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MOLECULES
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BIOL 1003
INTRODUCTORY
BIOLOGY I 4. Molecules of life: we are what we eat - FALL2014
Iain McKinnell – Dept. Biology
Introduction
• All organisms contain the same macromolecules.
• carbohydrates,
• proteins,
• lipids,
• nucleic acids.
• Core of these macromolecules is carbon
• Earths organisms are 18% carbon
• Carbon must flow from the atmosphere to
photosynthesizers to organisms
• Use carbon to build up tissues & power activities
Methane (CH4) is one of the simplest organic compounds.
Most organic molecules are not simple hydrocarbons however
Length. Carbon skeletons vary in length.
Ethane Propane
Butane Isobutane
Branching. Skeletons may be unbranched or branched.
Double bonds. Skeletons may have double bonds.
1-Butene 2-Butene
Cyclohexane Benzene
Rings. Skeletons may be arranged in rings.
The most simple organic
molecules are hydrocarbons
Functional Groups are key to the functioning of biological molecules
• An organic compound has unique
properties that depend upon the
• size and shape of the compound
• functional groups attached to it.
• A functional group affects a
biological molecule’s function in a
characteristic way.
• Often impart charge/polarity, changing
the bonding capacity.
• E.g. Add –OH to hydrocarbon and
you have an alcohol.
• Electronegativity of O results in polarity
• Compounds containing functional
groups are hydrophilic (water-loving).
Cells make a huge number of large molecules from a
limited set of small molecules
• There are four classes of molecules important to
organisms:
• carbohydrates,
• proteins,
• lipids, and
• nucleic acids.
• Each of these complex molecules comes from
simple building blocks
• They are polymers built by joining monomers
• E.g. Carbohydrates are built through the joining of
Monosaccharides-disaccharides-polysaccharides
Short polymer Unlinked
monomer
Dehydration reaction
forms a new bond
Longer polymer
Monomers are linked together to form polymers
through dehydration reactions
Glucose Glucose
Maltose
All biological reactions of this sort are mediated by
enzymes, which speed up chemical reactions in cells.
Polymers are broken apart by hydrolysis
Hydrolysis
breaks a bond
Polymer animation
Carbohydrates
• Major source of energy, also play a significant structural
role in both plants and animals
• Comprised of Carbon, Hydrogen & Oxygen
• Usually in a 1:2:1 ratio
• Consumed as nutrients
• Simple sugars (milk, juice, honey)
• Complex sugars (Veggies, pasta)
• Processed simple sugars
• Fibre - complex carbs not digested
Monosaccharides are the simplest carbohydrates
• Carbohydrates range from simple sugar molecules
(monomers) to large polysaccharides.
• The most simple sugars are monomers -
monosaccharides, such as
• Glucose
• fructose.
• Disaccharides also considered simple sugars
• Monosaccharides can be hooked together to form
• Polysaccharides (complex carbohydrates).
Polysaccharides are long chains of sugar units
• Polysaccharides are
• macromolecules and
• polymers composed of thousands of monosaccharides.
• Polysaccharides may function as
• storage molecules • Starch
• Glycogen
• structural compounds.
• Cellulose
• Chitin
Starch granules in potato tuber cells
Glucose monomer
Starch
Cellulose
Hydrogen bonds
Cellulose molecules
Cellulose microfibrils in a plant cell wall
Lipids • No monomer or structural unit common to all lipids
• Shared characteristic is that they are water insoluble (hydrophobic, or water-fearing)
• Consist mainly of carbon and hydrogen atoms linked by nonpolar covalent bonds • Also Oxygen (more H relative to O),
and phosphorus
• are important in long-term energy
storage
• fats,
• phospholipids, and
• steroids.
Fatty acids
Glycerol
Most common form of lipid
3 carbon glycerol linked to
fatty acids
Fatty acid – chain of hydrocarbons terminating in a COOH group.
90% of fats are triglycerides
Several different fatty acids types may combine to form a triglyceride
Fats (glyceride lipids)
Unsaturated vs. saturated fats
• Fatty acids containing one or more
double bonds - unsaturated fatty
acids
• cause kinks or bends in the carbon chain
• olive oils
• Fats with the maximum number of
hydrogens - saturated fatty acids
• animal fats
Fats animation
Unsaturated vs. saturated fats
• Hydrogenated
vegetable oils are
unsaturated fats that
have been converted
to saturated fats by
adding hydrogen.
• This hydrogenation
creates trans fats
associated with health
risks.
Phospholipids
• Phospholipids are
• structurally similar to fats -major
component of all cells.
• Glycerol attached to 2 fatty
acids and a phosphate head
group
• Phosphorus atom attached to four
oxygen
• Fatty acids tails – Hydrophobic
• Phosphate head – Hydrophilic
• Will bond with H20
Water
Hydrophobic
tails
Water
Hydrophilic
heads
Symbol for
phospholipid
Phosphate group
Glycerol
Steroids - a variety of functions
• Steroids are lipids in which the carbon skeleton contains
four fused rings.
• Cholesterol
• common component in animal cell membranes and
• starting material for making steroids, including sex hormones.
Proteins
• Chemical reactions are enabled by proteins
(enzymes)
• Also form scaffolding/structural support
• Dietary complete protein contains all the essential
amino acids required
• Beef, poultry, fish, eggs
• Nuts, pulses, vegetables
• Proteins are polymers of amino
acids
Proteins: amino acids linked by peptide bonds
Amino acids have
an amino group and
a carboxyl group (which makes it an acid).
Bonded to the central carbon is
a hydrogen atom and chemical group symbolized by R,
which determines the specific properties of each of the
20 amino acids used to make proteins.
Amino
group
Carboxyl
group
Proteins: amino acids linked by peptide bonds
• Amino acid monomers are linked together
• joining carboxyl group of one amino acid to the amino group of the
next amino acid, and
• creating a peptide bond.
• Additional amino acids can be added by the same process
to create a chain of amino acids called a polypeptide.
Carboxyl group
Amino group
Amino acid Amino acid Dipeptide
Peptide bond
Dehydration reaction
A protein’s specific shape determines its function
• A polypeptide chain contains hundreds or thousands of
amino acids linked by peptide bonds.
• The amino acid sequence causes the polypeptide to
assume a particular shape.
• The shape of a protein determines its specific function.
Groove
primary structure
secondary structure
tertiary structure
quaternary structure
Amino acids Amino acids
Beta pleated sheet
Alpha helix
Hydrogen bond
Transthyretin polypeptide
Transthyretin, with four identical polypeptides
A protein’s shape depends
on four levels of structure
Lipoproteins & glycoproteins
• Glycoproteins
• Carbs and proteins
• Receptors, some hormones, signaling
molecules
• Lipoproteins
• Lipid plus protein
• Transport fats
• LDL vs. HDL
Fat in the diet
• Health or harm of dietary fat is down to it’s effect on
lipoproteins
• Polyunsaturated fat containing omega-3 fatty acids
• Monounsaturated & polyunsaturated fat without omega-3
• Saturated fats
• Trans fat
• Polyunsaturated fat containing omega-3 fatty acids • Fatty acids with 2 or more carbon-carbon double bonds =
polyunsaturated
• Omega-3 is one such fatty acid – the C=C bond is between the 3rd and
4th carbon from the omega end
• Increase HDL, reduce fat in blood, reduce growth of deposits
• Salmon, mackerel, walnuts, canola, tofu
Fat in the diet
• Monounsaturated & polyunsaturated fats
without omega-3 • Monounsaturated fats (mostly oils)
• Leave LDL & HDL unchanged
• Mediterranean diet
• Non-omega-3 polyunsaturated fats • Slightly lower HDL (not considered harmful)
Fat in the diet
• Saturated fats
• Do the most to raise LDL levels
• 1% increase in diet leads to 2% increase in LDL (keep to
<7% of calories).
• Animal fat & dairy
• Trans fat – Industrial hydrogenation
• Turns oils into fats at room
temperature
• Raises LDL, lowers HDL
• Increases fat in blood, should
get <1% of calories
• Cookies, fries, cakes, etc
LIGHTSPRING/SHUTTERSTOCK.COM
Other biomolecular needs
• Micronutrients – required in small amounts
• Vitamins
• Most not synthesized (Vit D is synthesized by body)
• function as co-enzymes
• Best obtained via whole foods
• Minerals
• Not carbon but essential (Ca+, Na+, K+, etc)
• Obtain through food
• Antioxidants
• Prevent free radical damage
• Found in nuts, fruits, grains
Nucleic Acids
• For life to occur must have a mechanism for
passing traits to the next generation.
• All life on Earth uses nucleic acids
• DNA is the primary information bearing molecule
• Contains the recipe for all the proteins in the cell
DNA and RNA - nucleic acids
• The amino acid sequence of a polypeptide is programmed
by a discrete unit of inheritance known as a gene.
• Genes consist of DNA(deoxyribonucleic acid).
Gene
DNA
Transcription
RNA
Protein
Translation Amino acid
Nucleic
acids
Phosphate
group
Sugar
Nitrogenous base
(adenine)
Nucleic acids are polymers of nucleotides
• DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) are composed of monomers called nucleotides.
• Nucleotides have three parts: • a five-carbon sugar called ribose in RNA and deoxyribose in DNA,
• a phosphate group, and
• a nitrogenous base.
Base pair
A
C
T
G C
C G
T A
C G
A T
T A
G C
T A
T A
A T
Nucleic acids are polymers of nucleotides
Two polynucleotide strands wrap
around each other to form a DNA
double helix.
The two strands are associated
because particular bases always
hydrogen bond to one another.
A pairs with T, and C pairs with G,
producing base pairs.
RNA is usually a single
polynucleotide strand.
Summary • Understand the role of carbon and functional groups
• What are the four main classes of biomacromolecules?
• Describe dehydration and condensation reactions
• Carbs - Mono, di, polysaccharides
• Roles of carbs
• What are the 3 types of lipids
• What are the different structure and functions?
• Proteins
• Describe amino acid structure
• What are the four levels of protein structure?
• Nucleic acids
• What is the structure of a nucleotide?
…Next up – Chapter 4: A tour of the cell.