bio chp 7

If a red blood cell is placed in a salt solution and bursts, what is the tonicity of the solution relative to the interior of the cell?

Hypotonic

Which statements about the fluid mosaic structure of a membrane are correct? Select the three correct statements. -Membranes include a mosaic, or mix, of carbohydrates embedded in a phospholipid bilayer. -The diverse proteins found in and attached to membranes perform many important functions. -Because membranes are fluid, membrane proteins and phospholipids can drift about in the membrane. -The framework of a membrane is a bilayer of phospholipids with their hydrophilic heads facing the aqueous environment inside and outside of the cell and their hydrophobic tails clustered in the center. -The kinky tails of some proteins help keep the membrane fluid by preventing the component molecules from packing solidly together.

2,3,4

What property of dishwashing liquid (detergent) makes it useful to wash grease from pans?

Amphipathic nature

Which of the following correctly describes some aspect of exocytosis or endocytosis? Hints Both processes provide a mechanism for exchanging membrane-impermeable molecules between the organelles and the cytosol. The inner surface of a transport vesicle that fuses with or buds from the plasma membrane is most closely related to the inner surface of the plasma membrane. Exocytosis and endocytosis temporarily change the surface area of the plasma membrane. Endocytosis and exocytosis involve passive transport. These two processes require the participation of mitochondria.

Exocytosis and endocytosis temporarily change the surface area of the plasma membrane.

How can a lipid be distinguished from a sugar?

Lipids are mostly nonpolar.

Select the correct statement about osmosis. Osmosis is the diffusion of water molecules across a selectively permeable membrane. Osmotic equilibrium cannot be reached unless solute concentrations equalize across the membrane. If a dead cell is placed in a solution hypotonic to the cell contents, osmosis will not occur.

Osmosis is the diffusion of water molecules across a selectively permeable membrane.

Which of the following particles could diffuse easily through a cell membrane? Hints Oxygen (O2) Sodium ion (Na+) Glucose Hydrogen ion (H+)

Oxygen (O2)

Which statement is correct? A solution of seawater is hypertonic. The contents of a red blood cell are hyperosmotic to distilled water. A solution of distilled water is hypotonic

The contents of a red blood cell are hyperosmotic to distilled water.

Which of the following factors does not affect membrane permeability? The polarity of membrane phospholipids The saturation of hydrocarbon tails in membrane phospholipids Temperature The amount of cholesterol in the membrane

The polarity of membrane phospholipids

Which of the following statements about osmosis is correct? Hints Osmosis is the diffusion of water from a region of lower water concentration to a region of higher water concentration. Osmotic movement of water into a cell would likely occur if the cell accumulates water from its environment. If a solution outside the cell is hypertonic compared to the cytoplasm, water will move into the cell by osmosis. If a cell is placed in an isotonic solution, more water will enter the cell than leaves the cell. The presence of aquaporins (proteins that form water channels in the membrane) should speed up the process of osmosis.

The presence of aquaporins (proteins that form water channels in the membrane) should speed up the process of osmosis.

Cell membranes are asymmetrical. Which of the following statements is the most likely explanation for the membrane's asymmetrical nature?

The two sides of a cell membrane face different environments and carry out different functions.

Which of the following statements about a typical plasma membrane is correct? Hints The two sides of the plasma membrane have different lipid and protein composition. Carbohydrates on the membrane surface are important in determining the overall bilayer structure. Phospholipids are the primary component that determines which solutes can cross the plasma membrane. The hydrophilic interior of the membrane is composed primarily of the fatty acid tails of the phospholipids. The plasma membrane is a covalently linked network of phospholipids and proteins that controls the movement of solutes into and out of a cell.

The two sides of the plasma membrane have different lipid and protein composition.

In facilitated diffusion, what is the role of the transport protein?

Transport proteins provide a hydrophilic route for the solute to cross the membrane.

True or false? Osmosis is a type of diffusion.

True

True or false? The water-soluble portion of a phospholipid is the polar head, which generally consists of a glycerol molecule linked to a phosphate group.

True

What happens when two solutions separated by a selectively permeable membrane reach osmotic equilibrium?

Water molecules move between the two solutions, but there is no net movement of water across the membrane.

Which of the following molecular movements is due to diffusion or osmosis? Cells of the pancreas secrete insulin into the bloodstream. When a plant cell is placed in concentrated salt water, water moves out of the cell. The sodium-potassium pump pumps three sodium ions out of a neuron for every two potassium ions it pumps in.

When a plant cell is placed in concentrated salt water, water moves out of the cell.

Which of the following factors would tend to increase membrane fluidity? a greater proportion of saturated phospholipids a relatively high protein content in the membrane a lower temperature a greater proportion of unsaturated phospholipids a greater proportion of relatively large glycolipids compared with lipids having smaller molecular masses

a greater proportion of unsaturated phospholipids

If the concentration of phosphate in the cytosol is higher than the concentration of phosphate in the surrounding fluid, how could the cell increase the concentration of phosphate in the cytosol?

active transport

Endocytosis moves materials _____ a cell via _____.

into ... membranous vesicles

When molecules move down their concentration gradient, they move from where they are _____________ to where they are______________ Diffusion across a biological membrane is called ______________

more concentrated less concentrated. passive transport.

What name is given to the process by which water crosses a selectively permeable membrane?

osmosis

Which of the following processes includes all others? osmosis transport of an ion down its electrochemical gradient diffusion of a solute across a membrane facilitated diffusion passive transport

passive transport

A white blood cell engulfing a bacterium is an example of _____.

phagocytosis

You can recognize the process of pinocytosis when _____.

the cell is engulfing extracellular fluid

Which of the following would be a factor that determines whether the molecule selectively enters the target cells? the nonpolar, hydrophobic nature of the drug molecule the concentration of the drug molecule that is transported in the blood the similarity of the drug molecule to other molecules that are transported into the target cells the phospholipid composition of the target cells' plasma membrane

the similarity of the drug molecule to other molecules that are transported into the target cells

The permeability of a biological membrane to a specific polar solute may depend on which of the following?

the types of transport proteins in the membrane

Part A Which of the following best describes the structure of a biological membrane? Hints a fluid structure in which phospholipids and proteins move freely between sides of the membrane two layers of phospholipids with proteins either crossing the layers or on the surface of the layers two layers of phospholipids (with opposite orientations of the phospholipids in each layer) with each layer covered on the outside with proteins two layers of phospholipids with proteins embedded between the two layers a mixture of covalently linked phospholipids and proteins that determines which solutes can cross the membrane and which cannot

two layers of phospholipids with proteins either crossing the layers or on the surface of the layers