Membranes and Diffusion

Question 1

Bilayer

Answer 1

thin polar membrane made of two layers of lipid molecules. These membranes are flat sheets that form a continuous barrier around all cells.

Question 2

Solution

Answer 2

composed of a solvent and a solute

Question 3

Solvent

Answer 3

The substance in which a solute is dissolved

Question 4

Solute

Answer 4

The substance which is dissolved in the solvent

Question 5

Concentration

Answer 5

The ratio of the mass or volume of a substance (solute) to the mass or volume of the solvent or solution (M aka mol/L)

Question 6

Lipids

Answer 6

Energy storage, structural component of cell membrane, and cell signaling

Question 7

Oils

Answer 7

triglyceride that is liquid at room temperature that does not mix with water

Question 8

Fats

Answer 8

Known as triglycerides, molecules made from the combination of one molecule of glycerol with three fatty acids

Question 9

Fatty acid

Answer 9

Largely of a chain of carbon atoms bonded with hydrogen atoms. At one of the terminal ends of a fatty acid is a carboxyl group (-COOH), which is the reactive portion of the molecule and will participate in chemical reactions to make lipids and to store energy.

Question 10

Saturated

Answer 10

(of a solution or solvent) containing the maximum amount of solute that can normally be dissolved at a given temperature and pressure.

Question 11

Unsaturated

Answer 11

capable of absorbing or dissolving to a greater degree; as, an unsaturated solution

Question 12

Waxes

Answer 12

the mixture of long-chain apolar lipids forming a protective coating (wax of honeybees for example)

Question 13

Phospholipids

Answer 13

Glycerol molecule, two fatty acids, and a phosphate group that is modified by an alcohol. The phosphate group is the negatively-charged polar head, which is hydrophilic. The fatty acid chains are the uncharged, nonpolar tails, which are hydrophobic.

Question 14

Glycerol

Answer 14

A sweet, syrupy liquid obtained from animal fats and oils or by the fermentation of glucose. It is used as a solvent, sweetener, and antifreeze and in making explosives and soaps.

Question 15

plasma membrane

Answer 15

a microscopic membrane of lipids and proteins that forms the external boundary of the cytoplasm of a cell or encloses a vacuole, and that regulates the passage of molecules in and out of the cytoplasm.

Question 16

cell membrane

Answer 16

made of phospholipids.

Question 17

cholesterol

Answer 17

waxy type of lipid, a substance that is insoluble in water, like oil or fat. Specifically, cholesterol is a type of fat that is made up of four interlocked rings of carbon called a steroid.

Question 18

Transport Proteins

Answer 18

A channel protein serves as a tunnel across the membrane into the cell. More specifically, channel proteins help molecules across the membrane via passive transport, a process called facilitated diffusion. These channel proteins are responsible for bringing in ions and other small molecules into the cell.

Question 19

Recognition Proteins

Answer 19

one of a class of glycoproteins or glycolipids that project above the plasma membrane and that identifies a cell as nonself (foreign) or self (belonging to one’s own body tissue)

Question 20

Receptor Proteins

Answer 20

binds extracellular substances, such as hormones that can trigger change in cell activities

Question 21

Cell Adhesion Proteins

Answer 21

of multi-celled species, a plasma membrane protein that helps cells stick together in tissues and to extracellular matrixes such as basement membrane

Question 22

Glycolipids

Answer 22

lipids with a carbohydrate attached by a glycosidic bond.Their role is to serve as markers for cellular recognition and also to provide energy.

Question 23

Glycoproteins

Answer 23

simply proteins with a sugar attached to them. The sugars can be attached to a protein in two locations in the cell, the endoplasmic reticulum, wand the Golgi apparatus

Question 24

Concentration Gradient

Answer 24

difference in the number of molecules or ions of any one substance between two adjoining regions

Question 25

Selectively permeable

Answer 25

built-in capacity of a cell membrane to prevent or allow specific substances from crossing it at certain times, in certain amounts

Question 26

Simple Diffusion

Answer 26

a process whereby a substance passes through a membrane without the aid of an intermediary such as a integral membrane protein.

Question 27

Tonicity

Answer 27

a measure of the effective osmotic pressure gradient, as defined by the water potential of two solutions separated by a semipermeable membrane. In other words, tonicity is the relative concentration of solutes dissolved in solution which determine the direction and extent of diffusion.

Question 28

Hypotonic

Answer 28

Of two liquids, the one with the lower solute concentration

Question 29

Hypertonic

Answer 29

Of two fluids, the one with the higher solute concentration

Question 30

Isotonic

Answer 30

any fluid having the same solute concentration as another fluid to which it is being compared

Question 31

Amphipathic

Answer 31

Pertains to a molecule containing both polar (water-soluble) and nonpolar (not water-soluble) portions in its structure. (2) Of, or relating to, a molecule having hydrophobic and hydrophilic regions.

Question 32

The different properties/domains of a phospholipid that make it amphipathic

Answer 32

phospholipid is amphipathic, having both polar and nonpolar regions, and it forms lipid bilayers spontaneously in water. (b) These lipid bilayers are stabilized by the energy gained from burying hydrophobic groups out of contact with water. A hydrophobic chain in water forces the formation of a cage of immobilized water molecules around it. When several hydrophobic regions cluster in a bilayer, the surface area exposed to water decreases, and the water molecules in the cage are released, accompanied by a gain in entropy that drives the formation of the bilayer.

Question 33

The structure of cell membranes/plasma membranes and how this structure is related to their most important function(s)

Answer 33

A cell membrane is a thin structure that is also known as the plasma membrane.The main functions of the cell membrane are:

to maintain the physical integrity of the cell - that is to mechanically enclose the contents of the cell, and also
to control the movement of particles e.g. ions or molecules, into and out of the cell.

Phospholipids
-Main fabric of the membrane
Cholesterol
- Tucked between the hydrophobic tails of the membrane phospholipids
Integral proteins
- Embedded in the phospholipid bilayer; may or may not extend through both layers
Peripheral protein
-On the inner or outer surface of the phospholipid bilayer, but not embedded in its hydrophobic core
Carbohydrates
-Attached to proteins or lipids on the extracellular side of the membrane (forming glycoproteins and glycolipids)

Question 34

Explain the effects of diffusion on a molecule that is at different concentrations on either side of a permeable membrane

Answer 34

Different concentrations of solute molecules leads to different concentrations of free water molecules on either side of the membrane. On the side of the membrane with higher free water concentration (i.e. a lower concentration of solute), more water molecules will strike the pores in the membrane in a give interval of time. More strikes equates to more molecules passing through the pores, which in turn results in net diffusion of water from the compartment with high concentration of free water to that with low concentration of free.This means that water flows in response to differences in molarity across a membrane.

Question 35

Explain the effects of diffusion on a molecule that is at equal concentration on either side of a
permeable membrane

Answer 35

the size of the solute particles does not influence osmosis. Equilibrium is reached once sufficient water has moved to equalize the solute concentration on both sides of the membrane, and at that point, net flow of water ceases.

Question 36

How water will move across a membrane under isotonic, hypertonic, and hypotonic
conditions

Answer 36

Isotonic: The solutions being compared have equal concentration of solutes.

Hypertonic: The solution with the higher concentration of solutes.

Hypotonic: The solution with the lower concentration of solutes.

Question 37

Take a look at the big cartoon diagram of CFTR in a membrane that is in the slides for a few of
the past lectures. What parts of the protein would you predict are hydrophobic and what parts are
hydrophilic? You should base your analysis on what is in contact with certain parts of the protein.
Is the protein touching part of the cell membrane? is it touching the outside world? What about
the functional aspects of the protein? I can think of at least 6 different regions of the protein that
you can assign a hydrophobic/hydrophilic nature to.

Answer 37

? (insert pic)

Question 38

Electric gradient

Answer 38

a difference in electric charge between adjoining regions