Biological MoleculesBio

Do Now

Spend the next 10 minutes studying for the quiz. The quiz will cover everything since our last exam:

1. Chemistry review2. Water3. Mono/disaccharides

Silently and independently:

Put away everything except a pencil and a cover sheet.Once done Turn it in on my desk Pick up the handouts Tape the orange sheet in your LAB notebook

• Lab report: due Thursday NEXT TUESDAY• Lab makeups on Thursday• Reminder: no tutoring after school on

Tuesdays• Pass back papers do NOT leave these in my

room please

Today’s Announcements

Can you…Draw on the diagram where a glycosidic bond will form and complete the diagram to show the disaccharide that will be produced.

Warm-up

Can you…Draw on the diagram where a glycosidic bond will form and complete the diagram to show the disaccharide that will be produced.

Review of Mono/disaccharides

The many forms of glucose: Straight chain(linear) form

(least common/stable)

α-Ring formAlpha-ring(“OH” group is below the ring)

β-Ring formBeta-ring(“OH” group is above the ring)

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Cyclic Structure of Glucose: RotationStraight open-chain glucose is so reactive that

almost all molecules quickly rearrange their bonds to form two new structures. These structures are six-membered rings like those below. The beta version is more stable.

How are the two monosaccharides

joined?Glycosidic BondFormed by

condensation reactions

Recall: what molecule is released when the glycosidic bond forms?

6C12H6O

12C22H11O

6C12H6O

H2O

How are the two monosaccharides

joined?Glycosidic Bonds

+H2O

REDUCING SUGARS

What is a “reducing sugar”? How do we test for it?

Reducing sugars• Can cause reduction chemical

reactions• Benedict’s Test: when a reducing sugar is

added to the reagent (copper sulfate dissolved in a base), it reduces the reagent and makes a red-brown precipitate

• Include the following:• ALL monosaccharides• SOME disaccharides

• E.g. Maltose

SUCROSE is an important example of a disaccharide that is NOT a reducing sugar

Which of the following would NOT reduce Benedict’s Reagent?

D.E.

A. C.B. Ribose

Simple Sugar Practice Problems

8 minutes- silent, independent work time8 minutes- group work time

4 minutes- class review

PolysaccharidesCarbohydrates which are made from many linked monosaccharide monomers form long chain-like molecules called polymers.

- made from glucose

monomers

polysaccharides cellulose

glycogen

starch

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There are three main types of naturally occurring polysaccharides. They are cellulose, glycogen, and starch that are of major importance.

Polysaccharides Derived from Glucose

What does cellulose do?(Hint: recall cell structures)

PolysaccharidesFunctions: storage, structure, recognition

• Starch and glycogen are storage molecules • Chitin and cellulose are structural

molecules • Cell surface polysaccharides are

recognition molecules

Starch A plant storage polysaccharide • Two forms: amylose and amylopectin

• Most starch is 10-30% amylose and 70-90% amylopectin

• Branches in amylopectin every 12-30 residues

• Amylose has αβ(1,4) links and one reducing end

Starch• Amylose: compact, energetic

spirals of α-glucose molecules• Amylopectin: compact,

branched, energetic shapes of α-glucose molecules

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The unbranched structure of amylose.

Polysaccharides Derived from Glucose

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Polysaccharides Derived from Glucose

The branched structure of amylopectin.

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An important reaction during digestion is the hydrolysis of starchy foods as shown below.

Starch is not soluble in cold water due to its large size and will form a colloidal dispersion in hot water.

Starch solutions form a blue-black color in the presence of free iodine.

Polysaccharides Derived from Glucose

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Glycogen is a carbohydrate polymer that is stored in the liver and muscle tissues in animals. It is the energy-storage carbohydrate in animals.

Glycogen has a structure similar to amylopectin (starch) except that it is more highly branched with the a-1,6-glycosidic linkages occurring more frequently along the polymer chain.

Like amylopectin, glycogen gives a red-violet color with iodine

Polysaccharides Derived from Glucose

Carbohydrates: Summary• Polysaccharides

– Storage: • Plants: storage • Animals: glycogen

• Polysaccharides Structural: Cellulose~ most abundant

organic compound; Chitin~ exoskeletons; cell walls of fungi; surgical thread

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Cellulose, like starch and glycogen, is a glucose-based polymer.

The glucose units in cellulose are joined by -1,4-glycosidic linkages instead of a-1,4-glycosidic linkages.

There is extensive hydrogen bonding in cellulose.

Therefore, it’s a long strong chain of -Glucose

Polysaccharides Derived from Glucose

Demonstration Time

Form human glucose polymers for:

• Amylose• Amylopectin

• Cellulose

Cellulose• Most abundant organic molecule.

• It’s very slow to decompose.• Made of β glucose units.

• Every other β glucose is rotated through 180° - this makes the chains straight, not coiled.

• Hydrogen bonding between monosaccharide molecules in the chain gives strength.

• Hydrogen bonding between cellulose molecules cause bundles called microfibrils to develop. These are held together in fibres.

• 20-40% of the plant cell wall.• A cell wall will have several layers of fibres running in different

directions - gives great strength almost equal to steel.• Provides support in plants and stops plant cells bursting.• Freely permeable to water and solutes.

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Figure 27.9 Two representations of cellulose. In the three-dimensional model note the hydrogen bonding that links the extended cellulose polymers to form cellulose fibers.

Three-dimensional model of cellulose

Which picture shows cellulose?

How are the polysaccharides formed?

Hint: Same type of reaction that forms a disaccharide from monosaccharies

Condensation reactions

Hydrolysis

Which type of reaction (condensation or hydrolysis) does this show?

Carb overload?Let’s practice this all some

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Review handoutWhen should this be due?

Sell that Saccharide Assignment

Options for saccharide

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Glucose is the most important of the monosaccharides. It is an aldohexose and is found in the free state in plant and animal tissue. Glucose is also known as dextrose and grape sugar.

Glucose is a component of the disaccharides sucrose, maltose, and lactose and is the monomer in the polysaccharides amylose, amylopectin, cellulose, and glycogen.

Glucose is the key sugar of the body and is carried by the bloodstream to all body parts.

Sell that Saccharide Example