## 1. Introduction

Membranes are selectively permeable. This means that membranes allow the cell to “select” what can pass through the membrane. This, in turn, allows the cell to determine what can enter or leave the cell, and what can’t.

In what follows, we’ll look at a few ways that things make their way across the cell membrane.

## 2. Diffusion

Diffusion is the tendency of molecules to spread out from where they’re more concentrated to where they’re less concentrated.

• Put a drop of ink into a cup of water. Over time, you’ll see the ink slowly spread out until it’s uniformly distributed throughout the cup. That’s diffusion.

• A fragrance (or bad odor) released in one part of a room spreads throughout the entire room. That’s diffusion.

A key idea related to diffusion is the idea of a concentration gradient. A gradient is a slope. In the same way that a ball will roll down a slope, molecules in a fluid will move down a concentration gradient, spreading out from higher concentration to lower concentration. So when you think of diffusion, just imagine that the diffusing molecules are flowing down a slope, moving from where they’re more concentrated (on the left side of this diagram) to less concentrated (on the right side). The -ΔG indicates that this process is spontaneous. You don’t have to add any outside energy to this system to make diffusion happen (and we’ll learn more about spontaneity in an upcoming module).

Both simple diffusion and facilitated diffusion are forms of passive transport. In passive transport:

• The cell doesn’t have to expend any energy to make these processes happen.
• The energy is in the kinetic energy of the molecules themselves.

You can see diffusion down a concentration gradient in the animation on the right: the molecules, represented by cubes, are flowing down their concentration gradient as they diffuse from where they’re in higher concentration (below the membrane) to where they’re in lower concentration (above the membrane)

In cells, diffusion can be of two types: simple diffusion or facilitated diffusion.

Facilitated diffusion is diffusion through a protein channel. Ions and polar molecules pass through membranes in this way. These channels are specific. For example, a channel that lets a sodium ion through won’t let a potassium ion through.

 Simple Diffusion Facilitated diffusion Simple diffusion is when a molecule diffuses right through the phospholipid bilayer. Non-polar molecules (such as steroid hormones) can do this. So can gases like carbon dioxide and oxygen. Facilitated diffusion is diffusion through a protein channel. Ions and polar molecules pass through membranes in this way. These channels are specific. For example, a channel that lets a sodium ion through won’t let a potassium ion through.

## 3. Active Transport

Cells, at times, need to move substances from lower concentration to higher concentration. Unlike diffusion, which occurs spontaneously, this requires the cell to expend energy as it pumps materials up a concentration gradient.

This type of energy-requiring movement of materials from lower to higher concentration is called active transport.

In diagrams like this one, look for two clues that tell you that it’s about active transport. First of all, follow the arrow. If the molecules are moving from where there are very few of them to where there are a lot of them, it’s active transport. Also, if you see “ATP” going into a pump or protein channel, you know that the cell is expending its energy (in the form of ATP) to do the work of pumping molecules up a concentration gradient.

## 4. Endocytosis

In endocytosis, the membrane pinches in. This creates a pocket that surrounds material outside the membrane. Like active transport, this requires cell energy.

There are three types of endocytosis:

 Pinocytosis Phagocytosis Receptor-Mediated Endocytosis In pinocytosis, the membrane pinches in (1). The pinching in continues (2) until a vesicle forms (3), surrounding some of the extracellular fluid and whatever was inside it. Think of pinocytosis as the cell taking a small “sip” of the material outside the membrane. During phagocytosis, the cell uses its membrane to surround a particle (or even another cell). The membrane pinches in (1)  to form a vesicle that enters the cytoplasm (2). Phagocytosis is used by white blood cells in the immune response to swallow invaders. Single-celled organisms like amoebas use phagocytosis to eat. In receptor-mediated endocytosis, a piece of the membrane pinches in response to some molecule that binds with a receptor embedded in the membrane. Images from www.boundless.com. Used under Creative Commons 4.0 license

## 5. Exocytosis

Exocytosis is the opposite of endocytosis. A vesicle filled with a molecule that the cell needs to release (1) fuses with the cell membrane (2). As the membrane of the vesicle fuses with the membrane of the cell, the vesicle’s contents are released into the fluid outside the cell.

Exocytosis is how cells, such as B cells (a type of white blood cell), export the proteins they’ve manufactured. For more detail about the cellular machinery involved, take a look at our tutorial on the endomembrane system.

## 6. Membrane Transport Flashcards

[qdeck random = “true;” style=”width: 528px; border: 2px solid black; ” qrecord_id=”sciencemusicvideosMeister1961-Membrane Transport Flashcards (M8)”]

[h] Flashcards: Cell Membrane Transport

[i] If you haven’t used a set of flashcards on Learn-Biology.com before, here’s what you need to know.

• If you know it, click ‘Got it.”
• If you don’t know it as well as you’d like, click ‘Need more practice,’ and that card will go to the bottom of the deck so you can practice it again.
• ‘Shuffle’ lets you shuffle the deck.

[!] Card 1+++++++++++++++++++++++++++++++++++[/!]

[q]The boundary that surrounds the cytoplasm of the cell is the ______ ______________

[textentry]

[a]The boundary that surrounds the cytoplasm of the cell is the cell membrane.

[!] Card 2+++++++++++++++++++++++++++++++++++[/!]

[q]Membranes allow certain molecules to pass through but not others. In other words, membranes are ________-_______________.

[textentry]

[a] Membranes allow certain molecules to pass through but not others. In other words, membranes are selectively-permeable. (note that semi-permeable means just about the same thing).

[!] Card 3+++++++++++++++++++++[/!]

[q]_____________ is the movement of molecules from where they’re more concentrated to where they’re less concentrated.

[textentry]

[a]Diffusion is the movement of molecules from where they’re more concentrated to where they’re less concentrated.

[!] Card 4+++++++++++++++++++++[/!]

[q]One way to talk about diffusion is to say the molecules in a fluid will move down a _____________ ____________.

[textentry]

[a]One way to talk about diffusion is to say the molecules in a fluid will move down a concentration gradient.

[!] Card 5+++++++++++++++++++++[/!]

[q]When substances diffuse directly through a membrane’s phospholipid bilayer, the process is called _____________ ____________.

[textentry]

[a]When substances diffuse directly through a membrane’s phospholipid bilayer, the process is called simple diffusion.

[!] Card 6+++++++++++++++++++++[/!]

[q]When substances diffuse into a cell by passing through a protein channel, the process is called _____________ ____________.

[textentry]

[a]When substances diffuse into a cell by passing through a protein channel, the process is called facilitated diffusion.

[!] Card 7+++++++++++++++++++++[/!]

[q]When cells expend energy to move a substance from lower concentration to higher concentration, this process is known as _____________ ____________.

[textentry]

[a]When cells expend energy to move a substance from lower concentration to higher concentration, this process is known as active transport.

[!] Card 8+++++++++++++++++++++[/!]

[q]A vesicle filled with some substance fuses with the membrane, releasing that substance outside the cell. This process is called ____________.

[textentry]

[a]A vesicle filled with some substance fuses with the membrane, releasing that substance outside the cell. This process is called exocytosis.

[!] Card 9+++++++++++++++++++++[/!]

[q]The cell membrane pinches in, taking in something outside of the cell and enclosing it within a vesicle. This process is called ____________.

[textentry]

[a]The cell membrane pinches in, taking in something outside of the cell and enclosing it within a vesicle. This process is called endocytosis.

[!] Card 10+++++++++++++++++++++[/!]

[q]The kind of endocytosis in which a small portion of the membrane pinches in, allowing the cell to “take a sip” of the fluid outside of the cell, is called _________

[textentry]

[a]The kind of endocytosis in which a small portion of the membrane pinches in, allowing the cell to “take a sip” of the fluid outside of the cell, is called pinocytosis.

[!] Card 11+++++++++++++++++++++[/!]

[q]The kind of endocytosis in which a large portion of the membrane surrounds a food particle (or even another cell), and then brings that particle into the cell is called _________

[textentry]

[a]The kind of endocytosis in which a large portion of the membrane surrounds a food particle (or even another cell), and then brings that particle into the cell is called phagocytosis.

[!] Card 12+++++++++++++++++++++[/!]

[q]The kind of endocytosis in which the membrane only pinches in when a molecule outside the cell binds with a receptor molecule in the membrane is called ____________.

[textentry]

[a]The kind of endocytosis in which the membrane only pinches in when a molecule outside the cell binds with a receptor molecule in the membrane is called receptor-mediated endocytosis.

[!] Card 13+++++++++++++++++++++[/!]

[q]The best name for the process shown in this diagram is [textentry]

[a]The best name for the process shown in this diagram is diffusion.

[!] Card 14+++++++++++++++++++++[/!]

[q]The best name for the process shown in this diagram is [textentry]

[a]The best name for the process shown in this diagram is simple diffusion.

[!] Card 15+++++++++++++++++++++[/!]

[q]The best name for the process shown in this diagram is [textentry]

[a]The best name for the process shown in this diagram is facilitated diffusion.

[!] Card 16+++++++++++++++++++++[/!]

[q]The best name for the process shown in this diagram is [textentry]

[a]The best name for the process shown in this diagram is active transport.

[!] Card 17+++++++++++++++++++++[/!]

[q]The best name for the process shown in this diagram is [textentry]

[a]The best name for the process shown in this diagram is exocytosis.

[!] Card 18+++++++++++++++++++++[/!]

[q]The best name for the process shown at “A,” “B,” and “C” in this diagram is [textentry]

[a]The best name for the process shown in this diagram is endocytosis.

[!] Card 19+++++++++++++++++++++[/!]

[q]The specific type of endocytosis shown in this diagram is [textentry]

[a]The specific type of endocytosis shown in this diagram is pinocytosis.

[!] Card 20+++++++++++++++++++++[/!]

[q]The specific type of endocytosis shown in this diagram is [textentry]

[a]The specific type of endocytosis shown in this diagram is phagocytosis

[!] Card 21+++++++++++++++++++++[/!]

[q]The specific type of endocytosis shown in this diagram is [textentry]

[a]The specific type of endocytosis shown in this diagram is receptor-mediated endocytosis

[x]

[restart]
[/qdeck]

## 7. Quiz: Cell Membrane Transport

[qwiz random = “true;” style = “border: 3px solid black; ” qrecord_id=”sciencemusicvideosMeister1961-Membrane Transport Quiz (M8)”]

[h] Quiz: Cell Membrane Transport
[i]This activity tests your understanding of membranes and transport. Here’s how the quiz works:

• Each question is multiple-choice, but the entire quiz is like a series of flashcards.
• If you get the question right, it comes off the deck.
• If you get the question wrong, it goes to the bottom of the deck, so you can try it again.

[q labels = “top”]

[l]lower concentration

[fx] No, that’s not correct.  Please try again.

[f*] Excellent!

[l]higher concentration

[fx] No, that’s not correct.  Please try again.

[f*] Correct!

[q labels = “top”]

[l]ink molecules in high concentration

[f*] Excellent!

[fx] No, that’s not correct.  Please try again.

[f*] Great!

[q labels = “top”]

 _____________________ ___________________ _____________________

[l]simple diffusion

[fx] No, that’s not correct.  Please try again.

[f*] Great!

[l]active transport

[fx] No, that’s not correct.  Please try again.

[f*] Excellent!

[l]facilitated diffusion

[f*] Great!

[q labels = “top”]

[l]active transport

[f*] Great!

[l]simple diffusion

[fx] No, that’s not correct.  Please try again.

[f*] Correct!

[l]facilitated diffusion

[f*] Excellent!

[q labels = “top”]

 ____________________________ _________________________

[l]exocytosis

[f*] Good!

[l]endocytosis

[f*] Great!

[q labels = “top”]

[l]pinocytosis

[fx] No, that’s not correct.  Please try again.

[f*] Great!

[l]phagocytosis

[f*] Great!

[l]receptor-mediated endocytosis

[f*] Good!

[q labels = “top”]

[l]molecules released from the cell

[fx] No, that’s not correct.  Please try again.

[f*] Excellent!

[l]vesicle

[f*] Great!

[l]molecules inside the vesicle

[fx] No, that’s not correct.  Please try again.

[f*] Great!

[q] When a cube of sugar is placed in a beaker of water, sugar molecules spread through the beaker by

[c]ZW5kb2N5dG9zaXM=[Qq]

[c]ZGlmZn VzaW9u[Qq]

[c]ZmFjaWxpdGF0ZWQgZGlmZnVzaW9u[Qq]

[c]YWN0aXZlIHRyYW5zcG9ydA==[Qq]

[f]Tm8uIEVuZG9jeXRvc2lzIGludm9sdmVzIGEgbWVtYnJhbmUgcGluY2hpbmcgaW4gdG8gYnJpbmcgb3V0c2lkZSBtYXRlcmlhbCBpbnNpZGUgdGhlIGNlbGwuIFRoZSBzcHJlYWRpbmcgb3V0IG9mIHRoZXNlIHN1Z2FyIG1vbGVjdWxlcyBpcyBhbiBleGFtcGxlIG9mIHN1YnN0YW5jZXMgbW92aW5nIGZyb20gaGlnaGVyIGNvbmNlbnRyYXRpb24gdG8gbG93ZXIgY29uY2VudHJhdGlvbi4gV2hhdCYjODIxNztzIHRoYXQga2luZCBvZiBtb3ZlbWVudCBjYWxsZWQ/[Qq]

[f]RXhjZWxsZW50LiBUaGlzIGlzIGFuIGV4YW1wbGUgb2YgZGlmZnVzaW9uLg==[Qq]

[f]Tm8uwqBGYWNpbGl0YXRlZCBkaWZmdXNpb24gaW52b2x2ZXMgbW9sZWN1bGVzIG1vdmluZyBhY3Jvc3MgYSBtZW1icmFuZSB0aHJvdWdoIGEgcHJvdGVpbiBjaGFubmVsLiBEcm9wIHRoZSAmIzgyMjA7ZmFjaWxpdGF0ZWQmIzgyMjE7IHBhcnQsIGFuZCB5b3UmIzgyMTc7bGwgaGF2ZSB0aGUgYW5zd2VyLg==[Qq]

[f]Tm8uIEFjdGl2ZSB0cmFuc3BvcnQgaW52b2x2ZXMgY2VsbHMgdXNpbmcgZW5lcmd5IHRvIHB1bXAgbWF0ZXJpYWxzIGZyb20gbG93ZXIgdG8gaGlnaGVyIGNvbmNlbnRyYXRpb24uIFRoZSBzcHJlYWRpbmcgb3V0IG9mIHRoZXNlIHN1Z2FyIG1vbGVjdWxlcyBpcyBhbiBleGFtcGxlIG9mIHN1YnN0YW5jZXMgbW92aW5nIGZyb20gaGlnaGVyIGNvbmNlbnRyYXRpb24gdG8gbG93ZXIgY29uY2VudHJhdGlvbi4gV2hhdCYjODIxNztzIHRoYXQga2luZCBvZiBtb3ZlbWVudCBjYWxsZWQ/

Cg==

[Qq]

[q] Diffusion is a term for the movement of molecules from

[c]IGFuIGFyZWEgb2YgbG93IGNvbmNlbnRyYXRpb24gdG8gYW4gYXJlYSBvZiBoaWdoIGNvbmNlbnRyYXRpb24u[Qq]

[c]IG91dHNpZGUgb2YgdGhlIGNlbGwgdG8gaW5zaWRlIHRoZSBjZWxs[Qq]

[c]IGFuIGFyZWEgb2YgaGlnaCBjb25jZW50cmF0aW9uIH RvIGFuIGFyZWEgb2YgbG93IGNvbmNlbnRyYXRpb24u[Qq]

[c]IGEgbnVjbGV1cyB0byB0aGUgbWl0b2Nob25kcmlhLg==[Qq]

[f]Tm8uIExvb2sgYXQgdGhpcyBkaWFncmFtLCBhbmQgc2VlIGlmIHlvdSBjYW4gY29tZSB1cCB3aXRoIHRoZSByaWdodCBleHBsYW5hdGlvbi4=

Cg==

[f]Tm90IG5lY2Vzc2FyaWx5LiBEaWZmdXNpb24gbWlnaHQgbW92ZSBtYXRlcmlhbHMgaW50byBhIGNlbGwsIGJ1dCBpdCBjYW4gYWxzbyBtb3ZlIG1hdGVyaWFscyBvdXQgb2YgYSBjZWxsLiBMb29rIGF0IHRoaXMgaW1hZ2UgYW5kIHNlZSBpZiB5b3UgY2FuIGZpZ3VyZSBvdXQgdGhlIHJpZ2h0IGFuc3dlci4=

Cg==

[f]RXhhY3RseS4gRGlmZnVzaW9uIGlzIHRoZSBtb3ZlbWVudCBvZiBhIHN1YnN0YW5jZSBmcm9tIGhpZ2ggdG8gbG93IGNvbmNlbnRyYXRpb24u[Qq]

[f]Tm8uIERpZmZ1c2lvbiBpcyBub3QgYWJvdXQgbW92aW5nIGZyb20gb25lIHNwZWNpZmljIHBsYWNlIHRvIGFub3RoZXIuIEl0JiM4MjE3O3MgbXVjaCBtb3JlIGdlbmVyYWwuIExvb2sgYXQgdGhpcyBpbWFnZSBhbmQgc2VlIGlmIHlvdSBjYW4gZmlndXJlIG91dCB0aGUgcmlnaHQgYW5zd2VyLg==

Cg==

[q] Diffusion is about the random movement of

[c]IGNlbGxz[Qq]

[c]IG9yZ2FuaXNtcw==[Qq]

[c]IGNlbGwgbWVtYnJhbmVz[Qq]

[c]IG1vbGVj dWxlcw==[Qq]

[f]Tm8uIERpZmZ1c2lvbiBpcyBhYm91dCByYW5kb20gbW92ZW1lbnQgb24gYSB2ZXJ5IHNtYWxsIGxldmVsLiBOZXh0IHRpbWUsIGNob29zZSBhIGxldmVsIG11Y2ggc21hbGxlciB0aGFuIGNlbGxzLg==[Qq]

[f]Tm8uIERpZmZ1c2lvbiBpcyBhYm91dCByYW5kb20gbW92ZW1lbnQgb24gYSB2ZXJ5IHNtYWxsIGxldmVsLiBOZXh0IHRpbWUsIGNob29zZSBhIGxldmVsIG11Y2ggc21hbGxlciB0aGFuIG9yZ2FuaXNtcy4=[Qq]

[f]Tm8uIERpZmZ1c2lvbiBpcyBhYm91dCByYW5kb20gbW92ZW1lbnQgb24gYSB2ZXJ5IHNtYWxsIGxldmVsLiBOZXh0IHRpbWUsIGNob29zZSBhIGxldmVsIG11Y2ggc21hbGxlciB0aGFuIGV2ZW4gYSBjZWxsIG1lbWJyYW5lLg==[Qq]

[f]WWVzLiBEaWZmdXNpb24gaXMgYWJvdXQgdGhlIHJhbmRvbSBtb3ZlbWVudCBvZiBtb2xlY3VsZXMu

Cg==

[Qq]

[q] For diffusion to occur, there must be:

[c]IGEgbWVtYnJhbmU=[Qq]

[c]IGEgZ3Jh ZGllbnQ=[Qq]

[c]IHdhdGVy[Qq]

[c]IEFUUA==[Qq]

[f]Tm8uIERpZmZ1c2lvbiBkb2VzIG5vdCByZXF1aXJlIGEgbWVtYnJhbmUuIEl0IGNhbiBvY2N1ciBpbiBhIGN1cCBvZiB3YXRlciBvciBhIHJvb20uIEluIHRlcm1zIG9mIHRoZSBtb2xlY3VsZXMgdGhhdCBhcmUgZGlmZnVzaW5nLCB3aGF0IGRvZXMgZGlmZnVzaW9uIHJlcXVpcmU/[Qq]

[f]WWVzLiBEaWZmdXNpb24gcmVxdWlyZXMgYSBncmFkaWVudCYjODIxMTthIGRpZmZlcmVuY2UgaW4gY29uY2VudHJhdGlvbiBsZXZlbHMu[Qq]

[f]Tm8uIERpZmZ1c2lvbiBjYW4gb2NjdXIgaW4gd2F0ZXIsIGFuZCB3YXRlciBjYW4gZGlmZnVzZSwgYnV0IHdhdGVyIGlzIG5vdCA=cmVxdWlyZWQ=IGZvciBkaWZmdXNpb24uwqBJbiB0ZXJtcyBvZiB0aGUgbW9sZWN1bGVzIHRoYXQgYXJlIGRpZmZ1c2luZywgd2hhdCBkb2VzIGRpZmZ1c2lvbiByZXF1aXJlPw==[Qq]

[f]Tm8uIEFUUCBpcyB0aGUgY2VsbCYjODIxNztzIGltbWVkaWF0ZSBlbmVyZ3kgc291cmNlLCBhbmQgY2VsbCBlbmVyZ3kgaXMgbm90IHJlcXVpcmVkIGZvciBkaWZmdXNpb24uIEluIHRlcm1zIG9mIHRoaXMgcXVlc3Rpb24sIHdoYXQgZG9lcw==IGRpZmZ1c2lvbiByZXF1aXJlPw==

Cg==

[Qq]

[q] Cell membrane channels are made of

[c]IHBob3NwaG9saXBpZHMu[Qq]

[c]IGNhcmJvaHlkcmF0ZXMu[Qq]

[c]IEROQS4=[Qq]

[c]IFJOQS4=[Qq]

[c]IHByb3Rl aW5zLg==[Qq]

[f]Tm8uIFBob3NwaG9saXBpZHMgbWFrZSB1cCB0aGUgYmlsYXllciwgd2hpY2ggaXMgdGhlIGtleSBzdHJ1Y3R1cmFsIHBhcnQgb2YgdGhlIG1lbWJyYW5lLiBUaGUgY2hhbm5lbHMgYXJlIG1hZGUgb2Ygc29tZXRoaW5nIGVsc2Uu[Qq]

[f]Tm8uIENhcmJvaHlkcmF0ZXMgYXJlIHBvc2l0aW9uZWQgb24gdGhlIG91dGVyIHN1cmZhY2Ugb2YgdGhlIG1lbWJyYW5lLCBwcm92aWRpbmcgZm9yIGNlbGwgcmVjb2duaXRpb24uIFRoZSBjaGFubmVscyBhcmUgbWFkZSBvZiBzb21ldGhpbmcgZWxzZS4=[Qq]

[f]Tm8uIEROQSBpcyBub3QgcGFydCBvZiB0aGUgbWVtYnJhbmUuIFdoYXQgY291bGQgdGhlc2UgY2hhbm5lbHMgYmUgbWFkZSBvZj8=[Qq]

[f]Tm8uIFJOQSBpcyBub3QgcGFydCBvZiB0aGUgbWVtYnJhbmUuIFdoYXQgY291bGQgdGhlc2UgY2hhbm5lbHMgYmUgbWFkZSBvZj8=[Qq]

[f]RXhjZWxsZW50ISBNZW1icmFuZSBjaGFubmVscyBhcmUgbWFkZSBvZiBwcm90ZWlu

Cg==

[Qq]

[q] The cell membrane lets only some things in and out. The best way to describe that is to say that the membrane is

[c]IHNlbWktcG VybWVhYmxl[Qq]

[c]IGltcGVuZXRyYWJsZS4=[Qq]

[c]IHBlcm1lYWJsZQ==[Qq]

[c]IGltcGVybWVhYmxl[Qq]

[f]IFRoYXTigJlzIHJpZ2h0LiBNZW1icmFuZXMgbGV0IG1hdGVyaWFscyBwYXNzIGluIGFuZCBvdXQgb2YgdGhlIGNlbGwsIGJ1dCB0aGV5IGRvIHNvIGluIGEgdmVyeSBzZWxlY3RpdmUgd2F5LiBUaGlzIG1ha2VzIHRoZSBtZW1icmFuZSBzZW1pLXBlcm1lYWJsZS4gTm90ZSB0aGF0ICYjODIyMDtzZWxlY3RpdmVseSBwZXJtZWFibGUmIzgyMjE7IG1lYW5zIGp1c3QgYWJvdXQgdGhlIHNhbWUgdGhpbmcu[Qq]

[f]IE5vLiDigJhJbXBlbmV0cmFibGXigJkgbWVhbnMgdGhhdCBub3RoaW5nIGNhbiBwYXNzIHRocm91Z2guIElmIG1lbWJyYW5lcyB3ZXJlIGltcGVuZXRyYWJsZSwgdGhleSB3b3VsZG7igJl0IGJlIGFibGUgdG8gbGV0IGZvb2QgYW5kIG5lZWRlZCBzdWJzdGFuY2VzIGludG8gdGhlIGNlbGwsIGFuZCBsZXQgd2FzdGVzIG91dC4gTmV4dCB0aW1lLCBzZWxlY3QgYSBjaG9pY2UgdGhhdCByZWZsZWN0cyB0aGUgbWVtYnJhbmXigJlzIGFiaWxpdHkgdG8gc2VsZWN0IHdoYXQgc3Vic3RhbmNlcyB3aWxsIGVudGVyIHRoZSBjZWxsLCBhbmQgd2hhdCBzdWJzdGFuY2VzIHdpbGwgbGVhdmUu[Qq]

[f]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[Qq]

[f]IE5vLiAmIzgyMjA7SW1wZXJtZWFibGUmIzgyMjE7IG1lYW5zIHRoYXQgbm90aGluZyBjYW4gcGFzcyB0aHJvdWdoLiBJZiBtZW1icmFuZXMgd2VyZSBpbXBlcm1lYWJsZSwgdGhleSB3b3VsZG7igJl0IGJlIGFibGUgdG8gbGV0IGZvb2QgYW5kIG5lZWRlZCBzdWJzdGFuY2VzIGludG8gdGhlIGNlbGwsIGFuZCBsZXQgd2FzdGVzIG91dC4gTmV4dCB0aW1lLCBzZWxlY3QgYSBjaG9pY2UgdGhhdCByZWZsZWN0cyB0aGUgbWVtYnJhbmXigJlzIGFiaWxpdHkgdG8gc2VsZWN0IHdoYXQgc3Vic3RhbmNlcyB3aWxsIGVudGVyIHRoZSBjZWxsLCBhbmQgd2hhdCBzdWJzdGFuY2VzIHdpbGwgbGVhdmUu

Cg==

[Qq]

[q]When molecules diffuse, they flow

[c]dXAgdGhlaXIgY29uY2VudHJhdGlvbiBncmFkaWVudA==[Qq]

[c]ZG93biB0aGVpciBjb25jZW 50cmF0aW9uIGdyYWRpZW50[Qq]

[f]Tm8uIEZsb3dpbmcgdXAgYSBjb25jZW50cmF0aW9uIGdyYWRpZW50IGlzIHdoYXQgaGFwcGVucyBpbiBhY3RpdmUgdHJhbnNwb3J0Lg==[Qq]

[f]WWVzLiBEdXJpbmcgZGlmZnVzaW9uLCBtb2xlY3VsZXMgZmxvdyBkb3duIHRoZWlyIGNvbmNlbnRyYXRpb24gZ3JhZGllbnQu

Cg==

[Qq]

[q] True or false: In active transport, a cell uses the kinetic energy in molecules and lets them flow down their concentration gradient.

[c]IFRSVUU=[Qq]

[c]IEZB TFNF[Qq]

[f]Tm8uIEluIGFjdGl2ZSB0cmFuc3BvcnQsIGEgY2VsbCBpcyAmIzgyMjA7ZmlnaHRpbmcmIzgyMjE7IGRpZmZ1c2lvbiwgd2hpY2ggaXMgZHJpdmVuIGJ5IG1vbGVjdWxlcyYjODIxNzsga2luZXRpYyBlbmVyZ3kuIMKgV2hhdCB0aGF0IG1lYW5zIGlzIHRoYXQgY2VsbHMgbmVlZCB0byB1c2UgdGhlaXIgb3duIGVuZXJneSB0byBtb3ZlIGEgc3Vic3RhbmNlIHVwIGEgY29uY2VudHJhdGlvbiBncmFkaWVudC4=[Qq]

[f]Q29ycmVjdC4gVGhpcyBzdGF0ZW1lbnQgaXMgZmFsc2UgYmVjYXVzZSwgaW4gYWN0aXZlIHRyYW5zcG9ydCwgdGhlIGNlbGwgaGFzIHRvIHVzZSBpdHMgb3duIGVuZXJneS4=

Cg==

[Qq]

[q] If you were a molecule, then facilitated diffusion would be most like

[c]IEJlaW5nIGNhcnJpZWQgYWNyb3NzIGEgc3RyZWFtLg==[Qq]

[c]IFdhbGtpbmcgYWNyb3NzIGEgcm9vbS4=[Qq]

[c]IENvYXN0aW5nIGFjcm9zcyBhIG JyaWRnZSBvbiB5b3VyIGJpa2Uu[Qq]

[c]IFJpZGluZyBhIHNraSBsaWZ0Lg==[Qq]

[f]Tm8uIEluIGZhY2lsaXRhdGVkIGRpZmZ1c2lvbiwgdGhlIGNlbGwgbGV0cyBhIG1vbGVjdWxlIHBhc3MgdGhyb3VnaCBpdHMgbWVtYnJhbmUgYnkgcHJvdmlkaW5nIGEgY2hhbm5lbC4gRnJvbSBhIG1vbGVjdWxlJiM4MjE3O3MgcGVyc3BlY3RpdmUsIGJlaW5nIGNhcnJpZWQgYWNyb3NzIGEgc3RyZWFtIHNlZW1zIG1vcmUgbGlrZSBhY3RpdmUgdHJhbnNwb3J0LCBzaW5jZSB0aGUgY2FycmllciBoYXMgdG8gZXhwZW5kIGVuZXJneS4gV2hpY2ggY2hvaWNlIGludm9sdmVzIGEgcGFzc2FnZXdheSB0aGF0JiM4MjE3O3MgZmFjaWxpdGF0aW5nIHlvdXIgY3Jvc3Npbmc/[Qq]

[f]Tm8uIEluIGZhY2lsaXRhdGVkIGRpZmZ1c2lvbiwgdGhlIGNlbGwgbGV0cyBhIG1vbGVjdWxlIHBhc3MgdGhyb3VnaCBpdHMgbWVtYnJhbmUgYnkgcHJvdmlkaW5nIGEgY2hhbm5lbC4gRnJvbSBhIG1vbGVjdWxlJiM4MjE3O3MgcGVyc3BlY3RpdmUsIHdhbGtpbmcgYWNyb3NzIGEgcm9vbSBzZWVtcyBsaWtlIGRpZmZ1c2lvbiAobW92aW5nKSBidXQgbm90IGZhY2lsaXRhdGVkIGRpZmZ1c2lvbiAobW92aW5nIGFjcm9zcyBhIGJhcnJpZXIpLsKgV2hpY2ggY2hvaWNlIGludm9sdmVzIGEgcGFzc2FnZXdheSB0aGF0JiM4MjE3O3MgZmFjaWxpdGF0aW5nIHlvdXIgY3Jvc3Npbmc/[Qq]

[f]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[Qq]

[f]Tm8uIEluIGZhY2lsaXRhdGVkIGRpZmZ1c2lvbiwgdGhlIGNlbGwgbGV0cyBhIG1vbGVjdWxlIHBhc3MgdGhyb3VnaCBpdHMgbWVtYnJhbmUgYnkgcHJvdmlkaW5nIGEgY2hhbm5lbC4gRnJvbSBhIG1vbGVjdWxlJiM4MjE3O3MgcGVyc3BlY3RpdmUsIHJpZGluZyBhIHNraSBsaWZ0wqBzZWVtcyBtb3JlIGxpa2UgYWN0aXZlIHRyYW5zcG9ydCwgc2luY2UgdGhlIGNhcnJpZXIgKHRoZSBza2kgbGlmdCkgaGFzIHRvIGV4cGVuZCBlbmVyZ3kuIFdoaWNoIGNob2ljZSBpbnZvbHZlcyBhIHBhc3NhZ2V3YXkgdGhhdCYjODIxNztzIGZhY2lsaXRhdGluZyB5b3VyIGNyb3NzaW5nPw==

Cg==

[Qq]

[q] Molecules that diffuse through a cell membrane by facilitated diffusion:

[c]IFJlcXVpcmUgYW4gZXhwZW5kaXR1cmUgb2YgY2VsbCBlbmVyZ3k=[Qq]

[c]IE1vdmUgZnJvbSBhbiBhcmVhIG9mIGxvdyBjb25jZW50cmF0aW9uIHRvIGFuIGFyZWEgb2YgaGlnaCBjb25jZW50cmF0aW9u[Qq]

[c]IENhbiBmbG93IGRpcmVjdGx5IHRocm91Z2ggdGhlIGNlbGwmIzgyMTc7cyBwaG9zcGhvbGlwaWQgYmlsYXllci4=[Qq]

[c]IFJlcXVpcmUgdGhlIGFpZCBvZi B0cmFuc3BvcnQgcHJvdGVpbnM=[Qq]

[f]Tm8uIExpa2UgYWxsIGZvcm1zIG9mIGRpZmZ1c2lvbiwgZmFjaWxpdGF0ZWQgZGlmZnVzaW9uIGludm9sdmVzwqB0aGUga2luZXRpYyBlbmVyZ3kgaW4gdGhlIGRpZmZ1c2luZyBtb2xlY3VsZXMuIE5vIGV4dHJhIGVuZXJneSBleHBlbmRpdHVyZSBieSB0aGUgY2VsbCBpcyBpbnZvbHZlZC4=[Qq]

[f]Tm8uIExpa2UgYWxsIGZvcm1zIG9mIGRpZmZ1c2lvbiwgZmFjaWxpdGF0ZWQgZGlmZnVzaW9uIGludm9sdmVzIHRoZSBtb3ZlbWVudCBvZiBtYXRlcmlhbHMgZnJvbSBoaWdoZXIgdG8gbG93ZXIgY29uY2VudHJhdGlvbi4=[Qq]

[f]Tm8uIFRvIA==ZmFjaWxpdGF0ZQ==IG1lYW5zIHRvIGFzc2lzdA==LiBUaGUgcG9pbnQgb2YgZmFjaWxpdGF0ZWQgZGlmZnVzaW9uIGlzIHRoYXQgaXQgaW52b2x2ZXMgbW9sZWN1bGVzIHRoYXQgY2FuJiM4MjE3O3QgZGlmZnVzZSB0aHJvdWdoIHRoZSBwaG9zcGhvbGlwaWQgYmlsYXllciwgYW5kIG5lZWQgc29tZSBraW5kIG9mIGFzc2lzdGFuY2UgdG8gbWFrZSB0aGVpciB3YXkgdGhyb3VnaC4=[Qq]

[f]RmFidWxvdXMhIE1vbGVjdWxlcyB0aGF0IHBhc3MgdGhyb3VnaCB0aGUgbWVtYnJhbmUgYnkgZmFjaWxpdGF0ZWQgZGlmZnVzaW9uIGFyZSBkb2luZyBzbyB3aXRoIHRoZSBhc3Npc3RhbmNlIG9mIGEgcHJvdGVpbiBjaGFubmVsIG9yIHRyYW5zcG9ydCBwcm90ZWluIHRoYXQgZmFjaWxpdGF0ZXMgdGhlaXIgcGFzc2FnZS4=

Cg==

[Qq]

[q] A molecule that can diffuse freely through a phospholipid bilayer is probably

[c]wqBwb2xhcg==[Qq]

[c]IFBvc2l0aXZlbHkgY2hhcmdlZA==[Qq]

[c]wqBub24t cG9sYXI=[Qq]

[c]wqBhIGxhcmdlIHByb3RlaW4=[Qq]

[f]Tm8uIFBvbGFyIG1vbGVjdWxlcyBjYW4mIzgyMTc7dCBwYXNzIHRocm91Z2ggdGhlIGh5ZHJvcGhvYmljLCBub24tcG9sYXIgcGFydCBvZiB0aGUgcGhvc3Bob2xpcGlkIGJpbGF5ZXIuIEp1c3QgcmVtZW1iZXIgdGhhdCBvaWwgKG5vbi1wb2xhcikgYW5kIHdhdGVyIChwb2xhcikgZG9uJiM4MjE3O3QgbWl4Lg==[Qq]

[f]Tm8uIENoYXJnZWQgbW9sZWN1bGVzIGNhbiYjODIxNzt0IHBhc3MgdGhyb3VnaCB0aGUgaHlkcm9waG9iaWMsIG5vbi1wb2xhciBwYXJ0IG9mIHRoZSBwaG9zcGhvbGlwaWQgYmlsYXllci4=[Qq]

[f]WWVzLiBOb24tcG9sYXIgbW9sZWN1bGVzIChmYXRzLCBvaWxzLCBzdGVyb2lkIGhvcm1vbmVzKSBjYW4gZnJlZWx5IHBhc3MgdGhyb3VnaCBhIHBob3NwaG9saXBpZCBiaWxheWVyLg==[Qq]

[f]Tm8uIExhcmdlIHByb3RlaW5zIGNhbiYjODIxNzt0IHBhc3MgZGlyZWN0bHkgdGhyb3VnaCBhIHBob3NwaG9saXBpZCBiaWxheWVyLiBJZiB0aGV5IGVudGVyZWQgYSBjZWxsIGF0IGFsbCwgaXQgd291bGQgaGF2ZSB0byBiZSB0aHJvdWdoIGEgdHJhbnNwb3J0IHByb3RlaW4u

Cg==

[Qq]

[q] Which of the following best describes what occurs during facilitated diffusion?

[c]IEluIGZhY2lsaXRhdGVkIGRpZmZ1c2lvbiwgc3Vic3RhbmNlcyBkaWZmdXNlIHRocm91Z2ggdGhlIHBob3NwaG9saXBpZCBiaWxheWVyIGFzIHRoZXkgZW50ZXIgb3IgbGVhdmUgdGhlIGNlbGwuIE5vIGNlbGwgZW5lcmd5IGlzIHJlcXVpcmVkLg==[Qq]

[c]IEluIGZhY2lsaXRhdGVkIGRpZmZ1c2lvbiwgdGhlIGNlbGwgdXNlcyBpdHMgb3duIGVuZXJneSB0byBwdW1wIHN1YnN0YW5jZXMgZnJvbSBsb3dlciBjb25jZW50cmF0aW9uIHRvIGhpZ2hlciBjb25jZW50cmF0aW9uLg==[Qq]

[c]IEluIGZhY2lsaXRhdGVkIGRpZmZ1c2lvbiwgbW9sZWN1bGVzIGRpZmZ1c2UgaW50byB0aGUgY2Vs bCB0aHJvdWdoIHByb3RlaW4gY2hhbm5lbHMuIE5vIGNlbGwgZW5lcmd5IGlzIHJlcXVpcmVkLg==[Qq]

[c]IEluIGZhY2lsaXRhdGVkIGRpZmZ1c2lvbiwgdGhlIGNlbGwgdXNlcyBpdHMgb3duIGVuZXJneSB0byBwdW1wIG1hdGVyaWFscyB0aHJvdWdoIHRoZSBwaG9zcGhvbGlwaWQgYmlsYXllci4=[Qq]

[f]IE5vLiBJbiBmYWNpbGl0YXRlZCBkaWZmdXNpb24sIHRoZSBjZWxsIHByb3ZpZGVzIHByb3RlaW4gY2hhbm5lbHMgb3IgY2FycmllciBwcm90ZWlucyB0byBhbGxvdyBzdWJzdGFuY2VzIHRvIGRpZmZ1c2UgaW50byBvciBvdXQgb2YgdGhlIGNlbGwuIE5vIGVuZXJneSBpcyByZXF1aXJlZCBvbiB0aGUgY2VsbOKAmXMgcGFydC4=[Qq]

[f]IE5vLiBJbiBmYWNpbGl0YXRlZCBkaWZmdXNpb24sIHRoZSBjZWxsIHByb3ZpZGVzIHByb3RlaW4gY2hhbm5lbHMgb3IgdXNlcyBjYXJyaWVyIHByb3RlaW5zIHRvIGFsbG93IHN1YnN0YW5jZXMgdG8gZGlmZnVzZSBpbnRvIG9yIG91dCBvZiB0aGUgY2VsbC4gTm8gZW5lcmd5IGlzIHJlcXVpcmVkIG9uIHRoZSBjZWxs4oCZcyBwYXJ0LiBJbnN0ZWFkLCB0aGUgZW5lcmd5IGlzIHByb3ZpZGVkIGJ5IHRoZSBraW5ldGljIGVuZXJneSBvZiB0aGUgZGlmZnVzaW5nIG1vbGVjdWxlcy4=[Qq]

[f]IEV4Y2VsbGVudCEgRmFjaWxpdGF0ZWQgZGlmZnVzaW9uIGlzIHN0aWxsIGEgZm9ybSBvZiBkaWZmdXNpb24sIGJ1dCByYXRoZXIgdGhhbiBzaW1wbHkgZGlmZnVzaW5nIHRocm91Z2ggdGhlIGxpcGlkIGJpbGF5ZXIsIHRoZSBwYXNzYWdlIG9mIG1vbGVjdWxlcyBpcyBmYWNpbGl0YXRlZCAobWFkZSBlYXNpZXIpIHRocm91Z2ggcHJvdGVpbiBjaGFubmVscyBvciBjYXJyaWVyIHByb3RlaW5zIHRoYXQgbGV0IHNwZWNpZmljIG1vbGVjdWxlcyBwYXNzIHRocm91Z2ggdGhlIG1lbWJyYW5lLg==[Qq]

[f]IE5vLiBJbiBmYWNpbGl0YXRlZCBkaWZmdXNpb24sIHRoZSBjZWxsIHByb3ZpZGVzIHByb3RlaW4gY2hhbm5lbHMgb3IgY2FycmllciBwcm90ZWlucyB0byBhbGxvdyBzdWJzdGFuY2VzIHRvIGRpZmZ1c2UgaW50byBvciBvdXQgb2YgdGhlIGNlbGwuIE5vIGVuZXJneSBpcyByZXF1aXJlZCBvbiB0aGUgY2VsbOKAmXMgcGFydC4gSW5zdGVhZCwgdGhlIGVuZXJneSBpcyBwcm92aWRlZCBieSB0aGUga2luZXRpYyBlbmVyZ3kgb2YgdGhlIGRpZmZ1c2luZyBtb2xlY3VsZXMu

Cg==

[Qq]

[q]When a substance created inside the cell is exported outside the cell, it leaves the cell through

[c]ZW5kb2N5dG9zaXM=[Qq]

[c]ZXhvY3l0 b3Npcw==[Qq]

[c]cGhhZ29jeXRvc2lz[Qq]

[f]Tm8uIEVuZG9jeXRvc2lzIG1lYW5zICYjODIyMDtpbnRvIHRoZSBjZWxsLiYjODIyMTsgV2hhdCBpcyB0aGUgdGVybSBmb3IgJiM4MjIwO2xlYXZpbmcgdGhlIGNlbGw/JiM4MjIxOw==[Qq]

[f]WWVzLsKgV2hlbiBhIHN1YnN0YW5jZcKgY3JlYXRlZCBpbnNpZGUgdGhlIGNlbGwgaXMgZXhwb3J0ZWQgb3V0c2lkZSB0aGUgY2VsbCwgaXQgbGVhdmVzIHRoZSBjZWxsIHRocm91Z2ggZXhvY3l0b3Npcy4=[Qq]

[f]Tm8uIFBoYWdvY3l0b3NpcyBpbnZvbHZlcyBjZWxscyBlbmd1bGZpbmcgZm9yZWlnbiBvYmplY3RzIGFuZCBicmluZ2luZyB0aGVtIGludG8gdGhlIGNlbGwuIEhlcmUsIHlvdSYjODIxNztyZSBsb29raW5nIGZvciBhIHRlcm0gdGhhdCBtZWFucyAmIzgyMjA7bGVhdmluZyB0aGUgY2VsbC4mIzgyMjE7

Cg==

[Qq]

[q] Passive transport is defined as the movement of any substance across a membrane without the use of

[c]IGNlbGwg ZW5lcmd5[Qq]

[c]wqBtZW1icmFuZSBjaGFubmVscw==[Qq]

[c]IGRpZmZ1c2lvbg==[Qq]

[f]Q29ycmVjdC7CoFBhc3NpdmUgdHJhbnNwb3J0IGlzIGRlZmluZWQgYXMgdGhlIG1vdmVtZW50IG9mIGFueSBzdWJzdGFuY2UgYWNyb3NzIGEgbWVtYnJhbmUgd2l0aG91dCB0aGUgdXNlIG9mIGNlbGwgZW5lcmd5Lg==[Qq]

[f]Tm8uIFBhc3NpdmUgdHJhbnNwb3J0IGluY2x1ZGVzIGRpZmZ1c2lvbiB0aHJvdWdoIG1lbWJyYW5lIGNoYW5uZWxzLiBDb25zaWRlciB0aGUgZmFjdCB0aGF0ICYjODIyMDtwYXNzaXZlIHRyYW5zcG9ydCYjODIyMTsgaXMgdGhlIG9wcG9zaXRlIG9mICYjODIyMDthY3RpdmUgdHJhbnNwb3J0LCYjODIyMTsgYW5kIHlvdSYjODIxNztsbCBoYXZlIHlvdXIgYW5zd2VyLg==[Qq]

[f]Tm8uIFRoZSB0ZXJtIA==cGFzc2l2ZSB0cmFuc3BvcnQ=IGhhcyBhIGxvdCBpbiBjb21tb24gd2l0aCB0aGUgdGVybSA=ZGlmZnVzaW9uLsKgQ29uc2lkZXIgdGhlIGZhY3QgdGhhdCAmIzgyMjA7cGFzc2l2ZSB0cmFuc3BvcnQmIzgyMjE7IGlzIHRoZSBvcHBvc2l0ZSBvZiAmIzgyMjA7YWN0aXZlIHRyYW5zcG9ydCwmIzgyMjE7IGFuZCB5b3UmIzgyMTc7bGwgaGF2ZSB5b3VyIGFuc3dlci4=

[Qq]

[q] Which of the following terms describes the process by which the cell membrane moves substances from lower concentration to higher concentration.

[c]IGZhY2lsaXRhdGVkIGRpZmZ1c2lvbg==[Qq]

[c]IG9zbW9zaXM=[Qq]

[c]IGRpZmZ1c2lvbg==[Qq]

[c]IGFjdGl2ZSB0 cmFuc3BvcnQu[Qq]

[f]IE5vLiBJbiBmYWNpbGl0YXRlZCBkaWZmdXNpb24sIG1vbGVjdWxlcyBhcmUgc3RpbGwgZGlmZnVzaW5nIGZyb20gaGlnaGVyIHRvIGxvd2VyIGNvbmNlbnRyYXRpb24uIEhvd2V2ZXIsIHJhdGhlciB0aGFuIHNpbXBseSBkaWZmdXNpbmcgdGhyb3VnaCB0aGUgbGlwaWQgYmlsYXllciwgdGhleSBwYXNzIHRocm91Z2ggYSBwcm90ZWluIGNoYW5uZWwuIE5leHQgdGltZSwgY2hvb3NlIGEgcHJvY2VzcyB0aGF0IHJlZmxlY3RzIHRoZSBuZWVkIGZvciBjZWxscyB0byBhY3RpdmVseSBwdW1wIG1hdGVyaWFscyBmcm9tIGxvd2VyIHRvIGhpZ2hlciBjb25jZW50cmF0aW9uLg==[Qq]

[f]IE5vLiBPc21vc2lzIGlzIHRoZSBkaWZmdXNpb24gb2Ygd2F0ZXIuIExpa2UgYWxsIGRpZmZ1c2lvbiBwcm9jZXNzZXMsIHdhdGVyIG1vdmVzIGZyb20gd2hlcmUgaXQgaXMgbW9yZSBjb25jZW50cmF0ZWQgdG8gd2hlcmUgaXQgaXMgbGVzcyBjb25jZW50cmF0ZWQu[Qq]

[f]IE5vLiBEaWZmdXNpb24gaXMgdGhlIG1vdmVtZW50IG9mIHN1YnN0YW5jZXMgZnJvbSBoaWdoZXIgY29uY2VudHJhdGlvbiB0byBsb3dlciBjb25jZW50cmF0aW9uLg==[Qq]

[f]IENvcnJlY3QhIEFjdGl2ZSB0cmFuc3BvcnQgaW52b2x2ZXMgY2VsbHMgaGF2aW5nIHRvIHB1bXAgbWF0ZXJpYWxzIGZyb20gbG93ZXIgdG8gaGlnaGVyIGNvbmNlbnRyYXRpb24sIGFnYWluc3QgdGhlIGRpcmVjdGlvbiBvZiBkaWZmdXNpb24u

Cg==

[Qq]

[q]In nerve cells, the amount of positively charged potassium ions inside the cell is much higher than the amount outside the cell. For the cell to take up more potassium, which process is required?

[c]YWN0aXZlIHRy YW5zcG9ydA==[Qq]

[c]cGFzc2l2ZSB0cmFuc3BvcnQ=[Qq]

[c]ZmFjaWxpdGF0ZWQgZGlmZnVzaW9u[Qq]

[c]c2ltcGxlIGRpZmZ1c2lvbg==[Qq]

[f]WWVzLiBUaGUgY2VsbCBpcyBnb2luZyB0byBoYXZlIHRvIGV4cGVuZCBpdHMgb3duIGVuZXJneSB0byBtb3ZlIHRoZSBwb3Rhc3NpdW0gZnJvbSBhIGxvd2VyIGNvbmNlbnRyYXRpb24sIG91dHNpZGUgdGhlIGNlbGwsIHRvIGEgaGlnaGVyIGNvbmNlbnRyYXRpb24gaW5zaWRlIHRoZSBjZWxsLg==[Qq]

[f]Tm8uIFBhc3NpdmUgdHJhbnNwb3J0IGlzIGVzc2VudGlhbGx5IHRoZSBzYW1lIGFzIGRpZmZ1c2lvbi4gSXQgcmVzdWx0cyBpbiBhbiBlcXVhbCBjb25jZW50cmF0aW9uIG9mIHN1YnN0YW5jZXMgYWNyb3NzIG1lbWJyYW5lcy4gV2hhdCBwcm9jZXNzIHdvcmtzIGFnYWluc3QgZGlmZnVzaW9uPw==[Qq]

[f]Tm8uIEZhY2lsaXRhdGVkIGRpZmZ1c2lvbiByZXN1bHRzIGluIGFuIGVxdWFsIGNvbmNlbnRyYXRpb24gb2Ygc3Vic3RhbmNlcyBhY3Jvc3MgbWVtYnJhbmVzLiBXaGF0IHByb2Nlc3Mgd29ya3MgYWdhaW5zdCBkaWZmdXNpb24/[Qq]

[f]Tm8uIFNpbXBsZSBkaWZmdXNpb24gaXMgZXNzZW50aWFsbHkgdGhlIHNhbWUgYXMgZGlmZnVzaW9uLiBJdCByZXN1bHRzIGluIGFuIGVxdWFsIGNvbmNlbnRyYXRpb24gb2Ygc3Vic3RhbmNlcyBhY3Jvc3MgbWVtYnJhbmVzLiBXaGF0IHByb2Nlc3Mgd29ya3MgYWdhaW5zdCBkaWZmdXNpb24/

Cg==

[Qq]

[q]In the diagram below, number 3 is

[c]YWN0aXZlIHRy YW5zcG9ydA==[Qq]

[c]ZmFjaWxpdGF0ZWQgZGlmZnVzaW9u[Qq]

[c]c2ltcGxlIGRpZmZ1c2lvbg==[Qq]

[f]WWVzLsKgSW4gbnVtYmVyIDMsIHRoZSBjZWxsIGlzIG1vdmluZyBtb2xlY3VsZXMgZnJvbSBsb3dlciB0byBoaWdoZXIgY29uY2VudHJhdGlvbiwgYSBwcm9jZXNzIGtub3duIGFzIGFjdGl2ZSB0cmFuc3BvcnQu[Qq]

[f]Tm8uIEZhY2lsaXRhdGVkIGRpZmZ1c2lvbiBhbGxvd3MgbWF0ZXJpYWxzIHRvIGRpZmZ1c2UgZG93biB0aGVpciBjb25jZW50cmF0aW9uIGdyYWRpZW50cywgYnV0IHByb3ZpZGVzIGEgcHJvdGVpbiBjaGFubmVsIGZvciB0aGUgbWF0ZXJpYWxzIHRvIHBhc3MgdGhyb3VnaC4gSXMgbnVtYmVyIDMgZ29pbmcgdXAgb3IgZG93biBpdHMgY29uY2VudHJhdGlvbiBncmFkaWVudD8=[Qq]

[f]Tm8uIFNpbXBsZSBkaWZmdXNpb24gaXMgdGhlIG1vdmVtZW50IG9mIG1hdGVyaWFscyBkaXJlY3RseSB0aHJvdWdoIHRoZSBwaG9zcGhvbGlwaWQgYmlsYXllci4=

Cg==

[Qq]

[q]In the diagram below, number 1 is

[c]YWN0aXZlIHRyYW5zcG9ydA==[Qq]

[c]ZmFjaWxpdGF0ZWQgZGlmZnVzaW9u[Qq]

[c]c2ltcGxlIGRp ZmZ1c2lvbg==[Qq]

[f]Tm8uwqBJbiBhY3RpdmUgdHJhbnNwb3J0LCB0aGUgY2VsbCBtb3Zlc8KgbW9sZWN1bGVzIGZyb20gbG93ZXIgdG8gaGlnaGVyIGNvbmNlbnRyYXRpb24uIEluIG51bWJlciAxLMKgwqB0aGUgbW92ZW1lbnQgaXMgZnJvbSBoaWdoZXIgdG8gbG93ZXIu[Qq]

[f]Tm8uIEluIGZhY2lsaXRhdGVkIGRpZmZ1c2lvbiwgbWF0ZXJpYWxzIGFyZcKgYWxsb3dlZCB0byBkaWZmdXNlIGRvd24gdGhlaXIgY29uY2VudHJhdGlvbiBncmFkaWVudHMsIGJ1dCBhIHByb3RlaW4gY2hhbm5lbCBpcyBwcm92aWRlZCBmb3IgdGhlIG1hdGVyaWFscyB0byBwYXNzIHRocm91Z2guIFRoZXJlJiM4MjE3O3Mgbm8gY2hhbm5lbCBpbiBudW1iZXIgMS4=[Qq]

[f]WWVzLiBOdW1iZXIgMSBpcyBzaW1wbGUgZGlmZnVzaW9uIHRocm91Z2ggdGhlIHBob3NwaG9saXBpZCBiaWxheWVyLiBJbiBudW1iZXIgMywgdGhlIG1hdGVyaWFscyBhcmUgbm90IGdvaW5nIHRocm91Z2ggdGhlIHBob3NwaG9saXBpZCBiaWxheWVyLCBidXQgdGhyb3VnaCBhIGNhcnJpZXIgcHJvdGVpbi4=

Cg==

[Qq]

[q] As part of the immune response, a white blood cell swallows an invading bacteria. Another name for that process is

[c]IGV4b2N5dG9zaXMu[Qq]

[c]IHBhc3NpdmUgdHJhbnNwb3J0Lg==[Qq]

[c]IHBoYWdvY3 l0b3Npcy4=[Qq]

[c]wqBmYWNpbGl0YXRlZCBkaWZmdXNpb24=[Qq]

[f]Tm8uIEV4b2N5dG9zaXMgbW92ZXMgdGhpbmdzIG91dCBvZiB0aGUgY2VsbC4=[Qq]

[f]Tm8uIFBhc3NpdmUgdHJhbnNwb3J0IGluY2x1ZGVzIHByb2Nlc3NlcyB0aGF0IGRvbiYjODIxNzt0IHJlcXVpcmUgYW55IGNlbGwgZW5lcmd5LCBsaWtlIHNpbXBsZSBhbmQgZmFjaWxpdGF0ZWQgZGlmZnVzaW9uLiBTd2FsbG93aW5nIGFuIGVudGlyZSBjZWxsIHJlcXVpcmVzIGEgbG90IG9mIGVuZXJneS4=[Qq]

[f]WWVzLiBQaGFnb2N5dG9zaXMgaXMgdGhlIG5hbWUgZm9yIHRoZSBwcm9jZXNzIGluIHdoaWNoIGNlbGxzIHN3YWxsb3cgcGFydGljbGVzIG9yIG90aGVyIGNlbGxzLg==[Qq]

[f]Tm8uwqBGYWNpbGl0YXRlZCBkaWZmdXNpb24gaW52b2x2ZXMgbW9sZWN1bGVzIGRpZmZ1c2luZyB0aHJvdWdoIHByb3RlaW4gY2hhbm5lbHMuIFdoYXQmIzgyMTc7cyBhYm92ZSBpcyBhIGZvcm0gb2YgZW5kb2N5dG9zaXMu

Cg==

[Qq]

[q]As shown in this diagram, the type of endocytosis in which molecules bind with receptors on the membrane, causing the membrane to pinch in and create a coated vesicle is called.

[c]cGhhZ29jeXRvc2lz[Qq]

[c]cGlub2N5dG9zaXM=[Qq]

[c]cmVjZXB0b3IgbWVkaWF0 ZWQtZW5kb2N5dG9zaXM=[Qq]

[f]Tm8uIFBoYWdvY3l0b3NpcyBpbnZvbHZlcyBhIHNpZ25pZmljYW50IGV4dGVuc2lvbiBvZiB0aGUgbWVtYnJhbmUuIFRoZXNlIGV4dGVuc2lvbnMsIGNhbGxlZCBwc2V1ZG9wb2RzLCBlbmd1bGYgbGFyZ2UgcGFydGljbGVzIG9yIGVudGlyZSBjZWxscy4=[Qq]

[f]Tm8uIFBpbm9jeXRvc2lzIGRvZXNuJiM4MjE3O3QgaW52b2x2ZSB0aGUgYmluZGluZyBvZiByZWNlcHRvcnMu[Qq]

[f]WWVzLiBXaGF0JiM4MjE3O3Mgc2hvd24gaGVyZSBpcyByZWNlcHRvci1tZWRpYXRlZCBlbmRvY3l0b3Npcy4=

Cg==

[Qq]

[q]The type of endocytosis in which the membrane pinches in and takes a small “sip” of whatever is outside the membrane is called

[c]cGhhZ29jeXRvc2lz[Qq]

[c]cGlub2N5 dG9zaXM=[Qq]

[c]cmVjZXB0b3IgbWVkaWF0ZWQtZW5kb2N5dG9zaXM=[Qq]

[f]Tm8uIFBoYWdvY3l0b3NpcyBpbnZvbHZlcyBhIHNpZ25pZmljYW50IGV4dGVuc2lvbiBvZiB0aGUgbWVtYnJhbmUuIFRoZXNlIGV4dGVuc2lvbnMsIGNhbGxlZCBwc2V1ZG9wb2RzLCBlbmd1bGYgbGFyZ2UgcGFydGljbGVzIG9yIGVudGlyZSBjZWxscy4=[Qq]

[f]WWVzLsKgV2hhdCYjODIxNztzIHNob3duIGhlcmUgaXMgcGlub2N5dG9zaXMsIGEgc21hbGwgcGluY2hpbmcgaW4gb2YgdGhlIGNlbGwgbWVtYnJhbmUgdGhhdCBlbmFibGVzIHRoZSBjZWxsIHRvICYjODIyMDt0YWtlIGEgc2lwJiM4MjIxOyBvZiB0aGUgc3Vycm91bmRpbmcgZXh0cmFjZWxsdWxhciBmbHVpZC4=[Qq]

[f]Tm8uIFJlY2VwdG9yLW1lZGlhdGVkIGVuZG9jeXRvc2lzIA==ZG9lcw==IGludm9sdmUgcGluY2hpbmcgb2YgdGhlIG1lbWJyYW5lLCBidXQgdGhlIHByb2Nlc3MgaXMgaW5pdGlhdGVkIGJ5IHRoZSBiaW5kaW5nIG9mIGNlcnRhaW4gc3Vic3RhbmNlcyB0byByZWNlcHRvcnMsIHdoaWNoIHlvdSBkb24mIzgyMTc7dCBzZWUgaGVyZS4=

Cg==

[Qq]

[q]In this type of endocytosis there is a significant extension of the membrane. These extensions, called pseudopods, engulf large particles or entire cells.

[c]cGhhZ29j eXRvc2lz[Qq]

[c]cGlub2N5dG9zaXM=[Qq]

[c]cmVjZXB0b3IgbWVkaWF0ZWQtZW5kb2N5dG9zaXM=[Qq]

[f]WWVzLiBXaGF0JiM4MjE3O3Mgc2hvd24gaGVyZSBpcyBwaGFnb2N5dG9zaXMu[Qq]

[f]Tm8uIFBpbm9jeXRvc2lzIGlzIGEgc21hbGwgcGluY2hpbmctaW4gb2YgdGhlIGNlbGwgbWVtYnJhbmUgdGhhdCBlbmFibGVzIHRoZSBjZWxsIHRvICYjODIyMDt0YWtlIGEgc2lwJiM4MjIxOyBvZiB0aGUgc3Vycm91bmRpbmcgZXh0cmFjZWxsdWxhciBmbHVpZC4gV2hhdCBpcyBzaG93biBoZXJlIGlzIG9uIGEgbXVjaCBsYXJnZXIgc2NhbGUu[Qq]

[f]Tm8uIFJlY2VwdG9yLW1lZGlhdGVkIGVuZG9jeXRvc2lzIA==ZG9lcw==IGludm9sdmUgcGluY2hpbmcgb2YgdGhlIG1lbWJyYW5lLCBidXQgdGhlIHByb2Nlc3MgaXMgaW5pdGlhdGVkIGJ5IHRoZSBiaW5kaW5nIG9mIGNlcnRhaW4gc3Vic3RhbmNlcyB0byByZWNlcHRvcnMsIHdoaWNoIHlvdSBkb24mIzgyMTc7dCBzZWUgaGVyZS4gQWxzbywgdGhlIHByb2Nlc3Mgc2hvd24gaGVyZSBpbnZvbHZlcyBtZW1icmFuZSBjaGFuZ2VzIG9uIGEgbXVjaCBsYXJnZXIgc2NhbGUu

Cg==

Wy8hXQ==

[Qq]

[q][hangman] is the movement of molecules from where they’re more concentrated to where they’re less concentrated.

[c]ZGlmZnVzaW9u

Cg==

[Qq]

[q]One way to talk about diffusion is to say the molecules in a fluid will move down a [hangman] [hangman].

[c]Y29uY2VudHJhdGlvbg==[Qq]

[c]IGdyYWRpZW50[Qq]

[q]When substances diffuse directly through a membrane’s phospholipid bilayer, the process is called [hangman] [hangman].

[c]c2ltcGxl[Qq]

[c]ZGlmZnVzaW9u[Qq]

[q]When substances diffuse into a cell by passing through a protein channel, the process is called [hangman] [hangman].

[c]ZmFjaWxpdGF0ZWQ=[Qq]

[c]ZGlmZnVzaW9u[Qq]

[q]When cells expend energy to move a substance from lower concentration to higher concentration, this process is known as [hangman] [hangman].

[c]YWN0aXZlIA==[Qq]

[c]dHJhbnNwb3J0[Qq]

[q]A vesicle filled with some substance fuses with the membrane, releasing that substance outside the cell. This process is called [hangman].

[c]ZXhvY3l0b3Npcw==[Qq]

[q]The cell membrane pinches in, taking in something outside of the cell and enclosing it within a vesicle. This process is called [hangman].

[c]ZW5kb2N5dG9zaXM=[Qq]

[q]The kind of endocytosis in which a small portion of the membrane pinches in, allowing the cell to “take a sip” of the fluid outside of the cell, is called [hangman].

[c]cGlub2N5dG9zaXM=[Qq]

[q]The kind of endocytosis in which a large portion of the membrane surrounds a food particle (or even another cell), and then brings that particle into the cell is called [hangman].

[c]cGhhZ29jeXRvc2lz[Qq]

[q]The best name for the process shown in this diagram is [hangman].

[c]ZGlmZnVzaW9u[Qq]

[q]The best name for the process shown in this diagram is [hangman] [hangman],

[c]c2ltcGxl[Qq]

[c]ZGlmZnVzaW9u[Qq]

[q]The best name for the process shown in this diagram is [hangman] [hangman]

[c]ZmFjaWxpdGF0ZWQ=[Qq]

[c]ZGlmZnVzaW9u[Qq]

[q]The best name for the process shown in this diagram is [hangman] [hangman],

[c]YWN0aXZl[Qq]

[c]dHJhbnNwb3J0[Qq]

[q]The best name for the process shown in this diagram is [hangman].

[c]ZXhvY3l0b3Npcw==[Qq]

[q]The best name for the process shown at “A,” “B,” and “C” in this diagram is [hangman],

[c]ZW5kb2N5dG9zaXM=[Qq]

[q]The specific type of endocytosis shown in this diagram is [hangman],

[c]cGlub2N5dG9zaXM=[Qq]

[q]The specific type of endocytosis shown in this diagram is [hangman].

[c]cGhhZ29jeXRvc2lz[Qq]

[q]The specific type of endocytosis shown in this diagram is

[hangman]-[hangman] [hangman]

[c]cmVjZXB0b3I=[Qq]

[c]bWVkaWF0ZWQ=[Qq]

[c]ZW5kb2N5dG9zaXM=[Qq]

[x]

[restart]

[/qwiz]