Download 2.1 Atoms, Ions, and Molecules

2.1 Atoms, Ions, and Molecules
KEY CONCEPT
All living things are based on atoms and their
interactions.
2.1 Atoms, Ions, and Molecules
Living things consist of atoms of different elements.
• An atom is the smallest basic unit of matter.
• An element is one type of atom.
Hydrogen atom (H)
H
Oxygen atom (O)
O
2.1 Atoms, Ions, and Molecules
• An atom has a nucleus and electrons.
– 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 (-)
2.1 Atoms, Ions, and Molecules
• A compound is made of atoms of different elements
bonded together.
– water (H2O)
_
O
H
+
H
+
2.1 Atoms, Ions, and Molecules
• A compound is made of atoms of different elements
bonded together.
– water (H2O)
– carbon dioxide (CO2)
2.1 Atoms, Ions, and Molecules
• A compound is made of atoms of different elements
bonded together.
– water (H2O)
– carbon dioxide (CO2)
– many other carbon-based compounds in living things
2.1 Atoms, Ions, and Molecules
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.
gained electron
Na loses an
electron to CI
Sodium atom (Na)
Chlorine atom (CI)
ionic bond
Sodium ion (Na+)
Chloride ion (CI-)
2.1 Atoms, Ions, and Molecules
Atoms share pairs of electrons in covalent bonds.
• A covalent bond forms when atoms share a pair of
electrons.
– multiple covalent bonds
– diatomic molecules
covalent bonds
Oxygen atom (O)
Carbon atom (C)
Carbon dioxide (CO2 )
Oxygen atom (O)
2.2
Properties
Water
2.1 Atoms,
Ions,ofand
Molecules
KEY CONCEPT
Water’s unique properties allow life to exist on
Earth.
2.2
Properties
Water
2.1 Atoms,
Ions,ofand
Molecules
Life depends on hydrogen bonds in water.
• Water is a polar molecule.
– Polar molecules have slightly charged regions.
_
O
H
+
H
+
– Nonpolar molecules do not have charged regions.
– Hydrogen bonds form between slightly positive
hydrogen atoms and slightly negative atoms.
2.2
Properties
Water
2.1 Atoms,
Ions,ofand
Molecules
• Hydrogen bonds are responsible for three important
properties of water.
– high specific heat
– cohesion
– adhesion
2.2
Properties
Water
2.1 Atoms,
Ions,ofand
Molecules
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
78 % Nitrogen
20% Oxygen
1% Other
What are the solutes and solvent in the beverage you drink?
2.2
Properties
Water
2.1 Atoms,
Ions,ofand
Molecules
• “Like dissolves like.” (Universal Solvent)
– Polar solvents dissolve polar solutes.
– Nonpolar solvents dissolve nonpolar solutes.
– Polar substances and nonpolar substances generally
remain separate.
2.2
Properties
Water
2.1 Atoms,
Ions,ofand
Molecules
Some compounds form acids or bases.
• An acid releases a hydrogen ion when it dissolves in
water.
– high H+ concentration
– pH less than 7
stomach acid pH between 1 and 3
more acidic
2.2
Properties
Water
2.1 Atoms,
Ions,ofand
Molecules
• A base removes hydrogen ions from a solution.
– low H+ concentration
– pH greater than 7
bile pH between 8 and 9
more basic
2.2
Properties
Water
2.1 Atoms,
Ions,ofand
Molecules
• A neutral solution has a pH of 7.
pure water pH 7
Cells have higher H+ concentrations than blood. Which has a
higher pH? Why?
2.3
CarbonIons,
based
2.1 Atoms,
andMolecules
Molecules
KEY CONCEPT
Carbon-based molecules are the foundation of life.
2.1 Atoms, Ions, and Molecules
2.3
CarbonIons,
based
2.1 Atoms,
andMolecules
Molecules
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
2.3
CarbonIons,
based
2.1 Atoms,
andMolecules
Molecules
• Many carbon-based molecules are made of many small
subunits bonded together.
– Monomers are the individual subunits.
– Polymers are made of many monomers.
2.3
CarbonIons,
based
2.1 Atoms,
andMolecules
Molecules
Four main types of carbon-based molecules are found in living things.
A phosphate group
Nucleic Acids
deoxyribose (sugar)
nitrogen-containing
molecule, called a base
2.3
CarbonIons,
based
2.1 Atoms,
andMolecules
Molecules
Four main types of carbon-based molecules are found in
living things.
• Carbohydrates are made of carbon, hydrogen, and
oxygen in a 1:2:1 ratio.
2.3
CarbonIons,
based
2.1 Atoms,
andMolecules
Molecules
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.
2.3
CarbonIons,
based
2.1 Atoms,
andMolecules
Molecules
• Carbohydrates can be broken down to provide
energy for cells.
• Some carbohydrates are part of cell structure.
Polymer (starch - storage)
Starch is a polymer of
glucose monomers that
often has a branched
structure.
Polymer (cellulose – cell structure)
monomer
Cellulose is a polymer
of glucose monomers
that has a straight, rigid
structure
2.3
CarbonIons,
based
2.1 Atoms,
andMolecules
Molecules
• Lipids are nonpolar molecules that include fats, oils, and
cholesterol. Consist of Carbon, Hydrogen & Oxygen
– Many contain carbon chains called fatty acids.
– Fats and oils contain fatty acids bonded to glycerol.
Triglyceride
2.3
CarbonIons,
based
2.1 Atoms,
andMolecules
Molecules
• Lipids have several different functions.
– broken down as a source of energy & insulation
– make up cell membranes
– used to make hormones
2.3
CarbonIons,
based
2.1 Atoms,
andMolecules
Molecules
• Fats and oils have different types of fatty acids.
– saturated fatty acids
– unsaturated fatty acids
2.3
CarbonIons,
based
2.1 Atoms,
andMolecules
Molecules
• Phospholipids make up all cell membranes.
– Polar phosphate “head”
– Nonpolar fatty acid “tails”
Phospholipid
2.3
CarbonIons,
based
2.1 Atoms,
andMolecules
Molecules
• Proteins are polymers of amino acid monomers
– Carbon, Hydrogen, Oxygen & Nitrogen
– Twenty different amino acids are used to build proteins
in organisms.
2.3
CarbonIons,
based
2.1 Atoms,
andMolecules
Molecules
• 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.
– Amino acids are linked by peptide bonds.
2.3
CarbonIons,
based
2.1 Atoms,
andMolecules
Molecules
• Proteins differ in the number and order of amino acids.
– Amino acids interact to give a protein its shape.
Hemoglobin
hydrogen bond
– Incorrect amino acids change a protein’s structure
and function.
2.4
Chemical
Reactions
2.1 Atoms,
Ions,
and Molecules
• Nucleic acids are polymers of monomers called
nucleotides.
2.5
Enzymes
2.1 Atoms,
Ions, and Molecules
• Nucleic acids are polymers of monomers called
nucleotides.
– Nucleotides are made of a sugar, phosphate
group, and a nitrogen base.
A phosphate group
deoxyribose (sugar)
nitrogen-containing molecule,
called a base
2.5
Enzymes
2.1 Atoms,
Ions, and Molecules
• Nucleic acids are polymers of monomers called
nucleotides.
– Nucleotides are made of a sugar, phosphate
group, and a nitrogen base.
– DNA stores genetic DNA
information.
– RNA builds proteins. RNA
2.4
Chemical
Reactions
2.1 Atoms,
Ions,
and Molecules
KEY CONCEPT
Life depends on chemical reactions.
2.4
Chemical
Reactions
2.1 Atoms,
Ions,
and Molecules
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.
CO2 + H2O
H2CO3
2.4
Chemical
Reactions
2.1 Atoms,
Ions,
and Molecules
• Bond energy is the amount of energy that breaks a bond.
– Energy is added to break bonds.
– Energy is released when bonds form.
• A reaction is at equilibrium when reactants and products
form at the same rate.
CO2 + H2O
H2CO3
2.4
Chemical
Reactions
2.1 Atoms,
Ions,
and Molecules
Chemical reactions release or absorb energy.
• Activation energy is the amount of energy that needs
to be absorbed to start a chemical reaction.
2.4
Chemical
Reactions
2.1 Atoms,
Ions,
and Molecules
• Exothermic reactions release more energy than they
absorb.
– Reactants have higher bond energies than products.
– Excess energy is released by the reaction.
2.4
Chemical
Reactions
2.1 Atoms,
Ions,
and Molecules
• 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.
2.5
Enzymes
2.1 Atoms,
Ions, and Molecules
KEY CONCEPT
Enzymes are catalysts for chemical reactions in
living things.
2.5
Enzymes
2.1 Atoms,
Ions, and Molecules
A catalyst lowers activation energy.
• Catalysts are substances that speed up chemical
reactions.
– decrease activation energy
– increase reaction rate
2.5
Enzymes
2.1 Atoms,
Ions, and Molecules
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.
2.5
Enzymes
2.1 Atoms,
Ions, and Molecules
• 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.
2.5
Enzymes
2.1 Atoms,
Ions, and Molecules
• An enzyme’s structure allows only certain reactants to
bind to the enzyme.
– substrates
– active site
substrates
(reactants)
enzyme
Substrates bind to an
enzyme at certain places
called active sites.
2.5
Enzymes
2.1 Atoms,
Ions, and Molecules
• The lock-and-key model helps illustrate how enzymes
function.
– substrates brought together
– bonds in substrates weakened
Substrates bind to an
enzyme at certain
places called active
sites.
The enzyme brings
substrates together
and weakens their
bonds.
The catalyzed reaction forms
a product that is released
from the enzyme.