Exam 2 Questions
If one strand of DNA molecule has the sequence of bases 5'ATTGCA3', the other complementary strand would have the sequence ___.
5'TGCAAT3'
One of the buffers that contribute to pH stability in human blood is carbonic acid (H2CO3). Carbonic acid is a weak acid that, when placed in an aqueous solution, dissociates into a bicarbonate ion (HCO3-) and a hydrogen ion (H+), as noted below. H2CO3 <--> HCO3- + H+ If the pH of blood increases, one would expect ___.
A decrease in the concentration of H2CO3 & an increase in the concentration of HCO3-
Which of the following descriptions best fits the class of molecules known as nucleotides?
A nitrogenous base, a phosphate group, and a sugar
What effect can occur because of the high surface tension of water?
A raft spider can walk across the surface of a small pond
What event accompanies energy absorption by chlorophyll (or other pigment molecules of the antenna complex)?
An electron is excited
Lactose, a sugar in milk, is composed of one glucose molecule joined by a glycosidic linkage to one galactose molecule. How is lactose classified?
As a disaccharide
Compared to a hydrocarbon chain where all the carbon atoms are linked by a single bond, a hydrocarbon chain with the same # of carbon atoms, but with one or more double bonds, will ___.
Be more constrained in structure
How might a change of one amino acid at a site , distant from the active site of an enzyme, alter an enzyme's substrate specificity?
By changing the shape of the enzyme
What most precisely describes the cellular process of breaking down large molecules into smaller ones?
Catabolism (catabolic pathways)
A noncompetitive inhibitor decreases the rate of an enzyme reaction by ___.
Changing the shape of the enzyme's active site by using an allosteric site
What is the term used for a protein molecule that assists in the proper folding of other proteins?
Chaperonin
Anabolic pathways ___.
Consume energy to build up polymers from monomers
A carbon atoms is most likely to form what kind of bond(s) with other atoms?
Covalent
What best summarizes the relationship b/w dehydration reactions and hydrolysis?
Dehydration reactions eliminate water from membranes; hydrolysis reactions add water to membranes
What is a statement of the first law of thermodynamics?
Energy cannot be created or destroyed
Which of the following solutions would require the addition of the greatest amount of base to bring the solution to neutral pH? Gastric Juice at pH 2 Vinegar at pH 3 Black Coffee at pH 5 Household Bleach at pH 12
Gastric Juice at pH 2
The partial negative charge at one end of the water molecule is attracted to the partial positive charge of another water molecule. What is this attraction called?
H Bond
Which type of bond must be broken for water to vaporize?
H Bonds
If the cytoplasm of cell is at pH 7, & the mitochondrial matrix is at pH 8, then the concentration of H+ ions ___.
Is 10 times higher in the cytoplasm than in the mitochondrial matrix
The active site of an enzyme is the region that ___.
Is involved in the catalytic reaction of the enzyme
What is true of carbon?
It can form both polar & nonpolar bonds
Why is ATP an important molecule in metabolism?
It provides energy coupling b/w exergonic & endergonic reactions
Consider the following reaction at equilibrium: C2O2 + H2O <--> H2CO3 What would be the effect of adding additional H2CO3?
It would drive the equilibrium dynamics to the left
Which of these classes of biological molecules does NOT include polymers? Carbohydrates Lipids Proteins Nucleic Acids
Lipis
What is true of metabolism in its entirety in all organisms?
Metabolism consists of all the energy transformation reactions in an organism
In living systems molecules involved in H bonding almost always contain either oxygen or nitrogen or both. How do you explain this phenomenon?
Oxygen & Nitrogen are elements with very high attractions for their electrons
When O2 is released as a result of photosynthesis, it is a direct by-product of___.
Splitting water molecules
Most cells can not harness heat to perform work because ___.
Temp. is usually uniform throughout the cell
For living organisms, which of the following is an important consequence of the 1st law of thermodynamics?
The organism ultimately must obtain all of the necessary energy for life from its environment
What statement correctly describes cis-trans isomers?
They have variations in arrangement around a double bond
Why are there several structurally different pigments in the reaction centers of photosystems?
This arrangement enables the plant to absorb light energy of a variety of wavelengths
The tertiary structure of a protein is the ___.
Unique 3D shape of the fully folded polypeptide
What is the best explanation for why vegetable oil is a liquid at room temperature while animal fats are solid?
Vegetable oil has more double bonds than animal fats
What is a FALSE statement concerning amino groups? Amino groups ___.
are nonpolar
Testosterone & estradiol are male & female sex hormones, respectively, in many vertebrates. In what way(s) do these molecules differ from each other? Testosterone and estradiol ___.
have different functional groups attached to the same carbon skeleton