Which of the following best describes how carrier proteins move molecules across
ID: 199601 • Letter: W
Question
Which of the following best describes how carrier proteins move molecules across the 1) membrane? A) selectively bind the molecule to be transported, used ATP to change configuration, and relaease it on the other side B) use an ion gradient to power movement of molecules across a membrane C) selectively bind the molecule to be transported, change configuration, and release it on the other side D) couple ions or molecules together to drive each other's transport across a membrane Which of the following classes of amino acids is buried within the folded structure of the 2) protein in the cytoplasm of a cell? Explain your answer on another piece of p aper. A) Basic B) Nonpolar C) Polar D) Acidic You have isolated a protein from your culture of yeast cells, and analyzed its structure. You find that the protein contains several alpha helices, some polar regions, and non-polar regions. Where in the cell is it most likely found? Explain your answer on another piece of paper. 3) A) embedded in a cell membrane B) in the perinuclear space C) associated with a cell membrane D) in the cytoplasm E) in the nucleus Which of the following are involved in forming the tertiary structure of proteins?Explanation / Answer
Q1-Carrier protein
Answer- C Carrier proteins are the integral proteins which extend into the lipid bilayer of cell membrane, and serve as channels for water soluble substances such as glucose and electrolytes. When transporting the solutes, carrier proteins bind solute on one side of a membrane, undergo conformational changes, and release them on the other side of the membrane. These proteins can mediate both active and passive transport. During the passive transport, molecules diffuse along the concentration gradient without consuming energy. Active transport is the movement of solute particles against the concentration gradient, and it needs energy. Carrier proteins act like enzymes. They bind only specific molecules, and the mode of attachment is similar to that between the active site of an enzyme and its substrate. Examples for some carrier proteins include; Glucose Transporter 4 (GLUT-4), Na+-K+ ATPase, Ca2+ ATPase etc.
Q2- About amino acids
Answer -B As the cytoplasm inside the cell mostly contains water, almost all proteins have nonpolar resides buried deep inside the folded structure. It gives the stability to the quaternary structure of the protein by stablizing it with hydrobhobic interactions, wheras outside is the polar and the charged amino acids.
Q-3 About helix
Answer-D) Cytoplasm
Protein folding is certainly a complex issue that, at present, isn't fully understood. However, the primary sequence of the polypeptide contributes strongly to this type of secondary structure. For each amino acid, there is a defined "helical propensity", which is a number that defines how likely a certain amino acid is to exist in an alpha helix. A series of amino acids with high helical propensity in the context of a protein will likely form an alpha helix because the strain on their phi and psi angles is lowest in this conformation. Conversely, proteins which do not contain a series of amino acids which can conform to the constraints of an alpha helix, will likely not form one, or not form a stable one. In this case, they may be more stable as a beta sheet, or they may form no secondary structure at all.
Though, primary sequence is only a small part of the story. For many organisms, there are proteins which assist in the folding of newly created proteins (chaperones). In short, proteins generally seek to assume the conformation that is most thermodynamically stable. For some proteins, like green fluorescent protein (GFP) this means folding into a pure beta sheet. For others, like insulin, alpha helices are the most favorable. It really depends on the environment where the protein is "born" and the sequence of events that follow as the protein comes off the ribosome.Hence the cytoplasm is the best place to find the protein having alpha helices.
Question 4 - No options
Related Questions
drjack9650@gmail.com
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.