Transcript 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
Energy Levels
• Electrons move around the
nucleus in regions called energy
levels.
• Energy Levels: Where
electrons are found outside the
nucleus.
• Different energy levels can hold
different numbers of electrons.
2.1 Atoms, Ions, and Molecules
Energy Levels
• Outermost Energy Level:
– Atoms are most stable
when they have a full
outermost energy level.
– Determine how atoms
form ions or covalent
bonds.
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 a substance made up of atoms of
different elements bonded together in a certain ratio.
– water (H2O)
_
O
H
+
H
+
2.1 Atoms, Ions, and Molecules
• A compound is a substance made up of atoms of
different elements bonded together in a certain ratio.
– water (H2O)
– carbon dioxide (CO2)
2.1 Atoms, Ions, and Molecules
• A compound is a substance made up of atoms of
different elements bonded together in a certain ratio.
– 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.
• Ionic bonds form between oppositely charged ions due
to electrical attraction..
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
Positive and Negative ions
– positive ions: Formed when atoms lose electrons;
tend to be formed by atoms with few outer energy
levels.
– negative ions: Formed when atoms gain electrons;
tend to be formed by atoms with nearly a full outer
energy level.
2.1 Atoms, Ions, and Molecules
Atoms share pairs of electrons in covalent bonds.
• A covalent bond forms when atoms share one or more
pairs of electrons.
• A molecule is formed when atoms are bonded together
by covalent bonds; it is not necessarily a
compound..forms when atoms share one or more pairs of
electrons.
covalent bonds
Oxygen atom
(O)
Carbon atom
(C)
Carbon dioxide (CO2
)
Oxygen atom
(O)
2.1 Atoms, Ions, and Molecules
KEY CONCEPT
Water’s unique properties allow life to exist on
Earth.
2.1 Atoms, Ions, and Molecules
Life depends on hydrogen bonds in water.
• Water is a polar molecule.
– Polar molecules have slightly charged regions due to
an uneven pull on the electrons.
_
O
H
+
H
+
– Nonpolar molecules do not have charged regions
due to equal pull on the electrons.
– Hydrogen bonds form between slightly positive
hydrogen atoms and slightly negative atoms like
oxygen.
2.1 Atoms, Ions, and Molecules
Atom: Oxygen
_
+
H
O
H
Charge: Slightly Negative
+
_
+
H
O
Atom: Hydrogen
H
+
Charge: Slightly positive
2.1 Atoms, Ions, and Molecules
Check for understanding
• What does it mean for a molecule to
be polar?
2.1 Atoms, Ions, and Molecules
• Hydrogen bonds are responsible for three important
properties of water.
– high specific heat
– cohesion
– adhesion
2.1 Atoms, Ions, and Molecules
High Specific Heat
• Large amount of energy needed to produce an increase
in temperature.
2.1 Atoms, Ions, and Molecules
Cohesion
• Water molecules “stick” to each other.
2.1 Atoms, Ions, and Molecules
Adhesion
• Water molecules” stick” to other substances.
• Water has greater adhesion than cohesion.
2.1 Atoms, Ions, and Molecules
Person on the left of each table:
• Explain to your partner the difference
between cohesion and adhesion
2.1 Atoms, Ions, and Molecules
Many compounds dissolve in water.
• A solution is formed when one substance dissolves in
another.
– A solution is a homogeneous mixture (a mixtures of
substances that are the same throughout).
– Solvents dissolve other substances. They are present
in a greater amount.
– Solutes dissolve in a solvent. They are present in a
lesser amount.
solution
2.1 Atoms, Ions, and Molecules
Person on the right of each table:
• Explain the difference between a
solute and a solvent
2.1 Atoms, Ions, and Molecules
• “Like dissolves like.”
– Polar solvents dissolve polar solutes.
– Nonpolar solvents dissolve nonpolar solutes.
– Polar substances and nonpolar substances generally
remain separate.
2.1 Atoms, Ions, and 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
2.1 Atoms, Ions, and Molecules
• A base removes hydrogen ions from a solution.
– low H+ concentration
– pH greater than 7
bile pH between 8 and 9
more basic
2.1 Atoms, Ions, and Molecules
• A neutral solution has a pH of 7. It is neither acidic or
basic.
pure water pH 7
2.1 Atoms, Ions, and Molecules
KEY CONCEPT
Carbon-based molecules are the foundation of life.
2.1 Atoms, Ions, and 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
2.1 Atoms, Ions, and Molecules
• Many carbon-based molecules are made of many small
subunits bonded together.
– Monomers are small molecules that are the single
units in a much larger molecule.
– Polymers are large molecules (macromolecules)
formed from many monomers bonded together.
2.1 Atoms, Ions, and Molecules
Four main types of carbon-based molecules are found in
living things.
• Carbohydrates
– Made of carbon, hydrogen, and oxygen.
• Function
– Broken down to provide a source of energy.
– Make up plant cell walls.
• Monomer Example: Glucose
2.1 Atoms, Ions, and 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.
2.1 Atoms, Ions, and Molecules
• 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)
monomer
Cellulose is a polymer
of glucose monomers
that has a straight, rigid
structure
2.1 Atoms, Ions, and Molecules
• Lipids
– nonpolar molecules that include fats, oils, and
cholesterol.
– Many contain carbon chains called fatty acids.
– Fats and oils contain fatty acids bonded to glycerol.
Triglyceride
2.1 Atoms, Ions, and Molecules
• Lipids have several different functions.
– broken down as a source of energy
– make up cell membranes
– used to make hormones
2.1 Atoms, Ions, and Molecules
• Fats and oils have different types of fatty acids.
– saturated fatty acids
– unsaturated fatty acids
2.1 Atoms, Ions, and Molecules
• Phospholipids make up all cell membranes.
– Polar phosphate “head”
– Nonpolar fatty acid “tails”
Phospholipid
2.1 Atoms, Ions, and Molecules
• Proteins are polymers of amino acid monomers.
– Many functions: enzymes, oxygen transport, oxygen
transport, and muscle movement.
– Polymer: polypeptide (protein)
– Monomer: amino acids
– Twenty different amino acids are used to build proteins
in organisms.
2.1 Atoms, Ions, and 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.
2.1 Atoms, Ions, and 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.
2.1 Atoms, Ions, and 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.
2.1 Atoms, Ions, and Molecules
• Nucleic acids are polymers of monomers called
nucleotides.
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.
– Functions: Store genetic information; build
proteins.
A phosphate group
deoxyribose (sugar)
nitrogen-containing molecule,
called a base
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.
– Types: DNA and RNA
DNA
– DNA stores genetic
information.
RNA
– RNA builds proteins.
2.1 Atoms, Ions, and Molecules
Warm-up:
• Write at least 3 sentences describing how you think each
of these terms are related to one another:
– Chloroplast
– Chemical reactions
– Cellular respiration
– Photosynthesis
– Mitochondria.
2.1 Atoms, Ions, and Molecules
Talking Drawing:
• Create a graphic representation (drawing) of the following
words. If you do not know what they are use your best
judgment to draw a picture:
– Atom
– Chemical reaction
– Proton
– Neutron
– Electron
– Photosynthesis
2.1 Atoms, Ions, and Molecules
KEY CONCEPT
Life depends on 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.
– 1. Reactants: Substances changed by a chemical
reaction.
– 2. Direction of the reaction
– 3. Products: Substances formed during a chemical
reaction.
CO2 + H2O
H2CO3
2.1 Atoms, Ions, and Molecules
• Bond energy: is the amount of energy that breaks a
bond, or the amount of energy released when a bond
forms.
– Energy is added to break bonds.
– Energy is released when bonds form.
• Chemical Equilibrium: Reversible reactions can occur in
both directions. A reaction is at equilibrium when reactants
and products form at the same rate.
CO2 + H2O
H2CO3
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.
• 4. Reactants
• 5. Activation Energy
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.
6. Total Energy
Released
7. Products
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.
8. Reactants
9. Activation Energy
10. Total Energy
Released
11. Products
2.1 Atoms, Ions, and Molecules
KEY CONCEPT
Enzymes are catalysts for chemical reactions in
living things.
2.1 Atoms, Ions, and Molecules
A catalyst lowers activation energy.
• A Catalyst: is a substance that speeds up chemical
reactions.
1. decreases activation energy
2. increases reaction rate
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.
2.1 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.
2.1 Atoms, Ions, and Molecules
• Enzyme structure and function: An enzyme’s structure
allows only certain reactants to bind to the enzyme.
– Substrates – Reactants that bind to the active site of
an enzyme.
substrates
(reactants)
enzyme
Substrates bind to an
enzyme at certain
places called active
sites.
2.1 Atoms, Ions, and Molecules
• The lock-and-key model helps illustrate how enzymes
function.
– substrates brought together
– The enzyme only works when specific substrates bind.
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.