Skip to main content

Which part of the cell membrane is responsible for transportation?

The cell membrane is made of a phospholipid bilayer that acts as a barrier to what molecules can or cannot enter the cell. There are different structures within the cell membrane to move molecules too large to enter between the phospholipids and those that are polar. Diffusion and osmosis are natural processes that do not require energy from the cell. Since no energy is required by the cell, diffusion and osmosis are types of passive...

The cell membrane is made of a phospholipid bilayer that acts as a barrier to what molecules can or cannot enter the cell. There are different structures within the cell membrane to move molecules too large to enter between the phospholipids and those that are polar. Diffusion and osmosis are natural processes that do not require energy from the cell. Since no energy is required by the cell, diffusion and osmosis are types of passive transport. Diffusion allows non-polar molecules to flow from an area of higher concentration to an area of lower concentration. Osmosis is a specific type of diffusion involving only water molecules. Some molecules will need the aid of a channel protein to pass through the membrane. When the channel protein is open, the molecules will pass though by diffusion. This is still a form of passive transport because it requires no energy. If a molecule is too large to pass through the membrane by diffusion, transport proteins are needed. Carrier proteins mediate active transport. Active transport requires energy expenditure by the cell to get a molecule into or out of the cell. This is because the molecule needs to work against the gradient, meaning it must go from a lower concentration to a higher concentration.

Comments

Post a Comment

Popular posts from this blog

What is the meaning of "juggling fiends" in Macbeth?

Macbeth is beginning to realize that the three witches have been deceiving him since he first encountered them. Like jugglers, they have kept changing their forecasts in order create confusion. This is particularly apparent when the Second Apparition they raise in Act IV,   Scene 1 tells him that no man of woman born can overcome him in hand-to-hand battle--and then Macbeth finds himself confronted by the one man he has been avoiding out of a... Macbeth is beginning to realize that the three witches have been deceiving him since he first encountered them. Like jugglers, they have kept changing their forecasts in order create confusion. This is particularly apparent when the Second Apparition they raise in Act IV,   Scene 1 tells him that no man of woman born can overcome him in hand-to-hand battle--and then Macbeth finds himself confronted by the one man he has been avoiding out of a sense of guilt, and that man tells him: Despair thy charm. And let the angel whom thou still hast serve...
Post a Comment
Read more

What are some external and internal conflicts that Montag has in Fahrenheit 451?

 Montag, the protagonist of Fahrenheit 451, faces both external and internal conflicts throughout the novel. Some examples of these conflicts are: External Conflicts: Conflict with the society: Montag lives in a society that prohibits books and critical thinking. He faces opposition from the government and the people who enforce this law. Montag struggles to come to terms with the fact that his society is based on censorship and control. Conflict with his wife: Montag's wife, Mildred, is completely absorbed in the shallow and meaningless entertainment provided by the government. Montag's growing dissatisfaction with his marriage adds to his external conflict. Conflict with the fire captain: Montag's superior, Captain Beatty, is the personification of the oppressive regime that Montag is fighting against. Montag's struggle against Beatty represents his external conflict with the government. Internal Conflicts: Conflict with his own beliefs: Montag, at the beginning of th...
Post a Comment
Read more

In A People's History of the United States, why does Howard Zinn feel that Wilson made a flimsy argument for entering World War I?

"War is the health of the state," the radical writer Randolph Bourne said, in the midst of the First World War. Indeed, as the nations of Europe went to war in 1914, the governments flourished, patriotism bloomed, class struggle was stilled, and young men died in frightful numbers on the battlefields-often for a hundred yards of land, a line of trenches. -- Chapter 14, Page 350, A People's History of the United States Howard Zinn outlines his arguments for why World War I was fought in the opening paragraph of Chapter 14 (referenced above). The nationalism that was created by the Great War benefited the elite political and financial leadership of the various countries involved. Socialism, which was gaining momentum in Europe, as was class struggle, took a backseat to mobilizing for war. Zinn believes that World War I was fought for the gain of the industrial capitalists of Europe in a competition for capital and resources. He states that humanity itself was punished by t...
Post a Comment
Read more