U2 Chapter 7: Membrane Structure and Function

Question 1

Fluid Mosaic Model

Answer 1

Describes the structure of the plasma membrane as a mosaic of components —including phospholipids, cholesterol, proteins, and carbohydrates—that gives the membrane a fluid character. Plasma membranes range from 5 to 10 nm in thickness

Question 2

Amphipathic

Answer 2

Any compound that contains two distinct covalently bonded components with different affinity for the solvent in the same molecule, in which one part possesses a high affinity for polar solvents (such as water), and another part has a strong affinity for nonpolar

Question 3

Glycoproteins

Answer 3

Molecules that comprise protein and carbohydrate chains that are involved in many physiological functions including immunity

Question 4

Glycolipid

Answer 4

Lipids with a carbohydrate attached by a glycosidic (covalent) bond. Their role is to maintain the stability of the cell membrane and to facilitate cellular recognition, which is crucial to the immune response and in the connections that allow cells to connect to one another to form tissues

Question 5

Selective Permeability

Answer 5

The cell membrane refers to its ability to differentiate between different types of molecules, only allowing some molecules through while blocking others. Some of this selective property stems from the intrinsic diffusion rates for different molecules across a membrane

Question 6

Transport Protein

Answer 6

Integral transmembrane proteins; that is they exist permanently within and span the membrane across which they transport substances. The proteins may assist in the movement of substances by facilitated diffusion or active transport

Question 7

Diffusion

Answer 7

The process of movement of molecules under a concentration gradient. It is an important process occurring in all living beings. Diffusion helps in the movement of substances in and out of the cells

Question 8

Concentration Gradient

Answer 8

An important process for understanding how particles and ions move in random motion in a solution or gas. It is the process used for particles moving from an area of higher concentration in a solution to an area of lower concentration

Question 9

Osmosis

Answer 9

Movement of water molecules from a solution with a high concentration of water molecules to a solution with a lower concentration of water molecules, through a cell’s partially permeable membrane

Question 10

Hypertonic

Answer 10

A solution that contains more dissolved particles (such as salt and other electrolytes) than is found in normal cells and blood

Question 11

Hypotonic

Answer 11

A solution outside of a cell is called hypotonic if it has a lower concentration of solutes relative to the cytosol. Due to osmotic pressure, water diffuses into the cell, and the cell often appears turgid, or bloated

Question 12

Isotonic

Answer 12

Contain equal concentrations of impermeable solutes on either side of the membrane and so the cell neither swells nor shrinks

Question 13

Facilitated Diffusion

Answer 13

Molecules diffuse across the plasma membrane with assistance from membrane proteins, such as channels and carriers. A concentration gradient exists for these molecules, so they have the potential to diffuse into (or out of) the cell by moving down it

Question 14

Ion Channels

Answer 14

Protein molecules that span across the cell membrane allowing the passage of ions from one side of the membrane to the other. They have an aqueous pore, which becomes accessible to ions after a conformational change in the protein structure that causes the ion channel to open

Question 15

Active Transport

Answer 15

Molecules moving against a gradient or other form of resistance, such as from an area of lower to higher charge. Active transport is used by cells to accumulate needed molecules such as glucose and amino acids

Question 16

Electrochemical Gradient

Answer 16

A measure of the free energy available to carry out the useful work of transporting the molecule across the membrane. It has two components: One component represents the energy in the concentration gradient for X across the membrane(chemical potential difference)

Question 17

Cotransport

Answer 17

A carrier protein that allows the transport of two different species (a solute and an ion) from one side of the membrane to the other at the same time

Question 18

Exocytosis

Answer 18

Transportation of glucagon from the pancreas into the liver where it is further processed for easier absorption into the blood stream
- Transportation of protein-filled vesicles from T cells to viral infected cells

Question 19

Endocytosis

Answer 19

A process by which cells absorb external material by engulfing it with the cell membrane
- Endocytosis is usually subdivided into pinocytosis and phagocytosis

Question 20

Phagocytosis

Answer 20

A cellular process for ingesting and eliminating particles larger than 0.5 μm in diameter, including microorganisms, foreign substances, and apoptotic cells

Question 21

Pinocytosis

Answer 21

A process by which the cell takes in the fluids along with dissolved small molecules. In this process, the cell membrane folds and creates small pockets and captures the cellular fluid and dissolved substances

Question 22

Receptor-Mediated Endocytosis

Answer 22

Also called clathrinid-mediated endocytosis, is a process by which cells absorb metabolites, hormones, proteins – and in some cases viruses – by the inward budding of the plasma membrane (invagination)