Chapter 14: Carbohydrates

Simple Sugars have the formula Cn(H2O)n and were once thought to be “hydrates” of Carbon.

The Carbon cycle.

____________ 6CO2 + 6H2O + energy C6H12O6 + 6O2

__________

Types of Carbohydrates

Monosaccharides – do not hydrolyze into smaller units.

Disaccharides – consist of two mono units joined together – these will hydrolyze (break apart).

Polysaccharides – consist of many mono units and are sometimes called “complex carbohydrates.”

Monosaccharides

Have between three and eight C atoms. Number of C’s determines whether it is a triose

(3), tetrose (4), pentose (5), hexose (6), etc. All have at least two –OH groups and the term

polyhydroxy- is sometimes used. Will have either an aldehyde or ketone group. Aldehyde = aldose and ketone = ketose. Molecules are written with the C backbone in a

vertical direction.

Monosaccharides

Glyceraldehyde Ketose or Aldose? ______________

C

C

H O

H OH

CH2OH

Monosaccharides

Erythulose Ketose or Aldose? ______________

C

C

H OH

CH2OH

O

CH2OH

Monosaccharides and Chirality

Most monosaccharides have several chiral C’s. If the lowest chiral C has the OH group on the

left, then it is called the L isomer. If it is on the right, then it is called the D isomer.

Hint: C’s with double to the O are not chiral and the -CH2OH groups are also not chiral.

Chiral Carbons

How many chiral carbons?

C

C

H O

H OH

CH2OH

C

C

H OH

CH2OH

O

CH2OH

Glucose

How many chiral carbons? ___

Is this the D isomer?____

C

C

HHO

H OH

C

CH2OH

OHH

C

C

OHH

H O

Fructose

How many chiral carbons? ___

Is this the D isomer? ____

CH2OH C == O

HO — C — H

H — C — OH

H — C — OH

CH2OH

Some Important MonoSaccharides Glucose, aka dextrose – the most important one. D-glucose (p. 486) is oxidized in the body to produce

energy. L-glucose (p. 488) cannot be oxidized. D-galactose (p. 489) is an aldohexose and is obtained as

from disaccharides and is a close cousin of glucose. D-fructose (p. 489) is a ketohexose and is twice as sweet

as sucrose. This is found in fruit juices and honey.

Cyclic Structures

The structures of the mono units are easy to show using the vertical, open chain system.

However, they actually exist as five and six-membered rings.

See also p. 492-3

Oxidation of Monosaccharides

All aldoses like glucose and galactose can be easily oxidized to yield carboxylic acids.

These are often referred to as “reducing sugars.” Benedict’s reagent (Cu+2) is used to test for

glucose in the urine. The extent of a color change indicates how much glucose is present in the urine.

Disaccharides

Composed of two mono units. Some common ones are:

Sucrose (Cane sugar) = Glucose + Fructose Lactose (Milk sugar) = glucose + galactose Maltose (Malt sugar) = glucose + glucose

In the presence of water and an acid catalyst, these linked molecules will split apart back into their mono units.

Sweetness Scale

All sugars and sugar substitutes vary in sweetness.

Sucrose is assigned a sweetness of 100.

Some artificial sweeteners have a caloric value, but because they are many, many times sweeter than regular sugar they are used in much smaller quantities.

Polysaccharides

This is essentially a polymer of glucose units (usually). Plant Starch, like that found in potatoes and rice, exists

in two forms: Amylose and Amylopectin. Amylose is a long,continuous chain of glucose molecules.

Typically has 250 – 4000 units. Amylopectin is a branched chain of glucose molecules.

Branches are about every 25 units. See p. 487.

Animal Starch is also called ___________. This is essentially a branched chain as well. Branches are about every 10 – 15 units.

Amylose and Amylopectin

Polysaccharides

____________, found in cell walls of plants and animals, is also a long chain of glucose units much like amylose.

The linkage between each unit is different and is resistant to hydrolysis.

Human’s do not possess the enzymes to break this material down for energy as some animals do.

We often refer to this material in our diet as “fiber.”

Ch. 15 Lipids

Lipids are a family of compounds that are __________ in water (ie. Non-polar).

Classes of Lipids: Waxes = fatty acid and long chain alcohol (ester) Fats & Oils = glycerol + three fatty acids Phospholipids = glycerol + 2 fatty acids + phosphate + an

amino alcohol Sphingolipids = fatty acid + sphingosine + phosphate + an

amino alcohol Glycolipids = fatty acid + glycerol or sphingosine + one

monosaccharide. Steroids = a fused ring structure of three cyclohexanes and one

cyclopentane.

Fatty Acids

Long chain carboxylic acids. 12 – 18 Carbon’s are the most common. Stearic acid is most often found in animal fat.

CH3CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2COOH

And it can also be represented like this:

C

O

OH

Fatty Acids

Can be saturated – all C-C single bonds. Can be mono-unsaturated – one C-C double bond.

Ex) Oleic Acid found in olives and corn. CH3(CH2)7CH=CH(CH2)7COOH

Can be poly-unsaturated – more than one C-C double bond. Ex) Linoleic Acid found in soybeans and sunflowers. CH3(CH2)4CH=CHCH2CH=CH(CH2)4COOH

In the Unsaturated acids, the cis isomer is usually found. Common ones shown on p. 499.

Physical Properties

The repeating zig-zag shape of saturated fatty acids allows them to fit close together leading to strong attractions. As a result, these are solids at room temperature.

The unsaturated fatty acids do not stack together because of the double bonds. As a result, these are liquids at room temperature.

Physical Properties

C

OH

O

C

OH

O

C

OH

O

Physical Properties

C

O

OH

C

O

OH

C

O

OH

Waxes

A wax is an ester of a fatty acid plus a long chain alcohol.

The reaction for Beeswax is:

CH3(CH2)14C

O

OH + (CH2)29CH3HO CH3(CH2)14 C

O

O (CH2)29CH3 + H2O

Fats and Oils

Fats and oils are the most common lipids. Often called triglycerides because they are a tri-

ester of glycerol and three fatty acids. Tristearin consists of three stearic acid molecules

reacting with glycerol. A Fat is a triglyceride that is ______ at room

temeprature. Source = animals. An Oil is a triglyceride that is usually a ______

at room temperature. Source = plants.

Making a Fat

In Tri-Stearin, the “R” groups would be –(CH2)16CH3 Three water molecules are also produced.

Reactions of Fats and Oils

Unsaturated oils can be converted into saturated ones by Hydrogenation. This reaction was shown for the alkenes.

Oxidation of Oils occurs with exposure to O2. This occurs more easily at the C-C double bonds. Thus, vegetable oils must have anti-oxidants added to retard this process.

HC CH + H2 H2C CH2R R RR

Other Lipids

Phospholipids are found in the structure of cell membranes. They regulate what passes into and out of cells.

Sphingolipids are found in the brain and nerve tissues. They increase the speed of the nerve impulses as well

as form a protective coating over the nerves. Glycolipids are also abundant in the brain and

nerve cells.

Steroids and Cholesterol

Steroids are any compounds containing the steroid nucleus.

Cholesterol is the most important and abundant steroid in the body.

You cannot exist with out this substance!

Cholesterol

HO

CH3

CH3

H3C

CH3

CH3

The Importance of Cholesterol

All hormones have as their base structure the steroid nucleus (pictured earlier).

Thus, the sex hormones and the adrenocortical hormones depend on cholesterol for their synthesis.

See molecules on p. 538 and you will see the cholesterol structure contained in these molecules.

Estrogen and Testosterone

HO

CH3OH

O

CH3OH

CH3

Estrogen Testosterone

Ch. 16 Amino Acids and Proteins

The human body produces over _________ different proteins.

These are grouped together by their function. Some of these are (Table 16.1): Structural – provide structural components. Examples are

Collagen found in tendons and cartilage and Keratin found in the hair and skin.

Contractile – provides for the movement of muscles. Myosin and Actin contract the muscle fibers.

Transport – carries essential substances through the body. Hemoglobin transports oxygen to the cells.

Storage – provides for storage of nutrients. Casein stores protein in milk and Ferritin stores iron in the spleen and liver.

Hormone – helps regulate body metabolism. Insulin regulates blood sugar levels.

Enzyme – catalyze biochemical reactions. Sucrase catalyzes the hydrolysis of sucrose.

Protection – recognition and destruction of foreign substances. Immunoglobulins stimulate the immune response.

Types of Proteins - continued

The Amino Acids

Are the building blocks of all proteins.

________ versions of these.

All contain the carboxylic acid and amine functional groups.

Center C is called the ______ Carbon.

CN

R

C

H

H

HOH

O

The Amino Acids

The R group is different for all 20 amino acids.

The R group may be non-polar like an H or a –CH3 or polar or acidic or basic.

The alpha Carbon is also chiral (except in Glycine).

All 20 are found on p. 556.

CN

R

C

H

H

HOH

O

Amino Acids

C

CH3

H

CH2N

O

OH C

CH2

H

CH2N

O

OH

OH

• Alanine, on the left, is a non-polar amino acid.• Serine, on the right, is a polar amino acid.

The Amino Acids

Because amino acids have both an acidic end and a basic end, they may auto-ionize to form what is called a zwitterion – the H+ is transferred from one end to the other.

CN

R

C

H

H

HOH

O

CN

R

C

H

OH

H

H

+

O_

The Peptide Bond

Amino acids link together by the reaction of a carboxylic acid on one with the amine of another.

This is a condensation reaction similar to that of the polyamides.

The linkage between the two is called a peptide bond.

Reaction between Glycine and Alanine

C

H

H

H2N C

O

OH + C

CH3

N

H

COOH

H

HHeat

CH2N

H

H

C

O

N

H

C

CH3

H

COOH + H2O

Primary Structure

Chains of 3 – 50 amino acids are called polypeptides. When more than 50 amino acids are joined, we usually

call it a protein. For a polypeptide of only 5 amino acids, the number of

combinations possible is staggering (sort of like playing the Lottery!).

The specific sequence of amino acids in a protein is called the primary structure and is determined by our ____ code.

Our ___ codes for only a limited number of specific sequences for making proteins.

Secondary Structure

Secondary Structure refers to how the amino acids next to or near each other are arranged in space. Hydrogen bonding (HB) forces within three or four nearby amino acids are the most common type of interaction.

The three most common types of secondary structures (p.542-3) are: Alpha Helix - which is a corkscrew shape of the chain that

results from HB between every fourth amino acid. All of the R groups then are pointed outward.

Beta-Pleated Sheet – rows of amino acids are held flat with HB keeping them rigid.

Triple Helix – is three peptide chains woven together like a braid. HB is also a powerful force that holds this together.

Alpha Helix Structure

Two models of the alpha helix:

Tertiary Structure

Tertiary Structure is the overall 3D shape of the protein. This also involves Hydrogen Bonding as well as cross-linking across much greater distances.

Thus, you may get a hydrogen bond or cross-link between one amino acid on the peptide and another one that is hundreds of amino acids away.

Tertiary Structure

A cross-link is formed by the oxidation of the thiol group found in the amino acid Cysteine.

C

H

CH2N

O

OH

CH2

SH

Tertiary Structure

The formation of the disulfide across a great distance in the chain would like this.

People with curly hair have many of these cross linkages.

R C SH +

H

H

CHS

H

H

R

[O]CR

H

H

S S C

H

H

R

Tertiary Structure

Two types of tertiary structures: Globular proteins, like hemoglobin and insulin,

have a very compact and round shape. The non-polar R groups point inward and the polar R groups point outward and this makes these proteins soluble in water.

Fibrous proteins, like keratin (hair, skin), consist of long, thin, fibrous shapes.

Albumin

A protein made in the liver.

It is found in large concentrations in blood serum.

The pink portions are alpha-helix and the yellow portions are beta-pleated sheet sections.

Quaternary Structure

Some proteins consist of two or more sub-units (tertiary structures).

The overall protein structure is then referred to a quaternary structure.

Hemoglobin consists of four heme units – each unit being able to transport one O2 molecule.

Overview of Protein Structures

Overview of Protein Structures