Connect Assignment Week 7

What type of microscope can be used to see the two phospholipid layers in a plasma membrane? Dark-field Phase contrast Fluorescent Electron

Electron

Which of the following is not one of the four main components of all plasma membranes? Interior protein network Lipid bilayer Extracellular matrix Transmembrane proteins Cell surface markers

Extracellular matrix

When a channel protein or carrier protein assists in diffusion, which of the following is observed? Simple diffusion Endocytosis Active transport Facilitated diffusion Dialysis

Facilitated diffusion

Which method of microscopy is illustrated in this drawing? Confocal microscopy Transmission electron microscopy Freeze-fracture microscopy Scanning electron microscopy

Freeze-fracture microscopy

Choose the three groups of lipids found in eukaryotic cells. Integral bilayer lipids Triglycerides Sphingolipids Sterols Glycerol phospholipids

Glycerol phospholipids Sphingolipids Sterols

The ER membrane is typically more fluid than the plasma membrane and it contains more curvature. Why? The ER membrane contains mainly sphingolipids. The ER membrane contains mainly unsaturated phospholipids. The ER membrane contains high concentrations of cholesterol.

The ER membrane contains mainly unsaturated phospholipids.

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.

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.

Select the accurate statements concerning membrane fluidity. The degree of membrane fluidity varies depending on the composition of the membrane. Phospholipids are relatively free to move around laterally within the membrane. All membranes have essentially the same composition and degree of fluidity. Unanchored proteins are relatively free to move around laterally within the membrane.

The degree of membrane fluidity varies depending on the composition of the membrane. Phospholipids are relatively free to move around laterally within the membrane. Unanchored proteins are relatively free to move around laterally within the membrane.

Select the statements that are true about ions. They interact well with polar molecules. 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.

They interact well with polar molecules. They are repelled by the hydrophobic interior of the lipid bilayer.

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

Transport specific ions and molecules across the membrane Catalyze specific chemical reactions on the surface of the membrane Function as cell-surface identity markers Receive external chemical messages

Due to the constant random motion of its atoms and molecules, a substance will exhibit net movement from a region where it has a higher concentration to a region where it has a lower concentration. This net movement is called _________

diffusion

The lipid bilayer that forms the core of all cell membranes is composed primarily of

phospholipids

The cytoplasm contains ions and molecules dissolved in .

water

When phospholipids are placed in water, they spontaneously form which of the following? A bilayer A double helix Unbranched chains Branched chains 5-sided rings

A bilayer

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.

As solute concentration increases, the rate of diffusion increases but eventually it remains constant once it reaches a maximum rate.

Which of the following are key functions carried out by membrane proteins? Transport oxygen into the cell Attach the membrane to the cytoskeleton Connect adjacent cells and hold them together Receive external chemical messages Code for the production of new polynucleotides

Attach the membrane to the cytoskeleton Connect adjacent cells and hold them together Receive external chemical messages

Which of the following describes passive transport? It does not require a concentration gradient. It can only be used to move materials up a concentration gradient. It does not require an expenditure of energy by the cell itself. It requires energy from ATP.

It does not require an expenditure of energy by the cell itself.

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.

It is selectively permeable. It is fluid.

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

Lipid bilayer Interior protein network Lipid bilayer Interior protein network

How do carrier proteins differ from channel proteins? 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.

Only carrier proteins actually bind to the substance being transported.

Compared to the ER membrane, the plasma membrane contains more of which of the following (choose all that apply)? Sphingomyelin Unsaturated phospholipids Cholesterol Phosphatidylcholine

Phosphatidylcholine Sphingomyelin Cholesterol

Which of the following makes up the bilayer of every cell membrane? Proteins Cholesterol Unsaturated fats Phospholipids Saturated fats

Phospholipids

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.

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.

Plasma membranes allow some substances to pass through easily while other substances only pass through very slowly or not at all. For that reason, plasma membranes are considered which of the following? Selectively permeable Fluid Partially permeable Hydrophobic Amphipathic

Selectively permeable

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 The polar heads on the surface and the nonpolar tails in the interior The polar heads in one layer and the nonpolar tails in the other layer The polar heads in the interior and the nonpolar tails on the surface

The nonpolar heads on the surface and the polar tails in the interior

Of the 2 types of transport proteins that mediate facilitated diffusion, only proteins actually bind with the substance being transported while proteins simply provide a hydrophilic space for the substance to move through.

carrier channel

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 _________ proteins. These transporter proteins are typically transmembrane proteins.

channel carrier

Ion _____________ have a hydrated interior that spans the membrane and allows ions to diffuse through.

channels

The lack of double bonds in saturated fats allow them to pack together tightly, and therefore the membrane is fluid. The presence of double bonds in unsaturated fats prevent them from packing together tightly, and therefore the membrane is fluid.

less more

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.

membrane permeable

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!

sphingolipids sterols