chapter 2 - part 2 chemical reactions

7/28/2019 Chapter 2 - Part 2 Chemical Reactions

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1

Chemical Reactions

Chemical reactions occur when chemical bonds form or

break among atoms, ions, or molecules

Reactants are the starting materials of the reaction - the

atoms, ions, or molecules

Products are substances formed at the end of the chemical

reaction

NaCl Na+ + Cl-

Reactant Products


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Chapter 2 | Part 2


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Types of Chemical Reactions

Synthesis Reactionmore complex chemical structure

is formed

A + BABDecomposition Reaction

chemical bonds are broken to form

a simpler chemical structure

ABA + B

Exchange Reactionchemical bonds are broken and new

bonds are formed

AB + CDAD + CBReversible Reactionthe products can change back to the

reactants

A + BnAB


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4

Acids, Bases, and Salts

Electrolytessubstances that release ions in water

Acids

electrolytes that dissociate to release hydrogen ionsin water

HCl H+ + Cl-Basessubstances that release ions that can combine with

hydrogen ions

NaOH Na+ + OH-Saltselectrolytes formed by the reaction between an

acid and a base

NaCl Na+ + Cl-

HCl + NaOH H2O + NaCl


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Acid and Base Concentration

pH scale -indicates the concentration of hydrogen ions insolution

NeutralpH 7;indicates equal

concentrations of H+

and OH-

AcidicpH less than

7; indicates a greaterconcentration of H+

Basic or alkalinepH greater than 7;indicates a greater concentration of OH-

OHconcentration increasesH+ concentration increases

AcidicH+

Relative

Amounts

of H+ (red)

and OH

(blue)

Basic

OH

2.0

gastric

juice6.0

corn

7.0

Distilled

water

8.0

Egg

white

10.5

milk of

magnesia

11.5

Household

ammonia

pH 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Basic (alkaline)NeutralAcidic

3.0

apple

juice

4.2

tomato

juice

5.3

cabbage

6.6

cows

milk

7.4

Human

blood

8.4

Sodium

biocarbonate

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Neutralization and Buffers

Neutralization occurs when an acid and basereact to form a salt and water in adisplacement reaction.

HCl + NaOH NaCl + H2O Termed neutralization because water is formed

neutralizing the solution.

Buffers act as acids when pH is high and baseswhen pH is low.

Carbonic acid-bicarbonate system.


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7

2.3: Chemical Constituents

of Cells

Organic v. Inorganic Molecules

Organic molecules

Contain C and H

Usually larger than inorganic molecules

Dissolve in water and organic liquids

Carbohydrates, proteins, lipids, and nucleic acids

Inorganic molecules

Generally do not contain C and H Usually smaller than organic molecules

Usually dissociate in water, forming ions

Water, oxygen, carbon dioxide, and inorganic salts


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Inorganic Substances

Water

Most abundant compound in living material

Two-thirds of the weight of an adult human

Major component of all body fluids Medium for most metabolic reactions

Important role in transporting chemicals in the body

Absorbs and transports heat

Oxygen (O2)

Used by organelles to release energy from nutrients in

order to drive cells metabolic activities

Necessary for survival


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Inorganic Substances

Carbon dioxide (CO2)

Waste product released during metabolic reactions

Must be removed from the body

Inorganic salts

Abundant in body fluids

Sources of necessary ions (Na+, Cl-, K+, Ca2+, etc.)

Play important roles in metabolism


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Organic Substances

CarbohydratesProvide energy to cells

Supply materials to build cell structures

Water-soluble

Contain C, H, and O

Ratio of H to O close to 2:1 (C6H12O6)

Monosaccharidesglucose, fructose

Disaccharidessucrose, lactose Polysaccharidesglycogen, cellulose


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11

Organic Substances

Carbohydrates

(a) Some glucose molecules

(C6H12O6) have a straight

chain of carbon atoms.

C

C

C

C

C

C

H

O

H

O

O

O

HH

OH

H

H

H

H O

H

H

H

H

C

H

O

O H

H

OH

O H

H

H H

C

O

H

C

C C

OC

H

(b) More commonly, glucose

molecules form a ring structure.

O

(c) This shape symbolizes

the ring structure of a

glucose molecule.

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Organic Substances

Carbohydrates

O

(a) Monosaccharide

O O

O

(b) Disaccharide

O

O

O

(c) Polysaccharide

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Organic Substances

Lipids Soluble in organic solvents; insoluble in waterFats (triglycerides)

Used primarily for energy; most common lipid in the body

Contain C, H, and O but less O than carbohydrates (C57H110O6) Building blocks are 1 glycerol and 3 fatty acids per molecule

Saturated and unsaturated

Glycerolportion

Fatty acidportions

C

O

OH C C

H

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

H

C

O

OH C C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

H

C

O

OH C C

H

HH

C

H

H

C

H

H

C

H

H

C

H H

H



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Neutral Fats

Triglycerides are formed from a fatty acid and glycerol (asugar).

They are the most plentiful source of stored energy to our

bodies.

Two types: Saturated- contain only single bonds

Unsaturated- contains one(mono) or more(poly) double bonds

Short, unsaturated fats are liquids (oils) and come from plants.

Long, saturated fats are solid (butter and meat fat) and comefrom animals.


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Organic Substances

LipidsPhospholipids

Building blocks are 1 glycerol, 2 fatty acids, and 1 phosphate per

molecule

Hydrophilic and hydrophobic

Major component of cell membranes

C

H

C

OH

CH

H

Glycerol portion

(a) A fat molecule

O

O

Fatty acid

Fatty acid

Fatty acid

H

C

H H

HH

C

H

H

N

O

O

Fatty acid

Fatty acid

O

POCH

O

Phosphate portion

(b) A phospholipid molecule

(the unshaded portion may vary)

H

CH

C

H

H

O

(c) Schematic representationof a phospholipid molecule

Water-insoluble

(hydrophobic)

tail

Water-soluble

(hydrophilic)

head





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Organic Substances

LipidsSteroids

Four connected rings of carbon

Widely distributed in the body, various functions

Component of cell membrane Used to synthesize hormones

Cholesterol

(a) General structure of a steroid

CC

CH2C

H2C C

H

(b) Cholesterol

C

CH CH2

CH2CH

CH3

CH2

HC

HC

H2

H2

CH2 CH

CH

2

CH3

CH3

C

H2

C

H

CH3

HO C

CH3

CH2

CHC

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Organic Substances

Proteins Structural material Energy source

Hormones

Receptors

Enzymes Antibodies

Protein building blocks areamino acids

Amino acids held

together with peptide bonds

17

H N

H

C

H

C

O

OH

S

C

H

HH

H N

H

C

H

C

O

OH

C

C

C

H

H

C H

C H

H

CH

CH

H N

H

C

H

C

O

OH

R


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Four Levels of Protein Structure

Pleated

structure

Coiled

structure

Amino acids

N

N

N

N

N

HH

H

H

H

C

CC

C

O

O

O

CC

C

C

CC

OC

O

NN

H H

C

OC

C

OC

H

N

NH

O

O

C

CC

C

N

N

N

N H

H

H O C

CC

O

O

CC

C

H OC

C

C

N

C

NHO

CC

H OC

C

N

N

N

N H

H

H O C

O

O

CC

C

H OC

H

R

H

R

H

R

H

R

H

R

H

R

H

R

H

R

H

R

H

H

R

H

H

R

H

R

H

R

HHRR

HHRR

CH

CH

Secondary structure

Primary structure


Organic Substances

Proteins

Three-dimensional

folding

H H

Tertiary structure

Quaternary structure


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19

Animation: Protein Denaturation

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Organic Substances

Nucleic Acids Carry genes

Encode amino acid sequences of proteins

Building blocks are nucleotides

DNA (deoxyribonucleic acid)double polynucleotide

RNA (ribonucleic acid)single polynucleotide

S

P B



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Organic Substances

Nucleic Acids

S

P

S

P

S

P

S

P

S

P

S

P

B

B

B

B

B

B

S

S

S

S

S

S

P

P

P

P

P

P

B

B

B

B

B

B

(b)

S

P

S

P

S

P

S

P

S

P

S

P

B

B

B

B

B

B

(a)



chapter 2 - part 2 chemical reactions

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