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Justin Krier
Period 4
Membranes
1. What does selective permeability mean and why is that important to cells?
Diffusion lets objects go from an area of high concentration to lower
concentration. Selective permeability is important to cells because it lets certain
objects in and out of a cell during diffusion.
2. What is an amphipathic molecule?
An amphipathic molecule is a molecule with two parts one that is polar and one
that is not. The polar side is hydrophilic and the non polar side is hydrophobic.
3. How is the fluidity of cell’s membrane maintained?
Temperature and cholesterol effect the fluidity of a cells membrane remaining
maintained. This is because cholesterol acts as a buffer and higher temperatures
create more fluidity
extracellular matrix – extracellular matrix creates structure in a animal cell.
carbohydrate – chemical messenger
glycoprotein – cell to cell recognition
cytoskeleton – cell structure
cholesterol – controls cell fluidity
glycolipid – cell to cell recognition
integral protein – channel for transportation of proteins through cell
peripheral protein – cell recognition
4. List the six broad functions of membrane proteins.
1)Transport,
2)Enzymatic activity
3)Signal transduction
4)cell to cell recognition
5)intercellular joining
6)attaching to the cytoskeleton or the extracellular matrix
5. How do glycolipids and glycoproteins help in cell to cell recognition?
Glycolipids and glycoproteins are for cell to cell recognition as an “ID tag” so that
one molecule knows that another molecule I meant to be there and will not attack
the molecule.
6. Why is membrane sidedness an important concept in cell biology?
it is an important concept in cell biology fro membranes to have multiple sides
because of processes like creation of vesicles through the process of
endocytosis and exocytosis.
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7. What is diffusion and how does a concentration gradient relate to passive
transport?
Diffusion is when anything but water goes from an area of high concentration to
low concentration. The objects moving in and out of the cell because of the
concentration gradient in and out of the cell causes passive transport because it
uses no energy to pass objects in and out of a cell.
8. Why is free water concentration the “driving” force in osmosis?
Free water concentration creates the areas with higher and lower amounts of
water. This is the driving force in osmosis because osmosis is the movement of
water from areas of high concentration to areas of lower concentration.
9. Why is water balance different for cells that have walls as compared to cells
without walls?
Cells without a cell wall do best in an isotonic cell because and not a hypotonic
cell because the will burst. Whereas cells with a cell wall will do better in a
hypotonic solution because the structure of those cells will hold and the elasticity
of cells with a cell wall will not explode.
10. What is the relationship between ion channels, gated channels and facilitated
diffusion.
facilitated diffusion is the process of ions moving down a concentration gradient.
Ion channels are channels with water in them that allow ions through them. And
gated channels are a type of channel that can open and close to let ions through.
11. How is ATP specifically used in active transport?
ATP is used in active transport because a protein pump counteracts a
concentration gradient. Protein pumps are a form of active transport and require
ATP to force objects against the concentration gradient.
12. Define and contrast the following terms: membrane potential, electrochemical
gradient, electrogenic pump and proton pump.
Membrane potential- difference in electrical potential in membrane
Electrochemical gradient – concentration gradient of ions in and out of cell
Electrogenic pump – creates charge imbalance in the membrane
Proton pump – creates a charge imbalance across the cell membrane.
An electrogenic pump, proton pump and membrane potential happen within the
membrane where as a proton pump and electrochemical gradient are in and out
of the cell.
13. What is cotransport and why is an advantage in living systems?
Cotransport is the process of which a single ATP pump transports several
solutes in and out of a cell. This is an advantage to a cell because ig gets
multiple energy needing processes done with one.
14. What is a ligand?
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A Ligand binds to a receptor site of another molecule.
15. Contrast the following terms: phagocytosis, pinocytosis and receptor-mediated
endocytosis
Phagocytosis is the process where a cell “eats” engulfs a particle by wrapping
around it and putting it in a sac, then digesting it when the sac combines with
lysosomes. Pinocytosis the cell puts droplets of extracellular fluid in vesicles to
dissolve the molecule in droplets. Receptor mediated endocytosis uses parts of
the membrane to take large parts of the cell. These large parts of the cell are
receptor sites that aren’t very concentrated in the extracellular fluid and proteins
are embedded in the membrane at receptor cites.
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