Here are the answers to the questions: - Carbohydrates are the most readily used source of cellular fuel. - Sucrose is classified as a disaccharide. - Glucose is classified as a monosaccharide. - A chemical reaction in which two smaller molecules unite to form a larger molecule (with the loss of water) is called dehydration synthesis. - A solution with a pH of 3 is considered acidic. - The molecules important in cell membranes include phospholipids and cholesterol.

1. Biochemistry for
Anatomy & Physiology Students
BIO 351
Our Lady of Holy Cross College

2. Elements
 All matter is composed of elements
– unique substances that cannot be
broken down into simpler substances
 Four elements – carbon, oxygen,
hydrogen, and nitrogen – make up
96% of our body weight
 Each element is composed identical
particles or building blocks called
atoms

3. Atoms

4. Periodic Table of Elements

5. Elements
 Different elements are composed of different #s of
protons, neutrons and electrons, and that is what
determines the unique properties of each element
 Atomic number = # of protons. It determines the
identity (name) of the element
 Atomic mass = sum of the masses of all of an
element’s protons and neutrons
 Isotopes of an element have the same # of protons
but different #s of neutrons
 Radioactive isotopes are unstable and disintegrate
spontaneously. Half-life is the amount of time for half
of the atoms to disintegrate
 Atomic weight = average of the mass #s of all
isotopes of an element, taking into account the
relative abundance of the isotopes

6. Elements in the Human Body
 26 of the elements are normally found in
the body
 Of these 11 are listed as major elements
because they are present in large amounts
 15 are called trace elements because they
are only present in tiny quantities
 H, O, N, and C are the most common
elements in the body. H forms 1 bond, O
forms 2 bonds, N forms 3 bonds, and C
forms 4 bonds

7. Subatomic Particles
 Proton is positively charged
 Neutron has no electrical charge
 Protons and neutrons have approximately
the same mass and are located in the
nucleus of the atom
 Electron has a negative charge and has
essentially no mass
 Atoms are electrically neutral. The positive
and negative charges (on protons and
electrons) are balanced

9. Atomic Model
 Planetary model – older model, electrons
orbit nucleus, are depicted in shells. Each
shell represents an energy level.
 Orbital model – more modern model, shows
an electron cloud which depicts probability
of finding an electron or electrons in a
particular region. Each electron shell
contains one or more orbitals.

10. Molecules
 Two or more atoms may combine to
form a distinctive type of particle called
a molecule
 If atoms of the same element combine,
they produce molecules of that element
 2 or more different elements can
combine to form molecules of a
compound.
 Exs: The chemical formula for water is
H2O. (Two atoms of hydrogen and one
atom of oxygen form each molecule.)
CO2 is carbon dioxide.

11. Chemical Bonds
 Reactivity of an atom is related to the # of
electrons in outermost shell
 Shell 1 can hold a maximum of 2 electrons.
 Octet rule – all other shells hold a
maximum of 8 electrons.
 When the outermost shell of an atom is full,
the atom is stable, i.e. chemically inert
 3 types of bonds: ionic, covalent, hydrogen

12. Ionic Bonds

13. Covalent Bonds

15. Water--H2O
 Water makes up 60—80% of the volume of
most living cells.
 It is a polar molecule, meaning that it has
unequal electron bond sharing.
 Water is the universal solvent. (Substance
dissolved in a solvent is called a solute.)
 Hydrogen bonds form between water molecules
as well as between other strongly polar
molecules.
 Hydrogen bonds are responsible for the high
surface tension of water
 and are responsible for the three-
dimensional shape of proteins and DNA.

16. Water
molecules
showing the
hydrogen
bonding that
exists between
negatively
charged
oxygen and
positively
charged
hydrogen.

18. Acids and Bases
 Electrolytes are substances that dissociate (break up) in
solution to form charged particles called ions. These
include acids, bases, and salts.
 Acids dissociate in water to yield hydrogen ions (which is
a bare proton) and anions (negatively charged particles).
They are proton donors
 Bases absorb hydrogen ions. (They are proton
acceptors.)
 The relative concentration of hydrogen ions is measured
in concentration units called pH units.
 The pH scale extends from 0—14; a pH of 7 is neutral; a
pH below 7 is acidic; a pH above 7 is basic or alkaline.
 Acids and bases neutralize each other. When mixed
together they form a salt and water.
 Buffers are substances which resist large fluctuations in
pH that would damage living tissues.

20. What is the pH range
of urine?
Of human blood?
Of saliva?
Of gastric juice?
Why is the pH of
gastric juice so acidic?
Why is the pH of
distilled water 7?

21. Organic Compounds
 Carbon containing compounds that
have C – C or C – H bonds
 The 4 kinds of organic
compounds we will
study are:
 Carbohydrates
 Lipids
 Proteins
 Nucleic Acids

22. Proteins, nucleic acids, polysaccharides and
lipids are the most abundant biomolecules

23. Carbohydrates
 This group of molecules includes sugars and
starches.
 All carbohydrates contain carbon, hydrogen,
and oxygen in a 1:2:1 ratio.
 Represent 1—2% of cell mass.
 Major function: to provide energy for cellular
work.
 Monosaccharides: simple sugars with 5 or 6
carbons in a single ring structure. Examples
are glucose (blood sugar), fructose (fruit
sugar), and galactose.

24. Examples of Monosaccharides
Glucose, fructose, and galactose have the
same chemical formulas (therefore they are
isomers), but differ in their structure (3
dimensional arrangement of their atoms). They
all have 6 carbons, so they are called hexoses.
Deoxyribose and ribose are both 5 carbon
sugars. They are called pentoses.

25. Carbohydrates, continued
 Disaccharides are formed when two
monosaccharides are joined in a chemical
reaction called dehydration synthesis.
 Biologically important disaccharides are lactose
(milk sugar), sucrose (table sugar), and
maltose.
 Polysaccharides are long chains of
monosaccharides linked together by
dehydration synthesis.
 Examples are glycogen (animal starch) and
cellulose. Where is glycogen found in the
body?

26. Glycogen is
stored in the liver
and in skeletal
muscle tissue.

27. Sucrose: a disaccharide

28. Lactose: milk sugar

29. The top reaction is the one that you will model in the
laboratory. Notice that a water molecule is lost when
the two monosaccharides are combined in the
synthesis reaction.

30. Note the branching in the
polysaccharide chain shown above.

31. Plant starch, a
digestible
polysaccharide

32. The cellulose
of plant cell
walls is
indigestible.

33. Hydrolysis
 Larger molecules are broken down
into smaller molecules in a process
called hydrolysis, literally to “break
with water.”
 When this occurs in the digestive
tract and is catalyzed by enzymes we
call it chemical digestion.

35. Lipids
 Insoluble in water but dissolve readily in
nonpolar solvents.
 Contain carbon, hydrogen, and oxygen, but
much less oxygen than carbohydrates. Some
lipids, called phospholipids, contain P.
 Types of lipids: neutral fats, phospholipids, and
steroids.
 Neutral fats are also called triglycerides and are
called fats when solid at room temperature and
oils when liquid at room temperature. They
are used for energy storage and pad and
protect organs.

36. Triglycerides are made up of glycerol and three
fatty acids. If the chemical bonds between the
carbon chains in the fatty acids are single, the
fat is saturated. They are solid at room temp. If
at least one double bond is present, the fat is
unsaturated. They tend to be liquid at room
temp.

37. Functions and Locations of
Neutral Fats
 Serve as energy reserves.
 Protect the body from temperature
extremes.
 Cushion vital organs.
 Fats are located in the subcutaneous
tissue and around body organs.

38. Section through the abdomen (Visible Human Project)

39. Phospholipids have a phosphate-containing group
that substitutes for a fatty acid, giving the
molecule a polar “head.” They are amphipathic,
meaning they have polar and nonpolar regions.
These molecules are important constituents of cell
membranes.

40. Chemical Structure
Nonpolar tails
Polar head

41. Steroids
 Classified with fats, but very different in
structure—made up of four interlocking
hydrocarbon rings.
 Fat soluble
 Examples: cholesterol, cortisol, aldosterone,
estrogen, testosterone, progesterone
 Cholesterol is the most important of the
steroids. Only found in foods of animal origin
 It is an important component of cell
membranes.
 It is the raw material of vitamin D synthesis.
 It is the raw material for the synthesis of
steroid hormones.

42. cholesterol

44. Some common chemical groups
 Hydroxyl –OH-
 Methyl -CH3
 Ethyl -CH2CH3
 Carboxyl –COOH
 Phosphate group –PO4
-3

45. Cholesterol’s Function in the Cell
Membrane
 It makes the lipid
bilayer less
deformable and
decreases its
permeability to
small water-soluble
molecules.
 The other
molecules shown
are the
phospholipids.

46. Questions
 Which organic molecules are the most readily
and used source of cellular fuel?
 Sucrose is classified as a __________.
 Glucose is classified as a __________.
 A chemical reaction in which two smaller
molecules unite to form a larger molecule (with
the loss of water) is called _____________.
 A solution with a pH of 3 is considered
________(acidic, alkaline).
 The molecules important in cell membranes
include ________________.