5.1-5.9 Flashcards
What is the fluid mosaic model?
Membrane’s structure; fluid phospholipid bilayer.
What is a quality of all cellular/plasma membranes
selective permeability (lets some substances cross more easily than others)
What is the outer layer of the cell membrane called?
Extracellular side
What is the inner layer of the cell membrane called?
Cytoplasmic side
What molecules can diffuse the lipid bilayer?
Small, nonpolar molecules (like CO2, O2)
What keeps a membrane fluid?
Kinks in the unsaturated tails of some phospholipids and the presence of cholesterol (in animal cells) keep phospholipids from packing too tightly.
What is the function of a junction protein?
Membrane proteins that can “attach” adjacent cells.
What is the function of a glycoprotein?
Protein that recognizes neighboring cell (with attached sugars)
What is the function of an active transport protein?
Transport proteins allow specific ions or molecules to enter or exit the cell.
What is the function of a channel protein?
Allow in certain molecules through faciliated diffusion
What is the function of a receptor protein?
Signaling molecules bind to receptor proteins, which relay the message by activating other molecules inside the cell.
What is the function of an attachment protein?
proteins that attach to the extracellular matrix and cytoskeleton and help support the membrane and can coordinate external and internal changes.
What is the final type of protein found in cell membranes (mentioned in the book).
Enzymes. React inside of the cell.
Identify the six different types of functions of proteins in a plasma membrane.
Attachment to the cytoskeleton and ECM, signal reception and relay, enzymatic activity, cell-cell recognition, intercellular joining, and transport.
Why are phospholipids important in evolution?
They naturally form a bilayer with water in the center. This plasma membrane was essential to the development of cells.
In the origin of a cell, why would the formation of a simple lipid bilayer membrane not be sufficient? What else would have to be a part of such membrane?
They would need embedded proteins that could regulate the movement of substances into and out of the cell.
Diffusion is a result of____
thermal energy; imbalanced concentrations
Define diffusion
the tendency for particles of any substance to spread out into the available space.
What will there always be in diffusion?
net positive movement to the area with a lower concentration
What is equilibrium, in diffusion
Equal distribution
Concentration gradient?
the process of particles, which are sometimes called solutes, moving through a solution or gas from an area with a higher number of particles to an area with a lower number of particles
Passive transport
where molecules do not have to work to diffuse themselves.
Why is diffusion across a membrane called passive transport?
The cell does not expand energy to spread it,
Osmosis
the diffusion of water over a selectively permeable membrane. Water will move so there is an equal concentration of solute across two membranes.
Why are free water molecules important in osmosis?
They can move concentration gradients. Their polarity is bonds them to the solute– but if there is not enough solute, they move.
Which would move to which: 0.5% sucrose solution and a 2% sucrose solution
0.5 __> 2.
Define tonicity
the ability of a surrounding solution to cause a cell to gain or lose water.
What happens when you submerge a cell in a solution with the same tonicity as it? (isotonic)
The volume remains constant; H20 is constantly leaving or entering, but at equal rates.
Define hypotonic
Lower solute concentration, gives water.
Define hypertonic
Higher solute concentration, takes water.
What is the control of water concentration called?
osmoregulation. Ex. A trout lives in a very hypotonic environment. It’s kidneys work to remove excess water.
What is the name for an isotonic plant cell?
flaccid, as opposed to turgid or shriveled.
What regulates water concentration in plant cells?
Turgor pressure, turgid. Prevents too much water from entering
What is plasmolysis?
When an organism is placed in a hypertonic environment and its cells lose water and shrivel. This causes plants to wilt and die.
What is facilitated diffusion.
A type of passive transport in which polar molecules and ions enter/exit through a channel in a cell membrane.
What molecules does facilitated diffusion bring across?
Ions and hydrophilic molecules. Ex. sugars, amino acids, water.
How does facilitated diffusion work?
A transport protein forms a channel that allows molecules and atoms to come through and lower the outer concentration gradient..
What is aquaporin?
A transport protein that allows for water to flow in and out of a cell.
How do transport proteins contribute to a membrane’s selective permeability?
Because they are specific for the solutes they transport, the numbers and kinds of transport proteins affect a membrane’s permeability to various solutes.
Why are aquaporins important in kidney cells?
Kidney cells must reabsorb a large amount of water when producing urine.
Define active transport
a process in which a cell expends energy to move a solute against its concentration gradient. Needs ATP or other energy storing molecule.
In the potassium sodium pump, inside has which?
Inside has potassium (K+) outside has sodium (Na+)
What the distribution of sodium and potassium important for?
Nerve signaling.
Remember to look at the sodium-potassium pump process!
Define exocytosis
The process of exporting bulky materials such as proteins or polysaccharides.
Describe exocytosis.
A transport vessel filled with macromolecules comes from the golgi apparatus and fuses with the plasma membrane, and spits out its contents.
Give an example of exocytosis
The pancreas makes insulin. it is secreted into extracellular fluid by exocytosis, integrating itself into the bloodstream.
Define endocytosis
An process in which a cell takes in large molecules. (Endo=inside)
What are the two types of endocytosis?
Phagocytosis and receptor-mediated endocytosis. (pinocytosis)
Describe the process of phagocytosis.
A cell engulfs a certain molecule with extensions called pseudopodia (singular: pseudopodium), and then encloses it in a sac, called a vacuole. The vacuole fuses with a lysosome, whose hydrolytic enzymes digest the contents of the vacuole. Also called “cellular eating”
Give an example of phagocytosis.
Protists (like amobea) take in food this way. White blood cells deal with invading bacteria.
Describe the process of receptor-mediated endocytosis.
The receptor proteins embedded in the cellular membrane (covered by a layer of coat proteins, which indent where the receptor proteins are). These receptors pick up certain molecules from extracellular fluid. Once connected, the coat pinches closed and takes the molecule in.
Give an example of R-M endocytosis
Cholesterol from the blood is taken using this. In the blood, cholesterol is within molecules called low-density lipoproteins (LDLs), which can bind to receptor proteins.
As a cell grows, its plasma membrane expands. Does this involve endocytosis or exocytosis? Explain.
Exocytosis: When a transport vesicle fuses with the plasma membrane, its contents are released and the vesicle membrane adds to the plasma membrane.
