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Macromolecules: Carbohydrates, Lipids, Proteins and Nucleic Acids PowerPoint PPT Presentation


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Macromolecules: Carbohydrates, Lipids, Proteins and Nucleic Acids . Objectives:. Describe the chemical composition and general structure of carbohydrates. - PowerPoint PPT Presentation

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Macromolecules: Carbohydrates, Lipids, Proteins and Nucleic Acids

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Macromolecules carbohydrates lipids proteins and nucleic acids l.jpg

Macromolecules: Carbohydrates, Lipids, Proteins and Nucleic Acids


Objectives l.jpg

Objectives:

  • Describe the chemical composition and general structure of carbohydrates.

  • Describe three classes of carbohydrates, how they are synthesized, specific examples of each (name, empirical and structural formulas) and their functions.

  • Define and describe examples of monosaccharide isomers

  • Describe the chemical composition and structures of lipids

  • Describe the formation of a triglyceride

  • Compare and contrast saturated and unsaturated triglycerides

  • List and describe examples of various forms of lipids and their functions in living things.

  • Describe the chemical composition of proteins

  • Describe the general structure of an amino acid and the variation of amino acids (how many, how are they similar, how they are different)

  • Describe the formation of peptide bonds and how polypeptide chains are formed.

  • Describe the 4 levels of protein structure.

  • Describe the major functions of proteins.

  • Describe the function, structure, and formation of nucleic acids.


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Carbohydrates

  • All carbohydrates are composed of carbon, hydrogen, and oxygen in a 1:2:1 empirical ratio.

  • The general empirical formula for a carbohydrate is CH2O.

    If a carbohydrate has 5 carbons atoms, what would be its empirical formula?

    If a carbohydrate has 12 hydrogen atoms present, what would be its empirical formula?

  • Most carbohydrates end with the suffix -ose

C5H10O5

C6H12O6


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Functions of Carbohydrates

  • Provide energy source: A fuel source when catabolized during cellular respiration. Energy is stored in the chemical bonds within the molecule and released during cellular respiration. Usually simple sugars.

  • Provide energy storage: Plants store energy in a complex carbohydrate form called starch (amylose). Animals store energy in a complex carbohydrate in their muscle tissue and liver in the called glycogen.

  • Structural Building Material: Plants build their cell walls of a complex carbohydrate material called cellulose. Animals such as arthropods build their exoskeletons of a complex carbohydrate called chitin. Chitin is also found in the cell walls of Fungi.


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Classes of Carbohydrates

  • There are three major classes of carbohydrates:

    1. Monosaccharides (simple sugars) These are the monomers or building blocks for all other classes of carbohydrates. Examples: glucose, fructose, galactose, and ribose.

    2. Disaccharides are produced by joining two simple sugars by dehydration synthesis forming a covalent bond between them. Examples: sucrose (table sugar), maltose, lactose

    3. Polysaccharides (complex carbohydrates) are produced by joining many monosaccharides together by many dehydration synthesis reactions forming a polymer molecule. Examples: amylose, glycogen, cellulose, and chitin


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Monosaccharides (Simple sugars)

  • They may exist in a linear molecule or in ring forms.

  • They are classified according to the number of carbon atoms in their molecule.

    5 carbons are called pentoses ex. Ribose

    6 carbons are called hexoses ex. Glucose

  • Many forms exists as isomers. Isomers are molecules which have the same empirical formula (recipe) but have different structures (shapes) due to arrangement of the atoms in the molecule. This also gives them different properties. Glucose and fructose both have the empirical formula C6H12O6, but they have different structural formulas or shapes.

  • MONOSACCHARIDES ARE THE BUILDING BLOCKS FOR ALL OTHER CARBOHYDRATES!


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H

H—C—OH

O H

CC

OH OH H

CC

H OH

H—C—OH

H

H

H—C—OH

CO

H H H

CC

OH H

OH CCOH

H OH

Monosaccharide Isomers

FRUCTOSE

α- GLUCOSE

What is the empirical formula for these molecules?

C6H12O6


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Disaccharide Formation and Structure

  • Disaccharides are formed when two monosaccharides are joined by dehydration synthesis reaction.


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CH2OH

CH2OH

CH2OH

CH2OH

H O H

H O H

H O H

H O H

O

OH

OH

OH OH

HO OH

Disaccharide Formation and Structure

H20

+

MALTOSE

α- GLUCOSE

α- GLUCOSE


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Disaccharide Structure

Sucrose Maltose


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Polysaccharide Structure and Formation

  • Polysaccharides are chains of monosaccharides that have been joined by many dehydration synthesis reactions.

  • The function of the polysaccharide depends on what type of isomer of glucose the polysaccharide is made. This determines how the glucose molecules bond together (linkage) and whether they can be used for energy storage or structural molecules.


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Alpha and Beta Glucose and Their 1,4 Linkages

Alpha and beta glucose are

structural isomers. They differ

only in the location of the

hydrogen and hydroxl group

location on carbon 1.

Alpha linkage can be broken by

enzymes present in plants and

animals. In other words, it can

be metabolized. (energy storage)

Beta linkage can not be broken

by enzymes present in plants

and animal, therefore it can not

be metabolized. (structural)


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Storage Polysaccharides

Starch and glycogen both have alpha 1,4 linkage and form helical chains that are often highly branched.

The diagram to the left show starch or amylose granules in a plastid of a plant cell.

The diagram to the left shows glycogen granules in a liver section of an animal. Glycogen is usually more highly branched than amylose.


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Structural Polysaccharides

  • Cellulose is the plant structural carbohydrate and has beta 1,4 linkage. Cellulose is the primary component of the plants primary or outermost cell wall.


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Have You Had Your Fiber Today?

  • Because cellulose has beta 1,4 linkage all animals lack the enzymes necessary to digest this material. In our case it simply passes through our gut and out of the body. We call it fiber or roughage. Animals such as termites and cows rely on simple, symbiotic, unicellular organisms such as protozoa or bacteria to carryout the job of digestion for them! In return the tiny organisms live in an ideal environment with a bountiful food supply.


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Structural Polysaccharides

  • Chitin is the “plastic-like” material that composes the exoskeletons of arthropods (insects, arachnids, and crustaceans). Most fungi (mushrooms) have chitin present within their cell walls.

Above is a structural monomer of

chitin.


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Lipids

  • Lipids are complex molecules composed of carbon, hydrogen, and oxygen.

  • Most lipids are non-polar and are hydrophobic because they contain hydrocarbon chains.

  • If there are double or triple bonds in the hydrocarbon chain the lipids are said to be “unsaturated”


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Lipid Functions

  • Energy storage: Fats and oils.

  • Waterproofing: Waxes and oils

  • Insulation: Fat layers (blubber)

  • Cushioning: Fat layers (soles of your feet)

  • Regulating metabolic processes: Steroids

  • Building component of cell membranes:

    Phospholipids


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Lipid structure (Triglyceride)

  • A triglyceride is composed of an alcohol called glycerol covalently bonded to three fatty acid molecules by dehydration synthesis reactions. This process forms three ester groups between the alcohol and one with each fatty acid chain.

Is this a saturated or unsaturated

Fat? Why or Why not?

It is saturated because there are no double bonds between carbon atoms in the

fatty acid hydrocarbon chains.


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Triglyceride formation

O H H H H H

-C-C-C-C-C-C-H

H H H H H

O H H H H H

-C-C-C-C-C-C-H

H H H H H

O H H H H H

HO-C-C-C-C-C-C-H

H H H H H

O H H H H H

HO-C-C-C-C-C-C-H

H H H H H

O H H H H H

HO-C-C-C-C-C-C-H

H H H H H

O H H H H H

-C-C-C-C-C-C-H

H H H H H

H

H-C—OH

H-C—OH

H-C—OH

H

H

H-C—O

H-C—O

H-C—O

H

H20

H20

H20

3 H20

GLYCEROL

FATTY ACIDS

TRIGLYCERIDE

What type of reaction forms a triglyceride?

Dehydration Synthesis


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Saturated vs. Unsaturated Fats

When double bonds form in hydrocarbon chains it causes them to bend. In unsaturated fats this prevents the molecules from being able to “stack” or “pack” themselves tightly, thus they remain in a liquid state at room temperature such as oils. If the hydrocarbon chains are saturated, the chains are straight and pack themselves close together forming a solid at room temperature (animal fat, butter, tallow, lard).


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Steroids

Cholesterol

  • Steroids are cyclic hydrocarbons usually composed of four rings.

  • They are involved with regulating metabolic processes in the body because many forms of them are hormones.

  • Testosterone, estrogen, and progesterone are all examples of steroid hormones.

  • Cholesterol is the most common steroid! It is the building block for other steroid hormones and also functions in cell membrane structure.


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Phospholipids

Phospholipids are a special class of lipids composed of a phosphate group, glycerol

molecule, and two fatty acid chains. The phosphate region of the molecule is polar because it is negativley charged. This makes it attracted to water or hydrophilic because of waters bipolar nature. The fatty acid chain region is composed of hydrocarbon chains which are very non-polar, therefore this end is hydrophobic or repels water.


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Phospholipid Structure


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Phospholipid Behavior

Because of their bipolar nature,when placed in water phospholipids orient themselves in small spheres or “bubbles” with their nonpolar (hydrophobic) regions oriented away from water and their polar (hydrophilic) regions exposed to water. These structure are called micelles and are similar in structure the cell membrane which is composed in part of a phospholipid bilayer.


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Proteins

  • Proteins are composed primarily of carbon, hydrogen, nitrogen,and oxygen. However, some contain sulfur.

  • They are all composed of structural monomers called amino acids.

  • Their differences from organism to organism is due to differences in the DNA which contains the instructions for their formation. Ex. Eye color, Blood type


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Protein Functions

  • Structure: Building structural components of organisms

    (collagen, elastin, keratin, microtubules, microfilaments)

  • Regulation of metabolic processes: Hormones (insulin)

  • Carrying out of metabolic processes: Enzymes

  • Membrane component: Carrier proteins, Protein pumps, Transport of materials through membrane phospholipid layers

  • Self and non-self recognition: Major histocompatibility complexes (Tissue rejection, immune responses).

  • Membrane receptors: Hormone receptors and neurotransmitter receptors.


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Amino Acids: Structural Monomers

Amino acids derive their name due to the presence of an amine group and a carboxylic group as part of their composition. They have a central carbon with the amine group, a carboxyl group, a hydrogen, and a variable group (R group) attached to it. The variable group is what is different from amino acid to amino acid and it is what give the amino acid its identity. There are twenty different variable groups, therefore there are twenty different amino acids.


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Amino Acid Variety


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Peptide Bond, Dipeptide, and Polypeptide Formation

A peptide bond is the bond that is created when two amino acids are covalently bonded together. The carboxyl group of the first is bonded to the amine group of the second. This is carried out by a dehydration synthesis reaction with the loss of a water molecule. This forms a dipeptide.


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H H O

N C C –OH

H R1

H H O

N C C –OH

H R2

H H O

N C C–

H R1

+

H O

N C C –OH

H R2

Peptide Bond, Dipeptide, and Polypeptide Formation

H2O

This is called a dipeptide. If the process is

repeated many

times a polypeptide is formed.

The peptide bond

is created between

the carboxyl carbon

of the first amino acid

and the amine group

of the second amino

acid.

Peptide Bond


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Levels of Protein Structure

Proteins are very complex molecules and their shape or structure determines their function. Most proteins have 4 levels of structure. They are:

a. Primary Level

b. Secondary Level

c. Tertiary Level

d. Quaternary Level

If any level of structure is changed it can create faulty or nonfunctioning proteins!


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Levels of Protein Structure

The Primary Level is determined by the number of amino acids, the type of amino acids, and the sequence of the amino acids in the polypeptide chain.


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Levels of Protein Structure

The Secondary Level is due to interactions between amino acids in the chain, usually due to hydrogen bonding between oxygen and hydrogen atoms in different amino acids. Two general forms are taken. Alpha helix, a spiral structure, common in globular proteins, or a Beta pleated sheet structure, common in structural proteins.


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Levels of Protein Structure

The Tertiary Level is due to the “folding over” of the alpha helical or beta pleated sheet structure on itself. This configuration is due again to hydrogen bonding, hydrophobic interactions, ionic bonding interactions, and the interaction of sulfur groups on the variable groups of some amino acids forming weak interactions called disulfide bridges.


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Levels of Protein Structure

The Quaternary Level of structure is due to the interactions of more than one polypeptide chain to form the complete, functional protein. Hemoglobin and antibodies exhibit this level of structure.


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Levels of Protein Structure


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Example of Modification in Levels of Protein Structure

Sickle-cell anemia is due to a change in protein structure at the primary level. Once the change is made at the primary level it has an effect on all subsequent levels. Resulting the formation or irregular hemoglobin protein that cause the molecule to take on an irregular form which in turns affects its normal function and the shape of the erythrocytes (red blood cells).


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Nucleic Acids

  • Composed of carbon, hydrogen, oxygen, nitrogen, and phosphorus

  • Carriers of the genetic code (recipe book for proteins)

  • Two types: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid)

  • Molecule responsible for heredity


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Nucleotide Monomers

Nucleic acids are composed of many monomers linked together by dehydration synthesis. These monomers are callednucleotides (nucleosides). These monomers are composed of a monosaccharide (deoxyribose in DNA or ribose RNA), a phosphate group, and a nitrogenous base. The nitrogenous bases found in DNA are adenine A, Thymine T, Guanine G, and Cytosine C. The nitrogenous bases found in RNA are Adenine A, Guanine G, Cytosine C, and Uracil U, which replaces thymine.


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Nucleotide Structure


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DNA Structure

The structure of DNA was discovered by an American scientist (James Watson) and a British scientist (Francis Crick) based on the work of Rosalind Franklin and Maurice Wilkins. In 1962 Watson and Crick received the Nobel Prize for their work. Wilkin later received a Nobel Prize for work relating to his contribution. Rosalind Franklin however, never received a Nobel Prize because she died of cancer before she was publicly recognized for her contributions to this effort.


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The Double Alpha Helix of DNA

DNA is a double stranded, alpha helical molecule. Each strand is composed of nucleotide covalently bonded between their phosphate groups and the deoxyribose sugar components in a 5,3 linkage between the sugars and phosphates. The nitrogenous bases point outward from the linear alternating sugar phosphate backbone.

5’

3’


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The Double Alpha Helix of DNA

When two strands of DNA join to form the alpha helix, it is due to hydrogen bonding between the complimentary purine and pyrimidine bases on each complimentary strand. Adenine forms hydrogen bonds with Thymine and Guanine forms hydrogen bonds with Cytosine. This is called Complimentary Base Pairing.


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The Double Alpha Helix of DNA

The complimentary strands run in opposite directions or anti-parallel to each other.


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The Double Alpha Helix of DNA

The strands begin to spiral and due to hydrogen bonding takes on the double alpha helix form.


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DNA bases (A,T,G,C)

Deoxyribose sugar

Original information for making proteins

One form or type

Found primarily in the nucleus forms chromosomes during cell division

Large molecule (double stranded)

RNA bases (A,U,G,C)

Ribose sugar

Working copy for making proteins

Variety of forms, m-RNA, t-RNA, r-RNA

Found in nucleus and through the cell

Smaller molecules (single stranded)

Comparing and Contrasting DNA and RNA