Chapter 5 Flashcards
Plasma Membranes
Describe what is meant by the “fluid mosaic” model of the cell membrane.
The plasma membrane is a mosaic of components. These components give the membrane its fluid character
What are the four main components of a plasma membrane?
Phospholipids cholesterol proteins and carbohydrates
Amphiphilic
molecule has parts that are hydrophobic and parts that are hydrophilic integral proteins are integrated into the membrane structure
selective permeability
certain substances are able to pass into or out of the cell while other ones are not
concentration gradient
things move from an area of a high concentration to areas of a lower concentration of the same substance
diffusion
passive random movement of a substance from an area of higher concentration to an area of lower concentration
osmosis
the diffusion of water across the semi permeable membrane
equilibrium
reached after the concentration gradient lessons over a period of time until the concentration is equal on both sides
Aquaporins
special channel proteins that allow water to pass through the membrane at a very high rate
Tonicity
the ability of an extracellular solution to influence the osmosis and therefore the volume of a cell
Electrochemical gradient
a difference of electrical charge across the plasma membrane will also influence the diffusion of molecules
Endocytosis
a type of active transport that moves large substances into a cell
Exocytosis
the active process of moving large substances out of a cell
Which molecular structures on the phospholipid are responsible for giving it the hydrophobic and hydrophilic nature.
The head is hydrophilic and the tail is hydrophobic
Is the membrane-spanning region of an integral protein hydrophobic or hydrophilic?
It is hydrophobic because it is interacting with the hydrophobic region of the phospholipid bilayer
How do peripheral proteins differ from integral proteins?
Peripheral proteins are only found on the surface of the membrane either internally or externally whereas integral proteins span across the entire surface throughout
Describe the conditions under which carbohydrates are associated with the plasma membrane.
Carbohydrates are only present on the exterior surface where they can attach to proteins to form glycoproteins or carbohydrates can attach to lipids to form glycolipids
What is the glycocalyx and why is it important to cells?
The glycocalyx includes glycoproteins and glycolipids it is highly hydrophilic and it helps to bring in substances to where they come into contact with this cell
What is the function of the cholesterol found incorporated into the plasma membrane of animal cells?
The cholesterol extends the range of temperatures at which the membrane can maintain a functional fluidity
Name several types of molecules that would likely be able to cross the plasma membrane. Name several types of molecules that would likely not.
Lipid soluble and other nonpolar molecules such as fat soluble vitamins, lipid based drugs, fat soluble hormones, oxygen, and carbon dioxide would be able to pass through whereas polar substances such as ions, simple sugars, and amino acids would not be able to
What are the three types of transport we discussed in lecture and how are they different? How are they the same?
There is passive transport active transport and bulk transport passive transport does not require the cell to spend any energy active transport requires a cell to use energy often in the form of ATP and bulk transport is used when cells need to take in or remove larger molecules and particles that cannot pass through the membrane
Which specific types of transport require energy and which do not?
Diffusion osmosis and facilitated diffusion do not require energy whereas active transport it does require energy
Be able to discuss the factors that influence the rate of diffusion for a particular substance.
Some of the factors are the extent of the concentration gradient, the mass of the molecule, temperature, density of the median, solubility, surface area and thickness of the membrane, distance traveled, electrical charge, and pressure/filtration
Understand how integral transmembrane proteins function as the two types of transport proteins in facilitated diffusion.
Channel proteins are integral transmembrane proteins which allow passage of a specific material into or out of a cell
Carrier proteins are integral transmembrane proteins that bind to a substance to allow it to pass into or out of a cell
Know which parts of a channel protein are hydrophobic and which are hydrophilic and why.
The hydrophilic portion is exposed to the intercellular and extracellular fluids and the hydrophilic portion is the channel
Be able to apply the concepts of hypo-, hyper-, and isotonic solutions in terms of which way the water would move across the semi-permeable membrane.
If a cell is in a hypotonic solution it will swell with water moving in, if it is in a hypertonic solution it will shrink with water moving out, and if it is an isotonic solution the water will be moving in and out equally and the cell will not change shape
What is the main energy form that active transport uses?
ATP
Be familiar with the sodium-potassium pump and how it works.
The sodium potassium pump is an antiporter that uses ATP to move three sodium into the cell and two potassium out of the cell across the cell membrane
What is the difference between the uniporter, symporter, and antiporter transport protein pumps?
Uniporter pumps carry one specific ion or molecule, symporter pumps carry two different ions or molecules in the same direction, and antiporter pumps carried 2 different ions or molecules in different directions
Given an example, be able to label transport as either primary or secondary active transport.
Primary active transport is solely dependent on ATP, while secondary active transport moves materials across the cell membrane due to the electrochemical gradient and commonly has a molecule that is attached such as hydrogen being transported with glucose
How is bulk transport different from other forms of active transport?
Bulk transport is used when cells need to take in or remove larger molecules and particles that cannot pass through the membrane
What are the three types of endocytosis we discussed?
Phagocytosis is the taking in of a large particle or cell, pinocytosis is the taking in of a small volume of extracellular fluid, and receptor mediated endocytosis is where receptor proteins in the plasma membrane allow for targeted endocytosis of a single specific type of substance
