Matter, Mass, and Weight Matter: anything that occupies space and has mass

Mass: measurement of the amount of matter in an object

Mass does not change with location

Weight: measurement of the gravitational force acting on an object`s mass

Weight change with location

Elements: the simplest type of matter with unique chemical properties; composed of atoms of only one kind

118 total (90 natural) Twenty-five elements are essential to life Four of these make up about 96% of the weight of the

human body– C (18.5%)– O (65%)– H (9.5%)– N (3.3%)– Remaining 4% elements are

• (Ca,P,K,S,Na,Cl,Mg)

• Trace elements occur in

smaller amounts (less than 0.01%)

Atoms: Indivisible, smallest particle of an element that has chemical characteristics of that element

Composed of subatomic particles: Protons (p)

– Subatomic particles that carry positive charges– Found in the atom’s nucleus

Neutrons (n)– Carry NO charges– Found in atom’s nucleus

Electrons (e)– Carry negative charges– Orbit around the nucleus– Atoms are neutrally charged:

# electrons = # protons

• Atomic number= # of protons in nucleus of the atom

• Mass number = # of protons + # of neutrons

• Most of atom’s mass is in the nucleus• Electrons virtually weigh nothing!

• What is the mass number of Uranium??– (92 protons, 143 neutrons)– Answer = 235

• Isotopes:Atoms with the same # of protons but different # of

neutrons

Atoms with the same atomic number but different mass numbers

• What determines whether an atom will interact with others?

– The number & arrangement of electrons in outermost shell

– Atoms whose outer shell are not full tend to interact

– Electrons move around in orbitals

– First orbital holds 2 e’, Second orbital holds 8 e’

– X = 2N2 (X is maximum no. of electrons in energy level number n)

– Unfilled outer shell = READY TO BOND!!!, Very reactive

– Helium – First shell is full with 2 electrons – chemically unreactive

– Atoms whose outer shells are not full share or transfer electrons to other atoms, forming compounds by chemical bonding

– Two major types of chemical bonds between atoms form compounds• Ionic bonds• Covalent bonds

• Ionic Bonds: When atoms bond by losing/gaining electrons– When an atom loses or gains electrons, it becomes

electrically charged• Charged atoms are called ions• Cation: positively charged ion• Anion: negatively charged ion• Ionic bonds are formed between oppositely charged

ions

• Covalent Bonds: When atoms bond by sharing electrons• Atoms held together by covalent bond form a molecule

• Single covalent: two atoms share one pair of electrons

• Double covalent: Two atoms share 4 electrons

• Eg. Hydrogen gas, oxygen gas, methane etc.

Nonpolar covalent: When electrons are shared equally because nuclei attract the electrons equally. Eg. Methane, H2

Polar covalent: Electrons not shared equally because one nucleus attracts the electrons more than the other does. Eg. water

Molecules: two or more atoms chemically combine to form an independent unit– Eg. hydrogen molecule (H2), H2O

Compounds: a substance composed of two or more different types of atoms chemically combined– Eg. Sodium chloride (NaCl)

Molecular Mass: determined by adding up atomic masses of its atoms or ions– Eg. NaCl (22.99 + 35.45) = 58.44

• Forces between molecules

• Result from weak electrical attractions between neighboring ions and molecules. Eg. water

• Intermolecular forces are weaker than forces producing chemical bonding

Hydrogen Bonds Forms between polar covalent bond Polar covalent molecules have positive &

negative ends. Eg. Water Intermolecular force occur between these two

ends Hydrogen bond forms when the positively

charged H of one molecule is attracted to the highly negatively charged O, N or F of another molecule – For eg, in water the positively charged

hydrogen atoms of one water molecule form hydrogen bond with the negatively charged oxygen atoms of other water molecules

– Hydrogen bonds play an important role in determining the shape of complex molecules

– Eg. Water, DNA, RNA, Protein

Solubility: ability of one substance to dissolve in another. eg. sugar or salt dissolves in water

Polar subs. – soluble in water Nonpolar – Insoluble in water Dissociation or Separation: When ionic compds dissolve in

water – dissociate Ions separate and each becomes

surrounded by water molecules and keeping them in solution But when molecules (covalent

comps) dissolve in water – intact & surrounded by water. Eg. sugar

Electrolytes: Are solutions made by dissociation of cations (+) and anions (-) in water– Because they have the capacity to conduct an electric

current– Currents can be detected by electrodes– Eg. ECG

Nonelectrolytes: solutions made by molecules that dissolve in water, but do not dissociate; do not conduct electric current. Eg. water

Chemical Reactions – Change in the chemical composition of matter

Chemical reactions include:Reactants: substances that enter

into a chemical reactionProducts: substances that result

from the reactionChemical reactions cannot

create or destroy matter They only rearrange it Chemical bonds are formed (synthesis

reaction) and broken (decomposition reaction) during chemical reactions

Two or more reactants chemically combine to form a

new and larger product – Synthesis Reaction– Water is removed: Dehydration– Produce chemicals characteristic of life: carbohydrates, proteins,

lipids, nucleic acids, ATP.– All of Synthesis reactions occur within body – Anabolism– Anabolic reactions - Responsible for growth, maintenance and

repair

A large reactant is broken down to form smaller products – Decomposition Reaction– Water is added – Hydrolysis– All of decomposition reactions occur within body – Catabolism – Includes digestion of food molecules, breakdown of fat store

etc.– All of the catabolic and anabolic reactions - Metabolism

• Chemical reactions in which the reaction can proceed either from reactants to products or from products to reactants.

• Example: CO2 and H+ formation in plasma, an imp. reversible reaction takes place in the body

• CO2 + H2O H2CO3 H+ + HCO3

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Oxidation: loss of an electron by a substance

Reduction: gain of an electron by a substance

Eg. Sodium chloride Oxidation-Reduction Reactions: the loss of

an electron by one substance is accompanied by the gain of that electron by another substance

• Energy: The capacity to do work• Two types of energy

– Potential energy (PE): • stored energy• ball on top of hill about to

roll down– Kinetic energy (KE):

• energy of motion• Ball rolling down hill

– Thermodynamics– Is the study of energy transformations– The First Law of Thermodynamics

• Energy can be changed from one form to another but cannot be created or destroyed

– The Second Law of Thermodynamics• Energy transformations increase disorder, or entropy,

and some energy is lost as heat

Potential and kinetic energy can be found in different forms:

Mechanical Energy: energy resulting from the movement of objects

For eg. Moving a limb, breathing, circulating blood

Heat Energy: energy that flows between objects of different temperatures

- Always transferred from hotter object – cooler object

Chemical Energy: Is a form of potential energy

• Is found in food, gasoline, and other fuels

• When a chemical bond is broken from food and energy is released, only some of that energy is used to manufacture ATP.

• Energy that is released but not captured is released as heat.

• Heat is used by mammals to maintain body temperature.

Chemical reaction occurs only when molecules have sufficient kinetic energy to collide with each other

Activation Energy: Is the minimum energy that reactants must have to start a chemical reaction

Enzymes: Are protein catalysts that increase the rate of chemical reactions by lowering the activation energy necessary for reaction to begin

Activation Energy and Enzymes

Temperature affects rate of reaction– Increase in temperature means increase of kinetic

energy– Molecules move faster, collide harder and more

frequently

Concentration of reactants– As concentration of reactants increases, rate of

reaction increases, molecules come in contact with each other faster

– A decrease of O2 in cells can cause death as rate of aerobic chemical reactions decreases

Inorganic Chemistry: Generally, substances that do not contain carbon– Eg. Water, oxygen– Exceptions: CO, CO2, and HCO3

-

Organic Chemistry: Study of carbon-containing substances

– Water is basis of life – Weight of the human body

contains 50%–60% of water– Composed of one atom of O

and two atoms of H– Water molecules are polar– H bonds between the water

molecules hold the water molecule together

• High specific heat: large amount of heat required to raise temperature of water, resist large temp. fluctuations– Stabilizes body temperature

• Protection– Lubricant, eg. tears– fluid cushion around the organs eg. Cerebrospinal fluid

surround the brain

• Participates in chemical reactions– Many reactions take place in water– Dehydration and hydrolysis

Serves as a mixing medium Solution: mixture of liquids, gasses, or solids

that are uniformly distributed and chemically combined– Solvent: that which dissolves the solute, eg. water– Solute: that which dissolves in the solvent, eg. Salt

Mixture: substances physically blended but not chemically combined– Suspension: materials separate unless stirred. Eg.

Sand and water, Blood and plasma– Colloid: dispersal of tiny particles through a medium.

Eg. Milk

Acids and Bases

Acid: a proton donor or any substance that releases hydrogen ions

HCl H+ + Cl Base: a proton acceptor or any substance that binds

to or accepts hydrogen ions and release hydroxide ions (OH-)

NaOH Na+ + OH-

• Refers to the Hydrogen ion (H+) concentration in a solution– Neutral: pH of 7 or

equal hydrogen and hydroxide ions

– Acidic: a greater concentration of hydrogen ions

– Alkaline or basic: a greater concentration of hydroxide ions

– Physiologic pH is 7.4

• Help to counter strong shifts in pH

• Biological fluids contain buffers

• Buffers are substances that resist pH change

• They accept H+ ions when they are in excess

• They donate H+ ions when they are depleted

Important Inorganic Compounds

• Oxygen (O2): Inorganic molecule consisting of 2 O atom

• 21% of atmospheric gas is oxygen• Essential for most animals • O2 is required in the final step of series of reactions used to

extract energy from food

• Carbon dioxide (CO2): consist of 1 C and 2 O atom

• produced during exhalation– Metabolic waste product– Combines with water in plasma and forms H+ thus

affecting acid/base balance– More CO2 in body – toxic

• Organic chemistry is the study of carbon compounds• Carbon is a versatile atom

• It has four electrons in an outer shell that can hold eight electrons

• Carbon can share its electrons with other atom to form up to four covalent bonds

• And constitutes the backbone of many molecules

• Four major groups of Organic molecules• Carbohydrates• Lipids• Proteins• Nucleic acids

• Carbohydrates: composed of carbon, hydrogen, oxygen• Molecular formula – CH2O

• Eg. Glucose – C6H12O6

• Small sugar molecules in soft drinks• Long starch molecules in pasta and potatoes

- Monosaccharides

- Disaccharides

- Polysaccharides

Single sugars, carbohydrate monomer Glucose is found in sports drinks, found in blood (blood sugar) Fructose is found in fruit Six-carbon sugars like glucose, fructose, and galactose are

isomers , molecular formula is same (C6H12O6) but atoms are arranged differently

Very important in the diet as energy sources Five-carbon sugars like ribose and deoxyribose are components of

ATP, DNA and RNA

Two simple sugars bound together by dehydration Eg: sucrose or table sugar ( glucose + fructose)Lactose or milk sugar (glucose + galactose)Maltose or malt sugar ( glucose + glucose)

• Polysaccharides are polymers of monosaccharides linked together by dehydration reactions

• Some polysaccharides are energy storage molecules– Starch in plants– Glycogen in animals

• Cellulose – Polysaccharide found in plants - Important structural component of cell wall

• Lipids are hydrophobic, non-polar• Do not mix with water• Consist mostly of hydrocarbons, lower ratio of

oxygen and phosphorous and N in some lipids • Eg. Fats, phosphpholipids, steroids

• Fats are major type of lipid• Ingested and broken down by hydrolysis• Functions: protection, insulation, energy source• Dietary fat consists largely of the molecule triglyceride,

constitute 95% of fat• Triglyceride is a combination of glycerol and three fatty acids• Formed by dehydration reactions

• Fatty acids may be saturated or unsaturated– Saturated Fatty acid – contains all single bonds in the

carbon chain, which produces a more rigid structure– eg. butter– Unsaturated Fatty acid – contains one (mono) or more

(poly) double bonds in the carbon chain, which produces a more relaxed structure

– eg. Olive oil, corn oil, sunflower oil• Better because they do not stick to the inside of blood

vessels.

Phospholipids– Contain only two fatty acid

groups attached to glycerol– Have a phosphate group instead

of a third fatty acid attached to glycerol

Polar (hydrophilic) at one end; nonpolar (hydrophobic) at the other

Important structural component of cell membranes

Steroids are very different from fats in structure and function.

• The carbon atoms bound together into four ringlike structures

– Cholesterol is the “base steroid” from which our body produces other steroids.• For eg. bile salts, reproductive hormones estrogen,

progesterone, testosterone Important component of cell membrane

• A protein is a polymer constructed from amino acid monomers

• Functions– Structural: hair, cell cytoskeleton– Contraction: Actin and myosin in muscle are

responsible for muscle contraction– Storage: sources of amino acids, such as egg white– Defense: antibodies, membrane proteins– Transport: carriers of molecules such as

hemoglobin, membrane proteins– Signaling: hormones, membrane proteins– Enzymes: regulators of the speed biochemical

reactions

• Basic building blocks for proteins are 20 amino acid molecules

• Each amino acid contains– An amino group– A carboxyl group – A hydrogen atom– One of twenty side ("R") chains

• The three groups and a hydrogen atom are bonded to a central "alpha" carbon

Covalent bonds formed between amino acids during protein synthesis – peptide bond

Dipeptides are two amino acids longPolypeptides are from several to more than a thousand

amino acids long

• A protein's specific shape determines its function• A protein's shape depends on four levels of structure

• Primary structure: the unique sequence of amino acids forming the polypeptide

– A slight change in the primary structure of a protein affects its ability to function• The substitution of one amino acid for another in

hemoglobin causes sickle-cell disease

• Secondary structure: the folding or coiling of the polypeptide chain, caused by hydrogen bonding– May be pleated sheet or alpha

helix• Hydrogen bonds between amino acids

maintain the shape• If H bonds break – Protein becomes

nonfunctional – Denaturation• Denaturation caused by high temp., pH

change. Eg. eggs

• Tertiary structure: the overall three-dimensional shape of the polypeptide

• Results from folding of helices, pleated sheets or formation of covalent bond between S atom of one amino acid and S atom of another amino acid contribute to tertiary structure

• Quaternary structure: the aggregation of two or more polypeptide chains (subunits)

• eg. collagen

An enzyme is a protein catalyst - increases the rate of chemical reaction

Lower the activation energy necessary for a reaction to occur

Three-dimensional shape contains an active site where reactants attach.

Enzymes change shape to accommodate the shape of specific reactants: Induced Fit Hypothesis

To be functional, some enzymes require additional nonprotein substance – Cofactors

Cofactors can be ions, such as mg, zinc or an organic molecule– Organic molecule cofactors

called coenzymes

There are two types of nucleic acids:• DNA, deoxyribonucleic acid• RNA, ribonucleic acid

DNA – DNA is a genetic material of cells Copies of DNA are transferred from one

generation of cells to next DNA determines the structure of protein

Composed of 2 strands of nucleotides Each nucleotide is composed of a five-carbon

sugar (deoxyribose), a nitrogenous base, and a phosphate

– Each DNA nucleotide has one of the following nitrogenous bases:• Adenine (A)• Guanine (G)• Thymine (T)• Cytosine (C)

– Purines - A & G – Contains double C ring– Pyrimidines - T & C – Contains single C ring

• DNA is a double helix • Two strands of

polynucleotides are twisted around each other, forms ladder like structure – Double Helix

• Uprights of ladder are formed of sugar and phosphates

• Rungs of ladder – nitrogenous base

• Nitrogenous base connected to other base by H bond

• Complementary base pairing rule:• Adenine pairs with thymine• Cytosine pairs guanine

• Two strands of DNA are said to Complementary

• If base sequence of one strand is known – other can be predicted because of base pairing rule

• DNA strands – Antiparallel

• Sequence of base determines Protein structure

• DNA defines all cellular activities

– RNA, ribonucleic acid, is different from DNA.• Its sugar (ribose) has an extra OH group.• It has the base uracil (U) instead of thymine (T).• Single strand polynucleotide• Responsible for interpreting the code within DNA into

the primary structure of proteins

• Energy currency of the body• Consists of adenine, ribose and 3 phosphate

groups• Provides energy for other chemical reactions • All energy-requiring chemical reactions stop

when there is inadequate ATP