6. Principles of chemistry underlie the functioning of biological systems.
As a basis for understanding this concept:
6.a. Carbon, because of its ability to combine in many
ways with itself and other elements, has a central role in the chemistry of living
6.b. Living organisms are made of molecules consisting
largely of carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur.
6.c. Living organisms have many different kinds of molecules,
including small ones, such as water and salt, and very large ones, such as carbohydrates,
fats, proteins, and DNA.
Because all living organisms are made up of atoms, chemical reactions take
place continually in plants and animals , including humans. The uniqueness of
organic chemistry stems from chain polymers. Life could not exist without
the ability of some chemicals to join together, repetitively, to form large, complex
molecules. Concepts learned in this standard set are critical for understanding
fully the chemistry of the cells of organisms, genetics, ecology, and physiology
that will be taught in the high school biology/life sciences standard sets.
Carbon is unique among the elements because it can bond to itself and to many
other elements. This attribute makes possible many different kinds of large, carbon-based
molecules. Typically, carbon will make four separate covalent bonds (to other
carbon atoms), but double and triple bonds are also possible. The variety of bonds
allows carbon-based molecules to have a wide range of shapes and chemical properties.
Key shapes include tetrahedral (e.g., methane and carbon tetrachloride), planar
(e.g., formaldehyde and ethylene), and linear (e.g., acetylene and carbon dioxide).
Students can research the nomenclature, composition, and structure of organic
molecules by using textbooks and supplemental instructional mate-rials. They can
also construct models of carbon-based molecules by using commercial modeling kits
or inexpensive alternatives (e.g., gumdrops and tooth-picks).
Living organisms are made up of a great variety of molecules consisting of
many atoms (with carbon atoms playing the main roles), but the number of different
elements involved is quite small. Carbon and only five other elements make up
most of Earth’s biomass. Those six elements, however, can combine in many different
ways to make large, organic molecules and compounds. To demonstrate this idea,
teachers may burn organic material, such as bone, leaves, wood, or a variety of
candles. They may hold a cold glass or plate above the flame to condense droplets
of water, one of the combustion products. They may also hold a heat-treated glass
in the flames to collect carbon deposits in the form of soot. Students can discuss
what elements were in the organic material. Teachers may draw students’ attention
to the black material that forms when meat is roasted or grilled or when toast
Living organisms require a variety of molecules; some molecules contain carbon
and some do not. The molecules that make up organisms and control the biochemical
reactions that take place within them are usually large molecules, such as DNA,
proteins, carbohydrates, and fats. Organisms also require simple substances, such
as water and salt, to support their functioning. Teachers may encourage students
to research why plants and animals need simple molecules such as water. Other
activities for teachers may include squeezing the water from celery or turnips
to demonstrate the presence of water. Or they may ask students how they can demonstrate
that water is in fruits and vegetables (e.g., dried fruit). Teachers may also
ask students how they know that there is salt in their bodies. Most students know
that their perspiration tastes salty.
|The Structure and Composition of
|Review from STANDARD SET 2
force between masses, is responsible for forming the Sun, the planets, and the
moons in the solar system into their spherical shapes and for holding the
It is also responsible for internal pressures in the Sun, Earth and other
planets, and the atmosphere. Newton asked himself whether the force that
causes objects to fall to Earth could extend to the Moon.
Newton knew that the Moon should travel in a
line (getting farther and farther from earth.) unless a force was acting on ot to change its direction into a circular path.He
worked out the mathematics that convinced him that the force between all
massive objects is directly proportional to the product of their masses and
inversely proportional to the square of the distance between their centers.
This relationship was then extended to explain the motion of Earth and other
planets about the Sun.
Initially, the universe consisted of light elements, such as hydrogen, helium,
and lithium, distributed in space. The attraction of every particle of matter
for every other particle of matter caused the stars to form, making possible
the “stuff” of the universe.
As gravity is the fundamental force responsible for the formation and motion
of stars and of the clusters of stars called galaxies, it controls the size
and shape of the universe.
The structure and composition of the universe can be learned from studying stars
and galaxies and their evolution. As a basis for understanding this concept:
a. Students know galaxies are clusters of billions of stars and may have different
b. Students know that the Sun is one of many stars in the Milky Way
galaxy and that stars may differ in size, temperature, and color.
c. Students know how to use astronomical units and light years as measures of
distances between the Sun, stars, and Earth.
d. Students know that stars are the source of light for all bright objects in
outer space and that the Moon and planets shine by reflected sunlight, not by
their own light.
STANDARD SET 4. Framework
Galaxies them-selves appear to form clusters that are separated by vast
expanses of empty space.
As galaxies are discovered they are classified by their differing sizes and
The most common shapes are spiral, elliptical, and irregular. Beautiful,
full-color photo-graphs of astronomical objects are available on the Internet,
in library books, and in popular and professional journals.
have inferred the existence of planets orbiting some stars.
The Sun is a star located on the rim of a typical spiral galaxy called
the Milky Way and orbits the galactic center.
In similar spiral galaxies this galactic center appears as a bulge of stars in
the heart of the disk.
The bright band of stars cutting across the night sky is the edge of the Milky
Way as seen from the perspective of Earth, which lies within the disk of the
Stars vary greatly in size, temperature, and color. For the most part those
variations are related to the stars’ life cycles.
Light from the Sun and other stars indicates that the Sun is a fairly typical
star. It has a mass of about 2
kg and an energy output, or luminosity, of about 4
The surface temperature of the Sun is approximately 5,500 degrees Celsius, and
the radius of the Sun is about 700 million meters.
The surface temperature determines the yellow color of the light shining from
the Sun. Red stars have cooler surface temperatures, and blue stars have
hotter surface temperatures.
To connect the surface temperature to the color of the Sun or of other stars,
teachers should obtain a “black-body” temperature spectrum chart, which is
typically found in high school and college textbooks.
Distances between astronomical objects are enormous.
Measurement units such as centimeters, meters, and kilometers used in the
laboratory or on field trips are not useful for expressing those distances.
Consequently, astronomers use other units to describe large distances.
The astronomical unit (AU) is defined to be equal to the average distance from
Earth to the Sun: 1 AU
Distances between planets of the solar system are usually expressed in AU.
For distances between stars and galaxies, even that large unit of length is
Interstellar and intergalactic distances are expressed in terms of how far
light travels in one year, the light year (ly):
meters, or approximately 6 trillion miles.
The most distant objects observed in the universe are estimated to be 10 to 15
billion light years from the solar system.
The energy from the Sun and other stars, seen as visible light, is
caused by nuclear fusion reactions that occur deep inside the stars’ cores.
By carefully analyzing the spectrum of light from stars scientists can
determine the composition of stars (and other distant objects)
Most stars are composed primarily of hydrogen, a smaller amount of helium, and
much smaller amounts of all the other chemical elements.
Most stars are born from the gravitational compression and heating of hydrogen
A fusion reaction results when hydrogen nuclei combine to form helium nuclei.
Hydrogen fusion in
releases energy and establishes a balance between the inward pull of gravity
and the outward pressure of the fusion reaction products.
Ancient peoples observed that some objects in the night sky wandered about
while other objects maintained fixed positions in relation to one another
(i.e., the constellations). Those “wanderers” are the planets.
Through careful observations of the planets’ movements, scientists found that
planets travel in nearly circular (slightly elliptical) orbits about the Sun.
Planets (and the Moon) do not generate the light that makes them visible.
The fact that planets
do not generate the light that makes them visible is
demonstrated during eclipses of the Moon or by observation of the phases of
the Moon and planets when a portion is shaded from the direct light of the
Various types of exploratory missions have yielded much information about the
reflectivity, structure, and composition of the Moon and the planets.
missions to the moon and planets have included
spacecraft flying by and orbiting those bodies
the soft landing of spacecraft fitted with instruments on them
the visits of astronauts to the Moon during the 1970's
Nine planets are currently known in the solar system:
Planets greatly in size and appearance.
the mass of Earth is 6
kg and the radius is 6.4
Jupiter has more than 300 times the mass of Earth, and the radius is ten times
The planets drastically vary in their
The inner planets (Mercury, Venus, Earth, and Mars) tend to be relatively
small and are composed primarily of rock.
The outer planets (Jupiter, Saturn, Uranus, and Neptune) are generally much
larger and are composed primarily of gas.
referrred to as 'Gas Giants'
Pluto is composed primarily of rock and is the smallest planet in the solar
All the planets are much smaller than the Sun
All objects are attracted toward one another gravitationally, and
strength of the gravitational force between objects depends on their masses
and the distance that separates them from one an-other
They are all being
acted on by the graviational attraction of each other and the Sun
MOONS & SATELLITES
Planets have smaller objects orbiting them called
Earth has one moon that completes an orbit once every 28 days (approximately).
Mercury and Venus have no moons, but Jupiter and Saturn have many moons.
Very small objects composed mostly of rock (asteroids) or the ice from
condensed gases (comets) or both also orbit the Sun.
The orbits of many asteroids are relatively circular and lie between the
orbital paths of Mars and Jupiter (the asteroid belt).
Some asteroids and all comets have highly elliptical orbits, causing them to
range great distances from very close to the Sun to well beyond the orbit of
Things to do...
visit a planetarium would be another way to observe the sky.
observe the motion of Jupiter’s inner moons as well as the phases of Venus.