Download Ch. 2 - The Chemistry of Life

Chapter 2


Matter—anything that occupies space and has
mass (weight)
Energy—the ability to do work
◦
◦
◦
◦
Chemical
Electrical
Mechanical
Radiant

Elements—fundamental units of matter
◦ 96 percent of the body is made from four elements





Carbon (C)
Oxygen (O)
Hydrogen (H)
Nitrogen (N)
Atoms—building blocks of elements


Elements – composed of atoms of the same
kind
Compound—composed of two or more atoms
of different kinds chemically combined
Figure 2.4


Atoms are united by chemical bonds
During chemical reactions chemical bonds are
broken, atoms rearrange, and new chemical
bonds form.
◦ A chemical bond is simply the force of attraction
between two atoms.

Groups of atoms bonded together are
referred to as a “molecule”.

Some bonds result in creating molecules that
are polar (like mini-magnets).
 Water is a polar molecule
Figure 2.8b

Polar substances dissolve in water; nonpolar
substances do not (“like dissolves like”).

Because water is polar, its molecules are very
attracted to each other.
◦ This strong inter-molecular attraction in water is
called “hydrogen bonding”.

This gives water very high surface tension.
+
H
H
O
–
Hydrogen bonds
+
H
O
–
–
H
O
H
+
–
+
+
H
H
O
–
(a)
+
H
(b)
Figure 2.9

Organic compounds
◦ Large, complex molecules (macromolecules)
◦ Must contain carbon and hydrogen
◦ Includes carbohydrates, lipids, proteins, nucleic acids

Inorganic compounds
◦ Smaller molecules
◦ Lack carbon in combination with hydrogen
◦ Tend to be simpler compounds
◦ Includes water, salts, and some acids and bases

Living things contain BOTH organic and
inorganic compounds.


Dehydration synthesis—monomers (building
blocks) are joined to form polymers through
the removal of water molecules
Biologically important to growth and repair
Figure 2.13a



Hydrolysis—polymers are broken down into
monomers through the addition of water
molecules
Opposite of dehydration synthesis
Biologically important in digestion
Figure 2.13b

Carbohydrates
◦ Contain carbon, hydrogen, and oxygen in a 1:2:1
ratio
◦ General formula CH2O
◦ Include sugars and starches
◦ Classified according to size
 Monosaccharides—simple sugars ex: glucose C6H12O6
 Disaccharides—two simple sugars joined by dehydration
synthesis ex: maltose C12H22O11
 Polysaccharides—long-branching chains of linked
simple sugars ex: starch and glycogen
Figure 2.14a–b
Figure 2.14c
Figure 2.14d

Lipids
◦ Contain carbon, hydrogen, and oxygen
 Carbon and hydrogen outnumber oxygen
◦ Insoluble in water (not polar!)
◦ Important components of cell membranes

Common lipids in the human body
◦ Neutral fats (triglycerides)
 Found in fat deposits
 Source of stored energy
 Composed of three fatty acids and one glycerol molecule
 Saturated fatty acids contain only single covalent bonds
 Unsaturated fatty acids contain one or more double covalent
bonds
Glycerol
3 fatty acid chains
(a) Formation of a triglyceride
Triglyceride, or neutral fat
3 water
molecules
Figure 2.15a
Figure 2.16a
Figure 2.16b

Common lipids in the human body
(continued)
◦ Phospholipids
 Contain two fatty acids rather than three
 Form cell membranes
Polar “head”
Nonpolar “tail”
Phosphorus-containing
group (polar end)
Glycerol
backbone
2 fatty acid chains
(nonpolar end)
(b) Phospholipid molecule (phosphatidylcholine)
Figure 2.15b

Common lipids in the human body
(continued)
◦ Steroids
 Include cholesterol, bile salts, vitamin D, and some
hormones
 Cholesterol is the basis for all steroids made in the
body
 High levels of cholesterol can lead to heart disease
 Excess saturated fats are converted to cholesterol in the
body
Figure 2.15c

Proteins
◦ Account for over half of the body’s organic matter
 Provide for construction materials for body tissues
 Play a vital role in cell function
 Act as enzymes, hormones, and antibodies
◦ Contain carbon, oxygen, hydrogen, nitrogen, and
sometimes sulfur
◦ Built from amino acids (monomers)

Amino acid structure
◦ Contain an amine group (NH2)
◦ Contain an acid group (COOH)
◦ Vary only by R groups
 20 different kinds
Amine
group
Acid
group
(a) Generalized
structure of all
amino acids
(b) Glycine
(the simplest
amino acid)
(c) Aspartic acid
(an acidic
amino acid)
(d) Lysine
(a basic
amino acid
(e) Cysteine
(a sulfurcontaining
amino acid)
Figure 2.17a-e


Proteins can bend and fold into interesting
shapes.
The shape of a protein is vital to its function.
◦ If a protein loses its shape it can’t do its job.
(a) Primary structure. A
protein’s primary structure
is the unique sequence of
amino acids in the
Amino
polypeptide chain.
acids
Hydrogen bonds
Amino
acids
(b) Secondary structure.
Two types of secondary
structure are named
alpha-helix and betapleated sheet. Secondary
structure is reinforced by
hydrogen bonds. Dashed
lines represent the
hydrogen bonds in this
figure.
Alphahelix
-pleated sheet
Figure 2.18a-b
Figure 2.18c-d
◦ Function in structure and also as antibodies or
enzymes
◦ Can be denatured (unraveled) by heat or pH
changes
◦ This will make the protein non-functional
Heme group
Globin
protein
(b) Hemoglobin molecule composed of the
protein globin and attached heme groups.
(Globin is a globular or functional protein.)
Figure 2.19b


Proteins that act as biological catalysts
Increase the rate of chemical reactions
◦ Bind to substrates at an active site
◦ Their SHAPE is critical to their function!
◦ Enzyme function is affected by pH, temperature and
concentration
Energy is Water is
absorbed; released.
bond is
H2O
formed.
Substrates (S)
e.g., amino acids
+
Product (P)
e.g., dipeptide
Peptide
bond
Active site
Enzyme-substrate
complex (E-S)
Enzyme (E)
1 Substrates bind to active
site. Enzyme changes shape
to hold substrates in proper
position.
2 Structural changes
occur, resulting in the
product.
Enzyme (E)
3 Product is released.
Enzyme returns to
original shape, ready
to catalyze another
reaction.
Figure 2.20

Built from nucleotide monomers which
contain:
◦ Pentose (5 carbon) sugar
◦ A phosphate group
◦ A nitrogenous base
 A = Adenine
 G = Guanine
 C = Cytosine
 T = Thymine
 U = Uracil.
Deoxyribose
Phosphate sugar
Adenine (A)
(a) Adenine nucleotide
(Chemical structure)
KEY:
Thymine (T)
Cytosine (C)
Adenine (A)
Guanine (G)
Figure 2.21a

Deoxyribonucleic acid (DNA)
◦ The genetic material found within the cell’s nucleus
◦ Provides instructions to make every protein in the body
◦ Organized by complimentary (paired) bases to form a
double-stranded helix held together by hydrogen
bonds
◦ Contains the sugar deoxyribose and the bases adenine,
thymine, cytosine, and guanine
◦ Replicates (duplicates) before cell division
Hydrogen bond
Deoxyribose
sugar
Phosphate
(d) Diagram of a DNA molecule
KEY:
Thymine (T)
Cytosine (C)
Adenine (A)
Guanine (G)
Figure 2.21c-d

Ribonucleic acid (RNA)
◦ Carries out DNA’s instructions for protein synthesis
◦ Created from a template of DNA
◦ Organized by complimentary bases to form a singlestranded helix
◦ Contains the sugar ribose and the bases adenine,
uracil, cytosine, and guanine
◦ Three varieties are messenger, transfer, and ribosomal
RNA

Adenosine triphosphate (ATP)
◦ Composed of a nucleotide built from ribose sugar,
adenine base, and three phosphate groups
◦ Supplies chemical energy used by all cells
◦ Energy is released by breaking high energy
phosphate bonds
◦ ATP is replenished by oxidation (breakdown) of
food fuels; primarily sugars
Adenine
High
energy
bonds
Ribose
Phosphates
(a) Adenosine triphosphate (ATP)
Adenosine diphosphate
(ADP)
(b) Hydrolysis of ATP
Figure 2.22a-b
(a) Chemical work. ATP provides the
energy needed to drive energyabsorbing chemical reactions.
Solute
Membrane
protein
(b) Transport work. ATP drives the
transport of certain solutes (amino
acids, for example) across cell
membranes.
Relaxed
smooth
muscle cell
Contracted
smooth
muscle cell
(c) Mechanical work. ATP activates
contractile proteins in muscle cells
so that the cells can shorten and
perform mechanical work.
Figure 2.23a-c