unit 3 Flashcards
How many different kinds of amino acids are there in most proteins?
20
Which of the following substances is made of lipids?
steroids
Which element is closely associated with the field of organic chemistry?
carbon
Which of the following molecules is a carbohydrate?
C60 H100 O50
Amino acids can be distinguished from one another by
the chemical properties of their R groups.
A disaccharide forms when
two monosaccharides join by dehydration synthesis.
Which of the following lists contains only polysaccharides?
cellulose, starch, and glycogen
Which of the following contains a carboxyl and an amino group?
amino acid
Carbohydrates are mainly used in our bodies _____.
as fuel
A DNA nucleotide is composed of a __________.
deoxyribose sugar, which is bonded to a phosphate group and a nitrogenous base
Fatty acids are
hydrophobic
A molecule with the formula C7H14O7 is probably a(n)
monosaccharide
Fatty acids with double bonds between some of their carbons are said to be
unsaturated
What is the general function of enzymes within a cell?
to speed up chemical reactions
How are these two amino acids attached together?
amino group to carboxylic acid group
DNA carries the instructions for building _____, and these instructions are found in informational units called _____.
polypeptides … genes
The lipids that form the main structural component of cell membranes are _____.
phospholipids
Which of the following is a carboxyl group?
-COOH
A shortage of phosphorus in the soil would make it especially difficult for a plant to manufacture _____.
DNA
The results of dehydration synthesis can be reversed by
hydrolysis
What feature of fats makes them hydrophobic?
Fats have nonpolar hydrocarbon chains.
Select the hydrocarbon
C3H8
The storage form of carbohydrates is ________ in animals and ________ in plants.
glycogen; starch
When two monosaccharides link to form a disaccharide, the by-product is __________.
water
A glucose molecule is to starch as _____.
a nucleotide is to a nucleic acid
When an RNA strand forms using DNA as a template, _____.
uracil pairs with adenine and cytosine pairs with guanine
Although the structures of the functional groups important to life (hydroxyl, carbonyl, carboxyl, amino, and phosphate) vary in chemical structure, they share one thing in common: They _____.
all are hydrophilic and increase the organic compound’s water solubility
Dehydration reactions __________. They do so by __________.
link monomers to form a polymer; removing a water molecule
Many names for sugars end in the suffix
-ose.
These two molecules are structural isomers. What is the difference between them?
the location of a double-bonded oxygen atom
A fatty acid containing at least one double bond is called _____.
unsaturated
Which of the following would be correctly classified as a protein?
an enzyme
The reaction that joins two monomers to form a polymer is known as a _____ reaction. The molecule of water formed is due to the interaction between _____ and a hydrogen ion.
dehydration … a hydroxyl group
Which of the following foods would contain the most starch?
Carrots
Based on the way the nitrogen-containing bases in DNA and RNA pair, you would expect the percentage of _____ to be equal to the percentage of _____. Look at the figure carefully.
A … T
Glucose molecules are to starch as ________ are to proteins.
amino acids
How does DNA differ from RNA?
RNA contains ribose, DNA does not.
A phospholipid is composed of
one glycerol molecule linked to one phosphate group and two fatty acids.
In a hydrolysis reaction, __________. In this process, water is __________.
a polymer breaks up to form monomers … consumed
Organic compounds
always contain carbon.
You work for a company that manufactures food products. A new “wonder food” is being distributed by a rival company. The researchers in your company determined that the “wonder food” contains only carbon, oxygen, and hydrogen. At this point, your researchers can say with certainty that the food
does not include proteins or nucleic acids.
A major type of lipid found in cell membranes is
phospholipids.
Which of the following is an amino group?
-NH2
