Chapter 2 Anatomy and Physiology

What are 2 ways the concentration of solute particles dissolved in solvents are expressed?

(1) In the first way, the percent of solute is calculated by weight per volume of solution. For example, a 10% solution of sodium chloride can be made by dissolving 10 g of sodium chloride into enough water to make 100 mL of solution. (2) For the second way, the number of particles in a solution is expressed as a concentration in osmoles. A particle can be an atom, an ion, or a molecule. An osmole (Osm) is Avogadro's number of particles of a substance in 1 kilogram (kg) of water. The osmolality of a solution reflects the number, not the type, of particles in a solution.

What are the two mechanisms that allow the formation of a wide variety of molecules?

(1) variation in the length of carbon chains and (2) the combination of the atoms involved. For example, some protein molecules have thousands of Caron atoms bound by covalent bonds, to one another or to other atoms, such as nitrogen, sulfur, hydrogen, and oxygen.

FIGURE 2.20 Phospholipids

(a) A molecular model of a phospholipid. The phosphate-containing region usually includes a nitrogen. The bent carbon chain indicates a kink from a double covalent bond. (b) A simplified depiction of a phospholipid.

FIGURE 2.19 Saturated and Unsaturated Fatty Acids

(a) A saturated fatty acid contains no double bonds between the carbons. An example is palmitic acid.

FIGURE 2.26 Components of Nucleotides

(a) Deoxyribose sugar, which forms nucleotides used in DNA production.

FIGURE 2.17 Carbohydrates

(a) Sucrose, a disaccharide, forms by a dehydration reaction involving glucose and fructose (monosaccharides). (b) Glycogen is a polysaccharide formed by combining many glucose molecules. (c) The transmission electron micrograph shows glycogen granules in a liver cell.

FIGURE 2.19 Saturated and Unsaturated Fatty Acids

(b) An unsaturated fatty acid has double bonds between the carbons. An example is linolenic acid, which has three double bonds.

FIGURE 2.26 Components of Nucleotides

(b) Ribose sugar, which forms nucleotides used in RNA production. Note that deoxyribose is ribose minus an oxygen atom.

FIGURE 2.26 Components of Nucleotides

(c) A deoxyribonucleotide consist of deoxyribose, a nitrogenous base, and a phosphate group.

What is a milliosmole?

1/1000 of an osmole. Most body fluids have a concentration of about 300 mOsm and contain many different ions and molecules.

When the pH increases or decreases by 1 how does this influence the H+ concentration?

10 fold. A change in the pH of a solution by 1 pH unit represents a 10-fold change in the H+ concentration. For example, a solution of pH 6 has a H+ concentration 10 times greater than a solution of pH 7 and 100 times greater than a solution of pH 8.

The atomic number of potassium is 19, and the mass number is 39. How many protons, neutrons, and electrons are in an atom of potassium?

19 protons 19 electrons 20 neutrons.

How many electrons do each shell hold?

1st shell holds 2 electrons 2nd shell holds 8 electrons 3rd shell holds 18 electrons 4th shell holds 32

What monosaccharides are most important to humans?

5 and 6-carbon sugars. Common 6-carbon sugars, such as glucose, fructose, and galactose. Important 5-carbon sugars include ribose and deoxyribose respectively.

what is deoxyribose?

5 carbon sugar for DNA.

What is ribose?

5 carbon sugar of ribose.

What is Avogadro's number? How is it related to a mole and molar mass?

6.022 x 10^23 Avogadro's number is equal to 1 mole. The mass of 1 mole of a substance expressed in grams is called the molar mass.

What is the normal pH range for human blood?

7.35 to 7.45

What percent does the nucleus account for the atom's mass?

99.97 % of an atom's mass but only 1 ten-trillionth of its volume.

What does a carboxyl group consist of?

A carboxyl group consists of both an oxygen atom and a hydroxyl group attached to a carbon atom:

Using the terms reactant and product, describe what occurs in a chemical reaction.

A chemical reaction occurs when atoms, ions, molecules, or compounds interact either to form or to break chemical bonds. The substances that enter into a chemical reaction are called reactants, and the substances that result from the chemical reaction are called products.

What is a cofactor?

A cofactor can be an ion, such as magnesium or zinc, or an organic molecule.

What is an ionic bond?

A complete transfer of electrons between two atoms results in separate positively charged and negatively charged ions. Example: Na+Cl- Sodium chloride

What is a conjugate acid-base pair?

A conjugate base is what remains of an acid after the H+ (proton) is lost. A conjugate acid is formed when a H+ is transferred to the conjugate base. Two substances related in this way are a conjugate acid-base pair.

What is a decomposition reaction?

A decomposition reaction is the reverse of a synthesis reaction-a larger reactant is chemically broken down into two or more smaller products.

FIGURE 2.23 Peptide Bond

A dehydration reaction between two amino acids forms a dipeptide and a water molecule. The covalent bond between the amino acids is called a peptide bond.

What is a fatty acid?

A fatty acid is a straight chain of carbon atoms with a carboxyl group attached at one end.

What is the difference between a saturated fat and an unsaturated fat? What is a trans fat?

A fatty acid is saturated if it contains only single covalent bonds between the carbon atoms. Sources of saturated fats include beef, pork, whole milk, cheese, butter, eggs, coconut oil, and palm oil. The carbon chain is unsaturated if it has one or more double covalent bonds between carbon atoms. The double covalent bond introduces a kink into the carbon chain, which tends to keep them liquid at room temperature. Trans fats are unsaturated fats that have been chemically altered by the addition of hydrogen. The process makes the fats more saturated and hence more solid and stable (longer shelf life). However, the double covalent bonds that do not become saturated are changed from the usual cis configuration (H on the same side of the double bond) to a trans configuration (H on different sides). This change in structure makes the consumption of trans fats an even greater factor than saturated fats in the risk for cardiovascular disease.

Differentiate between a molecule and a compound.

A molecule is composed of two or more atoms chemically combined to form a structure that behaves as an independent unit. A compound is a substance resulting from the chemical combination of two or more different types of atoms.

Distinguish between a molecule and a compound. Give an example of each. Are all molecules compounds? Are all compounds molecules?

A molecule is composed of two or more atoms chemically combined to form a structure that behaves as an independent unit. Example: Sometimes the atoms that combine are of the same type, such as two hydrogen atoms combining to form a hydrogen molecule. However, more typically, a molecule consists of two or more different types of atoms, such as two hydrogen atoms and an oxygen atom combing to form water. Thus, a glass of water consists of a collection of individual water molecules positioned next to one another. A compound is a substance resulting from the chemical combination of two or more different types atoms. Water is a molecule that is also a compound because it is a combination of two different atoms, hydrogen and oxygen. But not all molecules are compounds. For example, a hydrogen molecule is not a compound because it does not consist of different types of atoms.

Describe the structure of a phospholipid. Which end of the molecule is hydrophilic? Explain why.

A phospholipid is polar at the end of the molecule to which the phosphate is bound and non polar at the other end. The polar end of the molecule is attracted to water and is said to be hydrophilic. The non polar end is repelled by water and is said to be hydrophobic. Phospholipids are important structural components of the membrane of cells. The presence of phospholipids with unsaturated fatty acids contributes to the fluidity of the plasma membrane.

What is a polypeptide bond?

A polypeptide bond is many amino acids bound together by peptide bonds.

How are salts related to acids and bases?

A salt is a compound consisting of a cation other than H+ and an anion other than OH-. Salts are formed by the interaction of an acid and a base in which the H+ of the acid are replaced by the positive ions of the base. For example, in a solution in which hydrochloric acid (HCl) reacts with the base sodium hydroxide (NaOH), the salt sodium chloride (NaCl) is formed. HCl + NaOH --> NaCl + H2O Typically, when salts such as sodium chloride dissociate in water, they from positively and negatively charged ions.

What is salt?

A salt is a compound consisting of a cation other than H+ and an anion other than OH-. Salts are formed by the interaction of an acid and a base in which the H+ of the acid are replaced by the positive ions of the base. For example, in a solution in which hydrochloric acid (HCl) reacts with the base sodium hydroxide (NaOH), the salt sodium chloride (NaCl) is formed: HCl + NaOH --> NaCl + H2O Typically, when salts such as sodium chloride dissociate in water, they form positively and negatively charged ions.

What is an ionic bond?

A sodium atom (Na) loses an electron to become smaller, positively charged ion, and a chlorine atom (CL) gains an electron to become larger, negatively charged ion. The attraction between the oppositely charged ions results in ionic bonding and the formation of sodium chloride.

Describe how an ionic bond is formed. What are a cation and anion?

A sodium atom loses an electron to become a smaller, positively charged ion, and a chlorine atom (Cl) gains an electron to become a larger, negatively charged ion. The attraction between the oppositely charged ions results in ionic bonding and the formation of sodium chloride. Cation is a positive charged ion formed when electrons are donated Anion is a negative charged ion formed when electrons are received.

Where is a substantial amount of glucose stored?

A substantial amount of the glucose that is metabolized to produce energy for muscle contraction during exercise is stored in the form of glycogen in the cells of the liver and skeletal muscles.

FIGURE 2.18 Triglyceride

A triglyceride is produced from a backbone of one glycerol molecule and three fatty acid molecules. One water molecule (H2O) is given off for each covalent bond formed between a fatty acid and glycerol.

What is a tripeptide bond?

A tripeptide is three amino acids bound together by peptide bonds.

Use ATP and ADP to illustrate the release or input of energy in chemical reactions.

ATP --> ADP + Pi + Energy ADP + Pi + Energy --> ATP

What is an example of a synthesis reaction?

ATP, which is composed of Aden-osine and three phosphate groups, is synthesized from adenosine diphosphate (ADP), which has two phosphate groups, and an inorganic phosphate (H2PO4) that is often symbolized as Pi: A-P-P + Pi --> A-P-P-P

Whats an example of a synthesis reaction?

ATP, which is composed of adenosine and three phosphate groups, is synthesize from adenosine diphosphate (ADP), which has two phosphate groups, and an inorganic phosphate (H2PO4) that is often symbolized as Pi: A-P-P + Pi --> A-P-P-P

Compare the lock-and-key and the induced fit models of enzyme activity. What determines the active site of an enzyme? State the difference between a cofactor and a coenzyme.

According to the lock-and-key model of enzyme action, a reaction occurs when the reactants (key) bind to the active site (lock) on the enzyme. This view of enzymes and reactants as rigid structures fitting together has been modified by the induced fit model, in which the enzyme is able to change shape slightly and better fit the reactants.

How do proteins contract?

Actin and myosin in muscle are responsible for muscle contraction.

Define activation energy, catalyst, and enzymes then explain how they affect the rate of chemical reactions.

Activation energy is the amount of energy needed to trigger a chemical reaction. Catalyst are substances that increase the rate of chemical reactions without being permanently changed or depleted themselves. Enzymes increase the rate of chemical reactions by lowering activation energy necessary for the reaction to begin.

Give an example of complementary base pairs.

Adenine and thymine are complementary base pairs because the structure of these bases allows two hydrogen bonds to form between them.

Describe the structure of ATP. Where does the energy to synthesize ATP come from? What is the energy stored in ATP used for?

Adenosine triphosphate is an especially important molecule for storing and providing energy in all living organisms. It consist of adenosine (the sugar ribose with the nitrogenous base adenine) and three phosphate groups. The close proximity of the three negatively charged phosphate groups make ATP a very unstable molecule. As a result, cleavage of the phosphate bonds releases a large amount of energy; hence, the second and third phosphate bonds are referred to as "high-energy" bonds. In particular, the potential energy stored in the covalent bond between the second and third phosphate groups of ATP is important to living organisms because it provides energy used nearly all of the chemical reaction within cells. Removal of the third phosphate generates adenosine diphosphate (ADP), which has only two phosphate groups.

What is adhesion?

Adhesion is the same attractive force of hydrogen bonds of water that will also attract other molecules. An example of adhesion is the surface tension that draws water across a glass plate and holds a bead of water to the skin before it falls to the ground. The combination of cohesion and adhesion helps hold cells together and move fluids through the body.

How do lipids provide protection?

Adipose tissue surrounds and pads organs.

How do lipids provide insulation?

Adipose tissue under the skin prevents heat loss. Myelin surrounds nerve cells and electrically insulates the cells from one another.

What does adipose tissue provide?

Adipose tissues also provide protection by surrounding and padding organs, and under-the-skin adipose acts as an insulator to prevent heat loss.

Hydroxyl

Alcohols contain a hydroxyl group, which is polar and hydrophilic. Hydroxyl groups greatly increase the solubility of molecules in water.

FIGURE 2.22 Amino Acids

All amino acids have a common structure of an amine group, a carboxyl group, and an R side chain that gives each amino acid its unique properties. The amino acid glycine, tyrosine, phenylalanine, and aspartic acid are shown as representative examples.

Define matter, mass, and weight.

All living things and nonliving things are composed of matter, which is anything that occupies space and has mass. Mass is the amount of matter in an object. Weight is the gravitational force action on an object of a given mass.

what is metabolism?

All of the anabolic and catabolic reactions in the body are collectively defined as metabolism.

What is a protein?

All proteins are organic macromolecules that contain carbon, hydrogen, oxygen, and nitrogen bound together by covalent bonds. Most proteins also contain some sulfur. In addition, some proteins contain small amounts of phosphorus, iron, and iodine. The molecular mass of proteins can be very large. For the purpose of comparison, the molecular mass of water is approximately 18, sodium chloride 58, and glucose 180, but the molecular mass of proteins ranges from approximately 1000 to several million. Proteins regulate body processes, act as a transportation system, provide protection, help muscles contract, and provide structure and energy.

What is a protein?

All proteins are organic molecules that contain carbon, hydrogen, oxygen, and nitrogen bound together by covalent bonds. Most proteins also contain some sulfur. In addition, some proteins contain small amount of phosphorus, iron, and iodine.

Amino

Amines have an amino group, which is less hydrophilic than carboxyl groups. Amines can act as a base by accepting a hydrogen ion. All amino acids have an amine group at one end. At physiological pH, the amino acid amine group is predominantly positively charged.

What is an atom?

An atom (atomos, indivisible) is the smallest particle of an element that has the chemical characteristics of the element. An element is composed of atoms of only one kind.

What is an element?

An element is the simplest type of matter, having unique chemical properties.

Differentiate between element and atom. What four elements are found the greatest abundance in the human body?

An element is the simplest type of matter, having unique chemical properties. Atoms are individual particles that are involved in elements. Hydrogen= 9.5 Carbon = 18.5 Nitrogen = 3.3 Oxygen = 65.0

Nonpolar Covalent Bond

An equal sharing of electrons between two atoms results in an even charge distribution among the atoms of the molecule. H | H-- C -- H | H

Give an example of hydrolysis reactions.

An example of a decomposition reaction is the breakdown of a dissaccharide (a type of carbohydrate) into glucose molecules. Note that this reaction requires that water be spit into two parts and that each part be contributed to one of the new glucose molecules. Reactions that use water in this manner are called hydrolysis reactions.

Whats a gram?

An object with 1/1000 the mass of a kilogram has a mass of 1 gram.

What is an osmole (Osm)?

An osmole (Osm) is Avogadro's number of particles of a substance in 1 kilogram (kg) of water.

What is a Polar Covalent Bond?

An unequal sharing of electrons between two atoms results in a slightly positive charge on one side of the molecule and a slightly negative charge on the other side of the molecule. Example: Water H \ O / H

Distinguish between chemical reactions that release energy and those that take in energy.

Anabolism, think Arnold swartanegger, take in energy to carry out a function Catabolism is the opposite, releases energy to carry out a function.

How do proteins protect?

Antibodies protect against microorganisms and other foreign substances.

What are complementary base pairs?

Are bases held together by hydrogen bonds.

Define atomic number, mass number, isotope, atomic mass, and mole.

Atomic number is the number of protons in a atom. Mass number is the number of protons plus the number of neutrons in a atom. Isotopes are two atoms that have the same amount of protons but different amount of neutrons. Atomic mass is the average mass of is naturally occurring isotopes, taking into account the relative abundance of each isotope. A mole of a substance contains Avogadr's number of entities, such as atoms, ions, or molecules.

Models

Atoms are shown as different-sized and different-colored spheres.

What happens if atoms have the same electronegativity?

Atoms that have the same electronegativities, such as two carbon atoms, will equally share electrons.

What is a chemical bond?

Attraction of electrons from two different elements.

Why is glycogen an important energy-storage molecule?

Because glucose can be metabolized rapidly and the resulting energy can used by cells, glycogen is an important energy-storage molecule.

How are ionic bonds formed?

Because oppositely charged ions are attracted to each other, cations and anions tend to remain close together. Thus, an ionic bond forms when electrons are transferred between atoms, creating oppositely charged ions. For example. Na+ and Cl- are held together by ionic bonding to form an array of ions called sodium chloride (NaCl), or table salt. Some ions commonly found in the body are listed in table 2.2.

Why are subatomic particles useful?

Because they allows us to see things that are not visible to the human eye.

How is blood glucose tightly regulated?

Blood glucose levels are tightly regulated by insulin and other hormones. In people with diabetes, the body is unable to regulate glucose levels properly. Diabetics need to monitor their blood glucose carefully to minimize the deleterious effects of this disease.

Give an example of a monosaccharide.

Blood glucose levels are tightly regulated by insulin and other hormones. In people with diabetes, the body is unable to regulate glucose levels properly. Diabetics need to monitor their blood glucose carefully to minimize the deleterious effects of this disease.

What is a buffer, and why are buffers important in the body?

Buffers are chemicals that resist the change in pH in any direction. Buffers help maintain the homeostasis in the body when it comes to pH.

Which complementary base pair, G-C or A-T, would be hardest to break apart when a double-stranded DNA helix unwinds during cellular processes?

C-G because there are three hydrogen bonds present versus two.

Describe the structural organization and major functions of carbohydrates, lipids, proteins and nucleic acids.

Carbohydrates are organic molecules composed primarily of Carbon, hydrogen, and oxygen atoms and range in size from small to very large. In most carbohydrates, there are approximately two hydrogen atoms and one oxygen atom for each carbon atom. Note that this two-to-one ratio is the same as in water (H2O). The molecules are called carbohydrates because carbon (carbo) atoms are combined with the same atoms that form water (hydrated). The large number of oxygen atoms in carbohydrates makes them relatively polar molecules. Consequently, they are soluble in polar solvent, such as water. Carbohydrates are important parts of other organic molecules, and they can be broken down to provide the energy necessary for life. Undigested carbohydrates also provide bulk in feces, which helps maintain the normal function and health of the digestive tract. Lipids are major group of organic molecules that are relatively insoluble in water. Like carbohydrates, they are composed principally of carbon, hydrogen, and oxygen but lipids have a lower ratio of oxygen to carbon than do carbohydrates. This makes them less polar. Consequently, lipids can be readily dissolved in non polar organic solvents, such as alcohol or acetone, but they are relatively insoluble in water. Some lipids also contain small amounts of other elements such as phosphorus and nitrogen, which can aid solubility in water. Lipids have many important functions in the body. They provide protection and insulation, help regulate many physiological processes, and form plasma membranes. In addition, lipids are major energy-storage molecules and can be broken down and used as a source of energy. The major classes of lipids are fats, phospholipids, eicosanoids, steroids, and fat-soluble vitamins. All proteins are organic macromolecules that contain carbon, hydrogen, oxygen, and nitrogen bound together by covalent bonds. Most proteins also contain some sulfur. In addition, some proteins contain small amounts of phosphorus, iron, and iodine. The molecular mass of proteins can be very large. For the purpose of comparison, the molecular mass of water is approximately 18, sodium chloride 58, and glucose 180, but the molecular mass of proteins ranges from approximately 1000 to several million. Proteins regulate body processes, act as a transportation system, provide protection, help muscles contract, and provide structure and energy. The nucleic acids are large molecules composed of carbon, hydrogen, oxygen, nitrogen, and phosphorus. Nucleic acids help form DNA and RNA which is used to make more DNA.

What are carbohydrates?

Carbohydrates are organic molecules composed primarily of carbon, hydrogen, and oxygen atoms and range in size from small to very large.

What are the major roles of carbohydrates in the body?

Carbohydrates have three major roles in the body: (1) they are parts of other organic molecules; (2) they are broken down to provide energy; and (3) when undigested they provide bulk in feces.

What do nitrogenous bases consist of?

Carbon and nitrogen atoms organized into rings. They are bases because the nitrogen atoms tend to take up H+ from solution. The nitrogenous bases are cytosine, thymine, and uracil, which have a single ring, and guanine and adenine, which have two rings each.

What does carbon atoms bound together constitute?

Carbon atoms bound together by covalent bonds constitute the "backbone" of many large molecules.

What is Caron dioxide and how is it important to the body?

Carbon dioxide consists of one carbon atom bound to two oxygen atoms. Each oxygen atom is bound to the carbon atom by a double covalent bond. Carbon dioxide is produced when organic molecules, such as glucose, are metabolized within the cells of the body. Much of the energy stored in the covalent bonds of glucose is transferred to other organic molecules when glucose is broken down and carbon dioxide is released. Once carbon dioxide is produced, it is eliminated from the cell as a metabolic by-product, transferred to the lungs by the blood, and exhaled during respiration. If carbon dioxide is allowed to accumulate within cells, it becomes toxic.

What role does carbon play in the body?

Carbon plays an especially important role in the chemistry of the body, due in part to its propensity to form covalent bonds with itself and other molecules.

What does Carbon's ability to form covalent bonds with other atoms make possible?

Carbon's ability to form covalent bonds with other atoms makes possible the formation of the large, diverse, complicated molecules necessary for life.

What are some examples of conjugate acid-base pair and how are they formed?

Carbonic acid and bicarbonate Bicarbonate is formed by the dissociation of carbonic acid (H2CO3)

Why is carbon such a versatile element.

Carbons ability to form covalent bonds with other atoms makes possible the formation of the large, diverse, complicated molecules necessary for life. Carbon atoms bound together by covalent bonds constitute the "backbone" of many large molecule.

Carboxyl

Carboxylic acids have a carboxyl group, which is hydrophilic and can act as an acid by donating a hydrogen ion. All amino acids have a carboxyl group at one end. At physiological pH, the amino acid carboxyl group is predominantly negatively charged.

Whats the difference between an enzyme and a catalyst?

Catalyst are substances that increase or decrease the rate of a chemical reaction but remain unchanged. Enzymes are proteins that increase rate of chemical reactions converting substrate into product.

What is an electrolyte?

Cation or anion in solution that conducts an electric current.

What are electrolytes?

Cations and anions that dissociate in water are sometimes called electrolytes because they have the capacity to conduct an electric current, which is the flow of charged particles.

What is the role of carbohydrates bulk?

Cellulose forms bulk in the feces.

Why is cellulose important?

Cellulose is an important structural component of plant cell walls.

What is cellulose and what is its function?

Cellulose is an important structural component of plant cell walls. When humans ingest plants, the starch can be broken down and used as an energy source. Humans, however, do not have the digestive enzymes necessary to break down cellulose. Cellulose is eliminated in the feces, where it provides bulk.

What are the four ways to picture a molecule?

Chemical Formula Electron-Dot Formula Bond-Line Formula Models

What is a covalent bond?

Chemical bond characterized by the sharing of electrons.

What are oxidation-reduction reactions?

Chemical reactions that result from the exchange of electrons between the reactants are called oxidation-reduction reactions.

Why is cholesterol an important steroid?

Cholesterol is an especially important steroid because other steroid molecules are synthesized from it. Steroids derive from cholesterol include bile salts, which increase fat absorption in the intestines, and the reproductive hormones estrogen, progesterone, and testosterone.

What is prostaglandin?

Class of physiologically active substances present in many tissues; among its effect are vasodilation, stimulation and contraction of uterine smooth muscle and the promotion of inflammation and pain.

How is the presence of cellulose important?

Clinically, the presence of cellulose (fiber) in our diet is important for regularity of bowel movements and has been reported to help produce cholesterol and control blood sugar levels.

What is coenzyme?

Cofactors that are organic molecules, such as certain vitamins, may be referred to as coenzymes.

Describe how the properties of water contribute to its physiological functions.

Cohesion is the attraction of water to another water molecule. Examples of cohesions is when beads of water form on the skin. Adhesion is the same attractive force of hydrogen bonds of water that will also attract other molecules. An example of adhesion holds a bead of water to the skin before it falls to the ground. The combination of cohesion and adhesion helps hold cells together and move fluids through the body. Stabilizing Body temperature. Water tend to resist large temperature fluctuations because it can absorb large amounts of heat and remain at a fairly stable temperature. Protection Water protects the body by acting as a lubricant and a cushion for organs. Lubrication reduces damage from friction. Chemical Reactions Many of the chemical reactions necessary for life do no take place unless the reacting molecules are dissolved in water. Mixing medium Water's ability to mix with other substances enables it to act as a medium for transport, moving substances from one part of the body to another. Body fluids, such as plasma, trnasport nutrients, gases, waste products, and a variety of molecules involved in regulating body functions.

What two properties of water are the result of hydrogen bonding, and how are the two properties different?

Cohesion is water to water Adhesion is water to other molecules. Cohesion is the attraction of water to another water molecule. Adhesion is the same attractive force of hydrogen bonds of water that will also attract other molecules.

How do proteins structure?

Collagen fibers form a structural framework in many parts of the body. Keratin adds strength to skin, hair, and nails.

Name the complementary base pairs in DNA and RNA.

Complementary base pairs are bases held together by hydrogen bonds. Adenine and thymine are complementary base pairs because the structure of these bases allows two hydrogen bonds to form between them. Cytosine and guanine are complementary base pairs because the structure of theses bases allows three hydrogen bonds to form between them. The two strands of a DNA molecule are said to be complementary. If the sequence of bases in one DNA strand is known, the sequence of bases in the other strand can be predicted because of complementary base pairing. DNA: A-T, C-G,

What can lipids be dissolved in?

Consequently, lipids can be readily dissolved in non polar organic solvents, such as alcohol or acetone, but they are relatively insoluble in water.

What bonds are the strongest and what bonds are the weakest?

Covalent are the strongest Ionic is weaker than covalent Hydrogen is the weakest

What is a peptide bond?

Covalent bonds formed between amino acid molecules using protein synthesis are called peptide bonds.

Why is Cyanide poisoning harmful?

Cyanide can be lethal because it interferes with ATP production in mitochondria. Without sufficient ATP, cells die because there is inadequate energy for anabolic chemical reactions and other energy-requiring processes. The heart and brain are especially susceptible to cyanide poisoning due to their relatively high energy requirements.

Give an example of complementary base pairs.

Cytosine and guanine are complementary base pairs because the structure of these bases allows three hydrogen bonds to form between them.

What is the double helix?

DNA has two strands of nucleotides joined together to form a twisted, ladder like structure called a double helix.

DNA is like a twisted ladder. What forms the sides of the ladder? The rungs?

DNA has two strands of nucleotides joined together to form a twisted, ladder like structure called a double helix. The sides of the ladder are formed by covalent bonds between the deoxyribose molecules and phosphate groups of adjacent nucleotides. The rungs of the ladder are formed by the nitrogenous bases of the nucleotides of one side connected to the nitrogenous basses on the other side by hydrogen bonds. Each nucleotide of DNA contains one of the nitrogenous bases: adenine, thymine, cytosine, and guanine.

PROCESS FIGURE 2.28 Structure of DNA

DNA is assembled from nucleotide building blocks held together by phosphate bonds. DNA forms a double-stranded helix that is held together by hydrogen bonds between the nucleotides of complementary strands.

Illustrate what occurs in dehydration and hydrolysis reactions.

Dehydration is a chemical reaction that releases water to form a product. Hydrolysis is a chemical reaction that uses water to form a product.

Name two types of nucleic acids, and state their functions.

Deoxyribonucleic acid is the genetical material of cells, and copies of DNA are transferred from one generation of cells to the next generation. DNA contains the information that determines the structure of proteins. Ribonucleic acid (RNA) is structurally related to DNA, and three types of RNA also play important roles in protein synthesis.

What is sucrose?

Disaccharide composed of glucose and fructose; table sugar. Glucose + Fructose = water and Sucrose

How can Dissacharides and polysaccharides be used as energy?

Disaccharides (sucrose, lactose, maltose) and polysaccharides (starch, glycogen) must be broken down to monosaccharides before they can be used for energy.

What are disaccharides and polysaccharides, and what type of reaction is used to make them?

Dissacharides are composed of two monosaccharides bound together through a dehydration reaction. For example, glucose and fructose combine to form a disaccharide called sucrose (table sugar) plus a molecule of water. In addition to sucrose, two other disaccharides important to humans are lactose and maltose. Lactose, or milk sugar, is glucose combined with galactose. Maltose, or malt sugar, is two glucose molecules joined together.

What is a solute?

Dissolved substance in a solution

What is an amino acid made of?

Each amino acid has an amine group (--NH2), a carboxyl group (--COOH), a hydrogen atom, a side chain designated by the symbol R attache to the same carbon atom.

What are the nucleotides of DNA?

Each nucleotide of DNA contains one of the nitrogenous bases: adenine, thymine, cytosine, or guanine.

What are eicosanoids important for?

Eicosanoids are made in most cells and are important regulatory molecules. Among their numerous effects is their role in the response of tissues to injuries.

Explain the difference between electrolytes and non electrolytes. Classify each of the following water solutions as an electrolyte or a non electrolyte: potassium iodide, sucrose, magnesium bromide and lactose.

Electrolytes produce electricity Non electrolytes do not produce electricity. Potassium iodide is an electrolyte Sucrose is a nonelectrolyte Lactose is a non electrolyte Magnesium bromide is an electrolyte.

FIGURE 2.5 Relationship Between Electronegativity and Chemical Bonding

Electronegativity is a measure of how much an atom attracts electrons from another atom to form a chemical bond. Covalent bonds are formed by the sharing of electrons between atoms that have the same electronegativity (nonpolar covalent bond, e.g., H2) or a relatively small difference in electronegativities (polar covalent bond, e.g., H2O). Ionic bonds are formed by the transfer of electrons between two atoms that have very different electronegativities. (e.g., NaCl)

What determines whether an electron is transferred or shared between two atoms?

Electronegativity is the ability of an atom's nucleus to attract electrons. In general, atoms that lack only 1 or 2 electrons from having an octet in their valence shell have a strong electronegativity.

Distinguish between elements and atoms, and state the four most abundant elements in the body.

Elements are composed of the same atoms that come together to form the element. Atoms are small particles that make up elements and other things. Hydrogen Carbon Nitrogen Oxygen

Define energy. How are potential and kinetic energies different from each other?

Energy is the capacity to do work--that is, to move matter. Energy can be subdivided into potential energy and kinetic energy. Potential energy is stored energy that could do work but is not doing so. Kinetic energy is the form of energy that is actually doing work and moving matter.

What is a protease?

Enzyme that breaks down proteins.

Explain how enzymes work.

Enzymes bind to the active site and change shape to lower the activation energy needed to carry out a chemical reaction.

How do proteins regulate?

Enzymes control chemical reactions. Hormones regulate many physiological processes; for example, insulin affects glucose transport into cells.

Ester

Esters are structures with an ester group, which is less hydrophilic than hydroxyl or carboxyl groups. Triglycerids and dietary fats are esters. Other types of esters include the volatile compound in perfumes.

What are some examples of inorganic molecules in human anatomy and physiology?

Examples include (1) oxygen we breathe, (2) carbon dioxide we exhale, (3) water essential for life, (4) calcium phosphate that makes up turbines, and (5) metals required for protein functions, ranging form iron in blood gas transport to zinc in alcohol detoxification.

How are fat-soluble vitamins beneficial?

Fat-soluble vitamins perform a variety of functions. Vitamin A forms retinol, which is necessary for seeing in the dark; active vitamin D promotes calcium uptake by the small intestine; vitamin E promotes wound healing; and vitamin K is necessary for the synthesis of proteins responsible for blood clotting.

What are fats?

Fats are a major type of lipid.

What is saturated?

Fatty acid in which the carbon chain contains only single bonds between carbon atoms.

What are polyunsaturated fats?

Fatty acid that contains two or more double covalent bonds between its carbon atoms.

How do fatty acids differ?

Fatty acids differ from one another according to the length and the degree of saturation of their carbon chains.

Why do females have less water?

Females have a lower percentage of water than males because they typically have more body fat, which is relatively free of water.

What are the three important points that can be made about chemical reaction?

First, in some reactions, less complex reactants are combined to form a larger, more complex product. An example is the synthesis of the complex proteins of the human body from amino acid "building blocks" obtained from food. Second, in other reactions, a reactant can be broken down, or decomposed, into simpler, less complex products. An example is the breakdown of carbohydrate molecules into glucose molecules. Third, atoms are generally associated with other atoms through chemical bonding or intermolecular forces; therefore, to synthesize new products or break down reactants, it is necessary to change the relationship between atoms.

Whats an example of a strong acid dissociating water?

For example, HCl is a strong acid because it completely dissociates in water: HCl-> H+ + Cl- Not easily reversible

What 's an example of measuring the amount of particles in a solution?

For example, a 1 Osm glucose solution and a 1 Osm NaCl solution both contain Avogadro's number of particles per kg of water. The glucose solution has 1.0 Osm of glucose molecules, whereas the NaCl solution has 0.5 Osm of Na+ and 0.5 Osm of Cl- because NaCl dissociates into Na+. and Cl- in water.

How is sucrose formed?

For example, glucose and fructose combine to form a disaccharide called sucrose plus a molecule of water.

Whats an example of difference in electronegativity?

For example, oxygen has a relatively strong electronegativity unequally from other atoms that have weaker electronegativity.

How are elements that are dangerous or toxic to humans become useful compounds?

For example, sodium is very explosive when placed in water, and chlorine is a strong disinfectant in solutions, such as bleach and swimming pool water. Chlorine is so toxic that it was used as a poison gas in World War 1, yet, when combined, sodium and chloride form the relatively safe and nonexplosive compound table salt.

Give an example of hydrogen bonding.

For example, the positively charged hydrogen atoms of a water molecule form hydrogen bonds with the negatively charged oxygen atoms of other water molecules. These hydrogen bods are essential for the unique properties of water.

What's an example of a weak acid that partially dissociates in water?

For example, when acetic acid (CH3COOH) is dissolved in water, some of it dissociates, but some it remains in the undissociated form. An equilibrium is established between the ions and the undissociated weak acid: CH3COOH = CH3COO- + H+ Easily reversible

Give an example of a isomer.

Fructose is a structural isomer of glucose because it has identical chemical groups bonded in a different arrangement in the molecule (red shedding).

Give an example of a stereoisomer.

Galactose is a stereoisomer of glucose because it has exactly the same groups bonded to each carbon atom but located in a different three-dimensional orientation (yellow shading)

Define gene, and explain how genes determine the structures and functions of cells.

Gene-functional unit of heredity. Each gene occupies a specific place, or locus, on a chromosome; it is capable of reproducing itself exactly at each cell division; it often is capable of directing the formation of an enzyme or another protein. Genes determine the type of sequence of amino acids in protein molecules. Because enzymes are proteins, DNA structure determines the rate and type of chemical reactions that occur in cells by controlling enzyme structure. Therefore, the information contained in DNA ultimately defines all cellular activities. Other proteins that are coded by DNA, such as collagen, determine many of the structural features of humans.

How is Glucose or blood sugar a major nutrient for most cells of the body?

Glucose, or blood sugar, is the major carbohydrate in the blood and a major nutrient for most cells of the body.

List the 5- and 6-carbon sugars that are important to humans.

Glucose, or blood sugar, is the major carbohydrate in the blood and a major nutrient for most cells of the body. Blood glucose levels are tightly regulated by insulin and other hormones. Fructose and galactose are also important dietary nutrients. Important 5-carbon sugars include ribose and deoxyribose, which are components of ribonucleic acid (RNA) and deoxyribonucleic acid (DNA), respectively.

How are glycerides described?

Glycerides can be described according to the number and kinds of fatty acids that combine with glycerol through dehydration reaction.

What is a glycerol?

Glycerol is a 3-carbon molecule with a hydroxyl group attached to each carbon atom.

Where is Glycogen important?

Glycogen is an important energy-storage molecule in muscles and in the liver.

What is Glycogen and what is its function?

Glycogen is the main storage form of glucose in humans.

Which carbohydrates are used for energy? What is the function of starch and cellulose in plants? What is the function of glycogen and cellulose in animals?

Glycogen, or animal starch, is a multi branched polysaccharide composed of many glucose molecules. Glycogen is the main storage form of glucose in humans. Because glucose can be metabolized rapidly and the resulting energy can be used by cells, glycogen is an important energy-storage molecule. Plants use starch as an energy-storage molecule in the same way that animals use glycogen. Cellulose is an important structural component of plant cell walls. When humans ingest plants, the starch can be broken down and used as an energy source.

How do proteins transport?

Hemoglobin transport oxygen and carbon dioxide in the blood. Plasma proteins transport many substances in the blood. Proteins in plasma membranes control the movement of materials into and out of the cell.

What does chemically reactive mean?

However, if an atom's valence shell is not full, the atom is chemically reactive and forms chemical bonds with other atoms to achieve a full valence shell, called an octet.

What are the functions of oxygen and carbon dioxide in living systems?

Humans require oxygen in the final step of a series of reactions that extract energy from food molecules. Carbon dioxide is produced when organic molecules, such as glucose, are metabolized within the cells of the body. Much energy stored in the covalent bonds of glucose is transferred to other organic molecules when glucose is broken down and carbon dioxide is released. Once carbon dioxide is produced, it is eliminated from the cell as a metabolic by-product, transferred to the lungs by the blood, and exhaled during respiration. If Caron dioxide is allowed to accumulate within cells, it becomes toxic.

Compare the roles of oxygen and carbon dioxide in the body.

Humans require oxygen in the final step of a series of reactions that extract energy from food molecules. Carbon dioxide is produced when organic molecules, such as glucose, are metabolized within the cells of the body. Much of the energy stored in the covalent bonds of glucose is transferred to other organic molecules when glucose is broken down and carbon dioxide is released. Once carbon dioxide is produced, it is eliminated from the cell as a metabolic by-product, transferred to the lungs by the blood, and exhaled during respiration. If carbon dioxide is allowed to accumulate within cells, it becomes toxic.

What is a hydrogen bond?

Hydrogen atoms bound covalently to either N or O atoms have a small positive charge that is weakly attracted to the small negative charge of other atoms, such as O or N; it can occur within a molecule or between different molecules.

What are some examples of intermolecular bonds?

Hydrogen bonds

What happens to the fat we do not need?

If fat intake exceeds need, excess chemical energy from any source can be stored in the body as adipose tissue for later use.

How are hydrogen bonds formed?

If the positively charged hydrogen of one molecule is attracted to the negatively charged oxygen, nitrogen, or fluorine of another molecule, a hydrogen bond forms.

How are Hydrogen bonds formed?

If the positively charged hydrogen of one molecule is attracted to the negatively charged oxygen, nitrogen, or fluorine of another molecule, a hydrogen bond forms. For example, the positively charged hydrogen atoms of a water molecule form hydrogen bonds with the negatively charged oxygen atoms of other water molecules.

Explain what creates a hydrogen bond, and relate its importance.

If the positively charged hydrogen of one molecule is attracted to the negatively charged oxygen, nitrogen, or fluorine of another molecule, a hydrogen bond forms. Without hydrogen bonds, water would be unable to carry out the normal features it usually does. An important role of hydrogen bonds is to help build the shape of complex molecules. The bonds can occur between different polar parts of a molecule to stabilize the final three-dimensional shape.

What does it mean to be inert?

If the valence shell is full (contains 8 electrons), the atom is inert, that is, it does not form chemical bonds with other atoms.

What are some important steroid molecules?

Important steroid molecules include cholesterol, bile salts, estrogen, progesterone, and testosterone.

How are chemical bonds formed?

In a chemical bond, the fate of the electrons between two atoms depends on the relative difference in electronegativity between the atoms. When electronegativites of two atoms forming a chemical bond are similar, the atoms tend to share, rather than transfer, the electrons. Under these conditions, covalent bonds are formed.

What are oxidation-reduction reactions?

In a reaction when electrons are lost somewhere, electrons are gained elsewhere. When atoms or compounds and molecules come together to carry out a chemical reaction, the reactants lose or gain electrons at the same time. Chemical reactions that result from the exchange of electrons between the reactants are called oxidation-reduction reactions. When sodium and chlorine react to form sodium chloride, the sodium atom loses an electron and the chlorine atom gain an electron. The lose of an electron by an atom is called oxidation, and the gain of an electron is called reduction.

Describe the role of water in dehydration and hydrolysis reactions.

In dehydration reactions water is released to form the product. In hydrolysis water is used to form products.

Why are carbohydrates named what they are?

In most carbohydrates, there are approximately two hydrogen atoms and one oxygen atom for each carbon atom. Note that this two-to-one ratio is the same as in water (H2O). The molecules are called carbohydrates because carbon (carbo) atoms are combined with the same atoms that form water (hydrated).

What is the protein structure determined by?

In summary, protein structure is determined by the following sequence of events. 1. First, by the amino acid sequence (primary structure). 2. Folding and bending of the primary structure into helices and sheets due to hydrogen bonding (secondary structure). 3. This is followed by large-scale folding of the protein that is drive by hydrophilic and hydrophobic interactions and stabilized by disulfide bridges (tertiary structure). 4. The final structure of some proteins is determined by their association with other proteins in multisubunit complexes (quaternary structure).

What effect does increasing temperature or increasing concentration of reactants have on the rate of a chemical reaction?

Increasing temperature increase the speed or how quickly a chemical reaction can be carried out while decreasing the temperature slows the rate of the chemical reaction.

Distinguish between inorganic and organic compounds.

Inorganic chemistry generally deals with substances that do not contain carbon, although a more rigorous definition is the lack of carbon-hydrogen bonds. Organic chemistry is the study of carbon-containing substances, with a few exceptions. For example, carbon monoxide (CO), carbon dioxide (CO2), and bicarbonate ions (HCO3-) are several important inorganic substances that contain carbon but lack C--H bonds.

Whats the difference between inorganic chemistry and organic chemistry?

Inorganic chemistry lacks C-H bonds while organic has C-H bonds.

What is the difference between inorganic and organic chemistry?

Inorganic has no carbon bonds, organic has carbon bonds. Inorganic - no carbon Organic - carbon.

How does Intermolecular force result?

Intermolecular force results from the attraction of the positive end of one polar molecule to the negative end of another polar molecule.

What are intermolecular forces, and how do they create a hydrogen bond?

Intermolecular forces are the weak electrostatic attractions that exist between oppositely charged parts of molecules, or between ions and molecules. There is no exchange of electrons in intermolecular forces. This differs from other chemical bonds. Intermolecular forces are much weaker than the forces producing chemical bonding. Intermolecular forces include hydrogen bonds and the properties of solubility and dissociation.

What is an important reversible reaction in the human body?

Involves carbon dioxide and hydrogen ions. Carbon dioxide (CO2) and water (H2O) combine to form carbonic acid (H2CO3). Cabonic acid then separates by a reversible reaction to form hydrogen ions (H+) and bicarbonate ions(HCO3-) CO2 + H2O = H2CO3 = H+ + HCO3-

What are some examples of chemical bonds?

Ionic Polar Covalent Nonpolar Covalent

Compare and contrast ionic and covalent bonds.

Ionic bonds and covalent bonds are similar because they both form when elements or atoms come together. Ionic bonds form anions and cations because they donate or receive electrons while covalent bonds share electrons.

How does water help stabilize body temperature?

It can absorb large amounts of heat and remain at a fairly stable temperature. When water evaporates, it changes from a liquid to gas; because heat is required for that process, the evaporation of water from the surface of the body rids the body of excess heat.

If the respiration rate increases, CO2 is eliminated from the blood. What effect does this change have on blood H+ levels?

It decreases because when CO2 leaves the blood, it decreases the amount of H2CO3 formed, which causes H+ to be depleted.

Energy from the breakdown of ATP provides the kinetic energy for muscle movement. Why does body temperature increase during exercise.

It takes energy to move muscles during exercise when transferring potential energy to kinetic energy some leaves as heat energy.

Carbonyl

Ketones and aldehydes have a carbonyl group, which is polar and hydrophilic. Ketones contain a carbonyl group within the carbon chain. Ketones are formed during normal metabolism, but they can be elevated in the blood during starvation or certain diabetic states. Aldehydes are similar to ketones, but they have the carbonyl group at the end of the carbon chain.

What is the international unit for mass?

Kilogram, which is the mass of a platinum-iridium cyclinder kept at the International Bureau of Weights and Measurements in France.

What leads to lactose intolerance?

Lack of the enzyme required to break down lactose leads to lactose intolerance.

How is Lactose formed?

Lactose, or milk sugar, is glucose combined with galactose.

What disaccharides are important to humans?

Lactose, or milk sugar, is glucose combined with galactose. Maltose, or malt sugar, is two glucose molecules joined together.

What is the building block of carbohydrates? What are isomers?

Large carbohydrates are composed of numerous relatively simple building blocks called monosaccharides, or simple sugar. Isomers are molecules that have the same number and types of atoms but differ in their three-dimensional arrangement.

What is a monosaccharide?

Large carbohydrates are composed of numerous, relatively simple building blocks called monosaccharides, or simple sugars. Monosaccharides commonly contain 3 carbons (trioses), 4 carbons (tetroses), 5 carbons (pentoses) or 6 carbons (hexoses)

What do lipids consist of?

Like carbohydrates, lipids are composed principally of carbon, hydrogen, and oxygen, but lipids have a lower ratio of oxygen to carbon than do carbohydrates. Some lipids also contain small amounts of other elements, such as phosphorus and nitrogen, which can aid solubility in water.

What are fats used for?

Like carbohydrates, the fats humans ingest are broken down by hydrolysis reactions in cells to release energy for use by those cells.

What is starch and cellulose composed of?

Like glycogen, both are composed of long chains of glucose.

What is a lipid?

Lipids are a major group of organic molecules that are defined as being relatively insoluble in water.

Can lipids be used as an energy source?

Lipids are major energy-storage molecules and can be broken down and used as a source of energy.

How can lipids be used as energy?

Lipids can be stored and broken down later for energy; per unit of weight, they yield more energy than carbohydrates or proteins.

What are the important functions of lipids in the body?

Lipids have many important functions in the body. They provide protection and insulation, help regulate many physiological processes, and form plasma membranes.

What is a solvent?

Liquid that holds another substance in solution.

How is maltose formed?

Maltose, or malt sugar, is two glucose molecules joined together.

Give an example of how water is used in a chemical reaction.

Many of the chemical reactions necessary for life do not take place unless the reacting molecules are dissolved in water. For example, NaCl must dissociate in water into Na+ and Cl-, which can then react with other ions. Water also directly participates in many chemical reactions. As previously mentioned, a dehydration reaction is a synthesis reaction that produces water, and a hydrolysis reaction is a decomposition reaction that requires water.

What do the therapeutic effects of aspirin result from?

Many of the therapeutic effects of aspirin and other anti-inflammatory drugs results from their ability to inhibit prostaglandin synthesis.

Define matter. How are the mass and the weight of an object different?

Matter is anything that occupies space and has mass. Mass is the amount of matter in an object while weight is the gravitational force acting on an object of a given mass.

Summarize the characteristics of mechanical, chemical, and heat energies.

Mechanical energy results from the position or movement of objects. Chemical energy is a form of potential energy stored within the chemical bonds of a substance. Heat energy is a form of energy that flows from a hotter object to a cooler object.

What is a colloid?

Milk water, a mixture in which a dispersed substance or particle is unevenly distributed throughout the mixture. A colloid is a mixture in which a dispersed substance or particle is unevenly distributed throughout the mixture. Unlike a suspension, the dispersed particles are small enough that they do not settle out. Proteins are common dispersed particles; proteins and water form colloids. For instance, the plasma portion of blood and the liquid interior of cells are colloids containing many important proteins.

What are isomers?

Molecules having the same number and types of atoms but differing in their three-dimensional arrangement.

What is a non electrolyte?

Molecules that do not dissociate and do not conduct electricity.

What are differences between monoglycerides, diglycerides and triglycerides?

Monoglycerides have one fatty acid, diglycerides have two fatty acids, and triglycerides have three fatty acids bound to glycerol.

What do most naturally occurring fatty acids contain?

Most naturally occurring fatty acids contain an even number of carbon atoms, with 14- to 18-carbon chains the most common.

What is a anion

Negatively charged ion

Are all molecules compounds?

No. For example, a hydrogen molecule is not a compound because it does not consist of different types of atoms.

What are nucleotides composed of?

Nucleotides are composed of a monosaccharide, a nitrogenous base, and a phosphate group.

What is the atomic number?

Number of protons in each type of atom.

What is the mass number?

Number of protons plus the number of neutrons in each atom.

What is the loss of an electron called and the gain of an electron called?

OIL RIG

Where do the names of element comes from?

Occasionally, the symbol is taken from the Latin, Greek, or Arabic name for the element--for example, the symbol for sodium is Na, from the Latin word natrium.

The difference between mass and weight can be illustrated by considering an astronaut. How do an astronaut's mass and weight in outer space compare with the astronaut's mass and weight on the earth's surface?

On earth the weight of an astronaut is heavier because of the lack of gravity the earth has versus the moon the astronaut is lighter because of the gravitational pull it has. The weight is different on the moon and earth but the mass is the same.

What is meant by the statement "DNA strands are antiparallel"?

One side of DNA is runs 5 to 3 and the other side runs 3 to 5.

What is osmolality?

Osmotic concentration of a solution; the number of moles of solute in 1kg of water times the number of particles into which the solute dissociates.

What four elements consist of 96% of the humans body weight?

Oxygen = 65.0% Carbon = 18.5% Hydrogen = 9.5% Nitrogen = 3.3%

What is oxygen and how is it important to the body?

Oxygen is an inorganic molecule consisting of two oxygen atoms bound together by a double covalent bond. About 21% of the gas in the atmosphere is oxygen, and it is essential for most living organisms. Humans require oxygen in the final step of a series of reactions that extract energy from food molecules.

Phosphate

Phosphates have a phosphate group, which is very hydrophilic due to the double negative charge. Phosphates are used as an energy source (adenosine triphosphate), in biological membranes (phospholipids), and as intracellular signaling molecules (protein phosphorylation).

How do lipids provide structure?

Phospholipids and cholesterol are important components of the membranes of cells.

What contributes to the fluidity of the membrane?

Phospholipids are important structural components of the membranes of cells. The presence of phospholipids with unsaturated fatty acids contributes to the fluidity of the plasma membrane.

What is a phospholipid?

Phospholipids are similar to triglycerides, except that one of the fatty acids bound to the glycerol is replaced by a phosphate-congaing region.

What type of bond would form when electrons are shared between an atom with stronger electronegativity and an atom with weaker electronegativity?

Polar covalent bond.

Give some examples of polyunsaturated fats?

Polyunsaturated fats, such as safflower, sunflower, corn, and fish oils, have two or more double covalent bonds between carbon atoms.

What is a cation?

Positively charged ion

What do prostaglandins regulate?

Prostaglandins have been implicated in regulating the secretion of certain hormones, blood clotting, some reproductive functions, and many other processes.

What are three examples of eicosanoids and their general functions?

Prostaglandins- Class of physiologically active substances present in many tissues; among its effect are vasodilation, stimulation and contraction of uterine smooth muscle and the promotion of inflammation and pain. thromboxanes-a hormone of the prostacyclin type released from blood platelets. It induces platelet aggregation and arterial constriction. Leukotrienes - Specific class of physiologically active fatty acid derivatives present in many tissues.

What are the roles of lipids in the body?

Protection: Fat surrounds and pads organs. Insulation: Fat under the skin prevents heat loss. Myelin surrounds nerve cells and electrically insulates the cells from one another. Regulation: Steroid hormones regulate many physiological processes. For example, estrogen and testosterone are the reproductive hormones responsible for many of the differences between males and females. Prostaglandins help regulate tissue inflammation and repair. Vitamins: Fat-soluble vitamins perform a variety of functions. Vitamin A forms a retinol, which is necessary for seeing in the dark; active vitamin D promotes calcium uptake by the small intestine; vitamin E promotes wound healing; and vitamin K is necessary for the synthesis of proteins responsible for blood clotting. Structure: Phospholipids and cholesterol are important components of the membranes of cells. Energy: Lipids can be stored and broken down later for energy; per unit of weight, they yield more energy than carbohydrates or proteins.

State 6 roles of lipids in the body, and give an example of each.

Protection: Fat surrounds and pads organs. Insulation: Fat under the skin prevents heat loss. Myelin surrounds nerve cells and electrically insulates the cells from one another. Regulation: Steroid hormones regulate many physiological processes. For example, estrogen and testosterone are the reproductive hormones responsible for many of the differences between males and females. Prostaglandins help regulate tissue inflammation and repair. Vitamins: Fat-soluble vitamins perform a variety of functions. Vitamin A forms retinol, which is necessary for seeing in the dark; active vitamin D promotes calcium uptake by the small intestine; vitamin E promotes wound healing; and vitamin K is necessary for the synthesis of proteins responsible for blood clotting. Structure: Phospholipids and cholesterol are important components of the membranes of cells. Energy: Lipids can be stored and broken down later for energy; per unit of weight, they yield more energy than carbohydrates or proteins.

What are proteins?

Proteins are polypeptides composed of hundreds of amino acids.

How do proteins Energy?

Proteins can be broken down for energy; per unit of weight, they yield as much energy as carbohydrates do.

What are the functions of proteins?

Proteins have many important functions in the body: (1) regulate body processes, (2) act as a transportation system, (3) provide protection, (4) help muscles contract, and (5) provide structure and energy.

For each subatomic particle of an atom, state its charge and location. Which region of an atom is most responsible for the mass of the atom? its volume?

Proton, positive, and nucleus Electron, negative, electron cloud. Neutron, neutral, nucleus. the nucleus is responsible for the mass and the electrons are responsible for the volume. The nucleus accounts for 99.97 % of an atom's mass but only 1 ten-trillionth of its volume. Most of the volume of an atom is occupied by the electrons.

Which subatomic particle determines the atomic number? What determines the mass number?

Protons determine the atomic number. Protons and neutrons determine the mass number.

Name the subatomic particles of an atom, and indicate their mass, charge, and location in an atom.

Protons, 1 AMU, positive, central part of an atom. Neutron, 1 AMU, no charge, central part of an atom. Electron, 0 AMU, negative, floats around the outer shell of an atom.

How are ions formed?

Recall that an atom is electrically neutral because it has equal numbers of protons and electrons. However, an atom can donate or lose electrons to other atoms depending on its electronegativity. When this occurs, the numbers of protons and electrons are no longer equal, and a charged particle, called an ion is formed.

Dihydrogen phosphate ion (H2PO4-) and mono hydrogen phosphate ion (HPO42-) form the phosphate buffer system. Identify the conjugate acid and the conjugate base in the phosphate buffer system: H2PO4- = H+ + HPO4^2- Explain how they function as a buffer when either H+ or OH- are added to the solution.

Recall that the definition of an acid is a proton donor. Thus, by losing an H+, dihydrogen phosphate ion (H2PO4-), it is functioning as the conjugate acid. When the H+ is lost, monohydrogen phosphate ion (HPO4-) is formed and is the conjugate base. The definition of a base is a proton acceptor. Thus, if H+ is added to the solution, it combines with HPO4-, helps resist an increase in free H_ by acting as an H+ "sponge." If OH- is added to the solution, it combines with any free H+ to form water. Now, H2PO4- (the conjugate acid) can dissociate into H+ and HPO4-, thus serving as a reservoir of H+ and a decrease in H+ is prevented, again resisting a change in pH. This is the essence of a buffer system: alternating between binding excess H+ and donating H+ when needed.

What are the roles of protein in the body?

Regulation: Enzymes control chemical reactions. Hormones regulate many physiological processes; for example, insuring affects glucose transport into cells. Transport: Hemoglobin transports oxygen and carbon dioxide in the blood. Plasma proteins transport many substances in the blood. Proteins in plasma membranes control the movement of materials into and out of the cell. Protection: Antibodies protect against microorganisms and other foreign substances. Contraction: Actin and myosin in muscle are responsible for muscle contraction. Structure: Collagen fibers form a structural framework in many parts of the body. Keratin adds strength to skin, hair, and nails. Energy: Proteins can be broken down for energy; per unit of weight, they yield as much energy as carbohydrates do.

What should we remember about molecules?

Remember that to be a molecule, a structure must be independent.

What is the tertiary structure?

Results from large-scale folding of the protein driven by interactionns within the protein and with the immediate environment. These interactions allow the pleated sheets and helices of the secondary structure to be arranged and organized relative to each other. Some amino acids are quite polar (hydrophilic) and therefore form hydrogen bonds with water. The polar portions of proteins tend to remain unfolded , maximizing their contact with water, whereas the less polar (Hydrophobic) regions tend to fold into a globular shape, minimizing their contact with water.

What is a secondary structure?

Results from the folding or bending of the polypeptide chain cause by the hydrogen bonds between amino acids. Two common shapes that result are pleated (folded) sheets and helices (sing. helix, coil). If the hydrogens bonds that maintains the shape of the protein are broken, the protein becomes denature and nonfunctional.

Define double covalent bond

Results when two atoms share 4 electrons, 2 from each atom. When a carbon atom combines with oxygen atoms to form carbon dioxide (CO2), two double covalent bonds form.

What is a reversible reaction? How does this type of reaction lead to chemical equilibrium?

Reversible reactions are when the reactants form products and the products can be put back into the reaction to form the reactants. This reaction is considered equilibrium because the reactants and products remain the same.

Where are carbohydrates used for structure?

Ribose forms part of RNA and ATP molecules. Deoxyribose forms part of DNA.

What is an isotope? How are isotopes denoted?

Same number of protons but different number of neutrons. Isotopes can be denoted using the symbol of the element preceded by the mass number (number of protons and neutrons) of the isotope. Thus, hydrogen is 1H, deuterium is 2H and tritium is 3H.

Describe solubility and the process of dissociation, and predict if a compound or molecule is an electrolyte or nonelectrolyte

Solubility is the ability of one substance to dissolve in another--for example, sugar dissolving in water. When ionic compounds dissolve in water, their ions dissociate, or separate, from one another because cations are attracted to the negative ends of water molecule and anions are attracted to the positive ends of water molecules.

Using the terms solute and solvent, summarize the properties of solutions, suspensions, and colloids.

Solutions are known as heterogenous or uniform because the solutes dissolve into the solvent and are unseen. Suspensions are known as non heterogenous or nonuniform because the solute and solvent has to be continuously mixed or they will separate. Colloids are also nonuniform because the solutes never settle and our constantly moving within the solvent.

What is a basic solution?

Solutions with a pH greater than 7 are alkaline or basic, and have fewer H+ than OH-

Explain how reversible reactions produce chemical equilibrium.

Some chemical reactions are reversible. In a reversible reaction, the reaction can run in the opposite direction, so that the products are converted back to the original reactants. When the rate of product formation is equal to the rate of the reverse reaction, the reaction system is said to be at equilibrium. At equilibrium, the amount of reactants relative to the amount of products remains constant.

Give some examples of saturated fats?

Sources of saturated fats include beef, pork, whole milk, cheese, butter, eggs, coconut oil, and palm oil.

Define thromboxanes

Specific class of physiologically active fatty acid derivatives present in many tissues.

What are leukotrienes?

Specific class of physiologically active fatty acid derivatives present in many tissues.

List and briefly describe the four functions that water performs in living organisms.

Stabilized body temperature, when we sweat and the water evaporates we lose heat causing us to become cooler. Protection, water acts as a lubricant to protect organs or our inside from damage. Chemical reactions use water to form products and carry out processes within the body. Mixing medium, water is known as the universal solvent and can help dissolve all substances.

What are some of the physical and chemical properties of water that aid organisms in survival?

Stabilizing Body temp Protection Mixing medium Chemical reactions.

What two important polysaccharides are found in plants?

Starch and cellulose are two important polysaccharides found in plants.

What is starch and what is its function?

Starch is a sugar. Plants use starch as an energy-storage molecule in the same way that animals use glycogen.

How do lipids regulate?

Steroid hormones regulate many physiological processes. For example, estrogen and testosterone are the reproductive hormones responsible for many of the differences between males and females. Prostaglandins help regulate tissue inflammation and repair.

FIGURE 2.21 Steroids

Steroids are four-ringed molecules that differ from one another according to the groups attached to the rings. Cholesterol, the most common steroid, can be modified to produce other steroids.

How do steroids differ?

Steroids differ in chemical structure from other lipid molecules, but their solubility characteristics are similar.

What is the difference between a strong acid or base and a weak or base?

Strong acids and bases dissociate completely when put into water versus weak acids and bases dissociate partially when put in water.

What are the roles of carbohydrates in the body?

Structure: Ribose forms part of RNA and ATP molecules, an deoxyribose forms part of DNA Energy: Monosaccharides (glucose, fructose, galactose) can be used as energy sources. Disaccharides (sucrose, lactose, maltose) and polysaccharides (starch, glycogen) must be broken down to monosaccharides before they can be used for energy. Glycogen is an important energy-storage molecule in muscles and in the liver. Bulk: Cellulose forms bulk in the feces.

How do you find the number of neutrons for any element?

Subtract the atomic number from the mass number.

What is meant by the statement "table sugar is soluble in water"?

Sugar dissolving in water. Charged substances, such as sodium chloride, and polar substances, such as glucose, readily dissolve in water, whereas non polar substances, such as oils, do not.

Phosphorus

Symbol : P Atomic Number: 15 Mass Number: 31 Atomic Mass: 30.97 Percent in Human Body by Weight (%): 1.0 Percent in Human Body by Number of Atoms (%): 0.22

Carbon

Symbol: C Atomic Number: 6 Mass Number: 12 Atomic Mass: 12.01 Percent in Human Body by Weight (%): 18.5 Percent in Human Body by Number of Atoms (%): 9.5

Calcium

Symbol: Ca Atomic Number: 20 Mass Number: 40 Atomic Mass: 40.08 Percent in Human Body by Weight (%): 1.5 Percent in Human Body by Number of Atoms (%): 0.31

Calcium ion

Symbol: Ca2+ Significance: Part of bones and teeth; functions in blood clotting, muscle contraction, release of neurotransmitters.

Chlorine

Symbol: Cl Atomic Number: 17 Mass Number: 35 Atomic Mass: 35.45 Percent in Human Body by Weight (%): 0.2 Percent in Human Body by Number of Atoms (%): 0.03

Chloride ion

Symbol: Cl- Significance: Water balance

Fluorine

Symbol: F Atomic Number: 9 Mass Number: 19 Atomic Mass: 19.00 Percent in Human Body by Weight (%): Trace Percent in Human Body by Number of Atoms (%): Trace

Iron

Symbol: Fe Atomic Number: 26 Mass Number: 56 Atomic Mass: 55.85 Percent in Human Body by Weight (%): Trace Percent in Human Body by Number of Atoms (%): Trace

Iron ion

Symbol: Fe2+ Significance: Red blood cell formation

Hydrogen

Symbol: H Atomic Number: 1 Mass Number: 1 Atomic Mass: 1.008 Percent in Human Body by Weight(%): 9.5 Percent in Human Body by Number of Atoms (%): 63.0

Hydrogen ion

Symbol: H+ Significance: Acid-base balance

Bicarbonate ion

Symbol: HCO3- Significance: Acid-base balance

Iodine

Symbol: I Atomic Number: 53 Mass Number: 127 Atomic Mass: 126.9 Percent in Human Body by Weight: Trace Percent in Human Body by Number of Atoms (%): Trace

Iodide ion

Symbol: I- Significance: Present in thyroid hormones.

Potassium

Symbol: K Atomic Number: 19 Mass Number: 39 Atomic Mass: 39.10 Percent in Human Body by Weight (%): 0.4 Percent in Human Body by Number of Atoms (%): 0.06

Potassium ion

Symbol: K+ Significance: Membrane potentials

Magnesium

Symbol: Mg Atomic Number: 12 Mass Number: 24 Atomic Mass: 24.31 Percent in Human Body by Weight(%): 0.1 Percent in Human Body by # of Atoms (%): 0.1

Magnesium ion

Symbol: Mg2+ Significance: Necessary for enzymes

Nitrogen

Symbol: N Atomic Number: 7 Mass Number: 14 Atomic Mass Body: 14.01 Percent in Human Body by Weight (%): 3.3 Percent in Human Body by Number of Atoms (%): 1.4

Ammonium ion

Symbol: NH4+ Significance: Acid-base balance

Sodium

Symbol: Na Atomic Number: 11 Mass Number: 23 Atomic Mass: 22.99 Percent in Human Body by Weight (%): 0.2 Percent in Human Body by Number of Atoms (%): 0.3

Sodium ion

Symbol: Na+ Significance: Membrane potentials, water balance.

Oxygen

Symbol: O Atomic Number: 8 Mass Number: 16 Atomic Mass: 16.08 Percent in Human Body by Weight : 65.0 Percent in Human Body by Number of Atoms (%): 25.5 s

Hydroxide ion

Symbol: OH- Significance: Acid-base balance

Phosphate ion

Symbol: PO4^3 Significance: Part of bones and teeth; functions in energy exchange, acid-base balance.

Sulfur

Symbol: S Atomic Number: 16 Mass Number: 32 Atomic Mass: 32.07 Percent in Human Body by Weight(%): 0.3 Percent in Human Body by Number of Atoms (%): 0.05

Contrast synthesis and decomposition reactions, and explain how catabolism and anabolism relate to these two types of reactions.

Synthesis is the same as anabolism they both take energy to carry out a function. Decomposition is the same as catabolism, they both release energy to carry out a function. The difference between synthesis and decomposition is synthesis take in energy to carry out a function while decomposition releases energy to carry out a function.

Summarize the characteristic of synthesis, decomposition, reversible reactions, and oxidation-reduction reactions.

Synthesis reaction is when two or more reactants chemically combine to form a new and large product. The synthesis reactions occurring in the body are collectively referred to as anabolism A decomposition reaction is the reverse of a synthesis reaction--a larger reactant is chemically broken down into two or more smaller products. The decomposition reactions occurring in the body are collectively called catabolism. Reversible reactions are reactions that work both ways, the sum of reactants is equal to the products and the products are equal to the sum of reactants. Chemical reactions that result from the exchange of electrons between the reactants are called oxidation-reduction reactions. When sodium and chlorine react to form sodium chloride, the sodium atom loses an electron and the chlorine atom gains an electron. The loss of an electron by an atom is called oxidation, and the gain of an electron is called reduction. OIL RIG Because one atom partially or completely loses an electron and another atom gains that electron, these reactions are called oxidation-reduction reactions.

What is dehydration reaction

Synthesis reactions in which water is a product are called dehydration (water out) reactions.

What is an example of a substance that is a compound but not a molecule?

Table salt (NaCl) is an example of a substance that is a compound but not a molecule. A piece of NaCl does not consist of individual sodium chloride molecules positioned next to one another. Instead, NaCl is an organized array of individual Na+ and individual Cl- in which each charged ion is surrounded by several ions of the opposite charge.

What is an Hydrogen Bond?

The attraction of oppositely charged ends of one polar molecule to another polar molecule holds molecules or parts of molecules together.

What are the building blocks of proteins? What type of bond chemically connects these building blocks? What is the importance of the R group?

The basic building blocks for proteins are the 20 amino acid molecules. Each amino acid has an amine group (--NH2), a carboxyl group (--COOH), a hydrogen atom, and a side chain designated by the symbol R attached to the same carbon atom. The side can be a variety of chemical structures, and th differences in the side chains make the amino acids different from one another. Peptide bonds connects these building blocks. The r group determines the function of the amino acid.

What is a nucleotide?

The basic building blocks of DNA and RNA are called nucleotides. Basic building block of nucleic acids consisting of a sugar (either ribose or deoxyribose) and one of several types of organic bases.

What are the basic building blocks of nucleic acids? What kinds of sugars and bases are found in DNA? In RNA?

The basic building blocks of DNA and RNA are called nucleotides. Each nucleotide is composed of a monosaccharide to which a nitrogenous base and a phosphate group are attached. The 5-carbon monosaccharide is deoxyribose for DNA; it is ribose for RNA. The nitrogenous bases consist o carbon and nitrogen atoms organized into rings. They are bases because the nitrogen atoms tend to take up H+ from solution. The nitrogenous bases are cytosine, thymine, uracil, which have a single ring, and guanine and adenine, which have two rings each. Single-ringed bases are called pyrimidines, and double-ringed bases are called purines.

Describe the role of nucleotides in the structures and functions of DNA, RNA, and ATP.

The basic building blocks of DNA and RNA are called nucleotides. Each nucleotide is composed of a monosaccharide to which a nitrogenous base and a phosphate group are attached. The 5-carbon monsaccharide is deoxyribose for DNA; it is ribose for RNA. The nitrogenous bases consist of carbon and nitrogen atoms tend to take up H+ from solution. The nitrogenous bases are cytosine, thymine, and uracil, which have a single ring, and guanine and adenine, which have two rungs each. Single-ringed bases are called pyrimidines and double ringed bases are called purines

Electron-Dot Formula

The boding electrons are shown as dots between the symbols of the atoms. Examples H:H = single covalent bond O::C::O = Double covalent bond

Bond-Line Formula

The bonding electrons are shown as lines between the symbols of the atoms. Example: H-H=Single covalent bond O=C=O= double covalent bond

What is unsaturated?

The carbon chain is unsaturated if it has one or more double covalent bonds between carbon atoms.

What are carboxyl groups responsible for?

The carboxyl group is responsible for the acidic nature of the molecule because it releases hydrogen ions into solution.

How is energy released from ATP?

The close proximity of the three negatively charged phosphate groups make ATP a very unstable molecule. As a result, cleavage of the phosphate bonds releases a large amount of energy; hence, the second and third phosphate bonds are referred to as "high-energy" bonds. In particular, the potential energy stored in the covalent bond between the second and third phosphate groups of ATP is important to living organisms because it provides the energy used in nearly all of the chemical reactions within cells. Removal of the third phosphate generates adenosine diphosphate (ADP), which has only two phosphate groups.

What is catabolism?

The decomposition reactions occurring in the body are collectively called catabolism.

What keeps unsaturated fats liquid at room temperature?

The double covalent bond introduces a kink into the carbon chain, which tends to keep them liquid at room temperature.

What changes cis configuration to trans configuration?

The double covalent bonds that do not become saturated are changed from the usual cis configuration (H on the same side of the double bond to a trans configuration (H on different sides)

What change in structure results in a greater risk for cardiovascular disease?

The double covalent bonds that do not become saturated are changed from the usual cis configuration (H on the same side of the double bond) to a trans configuration (H on different sides). This change in structure makes the consumption of trans fats an even greater factor than saturated fats in the risk for cardiovascular disease.

What are eicosanoids?

The eicosanoids are a group of important chemicals derived from fatty acids.

What is an electron shell?

The energy levels are often depicted as concentric rings, called electron shells.

What analogy helps clarify the concept of reversible reactions?

The following analogy may help clarify the concept of reversible reactions and equilibrium. Imagine a football team. The team is divided into two groups: players on the field and those on the bench. Because the players can move in either direction (on or off the field), this is like a reversible reaction. Imagine that the players on the bench are the reactant and the players on the field (lined up in formation) are the product. At equilibrium, the amount of reactant relative to the amount of product is always the same. When some players on the bench run onto the field, an equal number of players run off the field, so equilibrium is maintained.

Chemical Formula

The formula shows the kind and number of atoms present. Examples: H2, CO2, C6H12O6

Which part of the phospholipid is polar and which is non polar?

The head or circle is polar and hydrophilic, the legs or tail is non polar and hydrophobic.

FIGURE 2.29 Structure of an Adenosine Triphosphate (ATP) Molecule

The key feature of ATP is the presence of three phosphate groups on adenosine. The high-energy phosphate bonds are indicated by the red squiggles.

What makes carbohydrates polar?

The large number of oxygen atoms in carbohydrates makes them relatively polar molecules. Consequently, they are soluble in polar solvents, such as water.

What are the major classes of lipids?

The major classes of lipids are (1) fats, which are mostly triglycerides; (2) phospholipids; (3) eicosanoids; (4) steroids; and (5) fat-soluble vitamins.

What is the molecular mass of proteins?

The molecular mass of proteins can be very large. For this purpose of comparison, the molecular mass of water is approximately 18, sodium chloride 58, and glucose 180, but the molecular mass of proteins ranges from approximately 1000 to several million.

What are the monosaccharides of nucleotides?

The monosaccharides are deoxyribose for DNA and ribose for RNA.

Why are nitrogenous bases basic?

The nitrogenous bases are basic because the nitrogen atom tend to take up H+ from solution.

What does the nitrogenous bases consist of?

The nitrogenous bases consist of carbon and nitrogen atoms organized into rings.

How do we know if an element is electrically neutral?

The number of protons and the number of electrons in each atom are equal, and the individual charges cancel each other.

How is the osmolality of a solution determined? What is a milliosmole?

The osmolality of a solution is determine by weight per kilogram of solution or number of osmoles in a concentration. depending on the number of particles in a solution, the osmolality reflects how many particles their are in the solution. A milliosmole is 1/1000 of an osmole. a measurement used to determine the concentration of body fluids.

What is the valence shell?

The outermost shell.

Describe the pH scale and its relationship to acidic, basic, and neutral solutions.

The pH scale is a means of referring to the H+ concentration in a solution. The scale ranges from 0 to 14. A neutral solution has equal concentrations H+ and OH-; pure water is considered a neutral solution and has a pH of 7. Solutions with a pH less than 7 are acidic and have a greater concentration of H+ than OH-. Solutions with a pH greater than 7 are alkaline, or basic, and have fewer H+ than OH-.

What determines the primary, secondary, tertiary, and quaternary structures of a protein?

The primary structure of a protein is determined by the sequence of the amino acids bound by peptide bonds. The potential number of different protein molecules is enormous because 20 different amino acids exist, and each amino acid can be located at any position along a polypeptide chain. The secondary structure results from the folding or bending of the polypeptide chain caused by the hydrogen bonds between amino acids. Two common shapes that result are pleated (folded) sheet and helices. The tertiary structure results from large-scale folding of the protein driven by interactions within the protein and with the immediate environment. These interactions allow the pleated sheets and helices of the secondary structure to be arranged and organized relative to each other. Quaternary structures results from the association of two or more proteins to form a functional unit. The individual proteins are called subunits. Interaction between subunits result in the quaternary structure.

How do the properties of elements change when they are combined to form compounds?

The properties of elements can change when they are combined to form compounds. For example, the element hydrogen is extremely flammable, and oxygen, although not flammable on its own, promotes fire. However, when combined, hydrogen and oxygen form the very nonflammable compound water.

Describe the factors that can affect the rate of chemical reactions.

The reactants and the products. Temperature, as temperature increases, reactants have more kinetic energy, moves faster speeds, and collide with one another more frequently and with greater force, thereby increasing the likelihood of a chemical reaction. When body temperature drops, various metabolic processes slow.

What is a reversible reaction?

The reaction can run in the opposite direction, so that the products are converted back to the original reactants.

What does electronegativity dictate?

The relative electronegativity of two atoms dictates the degree of sharing of electrons between those atoms.

What are the rungs of the ladder formed by?

The rungs of the ladder are formed by the nitrogenous bases of the nucleotides of one side connected to the nitrogenous bases of the other side by hydrogen bonds.

Define a single covalent bond

The sharing of one pair of electrons by two atoms results in a single covalent bond. A single line between the symbols of atoms involved represents a single covalent bond.

What are the sides of the ladder formed by?

The sides of the ladder are formed by covalent bonds between the deoxyribose molecules and phosphate groups of adjacent nucleotides.

How do carbonic acid and bicarbonate act as buffers?

The sodium salt of bicarbonate (NaHCO3) also known as baking soda, is an active ingredient in some antacids taken to reduce stomach acidity. In the forward reaction, H2CO3 loses a H+ to produce HCO3-, which is a conjugate base. In the reverse reaction, a H+ is transferred to the HCO3- (conjugate base) to produce H2CO3, which is a conjugate acid. For a given condition, this reversible reaction results in an equilibrium, in which the amounts of H2CO3 relative to the amounts of H+ and HCO3- remain constant. The conjugate acid-base pair can resist change in pH because of this equilibrium.

What is the octet rule?

The tendency of atoms to combine with other atoms until each has 8 electrons (2 electrons for hydrogen) in it valence shell.

What is a domain?

The tertiary structure determines the shape of a domain, which is a folded sequence of 100-200 amino acids within a protein. The functions of proteins occur at one or more domains. Therefore, changes in the primary or secondary structure that affect the shape of the domain can change protein function.

What is the conservation of energy principle?

The total energy of the universe is constant. Therefore, energy is neither created nor destroyed, but it can take on different forms. For example, the potential energy in the ball is coverted into kinetic energy as the ball falls toward the floor. Conversely, the kinetic energy required to raise the ball from the floor is converted back into potential energy.

What are the two major ways an octet can be achieved?

The transfer of electrons between atoms and the sharing of electrons between atoms.

How do oxidation reduction reactions form ionic or covalent bonds?

The transfer of the electron can be complete, resulting in an ionic bond, or it can be partial, resulting in a covalent bond. Because one atom partially or completely loses an electron and another atom gains that electron, these reactions are called oxidation-reduction reactions.

Why is complementary base pairing useful?

The two strands of a DNA molecule are said to be complementary. If the sequence of bases on one DNA strand is known, the sequence of bases in the other strand can be predicted because of complementary base pairing.

What are the two types of nucleic acids?

There are two types of nucleic acids: Deoxyribonucleic acid (DNA) is the genetic material of cells. Copies of DNA are transferred from one generation of cells to the next generation. DNA contains the information that determines the structure of proteins. Ribonucleic acid is structurally related to DNA, and there types of RNA play important roles in protein synthesis.

Give an example of isomers and stereoisomers?

These monosaccharides almost always form a ring-shaped molecule. Although not labeled with a C, carbon atoms are located at the corners of the ring-shaped molecules. Fructose is a structural Isomer of glucose because it has identical chemical groups bonded in a different arrangement in the molecule (red shading). Galactose is a stereoisomer of glucose because it has exactly the same groups bonded to each carbon atom but located in a different three-dimensional orientation (yellow shading).

FIGURE 2.16 Monosaccharides

These monosaccharides almost always form a ring-shaped molecule. Although not labeled with a C, carbon atoms are located at the corners of the ring-shaped molecules. Fructose is a structural isomer of glucose because it has identical chemical groups bonded in a different arrangement in the molecule (red shading). Galactose is a stereoisomer of glucose because it has exactly the same groups bonded to each carbon atom but located in a different three-dimensional orientation (yellow shading.

What happens when strong acids or bases enter water?

They dissociate immediately releasing all of their H+ or OH- ions.

What do eicosanoids include?

They include prostaglandins, thromboxines, and leukotrienes.

What is an example of decomposition reactions?

They include the digestion of food molecules in the intestine and within cells, the breakdown of fat stores, and the breakdown of foreign matter and microorganisms in certain blood cells that protect the body.

Explain the importance of buffers in organisms.

They maintain the pH of fluids in our body and can help achieve homeostasis. A major buffer in our body fluids is the bicarbonate system. A bicarbonate ion (HCO3-) is formed by the dissociation of carbonic acid (H2CO3). Carbonic acid and bicarbonate are a conjugate acid-base pair. The sodium salt of bicarbonate (NaHCO3) also known as baking soda, is an active ingredient in some antacids taken to reduce stomach acidity.

Sulfhydryl

Thiols have a sulfhydryl group, which is polar and hydrophilic. The amino acid cystine contains a sulfhydryl group that can form a disulfide bond with another cysteine to help stabilize protein structure.

What are three important polysaccharides?

Three important polysaccharides are glycogen, starch, and cellulose.

What is triglyceride?

Three-carbon glycerol molecule with a fatty acid attached to each carbon; constitute approximately 95% of the fats in the human body. Also called triacylglycerol.

When hydrogen gas combines with oxygen gas to form water, is the hydrogen reduced or oxidized? Explain.

To answer this question, it may be helpful to write out the formulas of the reactants and the products. Hydrogen gas is represented by H2, whereas O2 represents oxygen gas; the product, water is represented by H2O. The oxygen atom is more electronegative than hydrogen, and each hydrogen forms a polar covalent bond with the oxygen. Recall that a polar covalent bond occurs when the more electronegative atom can pull the electrons more strongly and the electrons associate with the oxygen more than they do the hydrogens. In a way, the oxygen has gained some negativity and its charge has been lowered. Thus, we say that the oxygen is reduced. On the other hand, the hydrogen atoms have partially lost their units of negativity, their electrons, and are more positive than they were before. In this case, we say the hydrogens are oxidized. The term oxidized is used because oxygen is an effect electron acceptor. A useful mnemonic device to remember these terms is OIL RIG (oxidation is loss [of electrons]; reduction is gain [of electrons]).

What are trans fats?

Trans fats are unsaturated fats that have been chemically altered by the addition of hydrogen. The process makes the fats more saturated and hence more solid and stable (longer shelf life).

What makes a Triglyceride?

Triglycerides consist of two different type of building blocks: one glycerol and three fatty acids.

What is the most common fat in the body, and what are its basic building blocks?

Triglycerides constitue 95% of the fats in the human body. Triglycerides consist of two different types of building blocks: one glycerol and three fattty acids. Glycerol is a 3-carbon molecule with a hydroxyl group attached to each carbon atom. Each fatty acid is a straight chain of carbon atoms with a carboxyl group attached at one end. A carboxyl group (--COOH) consists of both an oxygen atom and a hydroxyl group attached to a carbon atom.

What constitutes 95% of the fats in the human body?

Triglycerides constitute 95% of the fats in the human body.

Which fats are the best type of fats?

Unsaturated fats are the best type of fats in the diet because, unlike saturated fats, they do not contribute to the development of cardiovascular disease.

What are fat-soluble vitamins?

Vitamin, such as A,D, E, and K, that is soluble in lipids and absorbed from the intestine along with lipids. Their structures are not closely related to one another, but they are non polar molecule essential for many normal body functions.

How much does water account for in males and females?

Water accounts for approximately 50% of the weight of a young adult male and 60% of a young adult male.

How is water formed?

Water has remarkable properties due to its polar nature. A molecule of water is formed when an atom of oxygen forms polar covalent bonds with two atoms of hydrogen. This gives a partial positive to the hydrogen atoms and partial negative charge to the oxygen atom. Because of water's polarity, hydrogen bonds form between positively charged hydrogen atoms of one water molecule and the negatively charged oxygen atoms of another water molecule. These hydrogen bonds organize the water molecules into a lattice, which holds the water molecules together and are responsible for many unique properties of water.

How does water protect the body?

Water protects the body by two ways: as a lubricant and as a cushion. (1) By acting as a lubricant, water reduces damage from friction. For example, tears protect the surface of the eye from rubbing of the eyelids. (2) By forming a fluid cushion around organs, water helps protect the organs from trauma. For example, the cerebrospinal fluid helps protect the brain.

What are intermolecular forces?

Weak electrostatic attractions that exist between oppositely charged parts of molecules, or between ions and molecules. There is no exchange of electrons in intermolecular forces. This differs from other chemical bonds. Intermolecular forces are much weaker than the forces producing chemical bonding. Intermolecular forces include hydrogen bonds and the properties of solubility and dissociation.

Describe what occurs during the dissociation of NaCl in water. What occurs when glucose (C6H12O6) dissolves in water?

When NaCl dissociates in water, sodium and chloride ions separate, and water molecules surround and isolate the ions, thereby keeping them in solution. Sodium chloride produces electrolytes which can be used to conduct electricity. Glucose does not dissociate into ions when dissolved in water. It is a nonelectrolyte. A non electrolyte solution does not contain ions. Therefore, the solution does not conduct electricity and the light bulb does not light.

FIGURE 2.24 Protein Structure

When a chain of amino acids is formed, chemical interactions between amino acids cause the entire chain to fold upon itself in predictable patterns. (a) Primary structure results from the amino acid sequence. (b) Secondary structure results from hydrogen bonds. (c) Tertiary structure results from folding of the protein. (d) Quaternary structure results from association of subunits.

What happens if atoms have different electronegativites?

When atoms have some differences in electronegativities, then there will be unequal sharing of electrons.

How are covalent bonds formed?

When atoms share one or more pairs of electrons. The sharing of electrons, rather than transfer of electrons, occurs because the atoms have similar electronegativities.

What occurs in the formation of a covalent bond? What is the difference between polar and non polar covalent bonds?

When atoms share one or more pairs of electrons. The sharing of electrons, rather than transfer of electrons, occurs because the atoms have similar electronegativities. The resulting combination of atom is called a molecule. Polar covalent bonds share atoms unequally because of electronegativity. Nonpolar covalent bonds share atoms equally.

What happens when electronegativities between atoms is different?

When electronegativities are very different, the atoms tend to transfer electrons. For example, an atom with 7 electrons in its valence shell has a strong pull on electrons, while an atom with 1 electron in its valence shell has a weak pull on electrons. Thus, the "strong" atom can "steal' the valence electron from the "weak" atom, resulting in a transfer of electrons.

What is a nonpolar covalent bond?

When electrons are shared equally between atoms, as in a hydrogen molecule, the bonds are called nonpolar covalent bonds.

Can humans digest cellulose?

When humans ingest plants, the starch can be broken down and used as an energy source. Humans, however, do not have the digestive enzymes necessary to break down cellulose. Cellulose is eliminated in the feces, where it provides bulk.

What does it mean when molecules dissociate?

When ionic compounds dissolve in water, their ions dissociate, or separate, from one another because cations are attracted to the negative ends of water molecules and anions are attracted to the positive ends of water molecules. When NaCl dissociates in water, sodium and chloride ions separate, and water molecules surround and isolate the ions thereby keeping them in solution.

What is equilibrium?

When the rate of product formation is equal to the rate of the reverse reaction, the reaction system is said to be at equilibrium. At equilibrium, the amount of reactants relative to the amount of products remains constant.

What is a synthesis reaction?

When two or more reactants chemically combine to form a new and larger product. The synthesis reactions occurring in the body are collectively referred to as anabolism.

What is an electron cloud?

Where electrons float around the nucleus of an atom.

What is a conjugate acid-base pair?

a conjugate base is what remains of an acid after the H+ (proton) is lost. A conjugate acid is formed when a H+ is trasnferred to the conjugate base. Two substances related in this way are a conjugate acid-base pair.

What is a dalton?

a dalton or unified atomic mass unit (u) is 1/12 the mass of 12C, a carbon atom with 6 protons and 6 neutrons. Thus, 12C has an atomic mass of exactly 12 Da. Just like a dozen is 12 things, a mole is simply Avogadro's number of things. In chemistry, those "things" are atoms or molecules.

What is chemical energy?

a form of potential energy stored within the chemical bonds of a substance. In any chemical reaction, the potential energy in the chemical bonds of the reactants can be compared with the potential energy in the reactants is less than that in the products, energy must be supplied for the reaction to occur. An example is the synthesis of ATP from ADP: ADP + H2PO4 + Energy --> ATP + H2O

What is thromboxanes?

a hormone of the prostacyclin type released from blood platelets. It induces platelet aggregation and arterial constriction.

What is Avogadro's number?

a mole of substance contains Avogadro's number of entities, such as atoms, ions, or molecules. The atomic mass is equal to 1 mole.

what is the lock-and-key model?

a reaction occurs when the reactants (key) bind to the active site (lock) on the enzyme.

What is a compound?

a substance resulting from the chemical combination of two or more different types of atoms.

Define acid and base, and describe the pH scale?

acid is anything below 7, think H+ (hydrogen ions) base is anything above 7, think OH- (hydroxide ions) The pH scale is a scale used to determine the acidity or alkalinity of a solution.

The blood pH of a patient is 7.30. What condition does this patient have, and what are the symptoms?

acidosis, the nervous system becomes depressed and the individual may become disoriented and possibly comatose.

What is a lipase?

any fat-splitting enzyme

What is a solution?

any mixture in which the substances are uniformly distributed.

What is matter?

anything that occupies space and has mass

What are eicosanoids?

are a group of important chemicals derived from fatty acids. They include prostaglandins, thromboxines and leukotrienes. Eicosanoids are made in most cells and are important regulatory molecules. Among their numerous effects is their role in the response of tissues to injuries. Prostaglandins have been implicated in regulating the secretion of certain hormones, blood clotting, some reproductive functions, and many other processes. Many of the therapeutic effects of aspirin and other anti-inflammatory drugs result from their ability to inhibit prostaglandin synthesis.

What are complementary base pairs?

are bases held together by hydrogen bonds. Adenine and thymine are complementary base pairs because the structure of these bases allows two hydrogen bonds to form between them. Cytosine and guanine are complementary base pairs because the structure of these bases allows three hydrogen bonds to form between them. The two strands of a DNA molecule are said to be complementary. If the sequence of bases in one DNA strand is known, the sequence of bases in the other strand can be predicted because of complementary base pairing.

What is a buffer? why is it important?

are chemicals that resist changes in pH when either acids or bases are added to a solution. For example, when an acid is added to a buffered solution, the buffer binds to the H+, preventing these ions from causing a decrease in the pH of the solution.

What are steroids?

are composed of carbon atoms bound together into four ringlike structures.

What is a disacharide?

are composed of two monosaccharides bound together through a dehydration reaction. For example, glucose and fructose combine to form a disaccharide called sucrose plus a molecule of water.

What is a nucleic acid?

are large molecules composed of carbon, hydrogen, oxygen, nitrogen, and phosphorus.

What is a polysaccharide?

are long chains of monosaccharides. These chains can be either straight or branched.

What are enzymes?

are proteins that act as catalyst. Enzymes increase the rate of chemical reactions by lowering the activation energy necessary for the reaction to begin. As a result, more molecules have sufficient energy to undergo chemical reactions. An enzyme allows the rate of chemical reaction to take place more than a million times faster than it would without the enzyme.

What are phospholipids?

are similar to triglycerides, except that one of the fatty acids bound to the glycerol is replaced by a phosphate-containing region. A phospholipid is polar at the end of the molecule to which the phosphate is bound and non polar at the other end. The polar end of the molecule is attracted to water and is said to be hydrophilic. The non polar end is repelled by water and is said to be hydrophobic. Phospholipids are important structural components of the membranes of cells. The presence of phospholipids with unsaturated fatty acids contributes to the fluidity of the plasma membrane.

What is a catalyst?

are substances that increase the rate of chemical reactions without being permanently changed or depleted themselves.

What are isotopes?

are two or more forms of the same element that have the same number of protons and electrons but a different number of neutrons.

What are trans fats?

are unsaturated fats that have been chemically altered by the addition of hydrogen. The process makes the fats more saturated and hence more solid and stable (longer shelf life). However, the double covalent bonds that do not become saturated are changed from the usual cis configuration (H on the same side of the double bond) to a trans configuration (H on different sides). This change in structure makes the consumption of trans fats an even greater factor than saturated fats in the risk for cardiovascular disease.

What is a polar covalent bond?

atoms bound to one another by a covalent bond do not always share their electrons equally because in these situations the electronegativity of one atom is stronger than the other atom.

What and how can we determine the molecular mass?

by adding up the atomic masses of it atoms (or ions). The term molecular mass is used for convenience for ionic compounds, even though they are not molecules.

What are the four major groups of organic molecules essential to living organisms?

carbohydrates lipids proteins nucleic acids.

What is a suspension?

chalk water, the contents of water and another substance has to be continuously mixed and blended together. Blood is a suspension-that is, red blood cells are suspended in a liquid called plasma. As long as the red blood cells and plasma are mixed together as they pass through blood vessels, the red blood cells remain suspended in the plasma. However, if the blood is allowed to sit in a container, the red blood cells and plasma separate from each other.

What is a mixture?

combination of two or more substances physically blended together, but not chemically combined.

What is a molecule?

composed of two or more atoms chemically combined to form a structure that behaves as an independent unit.

What is a triglyceride?

constitute 95% of the fats in the human body. Triglycerides consist of two different types of building blocks: one glycerol and three fatty acids. Glycerol is a 3 carbon molecule with a hydroxyl group attached to each carbon atom. Each fatty acid is a straight chain of carbon atoms with a carboxyl group attached at one end. A carboxyl group consists of both an oxygen atom and a hydroxyl group attached to a carbon atom:

What is a base

defined as a proton acceptor. Any substance that binds to (accepts) H+ is a base. Many bases function as proton acceptors by releasing hydroxide ions (OH-) when they dissociate. The base sodium hydroxide (NaOH) dissociates to form Na+ and OH-: NaOH--> Na+ +OH-

What is an acid?

defined as a proton donor. A hydrogen ion (H+) is a proton because it results when an electron is lost from a hydrogen atom, which leaves just the proton nucleus. Therefore, a molecule or compound that releases H+ is an acid. Hydrochloric acid (HCl) forms hydrogen ions (H+) and chloride ions (Cl-) in solution and therefore is an acid: HCl--> H+ + Cl-

What is a stereoisomer?

each of two or more compounds differing only in the spatial arrangement of their atoms.

What is a gene?

functional unit of heredity. Each gene occupies a specific place, or locus, on a chromosome; it is capable of reproducing itself exactly at each cell division; it often is capable of directing the formation of an enzyme or another protein.

What is a neutral solution?

has equal concentrations of H+ and OH-; pure water is considered a neutral solution and has a pH of 7.

Give an example of activation energy.

heat in the form of a spark is required to start the reaction between oxygen and gasoline vapor. Once some oxygen molecules react with gasoline, the energy released can start additional reactions.

What is the induced fit model?

in which the enzyme is able to change shape slightly and better fit the reactants. The enzyme is like a glove that does not achieve its functional shape until the hand (reactants) moves into place.

What is heat energy?

is a form that flows from a hotter object to a cooler object. Temperature is a measure of how hot or cold a substance is relative to another substance. All other forms of energy can be converted into heat energy. For example, when a moving object comes to rest, its kinetic energy is converted into heat energy by friction. Some of the potential energy of chemical bonds is released as heat energy during chemical reactions. Human body temperature is maintained by heat produced as a by-product of chemical reactions.

What is the pH scale?

is a means of referring to the H+ concentration in a solution. The scale ranges from 0 to 14.

what is an enzyme?

is a protein catalyst that increases the rate at which a chemical reaction proceeds without the enzyme being permanently changed.

What is an electrocardiogram and what does it do?

is a recording of electric currents produced by the heart. These currents can be detected by electrodes on the surface of the body because the ions in the body fluids conduct electric currents.

What is adenosine triphosphate?

is an especially important molecule for storing and providing energy in all living organisms. It consist of adenosine (the sugar ribose with the nitrogenous base adenine) and three phosphate groups.

What is cholesterol?

is an especially important steroid because other steroid molecules are synthesized from it. Steroids derived from cholesterol include bile salts, which increase fat absorption in the intestines, and the reproductive hormones estrogen, progesterone, and testosterone. In addition, cholesterol is an important component of the plasma membrane of all cells in the body. Although high levels of cholesterol in the blood increase the risk for cardiovascular disease, a certain amount of cholesterol is vital for normal function.

What is primary structure of a protein?

is determined by the sequence of the amino acids bound by peptide bonds. The potential number of different protein molecules is enormous because 20 different amino acids exist, and each amino acid can be located at any position along a polypeptide chain. The characteristics of the amino acids in a protein ultimately determine the three-dimensional shape of the protein, and the shape of the protein determines its function. A change in one or a few amino acids in the primary structure can alter protein function, usually making the protein less functional or even nonfunctional.

Ribonucleic acid

is structurally related to DNA, and three types of RNA also play important roles in protein synthesis.

What is cohesion?

is the attraction of water to another water molecule. Examples of cohesion are the surface tension exhibited when water bulges over the top of a full glass without spilling over and when beads of water form on the skin.

What is denaturation?

is the change in shape cause by the breaking of hydrogen bonds. It can be cause by abnormally high temperatures or changes in the pH of body fluids. An everyday example of denaturation is the change in the proteins of egg whites when they are cooked.

What is deoxyribonucleic acid?

is the genetic material of cells, and copies of DNA are transferred from one generation of cells to the next generation.

What is activation energy?

is the minimum amount of energy that the reactants must have to start a chemical reaction.

What is the active site?

is the region of the enzyme that binds reactants and catalyzes their conversion to products

What is a decomposition reaction?

is the reverse of a synthesis reaction--a larger reactant is chemically broken down into two or more smaller products. The decomposition reactions occurring in the body are collectively called catabolism.

What is a dipeptide bond?

is two amino acids bound together by a peptide bond, a tripeptide is three amino acids bound together by peptide bonds, and a polypeptide is many amino acids bound together by peptide bonds.

What would water be like without hydrogen bonds?

it would evaporate at odd temperatures and wouldn't look the same. Hydrogen bonding is essential to water and water is essential to life.

Oxygen

makes up most of our body weight and is the most abundant element in the earth's crust.

What are some examples of monounsaturated fats?

olive and peanut oils, have one double covalent bond between carbon atoms.

Contrast potential and kinetic energy.

potential is stored energy. Kinetic is energy that is moving, muscles contracting.

What are double-ringed bases called?

purines

What are single-ringed bases called?

pyrimidines

What are hydrolysis reactions?

reactions that use water to make new molecules.

What is saturation?

refers to the number of hydrogen atoms in the carbon chain.

What is the quaternary structure?

results from the association of two or more proteins to form a functional unit. The individual proteins are called subunits. Interactions between subunits result in the quaternary structure.

What is mechanical energy?

results from the position or movement objects. Many of the activities of the human body, such as moving a limb, breathing, and circulating blood, involve mechanical energy.

What is acidosis and its side effects?

results if blood pH drops below 7.35, in which case the nervous system becomes depressed and the individual may become disoriented and possibly comatose.

What is Alkalosis?

results if blood pH rises above 7.45. Then the nervous system becomes oveexcitable, and the individual may become extremely nervous or have convulsions.

What is an acidic solution?

solutions with a pH less than 7 are acidic and have a greater concentration of H+ than OH-.

What is potential energy?

stored energy that could do work but is not doing so.

What does antiparallel mean?

that two strands lie side by side but their sugar-phosphate "backbones' extend in opposite directions because of the orientation of their nucleotides.

What are the basic building blocks for proteins?

the 20 amino acid molecules.

What is solubility?

the ability of one substance to dissolve in another-for example, sugar dissolving in water. Charged substances, such as sodium chloride, and polar substances, such as glucose, readily dissolve in water, whereas non polar substances, such as oils, do not.

What is mass?

the amount of matter in an object.

Define energy.

the capacity to do work--that is, to move matter.

What is kinetic energy?

the form of energy that is actually doing work and moving matter.

What is weight?

the gravitational force acting on an object of a given mass.

What is the difference between RNA and DNA

the sugar, ribose is for RNA which is OH and deoxyribose is for DNA which is H Like DNA four different nucleotides make up the RNA molecule, and the nitrogenous bases are the same, except thymine is replaced with uracil. Uracil can bind only to adenine.

How is DNA structured?

two strands of nucleotides joined together to form a twisted, ladder like structure called a double helix. The sides of the ladder are formed by covalent bonds between the deoxyribose molecules and the phosphate groups of adjacent nucleotides. The rungs of the ladder are formed by the nitrogenous bases of the nucleotides of one side connected to the nitrogenous bases of the other side by hydrogen bonds. Each nucleotide of DNA contains one of the nitrogenous bases: adenine, thymine, cytosine, or guanine.