Biology Now, 2e

Ingredients for Life ■ 53

O

S

Oxygen

Sulfur

Common sugar is

the disaccharide

sucrose.

Simple sugar

Carbohydrates

Carbohydrates are polymers of simple

sugars, used for energy storage and

structural support.

A major component

of the bacterial cell

wall is peptidoglycan.

The hard outer shell

of crustaceans is

made of chitin.

Glycogen is stored in

muscle tissue as a

quick energy source.

H

H

CH 2 OH

H

H

OH H

OH

O

HO

OH

The “strings” in

celery are

cellulose fibers.

Tubers like
potatoes store
energy as starch.

Monosaccharides pair

up to form disaccharides

(e.g., sucrose).

Long chains of

monosaccharides create

polysaccharides like

starch and cellulose.

O

O

C C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

H

H H

H

H

H

CH 3

Hydrocarbon

Lipids

Lipids are a diverse group of

hydrophobic molecules composed

primarily of hydrocarbons.

Hydrocarbon rings

join together to form

steroid molecules

like cholesterol.

Phospholipids and

cholesterol, along

with proteins, form

the membranes in

a cell.

Fatty acid chains join glycerol

to form triglycerides, and

join glycerol and phosphates

to form phospholipids.

Chains of

hydrocarbons

form fatty

acids.

Cholesterol is an essential component of cell

membranes, but in excess it can cause

atherosclerosis (clogging of arteries), resulting

in heart attack and stroke.

Bacon, like all meats,

contains both fat and

cholesterol.

Fat under the skin of

marine mammals like

the walrus provides

long-term energy

storage and insulation

against icy waters.

Seeds contain oil as a

long-term energy

source for a newly

germinated sprout to

use until its leaves are

formed and capable

of photosynthesis.