Transport across cell membranes Flashcards
Channel Proteins in the cell membrane does what?
- Helps molecules be transported through the membrane by Facilitated Diffusion
Why is the cell-surface membrane described as a fluid-mosaic?
- the phospholipid molecules in the bilayer are constantly moving about giving a fluid structure
- the protein molecules are unevenly distributed throughout the membrane forming a mosaic
How are phospholipids arranged in a membrane?
- hydrophilic heads of phospholipids oriented either inwards towards the cytoplasm or outwards towards the watery extra-cellular fluid
- hydrophobic tails are oriented towards each other away from water.
What passes through a membrane during simple diffusion?
-very small molecules e.g, carbon dioxide and oxygen
What does a phospholipid bilayer prevent from going through?
- water soluble ions and polar molecules
Intrinsic and Extrinsic Protein
intrinsic - spans the whole membrane
extrinsic - doesn’t span the whole membrane
Cholesterol in the cell membrane does what?
- provides strength and regulates fluidity of fatty acid chain
What is facilitated diffusion
- Diffusion of molecules down a concentration gradient aided by Carrier and Channel Proteins
Rate of Diffusion equation (Fick’s Law)
Surface Area x Concentration Difference/Diffusion Distance
Carrier Proteins in the cell membrane does what?
- Helps molecules be transported through the membrane by facilitated Diffusion and active Transport
How do carrier proteins work?
- the carrier protein has a complementary shape to the polar molecule being transported
- they bind which causes the carrier protein to change shape and transport molecules across the membrane
What is diffusion?
- the net movement of molecules from a high concentration to a low concentration until the molecules are equally distributed
Glycoproteins and Glycolipids Function
involved in cell to cell recognition and able to act as receptors
Factors that decrease Active Transport
- Lowering of temperature
- Lack of Oxygen
- Metabolic and Respiratory Inhibitors
What is Osmosis?
Diffusion of water through a selectively permeable membrane
What is Water Potential?
The potential tendency of water molecules to leave a solution by osmosis
What is Active Transport?
- the movement of ions or molecules against the conc gradient through carrier proteins, requiring ATP
What factors increase Rate of Diffusion?
Increased Surface Area
Increased Concentration Difference
Decreased Diffusion Distance
What happens to red blood cells in a isotonic solution?
- the solution has the same water potential as the cell so there is no net movement of water.
Cell turgor during osmosis?
- as water enters the cell, the vacuole enlarges and the vacuole, cytoplasm and cell membrane exert an outward turgor pressure on the cell wall
What happens to red blood cells in a hypertonic solution?
- the cell has a higher water potential than the solution so water moves out of the cell and into the solution which makes the cell shrivel and become flaccid.
What happens to red blood cells in a hypotonic solution?
- the cell has a lower water potential than the solution and so water moves into the cell which causes swelling and eventually bursting of the cell
What is an epithelial cell?
cells in the body specialised for the absorption or transport of important molecules
Intestine Epithelial cell adaptations? (2)
- folded cell surface membrane into microvilli to increase surface area
- numerous mitochondria to provide ATP for the release of energy. (active transport)
