Biology Homework Chapter 3: Functional Groups, Carbohydrates, and Lipids
Textbook assignment: Chapter 3: The Molecules of Cells, sections 1-7.
- Overall: Most organic molecules are made of many similar or identical components, called monomers. Together these components form the polymer organic molecules. Each time a monomer joins the chain, water is released through dehydration synthesis. Polymers break apart by absorbing water in the process of hydrolysis. If you understand the monomers and how they fit together, you can identify the type of molecule and its primary function.
- 3.1 Carbon, with up to 4 possible bonds, can form the greatest variety of monomer structures of all the elements. We group carbon molecules by whether or not they include double bonds, and by shape: linear, branched, or ring. Molecules with the same chemical formula but different structures are isomers. Because the locations of the chemical bonds holding the atoms together change, the energy required to break up the molecule, and thus all its reactions with other chemicals, are influenced by the particular arrangements. Different isomers will have different chemical properties. Moreover, surrounding environments can change the form or shape of the molecule. As you try to visualize the actual molecule, remember that the "flat" two-dimensional structural diagrams in your text do not reflect the actual distribution of atoms in space!
- 3.2 All organic molecules have a hydrocarbon chain with some common and some unique attachments. We classify the molecules by the type of common attachments (functional group) that most often reacts with other molecules. The major organic compound functional groups (hydroxyl, carbonyl, carboxyl, amino, phosphate, and methyl) can occur in combinations where there are multiple groups of one kind or mixed groups of several kinds.
- 3.3 The dehydration synthesis process joins two monomer molecules together by removing an OH- group from one and an H+ from the other, with a net loss of one water molecule. In hydrolysis, a single molecule is broken apart into two components, and water is broken apart to complete each component (lysis comes from the Greek word for loosening). By varying the sequences of a few different monomers, cells can create a huge diversity of specialized macromolecules.
- 3.4 Carbohydrates are molecules made from chains of carbon, oxygen, and hydrogen molecules called monosaccharides, where one or more of the hydrogen atoms is replaced by a functional group with oxygen and hydrogen. Glucose and fructose are isomers of the simples monosaccharide; the differences determine how cells sense and react to the molecule. The basic structure of a glucose molecule changes when it is placed in water, and since most monosaccharide molecules in organic cells are in solution, we will commonly deal with the ring form of sugars.
- 3.5 Go through the steps of dehydration synthesis used to form polysaccharides from monosaccharides. Be sure that you can identify the specific parts of the molecule that are involved in the reaction.
- 3.6 This is a "cultural enrichment" section, which provides not merely academic information you should know, but health and safety type information you need to apply to your life. The absorption and use of sugars by animals has to be regulated by hormones such as insulin. Too much or too little sugar can lead to life-threatening diabetes conditions.
- 3.7 There are three major types of complex sugars (polysaccharides): starch is a simple chain of similarly oriented glocose molecules ; glycogen is a branched molecule of starch strands, and cellulose is a set of althernating-glucose chains linked by hydrogen bonds into a a strong sheet that often appears as the strutural component of plant cell walls. Chitin is a similar strong carbohydrate structure that shows up in animal exoskeletons.
Read the following weblecture before chat: Organic Molecules
Take notes on any questions you have, and be prepared to discuss the lecture in chat.
Perform the study activity below:
Chat Preparation Activities
- Essay question: The Moodle forum for the session will assign a specific study question for you to prepare for chat. You need to read this question and post your answer before chat starts for this session.
- Mastery Exercise: The Moodle Mastery exercise for the chapter will contain sections related to our chat topic. Try to complete these before the chat starts, so that you can ask questions.
- No quiz yet: the Chapter Quiz opens when we finish the chapter.
Read through the lab for this week; bring questions to chat on any aspect of the lab, whether you intend not perform it or not. If you decide to perform the lab, be sure to submit your report by the posted due date.
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