Biological Membranes 2.5 Flashcards
Name the roles of the membrane
The membrane seperates the internal and external environments so that reactions can occur without interference.
The membrane also allows for cell to cell signalling to take place as there are glycoprotiens that contain antigens so any foreign bodies can be detected if the wrong antibodies are displayed.
allows the passage of certain moleules in and out of the cell this maybe with the use of the enzyme pathways.
what model is used to describe the structure of the membrane and what molecules does it contain write an answer like a 6 marker and compare
The membrane is described as a fluid mosaic model as the membrane has many randomly placed molecules such as glycoproteins and pathways for molecules to travel through. The bi layer consists of 2 layers of phospholipids. There are protein channels, carrier and peripheral proteins . The cholesterol is used to regulate the fluidity. If the membrane is to fluid it will allow the passage or unwanted organelles in and out of the cell. If it is too rigid the cell will not be able to travel around the body and perform its tasks.
What is meant by the term simple diffusion and what are examples of molecules that can make use of it in the membrane
This the movement of substances from a area of high conc to an area of low conc. Lipids can pass through due to the membrane being made of lipids and steroid hormones thathave been made from fats as fats comprise one of the components of the phospholipid
What affects the rate of diffusion. with added detail write down answers before looking
The temperature affects the rate as if the temp increases there will be more gaps in the membrane for the molecules to pass through.
If the diffusion distance is too thick diffusion will stop or be very slow.
The surface area of places for the molecules to diffuse through the larger the cell the more surface area it has for molecules to diffuse through.
the size of the diffusing molecule
conc gradient
What is meant by the term facilitated diffusion
This is with the use of channel and carrier proteins as it is the movement of ions and bigger molecules. the carrier proteins that are used are specific to the purpose and therefore do not require atp
How does the body transport molecules against the conc grad
This is with the use of active transport and ATP. There is a use for carrier proteins that are activated with the use of ATP. The ATP is used to change the confirmation shape.
how does the body transport large molecules through the cells.
Bulk transport is used to transport the molecules by pinching off, separation and fusion with the use of vesicles that require ATP to produce.
Moving large quantities of material out of the cell is called….
Exdocytosis, this process takes place at the end of protein synthesis. The vesicle fuses with the cell surface membrane forcing the material out of the cell
Moving large quantities of material into the cell is called….
Endocytosis, this is used in phagocytosis when the phagocyte is engulfing a pathogen that is then digested and broke apart with the help of lysosomes
How does temperature affect both structure and permeability
If the temperature is below or on 0 degrees the membrane is rigid and can be punctured by ice crystals. Cholesterol does try to buffer the effects by preventing the compacting lipids. At normal temperatures the fluidity is maintained and membranes partial permeability remains constant. As the temp rises the proteins in the membrane begin to denature as well as the high kinetic energy forces the phospholipds to vibrate causing gaps and increasing permeability.
What is the practical example used to show this..
Beetroot sample is used to see how temperature affects the membrane as there is a pigment in the vacuole called betalain that when released shows a red colour so the more the membrane begins to denature the more the pigment is shown.
The movement of water from high conc to low conc across a partially permeable membrane is known as…
osmosis
What is the measure of conc of water based upon the free water molecules that can diffuse
Water Potential trident as notation
What are the three types of solution caused by osmosis and what are their characteristics
Hypotonic - this is when there is too much water in the cell and the cell becomes lysed and implodes. However in plant cells the cell only becomes turgid due to the cellulose cell wall.
Isotonic - solution is the normal movement and is steady for animal cells but for plant cells this is the flaccid state
Hypertonic - this is when there is a higher salt conc outside of the cell which leads to all water leaving the cell. this will lead to the animal cell becoming crenated and the plant cell becoming plasmolysed.
