Elements and Their Atoms
In chemistry and physics, an element is a substance that cannot be broken down into a simpler substance by chemical means. A pure element is a substance consisting of a single type of atom, with its chemical properties determined by that atom's atomic number, which is the number of protons in its nucleus. Examples of elements include carbon, oxygen, aluminum, iron, gold, copper, mercury, and lead.
The Elements of Life
In biology, the elements of life are the essential building blocks that make up living things. They are carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur. The first four of these are the most important, as they are used to construct the molecules that are necessary to make up living cells. These elements form the basic building blocks of the major macromolecules of life, including carbohydrates, lipids, nucleic acids and proteins. Carbon is an important element for all living organisms, as it is used to construct the basic building blocks of life, such as carbohydrates, lipids, and nucleic acids. Even the cell membranes are made of proteins. Carbon is also used to construct the energy-rich molecules adenosine triphosphate (ATP) and guanosine triphosphate (GTP). Hydrogen is used to construct the molecules water and organic compounds with carbon. Hydrogen is also used to construct ATP and GTP. Nitrogen is used to construct the basic building blocks of life, such as amino acids, nucleic acids, and proteins. It is also used to construct ATP and GTP. Oxygen is used to construct the basic building blocks of life, such as carbohydrates, lipids, and nucleic acids. It is also used to construct ATP and GTP. Phosphorus is used to construct the basic building blocks of life, such as carbohydrates, lipids, and nucleic acids.
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All AP Biology Resources
A fatty acid that has two double bonds between its carbon atoms is called __________.
Possible Answers:
good cholesterol
an unsaturated fatty acid
a saturated fatty acid
a hydrogenated fatty acid
Correct answer:
an unsaturated fatty acid
Explanation:
An unsaturated fatty acid has one or more double bonds in its hydrocarbon tail. These double bonds are formed by the removal of hydrogen atoms from the carbon tail, resulting in a kink in the tail. As such, they are not fully saturated with hydrogen atoms. Cholesterol is a type of lipid that contains four hydrocarbon rings in its structure. Hydrogenated fatty acids are unnatural saturated fatty acids that are modified for their physical properties.
Three fatty acids each joined to glycerol by an ester linkage is a __________.
Possible Answers:
cholesterol
steroid
phospholipid
triacylglycerol
Correct answer:
triacylglycerol
Explanation:
A triacylglycerol (also called commonly referred to as a fat or a triglyceride) is composed of three fatty acid chains linked to glycerol via an ester linkage. The fatty acids can be the same or two or three different types. Steroids are derived from cholesterol, a molecule that contains four hydrocarbon rings attached together. Phospholipids only have two fatty acid tails linked to a glycerol head and a phosphate group.
Which of the following is an example of a lipid?
Possible Answers:
cellulose
triacylglycerol
chitin
amino acid
Correct answer:
triacylglycerol
Explanation:
Triacylglycerol (also called a fat or triglyceride) is a type of lipid. Amino acids are the subunits that make up proteins. Chitin and cellulose are polysaccharides, or carbohydrates.
Which of the following terns best describes a molecule that contains three fatty acid chains bonded to a glycerol molecule?
Possible Answers:
Triglyceride
DNA
Glycogen
None of these
Cellulose
Correct answer:
Triglyceride
Explanation:
Structurally speaking, a triglyceride molecule contains three fatty acid chains covalently bonded to glycerol—specifically where the hydroxyl groups are located on the glycerol molecule.
A polyunsaturated lipid contains which of the following that is/are not contained in saturated lipids?
Possible Answers:
Sulfur atoms in place of carbons
One double bond
Multiple double bonds
A polar head group
No double bonds
Correct answer:
Multiple double bonds
Explanation:
The term saturated when describing a lipid means that a molecule has the maximum number of hydrogens on its carbons, it is saturated with hydrogens. An unsaturated lipid has less than the maximum amount of hydrogens bonded to its carbons because there is a double bond between two of the carbons. Lipids molecules can have one carbon to carbon double bond (mono-unsaturated) or multiple (poly-unsaturated).
All of the following biomolecules form true polymers except __________.
Possible Answers:
fatty acids
sugars
glucose
amino acids
nucleotides
Correct answer:
fatty acids
Explanation:
Fatty acids occur as free molecules in trace amounts in living organisms. They usually occur as a component of several types of lipid molecules, and are not true monomers, even though 1-3 of them can be attached to a polar head group such as glycerol or a phosphate group. The rest of the choices listed form polymers. Amino acids form proteins, sugars such as glucose form carbohydrates, and nucleotides form both DNA and RNA.
Which of the following statements regarding lipid molecules is true?
Possible Answers:
They store genetic information
They are soluble in water
They must contain a phosphate group
They are hydrophilic
They can be used as a source of energy
Correct answer:
They can be used as a source of energy
Explanation:
Lipids can be used as an energy source and are often used by cells to store energy for future use. Phosphate groups are not found in all lipids. For example most steroids, which are lipids, do not have phosphate groups. Lipids are hydrophobic and are repelled by water.
Which of the following correctly describes saturated fats?
Possible Answers:
In saturated fats, the carbons have double bonds between them.
Saturated fats have single bonds between nitrogen and carbon.
In saturated fats, the carbons contain the maximum amount of hydrogens bonded to them.
Saturated fats are usually liquid at room temperature.
Correct answer:
In saturated fats, the carbons contain the maximum amount of hydrogens bonded to them.
Explanation:
In saturated fats, the carbons have single bonds between them and the maximum number of hydrogen atoms. Saturated fats do not have nitrogen, and they are solid at room temperature.
Which of the following is true of unsaturated fats?
Possible Answers:
The nitrogens are bonded to a phosphate group in a chain.
Unsaturated fats have one or more double bonds between between carbons in the fatty acid chain.
Unsaturated fats have the maximum number of hydrogens bonded to the carbons.
Unsaturated fats are solids at room temperature.
Correct answer:
Unsaturated fats have one or more double bonds between between carbons in the fatty acid chain.
Explanation:
Unsaturated fats have at least one double bond between two carbons in the fatty acid and do not have the maximum number of hydrogens. They do not contain nitrogen and are usually liquid at room temperature.
Which of the following is not a function of lipids?
Possible Answers:
Maintaining body temperature
Folding proteins
Signal transduction
Storing energy
Forming membranes around organelles
Correct answer:
Folding proteins
Explanation:
Lipids are what make up fats. Fats store energy and help insulate animals against the cold. They also form lipid bilayers that surround cells and organelles. All steroid hormones are derived from cholesterol, a lipid. Thus, lipids play a significant role in signal transduction. Folding proteins is a function left to other proteins.