1 chapter 6 chemistry in biology 6.1 atoms, elements and compounds

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Chapter 6 Chemistry in Biology

6.1 Atoms, Elements and Compounds

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Elements

Everything is made of substances called elements

About 90 elements occur naturallyAbout 16 elements are man madeOf the 90 naturally occurring elements,

only 25 are essential to living things

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Periodic Table of the Elements

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Reading the Periodic Table

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Periodic Table of the Elements

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Needed in Macro-amounts

Oxygen 65%Carbon 18.5%Hydrogen 9.5%Nitrogen 3.3%

Other elements are needed in trace amounts

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Trace Elements

All organisms need trace elements even though they are needed in very small amounts they are essential for life

Plants absorb the trace elements from the soil

Animals eat the plants and other animalsExamples: iron, magnesium, gold,

arsenic, copper and many others

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Atoms: The Building Blocks of Elements

Atoms is the smallest particle of an element that has the characteristics of that element

Nucleus contains protons (+) and neutrons (0)

Electrons (-) in “cloud” around nucleus

Carbon atom

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Electron Energy Levels

Certain numbers of electrons can occupy different regions around the nucleus of an atom

Energy Levels1st- closest to nucleus: 2 electrons2nd- next level out: 8 electrons3rd- further level out: 18 electrons

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Electron Energy Levels

Closest energy levels are always filled first

Carbon atoms have 6 electrons

2 electrons are in the first energy level

The remaining 4 electrons fill the second energy level

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Potassium Energy Levels

19 total electrons2 electrons in first

energy level8 electrons in second

energy level9 would be in third

energy level but this is unstable8 electrons in third1 electron in fourth

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Isotopes of an Element

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Isotopes of an Element

Atoms that have different numbers of neutron but the same number of protons

Have same protons (atomic number) but different numbers of neutrons (atomic mass)

Most isotopes are unstable and the nuclei break apart and give off radiationUseful for X raysUseful for radioactive dating

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Chemistry in Biology

van der Waals Forces

When molecules come close together, the attractive forces between slightly positive and negative regions pull on the molecules and hold them together.

The strength of the attraction depends on the size of the molecule, its shape, and its ability to attract electrons.

6.1 Atoms, Elements, and CompoundsChapter 6

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Compounds and Bonding

Compounds: composed of two or more different elements that are chemically combined (bonded)

Chemical bonds hold atoms together so that they are more stable

Atoms are more stable when they have their outer electron energy levels filled

Bonds can be covalent or ionic

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Covalent Bonds

Atoms share electrons

Covalent means cooperate

A molecule is a group of atoms held together by covalent bonds

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Ionic Bonds

Ionic bonds involve gaining or losing electrons

Na has lost an electron and now has a positive charge

Cl has gained and electron and now has a negative charge

Opposite charges attract

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Ionic Bonds

Ions are atoms that have gained or lost electrons

Lose electron have a positive chargeGain electrons have a negative chargeIonic bonds are not as common as

covalent in living organisms

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6.2 Chemical Reactions

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Chemical Reactions

When chemical reaction occur, bonds between atoms are formed or broken causing substances to combine and recombine as different molecules

All of the chemical reactions that take place in an organism is called metabolism

Chemical reaction depend on many things: temperature, concentration and pH

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Balancing Chemical Reactions

Matter cannot be created or destroyed only changed in form

So all atoms must be accounted for in a chemical reaction

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Balancing Chemical Reactions

What you start with (reactants) must equal what you end up with (products)

2H2 + O2 2H2O

2 x 2 H 2 x 2 2 O 2 x 1

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The activation energy is the minimum amount of energy needed for reactants to form products in a chemical reaction.

Energy of Reactions

6.2 Chemical ReactionsChapter 6

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This reaction is exothermic and released heat energy.

The energy of the product is lower than the energy of the reactants.


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This reaction is endothermic and absorbed heat energy.The energy of the products is higher than the energy of the reactants.


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A catalyst is a substance that lowers the activation energy needed to start a chemical reaction.

Enzymes are biological catalysts.

It does not increase howmuch product is made and it does not get

used up in the reaction.

Enzymes


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The reactants that bind to the enzyme are called substrates.

The specific location where a substrate binds on an enzyme is called the active site.


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Factors such as pH, temperature, and other substances affect enzyme activity.


The active site changes shape and forms the enzyme-substrate complex, which helps chemical bonds in the reactants to be broken and new bonds to form.

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6.3 Water and Solutions

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Mixtures and Solutions

Mixtures are combinations of substances in which the individual components retain their own properties, like sand and salt mixed together, no chemical reactions have taken place

Solutions are a type of mixture where one substance dissolves in another substanceSolvent does the dissolving: waterSolute gets dissolved: sugar

Solutions are very important in living things as we are ~75% water

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Acids and Bases

pH is a measure of how acidic or basic a substance is

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Ph Scale

Most of our foods are acidic

Most of our cleaning supplies are basic (alkaline)

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Blood pH

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Buffers are mixtures that can react with acids or bases to keep the pH within a particular range.

6.3 Water and SolutionsChapter 6

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Importance of Water

Most life’s process (chemical reactions) can only happen in water

Water is a transport medium: blood and sap

Water has a high specific heat; holds heat and requires more heat to change its temperature; works like an insulator

Water expands when it freezes, less dense; ice floats on top

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Structure of Water

Chemical formula: H2O

Water is polarOxygen end negativeHydrogen end positive

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Polar Covalent Bonds

The electron in the covalent bond between the hydrogen and oxygen spends more time with the oxygen

Causes the oxygen end to be slightly negative, hydrogen end to be slightly positive

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Hydrogen Bonds Form due to Polarity

Hydrogen bonds are weak bonds between molecule

Positive end of one molecule is attracted to negative end of another molecule

Causes cohesionCauses adhesion

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Water’s Hydrogen Bonds

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Chapter 6 The Chemistry of Life

6.4 The Building Blocks of Life

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Carbon

Carbon is the element present in all life substances

Carbon has a unique structure Shares four electrons Forms four covalent

bonds Can have single, double,

or triple bonds Because of bonding some

molecules of the same formula can have different shapes

CH4 Methane

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Carbon

Glucose has formula C6H12O6

Fructose has formula C6H12O6

Isomers have same formula but different

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Carbohydrates

Contain carbon, hydrogen, and oxygen

Subunit : glucoseTwo types simple and

complex

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Simple Carbohydrates: Sugars

Monosaccharides: one sugarGlucoseFructoseGalactose

Disaccharides: two sugarsSucrose: glucose and fructoseMaltose: glucose and glucoseLactose: glucose and galactose

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Simple Carbohydrates: Sugars

Fructose

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Complex Carbohydrates: Polysaccharides

Include starch, cellulose and glycogenAll are chains of glucoseDifference is how the chains are put

together and type of bonds holding the glucose together

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Starch

Carbohydrate storage for plants

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Cellulose

Carbohydrate structural support for plants and algae

Found in the cell wall to give the cell structure and support

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Glycogen

Carbohydrate storage for animals

Found in liver and can move to any location

Found in muscle and only stays in that muscle

Liver Cell

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Lipids

Contain carbon, hydrogen, and oxygen

Subunit: fatty acidThree types:

DiglyceridesTriglyceridesSterols

Many more carbon-hydrogen bonds to store large amounts of energy

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Fatty Acids

Can be saturated with hydrogen and have no double bonds (most animal fats)

Can have double bonds and be unsaturated (most plant fats)

Health risks associated with saturated fats

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Diglycerides

A Phosphodiglyceride is the main part of cell membranes

Not a large component of our body

Not a large component of the food we eat

Contain a glycerin backbone and two fatty acid chains

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Triglycerides

The most common lipid

Found in our bodies Found in the food we

eatCalled fats and oilsContain a glycerin

backbone and three fatty acid chains

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Sterols

Contain four interconnected carbon rings

Common one is cholesterol

Many other sterols are made from cholesterol

Some hormones are sterols

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Proteins

Contain, carbon, hydrogen, oxygen and nitrogen

Subunit: amino acid 20 different amino acids Linked by peptide bond

Types: structural protein and enzymes Structural- build a part Enzymes- control the rate

of chemical reactions

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Enzymes

Works on a specific substrate

Lock and key fit with the substrate

Products are releasedAfter reaction the

enzyme resumes its original shape and can react again with another substrate

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Nucleic Acids

Contain carbon, hydrogen, oxygen, nitrogen and phosphorus

Subunits: nucleotidePhosphate groupSugarNitrogen base

Types: RNA and DNA Nucleotide

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DNA and RNA

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DNA

Deoxyribonucleic acidInformation storage

for cell in cell’s nucleus

Directs cell’s activitiesGenetic code

blueprintDouble helix

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RNA

Ribonucleic acidNeeded by DNA to

make proteinsWorking copy of DNALeaves the nucleus

1 chapter 6 chemistry in biology 6.1 atoms, elements and compounds

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