Biochemistry
Biology 20
Chemistry of Life
• 98% to 99% of living matter is made up of 6
atoms
– Carbon, Oxygen, Hydrogen, Nitrogen, Phosphorus
and Sulphur
• Metabolism is the sum of all chemical reactions
•
that take place within the cell
The four most important organic compounds
are:
– Proteins, Carbohydrates, Lipids and Nucleic Acids
Types of Proteins
• Proteins function in the growth, repair and
•
protection of living tissue
Special Proteins in the human body include:
Name
Antibodies
Enzymes
Hormones
Function
Immune
Response
Catalyse
Reaction
Chemical
Messengers
Example
Antibody A
Sucrase
Insulin
Protein Structure
• Proteins are built from 20
different types of amino acids
– 8 essential amino acids (obtained
from food)
• AA  joined by peptide bonds 
•
Polypeptide Chains  Proteins
Proteins can be almost any 3D
shape, therefore the often work
by using a lock and key fit
Chemistry of Proteins
Leucine
• Chemically composed of C, H, O and N
• Broke down for energy after carbohydrates and lipids
•
(Anorexia)
Deamination – breakdown of proteins into amino acids
– Proteins  Ammonia  Urea  Urine
(Poisonous) (Safe)
• Denaturation – a temporary change in the shape of
•
protein do to expose to extreme heat, acidity or radiation
Coagulation – permanent change in the shape of a
protein.
Formation and Breaking of
Chemical Bonds
• Dehydration Synthesis –
•
•
removing water in order to
form a new bond
Hydrolysis – using water to
aid in the breaking of a
bond
Dehydration Synthesis and
Hydrolysis are used to join
or break apart proteins,
carbohydrates and lipids
Characteristics of a Carbohydrate
• Function: The most readily available
source of energy for our body.
• Chemically composed of Carbon,
Hydrogen and Oxygen in 1:2:1 ratio.
C6h12O6 - glucose
Types of Carbohydrates
• Monosaccharide
– Simple sugars
– Glucose (fuel for the human body), fructose, ribose
• Disaccharides
– Combination of two monosaccharides.
– Sucrose (table sugar) – glucose and fructose
• Polysaccharides
– Formed from long chains of monosaccharides (joined by dehydration
synthesis)
– Stored form of glucose in plants and animals
• Starch – stored form of glucose in plants
• Cellulose – component of the cell wall, cannot be digested in humans.
• Glycogen – stored for of glucose in humans
Characteristics of Lipids
• Lipids are used for energy, storage
•
•
•
and cushioning.
Lipids compose the cell membrane,
help with the absorption of
vitamins and help build hormones.
Chemically composed of carbon,
hydrogen and oxygen but in no
fixed ratio.
Composed of glycerol and fatty
acids (joined by dehydration
synthesis)
Types of Lipids
• Monoglycerides
– Composed of 1 glycerol and 1 fatty
acid
• Diglycerides
– Composed of 1 glycerol and 2 fatty
acids
• Triglycerides
– Composed of 1 glycerol and 3 fatty
acids
Case Study – Fats and Health Pg 248
Nucleic Acids
• Building blocks of the genetic code
• Forms the DNA which in turn is the
•
molecule that makes up your
chromosome (DNA – deoxyribose
nucleic acid)
Composed of 4 nitrogen bases
– Adenine   Thymine
– Cytosine   Guanine
• Nucleotide
– Sugar/Phosphate backbone and
nitrogen base
Test Substances
• Benedict’s Solution – tests for
monosaccharides
– Blue  Orange/Red
• Iodine – tests for starches
– Amber  Blue/Black
• Beuret’s Reagent – tests for
peptide bonds (proteins)
– Blue  Pink/Purple
• Sudan IV Solution – tests for
lipids
– Clear  Pink/Red
• Translucence test (brown bag) –
tests for lipids
– Bag becomes transparent
The Importance of Water
•
•
•
•
•
•
•
•
•
•
•
•
Absorbs and releases energy (moderates temperature)
Is the medium in which metabolic reactions take place in organisms
Is an excellent solvent
Composes about 60% of the cells mass
Cushions the body organs
Lubricates body parts – joints
Cleaning – tears and saliva
Important for the breakdown of chemicals – hydrolysis and
dehydration synthesis
Dissolves particles for transportation
Provides H+ and OH- for acid-base reactions
It comprises 70% of the human body
Covers two-thirds of out planet ( 97% salt water, 3% fresh water)
Characteristics of Water
• Occurs in all there states: liquid, gas, solid
• High freezing point (o degree Celsius) and high boiling point
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(100 degree Celsius)
High heat of vaporization – amount of energy needed to
turn liquid into gas (cools our body – sweat)
High heat of fusion – amount of energy needed to turn a
solid into a liquid.
Cohesion – tendency of like molecules to cling together
Adhesion – tendency of unlike molecules to cling
together (capillary action)
Surface tension
Acids and Bases
• H2O  H+ + OH• Producing acids and bases
–
–
–
Neutral substances H+ = OHAcidic substances H+ > OHBasic substances H+ < OH-
• The pH scale
• Buffers
–
Absorb excess fluctuations in the levels of acids and bases. Maintain a substance at a
specific pH.
• Neutralizers
–
Maintains the pH at 7.
–
–
–
Stomach ph 2.4
Blood pH 7
Vagina ph 4.5
• Examples
Enzymes
• Enzymes are special
•
•
proteins that increase
the speed (catalyze)
of chemical reactions
Enzymes are not used
up in the chemical
reaction.
Examples of enzymes
Enzyme
Substrate
Location
Amylase
Starch
Mouth
ATPase
ADP
Mitochondria
Lactase
Lactose
Sm. Intestine
Lipase
Lipids
Sm. Intestine
Maltase
Maltose
Sm. Intestine
Pepsin
Proteins
Stomach
Enzyme - Lock and Key Fit
• Substrate – the molecule that
•
•
•
fits with the enzyme
Enzyme-Substrate complex –
when a molecule and enzyme
become locked together
Product – end result of the
reaction
Active Site – the area on the
enzyme in which the
substrate attaches.
Rate of Enzyme Activity
• Factors that affect the rate of enzyme activity:
– Temperature
• 37 C is optimal
• Colder or warmer they slow down
• Denaturation at 45 C
– Acidity
• pH sensitive. Designed to function of specific pH
– Substrate Concentration
• Decrease substrate concentration, decrease enzyme activity and
visa versa
– End Product Concentration
• As end product concentration increases enzyme activity will
•
decrease
Some end product are poisonous in high concentration
Coenzymes and Cofactors
• Alter the active site so the enzyme will fit
a new substrate.
• Normally vitamins
Competitive Inhibitors
• Block the active site of an enzyme.
•
•
Therefore prevents contact from
the substrate
Most competitive inhibitors are
reversible and only temporarily
block the active site.
Cyanide – irreversible inhibitor.
Prevents to production of ATP by
the mitochondria.