Plasma Membrane

plasma membrane

phospholipid bilayer + embedded proteins → separate intracellular environment from extracellular environment

intracellular

inside a cell

extracellular

outside a cell

selective permeability / semipermeable

property that ensures only specific substances pass across it.

phospholipid bilayer

an amphipathic molecule that makes the membrane stable

phospholipid bilayer structure

• hydrophilic phosphate head

• hydrophobic fatty acid tails

cholesterol

a steroid-alcohol that regulates fluidity in the P.M

protein channels

pores or holes in the membrane that let a specific substance through.

carbohydrate chains

• aid with cell-cell communication

• signalling

• recognition of self or non-self (foreign) molecules

• adhesion

glycolipid

a phospholipid bound to a carbohydrate.

• stabilises membrane

• acts as recognition site

glycoprotein

protein bound to a carbohydrate

• cell signaling

• cell-cell recognition

• cell adhesion

passive transport

movement of molecules through semipermeable membrane, down the concentration gradient without energy

active transport

movement of molecules across a semipermeable membrane that requires energy

diffusion

passive movement of molecules from areas of high concentration to areas of low concentration

concentration gradient

the difference in solute concentration between two adjacent areas

solute

a substance dissolved in the solvent

solvent

a liquid in which a solute is dissolved, forming a solution

nonpolar

a molecule without a clearly positive or negative end, generally hydrophobic

hydrophobic

water hating

hydrophilic

water loving

polar

a molecule with both a positive end and a negative end, tend to be hydrophilic

facilitated diffusion

the passive movement of molecules down their concentration gradient through a membrane-bound protein

carrier protein

membrane protein that undergoes conformational change to transport molecules across a membrane

osmosis

the diffusion of water across a selectively permeable membrane from areas of low solute concentration to areas of high solute concentration

tonicity

measure of the relative concentration of solutes on either side of a semipermeable membrane

hypertonic

a solution with a higher solute concentration when compared to another solution

isotonic

describes a solution with the same solute concentration as another solution

hypotonic

describes a solution with a lower solute concentration when compared to another solution

protein-mediated active transport

involves using membrane proteins to move molecules across a membrane against their concentration gradient

ATP

Molecule that can be used for energy

Exocytosis

exocytosis is the process by which the contents of a vesicle are released from a cell.

exocytosis steps

1 Vesicular transport – a vesicle containing secretory products is transported to the plasma membrane

2 Fusion – the membranes of the vesicle and cell fuse

3 Release – the secretory products are released from the vesicle and out of the cell.

endocytosis

endocytosis involves transporting large molecules or groups of molecules into the cell.

endocytosis steps

1 Fold – the plasma membrane folds inwards to form a cavity that fills with extracellular fluid and the target molecules.

2 Trap – the plasma membrane continues folding back on itself until the two ends of the membrane meet and fuse. This traps the target molecules inside the vesicle.

3 Bud – the vesicle (or endosome) pinches off from the membrane. It can then be transported to the appropriate cellular location or fused with a lysosome for digestion.

cytoskeleton

The cytoskeleton gives shape and support to the cell and transports molecules around the cell.