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Connect Assignment Week 7 exam
Although a eukaryotic cell membrane can contain many different lipids, they can be classified in three groups: glycerol phospholipids, ___________ , and _________________
. When answering the question think about the lipids found in membranes, not about all the lipids that an organism makes! - answer โ
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sphingolipids sterols Cellular __________ are said to be selectively________ because they allow some substances to pass through easily while other substances pass through very slowly or not at all. - answer โ
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membrane permeable Choose the three groups of lipids found in eukaryotic cells. Integral bilayer lipids
Triglycerides Sphingolipids Sterols Glycerol phospholipids - answer โ
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Glycerol phospholipids Sphingolipids Sterols Compared to the ER membrane, the plasma membrane contains more of which of the following (choose all that apply)? Sphingomyelin
Only carrier proteins have a hydrophilic interior channel. Only carrier proteins can facilitate net movement of a substance down its concentration gradient. Only carrier proteins actually bind to the substance being transported. Only carrier proteins are selective for one type of molecule. - answer โ
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Only carrier proteins actually bind to the substance being transported. How does lipid composition affect membrane fluidity? Saturated fatty acids tend to make the membrane less fluid because they pack together well.
Lipid composition has no effect on the fluidity of membranes. Unsaturated fatty acids tend to make the membrane less fluid because kinks introduced by the double bonds keep them from packing together well. Sterols, such as cholesterol, can either increase or decrease membrane fluidity depending on temperature.
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Saturated fatty acids tend to make the membrane less fluid because they pack together well. Sterols, such as cholesterol, can either increase or decrease membrane fluidity depending on temperature. Ion _____________ have a hydrated interior that spans the membrane and allows ions to diffuse through. - answer โ
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channels Many substances that are repelled by the hydrophobic interior of the lipid bilayer can readily diffuse across the plasma membrane with the help of specific ________ proteins or _________
Partially permeable Hydrophobic Amphipathic - answer โ
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Selectively permeable Select all that apply Identify the four main components of all eukaryotic membranes. Lipid bilayer Interior protein network Actin filaments
Transmembrane proteins Cell surface markers Extracellular matrix - answer โ
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Lipid bilayer Interior protein network Lipid bilayer Interior protein network Select the accurate statements concerning membrane fluidity. The degree of membrane fluidity varies depending on the composition of the membrane.
They are repelled by the hydrophobic interior of the lipid bilayer. They can easily cross the plasma membrane without the help of special transport proteins. - answer โ
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They interact well with polar molecules. They are repelled by the hydrophobic interior of the lipid bilayer. Select the true statements about cell membranes. The surface (the side facing the cytoplasm or the extracellular fluid) of the phospholipid bilayer is hydrophobic. The degree of membrane fluidity varies depending on the composition of the membrane.
All membranes have essentially the same composition and degree of fluidity. Individual lipids and unanchored proteins are relatively free to move around laterally within the lipid bilayer. - answer โ
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The degree of membrane fluidity varies depending on the composition of the membrane. Individual lipids and unanchored proteins are relatively free to move around laterally within the lipid bilayer. The cytoplasm contains ions and molecules dissolved in
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water The ER membrane is typically more fluid than the plasma membrane and it contains more curvature. Why? The ER membrane contains mainly sphingolipids.
Dark-field Phase contrast Fluorescent Electron - answer โ
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Electron When a channel protein or carrier protein assists in diffusion, which of the following is observed? Simple diffusion Endocytosis Active transport
Facilitated diffusion Dialysis - answer โ
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Facilitated diffusion When phospholipids are placed in water, they spontaneously form a bilayer with which of the following? The nonpolar heads in the interior and the polar tails on the surface The nonpolar heads on the surface and the polar tails in the interior The nonpolar heads in one layer and the polar tails in the other layer
Unbranched chains Branched chains 5-sided rings - answer โ
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A bilayer Which method of microscopy is illustrated in this drawing? Confocal microscopy Transmission electron microscopy Freeze-fracture microscopy
Scanning electron microscopy - answer โ
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Freeze- fracture microscopy Which of the following are key functions carried out by membrane proteins? Catalyze specific chemical reactions on the surface of the membrane Transport specific ions and molecules across the membrane Short-term storage of excess energy Function as cell-surface identity markers Receive external chemical messages - answer โ
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Transport specific ions and molecules across the membrane
Code for the production of new polynucleotides - answer โ
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Attach the membrane to the cytoskeleton Connect adjacent cells and hold them together Receive external chemical messages Which of the following are true of the plasma membrane? It is fully permeable. It is selectively permeable. It is fluid. It is composed mainly of carbohydrates and proteins. - answer โ
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It is selectively permeable.
It is fluid. Which of the following best describes the relationship between solute concentration and rate of diffusion during facilitated diffusion by carrier proteins? As solute concentration decreases, the rate of diffusion increases. As solute concentration increases, the rate of diffusion increases. As solute concentration decreases, the rate of diffusion increases but eventually it remains constant once it reaches a maximum rate. As solute concentration increases, the rate of diffusion increases but eventually it remains constant once it reaches a maximum rate. - answer โ
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As solute
