The Cell Membrane Essay, Research Paper
Homeostasis is essential to the cell s survival. The cell membrane is
responsible for homeostasis. The membrane has a selective permeability
which means what moves in and out of the cell is regulated. Amino
acids, sugars, oxygen, sodium, and potassium are examples of substances
that enter the cell. Waste products and carbon dioxide are removed from
the cell. All of these substances cross the membrane in a variety of
ways. From diffusion and osmosis, to active transport the traffic
through the cell membrane is regulated.
Diffusion is the movement of molecules form one area of higher
concentration to an area of lower concentration. Concentration gradient
causes the molecules to move from higher concentration to a lower
concentration. The side of the membrane that has the higher
concentration is said to have the concentration gradient. It drives
diffusion because substances always move down their concentration
gradient. The pressure gradient also plays a role in diffusion. Where
this is a pressure gradient there is motion of molecules. The pressure
gradient is a difference in pressure between two different points. If
the concentration of one side of the membrane is greater than the
molecules will travel from the higher to lower concentration.
Eventually there will be a dynamic equilibrium and there will be no net
movement of molecules from one side to the other.
Osmosis is the diffusion of water. Like diffusion, the water moves
from a region of higher water potential to a region of lower water
potential. Solutions have three different stages that the solutes can
be classified in: isotonic, hypertonic, and hypotonic. Isotonic is when
the solutions have equal amounts of solutes. Like equilibrium, there is
no net change in the amount of water in either solution. When the
solutions have different concentration of solutes then the one with less
solute is hypotonic and the one with more solute is hypertonic.
Hypotonic takes in the solute from the hypertonic side that gives away
the solute. There will be a net movement in these types of solution.
The molecules will move from the hypotonic solution into the hypertonic
solution.
The third way a substance can cross the cell membrane is through
facilitated diffusion. This occurs when special carrier proteins carry
solutes dissolved in the water across the membrane by using active
transport. When the concentration gradient can not allow travel from
one side of the membrane to the other fast enough for the cell s
nutritional needs, then facilitated diffusion is used. The transport
protein is specialized for the solute it is carrying, just as enzymes
are specialized for their substrate. The transport protein can be
changes or blocked just like enzymes. There are several theories on how
proteins facilitate diffusion. In one case the transport protein acts
like a revolving door. The protein opens on one end and accepts the
solute and then closes. It opens on the other end and releases the
solute. Another way proteins facilitate diffusion is proteins that
extend over the membrane can provide a shuttle that the selective
solutes may cross. There are proteins where their job is to open and
close a gated channel. Polar molecules and ions blocked by the
phospholipid bilayer diffuse through it by facilitated diffusions.
Intercellular joining is when cell s membranes hook together. Cell to
cell recognition and when different parts of the cytoskeleton bond to
proteins, are both ways that substances may cross the membrane through
facilitated diffusion.
Active transport moves the solutes against their concentration
gradients. Proteins use ATP energy to pump certain substances through
the membrane. One way ATP powers active transport is by a
sodium-potassium pump. The pump exchanges sodium for potassium across
the plasma membrane of animal cells. ATP powers it by transferring a
phosphate group to the protein. Large molecules are transported across
the plasma membrane by vesicles, this is called exocytosis. Vesicles,
which form in the Golgi apparatus, are moved by the cytoskeleton to the
plasma membrane. When the plasma membrane and the vesicle membrane
touch the lipid molecules rearrange themselves so that the two membranes
are fused together. The substance inside the vesicle now overflows
outside of the cell. The opposite method, substances moving into the
cell, is called endocytosis. There are three steps involved in
endocytosis. The first step, phagocytosis, takes in macromolecules and
packages hem membrane-enclosed sac. After the sac fuses with enzymes it
is digested. In the next step, called pinocytosis, the cell engulfs the
sac and its dissolves solute. The final step is receptor-mediated
endocytosis, where only specific substances attach to the receptor
sites. Endocytosis brings substances outside the cell into the cell.
Active transport has one final way of transporting substances across the
cell membrane, and that is called phosphorylation. ATP is made up of
three phosphates that can power active transport by transferring one of
its phosphate groups to a protein. When ATP s phosphate group is
hydrolyzed and the phosphate group is transferred we call it
phosphorylation.
In review, substances cross the cell membrane in two different ways:
passive and active transport. Passive transport includes osmosis,
diffusion, and facilitated diffusion. None of these techniques use
energy. Active transport includes endo and exocytosis, sodium-potassium
pumps. and phosphorylation, all of which expend energy to transport
substances across the cell membrane. The cell has the ability to
regulate what crosses its cellular boundaries.
38c
Другие работы по теме:
Smoking Is An Addiction Essay Research Paper
Smoking is an addiction. When a person smokes a tobacco product, they inhale the smoke, which contains nicotine as well as over 500 other chemicals. A cigarette contains cover paper, tobacco, nicotine, filter, and tar.
State Cross Country Meet Essay Research Paper
State Cross Country Meet I can still remember the day I ran at the state Cross Country Meet. It was one of the most exciting days of my life. It took place in Round Rock, Texas during my
The Dream Of The Rood Essay Research
Paper ?Creating a Warrior?: Analyzing The Dream of the Rood The story of Christ’s crucifixion is one of the most important and well known stories of the Bible. It has been told through many different perspectives but none more unique then the one shared in ?The Dream of the Rood?. Told through the view of the cross ?The Dream of the Rood? is based on the story of the crucifixion.
The Importance Of Water In Living Organisms
Essay, Research Paper Water has importance inside cells and externally. This may be because it has interesting chemical and physical properties; it can be found naturally in all three of its states. However its molecules are bonded together by hydrogen bonds, this raises its melting and boiling points, i.e. its boiling point would be -120??C rather than 100??C.
Properties Of Water Essay Research Paper What
Properties Of Water Essay, Research Paper What properties of water make it a unique material and an essential component of living matter? Water is so common that it is easy to overlook the fact that it is an exceptional substance with many amazing qualities. With its properties, we can trace water s unique behavior to the structure and interactions of its molecules.
Sound Nature Essay Research Paper
Very simply, sound is the vibration of any substance. The substance can be air, water, wood, or any other material, and in fact the only place in which sound cannot travel is a vacuum. When these substances vibrate, or rapidly move
Algebra Essay Research Paper Determine and Apply
Algebra Essay, Research Paper Determine and Apply a Formula My topic for this assignment is was to determine the amount of people possible to cross a crosswalk during the time of the crosswalk?s walking symbols. To calculate this I made an algebraic equation to support my idea, and an example to support my equation.
Acids And Bases Essay Research Paper What
Acids And Bases Essay, Research Paper What substances turned into Acids? & What substances turned into Bases? Hypothesis: Procedure: Pour about three milliliters of your sample in each of three test
Chemical Properties Essay Research Paper Mixtures and
Chemical Properties Essay, Research Paper Mixtures and pure substances - Pure substances are matter made up of only one type of atom or molecule - Mixtures are a collection of 2 or more pure substances physically mixed
Element Essay Research Paper What is an
Element Essay, Research Paper What is an element: Simple substances that can not be broken down into simpler substances. What is an atom: smallest part of an element that can be identified as an element.
The War On Drugs Essay Research Paper
War On Drugs In today?s society, the war on drugs has become a major issue in our cities and the business community. Many cities have started programs to make the situation better, but some have failed and the situation has become worse. The root of all the problems discussed in this case study, can be linked to drugs.
The History Of The Atom Essay Research
Paper THE HISTORY OF THE ATOM I am doing my project on the history of the atom. The atom was not just thought up overnight it took thousands of years of research and experimenting, but was finally finalized bty Dalton. Dalton was curious about many things but most of all he wondered how substances combined. He discovered that if you combine two substance, you got a new completely different substance.
Spinoza Essay Research Paper This paper will
Spinoza Essay, Research Paper This paper will outline Spinoza s argument in Part 1 of his Ethics of substance. He argues that there is only one substance, which is the same as God, that includes everything in the universe. It will walk through each proposition and explain his proof of it, which relies of his stated definitions.
Archeo Essay Research Paper A Cross Cultural
Archeo Essay, Research Paper A Cross Cultural Perspective of Polygyny As an institution, polygyny, the social arrangement that permits a man to have more than one wife at the same
Freudian Defense Mechanisms Essay Research Paper All
Freudian Defense Mechanisms Essay, Research Paper All people use defense mechanisms, whether they be consciously or unconsciously. Anxiety may arise from an intense situation or even past experience. It is then the ego’s job to displace anxiety so as to protect the rest of the mind. Through defense mechanisms such as sublimation, repression, fantasy, compulsive fun-seeking, and negativism, the ego eliminates anxiety caused by surroundings which in effect tries to prevent insanity.
St Patrick
’s Cross Essay, Research Paper History and Symbolism of the Celtic Cross There are many variations of the legends about the Celtic Cross. In modern times the ringed cross is sometimes a symbol of faith or to show ones Irish, Scottish or Welsh identity. An Irish Catholic priest might tell you that the circle on a Celtic Cross is a symbol of eternity that represents the unending love that God showed through Jesus’ crucifixion.
The Membrane Essay Research Paper The MembraneThe
The Membrane Essay, Research Paper The Membrane The membrane has a double lipid layer through which fat- soluble substances will move, by passive transport or diffusion. The molecules will only move through if they are small enough.
Lava Lamp Paper how To Make Essay
, Research Paper Things you can use to make a Lava Lamp. There are many things you can use to make a Lava Lamp. Aside from wax and water, there are many other substances that you can use to make the lamp work in the same fashion. For example, you can use mineral oil as the lava and 90% isopropyl alcohol mixed with 70% isopropyl alcohol (rubbing alcohol) as the liquid inside the lamp.
PlatoS Forms Examining The View Essay Research
Paper I. Introduction Purpose I intend to show the validity of Plato’s arguments about his theory of Forms. Aristotle, along with others, cross-examines Plato’s proposals. Yet, I happen to see the potential of his point of view and would like to take a deeper look into his theory. The purpose of this paper is to critically analyze the theory of Plato’s Forms from his perspective and that of several others, including Aristotle.
Drugs And Alcohol Essay Research Paper Drugs
Drugs And Alcohol Essay, Research Paper Drugs and Alcohol In today’s college experience both drugs and alcohol are factors in a students everyday life. Although drinking under the age of twenty-one and the use of non-prescription drugs are illegal they are still prevalent. Both substances are easily accessible to today’s college students.
Cell Permeability Essay Research Paper Cell membrane
Cell Permeability Essay, Research Paper Cell membrane permeability refer to the crossing of the cell membrane by substances. Substances move into or out of the cell by crossing the cell membrane. Some substances cross the membrane very easily and the membrane is said to be very permeable to these substances; others move across with difficulty, while others are excluded completely.
Constantine Essay Research Paper November 9 1998Brandon
Constantine Essay, Research Paper November 9, 1998 Brandon McGarrell Constantine and Sigma Chi The design of the white cross that symbolizes Sigma Chi is patterned after the Christian cross that Emperor Constantine had envisioned the night before he attacked Rome in the battle at Melvin Bridge. Maxentius, the leader of the Roman army had died a few days earlier due to poor construction of a bridge while on retreat.
How Temperature Can Affect The Rate Of
Reaction Essay, Research Paper The Problem: I am going to find out how temperature can affect the rate of reaction. Background information: Factors that change the rates of reactions are:
Sodium Thiosulphate And Hydrochloric Acid Essay Research
Paper I am measuring the rate of reaction (how fast a reaction takes) of sodium thiosulphate and hydrochloric acid. There are different variables I could use to see the change in the rate of reaction. These include temperature, concentration or catalysts. I am going to do two experiments, one changing the temperature and one changing the concentration of the sodium thiosulphate.
Crosscultural Communication Barriers Essay Research Paper Thesis
Cross-cultural Communication Barriers Essay, Research Paper Thesis: A number of different factors contribute to cross-cultural communication barriers. This thesis will be proven through the examination of Canada?s past history, current policies and future plans concerning immigration and assimilation of immigrants into Canadian society.
In The Life Of A Modern Man
Born In The Renaissance Essay, Research Paper Have you ever pondered the birth of your hobbies? Or have you ever wondered who invented the mechanisms you use in your everyday life? Well, modern art, today’s religion, and the present printing press had to originate some point in time. And what could be a better time then during the Renaissance and the Reformation? These three points were a major part of those years.
The Things They Carried Possessions Of Character
Essay, Research Paper The Things They Carried: Possessions of Character “The Things They Carried,” by Tim O’Brien, contains many references to “possessions of character.” Many things Lt. Cross carries were carried by all,
The Things They Carried
– Tim O’biran Essay, Research Paper Tim O?Brien?s ?The Things They Carried? is a tale that deals not only with the physical risk of war, but also with the emotional effects it has on the young soldiers. Lt. Jimmy Cross is the designated leader. He has been placed in a position of authority and great responsibility.
Kkk And The Cross In Cincinnati Essay
, Research Paper The KKK and the Cross The KKK are only putting the cross up in Fountain Square because they want attention. Do we want to give them what they want? NO! So, we can all not pay any attention to the cross. Instead of criticizing it, we worship it. It?s like whenever a little kid is doing something really annoying and you keep telling them to stop, but they don?t because they just want attention.