AP BIO - Membranes

Covers mostly vocabulary: Diffusion, permeability, etc.

Passive transport

the spontaneous movement of molecules across a membrane from an area of high concentration to an area of low concentration, driven by a concentration gradient, and without the cell expending energy

Active transport

the movement of molecules across a cell membrane from an area of low concentration to an area of high concentration, against a concentration gradient. This process requires energy,

Equilibrium

The state in which a substance is equally distributed throughout a space

Permeability

The quality of a membrane which allows substances to pass though it

Semipermeable

permeable to certain substances and not others (EX: some things can fit through a door, but not others)

Concentration Gradient

A region of space over which the concentration of a substance changes

Diffusion

The natural movement of particles from a high to low concentration to achieve equilibrium

Extracellular space

Space surrounding a cell

Extracellular Matrix (EMC)

Most animal cells release materials into the extracellular space, creating a complex mesh work of proteins and carbohydrates. 

Plasma Membrane

a phospholipid bilayer with the consistency of salad oil, which protects the cell and allows it to interact with it’s surroundings in a controlled manner (excludes, takes in, and excretes) 

Osmosis

is the net movement of a solvent, usually water, across a semi-permeable membrane from an area of higher water concentration to an area of lower water concentration to equalize the solute concentrations on both sides

Amphipathic

a type of molecule that has both hydrophilic and hydrophobic regions (like phospholipids)

Fluid Mosaic Model

A phospholipid bilayer, separating the inside of a cell from the outside, which contains a “mosaic” of proteins and other particles which serve specific purposes within the membrane

Integral proteins

completely submerged inside the membrane, very difficult to remove (channel proteins, carrier proteins, glycoproteins)

Channel Proteins

Integral proteins which allow items which cannot permeate the membrane to enter the cell. These can also pump out, and require no ATP.

Carrier Proteins

A type of integral proteins which will see something a cell needs and allow it to enter the cell safely. These can go against the concentration gradient and DO require ATP

Glycoproteins

Technically an integral protein, which is made up of a chain of sugars (glyco-) attached to a protein which allows a cell to recognize another cell. (can be attached to any other the previous mentioned integral proteins)

Peripheral Proteins

located on the periphery of the membrane/other proteins, can attach/detach themselves at will, generally there for cell functions such as hormones, etc.

Lipid-bound proteins

A very rare type of protein, located inside the lipid bilayer. Rare because membrane proteins are there to interact with the outside/inside of the cell, these guys can do neither and really serve no purpose.

Water Potential

The potential energy of water per unit area compared to pure water. Allows us to figure out if water is going to flow into the cell or not. 

Pure water= 0 bars

ψs+Ψp=Ψ

Solute Potential

the effect of dissolved solutes on the water potential of a solution

Turgor pressure

the internal force within plant cells that pushes the plasma membrane against the rigid cell wall, a result of water uptake via osmosis

ATP

Adenosine triphosphate, the primary energy carrier in living things

Plasmolysis

When a plant, fungi, or prokaryotic cell are placed in a hypertonic solution and their cytoplasm shrivels and breaks away from their cell wall.

Hypertonic Solution

a solution with more solutes in it then the inside of a cell. Will result in osmosis out of the cell and into the solution, shriveling the cell.

Hypotonic Solution

a solution with less solutes in it then the inside of a cell. Will result in osmosis into the cell from the solution, possibly lysing the cell in the process.

Isotonic

solutions that have the same solute concentration as another solution, typically inside a cell, leading to no net movement of water across a semipermeable membrane

Endocytosis

The process by which cells internalize substances by engulfing them in a membrane-bound vesicle. Bonus: what are the two types of endocytosis?

Phagocytosis

a form of endocytosis where the cell engulfs large particles or microorganisms, forming a phagosome. (phago = eat, cytosis = cell)

Pinocytosis

a form of endocytosis in which the cell engulfs small amounts of liquid and solutes, forming a pinocytotic vesicle. (pino = drink, cytosis = cell)

Cholesterol as a temperature buffer

• if the temperature is too high for the membrane, cholesterol decrease fluidity

• if the temperature is too low for the membrane, cholesterol increases fluidity

The Plant Cell wall is what?

a structural boundary that protects and maintains the shape of the cell and a permeable barrier The cell wall is made of cellulose (a polysaccharide)

Fungi Cell wall

The fungi cell wall is made of chitin (a polysaccharide)

The prokaryotic cell wall

is made of peptidoglycan, which is a polymer of sugar and amino acids.

Plasmodesmata

small holes between the plant cells that allow the transfer of nutrients, waste, and ions

Osmolarity

the total solute concentration in a solution

lucasite

a white blood cell which rolls/velcros along the blood vessel (think a tennis ball on Velcro)