Shared Flashcard Set

Details

Ch7 Membrane Structure and Function
BIO181 BIO 181 Obermiller
76
Biology
Undergraduate 2
06/14/2012

Additional Biology Flashcards

 


 

Cards

Term
What is measured by the differences in positive and negative charges on each side of the membrane?
Definition
Membrane Potential
Term
What is the transport of molecules from one area to another without energy called?
Definition
Passive
Term
What is it called when a cell membrane only allows certain molecules to pass from one side to the other?
Definition
Selective Permeability
Term
What is the passive transport (diffusion) of molecules across the plasma membrane with the help of transport proteins called?
Definition
Facilitated
Term
Some plants increase this type of fatty acids in their phospholipids to make their membranes more fluid in colder conditions.
Definition
Unsaturated
Term
Integral membrane proteins that transport specific ions or molecules across the plasma membrane.
Definition
Transport
Term

Technique scientists use to support the fluid mosaic model.

 

Involves freezing a cell and then breaking it apart at the membrane.

Definition
Freeze Fracture
Term

Solution that has a higher solute concentration than that found inside the cell.

 

Resulting in water flow out of the cell.

Definition
Hypertonic
Term
Gradient of electrical energy established by a membrane's potential.
Definition
Electrochemical
Term
The fluidity of the plasma membrane is dependent on this environmental factor.
Definition
Temperature
Term
Importing of macromolecules from the cell via fusion with the plasma membrane forming vesicles.
Definition
Endocytosis
Term
The random movement of molecules spreading out in available space.
Definition
Diffusion
Term
Molecules that are both hydrophobic and hydrophilic at the same time on different parts.
Definition
Amphipathic
Term
Tran-membrane proteins that have hydrophobic regions that embed in the hydrophobic interior of the plasma membrane.
Definition
Integral
Term
Plants cells in hypotonic solutions become ________.
Definition
Turgid
Term

Solution that has a lower solute concentration than that found inside the cell.

 

Resulting in water flow into the cell.

Definition
Hypotonic
Term

Model of cell membrane structure supported by current evidence.

 

States that proteins freely "float" within the bilayer "ocean".

Definition
Fluid Mosaic
Term
Differences in the concentration of molecules between two areas of a solution is called a concentration _________.
Definition
Gradient
Term
Diffusion of water across a selectively (semi) permeable membrane due to differences in the concentrations of solutions of each side of that membrane.
Definition
Osmosis
Term
Type of endocytosis that triggers the formation of coated pits on the plasma membrane.
Definition
Receptor Mediated
Term
Plant cells in hypertonic solutions become ________.
Definition
Plasmolysed
Term
Type of transmembrane protein that passes positively charged hydrogen ions across a membrane.
Definition
Proton
Term
Proteins that attach to the surface of the plasma membrane are called __________.
Definition
Periferal (sp? - peripheral)
Term
Type of transport across the plasma membrane with the help of transport proteins that requires energy.
Definition
Active
Term
Type of lipids that form each half of the cell membrane.
Definition
Phospholipids
Term
In animal cells, the fluidity of the membrane is also dependent on this chemical factor.
Definition
Cholesterol
Term
Side of the fracture facing the exterior environment.
Definition
Eface
Term

Solution that has the same solute concentration of that found inside the cell.

 

Resulting in no water flow.

Definition
Isotonic
Term
__________ or electrically neautral molecules can easily pass through the plasma membrane.
Definition
Hydrophobic
Term
Exporting of macromolecules from the cell via fusion of vesicles with the plasma membrane.
Definition
Exocytosis
Term
Membrane that separates the cell from its non-living surroundings.
Definition
Plasma
Term
Side of the fracture facing the plasma membrane.
Definition
Pface
Term
What are cell membranes composed of?
Definition
Phospholipids
Term
Why are cell membranes a bi-layer?
Definition
The phospholipids are arranged as a bilayer (two molecules thick). The phospholipids are stacked with the non-polar hydrocarbon chains pointed inward while the polar ends act as the external surface as shown in graphic on the left. The structure of the bilayer is another application of the solubility principle of "likes dissolve likes".
Term
Which parts of the bilayer are hydrophobic?
Definition
The tails
Term
Which parts of the bilayer are hydrophilic?
Definition
The heads
Term
Are cell membranes amphipathic?
Definition
Yes, because the phospholipids have hydrophobic tails and hydrophilic heads.
Term
What does selectively or semi-permeable mean?
Definition
Cell membrane has some control over what can cross it, so that only certain molecules either enter or leave the cell.
Term
Why is selectively or semi-permeable an important property of cell membranes?
Definition
Maintain homeostasis
Term
What is the fluid mosaic model?
Definition
Proteins embedded in the phospholipid bilayer of the membrane.

Membrane is a mosaic of proteins that float around in the bilayer.
Term
What other evidence supports the fluid mosaic model?
Definition
Experimental evidence for the “fluid” property of membranes:
1. Mark proteins on cells with different fluorescent dyes.
2. Fuse the cells to form “hybrids”.
3. Observe migration and mixing of proteins
Term
Name an environmental factor that can alter membrane fluidity.
Definition
Temperature
Term
How can animals adjust the fluidity of the plasma membrane?
Definition
Cholesterol
Term
How can plants adjust the fluidity of the plasma membrane?
Definition
Unsaturated fat
Term
What are some of the functions of integral membrane proteins?
Definition
Transport
Enzymatic activity
Signal tranduction
Intercellular joining
Cell-cell recognition
Attachment to the cytoskeleton and extracellular matrix
Term
Why is adjusting the fluidity of the plasma membrane important?
Definition
In order to work properly, membranes must remain fluid.

Cells alter lipid composition of membranes to cope with changes in fluidity due to temperature flux.
Term
What are some of the functions of peripheral membrane proteins?
Definition
Some peripheral proteins may serve the role of enzymes. Others are involved in changing cell shape during cell division & muscle contraction, or linking cells together.
Term
What are transport proteins?
Definition
Integral Membrane Proteins (IMPs) that transport specific molecules or ions across biological membranes
Term
What would happen if I placed a cell in an isotonic solution?
Definition
Nothing because there is no difference in the concentration gradient
Term
What would happen if I placed a cell in an hypotonic solution?
Definition
The cell would burst (lyse) because water would rush into the cell to dilute its higher concentration of solutes
Term
What would happen if I placed a cell in an hypertonic solution?
Definition
The cell would shrink because water flows out to dilute the surrounding areas of higher solute concentration
Term
What is osmotic concentration?
Definition
The total solute concentration of a solution
Term
What is osmotic pressure?
Definition
The pressure exerted by water flowing into a hypeertonic solution across a spm.
Term
What is reverse osmosis?
Definition
The reversal of osmosis by exerting more pressure than the osmotic pressure o the hypertonic side of a spm.
Term
What happens as a result of reverse osmosis?
Definition
Water flow in the opposite direction of that due to osmosis
Term
How is facilitated diffusion different from diffusion?
Definition
Facilitated diffusion is the diffusion of solutes across a membrane with the help of transport proteins; whereas diffusion is the action of molecules of any substance spreading outin available space.
Term
How does a Sodium Potassium pump work?
Definition
It is an electrogenic pump that generates electrochemical gradient by pumping two K+ ions inside for every three Na+ ions that it moves out (Animals)
Term
What is the function of a Sodium Potassium pump?
Definition
Sodium and potassium ions are pumped in opposite directions across the membrane building up a chemical and electrical gradient for each. These gradients can be used to drive other transport processes. In nerve cells the pump is used to generate gradients of both sodium and potassium ions. These gradients are used to propagate electrical signals that travel along nerves.
Term
What is an electrochemical gradient similar to that we use in our everyday lives?
Definition
Term
What is an electrogenic pump?
Definition
Special tranport proteins that generate voltage gradients across a membrane
Term
Give an example of an electrogenic pump in animals and in plants.
Definition
Animals - Sodium Potassium Pump
Plants - Proton Pump
Term
What is co-transport?
Definition
An ATP-powered pump that transports one solute can indirectly drive the active transport of several other solutes via a different protein
Term
How does co-transport work?
Definition
As H+ leaks back across membrane (with the gradient) through special transport proteins it carries other substances with it (sucrose; against the gradient)
Term
Compare and contrast the three types of endocytosis.
Definition
1. Phagocytosis- Process of engulfing a particle by wrapping pseudopodia around it forming a vacuole
(Phago: Eat)

2. Pinocytosis- indiscriminant engulfing of extracellular fluid by the plasma membrane; forming small vesicles
(Pino: drink)

3. Receptor mediated endocytosis- when specific molecules bind to specialized receptors on the cell's surface it activates coat proteins to form vesicles containing the bound molecules
Term
What are pseudopodia?
Definition
Extensions of the cytoplasm from the plasma membrane forned by cytoplasmic streaming
Term
What are pseudopodia used for?
Definition
Particles in the engulfed vacuole are digested by fusing with a lysosome
Term
The sodium-potassium pump is called an electrogenic pump because it
Definition

pumps hydrogen ions into the cell

 

contributes to the membrane potential.

 

pumps equal quantities of Na+ and K+ across the membrane

 

ionizes sodium and potassium

 

pumps hydrogen ions into the cell

Term
Which of the following would indicate that facilitated diffusion was taking place?
Definition
A substance was slowing as it moved down its concentration gradient
 
 
Term
All of the following cellular activities require ATP energy except
Definition

cytoplasmic streaming

 

exocytosis

 

movement of O2 into the cell.

 

protein synthesis

 

Na+ ions moving out of the cell

Term
Mutant cells lacking coated pits would most likely be
Definition
unable to actively transport ions into the cell
 
characterized by a smooth surface on both sides of the bilayer
 
unable to adapt to the cold
 
deficient in receptor-mediated endocytosis.
 
involved in steroid synthesis
 
Term
The movement of a substance across a biological membrane against its concentration gradient with the help of energy input is which of the following?
Definition

osmosis

active transport.

diffusion

exocytosis

facilitated diffusion

Term
All of the following statements about membrane structure and function are true except:
Definition

voltage across the membrane depends on an unequal distribution of ions across the plasma membrane

 

special membrane proteins can cotransport two solutes by coupling diffusion with active transport

 

both sides of a membrane are identical in structure and function.

 

diffusion of gases is faster in air than across membranes

 

diffusion, osmosis, and facilitated diffusion do not require any energy input from the cell

Term
Of the following functions, the glycoproteins and glycolipids of animal cell membranes are most important for
Definition

facilitated diffusion of molecules down their concentration gradients

 

the ability of cells to recognize like and different cells.

 

active transport of molecules against their concentration gradients

 

maintaining membrane fluidity at low temperatures

 

maintaining the integrity of a fuid mosaic membrane

Term
What is one of the ways that the membranes of winter wheat are able to remain fluid when it is extremely cold?
Definition

by increasing the percentage of unsaturated phospholipids in the membrane.

 

by decreasing the number of hydrophobic proteins in the membrane

 

by increasing the percentage of cholesterol molecules in the membrane

 

A, B, and C

 

A and B

Term
The movement of potassium into or out of an animal cell requires
Definition

plant hormones embedded in the cell membrane

 

high cellular concentrations of potassium

 

glucose for binding and releasing ions

 

low cellular concentrations of sodium

 

an energy source such as ATP or a proton gradient.

Term
All of the following processes take material into cells except
Definition

pinocytosis

carrier-facilitated diffusion

exocytosis.

active transport

endocytosis

Supporting users have an ad free experience!