Atoms, Molecules, Compounds,
Cells, Tissues, Organs and
Systems
So, why do we need to know
biochemistry anyway?
Atoms, Molecules and Compounds
• At the simplest level, the body is made of
atoms. The most common elements in
living organisms are: carbon, hydrogen,
oxygen, nitrogen, phosphorous, and sulfur.
• Molecules and compounds, such as water
and carbon dioxide, carbohydrates,
proteins, and lipids are molecules that are
important to our bodies.
Cells
Sperm Cell
Red Blood Cells
White Blood Cells
Nerve Cells
Generalized Cell
Cells
• Cells are the smallest independent units of
life, and all life depends on the many
chemical activities of cells.
• Some basic functions of cells include:
growth, metabolism, and reproduction.
• Cells range from 5 micrometers (sperm) to
more than a meter (some nerve cells).
In the cell …
• The cell is made of atoms that form
molecules.
• Cytosol – water, proteins, nutrients, waste
products, glycogen granules and lipid
droplets
• Ribosomes – RNA and proteins
• Mitochondria – proteins and lipids
* These are only some examples
Tissues
• Tissues are made up of many similar cells
that perform a specific function. Tissues
are divided into four groups: epithelial
(skin, linings, protective), connective
(bones and tendons, connects and
supports body), muscle (skeletal, smooth
and cardiac, produces movement) and
nervous (brain, spinal cord and nerves,
responds to stimuli and transmits signals).
• Bones, muscles, hair, nails, blood,
enzymes, etc., are proteins. Some have
extra elements to help strengthen
structures, but essentially, your body is a
lot of proteins.
Organs
• Organs are a collection of two or more kinds of
tissues that work together to perform a certain
function.
• Example: Stomach
 Epithelial tissue lines the stomach to protect it
 Smooth muscle tissue churns food
 Nervous tissue transmits nerve impulses that
coordinate muscle contractions
 Connective tissue holds all other tissues together
Systems
• A group of organs that work together to perform
a major function.
• All the body systems are specialized, and their
functions are coordinated to produce a dynamic
and efficient organism – the human body.
• Example: The respiratory system
 contains several organs that provide a mechanism for
exchange of oxygen and carbon dioxide between the
outside the body and the blood inside
Systems
• Integumentary (skin, hair, nails, sweat
and oil glands)
• Skeletal (bones and cartilage)
• Muscular (skeletal, smooth, cardiac)
• Nervous (brain, spinal cord, peripheral
nerves, sensory organs)
• Endocrine (ductless glands)
• Cardiovascular (heart, blood, blood
vessels)
• Lymphatic (glands, lymph nodes, lymph,
lymphatic vessels)
• Respiratory (airways, lungs)
• Digestive (stomach, intestines, other digestive
structures)
• Urinary (kidneys, ureters, urinary bladder,
urethra)
• Reproductive (ovaries, testes, reproductive
cells, accessory glands and ducts)
• Your body is made of atoms. When we look at
biochemistry, it is so that you understand that at the
molecular level, we are all just elements that come
together and function together.
• Glucose is our main energy source that can be used by
cells (cellular respiration)
• Glycogen can stored in cells as a quick energy source
• Fats are an energy source, but also make cell
membranes and so much more
• Proteins are rarely used as energy because when you
start breaking down proteins as energy, you start eating
your muscles, etc.
• Students are responsible for the hand-out
on the cell. There will be a quiz on the cell
and its parts.
• Atoms make molecules, molecules make
cells, cells make tissues, tissues make
organs, organs make systems, systems
make up people