The Cell

Cell theory

• the cell is the functional unit of life

• cells can only arise from pre-existing cells

• the function of the whole organism depends on the function of the cell and all its parts

all cells have

plasma membrane, cytoplasm, and nucleus

what is outside the cell?

extracellular fluid, cellular secretions, and extracellular matrix

the extracellular fluid consists of

interstitial fluid, blood plasma, and cerebrospinal fluid

interstitial fluid

fluid between cells

phospholipids

hydrophilic polar phosphate heads and hydrophobic nonpolar fatty acid tails

The plasma membrane is made of a

phospholipid bilayer, glycolipids, and cholesterol

Phospholipid bilayer forms a

passive barrier to transport water, large, or polar molecules

glycolipids

lipids with sugar groups

cholesterol in the plasma membrane increases

membrane stability

functions of the plasma membrane

selective permeability and cell signaling

transport proteins

channels in the plasma membrane

integral proteins

proteins that are integrated into the bilayer of the plasma membrane

peripheral proteins

enzymes that are attached to phosphate heads or anchored to integral proteins that anchor cytoskeletal elements

tight junctions

aka zipper proteins; form a barrier that prevents material and microbes from passing between cells

desmosomes

anchor cells together mechanically and transmit forces the cytoskeleton

gap junctions

form pore complexes (channels) between cells that allow materials to pass through

diffusion

The movement of molecules from areas of high concentration to low concentration until equilibrium is reached

The net rate of diffusion is proportional to

permeability, membrane surface area, and concentration gradient

the net rate of diffusion is inversely proportional to

distance

diffusion works best over

shorter distances

diffusion and osmosis are __ processes

passive

osmosis

the diffusion of water

aquaporin

water channel

Na+/K+ ATPase channels are a __ process

active

For every one ATP hydrolyzed, the Na+/K+ ATPase channels pump

3 Na+ out of the cell and 2 K+ into the cell