-30, making it a polarized molecule.

The dielectric constant of a molecule is a measurement of how polarized it is. Water has a high dielectric constant because of its high dipole moment. This gives water the ability to surround ions, blocking the charges of the ions so it can be a good solvent for any type of polar or ionic substance. Therefore, it is called a universal solvent as many types of ions can dissolve in it.

Because of the polar aspect of water and its ready ability to undergo hydrogen bonding, polar molecules that are uncharged can easily dissolve in it. Water stabilizes these molecules by the effect of its hydrogen-binding ability between any polar molecule and the water molecule. Any molecule that has an N-H bond, alcohols, aldehydes, and ketones all can form hydrogen bonds, making them soluble in water. All of these molecules are biomolecules found in the human body.

The hydrogen bonds between an uncharged polar molecule and water will be the strongest when the hydrogen atom in the molecule is in a straight line between two different electronegative atoms. Because of this, the property of hydrogen bonding in the water molecule is very directional. Water has the unique ability to recognize and adapt to the different shapes of organic molecules so that it can keep them in solution.

Water also has the capability of forming a hydration shell. This is a shell that forms in a waterbased solution when the solute dissolves in the water. The solute can be surrounded by the

positively-charged hydrogen ions that bind to the solute, allowing it to stay in the watery solution.

Water has the ability to be stabilizing to ions like sodium and chloride. It hydrates both ions and decreases the electrostatic interaction between the ions, weakening their tendency to want to go out of solution and form a crystalline lattice. This is also the case with protonated amines, anhydride molecules, carbolic acid, and other biomolecules. Instead of precipitating out as solute-solute solids, they form solute-solvent interactions, keeping the molecules in solution. In effect, water acts as a screen between the polar aspects of the molecule that would have the solute bind with itself instead of water.

Water is an extremely versatile solvent. When a crystal of an ionic compound is placed in water, the ions are broken apart by the water solvent. Hydrogen, being negatively charged, will attract any part of the molecule that is positively charged, while oxygen, being positively charged, will attract any part of the molecule that is negatively charged. It effectively forms a shell around each positively and negatively charged component of an ionic substance so that they don’t bind to each other and precipitate out of solution. The substances can move freely in water is a favorable, energy-free occurrence.

Water can interact with hydrophobic molecules as well. It causes that part of a hydrophobic molecule to hide within the hydrophilic components of the molecule, leaving the hydrophobic portion hidden and the hydrophilic part exposed. This is an energetically unfavorable interaction but needs to happen to keep the hydrophobic parts of the molecule away from the water. Organic hydrophobic molecules form a micelle, which involves the hydrophilic parts being exposed to water and shielding the hydrophobic parts.

Non-polar substances will not dissolve in water and form an unfavorable interaction with water.

The hydrocarbon backbone of many organic molecules must form micelles to be dissolved in water and decrease the entropy of water, which is considered an unfavorable process.

In humans and animals made from cells surrounded by lipids, water needs to be a part of this system. One typical micelle found in nature is the lipid bilayer of the plasma membrane of the cell. There are polar heads on the phospholipids that make up the lipid bilayer that shield the lipid portions of the bilayer. Fat-soluble molecules can get inside the membrane but ionic compounds cannot.

When enzymes and other organic molecules are present in solution, sometimes the water molecules form an ordered structure that is separate from the enzymes and the molecules they work on for the interaction to occur. This increases the disorder of the molecules, increasing the entropy and allowing the process that is to occur between the enzyme and its substrate to become more favorable. This forms an enzyme-substrate complex that starts the enzymatic process. This is considered an example of “desolvation.”

Water is not just the solvent the human body uses as the main thing biomolecules are dissolved in. It plays a significant role in many biochemical reactions inside the body. One specific example is the transformation of adenosine diphosphate (ADP) to adenosine triphosphate (ATP), which is how the human body gets its energy. There is a specific condensation that

occurs, in which water is produced for ADP to take on its third phosphate group. Water is again necessary for ATP to become hydrated enough to release its energy. Water is rich in electrons, in which the oxygen component serves as a nucleophile. These types of reactions release energy and are favorable in the biochemical environment. The redox reactions that occur in the human body also require water.

Water and Hydrogen Bonding The hydrogen bonds so important regarding water, along with ionic bonding, hydrophobic bonding, and Van der Waal interactions between molecules are much weaker than any covalent bond in a molecule but, even though they are weak, they are cumulative and have a great effect on what happens inside the human body when it comes to the chemistry of the human body. Any given enzymatic may rely on several of these bonding types, of which hydrogen bonding usually involves the water molecule.

The bonding that occurs in enzymatic reactions results in a net decrease in the free energy of the environment and an instability of covalent bonds that then can be overcome to break the covalent bond of a substrate, altering the chemical structure of the substrate as part of the enzymatic reaction. The stability of the covalent bond changes exponentially with the binding energy. Large macromolecules, such as RNA, DNA, and proteins have many different sites of potential bonding by the various types of bonds mentioned above that are always acting maximally on the macromolecule. It is these types of bonds that ultimately control the overall three-dimensional structure of the macromolecule.

Key Takeaways 

Water is the universal solvent found in almost all biochemical systems.

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Hydrogen bonding is important to the function of water in biochemical reactions.

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Water interacts with hydrophobic molecules because these molecules form micelles that keep the hydrophobic parts of the molecule away from water.

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Water is not only an important solvent but it is a part of many biochemical reactions.

Quiz 1. How many oxygen atoms are in a single molecule of water? a. One b. Two c. Three

d. It depends on its charge Answer: a. Each water molecule has just one atom of oxygen, regardless of the charge of the molecule, which is normally neutral because of the two hydrogen ions that have a strong affinity for the oxygen atom.

2. What property of water allows for its high melting point? a. The hydrogen and oxygen bonding is extremely tight. b. Water has a high affinity for ions that do not melt. c. Water molecules have a high affinity for each other. d. Water has a high covalent bond between the water molecules.

Answer: c. Water has a high melting point because water molecules have a high affinity for each other.

3. Hydrogen bonding in a water molecule allows for what property? a. High heat capacity b. High melting point c. High boiling point d. All of the above Answer: d. The hydrogen bonding in a water molecule allows for its high heat capacity, its high melting point, and its high boiling point.

4. What can be said about the boiling point of water? a. It is lower than expected because the forces between the water molecules are weaker than other molecules of its type. b. It is higher than expected because the forces between the water molecules are greater than other molecules of its type. c. it is about the same as other molecules of its type at about 212 degrees Fahrenheit. d. It is higher than it should be at about 120 degrees Celsius.

Answer: b. The molecules of water have stronger forces than other molecules of its type, giving it a higher than expected boiling point at about 100 degrees Celsius.

5. What aspect of water stabilizes the heat environment of the area around small bodies of water? a. Its high melting point. b. Its high boiling point.

c. Its high specific heat. d. Its high heat of vaporization.

Answer: d. Water’s high heat of vaporization is what prevents water from turning from its liquid to gaseous form without the need for a high expenditure of energy.

6. There is hydrogen bonding occurring with regard to water that is responsible for much of its properties. Describe what this hydrogen bonding is all about? a. Hydrogen molecules bind tightly to the oxygen molecule, preventing its breakup. b. Hydrogen molecules bind to other hydrogen molecules next to it, causing an increased affinity for each other. c. Hydrogen forces occur between the oxygen molecules on the water molecule, causing an increased affinity between the different water molecules. d. Hydrogen has an affinity for the oxygen atom on another oxygen molecule, accounting for a high affinity between the molecules of water.

Answer: b. Hydrogen molecules in different molecules of water nearby have a bond between one another, called hydrogen bonding, which accounts for an increased affinity of water molecules for one another.

7. How does water prevent biomolecules and ionic substances from precipitating out of solution? a. It is highly polar so it promotes the formation of solute-solvent bonds, preventing solute-solute bonds. b. It bonds covalently with solutes so they can’t get out of solution. c. The hydrogen bonds break in the water molecule and coat the solute, preventing its precipitation. d. The oxygen part of the molecule binds to the hydrogen of the solutes, preventing their precipitation.

Answer: a. Water is highly polar, forming solute to solvent bonds, preventing solute to solute bonds that would take the solute and allow it to precipitate out of solution.

8. What causes the shield that prevents sodium chloride from precipitating? a. The water molecule is larger than the sodium chloride molecule so it keeps it from precipitating. b. The water molecule surrounds the sodium chloride molecule on all sides so it can’t get near any other sodium chloride molecule. c. Water is small so it can surround the sodium chloride molecule on all of its sides, keeping it from precipitating.

d. Water is polar and it attracts different charges on the sodium chloride molecule, making it unable to attract the sodium and chloride to one another.

Answer: d. Water keeps sodium chloride from precipitating because it is polar and its different charges attract the positive and negative charge on sodium chloride molecule, keeping the sodium and chloride from binding to each other in solution.

9. How is it that human cells can be surrounded by lipid membranes in a watery matrix? a. Lipids are able to dissolve in water because they are polar, too. b. The lipids form a bilayer micelle that hides the hydrophobic parts of the lipid. c. There are organic molecules that protect the lipid membrane from water. d. The lipids don’t have to be attracted to water in order to be present in a watery matrix.

Answer: b. Lipids form a lipid bilayer micelle that hides the hydrophobic parts of the lipid from its more hydrophilic parts (which are exposed to water).

10. What is the main bonding type important in water-based reactions? a. Covalent bonding b. Van der Waals bonding c. Hydrophobic bonding d. Hydrogen bonding Answer: d. Hydrogen bonding is the most important aspect of bonding in water-based reactions in human biochemistry.