Mastering Biology Chapter 7 HW

In this diagram of the plasma membranes of two adjoining cells, identify the protein indicated by the white arrow, including its function.

* a receptor protein that binds with a signaling molecule and relays the message into the cell by activating other molecules inside the cell *

Which of the following statements correctly describe(s) the driving forces for diffusion of Na+ and K+ ions through their respective channels? Select all that apply.

1) The diffusion of K+ ions out of the cell is impeded by the electrical gradient across the plasma membrane. 2)The electrochemical gradient is larger for Na+ than for K+. 3) The diffusion of Na+ ions into the cell is facilitated by the Na+ concentration gradient across the plasma membrane.

Which statements about the fluid mosaic structure of a membrane are correct? Select the three correct statements.

1) The diverse proteins found in and attached to membranes perform many important functions. 2)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. 3)Because membranes are fluid, membrane proteins and phospholipids can drift about in the membrane.

Which of the following statements about the conditions shown in the U-shaped tube are true?

1) Water is tightly clustered around the hydrophilic solute molecules on both sides of the membrane. 2) There is less free water in the right arm of the tube than in the left arm of the tube.

Part A - Active transport by the sodium-potassium pumpPART completeAll cells contain ion pumps that use the energy of ATP hydrolysis to pump ions across the plasma membrane. These pumps create an electrochemical gradient across the plasma membrane that is used to power other processes at the plasma membrane, including some transport processes. In animal cells, the main ion pump is the sodium-potassium pump.

A- 3 Na+ increase 2 K+ decrease B- Na high K low C-Excess + charge D- Na low K high E- Excess - charge

Sort the phrases into the appropriate bins depending on whether they are true only for channels, true only for carrier proteins, or true for both channels and carriers.

Only channels- provides a continues path across the membrane, allow water molecules and small ions o flow quickly across the membrane only carriers- undergo change in shape to transport solute across the membrane, transports primarily small organic molecules Both- provides hydrophilic path across membrane, are integral membrane proteins, transports solutes down concentration or electrochemical gradient

Part A - Diffusion All molecules have energy that causes thermal motion. One result of thermal motion is diffusion: the tendency of substances to spread out evenly in the available space. Although the motion of each individual molecule is random, there can be directional motion of an entire population of molecules.

Orange dye moves more independently of purple dye- always Concentration gradients exist that drive off diffusion on both dyes- only before equilibrium is reached There is a movement of orange dye from side A to side B- only before equilibrium is reached Purple dye moves ONLY from B to A- never There is no net movement of purple dye- only at equilibrium

Part D Part completeIf the pores in the selectively permeable membrane became larger, but still not large enough to let the sugar pass through, what would happen during osmosis in the U-shaped tube compared to what is shown in the figure?

The final water levels would be the same as shown in the figure, but the solutions would reach near equal concentrations faster.

Part C: You are working on a team that is designing a new drug. For this drug to work, it must enter the cytoplasm of specific target cells. Which of the following would be a factor that determines whether the molecule selectively enters the target cells?

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

If more sugar were added to the solution on the left side of the tube, what would happen to the water level on the right side of the tube?

The water level would go down.

Part B Which of the following molecules can cross the lipid bilayer of a membrane directly, without a transport protein or other mechanism? Select all that apply.

Water, Carbon Dioxide, Lipids, Oxygen

Part A - The glucose-sodium cotransporterPart completeIn many animal cells, the uptake of glucose into the cell occurs by a cotransport mechanism, in which glucose is cotransported with Na+ ions.

a- glucose low b- glucose and Na down c- glucose high d- Na moves down and glucose moves against

Part A - Exocytosis and endocytosisPart completeSort the phrases into the appropriate bins depending on whether they describe exocytosis, endocytosis, or both.

exocytosis- requires fusion of vesicles with the plasma membrane, increse the surface area of the plasma membrane, secretes large molecules out of cells endocytosis- decrease the surface area of the plasma membrane, forms vesicles from inward folding of the plasma membrane both- requires cellular energy, transported substances never physically cross the plasma membrane

During osmosis, water diffuses across a selectively permeable membrane from the region of higher ______ concentration and lower _____ concentration to the side with lower ______ concentration and higher ______ concentration.

free water, solute, free water, solute