Lecture 16: cell transport

cell membrane

Made up of phospholipids in a phospholipid bilayer

role of cell membrane

• Keep internal and external environment separate

• Control what enters and exits

• Remain fluid to allow all parts to move around

parts of the cell membrane

• phospholipids

• proteins

• cholesterols

• glycolipids / glycoproteins

cholesterol in the cell membrane

keeps cell membrane fluid

glycolipids / glycoproteins in the cell membrane

proteins and lipids with sugars attached, helps identify the cell as being part of you

phospholipid bilayer

selectively permeable —> only lets certain things enter or exit the cell

proteins in the cell membrane

can help select objects move in and out the cell

solvent

the substance things are dissolved into (like water)

solute

substance being dissolved (like NaCl)

solution

solvent + solute

diffusion

Spontaneous movement of a substance from an area of high concentration to low concentration

osmosis

• Passive diffusion of water from a high water concentration to a low water concentration

• DOES NOT MOVE THE SOLUTE

movements that do not require energy

diffusion, osmosis, facilitated diffusion (channels)

movements that require energy

facilitated active transport (using pumps)

molecules that cannot cross the membrane

• ions (have charge)

• larger molecules (sugars, amino acids, nucleic acids)

facilitated diffusion

• uses channel proteins allow a specific molecule through

• facilitated = done by proteins

pumps during active transport

use ATP to move material up its concentration gradient

vescicles

• a smaller phospholipid bilayer used for transportation within the cell

• when the cell can’t rely on facilitated diffusion or active transport

exocytosis

Releasing a large amount of material outside the cell by fusing a vesicle with the cell membrane to release material

• e.g. LDL and HDL excreted by liver cells into the bloodstream

endocytosis

when the cell takes in a large amount of substances by engulfing them with the cell membrane, forming a vesicle

• e.g. immune system engulfing a bacteria for destruction

molecules that can pass the membrane without assistance

water (osmosis), small fat molecules, small gas molecules (oxygen, CO2)