BSC2085 UNIT 2

cell theory

- cells are the building blocks of all plants and animals

- all cells come form the division of pre-existing

- cells are the smallest units that perform all vital physiological functions

- each cell maintains homeostasis at the cellular level

somatic cells

these include all cells in the body except the ones created by meiosis

sex cells

also known as germ cells

the cell is surrounded by

plasma/cell membrane

cell membrane

defines cell boundaries and is made of proteins and lipids, composition can very depending on the region of the cell

cytoplasm

region between the plasma membrane and nucleus, contains organelles and ICF/cytosol

extracellular fluid (ECF)

located outside of cells

functions of the plasma membrane

physical barrier, regulates entry/exit of material for the cell, responds to changes in the ECF, provides support to the cell by controlling shape and what the cell binds to

phospholipids for plasma membrane

75% of membrane lipids, amphipathic molecules arranged in a bilayer

What are the components of a phospholipid?

Hydrophilic heads and hydrophobic tails

Which direction do the hydrophilic heads face in a membrane?

They face the water on each side of the membrane

Which direction do the hydrophobic tails face in a membrane?

They face the inside of the membrane away from water

cholesterol

20% of membrane lipids, holds phospholipids still and can stiffen or loosen the membrane

glycolipids

lipid with a carbohydrate attached to the outside

glycolcalyx

carbohydrate component of glycolipids and glycoproteins

functions of glycocalyx

protection, immunity, defense against cancer, transplant compatibility, cell adhesion, fertilization, embryonic development

transmembrane proteins

pass completely through the membrane, most are glycoproteins

peripheral proteins

adhere to one face of the membrane, usually tethered to the cytoskeleton

membrane proteins- receptors

bind chemical signals to trigger internal changes, may cause the production of a second messenger

membrane proteins- enzymes

catalyze reactions like digestion of molecules and production of second messengers

membrane proteins- channel proteins

allow hydrophilic solutes and water to pass through the membrane, leak channels or gated channels

ligand gated channels

responds to chemical messengers

voltage gated channels

respond to charge changes

mechanically gated channels

respond to physical stress on cell

CAMs

cell adhesion molecules, mechanically link cell to another cell and to extracellular material

simple diffusion

net movement of particles from a place of high concentration to a place of low concentration without the need for energy input, air and water does not require a membrane

as temperature increases

motion of particles increases

molecular weight

smaller particles move faster

higher membrane surface area

faster gradient movement

osmosis

net flow of water through a selectively permeable membrane

aquaporins

channel proteins in the membrane that are specialized for water passage

osmotic pressure

hydrostatic pressure required to stop osmosis

hydrostatic pressure

fluid pressure on the membrane

reverse osmosis

process of applying mechanical pressure to override osmotic pressure

osmolarity

osmotic concentration

tonicity

ability of a surrounding solution to affect fluid volume and pressure in a cell

carrier-mediated transport

proteins (carriers) in cell membrane carry solutes into or out of cell (or organelle)

transport maximum

all of the carriers are occupied

uniport carriers

carrier that moves one type of solute

symport

carrier that moves two or more solutes simultaneously in same direction (cotransport)

antiport

carrier that moves two or more solutes in the opposite direction (countertransport)

facilitated diffusion

carrier moves its solute down its concentration gradient, does not consume ATP

primary active transport

carrier moves its solute up its concentration gradient, the carrier protein used ATP for energy

secondary active transport

carrier moves solute through membrane, but only uses ATP indirectly

sodium potassium pump

example of primary active transport, uses ATP to bring in 2 K and get rid of 3 NA

vesicular transport

moves large particles, fluid droplets, or numerous molecules at once through the membrane in vesicles

vesicles

bubble-like enclosures of membrane

endocytosis

brings materials into the cell (uses ATP)

exocytosis

releases material from the cell (uses ATP)

phagocytosis

engulfing and destroying large particles (cell eating)

pinocytosis

taking in droplets of EFC containing molecules useful in the cell, pinocytic vesicles in the cytoplasm (cell drinking)

receptor mediated endocytosis

particles bind to specific receptors on plasma membrane

transcytosis

transport of material across the cell by capturing it on one side and releasing to on the other

internalization

similar to endocytosis