Membrane transport Flashcards
What is the function of the plasma membrane?
Forms a barrier between the cytoplasm and the environment
What is the plasma membrane made up of?
Phospholipids.
How do the hydrophobic tails and hydrophilic heads of phospholipids arrange themselves in the bilayer?
Hydrophobic fatty acid tails face inwards
What is the function of the phospholipid bilayer?
Forms a barrier between water-soluble molecules and maintains different environments on each side of the membrane.
Why is the cell membrane described as fluid?
Molecules in the membrane can move freely.
What is the role of cholesterol in the cell membrane?
Cholesterol fits between fatty acid tails
What is the role of channel proteins?
Allow transport across the membrane by facilitated diffusion (intrinsic proteins).
What is the role of carrier proteins?
Allow transport across the membrane by moving charged particles from one side of the membrane to the other (intrinsic proteins).
What is the role of glycoproteins?
Proteins with attached carbohydrate parts involved in cell recognition
What is diffusion?
The net movement of molecules or ions from an area of high concentration to low concentration through a partially permeable membrane until dynamic equilibrium is reached.
Why does diffusion occur?
Particles have kinetic energy
What does diffusion result in?
Dynamic equilibrium
What factors affect the rate of diffusion?
Concentration gradient
What is Fick’s Law of Diffusion?
Diffusion ∝ (surface area × difference in concentration) / length of diffusion path.
What is facilitated diffusion?
The movement of water-soluble
How do channel proteins assist in facilitated diffusion?
They allow specific water-soluble ions and molecules to pass through; channels are only open for specific molecules.
How do carrier proteins assist in facilitated diffusion?
Carrier proteins bind to specific molecules
What is osmosis?
The movement of water from a region of high water potential to low water potential through a partially permeable membrane until dynamic equilibrium is reached.
What happens to cells in a hypertonic solution?
In plant cells: water moves out
What happens to cells in a hypotonic solution?
In plant cells: water moves in
What happens to cells in an isotonic solution?
Dynamic equilibrium is reached; no net water movement occurs.
What is active transport?
The movement of molecules or ions against a concentration gradient using energy in the form of ATP and requiring carrier proteins.
How does active transport occur?
A molecule binds to a carrier protein. ATP binds
What are the types of active transport?
Uniport (single molecule)
What is endocytosis?
The process where materials are surrounded by the membrane and taken into the cell.
What is exocytosis?
The process where a membrane-bound vesicle empties its contents outside the cell.
What is phagocytosis?
“Cell eating
What is pinocytosis?
“Cell drinking
What is the difference between diffusion and active transport?
Diffusion moves molecules down the concentration gradient and does not require energy. Active transport moves molecules up the concentration gradient and requires ATP and carrier proteins.
