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Macromolecules
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1We know from Chargaff’s rules that A binds T and G binds C. Hydrogen bonding is important in those pairings: [blank_start]three[blank_end] H bonds for G-C and [blank_start]two[blank_end] H bonds for A-T. G-C bonds are, therefore, harder to break than A-T pairs.
- Athree
- Btwo
2Cellular RNA is (usually) single stranded, with no double helix. Complex 3-D structures can form from rules governed primarily by Watson-Crick base pairing: A to U; G to C. Chargaff's rules do not apply for single strands of RNA because there is no pairing across the entire length.
- ATrue
- BFalse
3The alpha helix is the most common form of secondary structure. The regular helical pattern is often broken by [blank_start]proline[blank_end]. The beta sheet features regions of chains interacting in a folded pleated pattern. It's dependent on hydrogen bonds. Parallel indicates chains run in the same direction ([blank_start]N[blank_end]-terminus to [blank_start]C[blank_end]-terminus) and antiparallel indicates the chains run in opposite directions. The beta sheet is also often broken by [blank_start]proline[blank_end], since [blank_start]proline[blank_end] contains a [blank_start]ring[blank_end] structure that tends to end regions of secondary structure.
- Aproline
- BN
- CC
- Dproline
- Eproline
- Fring
4The [blank_start]native[blank_end] (folded) state of a protein always assumes the [blank_start]lowest[blank_end] energy conformation in cellular conditions. The native state is determined primarily by [blank_start]weak[blank_end] interactions. The native state is usually 20-65 kJ/mol lower than the denatured (unfolded) state.
- Alowest
- Bnative
- Cweak
5[blank_start]Leucine zippers[blank_end] are made up of antiparallel alpha-helices held together by hydrophobic interaction between [blank_start]leucines[blank_end].
- ALeucine zippers
- Bleucines
6[blank_start]Motif[blank_end]: Stable arrangement of secondary structure, also called “ supersecondary structure” or “fold.”
[blank_start]Domain[blank_end]: Globular region of a protein. The protein below has distinct domains as indicated by the different colors.- AMotif
- BDomain
7ATP-binding proteins typically do more than just bind ATP. Often, one domain binds ATP, and another domain catalyzes a reaction or carries out some function. The ATP-binding domain is frequently called a [blank_start]nucleotide-binding domain[blank_end] (or NBD).
- Anucleotide-binding domain
8SSBs ([blank_start]single strand DNA binding proteins[blank_end]) recognizes a [blank_start]conformation[blank_end], not a sequence. SSB recognizes single stranded regions during replication or recombination.
- Asingle strand DNA binding proteins
- Bconformation
9The lambda repressor, like many DNA-binding proteins, bind to specific sequences. Its recognition helix is an alpha-helix that fits neatly into the major groove of DNA. The major groove’s hydrogen bond acceptors allow proteins to distinguish sequence--it's tougher in the minor groove (more on that in chapter 6). The N-terminus of the alpha helix is positively charged and interacts with the negative phosphate backbone of DNA.
- ATrue
- BFalse
10A [blank_start]helix[blank_end]-[blank_start]turn[blank_end]-[blank_start]helix[blank_end] motif has two helices that are somewhat perpendicular and connected by a short loop. The recognition helix binds a specific DNA sequence, and the other helix helps [blank_start]stabilize[blank_end] the interaction.
- Ahelix
- Bturn
- Chelix
- Dstabilize
11The TATA-binding protein uses a beta sheet instead of an alpha-helix. The beta sheet binds the TATA-box of a promoter in the [blank_start]minor[blank_end], not [blank_start]major[blank_end] groove. The protein is important in transcription initiation.
- Aminor
- Bmajor
12mRNA-binding proteins bind mRNA based on the lack of 3-D structure. Most mRNA molecules lack 3-D structure. Others bind specific structures. The RRM binds a [blank_start]stem[blank_end]-[blank_start]loop[blank_end] RNA structure that develops from internal base pairing and is commonly found in RNA-binding proteins. The motif is about 80-90 amino acids long and forms four antiparallel beta strands. This motif is also refered to as the RNP ([blank_start]ribonuclear protein[blank_end])motif.
- Aribonuclear protein
- Bstem
- Cloop
13[blank_start]Allostery[blank_end] in proteins usually involves the binding of a molecule at one domain affecting the shape of a molecule’s other domain. For instance, in hemoglobin, the binding of oxygen to one subunit facilitates oxygen binding to the other three subunits.
- AAllostery
14Recall that [blank_start]kinases[blank_end] transfer phosphoryl (PO3) groups, and [blank_start]phosphatases[blank_end] hydrolyze phosphate groups (PO4). Some proteins are only active when phosphorylated; other proteins are only active when dephosphorylated. Therefore, kinases can turn enzymes on or off, and phosphatases can turn enzymes on or off. Controlling the activity of kinases and phosphatases control those on/off switches.
- Aphosphatases
- Bkinases
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- Molecular Biology (Unit 2) Quiz on Macromolecules , created by Brooks Johnson on 03/06/2020.
- Author
- Brooks Johnson
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- English
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