Cell membrane and Transport Flashcards
(15 cards)
What is the primary function of the cell membrane?
The selective transport of materials across into and out of the cell
Other functions include recognition of other cells and providing attachment sites for enzymes and hormones.
What model describes the structure of the cell membrane?
The fluid mosaic model
This model illustrates that membranes consist of a flexible double layer of lipids with embedded specialized molecules.
What are the two main components of a phospholipid molecule?
A hydrophilic head and two hydrophobic tails
Unbroken is saturated and broken is unsaturated
The head is attracted to water, while the tails repel water.
What is passive transport?
Movement of substances that does not require energy
Materials move down a concentration gradient from an area of high concentration to low concentration.
Define diffusion.
The net movement of particles from a region of high particle concentration to a region of lower particle concentration
This process continues until equilibrium is reached.
What is facilitated diffusion?
A process where carrier and channel proteins help transport substances across the membrane from low to gigh conc. without using energy
This is necessary for charged particles and larger molecules that cannot pass through the phospholipid bilayer directly.
What is osmosis?
The diffusion of water through a semipermeable membrane and down its concentration gradient
Water is often described as the universal solvent.
Sugar solute
make solution
What is the difference between a hypotonic and a hypertonic solution?
Hypotonic; lower solute conc. outside of cell than inside cell. Water moves inrto cell
hypertonic; have a higher concentration of solute outside of cell than inside. Water moves out of cell
This affects the movement of water across cell membranes.
What type of transport requires energy in the form of ATP?
Active transport
This process moves substances from areas of low concentration to areas of high concentration.
What is endocytosis?
The process by which large molecules or particles are engulfed by the cell membrane and brought into the cell
This includes processes like phagocytosis and pinocytosis.
What is exocytosis?
The process by which moves large substances are expelled from the cell
This often involves hormones, mucus, and digestive enzymes.
What factors affect the exchange of materials across the cell membrane?
Characteristics of the selectively permeable membrane and the physical and chemical properties of the substance
These include size, charge, and concentration gradient.
What is the significance of surface-area-to-volume ratios in cells?
Cells with a larger surface-area-to-volume ratio can obtain nutrients and remove wastes more efficiently
This is critical for cellular function and survival.
Fill in the blank: The lipid bilayer is composed of subunits called _______.
phospholipids
What does cholesterol do
helps to maintain cell membrane stability at varying temperatures.
