Transcript Bio1A Unit 1-1 Chem Notes File

Biology Themes
Evolution
• Origin - Organisms living on Earth are modified descendents of common ancestors
• Gradual Change
• Selection
Organisms interact with their environments, exchanging matter and energy
Energy Conversion
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Work requires a source of energy
Energy can be stored in different forms, for example, light, chemical, kinetic, or thermal
energy exchange between an organism and its environment often involves energy transformations
Energy flows through an ecosystem, usually entering as light and exiting as heat
Structure and function are correlated at all levels of biological organization
Proteins’ ability to change shape is central to biological function
Cells are an organism’s basic units of structure and function
• The cell is the lowest level of organization that can perform all activities required for life
• All cells:
– Are enclosed by a membrane
– Use DNA as their genetic information
• ability of cells to divide is basis of all reproduction, growth, & repair of multicellular organisms
Compartmentalization
life is based on heritable information in the form of DNA
• DNA controls the development and maintenance of organisms
• DNA is inherited by offspring from their parents
• Genes are the units of inheritance that transmit information from parents to offspring
Homeostasis: Feedback mechanisms regulate biological systems
• Feedback mechanisms allow biological processes to self-regulate
• Negative feedback means that as more of a product accumulates, the process that creates it slows
and less of the product is produced
• Positive feedback means that as more of a product accumulates, the process that creates it
speeds up and more of the product is produced
Chemistry
Elements and Compounds
• Matter is made up of elements
• Element = substance that can’t be broken down to other substances by chemical reactions
Each element consists of unique atoms
An atom is the smallest unit of matter that still retains the properties of an element
 Element = 1 type of Atom,
 Ex: H, C, N, etc. these are elements
• Compound = substance consisting of two or more elements in a fixed ratio
Ex: H2O, NaCl are compounds
• A compound has characteristics different from those of its elements
 NaCl is table salt, Na is a metal, Cl is a gas chlorine
•Essential Elements of Life
- About 25 of the 92 elements are essential to life
- Carbon, hydrogen, oxygen, and nitrogen make up 96% of living matter
- Most of the remaining 4% consists of calcium, phosphorus, potassium, and sulfur
- Trace elements are those required by an organism in minute quantities
Chemistry
Atomic Structure
Atom - smallest unit of an element that retains the properties of that element
Element - Atoms with same number of protons
Atomic Structure – Model of an atom
Includes:
proton
Charge
+1 Positive
Mass
1 AMU
(n) neutron
0 Neutral
1 AMU
(e-) electron
-1 Negative
0 AMU
(p+)
Periodic table of elements
Avg of isotopes
Atomic Number = # protons
determines the element (NEVER CHANGES)
always the smaller number
Chemical Symbol
Atomic Mass (Weight) = # protons + # neutrons
always the bigger number
Neutral Atom = no charge
therefore # electrons = # protons
always start with a neutral atom
Be able to write this in various forms
=
7
Li
3
Note: Atomic number is on the bottom, mass number
is on top when talking about a specific atom
Subatomic
configuartion
Electron shell = energy level
The further out the more energy
Valence Shell – Outermost Shell
Octet Rule : shell 1 wants 2 electrons, other shells want 8 electrons
Isotopes - Same element but diff # of neutrons
Radioisotope = unstable neutrons that
decay and release radioactive particles
(Don’t know unless told)
Ions - atoms that have gained or lost electrons
(11p+; 12n0; 10e-)
(17p+; 18n0; 18e-)
Overall positive charge
Overall negative charge
Redox Reactions: Oxidation & Reduction
Chemical reactions that transfer electrons
Oxidation - substance loses electrons (is oxidized)
Reduction - substance gains electrons, (is reduced) (the amount of positive charge is reduced)
•The electron donor is called the reducing agent
•The electron receptor is called the oxidizing agent
The Energy Levels of Electrons
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Energy is the capacity to cause change
Potential energy is the energy that matter has because of its location or structure
The electrons of an atom differ in their amounts of potential energy
An electron’s state of potential energy is called its energy level, or electron shell
Electron Distribution and Chemical Properties
The chemical behavior of an atom is determined by the distribution of electrons in electron shells
• Valence electrons are those in the outermost shell, or valence shell
• The chemical behavior of an atom is mostly determined by the valence electrons
• Elements with a full valence shell are chemically inert
Covalent Bonds – Strongest – shares electrons
•Atoms can “share” one or more electrons with another atom
•The shared electron is in both atoms’ valence electron shell
(Therefore each atom gains an electron filling it outer shell)
•Every covalent bond represent 2 electrons
Chemical
symbols
1 line = 2 e-
CH4
Double (Covalent) bond
Triple (Covalent) bond
C has 4 bonds
N has 3 bonds (or 4 and is positive)
O has 2 bonds (or 1 and is negative)
H has 1 bond (or none and is positive)
Ionic Bonds – medium - Ions of opposing charge interact
= NaCl or Na+Cl-
Chemical
formula
Hydrogen – weak – attraction between electronegative and
electropositive atom
usually H (which is d+) to
N or O (which is d-)
polar
non-polar
Hydrophobic Bond – water hating – e.g. oil and water
driven by LACK of hydrogen bonding
Van der Waals Interactions
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If electrons are distributed asymmetrically in molecules or atoms, they can
result in “hot spots” of positive or negative charge
Van der Waals interactions are attractions between molecules that are close
together as a result of these charges
Extremely weak – but with lots of them, can add up
H2O - The Molecule That Supports All of Life
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Water is the biological medium on Earth
All living organisms require water more than any other substance
Most cells are surrounded by water, and cells themselves are about 70–95% water
The abundance of water is the main reason the Earth is habitable
4 properties of water contribute to Earth’s fitness for life
Hydrogen bonds affects properties of:
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cohesion (surface tension)
heat absorption
Density (expansion on freezing)
Solubility (versatile solvent)
A Lattice of Hydrogen Bonds
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Liquid water lattice – each water molecule
constantly breaks and reforms hydrogen bonds with
its neighbors (allows for absorption of heat)
Ice lattice – rigid, crystalline structure, spaces each
water molecule farther apart
Ice is ~10 less dense = floats
Water as a Solvent
H2O interacts with anything polar or charged
Hydration layer: Tends to coat anything polar or charged
Hydration layers reduce attraction between
molecules or ions and promote their entry into a
solution
Water (solvent) surrounds dissolved substance
(solute) and prevents them from reassociating (e.g.
sodium and chloride)
Therefore must have a lot more solvent
Chemical structures of Bonds
Indicates 4 H atoms
= CH4
Chemical formula
Only atoms in the relative proportion
Chemical symbols
Atomic Structure
(include protons, neutrons, electrons) 1. chemical symbols to represent atoms
Note: not complete above
2. Lines to represent covalent bonds (1 line = 1 bond = 2 electrons)
OH is often used for O-H
3. + or – to represent ions
4. Dotted lines represent hydrogen bonds
Functional Groups –
Responsible for a characteristic chemical reaction
methyl
R -OH
Carboxyl
group
Amino
Phosphae
Hydroxyl
or alcohol
R – is a variable, can represent anything
Like “x” in a math equation
ketone
aldehyde
Abbreviated chemical structures
Chemical symbols
1. Carbon at the end of every line, unless there is
already an element there
2. Each carbon has 4 covalent bonds, fill in missing
bonds with H
ester
Chemical Reactions
•Occur when chemical bonds are formed, rearranged, or broken
•Are written in symbolic form using chemical equations
•Chemical equations contain:
•Number and type of reacting substances, and products produced
•Relative amounts of reactants and products
• Synthesis reactions: Combination reactions: bond formation
A + B  AB
Examples:
• Decomposition reactions: Molecules are broken down into smaller molecules
AB  A + B
Glu-Fru
Glu + Fru
(Sucrose)
(Glucose)
(Fructose)
• Exchange reactions: Bonds are both made and broken
AB + C  AC + B
• Redox reactions: Oxidation (loss of electrons) Reduction (Gain of electrons)
(LEO the lion say GER)
2Na
+ Cl2
2Na+ + 2Cl-
Reversibility in Chemical Reactions
• All chemical reactions are theoretically reversible
A + B  AB
or
A + B  AB
AB  A + B
• If neither a forward nor reverse reaction is dominant, chemical equilibrium is reached
Energy Flow in Chemical Reactions
•Exergonic reactions – reactions that release energy
2Na + Cl2
2Na+ + 2Cl•Endergonic reactions – reactions whose products contain more potential energy than did its
reactants
Factors Influencing Rate of Chemical Reactions
•Temperature – chemical reactions proceed quicker at higher temperatures
•Particle size – the smaller the particle the faster the chemical reaction
•Concentration – higher reacting particle concentrations produce faster reactions
•Catalysts – increase the rate of a reaction without being chemically changed
•Enzymes – biological catalysts
Acids and Bases
Acids release H+ and are therefore proton donors
HCl  H+ + Cl –
Bases release OH– and are proton acceptors
NaOH  Na+ + OH–
•Acidic solutions have higher H+ concentration and
therefore a lower pH
•Alkaline (basic) solutions have lower H+ concentration
and therefore a higher pH
•Neutral solutions have equal H+ and OH–
concentrations
pH Scale
Measures concentration of H+
Acidic: pH 0–6.99
Basic: pH 7.01–14
Neutral: pH 7.00
Buffers
Systems that resist abrupt and large swings in the pH of body fluids
Carbonic acid-bicarbonate system
Carbonic acid dissociates, reversibly releasing bicarbonate ions and protons
The chemical equilibrium between carbonic acid and bicarbonate resists pH changes
in the blood
Carbonic acid
H+
H2CO3
+
HCO3-
If acid added: increase in H+ followed by shift to more Carbonic Acid
H2CO3
H+
+
HCO3-
If base added: decrease in H+ followed by shift to more bicarbonate
H2CO3
H+
+
HCO3-
Overall not much change in H+ concentration or pH
bicarbonate