Biology Now, 2e

52 ■ CHAPTER 03 Chemistry of Life

CELLS

H

Hydrogen

P

Antibodies

There are four levels

of protein structure.

The simplest level is

a chain of amino

acids.

The chain folds

further into a 3D

shape that supports

the protein’s function.

Some proteins join

other proteins and

form a complex.

This chain then forms

coils or sheets.

Amino acid

P

Phosphorus

Proteins

Proteins are polymers of amino acids

and perform many functions in the cell.

H 3 N+

O

OH

C C

H

R

Tetanus

toxoid

Human antibodies

and the bacterial

tetanus toxoid are

both proteins.

Foods rich in

protein include

meats, fish, dairy,

and beans

(legumes).

O–

O–

P O

O

O

OHOH

H

H H

CH 2

C

NH 2

N

N N

N Carbon

Nitrogen

Nucleic acids are polymers of nucleotides and

function to store and transmit genetic information.

The four different

ribonucleotides

make up RNA.

RNA is made up

of one strand of

nucleotides.

Nucleotide

A eukaryotic plant cell.

DNA is built

of two strands

of joined

nucleotides.

A human has 46 chromosomes.

Cell

Cytoplasm

Ribosome

mRNA

Protein

Cell

RNA

Cytoplasm

Nucleus

DNA

mRNA

C

N

Nucleic acids

Supplements

advertising amino

acids contain these

building blocks of

proteins.

RNA is read by

ribosomes to

create proteins.

The genetic

information in DNA

is transcribed into

RNA.

The 20 amino

acids differ only

at the “R” side

group.

O–

O–

P O

O

O

OH H

H

H H

CH 2

C

N

The four different

deoxyribonucleotides

make up DNA.

Figure 3.11

Biomolecules are

critical for life

A handful of monomers

(mono, “one”) can be

assembled into a great

variety of polymers

(poly, “many”). Each

of these biologically

important molecules is

built on a framework of

repeating monomers

made up of some, and in

several cases all, of the

atoms shown in the center

circle—with the exception

of the lipids, which are

instead characterized by

repeating atoms of carbon

and hydrogen. M