Download Biology Ch. 2 Review

Name___________KEY_________________
Biology Ch. 2 Review:
9-26-16
Hour________ Desk #_________
Use Ch. 2 notes & the textbook to complete the following.
Write your answers on loose-leaf paper.
Vocabulary: The vocabulary terms in this chapter are related to each other in various ways. For
each group of words below, write a sentence or two to clearly explain how the terms are
connected. For example, the terms covalent bond and molecule, you could write “A molecule
is made of atoms connected by covalent bonds.”
1. atom, ion=
Atoms are the basic unit of matter. An atom that gains or loses electrons and has a
charge is an ion.
2. hydrogen bond, cohesion=
Cohesion in water is the result of hydrogen bonds that form from one polar water
molecule being attracted to another.
3. solution, solvent=
A solvent dissolves other substances to form a solution.
4. acid, base, pH=
Acids have high concentration of hydrogen ions and a low pH. Bases have a low
concentration of hydrogen ions and a high pH.
5. exothermic, endothermic=
Exothermic reactions release more energy than they absorb. Endothermic reactions
absorb more energy than they release.
6. catalyst, enzyme=
A catalyst is a substance that increases the rate of a chemical reaction and enzymes
are biological catalysts.
Word Origins
7. The word atom comes from the Greek word atomos, which means “indivisible.”
Describe the relationship between the Greek term and your understanding of atoms.
An atom is the basic unit of matter. It cannot be broken down by normal chemical
means.
8. The p in pH stands for the German word Potenz, which means “power” or “potential.”
The “H” represents hydrogen ions (H). How are these related to the definition of pH?
pH is the strength or concentration of hydrogen ions that makes a solution acidic or
basic.
9. The prefix mono- means “one” and the prefix poly- means “many.” Some lipids are
monounsaturated and others are polyunsaturated. Explain the difference between fatty
acids in these different types of lipids.
A monounsaturated lipid has one unsaturated carbon in its fatty acid tail(s); a
polyunsaturated lipid has 2 or more unsaturated carbons in its fatty acid tail(s).
Reviewing Main Ideas
10. Explain how the combination of electrons, protons, and neutrons results in the neutral
charge of an atom.
Neutrons have no charge. Each proton has a charge of +1, and each electron has a
charge of -1. Atoms are neutral when the # of protons and electrons are equal.
11. Potassium ions (K+) have a positive charge. What happens to a potassium atom’s
electrons when it becomes an ion?
Loses one electron.
12. Some types of atoms form more than one covalent bond with another atom. What
determines how many covalent bonds two atoms can make? Explain.
If atoms need more than one electron to fill their outermost energy levels, they can
share more than one electron pair.
13. How is hydrogen bonding among water molecules related to the structure of the water
molecule?
The larger oxygen atom pulls electrons away from the hydrogen atoms, producing
charged regions that result in hydrogen bonding.
14. Explain the difference between solvents and solutes.
Solvents are present in greater concentrations and dissolve solutes.
15. Describe the relationship between hydrogen ions (H+) and pH.
How is pH related to a solution’s acidity?
There is an inverse relationship-the greater the hydrogen ion concentration, the lower
the pH, the more acidic the solution.
16. Carbon forms a very large number of compounds. What characteristic of carbon atoms
allows the formation of all these compounds? Explain.
Carbon atoms have four unpaired electrons in their outermost energy level, so they
can form four covalent bonds.
17. Identify and explain examples of monomers and polymers in carbohydrates, proteins,
and nucleic acids.
Carbohydrates-Simple sugars (Example: glucose) are monomers that are bonded to
form polysaccharides (Example: cellulose).
Proteins-Amino acids are monomers that are bonded to form proteins.
Nucleic acids-Nucleotides are monomers that are bonded to form nucleic acids.
18. Explain the relationship between a protein’s structure and its ability to function.
The specific function of a protein is dependent on its precise structure. A change in
protein structure changes its function.
19. What are the components of a chemical reaction?
Substances that are changed in a chemical reaction are reactants; substances made
are products.
20. Explain the difference between exothermic and endothermic reactions.
If a reaction absorbs more energy than it releases (net gain), it is an endothermic
reaction and the products have a higher bond energy than reactants have.
If a reaction releases more energy than it absorbs (net release of energy), it is an
exothermic reaction and the products have a lower bond energy than the reactants
have.
21. Describe the effect of a catalyst on activation energy and reaction rate.
A catalyst decreases activation energy and increases reaction rate.
22. What is the role of enzymes in organisms?
Enzymes allow reactions to occur at high rates under the tightly controlled conditions
found in organisms.
23. Homeostasis involves the maintenance of constant conditions in an organism. What
might happen to a protein if homeostasis is disrupted? Why?
A protein’s function might be disrupted if hydrogen bonds break and the protein’s
structure changes due to changes in pH or temperature.
24. Suppose you had a friend who wanted to entirely avoid eating fats. What functions of
lipids could you describe to convince that person of the importance of fats to his or
her health?
Lipids are a major component of cell membranes, they store energy, and they are used
to make hormones.
25. The human body can reuse some of the enzymes found in raw fruits and vegetables.
Why is this not the case for cooked fruits and vegetables?
In raw foods, enzyme structures are still intact & can be reused. When foods are
cooked, the enzyme structure is destroyed, and it loses its function.
Interpreting Visuals
26. Briefly explain what is happening at each step of the process. Be sure to identify each of
the substances (A, B, C, & D) shown in each step of the process.
Substrate B binds to active site of enzyme A; a chemical reaction occurs due to the
reactants’ weakened bonds; products C & D are released from the enzyme.
27. How does Substance A affect the amount of activation energy needed by the process?
Explain.
It decreases the amount of activation energy needed because the weakened bonds of
the substrate are easier to break.
28. Describe the importance of buffers in solutions in allowing the process shown above to
take place.
Buffers help keep pH stable. Conditions such as pH need to be tightly controlled so
that hydrogen bonds between amino acids in enzymes can remain intact.
29. Suppose the graph above was constructed from data collected during an experiment.
What were the independent and dependent variables in the experiment? Explain.
The independent variable is enzyme (or catalyst) concentration; the dependent
variable is energy required.
30. How much activation energy is needed to start the chemical reaction represented by
each line on the graph? How much energy is released from each reaction?
17 units needed/21 units released; 12 units needed/16 units released; 8 units
needed/12 units released
31. Explain whether each of the chemical reactions shown on the graph is endothermic or
exothermic.
They are all exothermic because they release more energy than they absorb.