Chemistry and Physiological Reactions Chapter 2

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Biochemistry

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

All chemicals either organic or inorganic

Organic compounds

Broken down by hydrolysis reaction

Synthesized by dehydration synthesis

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

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

Organic molecules contain carbon

Carbon shares electrons and form four covalent bonds with other elements

Inorganic compounds

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

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

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

Chemical Reactions

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

Exchange Reactions

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

Decomposition Reaction

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

Glycogen

Synthesis Reaction

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

Amino Acids

Products

Resulting chemical end products

Reactants

Substances entering into a reaction together

Chemical Bonds

Three Types of Chemical Bonds

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)

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

Nonpolar Covalent

Polar Covalent

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

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

Atoms and Elements

4 Elements make up our body

Nitrogen

Hydrogen

Oxygen

Carbon

Atoms are composed of three subatomic particles

Electrons → Carry a negative charge (-)

Neutrons → Have no electrical charge (0)

Protons → Carry a positive charge (+)

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

Acids and Bases

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)

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

Bases

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

Acids

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

Macromolecules

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

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:

Ribonucleic acid (RNA)

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

Contains a ribose sugar (not deoxyribose)

Deoxyribonucleic acid (DNA)

holds the genetic blueprint for the synthesis of all proteins

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

Globular

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!

antibodies, hormones and enzymes

Contain specific functional regions (active sites)

Tertiary or quaternary structure (3-D)

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

Fibrous

keratin, elastin, collagen and contractile fibers

Provide mechanical support and tensile strength

Most have tertiary or quaternary structure (3-D)

Strand like , water-insoluble, and stable

Lipids

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

Many types

Eicosanoids

Steroids

Phospholipids

Triglycerides

Carbohydrates

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

3 Classes

Polysaccharides

many sugars

Disaccharides

two sugars

Monosaccharides

Monomers: the smallest unit of carbohydrate

one single sugar