Assignment 2: Chapter 2 Practice Questions

Biochemistry Practice Questions

1. What is the difference between an endergonic and an exergonic reaction?
Endergonic reaction consumes or absorbs energy while exergonic reaction releases energy.

2. How many protons, neutrons, electrons, and valence electrons does Na+ have? (the atomic number for sodium is 11)
Sodium has 11 protons, 11 neutrons, 10 electrons and 8 valence electrons.

3. What is the difference between an ionic bond and a covalent bond? Which is stronger?
Ionic bond results from the attraction between ions that have opposite charges. In this bond, an atom either gains or loses an electron making it positively or negatively charged. Covalent bond are formed by sharing of pairs of electrons. Covalent bond is stronger.

4. What are the four types of organic macromolecules and which monomers link together to make up each?
The four types of organic macromolecules are:
Polysaccharides (starches) are chains of monosaccharides (sugars)
Lipids are chains of fatty acids
Nucleic Acids (DNA and RNA) are chains of nucleotides
Polypeptides (proteins) are chains of amino acids

5. Which type of bond holds together the monomers that make up the four primary organic macromolecules?


6. Which type of bonds holds together two complementary strands of DNA?
Hydrogen bonds hold together two complementary strands of DNA.

7. Why do phospholipids form micelles in water?
Phospholipid molecules are both hydrophobic and hydrophilic produce micelles in water. The charged part faces outward and the uncharged part are in the interior giving a globular form.

8. What is the difference between a saturated and an unsaturated fatty acid?
Saturated fatty acids have only single covalent bonds between carbon atoms in their carbon chain and contain more hydrogen. Unsaturated fatty acids have one or more double bonds between carbons and contain less hydrogen. The double bond causes a bend in the carbon chain. The more hydrogen you have in your body, the more saturated fats you have. Hydrogen contains ATP which means you have more calories stored in your body.

9. Often times science fiction stories make reference to silicon-based life forms as opposed to carbon-based life. Why does this make sense as a plausible possibility for alien life?
Silicon has many chemical properties similar to carbon and is in the same periodic table group, the carbon group. With this fact of information, many scholars and science fiction writers have been prompted to wrie about the possibility of silicon-based life. It is possible that the chemistry of silicon is altered sufficiently by the great temperatures and pressures deep in the Earth or out of spce to make it more suited to forming complex molecules.

10. What are the three differences between DNA and RNA?
Differences between DNA and RNA:
a) They have different sugar in backbone; deoxyribose in DNA, ribose in RNA.
b) RNA is single stranded while DNA is double stranded which consist of two chains held together by a hydrogean bond.
c) RNA contains the base uracil and DNA contains the base thymine.

11. What are the five nitrogenous bases that form the eight nucleotides that make up RNA and DNA?
a) DNA and RNA contains the nitrogenous bases: Adenine, Cytosine and Guanine
b) DNA contains Thymine and RNA contains Uracil.

12. How do nucleotides fit together to form DNA? (draw it!)

13. What causes proteins to fold into their final shape?
Characteristics of the reactive groups cause regions of the protein to attract or repel one another, causing the protein to fold into its final shape

14. What is the difference between a protein’s primary structure, secondary structure, tertiary structure, and quaternary structure?
a) Primary structure of a protein contains a sequence of amino acid in a polypeptide chain and resembles like a straight telephone cord.
b) The secondary structure consists of the foiling and coiling of the amino acid chain, such as a helix or pleated sheet, caused by the hydrogen bonds.
c) The third structure (tertiary), the chain tends to fold up to form a globular or irregular spherical structure.
d) The quarternary structure are large proteins.

15. What causes the structural shape of receptors to change?
Receptors communicate information by causing conformational (shape) changes that transmit a signal cascade like dominoes falling down. Ligands are the generic name for molecules that specifically bind to receptors which cause receptor to undergo conformational change.

16. What would happen if an enzyme were absent from a cell?
Enzymes are proteins that act as biological catalyst. The chemical reactions in living organisms exists in a lower energy level. A catalyst can either initiate a reaction or accelerates the rate of chemical reaction that is occurring slowly by decreasing the energy required to cause such reactions.
If an enzyme was absent from a cell, its metabolic reactions would occur at a rate slower than normal.

17. What would happen if a cell had too much of a particular enzyme?
Each particular enzyme has one specific job. If there is too much of a particular enzyme, it may be harmful to the body and may deregulate its functions.

18. Why are enzymes highly specific for their substrates and receptors highly specific for their ligands?
Substrates are the chemicals that are transformed with the help of enzymes. Once a substrate has come into contact with the active site of an enzyme, it is modified by the enzyme to form the end product. Once the process is complete, the enzyme releases the product and is ready to begin the process with new substrates. Enzymes are never wasted and always recycled.

19. Based on its name, what do you think proteases do?
(Hint: these are also called peptidases) Protease refers to a group of enzymes whose catalytic function is to hydrolyze (breakdown) peptide bonds of proteins.