What are glycoproteins and glycolipids important for
cell-cell recognition
A single layer of phospholipid molecules coats the water in a beaker. Which part of the molecules will face the air?
hydrocarbon tails
Is osmosis a passive process in cells without walls, but an active one in cells with walls
no
Support for the fluid mosaic model of membrane structure comes from
The freeze fracture technique of electron microscopy
and the movement of proteins in hybrid cells
and the amphipathic nature of many membrane proteins
Facilitated diffusion of ions across a cellular membrane requires _____ and the ions move _______.
Transport proteins ... down their electrochemical gradient
Which of the following is the most probable description of an integral, transmembrane protein?
A middle region composed of alpha helical stretches of hydrophobic amino acids, with hydrophilic regions at both ends of the protein.
The fluidity of membranes in a plant in cold weather may be maintained by increasing the
Number of phospholipids with unsaturated hydrocarbon tails
An animal cell placed in a hypotonic environment will
Burst (lyse)
Which of the following is not true of carrier molecules involved in facilitated diffusion?
They can concentrate solute molecules on one side of the membrane
The membrane potential of a cell favors
The movement of cations into the cell.
Cotransport may involve
Transport of one solute against its concentration gradient in tandem with another that is diffusing down its concentration gradient.
Exocytosis may involve all of the following except
Ligands and coated pits
The proton pump in plant cells is the functional equivalent of an animal cell's
Sodium-potassium pump
Pinocytosis involves
The pinching in of the plasma membrane around small droplets of external fluid.
Watering a houseplant with too concentrated a solution of fertilizer can result in wilting because
The soil solution becomes hypertonic, causing the cells to lose water.
A cell is manufacturing receptor proteins for cholesterol. How would those proteins be oriented in the following membranes before they reach the plasma membrane?
Facing inside the ER lumen and inside the transport vesicle.
You observe plant cells under a microscope as they are placed in an unknown solution. First the cells plasmolyze, after a minute, the plasmolysis reverses and the cells appear normal. What would you conclude about the unknown solution?
It is hypertonic to the plant cells, but its solute can cross the plant membranes.