Molecules of Life

Polymers Are Built of Monomers Organic molecules are formed by living organisms have a carbon-based core the core has attached groups of atoms called functional groups the functional groups confer specific chemical properties on the organic molecules

Polymers Are Built of Monomers The building materials of the body are known as macromolecules because they can be very large There are four types of macromolecules: Proteins Nucleic acids Carbohydrates Lipids Large macromolecules are actually assembled from many similar small components, called monomers the assembled chain of monomers is known as a polymer

Macromolecule Formation There are 4 major categories of organic molecules in living organisms: Carbohydrates Lipids Protein Nucleic acids

Macromolecules A macromolecule is built upon repeating subunits called polymers. Macromolecules are large and complex. An organic molecule is based on long chains of carbon with functional groups on the ends that give the molecule its unique chemical properties.

Macromolecules All four macromolecules consist of a covalent bond between two subunits..a hydroxyl group is removed from one end and a hydrogen group from the other end. This process is called dehydration. Dehydration requires the action of an enzyme to facilitate chemical binding. Adding of water to the polymer too break them into subunits is called hydrolysis.

Carbohydrates Carbohydrates are energy sources and are made of polymers of simple carbohydrates. Simple carbohydrates include monosaccharides and disaccharides. Complex carbohydrates are polysaccharides formed from glucose. Component of plant cell walls, outer skeletons of insects. Ex.: chitin, cellulose, glycogen, starch.

Carbohydrates Carbohydrates are monomers that make up the structural framework of cells and play a critical role in energy storage a carbohydrate is any molecule that contains the elements C, H, and O in a 1:2:1 ratio the sizes of carbohydrates varies simple carbohydrates – consist of one or two monomers complex carbohydrates – are long polymers

Carbohydrates Simple carbohydrates are small monosaccharides consist of only one monomer subunit an example is the sugar glucose (C6H12O6) disaccharides consist of two monosaccharides an example is the sugar sucrose, which is formed by joining together two monosaccharides, glucose and fructose

Formation of sucrose

Carbohydrates Complex carbohydrates are long polymer chains because they contain many C-H bonds, these carbohydrates are good for storing energy these bond types are the ones most often broken by organisms to obtain energy the long chains are called polysaccharides

Carbohydrates Plants and animals store energy in polysaccharide chains formed from glucose plants form starch animals form glycogen Some polysaccharides are structural and resistant to digestion by enzymes plants form cellulose cell walls some animals form chitin for exoskeletons

Carbohydrates and their function

Lipids Fats and all other biological materials that are not soluble in water, but are soluble in oil are lipids. Used for long term energy storage. Fats: Triglycerols are made of glycerol and three fatty acids. Fatty acids may be saturated or unsaturated with hydrogen along the carbon chain.

Lipids Fats are used for: Energy storage; Components of cell membranes (phospholipids); Message transmission (steroids); Pigmentation.

Lipids Fatty acids have different chemical properties due to the number of hydrogens that are attached to the non-carboxyl carbons if the maximum number of hydrogens are attached, then the fat is said to be saturated if there are fewer than the maximum attached, then the fat is said to be unsaturated

Saturated and unsaturated fats

Proteins Proteins may serve as enzymes, play a structural role, and act as chemical messengers. They are polypeptides made up of amino acids joined by peptide bonds. Act as catalysts.

The formation of a peptide bond

Proteins Protein structure: The sequence of amino acids within the protein is called the primary structure. Any folding of the primary chain structure is called the secondary structure. Globular shapes are the tertiary structure of a protein. When more than one polypeptide chain composes the protein, it has quaternary structure. The shape of a protein can be denatured (poor function results).

Proteins There are four general levels of protein structure Primary Secondary Tertiary Quaternary

Proteins Primary structure – the sequence of amino acids in the polypeptide chain This determines all other levels of protein structure Figure 4.7 Levels of protein structure: primary structure

Proteins Secondary structure forms because regions of the polypeptide that are non-polar are forced together; hydrogen bonds can form between different parts of the chain The folded structure may resemble coils, helices, or sheets Figure 4.7 Levels of protein structure: secondary structure

Proteins Tertiary structure – the final 3-D shape of the protein The final twists and folds that lead to this shape are the result of polarity differences in regions of the polypeptide Insert Figure 4.7 from TLW 6e

Proteins Quaternary structure – the spatial arrangement of proteins comprised of more than one polypeptide chain Figure 4.7 Levels of protein structure: quaternary structure

Protein The shape of a protein affects its function changes to the environment of the protein may cause it to unfold or denature increased temperature or lower pH affects hydrogen bonding, which is involved in the folding process a denatured protein is inactive

Nucleic Acids Nucleic acids (polynucleotides) store information for cells. DNA (Deoxyribonucleic acid) exists as a double helix of polynucleotides, using base pairing within the helix. Base pairing dependent upon hydrogen bonding. DNA encodes genetic materials and ribonucleic acid (RNA) is involved in protein synthesis.

The Double Helix The reason for DNA to assume its double helix is because only two base pairs are possible: Adenine-Thymine and Guanine-Cytosine. The advantage of the double helix is that it contains two copies of the information—one the mirror image of the other.

The DNA double helix

The Structure of DNA All life on earth uses a chemical called DNA to carry its genetic code or blueprint. In this lesson we be examining the structure of this unique molecule. {Point out the alligator’s eyes in the first picture.} By the way, can you make out what this is? *************************************************************** [The goal of this presentation is to introduce high school biology students to the chemical structure of DNA. It is meant to be presented in the classroom while accompanying the teacher’s lecture, under the control of the teacher.] Mr. Coleman Biology

DNA DNA is often called the blueprint of life. In simple terms, DNA contains the instructions for making proteins within the cell. Why is DNA called the blueprint of life?

Why do we study DNA? We study DNA for many reasons, e.g., its central importance to all life on Earth, medical benefits such as cures for diseases, better food crops. About better food crops, this area is controversial. There is a Dr. Charles Arntzen who is working on bioengineering foods with vaccines in them. People in poor countries could be immunized against diseases just by eating a banana, for instance.

Chromosomes and DNA Our genes are on our chromosomes. Chromosomes are made up of a chemical called DNA. {Ask students where the chromosomes are in this picture. Or ask them where the DNA is. Remind them that the mitochondria also have DNA.}

The Shape of the Molecule DNA is a very long polymer. The basic shape is like a twisted ladder or zipper. This is called a double helix. {Show students a model of the double helix. Explain what a spiral is and a helix is.}

The Double Helix Molecule The DNA double helix has two strands twisted together. (In the rest of this unit we will look at the structure of one strand.) We will take apart the DNA molecule to see how it is put together. First, we will look at one strand.

One Strand of DNA The backbone of the molecule is alternating phosphate and deoxyribose, a sugar, parts. The teeth are nitrogenous bases. phosphate deoxyribose {Point to the 3-D mode, if you have one, to show the parts as you discuss them.} bases

Nucleotides O -P O O ATP One deoxyribose together with its phosphate and base make a nucleotide. O -P O O Nitrogenous base C O Phosphate {Ask students where they have seen a similar molecule before in this class. Answer: ATP . Emphasize that nucleotides are the basic building blocks or units of a DNA molecule and that a single molecule has many millions of nucleotides.} C C C Deoxyribose ribose O

One Strand of DNA One strand of DNA is a polymer of nucleotides. One strand of DNA has many millions of nucleotides. nucleotide {Point to the 3-D mode, if you have one, to show the parts as you discuss them.}

Four nitrogenous bases DNA has four different bases: Cytosine C Thymine T Adenine A Guanine G These four bases are abbreviated by using their respective first letters.

Two Kinds of Bases in DNA Pyrimidines are single ring bases. Purines are double ring bases. N N C O C C N C C N

Thymine and Cytosine are pyrimidines Thymine and cytosine each have one ring of carbon and nitrogen atoms. C N O cytosine C N O thymine

Adenine and Guanine are purines Adenine and guanine each have two rings of carbon and nitrogen atoms. C N O Guanine C N Adenine

Two Stranded DNA Remember, DNA has two strands that fit together something like a zipper. The teeth are the nitrogenous bases but why do they stick together? {Point to the 3-D model to show the parts as you discuss them.}

Hydrogen Bonds The bases attract each other because of hydrogen bonds. Hydrogen bonds are weak but there are millions and millions of them in a single molecule of DNA. (The bonds between cytosine and guanine are shown here.)

Hydrogen Bonds, cont. C N O When making hydrogen bonds, cytosine always pairs up with guanine, And adenine always pairs up with thymine. (Adenine and thymine are shown here.)

Important: Adenine and Thymine always join together A T Cytosine and Guanine always join together C G

DNA by the numbers Each cell has about 2 m of DNA. The average human has 75 trillion cells. The average human has enough DNA to go from the earth to the sun more than 400 times. DNA has a diameter of only 0.000000002 m. The earth is 150 billion m or 93 million miles from the sun. If you unravel all the DNA in the chromosomes of one of your cells, it would stretch out 2 meters. If you did this to the DNA in all your cells, it would stretch from here to sun more than 400 hundred times!