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Biochemistry
Organic Chemistry – The study of compounds containing carbon (C) atoms bound to other
elements such as hydrogen (H), oxygen (O) and nitrogen (N). The human body is 96% organic
compounds.
Note: Not all compounds that contain carbon are organic e.g. carbon dioxide (CO2), carbon
monoxide (CO) and carbonates (CO32-)
Functional Groups – Are a cluster of atoms that give compounds specific chemical properties.
Many organic molecules contain carbon atoms with functional groups attached.
See 5 important functional groups in Table 1 pg 25.
Macromolecules – Large organic molecules that contain dozens of carbon atoms and many
functional groups.
There are four major groups of biologically important macromolecules:
1.
2.
3.
4.
carbohydrates
lipids
proteins
nucleic acids
1.
CARBOHYDRATES
STRUCTURE: - molecules that contain carbon, hydrogen and oxygen
- primary building block of carbohydrates is glucose
FUNCTION:
- primarily used as a source of energy by living organisms
The Carbohydrate Family
MONOSACCHARIDES (simple sugars)
glucose
fructose
galactose
DISACCHARIDES (double sugars)
maltose
sucrose
lactose
POLYSACCHARIDES (complex carbohydrates)
glycogen
starches
fibres
Three types of Carbohydrates:
A) Monosaccharides (simple sugars) (mono = “one” and saccharide = “sugar” in Greek)
- the simplest carbohydrate, sweet-tasting, water soluble
- the three key monosaccharides have the same number and type of atoms but in different
arrangements (6 carbons, 12 hydrogens, 6 oxygens – some of the oxygen and hydrogens are
in the form of hydroxyl groups)
Glucose (C6H12O6) – primary energy source for living things
Fructose (C6H12O6) – sweetest of sugars, found in fruits and honey
Galactose (C6H12O6) – seldom occurs naturally, when bound to glucose it is found in milk
B) Disaccharides (double sugars)
- two monosaccharides bonded together (glucose is always included), water soluble
SUCROSE = GLUCOSE + FRUCTOSE
- table sugar, fruits, vegetables and grains
MALTOSE = GLUCOSE + GLUCOSE
- produced whenever starch breaks down e.g. during carbohydrate digestion and
fermentation
LACTOSE = GLUCOSE + GALACTOSE
- principle carbohydrate of milk
C) Polysaccharides (complex carbohydrates)
- contain many glucose units and a few other monosaccharides strung together as long chains
called polysaccharides
- polysaccharides are insoluble and very large, therefore when eaten, reactions in the digestive
system break everything down to glucose molecules
- there are three important polysaccharides: glycogen, starches, and fibres
Glycogen
- not a significant food source of carbohydrates
- animals store glucose as glycogen in muscle cells, liver cells, and certain types of white cells
- when blood glucose levels drop, certain hormones (e.g. glucagon) are released which cause
stored glycogen to be broken down into glucose which can then be used by the cells
Starches
- a major source of energy
- just as animals store glucose as glycogen, plants store glucose as starch
- all starchy foods come from plants e.g. potatoes, grains, beans
- when you eat a starch your body breaks the starch down into glucose molecules
Fibres
- are the structural parts of plants and are therefore found in all plant-derived foods e.g.
vegetables, fruits, grains and legumes
- unlike starches, fibres cannot be broken down by human digestive enzymes, instead they are
broken down by the BACTERIA of the gastrointestinal tract
- there are different types of fibres:
- cellulose – primary component of plant cell walls
- can only be broken down by ruminants e.g. sheep and cows
- chitin
- is a modified form of cellulose which makes up the hard exterior
skeletons of insects and crustaceans, such as lobsters and shrimp
- used in contact lenses and decomposable stitches
2. LIPIDS
STRUCTURE: - the primary building block of lipids is fatty acids
FUNCTION:
- lipids are primarily used by animals to store energy
The Lipid Family
1.TRIGLYCERIDES
saturated fats
unsaturated fats
trans - fats
2. WAXES
3. PHOSPHOLIPIDS
4. STEROIDS
1. Triglycerides: Oils and Fats
- composed of triglyceride molecules
- triglyceride molecules are the main form of fat in the diet and the major storage form of fat in
the body (composed of a glycerol backbone with 3 fatty acids attached)
Saturated, Unsaturated and Trans-Fats
Type
Saturated Fats
(Saturated fatty
acids)
Structure
- fully loaded with
hydrogens
- single bonds between
carbon atoms of fatty
acid
Properties
- solids at room
temperature
- do not become rancid
quickly (resist oxidation)
Unsaturated Fats
(Unsaturated fatty
acids)
- missing hydrogens
- one or more double
bonds between carbon
atoms of fatty acid
- liquids at room
temperature
- become rancid easily
Trans – Fats
(Trans – fatty acids)
- hydrogen atoms are
added to an unsaturated
fatty acid
(hydrogenation)
- unsaturated fats with
the advantages of
saturated fats
i.e don’t oxidize (become
rancid) as quickly and
have enhanced texture
(creamy) and taste
Examples
- most animal fats (e.g.
lard and butter)
* play a role in coronary
artery disease
- plant oils (e.g.
sunflower, canola and
olive oil)
- spreadable margarine
- cakes, cookies
- peanut butter
- fried foods
* play a role in coronary
artery disease
Waxes, Phospholipids and Steroids
Type
Waxes
Phospholipids
Steroids
Description
lipid molecules commonly used by plants
and some animals as waterproof coatings
play a key role in the structure of the cell
membrane
arranged in rings
Examples
bees wax
cherries – water resistant coating
lecithins – food industry uses it as an
emulsifier (combine two ingredients
that do not ordinarily combine e.g.
water and oil)
cholesterol – comes from animal
products
hormones – testosterone and estrogen
3. PROTEINS
STRUCTURE: - proteins are composed of carbon, hydrogen, oxygen and NITROGEN
- the building blocks of proteins are amino acids (amino acids are linked by
peptide bonds, therefore, a small chain of amino acids is called a polypeptide)
- there are 20 different amino acids
FUNCTION:
- many different functions (see key functions below)
Key Functions of Proteins
FUNCTION
Speed up chemical reactions
Support cell and body structures
EXAMPLE
enzymes e.g. lactase, amylase
keratin in hair, silk in spider webs, muscle and collagen
Essential versus Nonessential Amino Acids
Type
Essential Amino Acids
(9)
Nonessential Amino Acids
(11)
Description
The body cannot synthesize (make) at all or
not enough to meet its needs. These amino
acids must be supplied by the diet.
The body can synthesize.
Examples
leucine
lysine
histidine
alanine
glutamine
glycine
What is denaturation?
- a process by which the peptide bonds between the amino acids are broken
- can be caused by heat, acidic, basic or salty environments
Examples:
- fever can denature neural enzymes and can lead to seizures
- heat can denature the keratin in hair and therefore allow for perming and straightening
- pickling foods in vinegar preserves the foods by denaturing the enzymes in bacteria
- cooking denatures the proteins in foods so that the food can be easily broken down
4. NUCLEIC ACIDS
STRUCTURE: - the building blocks of nucleic acids are nucleotides
FUNCTION:
- organisms use nucleic acids to store and decode hereditary information (i.e.
nucleic acids provide the blue print for the body)
Two Types of Nucleic Acids:
1. DNA (deoxyribonucleic acid)
- stores genetic information
- double helix structure
- made of four nitrogenous bases: guanine, thymine, cytosine, adenine
- A and T pair and G and C pair
2. RNA (ribonucleic acid)
- decodes genetic information
- single helix structure
- nitrogenous bases are not paired
- instead of thymine, RNA contains uracil
Characteristics of Biological Macromolecules
Macromolecule
Carbohydrates
monosaccharides
disaccharides
polysaccharides
Lipids
Proteins
Nucleic Acids
Structure of typical
subunit
Examples
Functions