Cell Biology Flashcards
What is the cell membrane made out of, and which way does each component face?
- double layer of phospholipids
- polar head faces outwards towards water, and non-polar tails face each other at the centre of the membrane
What are other molecules embedded inside the cell membrane used for?
Transport, recognition, etc.
The cell membrane is s____ p____. What does that mean?
- selectively permeable
- certain molecules can pass through, while others cannot
Three types of passive transport
Diffusion, osmosis, and facilitated diffusion
What is passive transport?
- A process that does not require energy from the cell
What is diffusion?
- It is the natural movement of particles from areas of high concentration, two areas of low concentration
- cell membrane can’t prevent passive transport if it is permeable to a substance (oxygen, CO2, lipid soluble molecules)
- Moving down or following the concentration gradient
What is the concentration gradient?
- The gradient is a difference in a quality between two adjacent regions
What is osmosis?
- osmosis is the diffusion of water (solvent) across a semi-permeable membrane
Describe when a cell is isotonic to surround fluid
- if [water] outside cell = [water] inside cell
- water movement in and out are equal
Describe when the cell is hypertonic to surrounding fluid
If [water] outside cell > [water] inside cell
- water moves into cell
- freshwater extracellular fluid is hypotonic
- cell swells and possibly bursts
Describe when a cell is hypotonic to surrounding fluid
If [water] inside cell > [water] outside cell
- water moves out of cell
- salty extracellular fluid is hypertonic
- cell shrinks as water moves out
Which direction does water move towards in osmosis?
- water moves towards a hypertonic solution until an equilibrium is reached
Describe facilitated diffusion
- passive transport
- movement of particles across the membrane, down the concentration gradient
- aided by a membrane protein
Ex. Glucose and other carbohydrates as too large for simple diffusion through the membrane
What is special about membrane proteins?
- they are very selective based upon shape, size, and electrical charge
- they only help a certain molecule through the membrane
Two types of membrane proteins that help in transport
Carrier proteins and channel proteins
What are channel proteins?
- tunnel-shaped protein through cell membrane
- have a charge
- positive channel specific for negative ion or molecule to pass
- negative channel specific for positive ion or molecule to pass
Types of proteins embedded in the phospholipids of cell membranes
- receptor proteins
- transport proteins (carrier and channel)
- Recognition protein
- enzymatic protein
Receptor proteins
- has a specific site that allows a specific molecule to bind to it
- A chemical messenger or hormone must fit the receptor site in order to affect the metabolism of the target cell
Carrier protein
- has a specific shaped site(s) of attachment
- combines with a molecule like glucose, or ions like Na+ and k+ and moves them across the membrane
Recognition protein
- has a specific carbohydrate chain attached to it
- chain is different for each person
- identifies that the cell belongs in your body
- your immune system under normal circumstances will only attack a foreign invaders such as a virus, or cells that aren’t yours
Enzymatic proteins
- when activated, it causes a reaction to occur that will affect the metabolism of the cell
- reaction occurs on the cytoplasm side of the proteins in the cytoplasm