fle5 Flashcards
Which of the following biomolecules lower the energy of activation of a biological reaction?
I. DNA polymerase
II. DNA ligase
III. Telomerase
A) I only B) II only C) I and II only D) I, II, and III
D- they are all enzymes so they all lower activation energy
When considering a double-reciprocal Lineweaver-Burk plot, the binding affinity between the substrate and the enzyme is best approximated by the magnitude of the:
A) x-intercept. B) y-intercept. C) inverse of the x-intercept. D) inverse of the slope.
c: x intercept is 1/Km so binding affinity= Km = invert of x intercept.
If the plasma membrane of a human muscle cell is subjected to detergents and enzymatic hydrolysis, which monomeric components will be found in the resulting solution?
I. Amino acids II. Fatty acids III. Nucleic acids IV. Carbohydrates A) II only B) I and II only C) I, II, and IV only D) I, II, III, IV
C
Which enzyme does NOT catalyze an irreversible step of glycolysis in cancer cells?
A) Hexokinase B) Phosphoglycerate kinase
C) Phosphofructokinase D) Pyruvate kinase
Answer B is correct. There are three reactions in glycolysis that have such large negative DG values in the forward direction that they are essentially irreversible. These are the three steps that must be bypassed using alternative reactions and enzymes during gluconeogenesis (the synthesis of glucose from pyruvate, an approximate reversal of glycolysis). The three irreversible steps are catalyzed by: hexokinase (a.k.a., glucokinase), phosphofructokinase, and pyruvate kinase. Therefore, Answers A, C and D are incorrect because these are enzymes that catalyze irreversible steps of glycolysis. Answer B, phosphoglycerate kinase, catalyzes the conversion of 1,3-bisphosphoglycerate to 3-phosphoglycerate. This is a step of glycolysis, but it is reversible. Therefore, Answer B is the correct answer to this NOT question type.
what are the irreversible step of glycolysis in cells?
hexokinase, phosphofructokinase and pyruvate kinase
what is geometry of atom surrounded by 6 bonds?
octahedral
Two wires with opposing current are placed near one another. In this arrangement, the magnitude of the:
A) force created by the magnetic fields will be zero.
B) force created by the magnetic fields will be at a maximum. C) magnetic field, B, will cause the wires to attract one another. D) magnetic field, B, will cause the wires to repel one another.
D
The strength of the dipole moment generated in a polar-covalent molecule can be calculated using which two variables? A) Charge and atomic size B) Electronegativity and atomic size C) Charge and distance D) Electronegativity and atomic number
Answer C is the correct choice. Option C is the only answer that takes distance into account. The relevant formula for calculating dipole moment is helpful, but not necessary to answer the question: µ = qr, where µ is the dipole moment, q is the charge, and r is the distance. The strength of the dipole is a function of both the charge and the distance across which that charge acts. Answer A should be eliminated because it is only half right: the charge is used directly to calculate the strength of the dipole, but atomic size is not. Answers B and D can be eliminated because electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons. This does not appear in the relevant equation and cannot be used to calculate the dipole moment.
London dispersion forces are the major contributor to intermolecular attractions between: A) nonpolar molecules. B) polar-covalent molecules. C) ions. D) hydrogen bonds.
Answer A is correct. London dispersion forces, considered a part of van der Waals forces, are the weakest type of intermolecular interaction. They occur between any two molecules that are very close to one another, but are most relevant to nonpolar molecules because they are the only intermolecular attraction experienced by nonpolar molecules. London dispersion forces occur due to instantaneous induced dipoles resulting from short-term changes in the location of electrons. For this reason, they are sometimes called “induced dipole-induced dipole” interactions. Answer B describes a dipole-dipole intermolecular interaction. Answer C is an example of an ionic interaction. Answer D, hydrogen bonding, occurs when the dipole created by a hydrogen bound to an electronegative atom (F, O or N) causes a strong intermolecular attraction.
When antidiuretic hormone is acting on the collecting tubules of the kidney in response to acute dehydration, the osmolarity of the ascending limb of the Loop of Henle will:
A) remain constant. B) increase. C) decrease. D) oscillate
Choice C is the correct answer. When a person becomes dehydrated, the brain secretes antidiuretic hormone (ADH), which increases water reabsorption at the collecting ducts. Reabsorption occurs through pores (aquaporin proteins) that are opened up in the collecting ducts, allowing water to pass into the medulla. As a result, there will be more water in the medulla. A more dilute medulla shifts the equilibrium between the filtrate in the ascending limb and the medulla, driving more ions out of the ascending limb (Note: recall that the ascending limb is impermeable to water, but highly permeable to ions). This increased removal of ions decreases the osmolarity of the filtrate in the ascending limb, so choice C is the correct answer.
what type of saccharides can humans not digest?
B linked saccharides CANNOT be digest by humans
saccharides are sugars (mono, poly, saturated,..)
Facilitated diffusion through the plasma membrane moves a substance:
A) down its concentration gradient and requires energy. B) down its concentration gradient and releases energy.
B
The primary role of oxygen in aerobic cellular respiration is to:
A) oxidize glucose. B) enter glycolysis. C) donate electrons to the electron transport chain. D) accept electrons from the electron transport chain.
D - so that protons can be pumped out
Ribosomes bound to the rough endoplasmic reticulum:
A) are enclosed within a dual bilayer membrane. B) synthesize proteins primarily used inside the cell. C) are identical to ribosomes found in prokaryotic cells. D) synthesize hydrolytic enzymes and secretory proteins.
Answer D is correct. Ribosomes bound to the rough endoplasmic reticulum in eukaryotic cells synthesize hydrolytic enzymes that function in the lysosomes, or proteins that are secreted by the cell.
Which of the following is a potential acetylation agent found in the Tip60 active site?
A) Acetate ion B) Acetamide C) Acetic anhydride
D) Acetyl-CoA
D- The question asks for an acetylating agent that could be found in the active site of Tip60. Acetic anhydride (Answer C) is an acetylating agent used in laboratory organic synthesis, but is not a natural biological molecule in vivo. Acetamide (Answer B) contains an amide linkage that is stable due to resonance and therefore unlikely to donate an acetyl group. Acetate ion (Answer A) is an end product of metabolism and is not used as an acetylating agent. Acetyl-CoA (Answer D) is commonly used by enzymes in the body for acetylation reactions as the carbonyl carbon is easily attacked by the nucleophilic nitrogen of an amino acid residue.
For an enzyme catalyzed reaction, initial reaction velocity is linearly related to which variable?
A) Solution pH B) Enzyme concentration
C) Temperature D) Substrate concentration
Answer B is correct. The relationship between product formation and initial enzyme concentration is proportional, while the relationship between product formation and initial substrate concentration is not. In the Michaelis-Menten Equation, the numerator includes a product of [S] and the denominator includes a sum of [S], which means the relationship between velocity and [S] cannot be linear.
This eliminates Answer D. Enzyme activity has a maximum pH below and above which activity drops, eliminating Answer A. Enzyme activity has a maximum temperature below and above which activity drops, eliminating Answer C. Furthermore, enzymes quickly become denatured at elevated temperatures. Answer D is incorrect because, as the substrate concentration increases, the initial reaction velocity levels off. Students should be familiar with the common graph of V0 vs [S], which is hyperbolic, not linear. It approaches an asymptote at Vmax.
During DNA replication, which enzyme removes RNA nucleotides from the primer and adds equivalent DNA nucleotides to the 3’ end of Okazaki fragments?
A) Helices B) Primase C) Ligase D) DNA polymerase
D