CELL MEMBRANES AND TRANSPORT Flashcards
what are the four components that make a cell membrane?
lipids, cholesterol, proteins and carbohydrates
what are the functions of a cell membrane?
controls what enters and exits the cell
keeps cell components inside the cell
acts as a sit for biochemical reactions
what is the structure of a phospholipid?
made up of a phosphate group and two fatty acid chains: hydrophilic head and hydrophobic tail
what molecules can pass through the phospholipid bilayer?
small, non polar molecules
what is the structure of a cholesterol molecule?
hydrophilic head and hydrophobic tail
what is the role of cholesterol in the cell membrane?
it fits between phospholipid molecules and regulates the fluidity of the membrane and keeps it stable
what are the two types of proteins found in the cell membrane?
integral (intrinsic) and peripheral (extrinsic)
what are the roles of proteins in the cell membrane?
transport proteins move substances that are unable to pass through the phospholipid bilayer such as ions
peripheral proteins act as receptors for cell recognition
act as antigens for cell to cell recognition and signalling
what do carbohydrates for on the cell membrane?
glycoproteins when they attach to a protein
glycolipids when they attach to a lipid
what are the roles of glycoproteins and glycolipids?
some act as receptors
used for cell recognition and cell signalling
what is meant by the fluid mosaic model?
the term fluid relates to the phospholipids in the membrane constantly moving. the term mosaic describes the top view of the cell wall as a mosaic from the scattered proteins, cholesterol, phospholipids and carbs
how thick in the cell wall?
7nm
how does temperature affect the cell membrane’s fluidity?
when temperature increases, fluidity increases
when temperature decreases, fluidity decreases
when temperature increases, cholesterol will pull the phospholipids together, which decreases the fluidity
when temperature decreases, cholesterol will push the phospholipids making more spaces between them, which increases the fluidity
what is diffusion?
the net movement of particles from a region of high concentration to a region of low concentration down a concentration gradient
what type of process is diffusion and why?
passive as it doesn’t need energy
how does temperature affect the rate of diffusion?
as temperature rises particles gain more kinetic energy and move faster causing diffusion to take place faster
how does surface area affect the rate of diffusion?
the more surface area of the membrane the more diffusion can occur
how does the concentration gradient affect the rate of diffusion?
the steeper the concentration gradient the faster the net movement of diffusion
what is facilitated diffusion?
the passive diffusion of large polar molecules across the membrane through a protein channel
what is active transport?
the movement of molecules across the cell membrane against the concentration gradient using ATP
what proteins does active transport use?
carrier protein
what is endocytosis?
engulfing of materials by the plasma membrane. this includes phagocytosis and pinocytosis
what is exocytosis?
the transport of materials out of the cell by the fusion of vesicles with the cell membrane
what is osmosis?
the net movement of water molecules from an area of high water potential to an area of low water potential through a partially permeable membrane
what does hypotonic mean?
when there is more water potential outside the cell than inside the cell so the net movement of water goes inside the cell
plant cells are turgid and animal cells are lysed
what does isotonic mean?
when there is an equal amount of water potential inside and outside the cell and the net movement is the same
plant cells are flaccid and animal cells are normal
what does hypertonic mean?
when there is more water potential inside the cell than outside the cell so the net movement of water goes outside the cell
plant cells are plasmolyzed and animal cells are shriveled
