transport between cell membrane Flashcards
(28 cards)
what is the cell’s requirements
continual supply of things they need and continual removal of things they produce.
require homeostasis, body systems work together to make sure environment is kept constant
needs certain substances from extracellular fluid. once these substances are processed, it needs to be removed from the cell into the extracellular fluid
all cells need oxygen and glucose for respiration that releases energy in the form of app adenosine triphosphate fro the cell’s activities.
waste like co2 and h20 needs o be released into the tissue fluid.
many cells produce produce elsewhere in the body like enzymes and hormones - must be released into extracellular fluid.
cell’s immediate environment is the extracellular fluid.
even cells that are very close together have. thin layer of tissue fluid
for a substance to get in or out of the cell, it needs o Gert through t eh cell membrane
homeostasis?
the maintenance of a relatively constant internal cellular environment
what is the structure of the cell membrane
made of 2 phospholipid molecules - known as a bilayer
(phospholipid bilayer). phospholipid is a lipid molecule made of a containing a phosphate group. bilayer is 2 layers that make up a singleton’s membrane.
Each phospholipid molecule has a tail that is hydrophobic (water hating) and a head that is hydrophilic (water loving)
embedded in the phospholipid bilayer is cholesterols that are wedged between the phospholipids and protein molecules
lipid
Large organic molecules made of fatty acids and glycerol.
what is the currently accept3ed model for the cell membrane and why?
fluid mosaic mode
lthe membrane is said to be fluid because the molecules in which it is made are constantly changing position.
It is said to be mosaic because it is made of many different types of molecules.
In science, a model is a simple explanation for a complex idea.
what are the protein membranes int eh cell membrane?
Only 2% of molecules in membrane are proteins but they make up 55% of weight of membrane Receptor proteins Channel Proteins Carrier proteins Identity makers proteins
what are the functions of the cell membrane?
- Physical Barrier - membrane separates the cell cytoplasm from the extracellular fluid (tissue fluid). Isolation between the cytoplasm and the extracellular fluid is important because they both have very different compositions.
- Regulation of passage of materials - membrane controls the passage of materials into and out of the cell. Eg the passage of ions, nutrients, removal of wastes, release of secretions channel proteins.
- Sensitivity - cell membrane is the first part of the cell affected by any changes in the extracellular fluid. It has protein receptors that are sensitive to particular molecules in its tissue fluid.
- Support - the internal part of the cell membrane is attached to microfilaments of cell’s cytoskeleton, hence giving support to the whole cell. There are connections between membranes of adjacent cells that give support to the whole tissue of which cells are a part of.
what type of membrane is the cell membrane
differentially permeable membrane meaning they allow certain ions and molecules to pass through but restrict the movement of others. (semipermeable or selectively)
Differentially permeable - a membrane that permits the passage of certain substances ions, small molecules, but restricts the passage of large molecules as it contains many tiny pores. Water passes through easily but sugar, starch, proteins are not able to pass through easily.
what is a passive process?
the cell’s energy that comes from respiration is not used. No energy or input is required and occurs from low to high concentration solute and high to low solvent concentration.
follows the diffusion gradient
what is an active process?
energy and input is required from respiration. Does not follow net diffusion as it can occur from high to low concentration solute and low to high concentration solvent. Requires expenditure of energy.
what is diffusion
passive process resulting from the random movement of ions and molecules from high concentration solute to a low concentration solute and (low to high concentration solvent).
Liquid and gas particles spread out over the available space.
Small molecules make their way through channel proteins to the other side of membrane like water and ions (Na, K, Ca) uncharged molecules such as CO2 and O2 and fat soluble molecules like alcohols, lipids, steroids and soluble drugs to pass freely through the phospholipid bilayer. (Fat soluble passes easily through lipid portions of bilayer). O2 diffuses into cell because it is continually used up inside the cell.
There will be always some molecules moving against the concentration gradient as the movement of molecules when diffusing is random.
concentration gradient
Concentration gradient is the difference in concentration of solvents and solute in a solution that brings about diffusion, inside and outside of a cell membrane.
diffusion gradient
Net diffusion is the movement of liquid or gas molecules from places of high to low concentrations along a diffusion gradient.
what can be solvents
Only liquid and gas particles are the solvents as the particles in these mediums are constantly moving.
how does diffusion occur
When molecules are diffusing, they move in random directions and in straight lines until they hit another molecule, obstacle or wall of cell membrane. A deflected molecule then continues in a straight line until it hits anther molecule or obstacle. Molecules moving away from a high concentrated area does fewer collisions than when moving to an area of low concentrations areas. When moving to areas of less concentrations, they will therefore stay on their straight paths longer and move out into areas which are less concentrated of molecules. Through this, the molecules become evenly distributed.
what happens when sugar and water molecules diffuse?
When sugar molecules are diffusing in a beaker of water, the water molecules are also diffusing. If passive process means that it goes from high to low concentration solute, at the same time, it is going from low to high concentration solvent (in the opposite direction) This is because there is a lower concentration of water in the sugar cube than the concentration of water elsewhere in the beaker. It needs to diffuse against the concentration gradient of the sugar cubes, therefore, there is also a diffusion gradient in the solvent (water), but in the opposite direction of that of the solute (sugar cube).
what is osmosis
Osmosis is the diffusion of water molecules through a differentially permeable membrane from an area of higher concentration of water to an area of lower water concentration (concentration gradient still going down passive). The concentration of solvent depends on how much solute has dissolved in the water.
what is osmotic pressure
pressure due to differences of concentrations of a solvent (water) on either side of a differentially permeable membrane. The higher the concentration of solute, the higher the osmotic pressure. More water is needed to be transferred from one side of membrane to the other is there is more solute that is required to be dissolved in. There will be more water on one side than on the other side.
what is carrier mediated transport
Carrier mediated transport is the transport of large molecules, such as sugar, starch and proteins through carrier proteins that can be active or passive.
Carrier mediated transport is a passive (going with net diffusion) or active transport (going against net diffusion) depending on the exact nature of mechanism.
transport of large molecules. Requires carrier proteins in membrane to transport large molecules such as sugar, starch and protein across cell membrane. (glucose, amino acids) and certain ions when active.
The molecule attaches to the binding site of the carrier protein. The protein changes shape and releases the molecule on the other side of the membrane.
what are the characteristics of carrier proteins in carrier?
- Carrier proteins only bind to a specific molecule. Some proteins may only bind to a glucose molecule, but not a sucrose molecule.
- Carrier proteins can become saturated. Once all career proteins are occupied, any increase int e concentration of molecules to be transported, cannot increase the rate of movement.
- Carrier activity is regulated by hormones
what are 2 types of carrier mediated transport?
facilitated diffusion and active transport
what is facilitated diffusion?
Facilitated diffusion is a passive process in which the diffusion of large molecules such as glucose and amino acids occur. Substances move with the concentration gradient. The molecule attaches to the binding site of carrier protein. The protein changes shape and releases the molecule on the other side of the membrane.
what is a passive process in carrier med transport?
Active transport requires energy from the cell as it moves against the concentration gradient (from lower to higher concentration solute and high to low concentration solvent). Carrier proteins can take certain ions, glucose and amino acids in and out of the cell membrane regardless of their concentrations in and outside cytoplasm.
vesicular transport
Vesicular transport is an active transport in which materials are transported through vesicles, from high to low concentration solute and low to high concentration solvent. Goes against concentration gradient.
The active transportation of liquids or solids into and out of cytoplasm through vesicles.
Vesicle is a small membrane bound cavity in the cytoplasm of a cell smaller than a vacuole.
It is an active transport as energy from the cell is required to make the vesicles.
