Transcript The Chemical Basis of Life

Chemistry and biological
molecules
Matter is anything that occupies space
and has mass.
Energy is the capacity to do work.
Potential (stored) energy
Kinetic energy (energy of motion)
Elements are substances which cannot be split
into simpler substances by ordinary chemical
reactions.
Each element has a one or two letter chemical
symbol.
O
C
H
N
Ca
P
K
Na
Cl
Mg
S
Fe
I
Oxygen
65 % of total body weight
Carbon
18.6
Hydrogen
9.7
Nitrogen
3.2
Calcium
1.8
Phosphorus
1.0
Potassium
0.4
Sodium (Natrium) 0.2
Chlorine
0.2
Magnesium
0.06
Sulfur
0.04
Iron (Ferrum)
0.007
Iodine
0.0002
O, C, H, N
= 96 % of body weight
Add
Ca and P
= 98.5 % of body weight
Add
K, S, Cl, Na and Mg = 99.9.% of body weight
“Bulk Elements”
Atoms are the smallest unit of an element that
still has the chemical properties of that element.
Atoms:
Have a central nucleus
Protons (+)
Neutrons (0)
Orbitals on the outside that hold
Electrons (-)
The number of electrons in the outermost
shell determines how each atom interacts
with other atoms.
Atomic number = the number of protons in the
atom.
Atomic weight (or Mass number) = the total
number of protons and neutrons
Expressed in daltons or atomic mass units
Isotopes are atoms of an element that all
have the same number of protons, but have
different numbers of neutrons.
Radioisotopes – radioactive decay
The time it takes for half of a radioactive
substance to decay is called its half-life.
When two or more atoms combine in a
chemical reaction, a molecule is formed.
When a molecule contains two or more atoms
of different elements, it is called a compound.
CO2
H 2O
NaCl
C12H22O11
Atoms are held together by forces of attraction
called chemical bonds, which are forms of
potential energy.
Ionic bonds
Covalent bonds
Hydrogen bonds
In an ionic bond electrons are transferred
from one atom to another. Opposing charges
hold the atoms together.
An ion is a charged particle (atom or molecule).
Na+
Cl-
Ca++
positive charge - cations
HCO3- negative charge – anions
Substances that breaks into positively and
negatively charged ions in solution are called
electrolytes.
An ion or molecule that that contains
unpaired electrons in its outermost energy
level is called a free radical.
Nitric Oxide is a free radical
neurotransmitter
blood clotting and vessel dilation
defense against pathogen
Cumulative damage = aging process
Covalent bonds are formed when atoms
share electrons. These are the strongest
bonds.
C-C
Double covalent bonds
C=C
Triple covalent bonds
N≡N
When one end of molecule has a
positive charge (δ+) and the other has
a negative charge(δ-), the molecule is
polar. (polar covalent bonds)
When molecules have a more uniform
distribution of charges they are called
nonpolar molecules. (nonpolar
covalent bonds)
Polar molecules are hydrophilic .
“water loving”
Nonpolar molecules are hydrophobic.
“water fearing”
Surface tension
slows rate of evaporation
lung function
tear film
Hydrogen bonds are weak but important
bonds. They do not bind atoms into
molecules, but are important in giving large
molecules their shape.
Involve interaction between δ+ of a hydrogen
and δ- of oxygen, nitrogen or fluorine
Chemical reactions involve making and
breaking bonds.
Making bonds requires the input of energy.
Energy is stored in molecules in the
chemical bonds.
Breaking bonds usually releases energy.
Synthesis reactions - Anabolism
A +
B
→
Reactants
AB
Products
Decomposition reactions – catabolism
AB → A + B
Exchange reactions involve the
replacement of one atom or atoms by
another atom or atoms.
AB + CD
→
AD
+ BC
In Reversible reactions end products can revert
to the original combining molecules.
AB ↔ A + B
CO2 + H2O ↔
H2CO3 ↔ H+ + HCO3carbonic
bicarbonate
acid
ion
Catalysts are molecules that influence the
rates of chemical reactions, but are not
consumed (used up) in the reaction.
Enzymes are biological catalysts (proteins).
-ase
Activation energy
Exergonic or exothermic
Endogonic or endothermic
Inorganic Compounds
CO2, O2, H2O and acids, bases
and salts
Inorganic acids, bases and salts dissociate
into ions in water.
Acids - one or more hydrogen ions (H+)
and one or more anions.
Bases - hydroxide ion (OH-) and one or
more cations.
A salt ionizes into anions and cations,
neither H+ nor OH-
pH
The pH is the negative log of the hydrogen
ion concentration.
The more hydrogen ion a solution has, the
lower its pH is.
Why is pH critical to body functioning?
Water
Water is the most abundant substance in
the body.
It is an excellent solvent.
Water participates in chemical reactions:
dehydration synthesis - combines
atoms with the removal of water
hydrolysis – breaks apart molecules
with the addition of water.
Water has a high heat capacity – good for
cooling.
Good for lubrication (pleura, etc.)
Good suspending medium - blood
Inorganic substances usually lack carbon
and are small molecules; many contain
ionic bonds and are electrolytes.
Inorganic ions are important to body
functions
Na+, K+, Ca++, HCO3-
Organic molecules
Organic compounds always contain carbon.
Other common elements are hydrogen,
oxygen and nitrogen.
Carbon compounds are held together by
covalent bonds, tend to decompose easily, and
are a good source of energy.
Macromolecules – large organic molecules
Formed by linking smaller repeating units
called monomers together. (subunits)
Many monomers linked together make a
large molecule called a polymer.
Classes of organic molecules
•Carbohydrates (sugars)
•Lipids
•Proteins
•Nucleic Acids
Carbohydrates
•Supply energy and build some cell structures
•Include sugars, starches, glycogen and
cellulose
•Always
Cx(H2O)y
• can have same formula (glucose and
fructose) but differ in shape (isomers)
• Monosaccharides are the monomers
Simple sugars
• 3-7 carbons
• Names end in –ose
• Mono and disaccharides dissolve in water
and are rapidly distributed
• Polysaccharides formed by dehydration
synthesis
• Chains can be straight or highly branched
• Glycogen in liver and muscle
• Polysaccharides do not dissolve in water
and are not “sweet”
Lipids
•Contain C, H, O
•C:H nearly 1:2
•Tend to be hydrophobic (nonpolar)
•Tend to be insoluble in water (blood)
•Diverse group : fats, oils, waxes
•Fatty acids, triglycerides, phospholipids,
glycolipids, steroids and eicosanoids
Lipids
•
•
•
•
•
Concentrated chemical energy
Good storage form
Cell membranes
Protect
Insulate
Fatty acids
• One end has a carboxyl group – COOH
• Hydrocarbon tail
– The longer the tail the lower the solubility
• Fatty acids bind to glycerol to form neutral
fats or triglycerides
• Trans fatty acids
– Cis:
C=C
Trans:
C=C
• omega-3 fatty acids
• Phospholipids and glycolipids
Phospholipids - amphipathic
Steroids are lipids
• Eicosanoids – prostaglandins
Prostatglandins
• Local hormones
• leukotrines
Proteins
•Functions:
•Support
•Movement
•Transport
•Buffering
•Metabolic regulation
•Coordination and control
•Defense
Proteins
• Contain C, H,O and N (nitrogen)
• Sometimes sulfur or phosphorus
• Made up of amino acids
• Amino group – NH2
• Carboxyl (acid) group – COOH
• Side chain or R group
• Central carbon
• Acts as an anion – Pr -
A protein’s structure determines its function
If it loses its structure, it is denatured, and
no longer functions.
Proteins may be enzymes end in “ –ase”
protein – apoenzyme
nonprotein – cofactor
organic molecule – coenzyme - vitamins
holoenzyme
Nucleic Acids
•Made up of C, H, O, N, and P
•Deoxyribonucleic Acid – DNA
•Ribonucleic Acid – RNA
•Monomers are called nucleotides
•Sugar, Phosphate group,
nitrogenous base
DNA
vs.
RNA
Uses A,T, C and G
Uses A, U, C and G
Use deoxyribose
Uses ribose
Double stranded
Single stranded