covalent bondsbiology100vvc.weebly.com/uploads/6/7/9/9/6799747/...• has 4 valence electrons •...

of

25

CHEMICAL BONDS

DEFINITION/DESCRIPTION:

Attraction that holds molecules together

Involves valence electrons

TYPES:

Ionic Bonds

Transfer of electrons from one atom to another

Difference in electronegativity is high Electronegativity = atom’s ability to attract and hold electrons Forms ions Cations = positive ions Anions = negative ions Weak bonds in solution

Covalent Bonds Involves sharing of electrons

Electronegativities O = 3.5 N = 3.0 C = 2.5 H = 2.1 Nonpolar = electrons shared equally C-C or C-H Small or no difference in

electronegativity

Polar = electrons NOT shared equally C-O or H-O

Difference in electronegativity is larger than nonpolar but smaller than ionic

TYPES:

of

25

of

25

WATER, ACIDS, BASES, BUFFERS

of

25

PROPERTIES OF WATER:

Liquid water is cohesive Cohesion = H bonds between water molecules; H2O molecules tend to stick tog. Importance = Transport H2O against gravity in plants Higher surface tension

Water has a high specific heat Takes a lot of energy to raise 1 gram of H2O 1 oC Why? Must break H bonds Liquid H2O can absorb large amounts of heat with small changes in temperature

Water has a high heat of vaporization Takes a lot of energy to convert liquid H2O into vapor Why? Must break H bonds Keeps water in liquid state

Water expands with it freezes Solid H2O is less dense than liquid H2O Why? In solid state H2O locked into max. number of H bonds; takes up more space

Water is a versatile solvent Will dissolve polar covalent and ionic compounds

of

25

DISSOCIATION OF WATER:

H2O + H2O + OH-

H2O + OH-

Hydronium ion Hydroxide ion

1 out of 554,000,000 water molecules dissociates At equilibrium in pure water at 25oC

[H+] = [OH-] = 1.0 x 10-7 M

If add [H+] to pure water If add [OH-] to pure water Removes OH- Removes H+ Equilibrium shifts left Equilibrium shifts right

[H+] > [OH-] [OH-]>[H+] reduces H+ indirectly

If add NH3 NH3 + H+ NH4+ Reduces H+ directly

H3o H+

PH SCALE: pH = -log10[H+]

[H+] x [OH-] = 10-14

If [H+] = 10-7 If [H+] = 10-9

Then [OH-]=10-7 Then [OH-] = 10-5

pH = 7 pOH=7 pH=9 pOH=5

of

25

BUFFERS:

Description Function Importance

Weak acids or bases

Minimize changes in pH

Controls chemical

reactions

Maintains homeostasis

BICARBONATE BUFFER SYSTEM:

H2O + CO2 H2CO3 HCO3— + H+

HCO3- = Bicarbonate (weak base)

H2CO3 = Carbonic acid (weak acid)

Major buffer system in blood

Maintains blood pH between 7.38 and 7.42

Action: Effect:

Increase [H+] How?

Fat metabolism OD on acidic

drug

Increase [H+]

Equilibrium shifts left

H+ + HCO3- H2CO3 CO2 + H2O

Increase [CO2]

Increase rate and depth of respiration

Increase Rate &

Depth of Respiration

Hyperventilate

Decrease [CO2] (CO2 is acidic)

Equilibrium shifts right

H+ + HCO3- H2CO3 CO2 + H2O

Blood pH increases

of

25

PROPERTIES OF CARBON:

• Has 4 valence electrons

• Form 4 covalent bonds (single, double, triple)

• Carbon chain

− Straight, branching, ring

− Varies in length, number and location of double bonds, and presence of

other elements

• Forms isomers

C6H12O6 chemical formula for glucose, fructose, & galactose

CARBOHYDRATES

General Characteristics

- Polymers of Simple Sugars

- Classified according to number of

simple sugars

- Sugars

- 3 - 7 carbons

C 6 H 12 O 6

of

25

Functional Groups: Affect a molecule’s function by participating in chemical reactions.

FUNCTIONAL

GROUP

DRAWING/FORMULA PROPERTIES

Hydroxyl

•

•

•

Polar Water soluble Alcohols

Carbonyl

•

•

Polar Water soluble

Carboxyl

•

•

•

Polar Water soluble Acid

Amino

•

•

•

Polar Water soluble Weak base

Sulfhydral

•

•

•

Form disulfide bridges

Stabilize protein shape

Polar

Phosphate

•

•

•

Polar Water soluble Acid

• Important in energy transfer

of

25

FUNCTIONAL

GROUP DRAWING/FORMULA PROPERTIES

Methyl

•

•

Nonpolar Not water soluble

MONOSACCHARIDES:

Trioses Simple sugars 3-carbon sugar Monomers of di- and polysaccharides glycerahdehyde Store energy in chemical bonds Pentose

5-carbon sugar Ribose

Deoxyribose Hexose 6-carbon sugar

Glucose Fructose

Galactose

Glu cose Glucose

Linear

form

(dry)

Ring form (in sol’n)

of

25

DISACCHARIDES: Double Sugars

Condensation Synthesis: Removal of water molecule to form bond between monomers

Hydrolysis: Addition of water to break bonds

POLYSACCHARIDES: Many monosaccharides covalently bonded together

FUNCTIONS:

Storage Starch: storage carb. in plants Glycogen: storage carb. in animals

Structural Cellulose: plant cell wall component Chitin: polymer of amino sugar Building block of exoskeletons

STARCH VS CELLULOSE

Starch –branched chains of GLC

Cellulose –unbranched chains of GLC Most animals lack enzyme to break

Glucose + Fructose Sucrose + water

Glucose + Glucose Maltose + water Glucose + Galactose Lactose + water

of

25

LIPIDS

General Characteristics: Not soluble in water

Mostly hydrocarbon chains

Fats, steroids, phospholipids

Fats:

Glycerol + fatty acids Compact energy source

Triglycerides have 3 fatty acids Cushions vital organs

Fatty acids present may vary Provides insulation

Building Blocks:

3

+ 3 H 2

of

25

Saturated:

No double bonds between carbons Straight chain

Fatty acid

Usually solid at room temperature Straight chains allow for tight packing

Most animal fats

Unsaturated:

At least 1 double bond between carbons

Hydrocarbon chain is bent

Usually liquid at room temperature Bent chain prevents tight packing Most plant fats

of

25

of

25

PROTEINS

GENERAL CHARACTERISTICS AND IMPORTANCES:

• Polymers of amino acids

• Each has unique 3-D shape

• Vary in sequence of amino acids

• Major component of cell parts

• Provide support

• Storage of amino acids

• Receptor proteins; contractile proteins; antibodies; enzymes

UILDING BLOCKS:

Amino acids

20 different

amino acids

ANION CATION DIPOLAR ION

of

25

PEPT IDE BONDS :

of

25

of

25

DENATURATION:

Changing protein’s native conformation

Change shape = change in activity

How?

1. High temperature

2. Chemical agent (acid or base) change in pH

3. Organic solvent

ENZYMES

Enzyme-Protein that functions as biological catalyst

Catalyst-substance that speeds up the rate of a chemical reaction

without being altered or consumed in the reaction; decreasing the

amount of energy needed in the reaction.

Functions:

-facilitate chemical reactions

Reactants (substrates)Products

-important for maintaining homeostasis

-without enzymes life would occur too slowly to maintain life.

of

25

DNA STRUCTURE AND REPLICATION

BUILDING BLOCKS OF DNA:

Nucleotides:

1. 5 carbon sugar (deoxyribose)

2. Nitrogenous base (A, T, C, or G)

3. Phosphate group

NITROGENOUS BASES

PYRIMIDINES PURINES

Single ring structure C and T Double ring structure G and A

Cytosine Guanine

Thymine Adenine

of

25

DNA STRUCTURE

of

25

One strand 5’ at top & 3’ at bottom

ANTIPARALLEL STRANDS

Other strand: 5’ at bottom & 3’ at top

5 ’ end

5 th carbon in

deoxyribose

3 ’ end

3 rd carbon

in

deoxyribose

Nucleotide

of

25

ATP Carries Energy

LAWS OF THERMODYNAMICS

First Law

Second Law

• Energy cannot be

created or destroyed

• Energy can be

transferred and

transformed

• Every energy transfer

makes the universe more

• disordered

Entropy = measure of

disorder

• Whenever energy is

transferred some is lost as

heat

• Amt of useful energy

decreases whenever energy

is transferred

PROBLEM

Living organisms are highly ordered; decrease entropy

Question: Do living organisms violate the 2nd law?

ANSWER

No

• Living organism is a closed system

• Must consider organism & environment

• Living organisms

Maintain highly ordered structure at expense of increased entropy of surroundings

Take in complex high energy molecules, extract

energy, release simpler, low energy molecules (CO2 and

H2O) and heat to environment

EXERGONIC REACTIONS

of

25

Reactants have more

energy than products

More ordered to less

Unstable to stable

Downhill reaction

Free energy released

Spontaneous

Examples

Cellular respiration

Digestion

ENDERGONIC REACTIONS

Products have more

energy than reactants

Less ordered to more

Stable to unstable

Uphill reaction

Free energy absorbed

from surroundings

Examples

Photosynthesis

Polymer synthesis

of

25

COUPLED REACTIONS

Energy released from

exergonic reaction

drives

endergonic reaction

Exergonic Reaction

∆G = max. work that can

be done

Endergonic

Reaction ∆G = min.

work needed to

drive reaction

ATP

Adenosine triphosphate

Has unstable phosphate bonds

of

25

ATP STRUCTURE

Adenine

Ribose

(5 - C sugar)

Phosphate groups

Unstable, high -

energy bonds

of

25

HOW ATP DOES WORK

TYPE OF WORK DESCRIPTION

Mechanical

Beating cilia

Muscular contraction

Movement

Transport

Active transport

Pumps (H+ and Na+/K+)

Chemical

Endergonic reactions

Polymerization

covalent bondsbiology100vvc.weebly.com/uploads/6/7/9/9/6799747/...• has 4 valence electrons •...

Documents