Biology 1.2.4 - Cell Transport

Membrane

• made up of a bilayer of phospholipids

• mostly phospholipids, then proteins, cholesterol, and sugars

• Phospholipids are selectively permeable based on their rotation:

• creates an entrance with heads on the outside and tails on the inside

  Proteins in the membrane

• act as doors for material exchange

• provides a passage through the membrane

  Cholesterol in the membrane

• cholesterol keeps the balance of liquid and solid in the membrane

  Carbohydrates in the membrane

• referred to as “membrane sugars” even though they are polysaccharides

• Membrane sugars identify things in the cell

• called glycoprotein when on a protein, called glycolipid when on a lipid

passive transport

• if a molecule passes through the membrane it is called passive transport

• they will pass through transport proteins called channel proteins

• water will try to dilute an area with more molecules inside it - called osmosis

  

• Goes from hypotonic solution - fewer molecules within it to hypertonic solution - more molecules within it. once this process is complete the solutions are called isotonic meaning they have equal ratios of molecules.

• When a plant cell is within a hypertonic solution during osmosis it collapses - called plasmolysis, also known as wilting

• In a hypotonic solution, an animal cell will burst in lysis, but a plant cell will be saved from the cell wall, but will still have water in it. This state of a cell is called turgid and it is very beneficial for a plant.

Active Transport

• molecules move through cells using energy or ATP

• molecules move through diffusion using active transport, sometimes they need carrier proteins or protein pumps

• The most important carrier protein is the sodium-potassium pump

• endocytosis - brings large substances into the cell

• phagocytosis - larger substances are pulled in for digestion

• pinocytosis - drops of liquid are pulled in for osmoregulation

• exocytosis - takes large substances out of the cell