Chapter 2

An ion, such as Ca2+ or Mg2+, that must be present in order for an enzyme to work is called a(n)_____.

cofactor

Calculate the amount of NaCl you would weigh out to make one liter of 0.9% NaCl. Explain how you would make a liter of this solution.

0.9% = 0.9 g/100 mL. Dissolve 9 g NaCl in water to yield 1 L of solution.

Name three nucleotides or nucleic acids, and tell why each one is important.

ATP: usable energy in a high-energy bond. DNA stores genetic information. RNA translates genetic information into proteins. cAMP: transfer of signals into cells. NAD and FAD transfer energy.

True or false? All organic molecules are biomolecules.

False. All biomolecules are organic molecules, but the reverse is not true.

Proteins combined with fats are called______, and proteins combined with carbohydrates are called______.

Lipoproteins Glycoproteins

Based on what you know from experience about the tendency of the following substances to dissolve in water, predict whether they are polar or nonpolar molecules: table sugar, vegetable oil.

Table sugar dissolves easily, so it is polar. Vegetable oil does not dissolve in water, so it is nonpolar.

Match these definitions with their terms (not all terms are used): a. the ability of a protein to bind one molecule but not another b. the part of a protein molecule that binds the ligand c. the ability of a protein to alter shape as it binds a ligand 1. irreversible inhibition 2. induced fit 3. binding site 4. specificity 5. saturation

a - 4 b - 3 c - 2

You have been asked to design some drugs for the purposes described next. Choose the desirable characteristic(s) for each drug from the numbered list. a. Drug A must bind to an enzyme and enhance its activity. b. Drug B should mimic the activity of a normal nervous system signal molecule. c. Drug C should block the activity of a membrane receptor protein. 1. antagonist 2. competitive inhibitor 3. agonist 4. allosteric activator 5. covalent modulator

a - 4, 5 b - 3 c - 2, 1

A 1.0 M NaCl solution contains 58.5 g of salt per liter. (a) How many molecules of NaCl are present in 1 L of this solution? (b) How many millimoles of NaCl are present? (c) How many equivalents of Na+ are present? (d) Express 58.5 g of NaCl per liter as a percent solution.

a) 6.02 × 1023 molecules of NaCl b) 1000 millimoles c) 1 equivalent d) 5.85% solution

How would you make 200 mL of a 10% glucose solution? Calculate the molarity of this solution. How many millimoles of glucose are present in 500 mL of this solution? (Hint: What is the molecular mass of glucose?)

10% glucose = 10g/100 mL or 20 g/200 mL solution. Molarity: 10 g/100 mL = 100 g/L × 1 mole/180g = 0.556 moles/L or 556 millimoles/L (556 mM). 500 mL of 10% glucose would have 50 g glucose × 1 mole/180 g = 278 millimoles glucose.

A solution in which [H+] = 10-3 M is (acidic/basic), whereas a solution in which [H+] = 10-10 M is (acidic/basic). Give the pH for each of these solutions.

10−3 M = pH 3; acidic. 10−10 M = pH 10; basic.

A negatively charged ion is called a(n)____, and a positively charged ion is called a(n)____.

Anion Cation

Fill in the blanks with the correct bond type: In a(n)____bond, electrons are shared between atoms. If the electrons are attracted more strongly to one atom than to the other, the molecule is said to be a(n)_____molecule. If the electrons are evenly shared, the molecule is said to be a(n)____ molecule.

Covalent Polar Nonpolar

You know that two soluble proteins are isoforms of each other. What can you predict about their structures, functions, and affinities for ligands?

Isoforms are structurally similar, with similar functions but differing affinities for ligands. They may function best under different conditions.

The harder a cell works, the more CO 2 it produces. CO 2 is carried in the blood according to the following equation: CO2 + H2O ⇌ H2CO3 ⇌ H+ + HCO3- What effect does hard work by your muscle cells have on the pH of the blood?

More CO2 means more H+ by the law of mass action. More H+ means a decrease in pH.

The graph shown below represents the binding of oxygen molecules (O2) to two different proteins, myoglobin and hemoglobin, over a range of oxygen concentrations. Based on the graph, which protein has the higher affinity for oxygen? Explain your reasoning. (look at graph on review sheet Ch. 2 Pt. 4)

Myoglobin has a higher affinity for O2 because at lower oxygen concentrations, myoglobin binds more O2 than hemoglobin does.

You have been summoned to assist with the autopsy of an alien being whose remains have been brought to your lab. The chemical analysis returns with 33% C, 40% O, 4% H, 14% N, and 9% P. From this information, you conclude that the cells contain nucleotides, possibly even DNA or RNA. Your assistant is demanding that you tell him how you knew this. What do you tell him?

Nucleotides contain all of the elements listed in the right ratio. Carbohydrates have a C:H:O ratio of 1:2:1, so alien does not have enough H. Fats are mostly C and H with little O (not enough H and too much O). Proteins do not have P and have less N relative to C.

An atom of carbon has four unpaired electrons in an outer shell with space for eight electrons. How many covalent bonds will one carbon atom form with other atoms?

One carbon atom needs to share four electrons to fill its outer shell; therefore, it will form four covalent bonds.

Name two elements whose presence contributes to a molecule becoming a polar molecule.

Oxygen and nitrogen strongly attract electrons and tend to form polar bonds.

List the four kinds of biomolecules. Give an example of each kind that is relevant to physiology.

Proteins (collagen, hemoglobin, enzymes); carbohydrates (glucose, sucrose); lipids (cholesterol, phospholipids); and nucleic acids (ATP, DNA, RNA).

Define the pH of a solution. If pH is less than 7, the solution is____; if pH is greater than 7, the solution is____.

pH = H+ concentration. pH <7 is acidic. pH >7 is basic or alkaline.

A molecule that moderates changes in pH is called a_____.

buffer

A protein whose structure is altered to the point that its activity is destroyed is said to be____.

denatured

A molecule that binds to another molecule is called a(n)______.

ligand

When atoms bind tightly to one another, such as H2O or O2, one unit is called a(n):

molecule