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.