How can we help?
You can also find more resources in our
Select a category
Something is confusing
Something is broken
I have a suggestion
What is your email?
What is 1 + 3?
Chapter 1, Chapter 2, Chapter 3, and Chapter 4
Which of the following statements concerning prokaryote and eukaryotic cells is not correct?
Prokaryotic cells contain membrane enclosed organelles.
Prokaryotes are classified as belonging to two different domains. What are the two domains?
Bacteria and Archaea.
A water sample from a hot thermal vent contained a single-celled organism that had a cell wall but lacked a nucleus. What is its most likely classification?
Charles Darwin proposed a mechanism for descent with modification which stated that organisms of a particular species are adapted to their environment when they possess..
inheritable traits that enhance their survival and reproductive success in the local environment.
A controlled experiment is one in which
There are at least two groups, one of which does not receive the experimental treatment.
Which of the following sequences represents the hierarchy of biological organization from the least to the most complex level?
Molecule, cell, organ system, population, ecosystem, biosphere.
Which of the following is a false statement?
All forms of life are composed of cells that have a membrane enclosed nucleus.
In terms of the hierarchical organization of life, a bacterium is at the ________ level of organization, whereas a human is at the __________ level of organization.
Single celled organism; multicellular organism.
Which of the following is a false statement regarding deoxyribonucleic acid (DNA)?
DNA is an enzyme that puts together amino acids to make a protein.
Which of the following types of cells utilize deoxyribonucleic acid (DNA) as their genetic material but do not have their DNA within a nucleic envelope?
One difference between carbon 12 and carbon 14 is that carbon 14 has
Two more neutrons than carbon 12.
Atoms whose outer electron shells contain eight electrons tend to
Be stable and chemically nonreactive, or inert.
Fluorine has an atomic number of 9. How many electrons are needed to complete the valence shell of a fluorine atom?
About 25 of the 92 natural elements are known to be essential to life. Which four of these 25 elements make up approximately 96 percent of living matter.
Carbon, Hydrogen, Nitrogen, Oxygen.
The mass number of an element can be easily approximated by adding together the number of ______ in an atom of that element.
Protons and neutrons.
What is the approximate atomic mass of an atom with 16 neutrons, 15 protons, and 15 electrons?
How do isotopes of the same element differ from each other?
Number of neutrons.
In ammonium chloride salt (NH4Cl) the anion is a single chloride ion, CL-. What is the cation of NH4Cl?
NH4 with a charge of +1.
In a single molecule of water, two hydrogen atoms are bonded to a single oxygen atom by?
Polar covalent bonds.
The slight negative charge at one end of one water molecule is attracted to the slight positive charge of another water molecule. What is this attraction called?
A hydrogen bond.
What gives rise to the cohesiveness of water molecules?
Based on your knowledge of the polarity of water molecules, the solute molecule is most likely...
Hydrophobic substances such as vegetable oil are..
Nonpolar substances that repel water molecules.
Which of the following solutions has the greatest concentration of hydrogen ions (H+)
Gastric juice at pH 2.
A carbon atom is most likely to form what kind of bond(s) with other atoms?
Why are hydrocarbons insoluble in water?
The majority of their bonds are nonpolar covalent carbon-to-hydrogen linkages.
A compound contains hydroxyl groups as its predominant functional group. Which of the following statements is true concerning this compound?
It should dissolve in water.
Which of the following contains nitrogen in addition to carbon, oxygen and hydrogen?
A monosaccharide such as glucose.
Which two functional groups are always found in amino acids?
Carboxyl and amino.
Which of the following solutions has the greatest concentration of hydroxyl ions [OH-]?
Seawater at pH 8.
If the pH of a solution is decreased from 9 to 8, it means the...
Concentration of H+ ions has increased 10-fold (10X) compared to what it was at pH 9. Concentration of OH- ions has decreased to one-tenth (1/10) what it was at pH 9.
Buffers are substances that help resist shifts in pH by...
Donation H+ to a solution when they have been depleted. Accepting H+ ions when they are in excess.
Pure, freshly-distilled water has a pH of 7. This means that....
The concentration of H+ ions in the water equals the concentration of OH- ions in the water.
A chemist wishes to make an organic molecule less acidic. Which of the following functional groups should be added to the molecule in order to do so?
Which functional groups can act as acids?
Carboxyl and phosphate.