© 2014 pearson education, inc. objectives 1.define/describe an atom and its subatomic particles...

© 2014 Pearson Education, Inc.

OBJECTIVESOBJECTIVES

1.1. Define/describe an atom and its subatomic particlesDefine/describe an atom and its subatomic particles

2.2. Describe differences between atoms, isotopes, and Describe differences between atoms, isotopes, and ionsions

3.3. Understand how and why atoms form moleculesUnderstand how and why atoms form molecules

4.4. Know the attributes of waterKnow the attributes of water

5.5. Understand what is pH and what is a bufferUnderstand what is pH and what is a buffer

6.6. Describe the four organic molecules and their Describe the four organic molecules and their functionfunction

Chapter 2:Chapter 2:The Chemistry of Living ThThe Chemistry of Living Thingsings


All Matter Consists of Elements

Chemistry: the study of matter Matter

– Anything that has mass and occupies space

– Composed of elements Elements

– Cannot be broken down to a simpler form

– Periodic table of elements—lists all known elements


Atoms—Smallest Functional Units of an Element

Atoms consist of– Nucleus (central core)

– Protons– positive charge– have mass

– Neutrons– no charge– have mass

– Shells (surrounding nucleus)– Electrons

– negative charge– no discernable mass


Figure 2.3Electron

a) Hydrogen1 proton

1 electron

Proton

Shell

Neutron

Nucleus

b) Oxygen8 protons8 neutrons8 electrons in 2 shells

c) Sodium11 protons11 neutrons11 electrons

in 3 shells


More About Atoms

Atomic symbol: one or two letters– Na: sodium– O: oxygen

Atomic number– Number of protons, always the same number for any

atom of a particular element Atomic mass

– Roughly equal to number of protons plus neutrons In an electrically neutral atom

– Number of protons number of electrons


Isotopes Have a Different Number of Neutrons

Isotopes are atoms of the same element that have a different number of neutrons– They will have a different atomic mass

Unstable isotopes are called radioisotopes: they give off:– Energy in the form of radiation, particles

Some radioisotopes have scientific and medical uses– Diagnostic imaging– Cancer treatment– Power supply for implants such as cardiac

pacemakers


Energy Fuels Life’s Activities

Energy: the capacity to do work Potential energy: stored energy Kinetic energy: energy in motion, doing work Potential energy can be transformed into kinetic

energy


Figure 2.4

Potential energy islocked up in the chemical bonds ofenergy-storagemolecules in GregLouganis’ tissues.

Kinetic energy is energy in motion.


Energy Fuels Life’s Activities

Electrons have potential energy– Each shell corresponds to a specific level of potential

energy

– Shells that are farther from the nucleus contain electrons with more potential energy

Atoms are most stable when their outermost shell is full

Atoms will interact with other atoms to fill their outermost shells (rule of eight)


Chemical Bonds Link Atoms to Form Molecules

Chemical bonds: attractive forces holding atoms together

Kinds of chemical bonds– Covalent bonds

– Ionic bonds

– Hydrogen bonds


Covalent Bonds Involve Sharing Electrons

Covalent bonds form when atoms share electrons Very strong bonds Nonpolar covalent bonds: electrons are shared

equally– H2

– O2

Polar covalent bonds: electrons are NOT shared equally– H2O: The oxygen has a stronger pull on the shared

electrons than the hydrogen does


Figure 2.5

Hydrogen(H2)

Oxygen(O2)

Water(H2O)

Single covalent bond

Double covalent bond

Two single covalent bonds

Structural representationStructural formula with covalent bond

Written formula

H H

H

H

O O

O


Ionic Bonds Occur Between Oppositely Charged Ions

Ion: an electrically charged atom or molecule Positively charged ion: forms if an atom or molecule

loses electrons Negatively charged ion: forms if an atom or molecule

gains electrons Ionic bond: attractive force between oppositely

charged ions Example: NaCl


Figure 2.6

Loss of electron:positive charge

Sodium atom (Na)

+ –

Chlorine atom (Cl) Sodium ion (Na+) Chlorine ion (Cl–)

Sodium chloride molecule (NaCl)

Gain of electron: negative charge

Na NaCl Cl


Hydrogen Bonds Form between Polar Molecules

Hydrogen Bonds Weak hydrogen bonds form between oppositely

charged regions of polar molecules– Example:

– weak forces between polar water molecules

– In DNA

– proteins


Table 2.1


When atoms gain, lose, or share they stay close When atoms gain, lose, or share they stay close together, held by attractions called together, held by attractions called chemical bonds chemical bonds

• When is a covalent bond formed?When is a covalent bond formed?

• When is an ionic bond formed?When is an ionic bond formed?

• What is a hydrogen bond?What is a hydrogen bond?

•


H HH2O

+ +

–

O

Atoms Combine to Form MoleculesAtoms Combine to Form Molecules


Living Organisms Contain Only Certain Elements

Over 100 different elements 99% of body weight consists of 6 elements

– Oxygen

– Carbon

– Hydrogen

– Nitrogen

– Calcium

– Phosphorus


Life Depends on Water

Key properties of water:– Water is an excellent solvent

– Water is liquid at body temperature

– Water can absorb and hold heat energy

– Evaporation of water uses up heat energy

– Water participates in essential chemical reactions


Water Is the Biological Solvent

Solvent: liquid in which other substances dissolve Solute: any dissolved substance Hydrophilic: polar molecules that are attracted to

water and interact easily with water Hydrophobic: nonpolar neutral molecules that do

not interact with or dissolve in water


Water Is a Liquid at Body Temperature

Water serves an important transport function in the blood, which is 90% water

Water is the main constituent of:– Intracellular spaces

– Extracellular spaces 60% of body weight is water


Water Helps Regulate Body Temperature

Water absorbs and holds a large amount of heat energy with only a modest increase in temperature– Prevents rapid changes in body temperature

Evaporative cooling enables body to lose excess heat quickly


Water Participates In Chemical Reactions

Synthesis of carbohydrates, proteins, and lipids produces water molecules

Breakdown of carbohydrates, proteins and lipids consumes water molecules


The Importance of Hydrogen Ions

Acids– Donate hydrogen ions (H)

– Increase hydrogen ion concentration in solutions Bases

– Accept hydrogen ions

– Decrease hydrogen ion concentration in solutions pH Scale

– A measure of hydrogen ion concentration


The pH Scale Expresses Hydrogen Ion Concentration

Measure of hydrogen ion concentration in solution Ranges from 0 to 14

– Acids: pH 7

– Neutral: pH 7

– Basic: pH 7


Figure 2.10

Drain opener

Bleach

Ammonia cleanser

Soapy water

Baking soda

Human blood, tears

Saliva, urine

Black coffee

Tomatoes

Vinegar, cola

Lemon juice

Hydrochloric acid

Concentrated nitric acid

Mo

re a

lkal

ine

Mo

re a

cid

ic

Neutral pH


Buffers Minimize Changes in pH

Minimize pH change Help maintain stable pH in body fluids Carbonic acid and bicarbonate act as one of the

body’s most important buffer pairs HCO3

+ H H2CO3

(reversible reaction)

If blood is too acidic: HCO3 + H H2CO3

If blood is too alkaline: H2CO3 HCO3 H


The Organic Molecules of LifeThe Organic Molecules of Life--

--

--What are organic molecules?What are organic molecules?• Contain Contain carboncarbon

•forms 4 covalent bondsforms 4 covalent bonds•The backbone of biological moleculesThe backbone of biological molecules

• Some are called Some are called macromoleculesmacromolecules• Built by Built by dehydration synthesis dehydration synthesis reactionsreactions• Broken down by Broken down by hydrolysishydrolysis reaction reaction• 4 major groups of macromolecules: 4 major groups of macromolecules:


Carbohydrates: Used for Energy and Structural Support

General formula: Cn(H20)n

Monosaccharides: simple sugars– Glucose

– Fructose

– Galactose

– Ribose

– Deoxyribose Disaccharides: two monosaccharides linked together

– Sucrose: glucose fructose

– Maltose: glucose glucose

– Lactose: glucose galactose


Polysaccharides Store Energy

Polysaccharides: thousands of monosaccharides joined in linear and/or branched chains– Starch: made in plants; stores energy

– Glycogen: made in animals; stores energy

– Cellulose: indigestible polysaccharide made in plants for structural support


Lipids: Insoluble in Water

Three important classes of lipids– Triglycerides: energy storage molecules

– Phospholipids: primary component of cell membranes

– Steroids: carbon-based ring structures


Triglycerides: Stored in adipose tissue as energy-storage

molecules Composed of glycerol and three fatty acids

– Fatty acids may be saturated or unsaturated (in oils) Steroids: Composed of four carbon rings Examples: Cholesterol, hormones e.g. estrogen,

testosterone Phospholipids: primary component of cell membranes


Proteins: Complex Structures Constructed of Amino Acids

Long chains (polymers) of subunits called amino acids

Amino acids are joined by peptide bonds, which are produced by dehydration synthesis reactions

Polypeptide: a polymer of 3–100 amino acids Protein: a polypeptide longer than 100 amino acids

that has a complex structure and function


Enzymes Facilitate Biochemical Reactions

Enzymes– Are proteins

– Function as biological catalysts– Speed up chemical reactions– Are not altered or consumed by the reaction

– Without enzymes, many biochemical reactions would not proceed quickly enough to sustain life


Figure 2.22

Enzyme changes shape

Reactants

Product

Products are released

Reactants approach enzyme

Reactants bind to enzyme

Enzyme


Nucleic Acids Store Genetic Information

Nucleic acids are long chains containing subunits known as nucleotides

Two types of nucleic acids– DNA: deoxyribonucleic acid

– RNA: ribonucleic acid DNA contains the instructions for producing RNA RNA contains the instructions for producing proteins Proteins direct most of life processes DNA RNA Proteins



Nucleotides: building blocks (monomers) of nucleic acids

Each nucleotide contains– 5 carbon sugar

– Phosphate group

– Nitrogenous base– Adenine

– Guanine

– Cytosine

– Thymine in DNA & Uracil in RNA



Structure of DNA (deoxyribonucleic acid)– Double–stranded

– Nucleotides contain– Deoxyribose (sugar)– Nitrogenous bases

– Adenine

– Guanine

– Cytosine

– Thymine

– Complementary base pairing:– Adenine - Thymine– Guanine - Cytosine


Figure 2.24

Base pair

Phosphate

Sugar

Nucleotide

C

C

G

G

A

A

A

C

G

G

G C

A

T

T

T

T

P

P

P

P

P

P

P

P

P

T

A



Structure of RNA (ribonucleic acid)– Single–stranded

– Nucleotides contain– Ribose (sugar)– Nitrogenous bases

– Adenine

– Guanine

– Cytosine

– Uracil


Figure 2.25

Phosphate

Ribose

Uracil

P

P

P

P

P

C

G

A

(U)


ATP Carries Energy

Structure and function of adenosine triphosphate (ATP)– Universal energy source

– Bonds between phosphate groups contain potential energy

– Breaking the bonds releases energy– ATP ADP P energy


Figure 2.26

Adenosine

Adenosine Adenosine

Adenine (A)

Triphosphate

Ribose

H2O

(ATP) (ADP)

Hydrolysis of ATP produces useful energy for the cell

P P P P P P

H2O

Energy for ATP synthesis comes from food or body stores of glycogen or fat

The breakdown and synthesis of ATP.The breakdown (hydrolysis) of ATP yields energy for the cell. The reaction is reversible, meaning that ATP may be resynthesized using energy from other sources.

The structure of ATP.

© 2014 pearson education, inc. objectives 1.define/describe an atom and its subatomic particles...

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