Biological molecules

june 2002 exam

Biological Molecules Notes

1. What is a Monosaccharide? -ready energy/primary energy source
-A simple sugar contains carbon, hydrogen, and oxygen in the ratio of 1:2:1. (empirical formula) Important simple sugars are: glucose, galactose, ribose, and fructose, deoxyribose.

2. What is a disaccharide? - transport forms eg sucrose (maple sugars)
-Two simple sugars bond together to form a chain of two simple sugars called a disaccharide. When this occurs, water is removed (dehydration synthesis). A disaccharide can be split into two simple sugars by putting the water back in (hydrolysis). Examples of disaccharides are: sucrose (glucose + fructose); lactose (glucose + galactose); maltose (glucose + glucose).

3. What are polysaccharides? storage forms
-They are long chains of simple sugar molecules bonded together. Important polysaccharides are:

Starch (storage form of sugar in plants), (Less highly branched than glycogen)

Cellulose (the structural components of cell walls of plants),

Glycogen (storage form of sugar in animals.) (more highly branched than starch)

4. What are Lipids?
-Group of organic substances that are in insoluble in polar substances like water. Examples are: Fats; Oils; Phospholipids; cholesterol.

There are 3 main types of lipids

a. Neutral fats - make up adipose tissue in our bodies and functions as long term energy storage, insulates and protects. The unit molecules or monomers that make up neutral fats are fatty acids and glycerol. Neutral fats are composed of one glycerol molecule and 3 fatty acid chains.
The diagram below shows the reaction that results in the formation of a neutral fat. X is glycerol, and Y represents the 3 fatty acid molecules. The neutral fat is shown on the right of the reaction arrows.

b. Steroids - 4 fused rings of carbon atoms with a chain attached. Some common examples are testosterone, estrogen, progesterone. Functions to maintain secondary sex characteristics, causes puberty in both sexes, maintains water balance.

c. Phospholipids - Fatty acids, glycerol and phosphate make up phospholipids. The phospholipids make up part of the cell membrane. Notice where the phosphate atom is located.

5. What is a FAT made up of? see lipids above
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6. What is a Nucleotide? What molecules are made up of nucleotides?
-Nucleotides are the unit molecules that make up nucleic acids. DNA and RNA, are nucleic acids

The molecules which make up Nucleotides are a 5 carbon sugar, a phosphate and a base

7. What is an unsaturated and saturated fat?
-A unsaturated fat can be recognized it by the many double bonds between the carbons.

A saturated fat has all its carbon atoms bonded, there is no more room for other atoms. There are no double bonds

8. What is an amino acid? What molecules are made up of amino acids?
-Amino acids are the unit molecules that make up proteins. They are characterized by a central carbon with an amino group(NH2) (X) on one end and an acid group (COOH) (Y) on the other.

The R group is represented by X in the diagram below

The diagram below shows two different ways that the chemical formula for an amino acid can be shown

Each of the 20 amino acids has it's own "identity" because of it's R-Group.
-Two amino acids joined together form a dipeptide. The bond joining them is a peptide bond. Look in the textbook and see what a peptide bond looks like

-Many amino acids linked together form polypeptides or polypeptide chains. These chains can be classified according to their structures. eg.

a. Primary structure (a linear sequence of amino acids joined by peptide bonds ( eg. like beads on a necklace). No folding, no 2 dimensional shape, no hydrogen bonding or bonding between R groups.

b. Secondary structure - (hydrogen bonding and an alpha helix shape) shaped like a spiral staircase, the shape is maintained by hydrogen bonds. Hydrogen bonding takes place along the entire length of the polypeptide.

c. Tertiary structure (bonding between R groups, covalent bonding, hydrogen bonding. It has a 3 dimensional shape )

d. Quaternary structures- involves 2 or more polypeptides linked together

The major functions of proteins

Some of the major functions of proteins are:

-Keratin makes up hair and nails and Collagen which gives support to ligaments, tendons and skin are structural proteins

-Hormones are proteins that influence cellular metabolism

-actin and myosin accounts for movement in cells and the ability for muscles to contract

-Some proteins transport molecules in the blood eg hemoglobin carries oxygen

-Anitbodies are proteins that combine with foreign substances and destroy them

-enzymes are proteins that speed up chemical reactions

-proteins in the plasma membrane form channels that allow substances to enter the cell and are carriers that transport molecules into and out of the cell

9. What is ATP (Adenosine triphosphate)

It is the energy molecule of the cell. The bonds that hold the phosphates to the adenosine molecule are broken and energy is released. This energy is used to power different cellular processes like active transport. See the diagram of ATP below. W is the nitrogenous base (adenine) , X is the ribose sugar, together W and X make up Adenosine. Y is a phosphate group, and Z is the high energy bond between the phosphate groups. When Z is hydrolyzed, energy is released that can be used by the cell.

10. What is hydrolysis? What is synthesis?

-Hydrolysis is a breakdown process shown in the diagram from Y to W eg. Y could be proteins, W therefore would be amino acids. The diagram below shows the breakdown of a polymer into unit molecules

-Synthesis is a buildup process shown in the diagram from W to Y eg. W. could be monosaccharides and Y would be polysaccharides. The diagram above would move to the left.

Cell Chem Quiz Questions

1. What is the definition of the following:

a. acid b. base c. buffer d. pH e. dependent variable f. independent variable

2. Define synthesis and give an example of the process

3. Define hydrolysis and give an example of the process

4. Define what the "control" in an experiment is and give an example

5. Define homeostasis and give an example

6. What is the name of the unit molecules that make up proteins?

7. Name three different proteins and list their functions ?

8. What is the definition of: a. primary protein structure b. secondary c. tertiary

9. Define protein denaturation and give three examples of substances that would cause it

10. List the main functions of carbohydrates

11. What is the definition of the following:

a. carbohydrate b. monosaccharide c. disaccharide d. polysaccharide e. neutral fat

f. steroid g. phospholipid h. saturated fat i. unsaturated fat j. ATP

k. nucleic acid l. polar molecule m. hydrogen bond n. phosphate bond o. nucleotide

12. Identify each of the following chemicals

Cell Chemistry Subjective Questions

1. List the difference between the following pairs of terms (2 marks each )

a. secondary protein structure and tertiary protein structure b. dehydration synthesis and denaturation

c. unsaturated and saturated fat d. enzymes and genes

e. primary and secondary protein structure d. inorganic and organic compounds

e. neutral fat and cellulose f. hydrogen bond and polar molecule

g. tertiary and secondary protein structure h. primary and tertiary protein structure

i. polysaccharide and polypeptide j. inorganic and organic compounds

k. hydrogen bond and polar molecule l. neutral fat and steroid

m. starch and protein molecules

2. Each of the following statements illustrates a characteristic of water. Provide a chemical explanation that accounts for the specific characteristic of water and describe its significance to the living organism.

a. Organisms are made up of a high percentage of water (3 marks )

b. Various materials dissolve in water (3 marks)

c. Sweating occurs when we are hot (3 marks )

d. Large bodies of water maintain a relatively constant temperature (3 marks)

3. Draw a diagram to show the difference between dehydration synthesis and hydrolysis, using a specific organic molecule like starch as an example. (4 marks)

4. Hydrogen bonding gives water special properties that are important to living organisms. Describe how the characteristics of water are important to living systems. (4 marks)

5. Describe what happens to a protein when it is denatured. Give an example of a protein which has undergone denaturation ( 2 marks)

6. Explain the process of dehydration synthesis, using a specific organic molecule of your choice as an example. You may draw a diagram to help your explanation (3 marks)

7. Explain the process of hydrolysis, using a specific organic molecule of your choice as an example. You may draw a diagram to help your explanation (3 marks)