Transcript Document

Chapter 6:
Chemistry in Biology
Section 1:
Atoms, Elements, and Compounds
MAINIDEA
Matter is composed of tiny particles called atoms.
RECALL
substance- form of matter that has a uniform and unchanging
composition
Compare the terms in the table by defining them:
Atom:
building block of matter
Nucleus:
central region of an atom that contains
protons and neutrons
Proton:
positively charged
particles located
in the nucleus
Neutron:
particles with no
charge located in
the nucleus
Electron:
Negatively charged
particles that
are located in a
cloud outside
the nucleus
Complete the paragraph below using the following terms: isotope,
molecule, ion, ionic bond, covalent bond, compound, element, van der
Waals force
A substance that cannot be broken down into other substances
element
isotope
is a(n) ____________________.
Carbon-14 is a(n) _____________
.
It has a different number of neutrons than other carbon atoms. A(n)
compound
______________________
forms when two or more elements combine.
The chemical bond that holds the elements together is a(n)
covalent bond
________________________
when electrons are shared. A substance
molecule
with this kind of bond is called a(n) _____________________________
.
An atom that has lost or gained one or more electrons becomes a(n)
ion
_________________________,
which carries an electric charge. Two of
these oppositely charged atoms can form an electrical attraction
ionic bond
called a(n) ________________________.
An attraction between
oppositely charged regions of molecules is called
van der Waals force
a(n) __________________________.
Atoms
The structure of an atom:
•Atoms are the building blocks of matter.
•Atoms are made up of smaller particles called neutrons, protons,
and electrons
•Protons are positively charged particles (p+).
•Neutrons are particles that have no charge (n0).
•Electrons are negatively charged particles (e-)
The structure of an atom:
•Protons and neutrons are located in the center of the atom,
called the nucleus.
•Electrons are located outside the nucleus.
Model an oxygen atom and label the parts in the box below. Note the
type of electric charge for each part. Then complete the sentence that
follows:
8 electrons (-)
8 protons (+)
8 neutrons (0)
zero
The overall charge of the oxygen atom is______________
because the
has an equal number of protons (+) and electrons (-)
atom________________________________________________.
Elements
•An element is a pure substance that cannot be broken down
into other substances by physical or chemical means.
•There are over 100 known elements, 92 of which occur
naturally.
•Each element has a unique name and symbol.
The periodic table of elements:
•Horizontal rows are called periods, vertical columns are called groups
Isotopes:
•Atoms of the same element that have the same number of
protons and electrons but have a different number of neutrons are
called isotopes.
Radioactive isotopes:
•Changing the number of neutrons in an atom does not affect the
charge, but does affect the stability.
•When a nucleus breaks apart, it gives off radiation that can be
detected and used for many applications.
•Isotopes that give off radiation are called radioactive isotopes.
Compare and contrast the characteristics of carbon-14 by completing
the following sentences:
Structurally, carbon-14 differs from other carbon atoms because
it
has a different number of neutrons
_________________________________.
its nucleus decays and breaks apart
Carbon-14 is radioactive because _______________________________.
calculate the
Knowing the half-life of carbon-14 enables scientists to _____________
age
of an object
_______________.
Compounds:
•A compound is pure substance formed when two or more different
elements combine.
•Compounds are always formed from a specific combination of
elements in a fixed ratio.
•Compounds cannot be broken down into simpler compounds or
elements by physical means, but can be broken down by chemical
means.
Identify four unique characteristics of compounds:
Formed from
specific combination
of elements in a
fixed ratio
Cannot be broken
down by physical
means
Compounds
Chemically and
physically different
than the elements
they are made of
Can be broken down
by chemical means
Chemical Bonds:
•The force that holds
substances together is called a
chemical bond.
•The electrons of an atom are
responsible for forming
chemical bonds.
•Electrons travel around the
nucleus of an atom in areas
called energy levels.
•Atoms become more stable by
losing electrons or attracting
electrons from other atoms.
Covalent bonds:
•The chemical bond that forms when electrons are shared is
called a covalent bond.
•A molecule is a compound in which the atoms are held together
by covalent bonds.
Label the following parts of the water molecule illustrated below:
•Hydrogen atoms
•First energy level
•Oxygen atom
•Second energy level
•Covalent bonds
Hydrogen
atoms
Covalent
bonds
First energy
level
Oxygen
atom
Second
energy level
Ionic Bonds:
•An atom that has lost or gained one or more electrons is an ion.
•Ions carry an electric charge.
•An ionic bond is an electrical attraction between two oppositely
charged atoms.
Compare positively and negatively charged ions:
gives away one or more electron
Atom
becomes
accepts one or more electron
Ionic Bonds:
•Some atoms tend to donate or accept electrons more easily than
other atoms.
•The elements identified as metals tend to donate electrons.
•The elements identified as nonmetals tend to accept
electrons.
•Most ionic compounds dissolve in water, are crystalline at room
temperature, and have higher melting points than compounds
formed by covalent bonds.
van der Waals Forces
•Attractions between molecules are called 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.
van der Waals forces in water:
•The slightly positive and slightly negative charges around the
water molecule are attracted to the opposite charge of other
nearby water molecules.
•van der Waals forces are responsible for water droplet
formation and surface tension.
Identify the positive and negative regions of these two molecules to
show the van der Waals forces:
+
-
van der Waals
+
-
Section 2:
Chemical Reactions
MAINIDEA
Chemical reactions allow living things to grow, develop,
reproduce and adapt.
RECALL
process-series of steps or actions that produces an end
product
Write the term next to the correct definition:
chemical
reaction
Process by which atoms or groups of atoms in substances are
reorganized into different subtances
reactant
Starting substance in a chemical reaction
product
activation
energy
catalyst
enzyme
substrate
active site
Substance formed during a chemical reaction
Minimum amount of energy needed for reactants to form products
in a chemical reaction
Substance that lowers the activation energy needed to start a
chemical reaction
Protein that speeds up a chemical reaction in a biological process
Reactant that binds to an enzyme
Location where a substrate binds on an enzyme
coefficient- number in front of a reactant or a product in a
chemical equation
Reactants and Products
•A chemical reaction is the process by which atoms or groups of
atoms in substances are reorganized into different substances.
•Chemical bonds are broken or formed during a chemical reaction.
•Clues that a chemical reaction has taken place:
-production of heat or light
-formation of a new gas, liquid, or solid
•Substances can also undergo physical changes, which change the
appearance but not the composition.
Chemical Equations
•In written chemical equations, chemical formulas describe
the substances in the reaction and arrows indicate the
process of change.
•The arrow can be read as “yields” or “react to form.”
Label the sides of the following equation as either products or
reactants:
reactants
products
CH4 + 2O2
CO2 + 2H2 O
Calculate the number of each atom from the chemical equation on
the previous page. Record the information in the table below:
Element
symbol
Element name Number of atoms
(reactant side)
Number of atoms
(product side)
C
Carbon
1
1
H
Hydrogen
4
4
O
Oxygen
4
4
Balanced equations
•In chemical reactions, matter cannot be created or
destroyed.
•All chemical equations must show this balance of mass.
•The number of atoms of each elements on the reactant side
must equal the number of atoms of the same element on the
product side.
Analyze the formula to check to see if it is balanced. Support
your reasons:
Each atom has the same number of atoms on both sides
of the equation, no mass has been lost or gained.
Explain why must chemical equations must be balanced:
Matter can neither be created nor destroyed
Energy of Reactions
Activation energy:
•The minimum amount of energy needed for reactants to form
products is called activation energy.
•Some reactions happen rarely due to the high activation energy
required.
Energy change in
chemical reactions:
•Reactions that
release energy in the
form of heat are
exothermic.
•Reactions that absorb
energy in the form of
heat are endothermic.
Compare what happens to energy in exothermic and
endothermic reactions by completing the diagram below:
exothermic
endothermic
During the reaction
energy is:
During the reaction
energy is:
released
absorbed
As a result the
energy of the
product is lower
than the energy in
the reactants
As a result the
energy of the
products is higher
than the energy of
the reactants
Enzymes
•All living things are driven by chemical reactions.
•Additional substances are needed to reduce activation energy
and reaction time in living organisms.
•A catalyst is a substance that lowers the activation energy
needed to start a chemical reaction.
•Catalysts do not change the amount of product produced, nor
are they used up during the reaction.
•Special proteins called enzymes are the biological catalysts that
speed up the rate of chemical reactions in biological processes.
•Most enzymes are specific to one reaction.
•The reactants that bind to an enzyme are called substrates.
•The specific location where a substrate binds on an enzyme is
called the active site.
•Factors such as pH, temperature, and other substances affect
enzyme activity.
Draw the reaction that will occur using the following substrate,
products, and enzyme. Be sure to label the active site:
Section 3:
Water and Solutions
MAINIDEA
The properties of water make it well suitable to help
maintain homeostasis in organisms
RECALL
Physical property- characteristic of matter that can be observed
without changing the composition of the substance
Write the correct term next to the definition:
base
Substance that releases hydroxide ions when dissolved in
water
acid
Substance that releases hydrogen ions when dissolved in
water
solvent
buffer
pH
solute
Substance in which another substance is dissolved
Mixture that can react with an acid or a base to keep the pH
within a particular range
Measure of concentration of hydrogen ions in a solution
Substance that is dissolved in a solvent
hydrogen bond
Weak interaction involving a hydrogen atom and fluorine,
oxygen, or nitrogen atom
polar molecule
Molecule that had oppositely charged regions
solution
mixture
Mixture that has a uniform composition throughout
Combination of two or more substances in which each
substance retains its individual characteristics and properties
suspend: to keep from falling or sinking
Water’s Polarity
• Water molecules are formed by covalent bonds that link two
hydrogen (H) atoms to one oxygen (O) atom.
• Water molecules have a slightly positive end near the H atoms
and a slightly negative end near the O atom.
• Molecules that have an uneven distribution of charge are called
polar molecules, meaning they have oppositely charged
regions.
Analyze polarity by writing attract or repel in the middle for each
diagram:
attract
+
-
+
-
-
+
+
-
repel
+
repel
-
+
• When a charged region of a polar molecule comes close to
the oppositely charged region of another polar molecule, a
weak attraction forms.
• A hydrogen bond is a weak interaction involving a hydrogen
atom and a fluorine, oxygen, or nitrogen atom.
• A hydrogen bond is a strong type of van der Waals force.
Mixtures with Water
• A mixture is a combination of two or more substances in which
each substance retains its individual characteristics and
properties.
• Mixtures are either homogeneous or heterogeneous.
Homogeneous mixtures:
• When a mixture has a uniform composition throughout, it is
called homogenous.
• A solution is another name for a homogeneous mixture.
• In a solution, there are two components:
• A solvent is a substance in which another substance is
dissolved.
• A solute is the substance that is dissolved in the solvent.
Heterogeneous mixtures:
• When the components in a mixture remain distinct, it is a
heterogeneous mixture.
• A suspension is a type of heterogeneous mixture where the
particles settle out over time
• A colloid is a heterogeneous mixture in which the particles do
not settle out
Identify each of the following mixtures as either homogeneous or
heterogeneous:
Sand
and
sugar
Salt and
water
Blood
heterogeneous
homogeneous
heterogeneous
For the homogeneous mixture above, identify the solvent and the
solute:
water
salt
solvent:______________
solute:________________
Acids and bases:
• Many solutes readily dissolve in water because of water’s
polarity.
• Substances that release H+ when they are dissolved in water
are called acids.
• Substances that release hydroxide ions (OH-) when they are
dissolved in water are called bases.
pH and buffers:
• The amount of hydrogen or hydroxide ions in a solution
determines the strength of an acid or base.
• The measure of concentration of H+ in a solution is called pH.
• Acids have pH values < 7; bases have pH values > 7
• Buffers are mixtures that can react with acids or bases to keep
the pH within a particular range
Fill in the rest of the scale by placing the following items in the
correct sequence:
•Releases some hydrogen ions
•Releases some hydroxide ions
•Releases many hydrogen ions
•Releases many hydroxide ions
•Water
Releases many
hydrogen ions
Acidic
solutions
strong
Releases some
hydroxide ions
weak
Releases some
hydrogen ions
water
weak
strong
Basic
solutions
Releases many
hydroxide ions
Section 4:
The Building Blocks of Life
MAINIDEA
Organisms are made up of carbon-based molecules.
RECALL
Organic compound- carbon-based substance that is the basis of
living matter
Write the correct term for each definition:
macromolecule
polymer
carbohydrate
lipid
protein
Large molecule that is formed by joining smaller organic molecules
Molecule made from repeating units of identical or nearly identical
compounds called monomers that are linked together by a series
of covalent bonds
Compound composed of carbon, hydrogen, and oxygen in a ratio
of one oxygen and two hydrogen atoms for each carbon atom
Molecule made mostly of carbon and hydrogen that makes up fats,
oils, and waxes
Compound made of small carbon compounds called amino acids
amino acid
Component of protein that is a compound made carbon, nitrogen,
oxygen, hydrogen, and sometimes sulfur
nucleic acid
Complex macromolecule that stores and transmits genetic
information
nucleotide
Repeating subunit of a nucleic acid
Organic Chemistry
•Organic chemistry is the study of organic compounds –
compounds that contain carbon.
•Carbon is a component of almost all biological molecules.
•Carbon atoms bond together to form a variety of important
organic compounds.
Macromolecules
•Macromolecules are large molecules that are formed by joining
smaller organic molecules together.
•Polymers are molecules made from repeating units of identical or
nearly identical compounds called monomers.
•Macromolecules are organized into four major categories:
-Carbohydrates
-Lipids
-Proteins
-Nucleic acids
Carbohydrates:
•Compounds composed of a ratio of 1 carbon : 2 hydrogen : 1 oxygen
are called carbohydrates.
•Carbohydrates have a general formula of (CH2O)n where n indicates
the number of CH2O units in the chain.
•Carbohydrates are a central energy source in organisms, as well as
functioning as cellular support in plants, fungi, and animals.
Evaluate the number of molecules of each element in the
carbohydrate described by the formula below:
(CH2O)6
6
Carbon:_________
12
Hydrogen:_______
6
Oxygen:_________
1:2:1
Ratio of carbon, hydrogen, oxygen:________________
Monosaccharide/ simple sugar
Type of carbohydrate:___________________________________
Lipids
•Lipids are molecules made mostly of carbon and hydrogen that
make up the fats, oils, and waxes.
•A lipid’s primary function is to store energy, but they are also
used to prevent water loss in plants and form the honeycomb in
beehives.
Proteins
•Proteins are compounds made of smaller carbon compounds
called amino acids.
•All amino acids are made of carbon, nitrogen, oxygen, hydrogen,
and sometimes sulfur and share the same general structure.
•There are 20 different amino acids, and proteins are
composed of various combinations
•Proteins are responsible for structural support in cells,
transporting substances within and between cells, signaling
within and between cells, speeding up chemical reactions,
and controlling cell growth.
Nucleic acids
•Nucleic acids are complex macromolecules that transmit and
store genetic information.
•Nucleic acids are composed of smaller repeating subunits
composed of carbon, nitrogen, oxygen, phosphorus, and
hydrogen called nucleotides.
•There are two types of nucleic acids in living organisms:
-Deoxyribonucleic acid (DNA): stores all
the instructions
for organisms
-Ribonucleic acid (RNA): uses the information from DNA
to make proteins
Describe nucleic acids by filling in the following chart:
Units that Make Up Nucleotides
phosphate
Function of DNA:
Stores all instructions
for organisms
nitrogenous
base
ribose sugar
Function of RNA:
Uses the information
from DNA to make
proteins