chapter 2 botany 1a
TRANSCRIPT
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The ChemicalComposition of Cells
Chapter 2
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LEARNING OBJECTIVE 1
Describe the basic structure of an atom,and explain ionic, covalent, and hydrogen
bonds
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Atoms
Atom smallest possible particle of anelement that still possesses and elements
property
Subatomic particles: Proton- positive electric charge, small mass Neutron- uncharged, about same mass as proton Electron- negative charge, extremely small mass
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Neutron
Electron
Proton
+
+++
++
+
Fig. 2-1, p. 24
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Isotopes of Hydrogen
Isotopes similar elements that contain different numbers of neutrons
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Electrons
Move around the nucleus at differentenergy levels
Allow elements to combine chemically toform chemical compounds
Ions are atoms which tend to gain or loseelectrons
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Electron Configurations
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(b) Carbon (C)(6p, 6n)
Electron
Nucleus
First (lowest)
energy level
Second energylevel
(a) Hydrogen (H)(1p)
Fig. 2-3ab, p. 25
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(d) Nitrogen (N)
(7p, 7n)
(c) Oxygen (O)
(8p, 8n)
Fig. 2-3cd, p. 25
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(e) Sodium (Na)
(11p, 12n)
(f) Chlorine (Cl)
(17p, 18n)
Fig. 2-3ef, p. 25
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Atoms are capable of forming
bonds Chemical bond attractive force that holds 2 or more
atoms together
Chemical bonds form compounds
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KEY TERMS
IONIC BOND An electrostatic attraction between oppositely
charged ions
COVALENT BOND A chemical bond involving one or more
shared pairs of electrons
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Ionic Bonding
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11 protons 17 protons
and
11 electronsSodium (Na)
17 electronsChlorine (Cl)
10 electrons
Sodium ion (Na+)
18 electrons
Chloride ion (Cl)
+
Fig. 2-4a, p. 26
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Arrangement of atoms in acrystal of salt
Sodium chloride (NaCl)
Cl Na+
Cl
Cl
Na+Na+
Na+
Fig. 2-4b, p. 26
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Covalent Bonding in Hydrogen
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Hydrogen (H) Hydrogen (H) Molecular hydrogen (H2)
Fig. 2-5, p. 27
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Covalent Bonding in Methane
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Types of Covalent Bonds
Nonpolar covalent bonds electrons are equally
shared
Polar covalent bonds electrons are unequally
shared
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KEY TERMS
HYDROGEN BOND An attraction between a slightly positive hydrogen
atom in one molecule and a slightly negative atom
(usually oxygen) in another molecule
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LEARNING OBJECTIVE 2
Discuss the properties of water, andexplain the importance of water to life
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Why is water important?
Essential to life Controls our climate Shapes continents
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Water is a polar substance
Polar substance substances with partial charges
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Water
Has a strong dissolving ability Molecules form hydrogen bonds with one another
(cohesion)
Molecules form hydrogen bonds to substances withionic or polar regions (adhesion)
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LEARNING OBJECTIVE 3
Distinguish between acidsand bases, anddescribe the pH scale
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Acids and Bases
Definition Acidsdissociate in water to form hydrogen
ions (protons, H+)
Basesdissociate in water to yield negatively
charged hydroxide ions (OH-)
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pH Scale
A measure of the relative concentrationsof H+and OH-in a solution
A solutions acidity or alkalinity isexpressed in terms of the pH scale
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ACID RAIN!!
Accumulation of sulfur oxides andnitrogen oxides in the atmosphere
Suflur oxide &nitrogen oxide combinewith water to form SULFURIC andNITRIC ACID
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LEARNING OBJECTIVE 4
Describe the chemical compositions andfunctions of carbohydrates, lipids, proteins,and nucleic acids
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Carbohydrates Include sugars, starches, cellulose
Important fuel molecules, components of molecules(nucleic acids) and cell walls
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Carbohydrates
Types of carbohydrates1. Monosaccharides - simple sugars
2. Disaccharides-two monosaccharide units
3. Polysaccharides- many monosaccharide
units
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Common Monosaccharides
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Sucrose Synthesis
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Starch: A Storage Polysaccharide
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Cellulose: A Structural
Polysaccharide
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Lipids
Organic compounds that have a greasy consistency, donot readily dissolve in water
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Lipids
Types of Lipids:1. Neutral fats2. Oils3. Phospholipids
4.
Pigments and Waxes
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Lipids
Neutral fats / oils1. Neutral fats solid at room temperature2. Oil- liquid at room temperature
Contain a molecule of glyceroljoined to one, two orthree fatty acids
Glycerol 3 carbon compound that contains ahydroxyl group
Usually used as a source of energy
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Formation of a Neutral Fat or Oil
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Lipids
Fatty acids Long, unbranched
hydrocarbon chainwith a carboxyl group
at one end Types:
Saturated contain nocarbon to carbon
double bonds
Unsaturated contain1 or more carbon to
carbon double bonds
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Saturated Unsaturated
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Lipids
Phospholipids Important component of the cell membrane Consists of a glycerol molecule and 2 fatty acids
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Lipids
Waxes Cutin waxy substance found in the outer wall of
epidermal cells
Suberin substance found in the walls of cork cells
Prevent water loss
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Protein
A macromolecule composed of amino acidsjoined bypeptide bonds
Order of amino acids determines structure and functionof a protein molecule
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Proteins
Enzymes A protein which controls the rate at which a chemical
reaction occurs
Highly specific E.g. Sucrase
Substrate the material in which theenzyme works on
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Amino Acids
Basic unit of proteins Contain a carbon atom bonded to an amino acid
(-NH2), a carboxyl group (-COOH2) and a side
chain, designated R
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Peptide Bonds
Bonds that links one amino acid to another as aresult of a condensation reaction
Several amino acids connected to each othercan form a polypeptide chain
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Organization of Protein Molecules
Organization of Protein
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Organization of Protein
Molecules
Primary linear sequence of amino acids Secondary spiral helix
Tertiary over-all shape of a polypeptide chaindetermined by interactions of side chains of aa
Quaternary 2 or more polypeptide chainsassociate to form one final protein molecule
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(d) Quaternary(a) Primary (b) Secondary (c) Tertiary
Fig. 2-15, p. 37
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Nucleic Acids
Macromolecules that are made out of carbon,hydrogen, nitrogen and phosphorous
Control the cell
s life processes
Deoxyribonucleic acid (DNA) Transmits information from one generation to the next
Ribonucleic acid (RNA) Involved in protein synthesis
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Nucleotides
Repeating units that form nucleic acids Order of nucleotides in a nucleic acid chain determines
the specific information encoded
Parts of a nucleotide1. Nitrogenous base2. 5-carbon sugar
3. Phosphoric acid
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Nucleic Acids
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Nucleic Acids
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Phosphate
Adenine(a nitrogenous
base)
Deoxyribose(a five-carbon sugar)
(a) Nucleic acids are composed of nucleotides. Like allnucleotides, this DNA nucleotide has three parts: a nitrogenous
base, a five-carbon sugar, and a phosphate group.
H H
Fig. 2-18a, p. 39
Two sugar-phosphatebackbones
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backbones
Pairedbases
Region of
hydrogen bonding
(c) The DNA molecule is a double helix
consisting of two nucleotide chainsjoined by their paired bases.
(d) A small part of a DNA molecule isunwound to show how the bases pair
(the region of hydrogen bonding).Fig. 2-18cd, p. 39
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ATP Adenosine triphosphate Modified nucleotide Composition:
Base adenine Sugar ribose 3 phosphate molecules
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Enzymes
Speed up a chemical reaction by loweringits activation energy(energy needed to
initiate the reaction)
Most enzymes are highly specific andcatalyze only a single chemical reaction
Without enzymes, chemical reactions incells would occur too slowly to support life
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Enzymes and Activation Energy
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Enzyme-Substrate Complex
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Active sites
Enzyme Substrates Enzymesubstratecomplex
Enzyme Products
Fig. 2-17, p. 38Stepped Art
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LEARNING OBJECTIVE 6
State the firstand second laws ofthermodynamics, and describe how eachapplies to plants and other organisms
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KEY TERMS
FIRST LAW OF THERMODYNAMICS Energy cannot be created or destroyed,
although it can be transformed from one form
to another
SECOND LAW OF THERMODYNAMICS When energy is converted from one form to
another, some of it is degraded into a lower-
quality, less useful form
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Energy
The ability to do work
Plants and other organisms cannot createthe energy they require to live, but must
capture energy from the environment and
use it to do biological work
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E
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Entropy
Measure of the disorder of less usable energy Continuously increases in the universe as
usable energy is converted to lower-quality, lessusable form (heat)
As each energy transformation occurs inorganisms, some energy changes to heat
Given off into the surroundings Can never be used again for biological work
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A i i H A B d
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Animation: How Atoms Bond
CLICKTO PLAY
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Animation: Miller s Reaction
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Animation: Millers Reaction
Chamber Experiment
CLICKTO PLAY
Animation: Structure of Starch
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Animation: Structure of Starch
and Cellulose
CLICKTO PLAY
Animation: Triglyceride
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Animation: Triglyceride
Formation
CLICKTO PLAY
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