1.
Some plasma membranes contain channel proteins that help transport specific molecules, such as ions, across the membrane. Which of the following transport processes allow these channel proteins to function without energy expenditure?

active transport
facilitated diffusion
osmosis
diffusion

Question

1. 	
Some plasma membranes contain channel proteins that help transport specific molecules, such as ions, across the membrane. Which of the following transport processes allow these channel proteins to function without energy expenditure?
 	
	active transport
	facilitated diffusion
	osmosis
	diffusion

phagey · Answer

2. 	The plasma membrane is responsible for which set of functions listed below?
 	
	cellular transport, protection, recognition of cellular messages
	replication of DNA, production of enzymes, control of cell division
	production of proteins, cellular respiration, break down of food molecules
	production of ATP molecules, control of cell division, synthesis of proteins
3. 	Why is the phospholipid bilayer only partially permeable to water?
 	
	Water is repelled by the polar tails of the phospholipid.
	Water is repelled by the hydrophobic tails of the phospholipid.
	Water is repelled by the polar head of the phospholipid.
	Water is repelled by the hydrophobic head of the phospholipid.

phagey · Answer

@Kikuo  @wilsondanielle help please

phagey · Answer

@Kikuo

kikuo · Answer

Active transport is the act of using protein pumps to transport a solute against its concentration gradient. 

Osmosis is the diffusion of water from a lower solute concentration to a higher solute concentration through a semipermeable membrane. Osmosis is a type of facilitated diffusion. It requires a channel protein to transport across a semipermeable membrane because a membranes internal structure is made of the the tails of a lipid which are composed of fatty acids opposed to their hydrophilic heads composed of glycerol that are exposed to the external environment. 

I just wanted to make it clear that osmosis is a type of facilitated diffusion. 

Facilitated diffusion is a type of diffusion that uses channel proteins without the use of ATP. It uses channel proteins--proteins that form a tube-like tunnel for proteins--instead of protein pumps which pump solutes against their concentration gradient. Solutes moved by facilitated diffusion travel from their concentration gradient down their concentration gradient through the channel. Carrier proteins are also used in facilitated diffusion which take solutes from their concentration gradient, change shape as they transport them to other side, and release them. 

Aquaporins are channel proteins used to transport water. 
Channel proteins and carrier proteins are a part of facilitated diffusion. 
Therefore, osmosis is a type of facilitated diffusion. 

As for what the plasma membrane is responsible for, I'll list a few things to help you limit your choices. 

Only ribosomes make proteins, and the only place ribosomes are located other than the cytoplasm is on the rough ER. 

An enzyme is a protein. DNA in the nucleus is used as a template to form a code for RNA polymerase to construct a strand of mRNA containing the copied code. 

What makes proteins? Ribosomes! Therefore, this message then goes into the cytoplasm out through the nuclear pores to the ribosome somposed of two subunits to translate this code to form a polypeptide chain (protein). 

DNA helicase, ligase, DNA polymerase 1 and 3, primase, and SSD are responsible for DNA replication. 

Interphase is the stage responsible for cell division, and that simply means the cell gains new organalles, proteins, molecules, and has its DNA replicated before cell division. 

Chemiosmosis is the big procedure that produces a lot of ATP molecules, and that's controlled by a protein called ATP synthase. 

The plasma membrane protects the inside by controlling what is allowed to come in and out. Therefore, we can deduce it must be involved in cellular transport, and as a membrane, we can also assume its job it protect what's inside. 

Now, think of this. How does a plasma membrane grow? It gets a lot of proteins from the golgi apparatus. There must be a way for it to recognize it right? 

So, based off of what I said, can you guess which one is correct? 

For the last question, think about what I've taught you so far. 

Remember when I said the fatty acid portion of a lipid is hydrophobic and the glycerol head is hydrophilic? 

Now, think of the word SEMI-permeable. Can you put the two together? 

Tell me if you have any trouble!

phagey · Answer

can you explain it easier for me please because all that you said really confused me @Kikuo  im sorry

kikuo · Answer

Sure! Facilitated diffusion -uses channel proteins that span the membrane -uses carrier proteins that take in solutes, change shape, and then release them to the other side -this is done without energy or ATP -this is a type of diffusion therefore it moves solutes from where they're more concentrated to where they're least concentrated visual representation http://prntscr.com/am4dbx -diffusion is movement of solutes from areas where they're most at to where they're least at Active transport -a type of transport that's not diffusion since it moves solutes against their concentration gradient: meaning they move solutes to where they're least concentrated to where they're more concentrated -use ATP or energy -uses protein pumps instead of protein channels or carrier visual representation http://prntscr.com/am4egs -arrow indicates movement of solutes from least concentrated region to more concentrated region Osmosis -diffusion of water from a place that's more hypotonic or contains less solutes and more water to an area that's hypertonic or contains more solutes and less water -requires a channel protein therefore being a type of facilitated diffusion -requires channel protein because a biological membrane is made up of a phospholipid bilayer meaning that the outside of the membrane is hydrophilic (composed of a head or more specifically a glycerol molecule that is polar) while the inside is composed of the glycerol's fatty acid chain or tails that are hydrophobic and therefore repel water while hydrophilic head allows water to pass -due to this a channel is needed for water to be transported into the cell -this protein is called an aquaproin visual representation http://prntscr.com/am4gmh As far as the plasma membrane goes let me make this more clear to you -ribosomes are organelles INSIDE the cell that the PLASMA MEMBRANE encloses that makes proteins -therefore the plasma membrane has no function in making proteins -since enzymes are proteins we can also conclude the plasma membrane has nothing to do with the composition of enzymes -cellular respiration is the act of breaking down glucose molecules to produce energy and this happens in an organelle meaning its enclosed by the plasma membrane serving as a specialized structure inside the cell called mitochondria -therefore the plasma membrane has nothing to do with cellular respiration or breaking down molecules since that's what cellular respiration does -the process of producing a lot of ATP molecules is done with a protein that spans the membrane called ATP synthase -therefore the plasma membrane has nothing to do with making ATP molecules -interphase is responsible for preparing a cell for cell division -therefore the plasma membrane has nothing to do with cell division since interphase is a stage

kikuo · Answer

-replication of DNA is controlled by ligase, DNA polymerase 1 and 3, primase, SSD, and DNA helicase all of which aren't related to the plasma membrane 
-the plasma membrane controls what goes into and out of the cell therefore serving as a protective guide for the structures inside the cell and also playing a part in membrane transport 
-since the plasma membrane needs to grow it also must be able to recognize those signals from inside the cell to help it grow

kikuo · Answer

As for why the phospholipid bilayer is only semi-permeable to water, the inside of a membrane--what it is made of internally--is made up of a hydrophobic fatty acid that repels water. The outside of a membrane is made up of a glycerol molecule and there is hydrophilic, so it allows water to pass. 

The membrane as a whole is considered the phospholipid bilayer. 

It's composed of a hydrophobic part and a hydrophilic part. 

So, it's only partially permeable to water. 

That should be enough for you to solve your problems!

kikuo · Answer

visual representation of phospholipid bilayer http://prntscr.com/am4ma3

fatir5 · Answer

You have an idea about what diffusion is. If there are some carrier molecules which (facilitate) help diffuse certain substances inside a cell, such type of diffusion is facilitated diffusion. No energy expenditure here.

In 2nd one, you are asking about functions of plasma membrane. See it's an outer membrane that holds all the contents of cell. So whatever gets inside the cell or come out, has to pass through this membrane. So can you tell me now if it's function is transportation or not? what will be the 1st thing a signal will encounter when it is getting inside the cell or communicate with it? Lastly it holds the whole contents of the cell, so is it involved in shaping a cell or not? I hope you got your answer.

fatir5 · Answer

As for the last one, phospholipid molecule has a polar hydrophilic head and a non polar hydrophobic tail. See there is a water repellant here ie hydrophobic tail, which makes it semi-permeable.

phagey · Answer

ok, so is 1. diffusion 2. cellular transport 3. Water is repelled by the hydrophobic tails of the phospholipid?  @fatir5  @Kikuo

phagey · Answer

ok can yall help me with 3 more? @fatir5  @Kikuo

kikuo · Answer

Yes.

fatir5 · Answer

Medal for this one? @phagey