AP Bio Midterm

Acetyl CoA is the correct answer because it is the intermediary metabolite that enters the citric acid cycle and is formed by the removal of a carbon (CO2) from one molecule of pyruvate. Acetyl CoA is a crucial molecule in cellular respiration as it carries the acetyl group, derived from pyruvate, into the citric acid cycle where it can be further oxidized to produce energy.

Feedback inhibition is the mechanism in which the end product of a metabolic pathway inhibits an earlier step in the pathway. This is a regulatory mechanism that helps maintain homeostasis by preventing the overproduction of a particular molecule. When the concentration of the end product reaches a certain threshold, it binds to an enzyme involved in an earlier step of the pathway, causing a conformational change that inhibits the enzyme's activity. This feedback loop helps regulate the rate of the metabolic pathway and ensures that the production of the end product is balanced with the cell's needs.

Exergonic reactions are characterized by a net release of free energy. This means that the energy released during the reaction is greater than the energy required to initiate the reaction. In other words, the products have less total energy than the reactants, resulting in a release of energy. This is in contrast to endergonic reactions, which require an input of energy from the surroundings in order to proceed. Therefore, the statement "The reaction proceeds with a net release of free energy" is true for all exergonic reactions.

Catabolism is the correct answer because it specifically refers to the cellular process of breaking down large molecules into smaller ones. Dehydration, metabolism, catalysis, and anabolism are not as precise in describing this process. Dehydration refers to the removal of water, metabolism is a broad term encompassing all chemical reactions in the body, catalysis refers to the acceleration of chemical reactions, and anabolism refers to the building up of larger molecules from smaller ones. Catabolism, on the other hand, focuses specifically on the breakdown of large molecules into smaller ones.

The correct answer is the difference in H+ concentrations on opposite sides of the inner mitochondrial membrane. This is because during respiratory oxidative phosphorylation, electrons from NADH are transferred through the mitochondrial electron transport chain, creating a proton gradient across the inner mitochondrial membrane. This proton gradient drives the synthesis of ATP by ATP synthase, as the flow of protons back into the mitochondrial matrix powers the phosphorylation of ADP to ATP.

The statement that is false is "The P680 chlorophyll donates a pair protons to NADPH, which is thus converted to NADP+". In photosystem II, the P680 chlorophyll does not donate protons to NADPH. Instead, it donates electrons to the electron transport chain, which eventually leads to the production of NADPH. NADP+ is reduced to NADPH by accepting electrons, not protons.

Yeast cells are frequently used as hosts for cloning because they are easy to grow and they have plasmids. Yeast cells are single-celled organisms that can be easily cultured in the laboratory, making them a convenient choice for cloning experiments. Additionally, yeast cells naturally contain plasmids, which are small, circular pieces of DNA that can be easily manipulated and used for cloning purposes. Therefore, both options A and C are correct.

Increasing the substrate concentration in an enzymatic reaction could overcome competitive inhibition. Competitive inhibition occurs when a molecule similar in structure to the substrate binds to the active site of the enzyme, preventing the substrate from binding and inhibiting the reaction. By increasing the concentration of the substrate, the chances of the substrate binding to the active site of the enzyme increase, reducing the impact of the competitive inhibitor and allowing the reaction to proceed.

Proton-motive force refers to the transmembrane proton concentration gradient. This gradient is created by the movement of protons across a membrane, such as the inner mitochondrial membrane, and is essential for various cellular processes, including ATP synthesis. The proton-motive force drives the movement of protons back across the membrane through ATP synthase, which generates ATP. Therefore, the correct answer is the transmembrane proton concentration gradient.

A cell surface protein that requires transport from the ER is most likely to have a small protein called ubiquitin attached to it. This is because ubiquitin is often attached to proteins that need to be transported or degraded by the cell. The attachment of ubiquitin marks the protein for degradation or for transport to specific cellular compartments. In this case, the cell surface protein needs to be transported from the ER, so it is likely that ubiquitin will be attached to it to facilitate its transport.

If a thylakoid is punctured and the interior of the thylakoid is no longer separated from the stroma, it will directly affect the synthesis of ATP. This is because the thylakoid membrane is where the electron transport chain and ATP synthase are located, which are responsible for the production of ATP during photosynthesis. Without the intact thylakoid membrane, the proper functioning of these processes would be disrupted, leading to a decrease in ATP synthesis.

Restriction enzymes are used to produce RFLPs (Restriction Fragment Length Polymorphisms). These enzymes recognize specific DNA sequences and cleave the DNA at those sites. This results in the generation of DNA fragments of different lengths, which can be separated and analyzed to identify genetic variations or polymorphisms. DNA ligase is responsible for joining DNA fragments together, reverse transcriptase is used to synthesize DNA from RNA, RNA polymerase is responsible for synthesizing RNA from a DNA template, and DNA polymerase is involved in DNA replication and repair. However, none of these enzymes are directly involved in producing RFLPs.

Without passing light through a prism, the bacteria would be relatively evenly distributed along the algal filaments. This is because passing light through a prism causes the light to separate into its different wavelengths, which can have different effects on the bacteria. Without this separation of light, the bacteria would not experience any specific changes in their distribution along the algal filaments.

Engelmann concluded that the bacteria congregated in the areas illuminated by red and blue light because these areas had the most oxygen being released.

Reverse transcriptase is the enzyme used to make complementary DNA (cDNA) from RNA. This enzyme is capable of synthesizing a DNA strand using an RNA template. It catalyzes the reverse transcription process, where RNA is used as a template to produce a complementary DNA strand. This technique is commonly used in molecular biology research to study gene expression and analyze RNA molecules.

The correct answer is non-protein coding DNA that is transcribed into several kinds of small RNAs with biological function. This accounts for most of the rest of the sequences because it has been discovered that a significant portion of the genome is transcribed into non-coding RNAs, which play important regulatory roles in gene expression and other cellular processes. These small RNAs have been found to have various biological functions, such as regulating gene expression, silencing genes, and controlling protein production. This discovery has challenged the previous notion that non-coding DNA was "junk" DNA with no purpose.

When a molecule is phosphorylated, it means that a phosphate group has been added to it. This addition of a phosphate group increases the chemical reactivity of the molecule, making it more likely to participate in chemical reactions. This increased reactivity allows the molecule to be involved in cellular work, such as energy transfer or signal transduction. Therefore, a phosphorylated molecule is considered to be "primed" and ready to perform cellular functions.

Many transcription factors in eukaryotes are known to have DNA binding domains, which allow them to bind to specific DNA sequences. Additionally, transcription factors often have other domains that are specific for binding to various molecules. Therefore, it would be expected that many transcription factors would be able to bind to other transcription factors, as they interact with each other to regulate gene expression.

Targeting siRNAs to disable the expression of an allele associated with autosomal dominant disease would likely gain the most from non-coding RNAs. Autosomal dominant diseases are caused by a mutation in a single copy of a gene, and targeting siRNAs can specifically inhibit the expression of the mutated allele, potentially reducing or eliminating the symptoms of the disease. This approach holds promise for developing targeted therapies for a wide range of genetic disorders.