Topic 3-crossing The Plasma Membrane Flashcards
What is the structure of phospholipids
A hydrophilic (water soluble) tail and a hydrophobic (insoluble) end.
What is the fluid mosaic model and what is its structure?
In the fluid mosaic model there is a double layer of phospholipid molecules (fats) which are arranged with their hydrophobic tails facing inwards and hydrophobic phosphate group facing outwards.
How is the fluid mosaic model significant
This self orienting property allows cellular membranes to reseal themselves when disrupted. The double layer of lipids is quite fluid in which proteins can move quite freely
What are the two components of proteins
INTEGRAL-embedded in the phospholipid bilayer and are described as transmembrane proteins
PERIPHERAL-anchored to the exterior of the plasma membrane by bonding with the lipids or indirectly associated with the plasma membrane through interaction with integral proteins within the membrane.
What is the composition and function of PHOSPHOLIPIDS
COMPOSITION: two fatty acid chains joined to a phosphate containing group
FUNCTION: forms the plasma membrane, controls movement of substances
What is the composition and function of TRANSMEMBRANE PROTEINS
Composition: Protein
Function: receptors to hormones and neurotransmitters
What is the composition and function of TRANSPORTERS CHANNEL AND CARRIER PROTEINS
Composition: protein
Function. Assists substances to be transported in and out of cells
What is the composition and function of GLYCOPROTEINS
Composition. Sugars attached to exposed part of proteins
Function. Cell identity, knows difference between foreign and own cells
What is the composition and function of GLYCOLIPIDS
Composition: carbohydrates attached to lipids
Function. Recognition site for cell to cell interactions, receptors and cell identity
What is the composition and function of CHOLESTEROL
Composition. Cholesterol
Function. Membrane stability, membrane fluidity
What is the function of the plasma membrane
The plasma membrane controls the movement of some dissolved substances into and out of cells. Because it only allows some substances to move in and out, it is selectively permeable.
Through which part of the membrane do substances move?
Water is able to move through the phospholipid bilayer and the protein channels. Even though water is not soluble in phospholipids, it is able to move through the phospholipid layer because it is constantly moving, so it is able to pass between the phospholipid molecules.
What is the difference between solute, solvent and solution
SOLUTE substance that can be dissolved in another
SOLVENT substance in which other substances can be dissolved
SOLUTION solute is a solution dissolved in a solvent
What is the concentration gradient
The difference in solute concentration between two regions
How do molecules move
Collide with one another and the sides of the container due to kinetic energy until they are evenly distributed within the given space. An increase in temperature will increase the motion of particles as they have more kinetic energy and will distribute quicker.
Why is water essential for life
All substances dissolve in and chemical processes of biological significance occur in an aqueous solution
Which properties of water make it useful for metabolic purposes
Water is a polar molecule as the oxygen end is slightly negative and the hydrogen end positive
It’s polar nature gives water versatility as a solvent
Water molecules show cohesion as they stick to each other and are held in place by hydrogen bonds
Water molecules show adhesion as they stick to other polar molecules
What is the definition of hydrophobic
Water fearing, substances that are insoluble in water
What is hydrophilic
Water loving, substances that are soluble in water
What is simple diffusion
The net movement of substances across the phospholipid bilayer from a low to high concentration
What is osmosis
The net movement of water across a semipermeable membrane from a Lo to high solute concentration
What type of transport is diffusion and osmosis
Passive transport. No energy requires for the molecules to move in and out of the cell
Define isotonic and the impact it has on osmosis
Isotonic, having an equal solute concentration to that of the cells. No net movement of water
Define hypotonic and the impact it has on osmosis
Having a lower solute concentration that the cell contents. Water will move into the cell. In plant cells the cell walls protect it from bursting and fill the vacuoles but will burst animal cells
Define hypertonic and the impact it has on osmosis
Having a higher solute concentration than the cell contents. More solute molecules outside the cells, so water will be sucked in that direction. In plant cells the cell loses water and wilts but in animal cells the cell shrinks.
What are the two major components of the plasma membrane?
Phospholipids and proteins
What does turgid mean in relation to plant cells?
If the plant cell is placed in water, water enters via osmosis but the cell does not burst it only swells. This is because the cell wall does not break it only stretches. Eventually the cellulose cannot stretch anymore and so the cell stops swelling. This is the point where the cell become TURGID. Turgidity is important in plants because it helps plants stay firm.
What does flaccid mean in relation to plant cells?
When the plant cell is placed in a hypertonic solution the water moves out of the cell via osmosis and the cell shrinks, losing turgor and becoming flaccid. If the external solution is strong enough plasmolysis occurs and the cytoplasm pulls away from the cell wall.
What is haemolysis and how is it caused?
In a hypotonic solution, water will diffuse into a cell when solute concentration is higher outside the cell. This causes the cell to swell and burst. The rupture of red blood cells is called haemolysis.
How do organisms without cell walls solve the problem of taking in too much water?
Single called organisms such as paramecium live in freshwater environments. They have a problem of taking in too much water. These organisms do not have a cell wall to stop them from bursting however they do have a pair of contractile vacuoles, which actively expel water from the cell absorbed by osmosis from their surroundings.
What is facilitated diffusion?
Facilitated diffusion enables molecules that cannot diffuse across the phospholipid bilayer to move across the plasma membrane through the agency of transporter proteins and is a net movement of molecules from a high to low concentration.
What kind of molecules are unable to diffuse through the phospholipid bilayer?
Water soluble molecules such as ions, amino acids and glucose require transporter proteins to move in and out of cells.
What factors affect the rate of diffusion?
Concentration gradient The distance involved The area involved Barriers to diffusion Temperature Size of molecules
How does concentration gradient affect the rate of diffusion?
Diffusion rates will be higher when there is a greater difference in concentration between two regions.
How does the distance involved affect the rate of diffusion?
Diffusion over short distances occurs at a greater rate than diffusion over larger distances
How does the area involved affect the rate of diffusion?
The larger the area across which diffusion occurs the greater the rate of diffusion
How do barrier to diffusion affect the rate of diffusion?
Thicker barriers slow diffusion rate. Pores in a barrier enhance diffusion
How does temperature affect rate of diffusion?
The higher the temperature the quicker the rate of diffusion because molecules move faster at higher temperatures.
How do the size of molecules affect the rate of diffusion?
At a given temperature, a smaller particle moves faster than a larger one, so smaller particles will diffuse faster than larger ones.
What is the definition of active transport?
Active transport moves dissolved substances from a region of low concentration to a region of high concentration of those substances with and input of energy (atp)
What are some examples of where active transport is used?
Key functions of cells including ph balance, regulation of cell volume and uptake of needed nutrients.
Uptake of dissolved mineral ions from water in the soil by plant root hair cells against their concentration gradient
Production of acidic secretion by stomach cells that have a low internal concentration of hydr
What is bulk transport?
The movement of substances in and out of cells through a process called cytosine involving the folding in or out folding of the plasma membrane. This process requires an input of energy called atp.
What is endocytosis?
The process of bulk transport into a cell achieved by part of the plasma membrane enclosing the material to be transported and then pinching off to form a membrane vehicle which moves out of the cell.
What is the difference between phagocytosis and pinocytosis?
Phagocytosis is a form of endocytosis that involves material that is in a sold form being transported into cells, while pinocytosis involves material that is in a solution.
What is exocytosis?
Bulk transport out of cells. Vesicles formed with a cell fuse with the plasma membrane.
