BIO130 - Exam 2 - Lecture 1

Structure and Function of Plasma Membranes

Plasma Membrane

Described by “Fluid Mosaic Model”
Mosaic - because many different components
Fluid - because lipids + proteins are not covalently attached to each other and move laterally

Parts of Plasma Membrane

Phospholipids, Cholesterol, Integral Membrane Proteins, Carbohydrates

Phospholipids

Building blocks and forms bilayer

Cholesterol

Stabilizes bilayer temperature

Integral membrane proteins

amino acids interact with hydrophobic lipids to anchor in membrane

Carbohydrates

glycoprotein (sugar on protein)
glycolipid (sugar on lipid)

creates a hydrophilic coating that attracts water

Passive Transport

Movements of materials that does not require energy

Diffusion

Solutes (subtances dissolved in liquid) move from high to lower concentration
“Down” their concentration gradient

Selective Permeability

The plasma membrane allows for certain atoms/molecules to move across it, but most can’t

Facilitated Transport

Channel or carrier proteins allow for movement of solutes across the plasma membrane

Down their concentration gradient

Channels are faster than carriers

can be open or gated

Osmosis

movement of water through a selectively permeable membrane from an area of low solute concentration to an area of high solute concentration

Aquaporins

plasma membrane allows movement of water via osmosis due to aquaporins

movements depends on amount of solute in surrounding solution

Hypotonic Solution

Surroundings have fewer solutes that inside of cell

Water moves into cell, cells swell and can burst

Bad for animal cells, good for plant cells

Hypertonic Solution

surroundings have more solutes than inside of the cell

Water moves out of cell, cells shrivel

Isotonic solution

surroundings have the same amount of solute as inside of cell

Good for animal cells, bad for plant cells

no net movement

Active Transport

movement of materials that requires energy

Moves materials against a concentration gradient (from low to high)

can be one/few atoms/molecules at a time

Bulk Transport

Active Transport of large structures/quantities

2 types - endocytosis and exocytosis

Endocytosis

Moves substances into a cell, enters through vesicles or vacuoles

Phagocytosis - large structures

Pinocytosis - many small particles

Exocytosis

A type of active transport that moves substances out of the cell

Exits from vesicles