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Chemical Compounds of Life

Chapter 4

314 Biology

4.1 Organic Compounds

Contain the element carbon

Occur naturally in living things or their products

Some produced in chemistry laboratory

Also contain H, N, O

Inorganic Compounds

Do not contain carbon


CO2 ( carbon dioxide )

CaCO3 ( calcium carbonate )

Contained in living organisms

Reactions are complicated

Water An Important Inorganic Compound

Most important of all

65 % of body

Survive for weeks without food

Biological processes take place only in water

Adhesion and cohesion both play important roles in the transport of water in plants.

Forces help water to rise up through the roots


Cohesion polar molecule

oxygen end has a partial negative charge

hydrogen end has a partial positive charge

Holds water molecule together

How and why water can store heat?

Protects organisms from damaging changes in temperature

Adhesion attraction between the molecules of one substance and the molecules of another substance


Best solvent why?


Ionic compounds

Capillary action or capillarity

Two slides dipped in water

Structure and Types of Organic Compounds

Difference inorganic and organic compounds

Greater size and complexity of many organic compounds

Electron structure

Number of carbon atoms

4 valence electrons

figure 4-4, p. 59

figure 4-5, p. 60

Long chain bonds


Unlimited arrangements

Usually double bonds formed

Sometimes triples bonds occur

Four types of organic compounds

Carbohydrates, lipids, nucleic acids, and proteins

Types of Hydrocarbon Bonds


Carbohydrates and Lipids


Carbohydrates compounds of carbon, hydrogen, and oxygen

Same ratio of H and O as water

2 H for ever 1 O

Simplest carbohydrates are Monosaccharides ( simple sugars )

Figure 4-6, page 61 shows structural formulas for C6H12O6

Glucose, fructose, and galactose all of which have the same chemical formula but different structural formula

Chemical names of sugars always end in ose

Sugars contain large amounts of energy

Nearly all organisms use glucose as a source of energy

Dehydration Synthesis

Sugar molecules can be put together by DS.

Synthesis putting together

Dehydration removing water

OH group in each molecule of water.

Figure 4-7, page 61.

Living cells DS brought about by action of enzymes ( see p. 68 )


Two simple sugars

A double sugar

Formed by DS

Figure 4.7 is maltose



Several simple sugars joined by DS or long chains of repeating sugars units.

Polymers large molecules consisting of long chains of repeating sugar units.

Polysaccharides are sugar polymers

Largest polysaccharides may contain hundreds or thousands of sugar units.

Organisms store excess sugar in the form of polysaccharides.

In plants, stored as starch.

In humans, stored in liver as glycogen ( polysaccharide ) sometimes called animal starch

Other polysaccharide types

cellulose found in plants

Chitin makes up shells of insects


Disaccharides and polysaccharides may be broken apart by HYDROLYSIS.

Figure 4.8, page 62

Maltose + water Glucose + Glucose

Two simple sugar bonds broken and OH groups restored.

In living organisms brought about by different enzymes action.


Are substances that are commonly called fats, oils, and waxes.

Made up of C, H, O

Less O2, less than in carbohydrates.

Lipids serve as reserve energy supply.

Lipids supply twice the amount of energy than the same amount of carbohydrates.

Fats and oils are chemically similar.

Oils remain liquid at room temperature

Plants: oils in seeds

Peanut oil, corn oil, castor oil.

Mammals: fat under skin

Cushions helps stop heat loss

Storage product but, not stored long

Broken down and replaced

Mice replace about each week.

The Formation of Lipids

Waxes combination of fatty acids and compounds that are similar to glycerol.

Fats and oils formed when fatty acids combine with glycerol.

Glycerol is a 3-carbon chain with an OH group bonded to each carbon.

Fatty acid:

1. A chain of carbon atoms to which hydrogen atoms are bonded

2. Carboxyl group

Consists of 1 carbon bonded to 1 O by a double bond and to an OH group.

See figure 4-9, page 62 and figure 4-10, page 63.

Saturated Fats

All single bonds

Usually solids

Evidence: found in animal products like butter and meat, increase cholesterol production in the body.

Build up of deposits that harden and narrow arteries.

Heart attack and strokes.

Cholesterol: normally synthesized in the body, mainly in the liver. Is a structural component of nerve tissue and cell membrane. It also is used to make various steriod hormones, including progesterone, testosterone, estradiol, and cortisol. Bile salts are breakdown products of cholesterol.

Unsaturated Fats

One or more pairs of carbon atoms in the fatty acid molecules are joined together by a double bond or even a triple bond.

Polyunsaturated fat that has chains with more than one double or triple bond.

Figure 4-11, page 63.

Can be changed to saturated fats, add a hydrogen. Process called hydrogenation.

Tend to be oils.

Many processed foods contain partially hydrogenated fats.

Found in plant products tend to decrease blood cholesterol levels.





Nucleic Acids and Proteins

Nucleic Acids

Contain P, N, C

Two kinds: both found in nucleus

DNA ( deoxyribonucleic acid )

Hereditary material

RNA ( ribonucleic acid )

More information in Chapter 26

The Structure of DNA

Molecule of long chain of repeating nucleotides


has 5-carbon sugar ribose or deoxyribose bonded to PO4 and a nitrogenous base

Only 4 nitrogenous bases in DNA molecule

Adenine, thymine, cytosine, guanine

Adenine is always bonded to a thymine

Cytosine is always bonded to a guanine

Shape of a ladder, figure 4-12a and 12b, page 65

Chain of nucleotides

Each rung consists of 2 bases

Human cell has 3 million pairs of bases

Sequence of the bases acts as codes that determines what protein is made in the cell.

DOUBLE HELIX coiled and fits in cell

The Structure of RNA

Similar to DNA


One chain or bases

Sugar RNA is ribose

Thymine is replaced by uracil

RNA is involved in protein synthesis


Contains N, C, H, O

Some contain S and P

Unlimited possibilities

Numerous range of properties

Makes life possible by its complexity

Found throughout living organisms


Body tissues

cartilage, bones, muscles



Enzymes are proteins

Amino Acids

Structural units of proteins

Figure 4-13, page 66.

Are simple compound and consists of

1 carboxyl group ( COOH )

1 amino acid ( NH2 )

1 Hydrogen atom

1 side chain, ( R ) which is different in each amino acid

Glycine, side which is another H

Alanine, side is another CH3

20 amino acids are commonly found as parts of proteins

The Peptide Bond

Figure 4-14, page 66

Peptide : a bond between two amino acids

Resulting Molecule called dipeptide.

Amino acids added to either end of a dipeptide by dehydration synthesis.

polypeptide long chain of amino acids

All proteins are made up of one or more polypeptides bonded together.

The Structure of Proteins

Linked together in any sequence and in varying lengths

Making different proteins.

Shapes include


Pleated sheets


Cross-links: creates enormous variety

Smallest protein molecule has about 50 amino acids or about 1000 atoms

The largest over 100,000 amino acids and millions of atoms.

Ordering is difficult

Insulin is the first protein structure

1954 by Frederick Sanger

Noble Prize Winner

Hormone that controls blood-glucose levels.

Technology now, in the present.

Methods to identify structures of proteins is painstaking.

Break molecule into smaller and smaller pieces

Identify the amino acid at the end of each broken section.

STM scanning tunneling microscope (page.67)



The Importance of Enzymes

Are protein substances necessary for chemical reactions in living cells.

Automobile engine

Burning of gasoline

Life chemical reactions are different.

Dozen of steps

Small part of molecule is removed

Small groups of atoms is added

Atoms rearranged in molecules

Steps must occur with great precision and in correct order.

Ordinary temperatures inside cell

Not give off great amounts of heat

Cell will be destroyed

Catalyst and Substrate

Catalyst: a substance that brings about a reaction without being changed itself.

Enzymes are organic catalysts.

Fore each step there is a specific enzyme

Enter a chemical reaction temporarily.

Used again and again.

Made by cells of living organism

Substrate: the substance that an enzyme acts upon.

Enzyme Names

End in suffix ase

Rest of name derived from substrate.

Example: maltase, which splits maltose into 2 glucose molecules. ( - ose, sugars )

Protease breaks down proteins

Lipase breaks down lipids

Pepsin made inside cells of stomach wall.

Leaves cells and mixes with food, breaks down proteins in food into simpler substances

How Enzymes Work

Depends on shape.

Active site on surface of enzyme.

Substrate fits active site

figure 4-15, page 69.

Forms temporary union

Enzyme-substrate complex

Break bonds within substrate molecule

Substrate separated into 2 smaller molecules

Two molecules join, two substrates

Each fit into active site

Close contact

( each enzyme catalyzes a reaction with only a certain substrate )

Lock-and-key model

Active site

Key and one lock shape fits only one substrate

Each enzyme can catalyze a reaction only of those substrates

Figure 4-15a, page 69

Induced-fit model

Enzyme is not a rigid shape

Changes shape slightly

Figure 4-15b, page 69

Grasping a baseball

Factors Affecting Enzyme Action
( fill in the blanks by using your textbook )

Small amounts of an enzyme can cause the reaction of large quantities of ___________.

Enzymes enable _____ reactions to take place at normal ___________________.

Enzymes work best at certain ___________.

At still higher _________, however, the _________ itself starts to breakdown. This process is called ____________________.

Each enzyme works best at a certain _____.

The rate of an enzyme-controlled reaction depends on the __________________ of the enzyme and _________________.

Some enzymes need substances called _______________ in order to function.

_________ are organic substances but not _____________.

Background Information

In the past, it was believed that organic compounds existed only on Earth. Using modern technology, organic compounds, such as methane, have been, detected in the atmosphere of planets and in interstellar clouds of gas. Organic compounds have been found in meteorites.

Many students believe that carbohydrates taste sweet. Although carbohydrates that are classified as sugars usually taste sweet, others such as polysaccharides do not.

Background continued

Sucrose and lactose are two common disaccharides. Lactose, or milk sugar, is formed from glucose and galactose. Sucrose, or table sugar, is made of glucose and fructose.

Most fatty acids have an even number of carbon atoms.

Stearic acid C18H36O2

Palmitic acid C16H32O2

Oleic acid C18H34O2

Nucleotides are building blocks of nucleic acids.

Enormous variety of proteins can be produced by different combinations of the 20 amino acids.

More Background Information

Many enzyme-catalyzed reactions involve the transformation of energy. Such reactions occur in photosynthesis and cellular respiration. Energy from ATP is used in muscle contraction and active transport processes.

Most of the chemical reactions of living cells will not occur without enzymes. Enzymes increase the rates of reactions they catalyze by at least 1 million times.

Enzymes are highly specific in their actions. Each enzyme catalyzes only one particular reaction, involving specific substrates.

Laboratory Investigation
pages 72 - 73

Name: Section: Lab Date:

Title: The Effect of Enzyme Concentration on Reaction Rate




Data Table:




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