Weekly quizzes Flashcards
Living systems are incredibly diverse in size, shape, environment, and behavior. It is estimated that there are between 10 million and 100 million different species. Despite this wide variety of organisms, it remains difficult to define what it means to say something is alive. Which of the following can be described as the smallest living unit?
Cell
Changes in DNA sequence from one generation to the next may result in offspring that are altered in fitness compared with their parents. The process of change and selection over the course of many generations is the basis of ___________________
evolution
The __________ __________ is made up of two concentric membranes and is continuous with the membrane of the endoplasmic reticulum.
nuclear envelope
Which of the following statements about mitochondria is NOT true?
Mitochondria are thought to have originated from bacteria
Mitochondria contain their own DNA
Mitochondria have an inner and outer membrane
Mitochondria are not present in plant cells
Mitochondria generate chemical energy for the cell
Mitochondria are not present in plant cells
Which of the following statements about chloroplasts is NOT true?
Chloroplasts contain their own DNA
Chloroplasts have an internal stack of membranes that is enclosed by two other membranes
Chloroplasts are thought to have originated from mitochondria
Chloroplasts produce food molecules and generate oxygen
Chloroplasts are present in plant and algal cells
Chloroplasts are thought to have originated from mitochondria
What structure in an interphase cell contains ribosomal rRNA and proteins for the formation of ribosomes?
Nucleolus
Which of the following structures can be easily detected and resolved by fluorescence light microscopy?
Mitochondria and the nucleus
Which of the following organelle provides a safe place in the cell to carry out biochemical reactions that generate and breakdown harmful, highly reactive oxygen species?
Peroxisomes
Cell biologists employ targeted fluorescent dyes or modified fluorescent proteins in both standard fluorescence microscopy and confocal microscopy to observe specific details in the cell. Even though fluorescence permits better visualization, the resolving power is essentially the same as that of a standard light microscope because the resolving power of a fluorescent microscope is still limited by the __________________ of visible light.
wavelegnth
Zebrafish (Danio rerio) are especially useful in the study of early development because their embryos ___________________ .
are transparent
Which one of the following statements about the polypeptide backbone is FALSE?
a. It plays an important role in the formation of both the alpha helix and beta sheet, two common secondary structures.
b. It includes the amino acid side chains.
c. It includes the peptide bond formed between the amino group on one amino acid and the carboxyl group on another amino acid.
d. It contains a repeating sequence of the core atoms (N-C-C) in every amino acid
b
Which one of the following statements about protein folding is FALSE?
a. The protein’s amino acid sequence ultimately determines the 3-D shape of a protein.
b. Two or more alpha-helices with hydrophobic stripes can interact to form a coiled coil.
c. The distribution of polar and nonpolar amino acids in a folded protein is largely determined by hydrophobic interactions, which favor clustering of nonpolar side chains in the interior.
d. The amino acid side chains are involved in forming the hydrogen bonds that stabilize the alpha helix and beta sheet secondary structures
d
What is the best definition of a protein domain?
a. The location of a protein subunit within a multi-subunit enzyme
b. An alpha-helix
c. The region in a cell where a protein is located
d. A segment of a protein that can fold independently into its own compact, stable 3D structure
d
Which one of the following statements about protein binding sites is FALSE?
a. Binding sites are often located in a cavity on the protein surface
b. Each antibody contains three antigen binding sites, which can bind many different antigens non-specifically
c. All proteins can bind themselves and/or other molecules called ligands
d Some proteins can bind to themselves to form higher order macromolecules, and the shape of the macromolecules is determined by the location of the binding sites.
b
Protein folding can be studied using a solution of purified protein and a denaturant (urea), a solvent that interferes with noncovalent interactions. Which of the following is observed after the denaturant is removed from the protein solution?
The polypeptide returns to its original conformation.
The polypeptide adopts a new, stable conformation.
The polypeptide remains denatured.
The polypeptide forms solid aggregates and precipitates out of solution.
The polypeptide returns to its original conformation.
The variations in the physical characteristics between different proteins are influenced by the overall amino acid compositions, but even more important is the unique amino acid ______________.
sequence
Ras is a small protein that functions in many signaling pathways. In its active form, with GTP bound, Ras transmits a signal that leads to cell proliferation. In its inactive form, with GDP bound, the signal is not transmitted. Mutations in the gene for Ras are found in many cancers. Which type of mutation in Ras is MOST likely to contribute to uncontrolled cell growth?
A mutation that increases the binding of Ras to GTP
A mutation that decreases the binding of Ras to GTP
A mutation that prevents Ras from being made
A mutation that increases the binding of Ras to GDP
A mutation that increases the binding of Ras to GTP
How does phosphorylation control protein activity?
a. The addition of a phosphate group can induce a conformational change in a protein
b. The phosphate group, with its two negative charges, prevents other negatively charged molecules from interacting with a protein
c. Phosphorylation always activates a protein
d. The addition of a high energy phosphate group adds energy to a protein
a
Which one of the following methods is the BEST way to assess the number and sizes of proteins in complex mixture?
gel electrophoresis
The attachment or removal of covalent modifications can control what aspects of a protein?
Its stability
Its behavior, activity, stability and/or location inside the cell
Its behavior or activity
Its location inside the cell
all
Complete the sentence: In a DNA double helix, _____________
the two DNA strands run antiparallel.
the two DNA strands are identical.
adenosine pairs with guanine.
thymine pairs with cytosine.
the two DNA strands run antiparallel
The process of sorting human chromosome pairs by size and morphology is called karyotyping. Which of the following questions would NOT be answered by using karyotyping?
Do any chromosomes contain mutations in their nucleotide sequences?
Is the individual genetically female or male?
Do any of the chromosomes contain pieces that belong to other chromosomes?
Does the individual have an extra chromosome?
a, any mutations
The chromosomes we typically see in images are isolated from mitotic cells. These mitotic chromosomes are in the most highly condensed form. Interphase cells contain chromosomes that are less densely packed and ______________ .
occupy discrete territories in the nucleus
Which of the following human cells contains a gene that specifies eye color?
Cells in the eye, the heart and the brain
Cells in the eye
Cells in the heart
Cells in the brain
all
