cell transport Flashcards
phospholipids
cell membrane is made of two layers of phospholipids.
There are small spaces between the phospholipids where gases and lipid soluble molecules can enter the cell.
phospholipid head
head end of the phospholipid is hydrophilic and faces the outside of the membrane
phospholipid tail
The tail end of the phospholipid is hydrophobic and faces the inside of the membrane.
Cholesterol
Embedded within the phospholipid bilayer to keep the membrane fluid.
Also makes cell membrane more permeable to water.
Channel Protein
Large protein which acts as a pore in the cell membrane.
Allows lipid soluble molecules to pass through.
Carrier Protein
Large protein which acts as a pore in the cell membrane to carry large or water soluble substances into or out of the cell.
Glycoprotein/Cell Identity Marker
Protein with a carbohydrate group attached which allows cells to tell self from non-self.
MOVEMENT OF SUBSTANCES
In most instances substances will want to move from where there is a greater concentration of the substance, to where there is a weaker concentration of the substance – this is called the concentration gradient.
PASSIVE TRANSPORT
substances pass through the cell membrane with out the cell having to use ATP energy
types of passive transport
diffusion, osmosis, facilitated diffusion,
active transport
When ATP energy is required to transport substances pass across the cell membrane.
active transports using carrier proteins
Transport of substances against the concentration gradient (from low to high concentration) using carrier proteins in the membrane.
Carrier proteins require ATP to pump against the gradient.
endocytosis
Endocytosis involves the cell absorbing large particles such as proteins (or even organisms) from the extracellular environment.
The substance is engulfed in the cell membrane, forming a vesicle which is absorbed
Pinocytosis & phagocytosis
Phagocytosis = cell eating e.g. iron, cells.
Pinocytosis = cell drinking e.g. lipids.
Exocytosis
Contents from a vesicle within the cell are passed to the outside of the cell.
The vesicle fuses with the cell membrane and pops, releasing its contents to the extracellular environment.
E.g. mucous, digestive enzymes.
Concentration Gradient
Differences in the concentration of substances in the intra and extracellular environment result in movement of molecules.
The larger the difference in concentration, the faster the substance will move.
Size
If a substance is large it cannot fit between the phospholipid to enter the cell and must use a carrier protein.
Therefore larger substances take longer to transport.
Solubility
The cell membrane is made of phospholipids.
If a substance is soluble in water it must use a channel protein as lipids repel water.
Water soluble substances take longer to transport than lipid soluble ones.
Hypertonic
a solution outside of a cell is called hypertonic if it has a greater concentration of solutes than the inside of the cell. This means water will move out of the cell.
Isotonic
a solution outside of a cell is called isotonic if the concentration of solutes is the same as the inside of the cell. Osmosis will not occur.
Hypotonic
a solution outside of a cell is called hypotonic if it has a lower concentration of solutes than the inside of the cell. This means water will move in to the cell.
