Structure and Function of Plasma Membranes
How many potassiums does the Na+/K+ ATPase pump into the cell?
2
How many ions or molecules can an antiporter carry? In what direction do these molecules travel?
2 different ions or molecules in different direction
How many ions or molecules can a symporter carry? In what direction do these molecules travel?
2 different ions or molecules, both in the same direction
How many sodiums does the Na+/K+ Atpase pump out of the cell?
3
Define pinocytosis.
A process that takes in molecule, including water, that the cell needs from the extracellular fluid
Which of the following are electrogenic? Na/K ATPase Ligand-gated NA+ channel Pinocytosis
Na/K ATPase Ligand-gated Na+ channel
The interior of living cell mostly have what charge?
Negative
How much energy does diffusion require?
None.
How many ions or molecules doe s a uniporter carry?
One
Which molecules have no charge and pass through membranes by simple diffusion?
Oxygen and Carbon dioxide
Which transport mechanism can bring whole cells into a cell?
Phagocytosis
Ligand-gated Na+ influx in response to a chemical neurotransmitter depends on: A. Na/K ATPase activity B. Aquaporins C. The fluidity of the phospholipid bilayer D. Cholesterol levels within the phospholipid bilayer Gap junctions
A. Na/K ATPase activity
What problem is faced by organisms that live in fresh water? A. their bodies tend to take in too much water B. They have no way of controlling their tonicity C. Only salt water poses problems for animals that live in it D. Their bodies tend to lose too much water to their environment
A. their bodies tend to take in too much water
Active transport mechanisms uses _____.
ATP
Plasma membrane are _____________ meaning they have both hydrophilic and hydrophobic parts.
Amphiphilic
What is created as sodium ion concentrations build outside of the plasma membrane because of the primary active transport process?
An electrochemical gradient
Which channel proteins allow water to pass through the membrane at a very high rate?
Aquaporins
Concentration gradients are a form of __________ energy.
Potential
The sodium potassium pump is an example of what type of transport?
Primary active transport
Define phagocytosis.
Process by which large particles are engulfed by vesicles and absorbed into the another cell.
Which plasma membrane component can be either found on its surface or embedded in the membrane structure?
Protein
What active transport mechanisms work against electrochemical gradients?
Pumps
Receptor mediated endocytosis is characterized by: A. simple diffusion of nutrients into a cell B. the cued bulk transport of extracellular compounds into a cell C. the bulk release of cellular waste products upon the activation of extracellular signaling compounds D. the facilitated diffusion of specific classes of signaling compounds into the cell
B. The cued bulk transport of extracellular compounds into a cell
How does the sodium-potassium pump make the interior of the cell negatively charged?
By expelling more cations than are taken in
What can get through the plasma membrane by simple diffusion?
Small uncharged molecules (Small nonpolar, hydrophobic) Gases
How does a carrier protein allow molecules to move into or out of the cell?
The carrier protein binds to the substance triggering a change of the protein's shape and then moves the bound molecule in the appropriate direction.
What is an isotonic solution?
The concentrations of water are equal on both side of the membrane. There will be no net movement of water into or out of the cell.
What is membrane potential?
The difference in charges on both sides of the membrane.
What produces the turgor pressure that stiffens cell walls in plants?
The hypotonic solution of the cytoplasm
How does the sodium potassium pump make the interior of the cell negatively charged? A. by expelling anions B By pulling in anions C. By expelling more cations that are taken in D. By taking in and expelling an equal number of cations
C. By expelling more cations than are taken in
What happens to the membrane of a vesicle after exocytosis? A. It leaves the cell B. It is disassembled by the cell C. It fuses with and becomes part of the plasma membrane D. It is used again in another exocytosis event.
C. It fuses with and becomes part of the plasma membrane.
The principal force driving movement in diffusion is the __________. A. Temperature B. Particle size C. Concentration gradient D. Membrane surface area
C. concentration gradient
In what important way does receptor-mediated endocytosis differ from phagocytosis? A. It transports only small amounts of fluid. B. It does not involve the pinching off of membrane. C. It brings in a specifically targeted substance. D. It brings substances into the cell, while phagocytosis remove substances.
C. it brings in a specifically targeted substance
What protein coats the inner portion of the plasma membrane in preparation for phagocytosis?
Clathrin
The principal force driving movement in diffusion is the __________ __________.
Concentration gradient
Active transport must function continuously because A. Plasma membranes wear out B. Not all membrane are amphiphilic C. Facilitated transport opposes active transport D. Diffusion is constantly moving solutes in opposite directions
D. Diffusion is constantly moving solutes in opposite directions
Define osmolarity.
Describe the total solute concentration of the solution
Active transport must function continuously because?
Diffusion is constantly moving solutes in opposite directions
Which characteristic of phospholipid contributes to the fluidity of the membrane?
Double bonds in the fatty acid tail
The lack of a concentration gradient in which there is no net movement of a substance is known as ____________ ____________.
Dynamic equilibrium
What is the combination of an electrical gradient and a concentration gradient called? A. Potential gradient B. Electrical potential C. Concentration potential D. Electrochemical gradient
Electrochemical gradient
What is the combination of an electrical gradient and a concentration gradient?
Electrochemical gradient
Define receptor mediated endocytosis.
Employes receptor proteins in the plasma membrane that have specific binding affinity for certain substances.
Which type of bulk transport moves large molecules, parts of cells or even whole cells into a cell?
Endocytosis
Name the three types of bulk transport.
Endocytosis Exocytosis Receptor-mediated endocytosis
If a substance must move against its concentration gradient, the cell must use __________ to move the substance.
Energy
What is the primary function of carbohydrates attached to the exterior of cell?
Identification of the cell
Define osmosis.
The movement of water through a semipermeable according to the concentration gradient of water across the membrane, which is inversely proportionally to the concentration of solutes.
What is the fluid mosaic model?
The phospholipid bilayer is fluid meaning it can move laterally and is a mosaic because it is made up of many different parts (proteins etc.)
How do facilitated transport proteins get ions into the hydrophobic parts of the cell membrane?
The proteins shield the materials from the repulsive force of the membrane, allowing them to diffuse into the cell.
What problem is faced by organism that live in fresh water?
Their bodies tend to take in too much water.
What is a hypertonic solution?
There is a higher concentration of water inside the cell than outside the cell. Water will leave the cell in this case.
What is a hypotonic solution?
There is a lower concentration of water inside the cell than outside the cell. Water will move into the cell in this case.
In what important way does receptor-mediated endocytosis differ from phagocytosis?
It bring in only a specifically targeted substance.
What is the function of secondary active transport?
It describes the movement of material that is due to the electrochemical gradient established by primary active transport that does not directly require ATP>
What is the function of primary active transport?
It moves ions across a membrane and creates a difference in charge across the membrane.
What does the vesicle formed by phagocytosis merge with once inside the cell to facilitate in the digestion of it?
Lysosome
How do substances diffuse?
They move from an area of high concentration to an area of low concentration until the concentration is equal.
What if the function of exocytosis?
To expel material from the cell into extracellular fluid
Define tonicity.
Tonicity is how an extracellular solution can change the volume of a cell by affecting osmosis
What are the three carrier proteins for active transport called?
Uniporters Symporters Antiporters
Are carrier proteins specified for a single substance?
Yes
Are protein channels specified for the substance they transport?
Yes.
Integral proteins can function as both ________ or ________.
channels, carriers
The combined gradient of concentration and electrical charge that affects an ion is called the ______________ __________.
electrochemical gradient
Water moves via osmosis
from an area with a high concentration of water to one of lower concentration
Osmotic pressure works against __________.
gravity
A solution with low osmolarity has a _________ number of water molecules relative to the number of solute particles.
greater
The cytoplasm in plants is always slightly ________. Why?
hypotonic Water will readily move into the cell in this case.
Channel proteins are either _______ at all times or they are ________.
open gated
Facilitated diffusion utilizes _________.
proteins
Membranes are ___________ permeable.
selectively
