Question

3.4 Lipids

1. List the several different classes of lipid molecules important in living organisms.
2. Diagram the structure of a triglyceride and explain how it is affected by the presence of saturated and unsaturated fatty acids.
3. Explain why some fats are solid at room temperature, and others are liquid.
4. Discuss how fats function as energy-storage molecules.
5. Apply knowledge of the structure of phospholipids to the formation of cellular membranes.
6. Describe the chemical nature of steroids and give an example of their biological importance.

3.5 Proteins

1. Give examples of the general types of functions that are carried out in cells by different types of proteins.
2. Explain how amino acids are joined to form a polypeptide, and distinguish between a polypeptide and protein.
3. Describe the levels of protein structure and the factors that determine them.
4. Outline the bonding forces important in determining protein shape and function.
5. Explain what domains are and their importance in proteins.

3.6 Nucleic Acids

1. Describe the three components of nucleotides.
2. Distinguish between the structures of DNA and RNA.
3. Describe how certain bases pair with others in DNA and RNA.

Answer 1

3.4 Lipids

Several classes of lipid molecules important in living molecules are:

I. Triglyceol : storage lipids.

II. Glycerophospholipids: found in cell membrane

III. Sphingolipid: found in cell membrane

IV. Waxes: form extra coating of animal

V. Steroids : act as messager

Figure : Structure of triglycerides

Some fats are solid at room temperature whereas some are liquid because of the the packing of saturated and unsaturated fats. The unsaturated fat make some bends that do not allow to form tightly stacked structure and are liquid in nature whereas saturated fats formation tightly packed structure and hence are solid in nature.

Fats function as a energy source because upon oxidation they produce more water and carbon dioxide.

Phospholipids are membrane lipids that constitute phosphate and lipids. The lipids allow fluidity so that different molecules are passed through the membrane and proteins are embedded in the lipid structure.

Steroids are a type of lipids molecules as they are hydrophobic and but their structure is not like lipids. For example, cholesterol is a steroid that is the precursor of many hormones and vitamin D.