Biological Chemistry

• Life is made up of matter

matter: occupies space & has mass

Biological Chemistry

mass:

weight:

• Matter consists of chemical elements

Chemical Elements

• 92 naturally occurring• 25 essential to life

THE TOP 10 ELEMENTS FOUND IN YOUR BODY

THE “BIG 4”

OTHER (4%)

96% of your body is composed of these 4 elements:

Nitrogen (3%)

Oxygen (65%)

Carbon (18.5%)

Hydrogen (9.5%)

Calcium

ChlorinePotassiumPhosphorus

SulfurSodium

• Trace amounts (less than 0.1%) of 15 other elements are also found in the body

Per

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• Elements consist of atoms

atom: smallest unit of matter that still has properties of an element

• Atoms are made of subatomic particles:

1) protons: positive charge

2) electrons: negative charge

3) neutrons: no charge (neutral)

THE ATOM: BASIC STRUCTURE

Nucleus

Hydrogen atom1 Proton0 Neutrons1 Electron

Carbon atom6 Protons6 Neutrons6 Electrons

Proton Neutron

Nucleus:

Electron

Forces of attraction between positive and negative charges hold the fast-moving electrons (negative) close to the nucleus (positive).

Examples of Atoms

Hydrogen1p+, 1e_

Helium2p+, 2e_

electron

proton

neutron

• All atoms of a given element have same number of protons = atomic number

Helium = 2 protons = atomic number =2

Carbon = 6 protons = atomic number = 6

• Same # protons & electrons, electrical charge = 0, what is charge of He?

atomic mass: protons + neutrons

C = 6 protons + 6 neutrons = 12

isotope:

Importance of Electrons

• Determine how atoms interact

• Energy level differences, higher energy farther from nucleus

electron shell: energy levels around nucleus in which electrons are found

ELECTRON SHELLS AND ATOM STABILITY

ELECTRON SHELLSElectrons move around the nucleus in designated areas called electron shells. An atom can have as many as seven electron shells in total.

First electron shell(capacity: 2 electrons)

Second electron shell(capacity: 8 electrons)

Vacancy

The chemical characteristics of an atom depend upon the number of electrons in its outermost shell.

Carbon6p+, 6e_

Oxygen8p+, 8e_

Sodium11p+, 11e_

Chlorine17p+, 17e_

How does a Reaction Occur?

• 2 atoms with incomplete e- shells, give/take of e-, such that both atoms gain full shells

Chemical bond: 2+ atoms attracted to one another by a reaction

molecule: 2+ atoms held together by chemical bond, e.g., water H2O

Types of Chemical Bonds

1) Ionic Bonds (e.g., NaCl = salt)

1 atom loses e- & 1 atom gains e-

Result = form ions or charged atoms

ionic bond: 2 ions with opposite charges are attracted to each other

SODIUMATOM11 p+

11 e-

electron transfer

CHLORINEATOM17 p+

17 e-

SODIUMION

11 p+

10 e-

CHLORINEION

17 p+

18 e-

Types of Chemical Bonds

2) Covalent Bonds (e.g., H2O)

2 atoms share outer shell e-

- The number of single covalent bonds is dependent on the # of e- needed to fill the outer shell

COVALENT BONDSOTHER EXAMPLES OF COVALENT BONDS

Each oxygen atom shares two electrons. This is called a double bond.

There are several different ways of representing molecular structure.

O2 molecule

“Space-filling”model

“Lewis”model

“Ball-and-stick”model

CH4molecule(methane)

Water: The Basis of All Life

polar covalent bonds: 2 atoms with very different electronegativities (attraction for shared e- in covalent bond) – results in charged molecule (+ & - ends)

hydrogen bonds: H(+) attracted to O(-)\

WATER: HIGH SURFACE TENSION

Pressure applied to water surface

“V”-shaped water molecules are held together by hydrogen bonds. The bonds are just strong enough to give water a surface tension with net-like properties.

Hydrogenbond

WATER: STRONG COHESIVENESSBecause of the cohesive properties of water, trees such as the giant sequoia are able to transport water molecules from the soil to their leaves 300 ft. above.

As each water molecule evaporates, it pulls additional water up through the tree because of the “sticky-ness” of the hydrogen bonds that link the water molecules.

Water molecule released into the atmosphere

300 ft.

Water molecule pulled into root system

Water molecules pulled upward

6-ft.-tall man

Frozen water

WATER: LOWER DENSITY WHEN FROZEN

FROZEN WATERHydrogen bonding arranges water molecules into a crystalline lattice, keeping them slightly farther apart and, therefore, less dense.

LIQUID WATERWater molecules move about freely, allowing them to be closer to one another.

RELATIVE AREA OCCUPIED BY THE SAME NUMBER OF H2O MOLECULES: Liquid water

Blood

THE pH SCALE

ACIDS BASES

H+ ion Water OH– ion

Bases are fluids that have a greater proportionof OH– ions to H+ ions.• OH– ions bind with H+ ions, neutralizingacids.• Strong bases are caustic to your skin.• Bases can be found in many household cleaners.• Bases are generally bitter in taste and soapy.

Acids are fluids that have a greater proportion of H+ ions to OH– ions.• H+ ions are very reactive.• Strong acids are corrosive to metals.• Acids break down food in your digestive tract.• Acids are generally sour in taste.

Beer

Soda

Battery acid

Coffee

Water

Ammonia

BleachBaking soda

Soda, with a pH of about 3.0, is 10,000 times more acidic than a glass of water, with a pH of 7.0!

0 7 141312111098654321

SUMMARY: THREE TYPES OF BONDS

1 COVALENT BONDA strong bond formed when atoms share electrons in order to become more stable, forming a molecule.

2 IONIC BONDAn attraction between two oppositely charged ions, forming a compound.

3 HYDROGEN BONDAn attraction between the slightly positively charged hydrogen atom of one molecule and the slightly negatively charged atom of another.

H2 molecule

Bon

d S

tren

gth

Strongest

Weakest

NaCl compound

H2O molecule H2O molecule

Four Macromolecules of Life

1) Carbohydrates (sugars = alcohol & aldehyde or ketone)

2) Lipids (fats = alcohol & carboxylic acid)

3) Proteins (made of amino acids)

4) Nucleic Acids

How are Polymers Made?

Dehydration Synthesis

- “free” monomers have H & OH groups

- Add “free” monomers to polymer chain = 1 H2O released

- Form new covalent bond between monomers

* Make polymers (macromolecules) for storage/transport, but cells must break them down to monomers in order to use them

Sucrose Formation

Glucose(monosaccharide)

Sucrose (disaccharide)

+ H2O

Fructose(monosaccharide)

How are Polymers Broken Down?

Hydrolysis (hydro = water; lysis = to break

- Reverse of dehydration synthesis

- Break covalent bond by adding water

- OH group to 1 monomer & H to adjacent monomer

Major Polysaccharides

cellulose

amylose (a starch)

glycogen

COMPLEX CARBOHYDRATES

FORMATIONBond(s) between simple sugars formed

Glucose Fructose

POLYSACCHARIDESComplex carbohydrates formed by the union of many simple sugars

DISACCHARIDESComplex carbohydrates formed by the union of two simple sugars

DIGESTIONBond(s) between simple sugars broken

Sucrose(table sugar)

Starch(consists of hundreds of glucose molecules)

ENERGY

Sugars broken down furtherSugars broken down further

ENERGY

Time

Blo

od s

ugar

leve

l

Time

Blo

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ugar

leve

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Complexcarbohydrates

Fructose

Depending on their structure, dietary carbohydrates can lead to quick-but-brief or slow-but-persistent increases in blood sugar.

DNA

• Double-stranded • Sugar-phosphate

backbone• Covalent bonds in

backbone• H bonds between

bases