biology basis of life
TRANSCRIPT
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The Basis of Life
Dr Mirna N. Chahine
Week 2
Feb 18th -22nd
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1. Matter, Energy, and Life
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All living things can use MATTER and ENERGY
to their advantage.
MATTER= anything that has a mass and takes
up space.
ENERGY= The ability to do work or causethings to move
Matter & Energy
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Work is being done
whenever some
physical force is
being used to move
an object some
distance
Energy
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Energy means that birds can fly,
tigers can roar,
wind can blow,
sun can shine,
cars can go fast, factories can make things,
light bulbs can glow and
your computer can work.
Without energy, there would be nothing: nolife, no movement, no light, nothing
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Energy All objects contain energy in one form or
another
Can take the form of:
Motion Position
Heat
Light
Sound
Electricity
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Kinetic Energy
-Potential Energy
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The amount of energy contained in anobject at rest;
The energy of position;
Stored energy (ex: in chemicals)
Ex: Stretched bow
Ex: Skiing (maintainingitself at top of the
slope)
Potential Energy
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Potential Energy
o Potential energystored within thechemical bonds of an object
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o Potential energystored within thechemical bonds of an object
Potential Energy
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Kinetic
Energy
vs
PotentialEnergy
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Kinetic
Energy
vs
PotentialEnergy
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Kinetic
Energy
vs
PotentialEnergy
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Kinetic
Energy
vs
PotentialEnergy
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Moving car
Tree branch Balloon filled with air
Balloon squirting around room
Potential or Kinetic Energy?
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Potential or Kinetic Energy?
Moving car: Kinetic Energy
Tree branch: Potential Energy
Balloon filled with air: Potential Energy
Balloon squirting around room : Kinetic Energy
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In conclusion : Energy
Energy can _______________
Energy can _______________
But ENERGY can_______________
from one form to another
never be created
never be destroyed
only be converted
LAW OF CONSERVATION
OF ENERGY
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2. The Nature of Matter
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Introduction: Matter / Chemistry
In Science, living things are not
composed of pure energy
In Science, living things are alsocomposed of matter
CHEMISTRY: Basic principles of MATTER Composition,
Structure,
Properties of matter
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Matter
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2. The Nature of Matter2.2. The Structure of an Atom
Neutrons
Protons
Electrons
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Elements
Pure substancesthat cannot be broken down
chemically into simpler kinds of matter
More than 100 elements (92 naturallyoccurring)
Elements
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90% of the mass of an organism is
composed of 4 elements (oxygen,
carbon, hydrogen and nitrogen) Each element unique chemical
symbol:
Consists of 1-2 letters
Firstletter is always capitalized
Elements
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ATOMS are the simplest particle ofan elementthat retains all theproperties of that element
Properties of atomsdetermine thestructure and properties of thematter they compose
Atoms
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AtomsThe study of chemistry begins with
the basic unit of matter, the atom.
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Placed side by side, 100
million atoms would
make a row only about 1centimeter long.
Atoms contain
subatomic particles
that are even smaller.
Atoms
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The subatomic
particles that makeup atoms are:
protons
neutrons
electrons
Atoms
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The Nucleus
Centralcore
Consists of positive
charged protons and
neutral neutrons
Positively charged
Contains most of the
mass of the atom
The subatomic particles
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The subatomic particles
in a helium atom.
XA: MASS NUMBER
Z: ATOMIC NUMBER
=PROTONS NUMBER
N= A-Z=NEUTRONS NUMBER
PROTONS NB= ELECTRONS NB
He4
2
=2
=2
=2
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2. The Nature of Matter2.1. The Structure of an Atom2.2. Elements may vary in Neutrons but not in
Protons
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Elements and Isotopes
A chemical element is a pure substance that consists
entirely of one type of atom.
Isotopes are atoms of the same element that differ in
the number of neutrons they contain.
N= 12-6= 6 N= 14-6= 8
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Because they have
the same number of
electrons, all isotopesof an element have
the same chemical
properties.
The differenceamong the isotopes
is the number of
neutrons in their
nuclei.
Elements and Isotopes
6 electrons
6 protons
8 neutrons
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2. The Nature of Matter2.1. The Structure of an Atom2.2. Elements may vary in Neutrons but not in
Protons
2.3. The positions of Electrons
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The Electrons
Negatively chargedhigh energy particles with little
or no mass
Travel at very high speedsat various distances
(energy levels)from the nucleus
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Electrons in the same energy level areapproximately the same distance from the
nucleus
Outer energy levels have more energythan inner levels
Each levelholds only a certain number ofelectrons
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Energy Levels
Atoms have 7energy levels
The levels are K (closest to the nucleus), L, M, N,O, P, Q(furthest from the nucleus)
The K level can only hold 2electrons Levels LQ can hold 8electrons (OCTET RULE)
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Periodic Table Elements are arranged by their atomic
number on the Periodic Table
The horizontal rows are called Periods & tell
the number of energy levels Vertical groups are called Families & tell the
outermost number of electrons
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2. The Nature of Matter2.1. The Structure of an Atom2.2. Elements may vary in Neutrons but not in
Protons
2.3. The positions of Electrons2.4. The formation of Molecules/Compounds
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Molecules/ Compounds
CO2 H2OO3
Moleculesare the simplest part of a substance thatretains all of the properties of the substance and
exists in a free state; They are composed by 2 or
more atoms of the same element ex: H2, O2, O3
Compounds are molecules composed by more than
one element ex: CO2, H20, CH4
The Formation of
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The Formation of
Molecules and Compounds
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Chemical Compounds
A chemical compoundis a substance formed bythe chemical combination of two or moreelements in definite proportions.
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Copyright Pearson Prentice Hall
Chemical Formula
Water
Table Salt
Hydrochloric Acid
Glucose
Molecules/ Compounds
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Copyright Pearson Prentice Hall
Chemical Formula
Water: H2O
Table Salt: NaCl
Hydrochloric Acid: HCl
Glucose: C6H12O6
Molecules/ Compounds
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2. The Nature of Matter2.1. The Structure of an Atom2.2. Elements may vary in Neutrons but not in
Protons2.3. The positions of Electrons
2.4. The formation of Molecules/Compounds
2.5. State of a compound: Physical and ChemicalChanges
f f
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States of Matter ofthe compound
Atoms are in constant motion
The rate at which atoms or molecules in asubstance move determines its state
f f
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Solid Molecules tightly linked together in a definite shape
Vibrate in place
Fixed volume and shape
Liquids
Molecules not as tightly linkedas a solid
Maintain fixed volume
Able to flow and conform to shapeof container
Gas
Molecules have little or no attraction to each other
Fill the volumeof the occupied container
Move most rapidly
States of Matter ofthe compound
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The tendency of elements to combine andform compounds depends on the number andarrangement of electrons in their outermostenergy level
Atoms are most stable when their outer most
energy level is filled Most atoms are not stable in their natural
state Tend to react(combine) with other atoms in
order to become more stable (undergo
chemical reactions) In chemical reactionsbonds are broken;
atoms rearranged and new chemical bondsare formed that store energy
Stability of atoms
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The atoms in
compounds are held
together by chemicalbonds.
The electrons that
are available to formbonds are called
valence electrons.
Chemical Bonds
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Chemical Bonds
The main types of chemical bonds are:
ionic bonds
covalent bonds
Ionic Bond
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An ionic bondis formed when one or more electronsare transferred from one atom to another.
These positively and negatively charged atoms areknown asions.
Because positive and negative electrical chargesattracteach other ionic bonds form
Ionic Bond
Ionic Bond
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Chemical Bonds
Protons +17
Electrons - 18
Charge -1
Protons +11
Electrons - 11
Charge 0
Protons +11
Electrons - 10
Charge +1
Protons +17
Electrons - 17
Charge 0
Sodium ion (Cl-)Sodium atom (Na)
Sodium atom (Cl)Sodium ion (Na+)
Ionic Bond
Ionic Bond
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Ionic Bond
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Copyright Pearson Prentice Hall
They are formed when electrons are shared
between atoms instead of being transferred.
Covalent Bonds
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single covalent
bond:
1 pair of e- is shared
double bond2 pairs of e- are shared
triple bond3 pairs of e- are shared
Covalent Bonds
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2. The Nature of Matter2.1. The Structure of an Atom
2.2. Elements may vary in Neutrons but not in
Protons
2.3. The positions of Electrons2.4. The formation of Molecules/Compounds
2.5. State of a compound: Physical and Chemical
Changes2.6. Water the Essence of Life
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The Water Molecule
A water molecule is polar because there is an unevendistribution of electrons between the oxygen and
hydrogen atoms.
The hydrogen end
of the molecule is
slightly positive
The oxygen end isslightly negative.
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Hydrogen BondsBecause of their partial positive and negativecharges, polar molecules can attract each
other.
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Solutions and Suspensions
Amixtureis a material composed of two or more
elements or compounds that are physically
mixed but not chemically combined.
Two types of mixtures can be made with water
solutions
suspensions
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SolutionsAll the components of a solution are evenly distributed
throughout the solution.
-solute: the substance that is dissolved: ex: NaCl-solvent: the substance in which the solute dissolves: ex: H2O;
Water is the universal solvent
Solutions and Suspensions
Suspensions
Some materials do not dissolve when placed
in water but separate into pieces so small
that they do not settle out easily.
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2. The Nature of Matter2.1. The Structure of an Atom
2.2. Elements may vary in Neutrons but not in
Protons
2.3. The positions of Electrons
2.4. The formation of Molecules/Compounds2.5. State of a compound: Physical and Chemical
Changes
2.6. Water the Essence of Life2.7. Acids, Bases, pH, and Buffers
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Acids, Bases, and pH
A water molecule is neutral, but can react to form
hydrogen and hydroxide ions.
H2O H+ + OH-
A id B d H
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Acids, Bases, and pH
The pH scale : Chemists devised a measurement system calledthe pH scale to indicate the concentration of H+ions in solution:
The pH scale ranges from 0 to 14.
Acid: is any compound that forms H+ions in solution; ex: HCl
Base: is a compound that produces OH-ions in solution; ex: NaOH
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the lowerthe pH the stronger the acid
the higherthe pH the stronger the base pH 7.0 is neutral
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h f
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2. The Nature of Matter2.1. The Structure of an Atom
2.2. Elements may vary in Neutrons but not in
Protons
2.3. The positions of Electrons
2.4. The formation of Molecules/Compounds2.5. State of a compound: Physical and Chemical
Changes
2.6. Water the Essence of Life2.7. Acids, Bases, and pH
2.8. Chemical reactions
FIVE t i t t
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FIVE most important
Chemical Reactions
1- Oxidation- Reduction Reactions
2- Acidbase reactions 3- Dehydration synthesis reactions
4- Hydrolysis reactions
5- Phosphorylation reactions
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Reduction-Oxidation Reactions
Many of the chemical reactions that help transfer
energy in living organisms involve the transfer of
electrons (reduction-oxidation = redox reactions)
1- Oxidation reactionreactant
loses electron(s) becoming more
positive
2- Reduction reactionreactant
gains electron(s) becoming more
negative
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Acid-Base Reactions
They take place when the ions of an acid interact
with the ions of a base;
This occurs in organisms and their environment inorder to protect them from damage
H Cl + Na OH Na Cl + HOH+ + +- - -
Hydrochloric
acid
Sodium
Hydroxide
Sodium
Chloride
Water :
H2O
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