KEY CONCEPTAll living things are based on atoms and their interactions.H:\chemistryppt.ppt

Living things consist of atoms of different elements.

An atom is the smallest basic unit of matter.An element is one type of atom.

H

O

Hydrogen atom (H)

Oxygen atom (O)

The nucleus has protons and neutrons. Electrons are in energy levels outside nucleus.

Oxygen atom (O)

Nucleus:8 protons (+)8 neutrons

outermost energy level: 6 electrons (-)

inner energy level: 2 electrons (-)

• An atom has a nucleus and electrons.

water (H2O)

OHH

_

++

• A compound is made of atoms of different elements bonded together.

carbon dioxide (CO2)

• A compound is made of atoms of different elements bonded together.

– water (H2O)

many other carbon-based compounds in living things

• A compound is made of atoms of different elements bonded together.

– water (H2O)

– carbon dioxide (CO2)

Ions form when atoms gain or lose electrons.

An ion is an atom that has gained or lost one or more electrons. positive ions negative ions

Ionic bonds form between oppositely charged ions.

Sodium atom (Na) Chlorine atom (CI) Sodium ion (Na+) Chloride ion (CI-)

Na loses anelectron to CI ionic bond

gained electron

Atoms share pairs of electrons in covalent bonds.

A covalent bond forms when atoms share a pair of electrons.

covalent bonds

Oxygen atom (O) Carbon atom (C) Oxygen atom (O)

Carbon dioxide (CO2 )

– multiple covalent bonds– diatomic molecules

Life depends on chemistry –all living things are made from chemical compounds which are used in chemical reactions to keep organisms alive

ELEMENT – made up of one kind of atom

Cannot be broken down into other substances by chemical means

More than 100 known , about 24 found in living organisms

CHEMICAL COMPOUND _- substance formed by the chemical combination of one or more elements in definite proportionsShown by a short hand form called CHEMICAL FORMULA which uses SYMBOLSPhysical and chemical properties usually very different from those of the elements from which they are formed

Silvery metal Yellowish gas

ATOM – basic unit of matter made up of subatomic particlesPROTONS - positively charged (+)NEUTRONS – no chargeStrong forces bind protons and neutrons bind together – NUCLEUS – at the center ATOMIC NUMBER= # of ProtonsELECTRON – negatively charged (-), are in constant motion

ISOTOPES – same number of protons in their atoms but different numbers of neutronsRADIOACTIVE ISOTOPE _ nucleus breaks down or decays overtime, giving off radiation in the form of matter and energy

Bone scan using isotope

ELECTRONS AND REACTIVITY – Electrons in the highest energy level of an atom determines how the atom reacts1st / lowest energy level – can hold 2 electrons2nd / highest energy level – can hold 8 electrons , when there is a partially filled energy level the atoms become chemically reactive, tend to react with other atomsPartially filled energy

levels

Ionic Bond – when an atom transfers an electron to another atomAn atom that loses electrons has a positive charge An atom that gains electrons has a negative charge

Covalent Bonds – when two atoms share electrons

When the atoms share 2 electrons the bond is called a single covalent bond

Sometimes,atoms share 4 electrons and form a double bond

2 or more atoms held together by covalent bonds form a MOLECULECan be modeled as a STRUCTURAL FORMULA – which is the number and types of atoms linked together by bonds Number and types of atoms in a molecule are designated by a CHEMICAL FORMULASPACE FILLING MODEL – drawing that depicts a 3-dimensional model

Molecules become rearranged into other molecules as existing chemical bonds break (absorbing energy from the surroundings).

Such changes, which result in the formation of one or more new substances are called CHEMICAL REACTIONS

Starting materials for the reaction – REACTANTS

Ending materials in the reaction - PRODUCTS

Hydrogen +Oxygen ------ Water + Energy

Reactants

Products

OHH

_

++

Life depends on hydrogen bonds in water.

Water is a polar molecule. Polar molecules have slightly charged regions.

– Nonpolar molecules do not have charged regions.– Hydrogen bonds form between slightly positive    hydrogen atoms and slightly negative atoms.

Hydrogen bonds are responsible for three important properties of water.

– high specific heat– cohesion– adhesion

Many compounds dissolve in water.

A solution is formed when one substance dissolves in another. A solution is a homogeneous mixture. Solvents dissolve other substances. Solutes dissolve in a solvent.

solution

“Like dissolves like.”

– Polar solvents dissolve polar solutes.– Nonpolar solvents dissolve nonpolar solutes.– Polar substances and nonpolar substances generally

remain separate.

Some compounds form acids or bases.

An acid releases a hydrogen ion when it dissolves in water. high H+ concentration pH less than 7

more acidic

stomach acid pH between 1 and 3

A base removes hydrogen ions from a solution.

– low H+ concentration– pH greater than 7

bile pH between 8 and 9

more basic

A neutral solution has a pH of 7.

pure water pH 7

Water molecule

Water Molecule is polar because there is an uneven distribution of electrons between the oxygen and hydrogen atoms- so they have regions with partial positive and negative chargeADHESION – attraction between unlike moleculesCOHESION – tendency of molecules of the same kind to stick together. Much stronger for water than most liquids

LOW DENSITY OF ICE – high density substance is always “tightly packed” than a low density substanceWater is the opposite – solid form(ICE) is less dense –so it floatsFloating ice insulates the water below allowing life to persist

THERMAL ENERGY – total amount of energy associated with the random movement of atoms and molecules in a sampleTEMPERATURE- measure of the average energy of random motion of the particles in a substanceWhen 2 substances differ in temperature, thermal energy in the form of heat is transferred from the warmer to the cooler one

SOLUTION – a uniform mixture of 2 or more substances SOLVENT – the substance that dissolves the other substance (water), Present in a greater amountSOLUTE – the substance that is dissolved. Present in a lesser amountAQUEOUS SOLUTION _ when water is the solventWater surround and separates the positive and negative ions

Some materials do not dissolve when placed in water but separate into pieces so small that they do not settle out. The movement of water molecules keep the small pieces suspended. Such mixtures of water and non dissolved materials are known as SUSPENSIONSEXAMPLE - blood

ACIDIC SOLUTIONS – contain higher concentrations of H+ ions than pure water and have pH values from 1-6ALKALINE (BASIC) SOLUTIONS - lower concentrations of H+ than pure water and have pH values of 8-14, higher concentrations of OH-pH SCALE – how acidic or alkaline (basic) a solution is

BUFFERS are weak acids or bases that can react with strong acids or bases to prevent sharp changes in pH

Important – because molecules in cells are very sensitive to concentrations of H+ or OH- ions. Even the slightest maybe harmful to living things.

If acids and bases are in equal proportion andthere is no excess of either H+ or OH- the solution is NEUTRAL and the process is calledNEUTRALIZATION

If acids and bases are in equal proportion and there is no excess of either H+ or OH-, the solution is called NEUTRAL and the process is called NEUTRALIZATION

KEY CONCEPTCarbon-based molecules are the foundation of life.

Carbon atoms have unique bonding properties.

Carbon forms covalent bonds with up to four other atoms, including other carbon atoms.

Carbon-based molecules have three general types of structures.– straight chain– branched chain– ring

Many carbon-based molecules are made of many small subunits bonded together.

– Monomers are the individual subunits.– Polymers are made of many monomers.

Four main types of carbon-based molecules are found in living things.

Carbohydrates are made of carbon, hydrogen, and oxygen.

Four main types of carbon-based molecules are found in living things.

Carbohydrates are made of carbon, hydrogen, and oxygen.

– Carbohydrates include sugars and starches.

– Monosaccharides are simple sugars.

– Polysaccharides include starches, cellulose, and glycogen.

Carbohydrates can be broken down to provide energy for cells.

• Some carbohydrates are part of cell structure.

Polymer (starch)

Starch is a polymer of glucose monomers that often has a branched structure.

Polymer (cellulose)

Cellulose is a polymer of glucose monomers that has a straight, rigid structure

monomer

– Many contain carbon chains called fatty acids.– Fats and oils contain fatty acids bonded to glycerol.

• Lipids are nonpolar molecules that include fats, oils, and cholesterol.

Triglyceride

Lipids have several different functions.

– broken down as a source of energy – make up cell membranes– used to make hormones

Fats and oils have different types of fatty acids.

– saturated fatty acids– unsaturated fatty acids

Phospholipids make up all cell membranes.

– Polar phosphate “head”– Nonpolar fatty acid “tails”

Phospholipid

Proteins are polymers of amino acid monomers.

– Twenty different amino acids are used to build proteins in organisms.

Amino acids differ in side groups, or R groups.

• Proteins are polymers of amino acid monomers.

– Twenty different amino acids are used to build proteins in organisms.

Amino acids are linked by peptide bonds.

• Proteins are polymers of amino acid monomers.

Amino acids differ in side groups, or R groups.

– Twenty different amino acids are used to build proteins in organisms.

Proteins differ in the number and order of amino acids.

– Amino acids interact to give a protein its shape.

– Incorrect amino acids change a protein’s structure and function.

hydrogen bond

Hemoglobin

Nucleic acids are polymers of monomers called nucleotides.

Nucleotides are made of a sugar, phosphate group, and a nitrogen base.

A phosphate group nitrogen-containing molecule,called a base

deoxyribose (sugar)

• Nucleic acids are polymers of monomers called nucleotides.

DNA stores genetic information.

• Nucleic acids are polymers of monomers called nucleotides.

– Nucleotides are made of a sugar, phosphate group, and a nitrogen base.

– RNA builds proteins.

DNA

RNA

KEY CONCEPT Life depends on chemical reactions.

Bonds break and form during chemical reactions.

Chemical reactions change substances into different ones by breaking and forming chemical bonds. Reactants are changed during a chemical reaction.

– Products are made by a chemical reaction.

• A reaction is at equilibrium when reactants and products form at the same rate.

CO2 + H2O H2CO3

Bond energy is the amount of energy that breaks a bond.– Energy is added to break bonds.– Energy is released when bonds form.

Chemical reactions release or absorb energy.

Activation energy is the amount of energy that needs to be absorbed to start a chemical reaction.

Exothermic reactions release more energy than they absorb.

– Reactants have higher bond energies than products.– Excess energy is released by the reaction.

Endothermic reactions absorb more energy than they release.

– Reactants have lower bond energies than products.– Energy is absorbed by the reaction to make up the

difference.

KEY CONCEPTEnzymes are catalysts for chemical reactions in living things.

A catalyst lowers activation energy.

Catalysts are substances that speed up chemical reactions. decrease activation energy increase reaction rate

Enzymes allow chemical reactions to occur under tightly controlled conditions.

Enzymes are catalysts in living things. Enzymes are needed for almost all processes.

– Most enzymes are proteins.

Disruptions in homeostasis can prevent enzymes from functioning.

– Enzymes function best in a small range of conditions.– Changes in temperature and pH can break hydrogen

bonds.– An enzyme’s function depends on its structure.

An enzyme’s structure allows only certain reactants to bind to the enzyme.

– substrates– active site

substrates (reactants)

enzyme

Substrates bind to anenzyme at certain places called active sites.

The lock-and-key model helps illustrate how enzymes function.

– substrates brought together– bonds in substrates weakened

Substrates bind to anenzyme at certain places called active sites.

The enzyme bringssubstrates together and weakens their bonds.

The catalyzed reaction formsa product that is releasedfrom the enzyme.