Chapter 6 Chemistry in Biology

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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 naturally
• About 16 elements are man made
• Of 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 animals
• Examples 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 Levels
• 1st- closest to nucleus 2 electrons
• 2nd- next level out 8 electrons
• 3rd- 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 electrons
• 2 electrons in first energy level
• 8 electrons in second energy level
• 9 would be in third energy level but this is
  unstable
• 8 electrons in third
• 1 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 radiation
• Useful for X rays
• Useful for radioactive dating

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Chemistry in Biology
Chapter 6
6.1 Atoms, Elements, and Compounds
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.

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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 charge
• Gain electrons have a negative charge
• Ionic bonds are not as common as covalent in
  living organisms

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Chapter 6 Chemistry in Biology

• 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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Chemistry in Biology
Chapter 6
6.2 Chemical Reactions
Energy of Reactions

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

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Chemistry in Biology
Chapter 6
6.2 Chemical Reactions

• 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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Chemistry in Biology
Chapter 6
6.2 Chemical Reactions

• 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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Chemistry in Biology
Chapter 6
6.2 Chemical Reactions
Enzymes

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

• Enzymes are biological catalysts.

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Chemistry in Biology
Chapter 6
6.2 Chemical Reactions

• 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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Chemistry in Biology
Chapter 6
6.2 Chemical Reactions

• 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.

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

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Chapter 6 Chemistry in Biology

• 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 substance
• Solvent does the dissolving water
• Solute 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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Chemistry in Biology
Chapter 6
6.3 Water and Solutions

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

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Importance of Water

• Most lifes 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 polar
• Oxygen end negative
• Hydrogen 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 cohesion
• Causes adhesion

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Waters 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 glucose
• Two types simple and complex

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Simple Carbohydrates Sugars

• Monosaccharides one sugar
• Glucose
• Fructose
• Galactose
• Disaccharides two sugars
• Sucrose glucose and fructose
• Maltose glucose and glucose
• Lactose glucose and galactose

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Simple Carbohydrates Sugars
Fructose
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Complex Carbohydrates Polysaccharides

• Include starch, cellulose and glycogen
• All are chains of glucose
• Difference 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 acid
• Three types
• Diglycerides
• Triglycerides
• Sterols

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 eat
• Called fats and oils
• Contain 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 released
• After 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 nucleotide
• Phosphate group
• Sugar
• Nitrogen base
• Types RNA and DNA

Nucleotide
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DNA and RNA
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DNA

• Deoxyribonucleic acid
• Information storage for cell in cells nucleus
• Directs cells activities
• Genetic code blueprint
• Double helix

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RNA

• Ribonucleic acid
• Needed by DNA to make proteins
• Working copy of DNA
• Leaves the nucleus