The Structure and Function of Macromolecules

What are Macromolecules?

They are ENORMOUS…as far as molecules go. Many are composed of thousands of atoms

Extremely complex Shape is often vital to function

Most biological molecules are macromolecules This does NOT mean that smaller and/or inorganic

molecules are unimportant to life.

Polymers

Monomer Many smaller subunits that are either similar

OR identical to each other

Polymer is a long molecule Covalent bonds link monomers (subunits)

Making a Polymer

Dehydration synthesis

Joining of monomers with a covalent bond Water is lost as a result

Breaking Down a Polymer

Hydrolysis Reactions Monomers separated by adding water Covalent bond between monomers is broken

Variety of Organic Macromolecules

Relatively few building blocks still lead to incredible variety in the molecules made

This is due to the ARRANGEMENT of the molecules – HOW they are put together.

CARBOHYDRATES

Sugars and their polymers

Elements: C, H, O H:O always 2:1

Functions Energy (quick) Storage of Energy Building and support

materials

Monosaccharides (simple sugars)MONOMERS of the carbohydrate Monosaccharide = simple sugar (CH2O)n

Glucose (C6H

12O

6) most common

FUNCTION: quick energy and as monomers for all other carbohydrate molecules

Monosaccharides

Can be shown as a linear molecule More realistic representation is as a ring Sugars form rings in aqueous solution Note that each bend in the ring is a carbon atom Note that Hydrogens and Hydroxyl (OH) groups extend from each

carbon (except one).

Disaccharides

Two monosaccharides bound together

As in all organic molecules, these covalent bonds are created through dehydration reactions.

glycosidic linkages

Examples of Disaccharides

Glucose + Glucose = Maltose

Glucose + Galactose = Lactose

Glucose + Fructose = Sucrose

Examples of Disaccharides

Functions of Disaccharides

Function 1 Transport in plants Sugar being transported from leaves to roots is

more safe (resists being consumed by the plant) when transported as sucrose.

Side note: Few adult mammals have the necessary

enzymes to break down lactose Preserves milk supply for young who need it

Polysaccharides

macromolecule - few hundred to a few thousand monosaccharides linked covalently (glycosidic linkages)

FUNCTION 1 Energy Storage

FUNCTION 2 Building and support material

Storage Polysaccharides

Starch Made only by plants

(Animals can break down starch , but they cannot make it)

Storage Polysaccharides

Glycogen Storage polysaccharide created and used by

ANIMALS Found in the liver and muscles Highly branched chains of glucose

Only about a day’s supply of glycogen is stored in the body

Note: Polysaccharides are NOT the major energy storage compound in animals that they are in plants

Glycogen – diagram and photo

Structural Polysaccharides

Structural polysaccharides are those that are used in building physical structures in an organism

Most often we think of cell walls in plants, but there are others.

Cellulose

Structural polysaccharide that makes up plant cell walls

The bulk of the woody part of a plant

Cellulose structure Long chains of glucose – similar to starch Glucose molecules are linked differently from starch Difference makes cellulose indigestible to almost all

organisms EXCEPT bacteria and some other microbes

Cellulose – detailed diagram

Chitin

Chitin is a structural polysaccharide found in Arthropod

exoskeletons (insects, crabs, lobsters, etc.)

Cell walls of fungus Also used to make

strong surgical thread that decomposes after healing of the wound.

LIPIDS

Elements : C, H, O (way less O than Carbs)Major types Fats and oils Waxes Phospholipids steroids

Functions Energy storage Insulation Cushioning Cell communication Make up membranes

Lipid Structure

Composed of two kinds of smaller molecules Glycerol

An alcohol 3 carbons each with an –OH group

Fatty acids LONG carbon / hydrogen chains Carboxyl group at one end Hydrocarbon tail makes up bulk of the fatty acid

Glycerol linked to 3 fatty acids with ester bonds/linkages

Ester bond = type of covalent bond

Lipid structure

Lipid structure relates to function

Lipids are hydrophobic Due to the hydrocarbons in the fatty acid

“tails” Hydrocarbons are NONPOLAR

When lipids are placed in water, water would rather stick to itself than the lipid.

Lipids and water separate

Saturated vs Unsaturated fats(fatty acid tail comparison)

Saturated fats Each carbon is “holding hands” with the max

number of hydrogen atoms NO double bonds between carbon atoms of the

fatty acid tails Tails are STRAIGHT as a result

Straight tails allow for tight packing Solid at room temperature

Saturated fat – diagram

Saturated fat – diagram and photo

Saturated vs unsaturated fats

Unsaturated fats At least two carbons in the fatty acid chain are

NOT “holding hands” with the maximum number of hydrogens they can

Instead two of the carbons (or more) are DOUBLY covalently bound to each other.

This results in a bending of the fatty acid tail Crooked tails prevent tight packing Liquid at room temperature

Unsaturated fat – diagram and photo

Functions of Fat

Primary function = Energy Storage One gram of fat stores twice the energy of a

gram of polysaccharide Advantageous to animals that have to move

around – unlike plants that can have unlimited bulk without concern for mobility.

Cells that store fat – adipose cells

Functions of Fat

Other functions specifically related to FAT Cushioning Insulation

Phospholipids

Structure Glycerol TWO fatty acid tails ONE phosphate group – “polar head”

Results in a molecule that is BOTH hydrophobic AND hydrophilic Fatty acids are nonpolar and hydrophobic Phosphate group is polar and hydrophilic

Phospholipid diagram

Phospholipid

Hydrophilic/phobic nature causes phospholipids to naturally form membranes when placed in water (aqueous solution)

Steroids

Structure 4 fused carbon rings Various functional groups extend from carbon rings

Functions Roles in cell membrane structure

CHOLESTEROL Maintains cell membrane structure in animals Also is a precursor to other hormones

Cell communication

Steroids - cholesterol

PROTEINS

MANY Important Functions Structural proteins – support

Silk in cocoons/webs; collagen in connective tissue

Storage proteins – storage of amino acids Albumin in egg white; casein in milk

Transport proteins – transport many substances across cell membranes or through the body

hemoglobin Hormonal proteins – coordination of activities

Insulin – controls concentration of sugar in the blood Receptor proteins – receive chemical stimuli and respond Contractile proteins – movement Defensive proteins – protection against disease Enzymatic proteins – speed up chemical reactions!!

Variety of Proteins

Variety within the different types of proteins is staggering! There are many thousands of different types of

enzymes alone – each specifically designed for a particular chemical reaction.

Importance of Shape

Conformation – term for the unique 3-D shape of a protein

Shape is absolutely critical to protein function!!

Protein StructureElements: CHONMonomers = AMINO ACIDS

POLYPEPTIDE is a polymer of amino acids Polypeptide may or may NOT be a fully functional

protein

One or more polypeptides configured in it’s particular shape = a protein

Protein Structure – AMINO ACIDS

An amino acid consists of 5 components 4 components ALWAYS the same

Carbon atom at center Hydrogen Amino group Carboxyl group

R-group The R group is the ONLY component that varies among

amino acids. The R group determines the characteristics of the amino acid

Nonpolar Amino Acids

Polar Amino Acids

Forming a Polypeptide

20 different amino acids exist

Can be assembled in any order

Options for HUGE variety of polypeptides

Forming a Polypeptide

To join two amino acids: Carboxyl group of one must meet the amino

group of another An enzyme will join them via a dehydration

reaction The resulting bond is called a peptide bond Repeating the process over and over creates a

polypeptide

Forming a Polypeptide

Formation of a Polypeptide

The repeated sequence of atoms that remains constant from one amino acid to the next is the polypeptide backbone.

The different appendages attached to the backbone are the R groups The reactivity of the R groups with each other

determines many unique properties of each polypeptide chain

Four Levels of Protein Structure

A functional protein is NOT just a polypeptide chain It is one or MORE polypeptide chains precisely

twisted, folded and coiled into a uniquely shaped molecule

ORDER OF AMINO ACIDS determine the 3-D SHAPESHAPE determines how the protein WORKS.

Four Levels of Protein Structure

Primary structure The ORDER of the

amino acids in the chain

Four Levels of Protein Structure

Secondary Structure Result from the

regularly repeating structure of the backbone

Hydrogen bonds between the constant parts of the amino acids

Results in Alpha helix (spiral) OR Beta pleated sheets

(fan)

Four Levels of Protein Structure

Tertiary Structure Results from interactions

between R-groups Hydrophobic interactions

Also involves van der Waals attractions

Disulfide bridges Hydrogen bonds Results in COMPLEX

folding and twisting of the polypeptide

Four Levels of Protein Structure

Quaternary Structure Results when two or more

polypeptide chains combine to make a functional protein

Example – Hemoglobin is composed of 4 chains.

Overview of Protein Structure - diagram

Different representations of a protein’s conformation - Lysozyme

Environment and Protein Conformation (SHAPE)

Environment plays an important role in shape of a protein

Environment unsuitable, protein can DENATURE – loss of a protein’s SHAPE (conformation)

What can cause a protein to denature?pH pH changes in the environment can interfere with the ability of a

polypeptide chain to hold its shape by interfering with the hydrogen bonds or other types of bonds within the molecule

Temperature Extremes Temperature extremes, especially HOT temperatures, cause an

increase in molecular movement which can cause the protein to lose its shape

Other causes of denaturing Changes in salinity Moving a protein from an aqueous to some organic solution

Hydrophilic regions of the protein that were once on the outside would move inside and vice versa

Denatutration of a Protein - diagram

NUCLEIC ACIDS

Genes give the information for constructing proteins

Genes are made of nucleic acids

Two types of Nucleic Acid

DNA Deoxyribonucleic Acid

RNA Ribonucleic Acid

Nucleic Acid Structure

Nucleic Acids (both RNA and DNA) are polymers

The monomers making up these polymers are nucleotides

Nucleotide structure

3 parts Nitrogenous base Sugar (ribose; which is a 5-carbon [or

penotose]sugar) Phosphate group

Nucleotides – Nitrogenous Bases

There are two families of nitrogenous bases Pyrimidines

Cytosine Thymine uracil

Purines Adenine guanine

Macromolecule Nutrition and Energy

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