Chapter 5: Membrane Structure and Function Flashcards
What is the plasma membrane?
the barrier of all living cells and exhibits selective permability due to the fact that it allows some substances to move easily across while keeping other out.
What are aquaporins?
one type of membrane protein that allows for water to pass through a membrane (many more than would pass through on their own)
What are lipids?
and proteins are the main ingredients of membranes, carbohydrates also make up part of the membrane
WHat does amphipathic mean?
hydrophobic and hydrophillic
What does the fluid mosaic model explain?
the liquid nature of the membrane with proteins embedded in it
How thick is the plasma membrane?
to layers thick, hence its name
What is the membrane also known as?
a mosaic due to its variety and number of components
What is a glycoprotein’s function?
cell recognition
What are oligosaccharides’ function?
tags for membrane, markers
What are glycolipids’ used for?
cell recognition
What is the extracellular matrix’s function?
hold some peripheral proteins- support
What is the cytoskeleton’s function?
give sturcutre to the cell, helps to facilitate movement
What is the integral proteins’ function?
transport molecules into & out of cells
What is peripheral proteins’ functions?
act as enzyme to carry out chem RXNs
What is cholesterol’s function?
maintains liquid nature of the cell membrane
Is it possible for phospholipids to move easily within the cell membrane? Explain.
Phospholipids are held together (to other phospholipids) primarily by hydrophobic interactions, wichh are much weaker than covalent bonds (they move through the membrane like party goers moivng through a room)
Explain what occured with Larry Frye and Michael Edidin’s experiment and what it showed.
THey labeled the proteins of a mouse and human cell and then saw how they mixed (moved) across the membrane over one hour.
WHat would you conclude about the proteins if, in a similar experiment, the proteins did not move at all?
You would assume that they are connected to the cytoskeleton of the cell
What are the reasosn that a membrane remains fluid at low temperatures?
Unsaturated fatty acids in plant cells, and cholesterol molecules in animal cells
What do fish that live in cold enviroments have?
a high proportion of unsaturated fatty acids in their phospholipids allowing their membranes to remain fluid at low tems
Plants that are able to tolerate extreme cold will have:
higher percentage of unsaturated phospholipids in the winter, and low percentage of unsaturated phospholipids in the summer
What are integral proteins?
proteins that extend all the way or partially through the cell membrane (the majority are transmembrane proteints)
What are peripheral proteins?
proteins that lie completely outside the bilayre
What are functions of the membrane protein?
transport, enzymatic activity, signal transduction, cell to cell recognition, intercellular joining (tight junction, gap junction), attach to cytoskeleton and ECM
What do glycoproteins and glycolipids help to identify?
cells, e.x. cell recognition, sorting of cells into embryonic tissues, identifying foriegn cells
How are transmemrane glycoproteins oriented in the ER?
carb portion facing into the ER for modification
How are transmembrane glycoproteins oriented in the Golgi apparatus?
carb portion facing into the GOlgi for modification
Breifly explain how transmembrane glycoproteins are oriented in the transport vesicle?
carb portion facing into the vesicle
Explain how the transmembrane glycoproteins are oriented in the plasma membrane?
carb portion facing out of the cell
What is selective permability?
DUe to the fact that molecules do not indiscriminately cross the cell membrane results in selective permeability. The cell is able to allow some small molecules to pass through while excluding molecules
What molecules can pass easily through the plasma membrane?
Small, nonpolar molecules
What cells do NOT pass easily through the plasma membrane?
Polar and large molecules, who require a protein channel
What do transport proetins do?
carry hydrophillic molecules across the plasma membrane, speeding up the movement of two molecules
WHat are the two types of transport proteins?
channel proteins and carrier proteins
What is a carrier proteins?
a protein specific to a certain (group) molecule and hold on to their passengers translocating them across the membrane (protein denaturing for a reason)
WHate does kintetic energy result win?
the random movement of molecules from an area of HIGH concentration to an area of LOW concentration, a process called diffussion
WHen are solutions said to be in equillibrium?
when two solutions are seperated by a permeable membrane and both have equal concentrations of the solute
What is the concentration gradeint?
the difference in concentration between two areas
What factors influence the rate of diffusion?
temperature, concentration gradient, movement, charge
WHat is passive transport?
the diffusion of a substance across a biological membrane because the cell does not have to expend energy to make it happen
What is osmosis?
the movement of water across a membrane. The will occur from HIGH to LOW concentration. Therefore this is considered a form of passive tranport.
What is an isotonic solutions?
when there is no concentration gradient – solute on both sides of the membrane are EQUAL. A cell that is placed in this type of solution will remain the same size
What is a hypertonic soluton?
when there is a higher concentration of solute particles in the enviroment than in the cell. Cells in this type of enviroment will shrink and become flaccid. THis process is called plasmolysis
What is a hypotonic solution?
when there is a lower concentration of solute particles in the enviroment than in the cell
Cells in this type of enviroment will swel and become turgid
What is the contractile Vacuole?
the structure in Paramecium that allows them to release water before it causes them to lose. THis is a form of osmoregulation
What is turgor pressure?
the pressure in plants as the cell membrane presses against the cell wall allowing a plant to stay rigid
What is plasmolysis?
a lack of turgor pressure resulting in a plant wilting
WHat is facilitated diffusion?
the process by which polar molecules and ions move across the plasma membrane, these molecules move through transport proteins
In facilitated diffusion, do molecules go up their concentraiton or down their concentration?
down their concentration
Is facilitated diffusion active or passive transport?
passive
What does a channel protein allow?
the flow of molecules across the membrane
What are aquaporins?
channel proteins that are water carriers
What are ion channels?
channel proteins which function as gated channels which open or close in response to a stimulus
What are carrier proteins?
proteins that undergo a subtle change in shape to translocate a molecule across a membrane
What is active transport?
the transport of molecules against the concentration gradient using Cellular NRG (ATP) (LOW to HIGH concentration)
What is membrane potential?
is the difference in voltage across a membrane created by the difference in ions on either side of the membrane
What is electrochemical gradient?
the difference in charge and concentration of ions that cause them to move across a membrane. Both of these factors drive the diffusion of ions
What is the electrogenic pump?
a protein that creates an electorchemical gradient
What are two examples of the electrogenic pump?
the sodium-potassium pump in animals, and the proton pump in plants, bacteria, and fungi
What can a solute that exists in diffrent concentrations do?
work as it moves
What is cotransports?
when one protein pump facilitates the movement of a different molecule through a different pump
What is exocytosis?
a form of active transport (bulk transport) when large molecules are expelled from the cell
What is endocytosis?
a form of active transport (bulk transport) in which molecules are taken in to the cell
What is phagocytosis?
solid materials are taken in to the cell throguh food vacuoles
What is pinocytosis?
when liquid materials are taken into the cell
What do receptor mediated endocytosis trigger?
the infolding of the membrane and the intake of specific materials
