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The Chemical Level of Organization

PowerPoint ® Lecture Presentations prepared by Jason LaPres Lone Star College—North Harris

An Introduction to the Chemical Level of Organization

•

Learning Outcomes

•

2-1

Describe an atom and how atomic structure affects interactions between atoms.

•

2-2

Compare the ways in which atoms combine to form molecules and compounds.

•

2-3

Distinguish among the major types of chemical reactions that are important for studying physiology.

•

2-4

Describe the crucial role of enzymes in metabolism.

An Introduction to the Chemical Level of Organization

•

Learning Outcomes

•

2-5

Distinguish between organic and inorganic compounds.

•

2-6

Explain how the chemical properties of water make life possible.

•

2-7

Discuss the importance of pH and the role of buffers in body fluids.

•

2-8

Describe the physiological roles of inorganic compounds.

•

2-9

Discuss the structures and functions of carbohydrates.

An Introduction to the Chemical Level of Organization

•

Learning Outcomes

• •

2-10

Discuss the structures and functions of lipids.

2-11

Discuss the structures and functions of proteins.

•

2-12

Discuss the structures and functions of nucleic acids.

•

2-13

Discuss the structures and functions of high energy compounds.

•

2-14

Explain the relationship between chemicals and cells.

An Introduction to the Chemical Level of Organization

•

Chemistry

• Is the science of change • Topics of this chapter include: • The structure of atoms • The basic chemical building blocks • How atoms combine to form increasingly complex structures © 2012 Pearson Education, Inc.

2-1 Atoms and Atomic Structure

•

Matter

• Is made up of

atoms

2-1 Atoms and Atomic Structure

•

Subatomic Particles

•

Proton

• Positive charge, 1 mass unit •

Neutron

• Neutral, 1 mass unit •

Electron

2-1 Atoms and Atomic Structure

•

Atomic Structure

•

Atomic number

• Number of protons • Nucleus • Contains protons and neutrons •

Electron cloud

Figure 2-1 The Structure of Hydrogen Atoms Electron shell Hydrogen-1 mass number: 1 A typical hydrogen nucleus contains a proton and no neutrons.

Hydrogen-2, deuterium mass number: 2 A deuterium ( 2 H) nucleus contains a proton and a neutron.

Hydrogen-3, tritium mass number: 3 A tritium ( 3 H) nucleus contains a pair of neutrons in addition to the proton.

Table 2-1 Principal Elements in the Human Body

2-1 Atoms and Atomic Structure

•

Elements and Isotopes

•

Elements

2-1 Atoms and Atomic Structure

•

Elements and Isotopes

•

Isotopes

are the specific version of an element based on its

mass number

2-1 Atoms and Atomic Structure

•

Atomic Weights

• Exact mass of all particles • Measured in

moles

2-1 Atoms and Atomic Structure

•

Electrons and Energy Levels

• Electrons in the electron cloud determine the reactivity of an atom • The electron cloud contains shells, or energy levels that hold a maximum number of electrons • Lower shells fill first • Outermost shell is the

valence shell,

Figure 2-2 The Arrangement of Electrons into Energy Levels Hydrogen, H Atomic number: 1 Mass number: 1 1 electron The first energy level can hold a maximum of two electrons.

Helium, He Atomic number: 2 Mass number: 4 (2 protons



2 neutrons) 2 electrons

Figure 2-2 The Arrangement of Electrons into Energy Levels The second and third energy levels can each contain up to 8 electrons.

Lithium, Li Atomic number: 3 Mass number: 6 (3 protons



3 neutrons) 3 electrons Neon, Ne Atomic number: 10 Mass number: 20 (10 protons



10 neutrons) 10 electrons

2-2 Molecules and Compounds

• • •

Chemical Bonds

Involve the sharing, gaining, and losing of electrons in the valence shell Three major types of chemical bonds

Ionic bonds

• Attraction between

cations

(electron donor) and

anions

(electron acceptor)

Covalent bonds

• Strong electron bonds involving shared electrons

Hydrogen bonds

2-2 Molecules and Compounds

•

Chemical Bonds

• Form molecules and/or compounds •

Molecules

• Two or more atoms joined by strong bonds •

Compounds

• Two or more atoms

OF DIFFERENT ELEMENTS

2-2 Molecules and Compounds

•

Ionic Bonds

• One atom —

the electron donor

—loses one or more electrons and becomes a cation, with a positive charge • Another atom —

the electron acceptor

Figure 2-3a The Formation of Ionic Bonds Formation of ions Sodium atom Attraction between opposite charges Sodium ion (Na



) Formation of an ionic compound Sodium chloride (NaCl) Chlorine atom Chloride ion (Cl



) Formation of an ionic bond.

1 A sodium (Na) atom loses an electron, which is accepted by a chlorine (Cl) atom. Because the sodium (Na



) and chloride (Cl



2 ) ions have opposite charges, they are attracted to one another. The association of sodium and chloride ions forms the ionic compound sodium chloride.

Figure 2-3b The Formation of Ionic Bonds Chloride ions (Cl



) Sodium ions (Na



)

Sodium chloride crystal. Large numbers of sodium and chloride ions form a crystal of sodium chloride (table salt).

2-2 Molecules and Compounds

•

Covalent Bonds

• Involve the sharing of pairs of electrons between atoms • One electron is donated by each atom to make the pair of electrons • Sharing one pair of electrons is a

single covalent bond

• Sharing two pairs of electrons is a

double covalent bond

Figure 2-4 Covalent Bonds in Four Common Molecules Molecule Electron Shell Model and Structural Formula Hydrogen (H 2 ) H



H O



O Oxygen (O 2 ) Carbon dioxide (CO 2 ) Nitric oxide (NO)



O N



2-2 Molecules and Compounds

•

Covalent Bonds

•

Nonpolar covalent bonds

• Involve

equal

sharing of electrons because atoms involved in the bond have equal pull for the electrons •

Polar covalent bonds

• Involve the

unequal

sharing of electrons because one of the atoms involved in the bond has a disproportionately strong pull on the electrons • Form

polar molecules

Figure 2-5 Polar Covalent Bonds and the Structure of Water Hydrogen atom Hydrogen atom Oxygen atom Hydrogen atom Oxygen atom 2

2-2 Molecules and Compounds

•

Hydrogen Bonds

• Bonds between adjacent molecules, not atoms • Involve slightly positive and slightly negative portions of polar molecules being attracted to one another • Hydrogen bonds between H 2 O molecules cause

surface tension

2-2 Molecules and Compounds

•

States of Matter

•

Solid

• Constant volume and shape •

Liquid

• Constant volume but changes shape •

Gas

2-2 Molecules and Compounds

•

Molecular Weights

• The

molecular weight

2-3 Chemical Reactions

•

In a

Chemical Reaction

• Either new bonds are formed or existing bonds are broken •

Reactants

• Materials going into a reaction •

Products

• Materials coming out of a reaction •

Metabolism

Figure 2-7 Chemical Notation Atoms The symbol of an element indicates one atom of that element. A number preceding the symbol of an element indicates more than one atom of that element.

VISUAL REPRESENTATION CHEMICAL NOTATION one atom of hydrogen two atoms of hydrogen one atom of oxygen two atoms of oxygen one atom of hydrogen one atom of oxygen two atoms of hydrogen two atoms of oxygen

Figure 2-7 Chemical Notation Molecules A subscript following the symbol of an element indicates a molecule with that number of atoms of that element.

VISUAL REPRESENTATION CHEMICAL NOTATION hydrogen molecule composed of two hydrogen atoms oxygen molecule composed of two oxygen atoms water molecule composed of two hydrogen atoms and one oxygen atom hydrogen molecule oxygen molecule water molecule

Figure 2-7 Chemical Notation Reactions In a description of a chemical reaction, the participants at the start of the reaction are called reactants, and the reaction generates one or more products. An arrow indicates the direction of the reaction, from reactants (usually on the left) to products (usually on the right). In the following reaction, two atoms of hydrogen combine with one atom of oxygen to produce a single molecule of water. VISUAL REPRESENTATION CHEMICAL NOTATION Chemical reactions neither create nor destroy atoms; they merely rearrange atoms into new combinations. Therefore, the numbers of atoms of each element must always be the same on both sides of the equation for a chemical reaction. When this is the case, the equation is balanced.

Balanced equation Unbalanced equation

Figure 2-7 Chemical Notation Ions A superscript plus or minus sign following the symbol of an element indicates an ion. A single plus sign indicates a cation with a charge of



1. (The original atom has lost one electron.) A single minus sign indicates an anion with a charge of



1. (The original atom has gained one electron.) If more than one electron has been lost or gained, the charge on the ion is indicated by a number preceding the plus or minus sign.

VISUAL REPRESENTATION CHEMICAL NOTATION sodium ion the sodium atom has lost one electron chloride ion the chlorine atom has gained one electron calcium ion the calcium atom has lost two electrons A sodium atom becomes a sodium ion Electron lost Sodium atom (Na) Sodium ion (Na



) sodium ion chloride ion calcium ion

2-3 Chemical Reactions

•

Basic Energy Concepts

• • • • •

Energy

• The power to do work

Work

• A change in mass or distance

Kinetic energy

• Energy of motion

Potential energy

2-3 Chemical Reactions

•

Types of Chemical Reactions

Decomposition reaction

(

catabolism

)

Synthesis reaction

(

anabolism

)

Exchange reaction 4.

Reversible reaction

2-3 Chemical Reactions

•

Decomposition Reaction

(

Catabolism

)

• Breaks chemical bonds • AB  A + B • Hydrolysis A-B + H 2 O  A-H + HO-B •

Synthesis Reaction

(

Anabolism

)

• Forms chemical bonds • A + B  AB • Dehydration synthesis (

condensation reaction

2-3 Chemical Reactions

•

Exchange Reaction

•

Involves decomposition first, then synthesis

•

AB + CD



AD + CB

2-3 Chemical Reactions

•

Reversible Reaction

• A + B  AB • At equilibrium the amounts of chemicals do not change even though the reactions are still occurring • Reversible reactions seek equilibrium, balancing opposing reaction rates • Add or remove reactants • Reaction rates adjust to reach a new equilibrium © 2012 Pearson Education, Inc.

2-4 Enzymes

•

Chemical Reactions

• In cells cannot start without help •

Activation energy

is the amount of energy needed to get a reaction started •

Enzymes

are protein

catalysts

Figure 2-8 The Effect of Enzymes on Activation Energy Reactants Activation energy required Without enzyme With enzyme Stable product Progress of reaction

2-4 Enzymes

•

Exergonic

(Exothermic) Reactions

• Produce more energy than they use •

Endergonic

(Endothermic) Reactions

2-5 Organic and Inorganic Compounds

• • • •

Nutrients

• Essential molecules obtained from food

Metabolites

• Molecules made or broken down in the body

Inorganic Compounds

• Molecules not based on carbon and hydrogen • Carbon dioxide, oxygen, water, and inorganic acids, bases, and salts

Organic Compounds

2-6 Properties of Water

•

Water

• Accounts for up to two-thirds of your total body weight • A

solution

is a uniform mixture of two or more substances • It consists of a

solvent

, or medium, in which atoms, ions, or molecules of another substance, called a

solute

2-6 Properties of Water

•

Solubility

• Water’s ability to dissolve a

solute

in a

solvent

to make a

solution

•

Reactivity

• Most body chemistry occurs in water •

High Heat Capacity

• Water’s ability to absorb and retain heat •

Lubrication

2-6 Properties of Water

•

The Properties of Aqueous Solutions

• Ions and polar compounds undergo ionization, or

dissociation

in water • Polar water molecules form

hydration spheres

Figure 2-9 The Activities of Water Molecules in Aqueous Solutions Negative pole H Positive pole Cl



Hydration spheres Na



Glucose molecule

Figure 2-9a The Activities of Water Molecules in Aqueous Solutions Negative pole

H Positive pole Water molecule. In a water molecule, oxygen forms polar covalent bonds with two hydrogen atoms.

Because both hydrogen atoms are at one end of the molecule, it has an uneven distribution of charges, creating positive and negative poles.

Figure 2-9b The Activities of Water Molecules in Aqueous Solutions Hydration spheres Cl



Sodium chloride in solution. Ionic compounds, such as sodium chloride, dissociate in water as the polar water molecules break the ionic bonds in the large crystal structure. Each ion in solution is surrounded by water molecules, creating hydration spheres.

Figure 2-9c The Activities of Water Molecules in Aqueous Solutions Glucose molecule

Glucose in solution.

Hydration spheres also form around an organic molecule containing polar covalent bonds. If the molecule binds water strongly, as does glucose, it will be carried into solution —in other words, it will dissolve. Note that the molecule does not dissociate, as occurs for ionic compounds.

Table 2-2 Important Electrolytes that Dissociate in Body Fluids

2-6 Properties of Water

•

The Properties of Aqueous Solutions

• Electrolytes and body fluids •

Electrolytes

2-6 Properties of Water

• The Properties of Aqueous Solutions • Hydrophilic and hydrophobic compounds •

Hydrophilic

•

hydro

- = water,

philos

= loving • Interacts with water • Includes ions and polar molecules •

Hydrophobic

•

phobos

2-6 Properties of Water

•

Colloids and Suspensions

•

Colloid

• A solution of very large organic molecules • For example, blood plasma •

Suspension

• A solution in which particles settle (sediment) • For example, whole blood •

Concentration

2-7 pH and Homeostasis

•

pH

• The concentration of hydrogen ions (H + ) in a solution •

Neutral pH

• A balance of H + and OH  • Pure water = 7.0

2-7 pH and Homeostasis

•

Acidic

pH Lower Than 7.0 • High H + concentration • Low OH  concentration •

Basic

(or

alkaline

) pH Higher Than 7.0

• Low H + concentration • High OH  concentration • pH of Human Blood • Ranges from 7.35 to 7.45

2-7 pH and Homeostasis

•

pH Scale

• Has an

inverse

relationship with H + concentration • More H + ions mean

lower

pH, less H + ions mean

higher

Figure 2-10 pH and Hydrogen Ion Concentration 1 mol/L hydrochloric acid Stomach acid Beer, vinegar, wine, pickles Tomatoes, grapes Urine Saliva, milk Blood Ocean Pure water Eggs water Household bleach Household ammonia 1 mol/L sodium hydroxide Oven cleaner Extremely acidic pH [H



] 0 10 0 (mol/L) 1 10



1 2 10



2 Increasing concentration of H



3 10



3 4 10



4 5 10



5 6 10



6 Neutral 7 10



7 Increasing concentration of OH



Extremely basic 8 10



8 9 10



9 10 10



10 11 10



11 12 10



12 13 10



13 14 10



2-8 Inorganic Compounds

• • •

Acid

• • • A solute that adds hydrogen ions to a solution

Proton donor Strong acids

dissociate completely in solution

Base

• • • A solute that removes hydrogen ions from a solution

Proton acceptor Strong bases

dissociate completely in solution

Weak Acids

and

Weak Bases

2-8 Inorganic Compounds

•

Salts

2-8 Inorganic Compounds

•

Buffers and pH Control

•

Buffers

• Weak acid/salt compounds • Neutralize either strong acid or strong base • Sodium bicarbonate is very important in humans • Antacids • Basic compounds that neutralize acid and form a salt • Alka-Seltzer, Tums, Rolaids, etc.

2-9 Carbohydrates

•

Organic Molecules

• Contain H, C, and usually O • Are covalently bonded • Contain functional groups that determine chemistry •

Carbohydrates

Table 2-3 Important Functional Groups of Organic Compounds

2-9 Carbohydrates

•

Carbohydrates

• Contain carbon, hydrogen, and oxygen in a 1:2:1 ratio •

Monosaccharide

—

simple sugar

•

Disaccharide

— two sugars •

Polysaccharide

2-9 Carbohydrates

• • •

Monosaccharides

• • Simple sugars with 3 to 7 carbon atoms

Glucose

fructose

, galactose

Disaccharides

• Two simple sugars condensed by dehydration synthesis •

Sucrose

, maltose

Polysaccharides

• Many monosaccharides condensed by dehydration synthesis •

Glycogen

starch, cellulose

Figure 2-12a The Formation and Breakdown of Complex Sugars Glucose Fructose DEHYDRATION SYNTHESIS Sucrose

Figure 2-12a The Formation and Breakdown of Complex Sugars DEHYDRATION SYNTHESIS Glucose Fructose Formation of the disaccharide sucrose through dehydration synthesis.

Figure 2-12a The Formation and Breakdown of Complex Sugars DEHYDRATION SYNTHESIS Sucrose During dehydration synthesis, two molecules are joined by the removal of a water molecule.

Figure 2-12b The Formation and Breakdown of Complex Sugars Sucrose HYDROLYSIS Glucose Fructose

Figure 2-12b The Formation and Breakdown of Complex Sugars HYDROLYSIS Sucrose Breakdown of sucrose into simple sugars by hydrolysis.

Figure 2-12b The Formation and Breakdown of Complex Sugars HYDROLYSIS Glucose Fructose Hydrolysis reverses the steps of dehydration synthesis; a complex molecule is broken down by the addition of a water molecule.

Figure 2-13 The Structure of the Polysaccharide Glycogen Glucose molecules

Table 2-4 Carbohydrates in the Body

2-10 Lipids

•

Lipids

• Mainly hydrophobic molecules such as

fats, oils, and waxes

• Made mostly of carbon and hydrogen atoms • Include: •

Fatty acids

•

Eicosanoids

•

Glycerides

•

Steroids

•

Phospholipids and glycolipids

2-10 Lipids

•

Fatty Acids

• Long chains of carbon and hydrogen with a

carboxyl group

(COOH) at one end • Are relatively nonpolar,

except

the carboxyl group • Fatty acids may be: •

Saturated

with hydrogen (no covalent bonds) •

Unsaturated

(one or more double bonds) •

Monounsaturated

= one double bond •

Polyunsaturated

Figure 2-14b Fatty Acids Saturated Unsaturated

A fatty acid is either saturated (has single covalent bonds only) or unsaturated (has one or more double covalent bonds). The presence of a double bond causes a sharp bend in the molecule.

2-10 Lipids

•

Eicosanoids

• Derived from the fatty acid called

arachidonic acid

•

Leukotrienes

• Active in immune system •

Prostaglandins

•

Local hormones

2-10 Lipids

• • •

Glycerides

Fatty acids attached to a

glycerol

molecule

• •

Triglycerides

are the three fatty-acid tails

Also called

triacylglycerols

neutral fats

Have three important functions 1.

Energy source 2.

Insulation 3.

Figure 2-16 Triglyceride Formation Glycerol Fatty Acid 1 Fatty acids Saturated Fatty Acid 2 Fatty Acid 3 Saturated Unsaturated DEHYDRATION SYNTHESIS HYDROLYSIS

Triglyceride

2-10 Lipids

•

Steroids

• Four rings of carbon and hydrogen with an assortment of functional groups • Types of steroids: •

Cholesterol

• Component of plasma (cell) membranes •

Estrogens

and

testosterone

• Sex hormones • •

Corticosteroids

and

calcitriol

• Metabolic regulation

Bile salts

Figure 2-17 Steroids Cholesterol Estrogen

Testosterone

2-10 Lipids

•

Phospholipids

and

Glycolipids

• Diglycerides attached to either a

phosphate group

(

phospho

lipid) or a sugar (

glyco

lipid) • Generally, both have hydrophilic heads and hydrophobic tails and are

structural lipids

Figure 2-18b Phospholipids and Glycolipids Carbohydrate

Fatty acids In a glycolipid, a carbohydrate is attached to a diglyceride.

Table 2-5 Representative Lipids and Their Functions in the Body

2-11 Proteins

•

Proteins

• Are the most abundant and important organic molecules • Contain basic elements • Carbon (C), hydrogen (H), oxygen (O), and nitrogen (N) • Basic building blocks • 20 amino acids © 2012 Pearson Education, Inc.

2-11 Proteins

•

Seven Major Protein Functions

Support

•

Structural proteins 2.

Movement

•

Contractile proteins 3.

Transport

•

Transport

(carrier)

proteins 4.

Buffering

• Regulation of pH

Metabolic Regulation

•

Enzymes 6.

Coordination and Control

•

Hormones 7.

Defense

•

Antibodies

2-11 Proteins

• • •

Protein Structure

Long chains of

amino acids

Five components of amino acid structure 1.

Central carbon atom 2.

Hydrogen atom

Amino group

( —NH 2 )

Carboxyl group

( —COOH) 5.

Variable

side chain

R group

Figure 2-19 Amino Acids

Structure of an Amino Acid

Amino group Central carbon Carboxyl group R group (variable side chain of one or more atoms)

2-11 Proteins

•

Hooking Amino Acids Together

• Requires a dehydration synthesis between: • The amino group of one amino acid and the carboxyl group of another amino acid • Forms a

peptide bond

• Resulting molecule is a

peptide

Figure 2-20 The Fomation of Peptide Bonds Peptide Bond Formation Glycine (gly) Alanine (ala) DEHYDRATION SYNTHESIS HYDROLYSIS

Peptide bond

2-11 Proteins

• Protein Shape •

Primary structure

• The sequence of amino acids along a polypeptide •

Secondary structure

• Hydrogen bonds form spirals or pleats •

Tertiary structure

• Secondary structure folds into a unique shape •

Quaternary structure

Figure 2-21 Protein Structure A1 A2 A3 A4 A5 A6 Linear chain of amino acids A7 A8 A9 A1 A1 A2 Hydrogen bond A6 A3 A5 A7 A9 Hydrogen bond OR A10 A9 A11 A2 A8 A3 A7 A4 A6 A12 A13 A14 A5 Alpha-helix Pleated sheet

Heme units OR Hemoglobin (globular protein) Keratin or collagen (fibrous protein)

Figure 2-21ab Protein Structure A1 A2 A3 A4 A5 A6 Linear chain of amino acids Primary structure. The primary structure of a polypeptide is the sequence of amino acids (A1, A2, A3, and Hydrogen so on) along bond its length.

A2 A6 A1 A3 A5 A7 A9 A7 A8 Alpha-helix Secondary structure. Secondary structure is primarily the result of hydrogen bonding along the length of the polypeptide chain. Such bonding often produces a simple spiral (an alpha-helix) or a flattened arrangement known as a pleated sheet.

Figure 2-21ab Protein Structure A1 A2 A3 A4 A5 A6 A7 A8 Linear chain of amino acids Primary structure. The primary structure of a polypeptide is the sequence of amino acids (A1, A2, A3, and so on) along its length.

A9 A1 Hydrogen bond A10 A9 A11 A2 A8 A3 A7 A4 A6 A12 A13 A14 A5 Pleated sheet Secondary structure. Secondary structure is primarily the result of hydrogen bonding along the length of the polypeptide chain. Such bonding often produces a simple spiral (an alpha-helix) or a flattened

arrangement known as a pleated sheet.

2012 Pearson Education, Inc.

Figure 2-21cd Protein Structure Heme units Tertiary structure. Tertiary structure is the coiling and folding of a polypeptide. Hemoglobin (globular protein) Quaternary structure. Quaternary structure develops when separate polypeptide subunits interact to form a larger molecule. A single hemoglobin molecule contains four globular subunits.

Figure 2-21cd Protein Structure Heme units Tertiary structure. Tertiary structure is the coiling and folding of a polypeptide. Keratin or collagen (fibrous protein) Quaternary structure. Quaternary structure develops when separate polypeptide subunits interact to form a larger molecule.

2-11 Proteins

•

Fibrous Proteins

• Structural sheets or strands •

Globular Proteins

• Soluble spheres with active functions • Protein function is based on shape •

Shape is based on sequence of amino acids

Figure 2-21d Protein Structure Heme units OR Hemoglobin (globular protein) Keratin or collagen (fibrous protein)

2-11 Proteins

•

Enzyme Function

• Enzymes are catalysts • Proteins that lower the activation energy of a chemical reaction • Are not changed or used up in the reaction • Enzymes also exhibit:

Specificity

— will only work on limited types of

substrates

Saturation Limits

— by their concentration

Regulation

Figure 2-22 A Simplified View of Enzyme Structure and Function Substrates bind to active site of enzyme

Figure 2-22 A Simplified View of Enzyme Structure and Function Once bound to the active site, the substrates are held together and their interaction facilitated

Enzyme-substrate complex

Figure 2-22 A Simplified View of Enzyme Structure and Function Substrate binding alters the shape of the enzyme, and this change promotes product formation

Figure 2-22 A Simplified View of Enzyme Structure and Function Product detaches from enzyme; entire process can now be repeated

2-11 Proteins

•

Cofactors and Enzyme Function

•

Cofactor

• An ion or molecule that binds to an enzyme before substrates can bind •

Coenzyme

2-11 Proteins

•

Effects of Temperature and pH on Enzyme Function

•

Denaturation

2-11 Proteins

•

Glycoproteins and Proteoglycans

•

Glycoproteins

• Large protein + small carbohydrate • Includes enzymes, antibodies, hormones, and

mucus

production •

Proteoglycans

2-12 Nucleic Acids

•

Nucleic Acids

• Are large organic molecules, found in the nucleus, which

store and process information

at the molecular level •

Deoxyribonucleic acid (DNA)

• Determines inherited characteristics • Directs protein synthesis • Controls enzyme production • Controls metabolism •

Ribonucleic acid (RNA)

2-12 Nucleic Acids

• • •

Structure of Nucleic Acids

DNA and RNA are strings of nucleotides • •

Nucleotides

Are the building blocks of DNA and RNA Have three molecular parts 1.

pentose

sugar (

deoxyribose

ribose

) 2.

Phosphate group

Nitrogenous base

Figure 2-23a Nucleotides and Nitrogenous Bases

Generic nucleotide

The nitrogenous base may be a purine or a pyrimidine.

Sugar Phosphate group

Nitrogenous base

Figure 2-23b Nucleotides and Nitrogenous Bases

Purines

Adenine

Guanine

Figure 2-23c Nucleotides and Nitrogenous Bases Pyrimidines Cytosine Thymine (DNA only)

Uracil (RNA only)

2-12 Nucleic Acids

• • • • DNA and RNA • DNA is double stranded, and the bases form hydrogen bonds to hold the DNA together Sometimes RNA can bind to itself but is usually a single strand DNA forms a twisting double helix

Complementary base pairs

Figure 2-24 The Structure of Nucleic Acids Phosphate group Deoxyribose Adenine Thymine Hydrogen bond DNA strand 1 DNA strand 2 RNA molecule. Cytosine Guanine DNA molecule.

2-12 Nucleic Acids

•

Types of RNA

•

Messenger RNA (mRNA)

•

Transfer RNA (tRNA)

•

Ribosomal RNA (rRNA)

Table 2-6 Comparison of RNA with DNA

2-13 High-Energy Compounds

•

Nucleotides Can Be Used to Store Energy

• Adenosine diphosphate (ADP) • Two phosphate groups;

di-

= 2 • Adenosine triphosphate (ATP) • Three phosphate groups;

tri-

= 3 •

Phosphorylation

• Adding a phosphate group to ADP with a high-energy bond to form the high-energy compound ATP •

Adenosine triphosphatase (ATPase)

Figure 2-25 The Structure of ATP Adenine Ribose Phosphate Phosphate Phosphate Adenosine High-energy bonds Adenosine monophosphate (AMP) Adenosine diphosphate (ADP) Adenosine triphosphate (ATP) Adenine

Ribose Adenosine Phosphate groups

2-14 Chemicals and Cells

•

Chemicals and Cells

• Biochemical building blocks form functional units called cells •

Metabolic turnover

lets your body grow, change, and adapt to new conditions and activities • Your body recycles and renews all of its chemical components at intervals ranging from minutes to years © 2012 Pearson Education, Inc.

Table 2-7 Classes of Inorganic and Organic Compounds

Table 2-8 Turnover Times