Cell membranes Flashcards
What is the cell-surface membrane?
The very thin structure around an individual cell
What do electron micrograph show the cell-surface membrane consisting of?
A double layer of phospholipid molecules tightly packed together
What are embedded in the phospholipid molecules?
Bigger protein molecules
What do some proteins do?
Go all the way through the membrane and some only go half way
What has the same structure as the cell-surface membrane?
Membranes surrounding the organelles inside cells
What is another name for cell-surface membranes?
Plasma membranes
What is the name for the membrane only allowing certain substances through it?
A partially permeable membrane
By how many methods do substances pass through membranes?
4 methods
What are the particles of liquids and gases constantly doing?
Moving about
What does the movement of liquid and gas particles cause?
It causes the particles to spread from an area of higher concentration to an area of lower concentration
Particles will diffuse through the cell membrane as long as what?
As long as they are small enough to pass through the very small gaps between the phospholipid molecules.
Which molecules can diffuse through the cell membrane?
Water, oxygen and carbon dioxide molecules
What doesn’t the cell need to provide for diffusion?
Energy
What is the difference in concentration called?
Sometimes called a concentration gradient (so a big difference in concentration is a big concentration gradient))
What is osmosis?
The diffusion of water molecules across a partially permeable membrane from a region of higher concentration of water molecules to a region of lower concentration of water molecules
