cell bio
Why is a selectively permeable membrane so important to living things?
Which of the following molecules is most likely to cross the cell membrane directly by passive diffusion?
A steroid hormone
Which of the following is important in protein folding after the formation of a polypeptide?
Monomers are removed from polymers by ________ reactions.
Hydrolysis
Which of the following statements about self-assembly is false?
Self-assembly only occurs in structures composed of protein.
The chemical nature of each amino acid is determined by which of the following groups?
R group
Which of the following contributes to the stability of the DNA double helix?
hydrophobic interactions between aromatic bases at the center of the double helix
The two strands of DNA are held together by ________; thus, ________.
Experiments by Stanley Miller in the 1950s demonstrated that the first organic molecules on earth
could have formed abiotically in a reducing atmosphere containing hydrogen, methane, ammonia, and water vapor.
The size range of most plant and animal cells is
50-100 mm.
Which of the following is a defining characteristic of eukaryotic cells?
Eukaryotic cells are believed to have arisen
Which of the following accurately explains the relationship between bond energy and bond stability?
Bond energy is directly proportional to bond stability, such that the more stable a bond is, the more energy will be required to break it.
Which answer correctly shows the hierarchical nature of cellular structure from the simplest to the most complex?
small organic molecules, macromolecules, organelles, a cell
_________ facilitate the assembly of proteins but are NOT components of the protein or protein-containing structure.
Chaperones
Based on our current understanding, the first prokaryotes evolved around 3.5 billion years ago. What is our best estimate of when the first eukaryotes appeared?
2 billion years ago
Which of the following is a polysaccharide used for energy storage in animals?
Glycogen
Which theory proposes that mitochondria and chloroplasts were once free-living prokaryotic cells that were engulfed by ancestral eukaryotic cells, eventually forming a symbiotic relationship?
Endosymbiont theory
Which type of chemical bond involves the sharing of electrons between atoms and can be polar or nonpolar?
Covalent
Which of the following is an example of a hydrogen bond in a biological context?
The bond between complementary base pairs in DNA, such as adenine and thymine.
Hemoglobin consists of two pairs of alpha chains and two pairs of beta chains. This defines the structure of the molecule at which level of organization?
Quaternary
How do the gene transcription and translation machinery in Archaea compare to Bacteria and Eukaryotes?
Archaea's transcription and translation processes are more similar to Eukaryotes than to Bacteria
Which of the following best describes the RNA World Hypothesis?
RNA molecules were the first to perform both genetic and catalytic functions in early life forms.
Which of the following is the primary function of triglycerides in the body?
Providing energy storage
Which component of a phospholipid is hydrophilic?
Phosphate group
What is the primary role of cholesterol in the plasma membrane?
Modulating membrane fluidity and stability
Why are lipids considered more efficient for energy storage compared to glycogen?
Lipids provide more energy per gram and can be stored with minimal associated water.
Why is carbon considered the backbone of organic molecules?
It can form four stable covalent bonds, allowing the construction of complex molecules.
Water's role as a universal solvent is primarily due to:
Its polarity, which allows it to dissolve a wide variety of solutes.
Water is essential in maintaining the structure of biomolecules like proteins and nucleic acids because:
It forms hydrogen bonds that help maintain their three-dimensional structure.
What is the significance of chirality in biological molecules?
Chirality determines how molecules interact with biological systems, including enzymes and receptors.
Why are L-amino acids predominantly found in proteins?
The enzymes that synthesize proteins in living organisms are specific for L-amino acids.
DNA molecules are polymerized such that there are 5' and 3' orientations to the DNA strands; likewise proteins have an animo terminus and a carboxyl terminus. These structural features represent:
polymer directionality
The ends of amphipathic phospholipids are critical to forming lipid bilayers. How would membrane formation differ if you added a polar group to the end of the nonpolar tail of all phospholipids?
These altered phospholipids would most likely form a lipid monolayer.
Based on the principle of complementary base pairing in DNA, you would expect the percentage of __________ to be equal to the percentage of __________.
A;T
Two proteins associated with a rare neurodegenerative disorder have been sequenced. Protein A contains many polar amino acids with small regions containing nonpolar, hydrophobic amino acids. Protein B is rich in nonpolar, hydrophobic amino acids with only two small regions containing polar amino acids. What might this suggest about the two proteins?
Protein A may be a cytoplasmic protein and Protein B may be a membrane associate protein.
Which of the following pairs correctly matches the monomer with its polymer?
:
Nucleotides; nucleic acids
RNA and DNA differ
in that RNA contains ribose and DNA contains deoxyribose.
in that RNA contains uracil and DNA contains thymine.
A general trend in the structure of many biomolecules is
that the order and bonding of monomers form the basis for the secondary and tertiary structure of the polymer.