Chapter 3 The Molecules of Life

Transcription

1 Chapter 3 The Molecules of Life State Standards Standard 1.h. Standard 5.a. Standard 4.e. Organic Molecules A cell is mostly water. The rest of the cell consists mostly of carbon based molecules organic compounds. Life s diversity results from Organic chemistry is the study of carbon compounds. Carbon Chemistry Carbon is a versatile atom. It has 4 electrons in an outer shell that holds eight. Carbon can share its electrons with other atoms Carbon can use its bonds to Attach to other carbons. Form an endless diversity of carbon skeletons. The simplest organic compounds are hydrocarbons. These are organic molecules containing Composed of a carbon skeleton with

2 The simplest hydrocarbon is methane. Larger hydrocarbons Are the main molecules in the gasoline we burnn in our cars. The hydrocarbons of fat molecules provide energy for our bodies. The unique properties of a organic compound depend not only on its carbon skeleton but also on the atoms attached to the skeleton. These atoms are called functional groups. The functional groups of an organic compound participate in chemical reactions. Hydrocarbon Practice Directions: Draw the following 5 carbon hydrocarbons: 1. Unbranched b. Why does each carbon bond to 4 other atoms? 2. With a double bond b. What is the molecular formula of this hydrocarbon? 3. Branched with no double bonds b. What is the molecular formula? 4. Ringed with one double bond b. How many hydrogen atoms are in this molecule? Hydrocarbon Practice Directions: Identify the functional group or groups in each molecule

3 Giant Molecules from Smaller Building Blocks Many of life s molecules are gigantic. Biologists call them macromolecules. Examples: DNA, carbohydrates Most macromolecules are polymers. Polymers are made by stringing together many smaller molecules called monomers. A huge number of different polymers can be made from a small number of monomers. Cells link monomers to form polymers by dehydration synthesis Polymers are broken down to monomer by the reverse process, hydrolysis

4 State whether the statement is describing dehydration synthesis or hydrolysis. 1. Connects monomers to form a polymer. 2. Produces water as a by product. 3. Breaks up polymers, forming monomers. 4. Water is used to break bonds between monomers. 5. Joins amino acids to form a protein. 6. Glycerol and fatty acids combine to form a fat. 7. Occurs when polysaccharides are digested to form monosaccharides. 8. H and OH groups form water. 9. Nucleic acid breaks up to form nucleotides. 10. Water breaks up. Biological Molecules There are four categories of large molecules in cells: Carbohydrates Lipids Proteins Nucleic acids Carbohydrates include Simple sugar molecules such as glucose in soft drinks Large polysaccharides such as starch molecules in pasta and potatoes The functions of carbohydrates include Provide energy for cellular work Short term storage of energy Building material to form plant bodies Carbon skeleton can be used to produce other organic compounds Monomers of carbohydrates The monomers of carbohydrates are the monosaccharides (simple sugars)

5 Monosaccharides Monosaccharides are simple sugars. Examples: glucose, fructose They are the source of energy for cellular work. Their carbon skeleton is used to produce other organic compounds Disaccharides A disaccharide is a double sugar It is made from two monosaccharides. Examples include: sucrose, lactose, maltose Cells link simple sugars to form disaccharides Monosaccharides can join to form disaccharides by a dehydration synthesis reaction. Polysaccharides Polysaccharides are complex sugars They are long chains of monosaccharides linked together by dehydration synthesis reactions. Examples include: starch, glycogen, cellulose Lipids Lipids are composed mainly of carbon and hydrogen They are grouped together because they are hydrophobic. Functions are: long term energy storage, hormones (chemical messengers) Examples: fats, steroids, phospholipids, waxes Fats Fats are lipids whose main function is long term energy storage They are also called triglycerides Fats perform essential functions in the human body: Long term energy storage Cushioning Insulation A triglyceride is a combination of glycerol and three fatty acid. Fatty acids can be saturated or unsaturated

6 Healthy fats Not all fats are unhealthy. Some fats perform important functions in the body and are essential to a healthy diet Example: omega 3 fats found in some fish Steroids Steroids are very different from fats in structure and function. The carbon skeleton is bent to form four fused rings. Cholesterol is the base steroid from which your body produces other steroids Example: sex hormones Anabolic steroids Anabolic steroids are usually synthetic forms of testosterone. Some athletes use them to build up their muscles quickly. However, these substances can pose serious health risks. Phospholipids and Waxes Phospholipids are a major component of cell membranes. Waxes form waterproof coatings. Proteins Proteins perform most of the tasks the body needs to function This includes: enzymes transport hormones structural components antibodies contractile The building blocks of proteins are amino acids. There are 20 different amino acids. Each amino acids consists of A central carbon atom bonded to 4 covalent partners A side group that is different for each of the 20 amino acids. Cells link amino acids together by dehydration synthesis reactions. The resulting bond between them is called a peptide bond.

7 Your body has tens of thousands of different kinds of proteins The diversity of proteins is based on its primary structure the specific sequence of amino acids Proteins differ in The different arrangements of the amino acids The number of amino acids they contain A slight change in the primary structure of a protein affects its ability to function. The substitution of one amino acid for another in hemoglobin causes sickle cell disease. Protein Structure A protein s shape determines its function. The shape of a protein is sensitive to the surrounding environment. Unfavorable temperature and ph changes can cause a protein to unravel, lose its shape and its function. This is called denaturation Nucleic Acids Nucleic acids are information storage molecules. They provide the directions for building proteins. They ultimately control the life of a cell. There are two types of nucleic acids: DNA, deoxyribonucleic acid RNA, ribonucleic acid The monomers of nucleic acids are nucleotides. Each nucleotide is composed of a sugar, a phosphate group, and a nitrogenous base. Each DNA nucleotide has one of the following bases: Adenine (A) Guanine (G) Thymine (T) Cytosine (C) Nucleotides are linked into long chains. A sugar to phosphate backbone joins the nucleotides together. The Structure of DNA The sugar in DNA is dexoyribose. The two strands of DNA join together to from a double helix. The sequence of the bases in DNA carries genetic information.

8 DNA Provides the Instructions to Make a Protein The genetic instructions in DNA are used to produce the primary structure of a protein. Structure of RNA RNA is different from DNA Its sugar is ribose It has the base uracil (U) instead of thymine (T) It is single stranded ATP The Cell s Energy ATP provides the energy needed for almost all cell and body activities. ATP is composed of: a ribose sugar the base adenine 3 phosphate groups Potential energy is stored in the covalent bonds between the phosphate groups When the bond joining the 2 nd and 3 rd phosphate group is broken the stored energy is released and is used by the cell to do work.