|
|
|
Lecture 14 Molecules of Life p. 11-18
“We are what we eat, we eat what we are.” Author Unknown
Life is all about shaping new molecules from old. Plants make green leaves from air, water, and soil. Animals make flesh from grass. Enzymes carry out these changes, altering molecules by way of chemical reactions." Robert Thornton, Chemistry of Life CD-ROM
Four categories of molecules make up living organisms
carbohydrates, proteins, lipids, nucleic acids
1. Carbohydrates (CH2O)n Fig. 1.9 carbon + water a. Energy storage: Here are examples of carbohydrates used in energy storage.
b. Structural carbohydrate of cellulose Cellulose is used by the plant for rigidity to make the cell wall. It is the most abundant biological molecule on Earth. Cellulose is indigestible by humans but is still healthy as the fiber we eat. Some protists and bacteria can digest cellulose, and these are found in the stomach of herbivores like cows. Fungi can digest cellulose, too. Products from cellulose are wood and paper.
2. Proteins Fig. 1.10 and 1.11
a. Functions Catalyze chemical reactions-help chemical occur without being used up. Protein catalysts of living organisms are called enzymes. The majority of proteins in living organisms are enzymes.
b. Structure Building blocks of proteins are amino acids. 20 different amino acids are used. Humans need 9 essential amino acids (need to get these in diet) Our bodies build the other 11. Plants build all 20 from elements like nitrogen and carbon. Arrangements of these 20 amino acids in different orders and amounts build different proteins.
Shape of protein is related to its function
Example: Hemoglobin protein is shaped so that oxygen fits into its pockets. In sickle-cell anemia, one wrong amino acid of 146 gives a faulty protein structure which gives a bad protein shape and bad function (doesn’t carry oxygen well).
3. Lipids (fig. 1.12)
a. Defined: Insoluble in water. Lots of C-H bonds. Lots of energy like fats or waxes. Examples:
b. Saturated vs. Unsaturated fat vs. Trans fats 1) Structurally, saturated fats contain carbons completely filled with hydrogen atoms. Unsaturated fats have some C=C double bonds with the hydrogen atoms on the same side or "cis". Trans fats are manmade conversions of unsaturated fats into an arrangement with some C=C double bonds but with the hydrogen atoms across from one another or "trans". 2) Importance Saturated fats and trans fats are converted to cholesterol which is linked to heart disease. Unsaturated fats are not made into cholesterol. Plants generally contain most of their fats in an unsaturated form. An exception to this rule are the tropical oils, palm and coconut oil, which are mainly saturated fats. Trans fats that we consume are mostly a product of partial hydrogenation of vegetable oils. This partial hydrogenation helps them mix better (think Skippy peanut butter vs. natural). You can read about trans fats at Wikipedia.
4. Nucleic acids (fig. 1.13) DNA=deoxyribonucleic acid All information of life is contained in nucleic acids. The information of nucleic acids tells the cell how to build proteins.
5. Plants are chemical factories (Box 1.2, p.10-11). Using chemistry, plants build many products important to people. See the list of some on p. 11.
Exercise
As you read the following paragraph, fill in the blanks with correct molecule of life. Look at Fig. 3.11 in Levetin.
1. The wax being deposited on the upper and lower epidermis is a _________________.
2. As photosynthesis occurs in the chloroplasts, glucose and starch are built to store energy as ____________________________________. 3. Water is transported through the veins. These rigid pipes are made of cellulose which is a structural _____________________. 4. . In class, we saw that potatoes could break down hydrogen peroxide and release oxygen. This breakdown is controlled by an enzyme which is a _______________________. Similarly, building glucose and starch in photosynthesis depends on many enzymes, all of which are also ___________. 5. All the information on how to build different enzymes is found in the DNA in the nucleus. DNA is a ____________________________________.
Lecture Notes List Next lecture |