Question 2

How do the structures of biologically important molecules (carbohydrates, lipids, proteins, and nucleic acids) account for their functions? How are these molecules synthesized and broken down? [Chapter 5]

 

 

The Polymer Principles (read pages 62-65)

 

Most macromolecules are polymers. The giant molecules cells use are composed of smaller units called monomers. Be sure you understand what monomers form which polymers. A large number of different kinds of polymers can be built from a small set of monomers.

 

Monomer

Polymers

Examples

monosaccharides

polysaccharides

Starch (Carbohydrates)

Fatty acids & glycerol

triglycerids

Animal fats (Lipids*)

Amino acids

Polypeptides, Proteins

Enzymes, hemaglobin

nucleotides

Nucleic Acids

DNA, RNA

* Note that lipids don’t closely follow the monomer-polymer relationships as do the other macromolecules.

 

The process of dehydration synthesis assembles macromolecules from monomers. Explain this process.

 

 

 

The process of hydrolysis disassembles macromolecules into monomer subunits. Explain this process.

 

 

 

 

Carbohydrates (Read pages 64-68)

 

  1. Carbohydrates are sugars and their polymers. You need to know the following:

 

  1. Carbohydrates are composed of carbon, hydrogen and oxygen. The hydrogen and oxygen are in a 2:1 ratio.

 

  1. The name carbohydrate literally means carbon and water.

 

  1. Monosaccharides are the simplest sugars; molecular formulas are usually a multiple of CH2O.

 

  1. What do organisms use these molecules for?

 

  1. What is a disaccharide? Give examples.

 

  1. What do organisms use disaccharides for?

 

  1. What is a glycosidic linkage?

 

  1. Two glucose bonded together make a molecule of ______________________________.

 

  1. A glucose molecule bonded to a fructose molecule makes a molecule of _____________________.

 

  1. What are polysaccharides? What are they used for? Give some examples.

 

  1. Starch in plants has alpha 1-4 linkages, what does this mean?

 

  1. Cellulose has beta 1-4 linkages, how does this arrangement differ from starch and what is significant about this difference?

 

  1. What makes chitin different from other polysaccharides and where is it found in nature?

 

Lipids (Read pages 68-71)

 

1.      Lipids are not very soluble in water. Why is this?

 

2.      Lipids contain carbon, hydrogen, and very little oxygen. How does this distinguish lipids from carbohydrates and proteins?

 

3.       Unlike carbohydrates, lipids do not follow the monomer-polymer structure very well; triacylglycerol is an exception (or triglycerides, also known as fat – these are solids at room temperature).

 

4.      Fat are composed of one 3-cardon glycerol and 3 fatty acid molecules. How are they arranged?

 

5.      Lipids may have hydrophobic and hydrophilic parts. What does this mean?

 

6.      Distinguish between a saturated fat and a non-saturated fat?

 

7.      What is the structure of a phospholipid? And, why are phospholipids important?

 

8.      What is the common structure of all steroids? What are some of the roles steroids have in organisms? Give some examples of steroids?

 

Amino Acids and Proteins (Read Pages 71-80)

 

1.      Amino acids are the monomers of proteins.

 

2.      There are 20 kinds of amino acids in organisms.

 

3.      Proteins means “prime” and they are more than 50% of the dry weight of cells.

 

4.      Two amino acids bonded together forms a dipeptide.

 

5.      More than two amino acids bonded form a polypetide.

 

6.       Proteins are composed of one or more polypeptides.

 

7.      Be sure you can describe the basic structure of an amino acid (p. 71)

 

8.      Amino acids are held together by a covalent bond between a nitrogen and carbon, this bond is called a _________________________

 

9.      Each protein has a unique shape determined by the sequence of amino acids in the polypeptide. This shape may be altered if just one of the amino acids is out of sequence.

 

10.  Think of amino acids as letters and proteins as a word. Re-arranging the letters changes the meaning of the word.

 

11.  See what happens to a blood cell, when just one amino acid is out of place in a hemoglobin molecule on page 75 (figure 5.19). What amino is out of place according to the illustration?

 

12.  Protein function depends upon its conformation. What does this mean?

 

13.  There can be four major steps to the formation of a protein, or only one. Be sure you know what happens during each of the following:

 

a.       Primary

b.      Secondary

c.       Tertiary

d.      Quaternary

 

14.  What role do chaperonins play in protein folding?

 

 

15.   How is x-ray crystallography used to determine protein structure?

 

 

 

Nucleic Acids – DNA & RNA (Read Pages 80-84)

 

 

1.       Nucleic acids store and transmit hereditary information.

a.      DNA stores information in the sequence of its four nucleotides (ATCG)

b.       DNA is used for long term storage, RNA (AUCG)is used for short term storage.

c.       What is the structure of DNA and how does it compare to the structure of RNA?

 

 

2.      A nucleic acid is a polymer of nucleotides.

 

3.       Inheritance is based upon replication of the DNA.

 

4.       DNA (and proteins) can be used to determine the relationships between species.

 

WE WILL RETURN TO NUCLEIC ACIDS IN LATER QUESTIONS

 

 

John C. Murphy

           Science

Phone:  (815) 436-3200, ext. 2120

 

jmurphy@learningcommunity202.org

 


 

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