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Which of the following inhibitors will block the active site of a protein?
Proteins can be inhibited in numerous ways by different types of inhibitors. Competitive inhibitors will compete with substrate for the active site to block the protein from performing its function. If there is enough substrate and very little competitive inhibitor, proteins will perform their functions almost as if there were no competitive inhibitors.
In contrast, allosteric inhibitors bind to regions of the protein away from the active site, but change the shape of the active site such that substrate cannot bind. Since there is no direct competition, increasing substrate concentration cannot overcome allosteric inhibition. Non-competitive inhibition is a type of allosteric inhibition. Uncompetitive inhibition occurs when the inhibitor will only bind to the enzyme-substrate complex, locking the substrate in place and preventing other substrates from binding.
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The active site of a protein works in a way similar to __________.
The active site on a protein is the area where a substrate can attach. This relationship is most often described using a metaphor of a lock and a key because each protein has an active site specific to one substrate much like a lock can only be opened by one key.
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__________ modification of an enzyme permits an effector molecule to bind the enzyme at a site other than the active site. This can modulate the enzyme's activity to make it either more or less active.
The key here is to know that if something binds the enzyme at a location other than the active site, the type of modification is defined as allosteric. The other words more generally describe things that can bind to receptors, enzymes, etc., but the best and most specific answer is "allosteric."
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Which of the following best describes why an enzyme loses its catalytic capabilities when exposed to extremely high temperatures?
It is important to know that when exposed to high temperatures, all proteins become denatured, and lose their native shape/conformation.
This has nothing to do with the activation energy of the reaction (eliminating that answer). While some substrates may be degraded at high temperatures, the word "all" renders this answer incorrect, nor does this describe what happens to the enzyme. Covalent modificatinos can change enzymatic function, but do not have anything to do with higher temperature.
The correct answer is that the enzyme itself is denatured, thus changing the shape and the way the active site is shaped, resulting in an inability to efficiently bind its substrate. The structure of the enzyme is dictated by intermolecular forces, which are susceptible to interference from temperature changes (unlike covalent bonds).
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Which mode of enzyme inhibition involves an inhibitor molecule binding the active site of the enzyme?
Competitive inhibition is the only type of inhibition in which the inhibitor molecule directly binds the active site of the enzyme, thereby 'competing' with the actual substrate for location on the enzyme. The other choices involve binding elsewhere on the enzyme (non-competitive) or binding the enzyme-substrate complex but not an isolated enzyme (mixed), but none of them describe binding the active site except for competitive.
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Which of the following is/are example(s) of nucleic acids?
Nucleic acids include DNA and all forms of RNA (mRNA, tRNA, rRNA, and htRNA). Note that the different types of RNA have the same base structure, but serve different functions. Messgener RNA (mRNA) is used as the template for protein translation. Transfer RNA (tRNA) transports amino acid residues to the ribosome during translation to aid in polypeptide elongation. Ribosomal RNA (rRNA) is used to form the structure of the ribosomal subunits. Heternuclear RNA (htRNA) is the original product of transcription, and is found in the nucleus prior to post-transcriptional modifications.
Glucose is a carbohydrate, and cholesterol is a lipid.
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Which of the following contains and controls the use of DNA?
During most of the cell cycle, DNA is found as chromatin. Chromatin is a mass of DNA and associated proteins. Depending on the state and activation of those proteins and on how tighly packed the DNA is around the proteins, certain genes can be turned on or off.
Chromosomes form from condensed chromatin only during mitosis (specifically during prophase), and are absent during most of the cell's cycle. Genes are units of heredity that encode the information needed to specify the amino acid sequence of proteins. The gene is the functional segment of DNA located at a specific place, or locus, on a chromosome. The cytoplasm is the material contained in the cell membrane and outside the nucleus. The nucleus is a membrane-bound organelle that contains the cell's genetic material.
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Operons __________.
An operon is a segment of DNA that is under the control of a single promoter. For example, if there are three genes required for breaking down a sugar in an operon, they will all be activated together. This makes sense, as there is no sense in activating only one or two of these genes, since all three are required to break down the sugar. For example, the control element that turns on the operator can be the sugar itself. It should make sense that the genes required to break down a sugar are only turned on if that sugar is present.
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Genes are said to be expressed when they are __________.
Genes are expressed when their gene products are made, to do this transcription and translation must occur to synthesize the protein which is coded for by the DNA.
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The correct pairing of nucleotide bases in DNA are __________.
The nucleotides in DNA always pair the same way; A with T and G with C. This is due to the chemical structure of each base; adenine and thymine form two hydrogen bonds when pairing, and guanine and cytosine form three. The other important thing to remember is that there is a different nitrogen base in RNA called uracil; uracil is not found in DNA, so pay attention to which molecule the question is asking about.
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How can synteny help with understanding chromosomes?
Synteny is the conservation of order of genes. Being able to see conserved blocks in genes when comparing two chromosomes of the same species, it indicates that at some time in evolutionary history, these blocks originated from a hypothetical common ancestor. Genes that are highly conserved among species are usually vital to the organism's viability. For example, the genes required for glycolysis to occur are required in almost all organisms.
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Which of the following answers best describes the human genome.
The human genome can be described as a chain of nucleotides that is 3.2 billion base pairs long. Twenty-three different lengths that are called chromosomes segment this string of material. Genes further segment the chromosomes. The chromosomes vary in length and so do their genes. DNA of a gene on a certain part of a certain chromosome can be transcribed into mRNA, which is then translated into protein. The number of genes in our genome has been highly contested. It was originally believed that humans had over 100,000 genes. This number declined as we learned more about our genome and was more or less standardized to be around 25,000 upon completion of the Human Genome Project.
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A chromosome is a molecule of __________.
A chromosome is one molecule of DNA. It contains genetic information required for cell replication and the passing down of genetic information. Humans have 23 pairs of chromosomes, with one chromosome per pair from the mother, and the other from the father.
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A human’s diploid number is 2n=46. What is the haploid number of a human gamete?
Humans have 23 homologous pairs of chromosomes, which adds up to 46 chromosomes total. Diploid cells have two copies of each chromosome (one from the mother, one from the father). A gamete is haploid, meaning it only contains one copy of each chromosome. The gametes (haploid) will fuse in a process known as fertilization in order to form a diploid zygote.
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Which of the following best describes an allele?
An allele is a variant or alternative form of a gene or gene locus. Humans are diploid—we have two alleles at each genetic locus. One allele is inherited from the mother and one allele comes from the father. Sometimes different alleles can lead to different phenotypic traits (e.g. eye color); however, most genetic variations result in little to no observable variation. An organism is considered homozygous if it possesses two of the same alleles at a particular locus. If the alleles are different, then the organism is considered heterozygous.
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DNA is found in which of the following?
DNA—deoxyribonucleic acid—is found in chromosomes within a cell’s nucleus. A complete set of DNA (i.e. 46 chromosomes) is called a genome. DNA contains instructions that make humans different from other species and other individuals. DNA provides instructions for all the proteins that the body makes and is passed from adults to offspring. DNA cannot get out of the nucleus; however, RNA can. RNA is used to get the instructions from DNA out of the nucleus and into the site of protein synthesis: the ribosomes within the cytoplasm. Proteins are made of amino acids and determine the structure and function of all of the body’s cells.
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A genome is best described as which of the following?
Based on the definition of genome, it is the entire set of DNA found within all the chromosomes an organism contains. The human genome is contained on 23 pairs of chromosomes, which code for about 25,000 genes.
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Which of the following is not true about DNA?
DNA nucleotides bond via hydrogen bonding to form the double helix structure. DNA is negatively charged due to the phosphates and binds to histones to form compact chromosomes in the nucleus.
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How are RNA and DNA similar?
Although RNA and DNA have some key differences that result in different functions, they also have some key similarities. Both are composed of nucleotide monomers linked together by phosphodiester bonds. They are also both read in the 5'-3' direction. It is important to know that the backbone of both DNA and RNA is made by phosphodiester bonds, but it is hydrogen bonds that bind two strands to DNA together to form the double-helix.
DNA and RNA both use adenine, cytosine, and guanine, but only DNA uses thymine and only RNA uses uracil. Only DNA is double-stranded; RNA is single-stranded. Deoxyribose, in DNA, is deoxygenated at the 2' carbon, but ribose in RNA is oxygenated.
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Which of the following bases is replaced by uracil during transcription?
DNA uses four nitrogenous bases: adenine, thymine, cytosine, and guanine. Adenine residues bond to thymine residues, and cytosine binds to guanine.
During transcription, DNA is used as a template to generate mRNA. During this process, bases are matched to the DNA template and used to build a single strand of RNA. In RNA, there are also four nitrogenous bases: adenine, cytosine, guanine, and uracil. Thymine is not found in RNA.
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