chemical basis of life 1

7/27/2019 Chemical Basis of Life 1

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Chemical Basis of Life

Chapter 2


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Objectives

1. Explain why an understanding of basic chemistry is important in the study oflife processes.

2. Explain the relationship between elements, compounds, atoms, and molecules.

3. List the major elements and major mineral elements found in cytoplasm.

4. Discuss atomic structure and explain how an atom's electron shells influenceits ability to enter into chemical reactions.

5. Compare and contrast the three major types of chemical bonds.

6. List and describe the three basic types of chemical reactions that occur in livingmaterial.

7. Discuss the properties that make water such an important inorganic moleculein living organisms.

8. Discuss the concept of pH and its relationship to acids, bases, and salts in thebody.

9. List the four major groups of organic substances in the body and give

examples and functions of specific types in each group. 10. Distinguish between the four major groups of organic substances by identifying

an important functional group or "building block" unique to each.

11. Define the term bioenergyand identify the most important of the bioenergymolecules.

12. Define or explain the following terms or phrases: atomic number, octet rule,isotope,polymer, electrolyte,polarity, nucleotide, base pair, and high-energy bond.

13. Describe the structure and function of enzymes.


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Elements in Body

26 elements in body

11 are major elements

Table 2-1; page 37

Carbon, oxygen, hydrogen, nitrogen make up

96% of body

Remaining 15 elements are called trace

elements (less than 0.1%)


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Atoms

1805, John Dalton proposed the concept that

matter is composed of atoms

Proton, electron, neutron

Elements are neutral


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Atomic Number and Weight

Elements differ in their chemical and physicalproperties

Different number of protons

Atomic numberis the number of protons Identifies type of element

92 elements occur naturally in nature

110 elements in periodic table

Atomic weight (mass)-mass of a singleatom

#proton + #neutron


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Energy Levels

In chemical reactions outer energy level(shell) participate in forming chemical bonds

Each level; electrons group in pairs

General rule: atom is inert and unable toreact with another atom if outermost level has4 pairs of e- (stable configuration)

If it isnt full-can react (lose, gain or share e-)

Octet rule Holds true for atoms except those with 1 level

and is filled by 2 max e-


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Isotope

Isotopes- contain the same number of

protons but different number of neutrons

Same basic chemical properties and same

atomic number Differ in atomic mass

Hydrogen and Carbon

Radioactive isotope unstable andundergoes nuclear breakdown

Emit nuclear particles and radiation-decay


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Chemical Bonds

Interactions between 2 or more atoms results

in chemical reaction

Gain, lose or share electrons (octet rule)

Result of reactions = molecule

Atoms held together by chemical bonds

Ionic

Covalent hydrogen


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Ionic or Electrovalent Bonds

Gaining or losing electrons

Make ions (positive or negative)


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Covalent Bonds

Share electrons

Can share one or more pairs of electrons

Great significance in body

Major elements almost always share electrons Can be single, double, or triple bonds

Single-1 shared paired

Double-2 shared paired

Triple-3 shared paired


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Hydrogen Bonds

Can exist within or between biologically

important molecules

Do not form new molecules

Much weaker than ionic and covalent bonds

Result from unequal charge distribution on a

molecule

Polar molecules Ex. Water Molecule


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Polar Molecules

Water is electrically neutral

It has a partial positive charge and a partialnegative charge

It has opposite charges at different ends of themolecule

Polar molecules serve to weakly attach thenegative side of one water molecule with the

positive side of an adjacent water moleculeAccounts for many of water unique properties

Important in maintaining the 3D structure ofproteins and nucleic acids


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Chemical Reactions

Involve interactions between atoms and

molecules that involve the formation or

breaking of chemical bonds.

3 basic types Synthesis reactions

Decomposition reactions

Exchange reactions


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Synthesis Reactions

2 or more substances form a differentsubstance

Result in the formation of new bonds

Energy is required

A+B AB

Occurs often in body

EX: cells combine amino acids to form

proteins EX: body synthesizes new tissue in wound

repair


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Decomposition Reactions

Result in breakdown of a complex substance

into two or more simpler substances

Chemical bonds are broken down and energy

is released Can be release as heat, or captured for

storage and future use

AB A + B + Energy


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Exchange Reactions

Permits two different reactants to exchange

components and form two new products

AB + CD AD + CB

Break down two compounds and synthesizetwo new compounds


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Reversible Reactions

Proceed in both directions

Many synthesis, decompositions, and

exchange reactions are reversible

An arrow pointing in both directions representreversible reactions

A + B AB


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Organic and Inorganic Compounds

Organic C-C and C-H bonds

Larger and more complex

Functional group-specialized arrangements

attached to C


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Inorganic-Water

Bodys most abundant and important compound

Properties of Water

Polarity= allows water to act as effective solvent;

ionizes substances in solution

The solvent allows for transportation of essential

materials throughout body

High specific heat-lose/gain large amounts of heat with

little change to temperature

High heat of vaporization-water requires absorption ofsignificant amounts of heat to change water from a liqid

to a gas


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Inorganic-Oxygen and Carbon Dioxide

Closely related to cellular respiration

Oxygen-required to complete decomposition

reactions necessary for the release of energy

in the body Carbon Dioxide-produced as a waste product

and also helps maintain the appropriate acid-

base balance in body


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Inorganic-Electrolytes

Large group of inorganic molecules

Acids, bases, salts

Substance dissociate in solution to form ions

Positively charged ions are cations;

negatively charged ions are anions


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Acids and Bases

Common and important chemical substancesthat are chemical opposites

Acids

Release a hydrogen ion (H+) within solution(proton donor)

Level of acidity depends on the # of hydrogen ions

a particular acid will release

Bases Dissociate to yield hydroxide ions (OH-) or

other electrolytes that combine with hydrogen

ions

Proton acceptors


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pH Scale

Measuring acidity and alkalinity (fig 2-12)

1. pH indicates the degree of acidity or

alkalinity of a solution

2. pH of 7 indicates neutrality (H+ = OH-); pH

of less than 7 indicates acid; pH greater than7 indicates alkalinity


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Buffers

1. maintains the constancy of the pH

2. minimize changes in the concentrations of

H+ and OH-

3. act as a reservoir for hydrogen ions


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Salts (Table 2-3)

1. Compound that results from chemical

interaction of an acid and a base

2. Reaction between an acid and a base toform a salt and water is called a neutralization

reaction


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Organic Molecules (fig 2-13; table 2-4)

Organic describes compounds that contain

C-C or C-H bonds

1. Carbohydrates

2. Proteins

3. Lipids

4. Nucleic Acids


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Carbohydrates

Contains carbon, hydrogen, and oxygen

Commonly called sugars and starches

1. Monosaccharides

Simple sugars with short carbon chains; thosewith 6 carbons are hexoses, five-pentoses

Fig 2-14

2. Disaccharides and polysaccharids

Two or more simple sugars that are bondedtogether through a synthesis reaction

Fig 2-15


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Proteins

Most abundant organic compound

Chainlike polymers

Two broad categories

Structural proteins form the structures of thebody

Functional proteins cause chemical changes

in the molecules

Shape of protein molecules determines

function


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Amino Acids (fig 2-16 thru 2-18)

Building blocks of proteins

Essential amino acids

8 amino acids that cant be produced by body

Nonessential amino acids

12 a.a. can be produced in body

Amino acids consist

Carbon atom

Hydrogen atom

Amino group Carboxyl group

Side chain


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Levels of protein structure (fig 2-19)

4 levels of protein organization 1. Primary

Number, kind, and sequence of a.a that make uppolypeptide chain

2. Secondary- Polypeptide is coiled or bent into pleated sheets

stabilized by hydrogen bonds

3. Tertiary Secondary structure can be further twisted, globular

shape; coils touch in many places and are welded bycovalent and hydrogen bonds

4. Quaternary- Highest level; protein contains more than one

polypeptide chain


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Lipids (table 2-6)

Water-insoluble organic molecules that are

critically important biological compounds

Major roles

Energy source Structural role

Integral parts of cell membranes


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Triglycerides

Types of fatty acids

Saturated fatty acids- all available bonds are

filled

Unsaturated fatty acids-one or more doublebonds

Formed by a dehydration synthesis


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Phospholipids (2-22)

Fat compounds similar to triglyceride

One end of the phospholipid is water soluble;

the other end is fat soluble

Can join two different chemical environments


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Steroids (2-23)

Main component in steroid nucleus

Involved in many structural and functions

roles


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Prostaglandins

Commonly called tissue hormones

Produced by cell membranes throughout the

body

Effects are many and varied: however, theyare released in response to a specific

stimulus and are then inactivatid


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Prostaglandins

Crucial role:

Regulating effects of several hormones

Influence blood pressure

Secretion of digestive juices Enhance body immune system and

inflammatory response

Blood clotting

respiration


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Prostaglandins-medicine

Use of prostaglandins and prostaglandin

inhibitors as drugs is exciting and rapidly

growing area

Treatment of disease, symptoms, medicalconditions

Relieving menstrual cramps

Asthma

High blood pressure

ulcers


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Nucleic Acids

DNA-deoxyribonucleic acid Composed of deoxyribonucleotides-pentose

sugar, phophate group, nitrogenous base

Two long chains of deoxyribonucleotidescoiled in double helix (fig 2-24)

Alternating deoxyribose and phophateunits=backbone of chains

Base pairs hold 2 chains of DNA together

Specific sequence of more than 100 millionbase pairs = 1 human DNA molecule

DNA functions as molecule of heredity


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Nucleic Acids

RNA ribonucleic acids

Composed of pentose sugar, phosphate

group, nitrogenous base

Nitrogenous bases for RNA are A, U. G, C


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Biomolecules combined

Large molecules can be joined to form larger

molecules

1. gives molecules completely different

function 2. names of combined molecules tell what is

in them

Base word-which component is dominant

Prefix-component in lesser amount


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Examples

Adenosine triphoshate (ATP)

Lipoproteins

Glycoproteins

Table 2-4


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Metabolism

All chemical reactions that occur in body cells

Catabolism

Anabolism


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Catabolism

Chemical reactions that break down complex

compounds into simpler ones and release

energy

Hydrolysis is a common catabolic reaction

More than half the energy released is put

back into storage as ATP, which is then used

to do cellular work

Fig 2-26


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Anabolism

Chemical reactions that join simple molecules

together to form more complex molecules

Chemical reaction responsible for anabolism

is dehydration synthesis


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ATP

Adenosine triphosphate

Ribose, adenine, three phosphates

High-energy bonds between phosphate groups

Break bonds=release of energy (catabolic)

Energy stored in ATP is used to do the bodys work

Energy currency of cells

ATP split into ADP and a phosphate group

If ATP is depleted during prolonged exercise, ADP isused for energy

chemical basis of life 1

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