Chemistry and Physiological Reactions Chapter 2

Carbohydrates

Carbohydrates include sugars and starches
Contain C, H, and O

3 Classes

Monosaccharides

one single sugar

Monomers: the smallest unit of carbohydrate

Disaccharides

two sugars

Polysaccharides

many sugars

Lipids

Contain C, H, O and sometimes contain P
Insoluble in water

Many types

Triglycerides

Phospholipids

Steroids

Eicosanoids

Proteins

-Comprise 20–30% of cell mass
Have most varied functions of any molecules
→ Structural, chemical (enzymes), contraction (muscles)

-Contain C, H, O, N, and sometimes S and P

-Polymers of amino acid monomers held together by peptide bonds

-Shape and function due to four structural levels

Shapes of proteins fall into two categories

Fibrous

Strand like , water-insoluble, and stable

Most have tertiary or quaternary structure (3-D)

Provide mechanical support and tensile strength

keratin, elastin, collagen and contractile fibers

Globular

Compact, spherical, water-soluble, and sensitive to environmental changes

Tertiary or quaternary structure (3-D)

Contain specific functional regions (active sites)

antibodies, hormones and enzymes

Enzymes

globular proteins that act as biological catalysts

Catalysts regulate and increase the speed of chemical reactions without getting used up in the process
Lower the energy needed to initiate a chemical reaction
→ This leads to an increase in the speed of a reaction
→ Allows for millions of reactions per minute!

Nucleic Acids

Nucleic acids, composed of C, H, O, N, and P
Nucleic acid polymers are made up of monomers called nucleotides
→ Composed of a nitrogen base, a pentose sugar, and a phosphate group

Two major classes:

Deoxyribonucleic acid (DNA)

holds the genetic blueprint for the synthesis of all proteins

Ribonucleic acid (RNA)

Contains a ribose sugar (not deoxyribose)

Messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA)

ATP

The chemical energy released when glucose is broken down is captured in ATP (adenosine triphosphate)
ATP directly powers chemical reactions in cells
→ Offers immediate, usable energy needed by body cells

Structure of ATP

→ Adenine-containing RNA nucleotide with two additional phosphate groups

Acids

Are proton donors, they release hydrogen ions
E.g HCl (hydrochloric acid), H2CO3 (carbonic acid)

Bases

Are proton acceptors, they pick up hydrogen ions in solution
E.g HCO3– (bicarbonate ion)

pH Scale

-measurement of the concentration of hydrogen ions [H+] in a solution
-The more hydrogen ions in a solution, the more acidic that solution is
-pH is the negative logarithm of [H+] in moles per liter that ranges from 0–14
-The pH scale is logarithmic, so each pH unit represents a 10-fold difference

Buffers

-Acidity involves only free H+ in solution, not H+ that is bound
-Buffers resist abrupt and large swings in pH
Can release H+ if pH rises
-Can bind H+ if pH falls
-Buffers convert strong acids or bases into a weaker form
-Carbonic acid–bicarbonate system (important buffer system of blood)

All matter is composed of elements Elements are substances that cannot be broken down into simpler substances by ordinary chemical methods

Atoms are composed of three subatomic particles

Protons
→ Carry a positive charge (+)

Neutrons
→ Have no electrical charge (0)

Electrons

→ Carry a negative charge (-)

4 Elements make up our body

Carbon

Oxygen

Hydrogen

Nitrogen

Chemical bonds are “energy relationships” between electrons of exacting atoms
Electrons are the subatomic particles that determine what type of chemical bond is formed

Three Types of Chemical Bonds

Ionic Bonds

Ionic bonds involve the transfer of valence shell electrons from one atom to another, resulting in ions
One becomes an anion (negative charge)
→ An atom that gained one or more electrons One becomes a cation (positive charge)
→ An atom that lost one or more electrons
The attraction of opposite charges results in an ionic bond

Covalent Bonds

Covalent bonds are formed by sharing of two or more valence shell electrons between two atoms
Sharing of 2 electrons results in a single bond
Sharing of 4 electrons is a double bond
Sharing of 6 electrons is a triple bond
→ Allows each atom to fill its valence shell at least part of the time

Polar Covalent

Nonpolar Covalent

Hydrogen Bonds

The attractive force between electropositive hydrogen of one molecule and an electronegative atom of another molecule
Common between dipoles such as water
Also act as intramolecular bonds, holding a large molecule in a three-dimensional shape (eg DNA)

Chemical reactions occur when chemical bonds are formed, rearranged, or broken
These reactions can be written in symbolic forms called chemical equations

Reactants

Substances entering into a reaction together

Products

Resulting chemical end products

Synthesis Reaction

Smaller particles are bonded together to form larger, more complex molecules

Amino Acids

Decomposition Reaction

Bonds are broken in larger molecules, resulting in smaller, less complex molecules

Glycogen

Exchange Reactions

Bonds are both made and broken (also called displacement reactions)

ATP

Biochemistry is the study of chemical composition and reactions of living matter

All chemicals either organic or inorganic

Inorganic compounds

water, salts, and many acids and bases
Do not contain carbon

Water
Most abundant inorganic compound
Accounts for 60%–80% of the volume of living cells

Salts
Ionic compounds that dissociate into separate ions in water

-Separate into cations (positively charged molecules) and anions (negatively charged)
-All ions are called electrolytes because they can conduct electrical currents in a solution
-Ions play specialized roles in body functions

Example: sodium, potassium, calcium, and iron
Common salts in the body
NaCl, CaCO3, KCl, calcium phosphates

Organic compounds

Organic molecules contain carbon

Carbon shares electrons and form four covalent bonds with other elements

Carbs, fats, proteins, and nucleic acids
Contain carbon, are usually large, and are covalently bonded

Many Polymers are made up of similar units called monomers (building blocks )

Synthesized by dehydration synthesis

Broken down by hydrolysis reaction