Download Background Biology and Biochemistry Practice

Background Biology and Biochemistry Practice Questions/Answers C
1. What are elements and compounds? Give an example of each.
An element is a pure substance, and it cannot be broken down into other types of
substances. A compound is a substance that consists of two or more elements. For
example, copper is an element and water is a compound.
2. List the four major types of organic compounds.
Carbohydrates, lipids, proteins and nucleic acids.
3. What determines the primary structure of a protein?
The sequence of amino acids.
4. State two functions of proteins.
Proteins help cells keep their shape.
It also speeds up chemical reactions.
5. Identify the three parts of a nucleotide.
Sugar, phosphate group and nitrogenous base.
6. Butter is a fat that is a solid at room temperature. What type of fatty acids does
butter contain? How do you know?
Butter contains saturated fatty acids. This is because saturated fatty acids are solids
at room temperature.
7. Assume that you are trying to identify an unknown organic molecule. It contains only
carbon, hydrogen, and oxygen and is found in the cell walls of a newly discovered plant
species. What type of organic compound is it?
A lipid.
8. Explain why carbon is essential to all known life on Earth.
The reason is carbon's ability to form stable bonds with many elements, including itself.
This property allows carbon to form a huge variety of very large and complex molecules.
9. Compare and contrast the structures and functions of simple sugars and complex
carbohydrates.
Simple sugars such as fructose and glucose are monosaccharides and the building blocks
of carbohydrates. Complex carbohydrates are polysaccharides that form when simple
sugars bind together in a chain.
10. Explain why molecules of saturated and unsaturated fatty acids have different
shapes.
In saturated fatty acids, carbon atoms are bonded to as many hydrogen atoms as
possible, and this causes its molecules to form straight chains.
On the other hand, in unsaturated fatty acids, some carbon atoms are not bonded to as
many hydrogen atoms as possible. Instead, they are bonded to other groups of atoms.
This causes its molecules to form bent chains.
11. Identify the roles of reactants and products in chemical reactions.
Reactants are the substances that start a chemical reaction. Products are the
substances that form as a result of a chemical reaction.
12. What is the general chemical equation for an endothermic reaction?
Reactants + Heat → Products
13. What are biochemical reactions? What is an example?
Biochemical reactions are chemical reactions that take place inside the cells of living
things. For example, it is photosynthesis.
14. How do enzymes speed up biochemical reactions?
Enzymes work by reducing the amount of activation energy needed to start the chemical
reaction.
15. What is wrong with the chemical equation below? How could you fix it?
CH4 + O2 → CO2 + 2H2O
CH4 + 2O2 → CO2 + 2H2O
16. What type of reaction is represented by the following chemical equation? Explain
your answer.
2Na + 2HCl → 2NaCl + H2 + heat
An exothermic reaction. This is because this chemical reaction releases energy as heat.
(i.e. Heat is present in the product side.)
17. How does a chemical equation show that matter is always conserved in a chemical
reaction?
The same number of atoms of each element appears on each side of the arrow in a
chemical equation. (i.e. The quantity of each element does not change.)
18. Why do all chemical reactions require activation energy?
In order for reactions to begin, reactant molecules must bump into each other strongly
enough to break old bonds and form new bonds. This requires energy.
19. Explain why organisms need enzymes to survive.
A typical biochemical reaction could take several days to occur without an enzyme. With
the proper enzyme, the same reaction can occur in just a split second. Organisms need
biochemical reactions to occur right away in order to survive.
20. Where is most of Earth’s water found?
In Oceans.
22. What is polarity? Describe the polarity of water.
Polarity is a difference in electrical charge between different parts of the same
molecule.
About the polarity of water, the oxygen atom in a water molecule attracts electrons
more strongly than the hydrogen atoms do. As a result, the oxygen atom has a slightly
negative charge, and the hydrogen atoms have a slightly positive charge.
23. What is the pH of a neutral solution?
It is 7.
24. Describe an example of an acid or a base that is involved in human digestion.
When food is digested in our stomach, the enzyme pepsin is used to help break down
proteins. In order for the pepsin to work, an acidic environment is needed in the
stomach. The stomach secretes a strong acid to meet this need. But, when stomach
contents enter the small intestine, the base secreted by the pancreas neutralizes the
acid.
25. Assume that you test an unknown solution and find that it has a pH of 7.2. What
type of solution is it? How do you know?
It is a base. This is because a solution with a pH higher than 7 is called a base.
26. How could you demonstrate to a child that solid water is less dense than liquid
water?
I would put a piece of ice on water, and let the child see that ice floats on water. (This
shows that the density of solid water, or ice is lower than that of liquid water.)
27. Explain how water’s polarity is related to its boiling point.
The polarity of a water molecule causes a hydrogen bond. Hydrogen bonds between
water molecules make water sticky. (i.e. Water molecules tend to stick together, and
resist getting apart. In order for liquid water to become gaseous, it needs to break
hydrogen bonds and become apart.) This property of water causes water to have a
relatively high boiling point of 100 ℃.
28. Explain why metabolism in organisms depends on water.
Water can dissolve many substances that organisms need, and it is necessary for many
biochemical reactions such as photosynthesis and cellular respiration.