Movement of molecules Flashcards
Diffusion
The movement of solute molecules in a solution from areas of high concentration to areas of low concentration
Types of gradients
Concentration gradient
Electrical gradient
Pressure gradient
Factors that influence the rate of diffusion and how
Steepness of concentration gradient - Bigger = faster
Temperature- Higher = atoms moving faster and diffuse more
Mass of diffusing substance - Larger mass = slower speed of diffusion
Surface area - Larger area = faster diffusion
Diffusion distance - Greater distance = slower diffusion
Active transport
Molecules moving against a gradient
Moving from low to high concentration
Require ATP
Forms of active transport
Pumps
Vesicle-mediated transport
Active transport pumps
Membrane transporters that move a substance against its concentration gradient
They concentrate substances on one side of the membrane as when storing ion inside an organelle
e.g Calcium pumps
Vesicle mediated active transport
Moves large volumes of molecules at once within a ball called a vesicle (made of phospholipids)
Exocytosis
Bulk secretion of substances such as hormones and neurotransmitters
Endocytosis
Movement into the cells
Passive transport
Transport down a gradient
Does not require energy
Types of passive transport
Simple diffusion
Facilitated diffusion
Osmosis
Simple diffusion
Molecules simply spread through membranes when the membrane is permeable to them
e.g gases and small uncharged molecules
Facilitated transport
When the membrane is impermeable to solutes, plasma proteins may assist Including channels and carriers
Allows for selective permeable characteristics of membrane
Facilitated transport with Channels
Channels allow only one type of solute to pass through e.g Ions
Gated channels may be open or closed and can trigger by a number of stimuli
Facilitated transport with carriers
Carriers attract and bind to the solute, change shape and release the solute out the other side e.g ions, glucose and drugs
