For a deeper dive into this material, complete these tutorials: Topics 2.5 -2.7, 2.9: Membrane Transport
1. Watch this Video
2.a. Read this: An important idea that didn’t make it into the video
Because water is polar, it can only diffuse through the phospholipid portion of the bilayer at a very slow rate. To facilitate water’s diffusion, cells provide special channels called aquaporins (shown bel0w).
2.b. Study this Summary
- What is Diffusion?
- Diffusion is the movement of molecules from areas of higher concentration to areas of lower concentration, driven by their kinetic energy.
- It is a spontaneous process during which substances flow “down” a concentration gradient.
- How Cells Control Diffusion:
- Diffusion is a type of passive transport, requiring no cellular energy.
- Simple Diffusion: Small, nonpolar molecules (e.g., oxygen, carbon dioxide) and nonpolar substances (e.g., steroid hormones) pass directly through the phospholipid bilayer.
- Facilitated Diffusion: Polar molecules and ions (e.g., glucose, amino acids, calcium) require protein channels to cross the membrane.
- Active vs. Passive Transport:
- Passive Transport: Molecules move down their concentration gradient (high to low) using their kinetic energy, without cellular energy.
- Active Transport: Molecules are pumped up a concentration gradient (from low to high concentration) using cellular energy, typically ATP or electron flow.
- Endocytosis vs. Exocytosis:
- Both are forms of bulk transport and require cellular energy.
- Endocytosis: The membrane pinches inward to enclose particles or fluids, forming a vesicle.
- Exocytosis: Vesicles fuse with the membrane to release their contents outside the cell.
- Both processes involve the cytoskeleton to reshape the membrane.
- Membrane Potential:
- An electrical charge across the membrane creates a voltage difference.
- Cells generate membrane potential by pumping ions across membranes using energy.
- Examples:
- Proton pumps in mitochondria create an electrochemical gradient, driving ATP synthesis.
- Similar processes occur in chloroplasts and nerve cells to enable photosynthesis and nerve impulses, respectively.
3. Master these Flashcards
[qdeck random = “true;” style=”width: 528px; border: 2px solid black; ” bold_text=”false”]
[h] Membrane Transport
[i]
[q]In the context of membranes, define what it means to be selectively permeable.
[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).
[q]What’s happening in the image below?
[a]The image shows diffusion: the movement of molecules from where they’re more concentrated to where they’re less concentrated.
[q]What’s the relationship between diffusion and concentration gradients?
[a]One way to talk about diffusion is to say the molecules in a fluid will move down a concentration gradient, moving from high concentration to low concentration.
[q]Define simple diffusion, and draw a simple sketch.
[a]Simple diffusion is when substances diffuse directly through a membrane’s phospholipid bilayer. Your sketch should look like this:
[q]Define facilitated diffusion, and draw a simple sketch.
[a]Facilitied diffusion is when substances diffuse into a cell by passing through a protein channel. A sample sketch should look like this:
[q]Define active transport, and draw a simple sketch.
[a]Active transport is when cells expend energy to move a substance from lower concentration to higher concentration.
[q]What types of molecules can pass through the membrane via simple diffusion?
[a]Simple diffusion works for small nonpolar molecules such as oxygen (O2) and carbon dioxide (CO2), which can diffuse directly through the phospholipid bilayer. So can larger nonpolar molecules such as lipids.
[q]What types of molecules can only pass through the membrane via facilitated diffusion (and why).
[a]The nonpolar interior of the phospholipid bilayer is impermeable to charged or polar molecules. For these molecules to diffuse into or out of the cell, a protein channel is needed. Examples of such molecules include amino acids, mono- and disaccharides, ions, and larger molecules (such as proteins).
[q]How does water diffuse into and out of cells.
[a]Because water is polar, it can only diffuse through the phospholipid portion of the bilayer at a very slow rate. To facilitate water’s diffusion, cells provide special channels called aquaporins.
[q]Compare and contrast passive and active transport.
[a]In passive transport, the cell doesn’t have to expend any of its own energy. Instead, molecules move down their concentration gradient and diffuse into or out of the cell. In active transport, the cell has to use its own energy, usually in the form of ATP, to pump molecules up a gradient from lower to higher concentration.
[q]Describe exocytosis, and draw a simple sketch representing the process.
[a]Exocytosis occurs when a vesicle filled with some substance fuses with the membrane, releasing that substance outside the cell.
[q]Describe endocytosis.
[a]During endocytosis, the cell membrane pinches in, taking in something outside of the cell and enclosing it within a vesicle.
[q]Describe receptor-mediated endocytosis.
[a]In receptor-mediated endocytosis, the membrane only pinches in when a molecule outside the cell binds with a receptor molecule in the membrane
[x]
If you want more practice, please press the restart button below. Otherwise, follow the links below.
[restart]
[/qdeck]
4. Tackle this Quiz
[qwiz random = “true;” style = “border: 3px solid black; “]
[h] Membrane Transport
[i]
[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
[fx] No. Please try again.
[f*] Excellent!
[l]ink molecules spread out
[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
[fx] No. Please try again.
[f*] Great!
[q labels = “top”]
[l]active transport
[fx] No. Please try again.
[f*] Great!
[l]simple diffusion
[fx] No, that’s not correct. Please try again.
[f*] Correct!
[l]facilitated diffusion
[fx] No. Please try again.
[f*] Excellent!
[q labels = “top”]
| ____________________________ | _________________________ |
[l]exocytosis
[fx] No. Please try again.
[f*] Good!
[l]endocytosis
[fx] No. Please try again.
[f*] Great!
[q labels = “top”]
[l]molecules released from the cell
[fx] No, that’s not correct. Please try again.
[f*] Excellent!
[l]vesicle
[fx] No. Please try again.
[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
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[q] Diffusion is a term for the movement of molecules from
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Cg==[q] Diffusion is about the random movement of
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[q] For diffusion to occur, there must be:
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Cg==[Qq]
[q] Cell membrane channels are made of
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[q] The cell membrane lets only some things in and out. The best way to describe that is to say that the membrane is
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Cg==[Qq]
[q]When molecules diffuse, they flow
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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.
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Cg==[Qq]
[q] If you were a molecule, then facilitated diffusion would be most like
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[f]WWVzISBJbiBmYWNpbGl0YXRlZCBkaWZmdXNpb24sIHRoZSBjZWxsIGxldHMgYSBtb2xlY3VsZSBwYXNzIHRocm91Z2ggaXRzIG1lbWJyYW5lIGJ5IHByb3ZpZGluZyBhIGNoYW5uZWwuIElmIHlvdSBjb2FzdCBhY3Jvc3MgYSBicmlkZ2Ugb24geW91ciBiaWtlLCB5b3UmIzgyMTc7cmUgdXNpbmcgeW91ciBraW5ldGljIGVuZXJneSB0byBjcm9zcyBhIGJhcnJpZXIsIHVzaW5nIGEgcGFzc2FnZXdheSAodGhlIGJyaWRnZSkgdGhhdCBmYWNpbGl0YXRlcyB5b3VyIGNyb3NzaW5nLg==[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]IG5vbn BvbGFy[Qq]
[c]wqBhIGxhcmdlIHByb3RlaW4=[Qq]
[f]Tm8uIFBvbGFyIG1vbGVjdWxlcyBjYW4mIzgyMTc7dCBwYXNzIHRocm91Z2ggdGhlIGh5ZHJvcGhvYmljLCBub25wb2xhciBwYXJ0IG9mIHRoZSBwaG9zcGhvbGlwaWQgYmlsYXllci4gSnVzdCByZW1lbWJlciB0aGF0IG9pbCAobm9ucG9sYXIpIGFuZCB3YXRlciAocG9sYXIpIGRvbiYjODIxNzt0IG1peC4=[Qq]
[f]Tm8uIENoYXJnZWQgbW9sZWN1bGVzIGNhbiYjODIxNzt0IHBhc3MgdGhyb3VnaCB0aGUgaHlkcm9waG9iaWMsIG5vbnBvbGFyIHBhcnQgb2YgdGhlIHBob3NwaG9saXBpZCBiaWxheWVyLg==[Qq]
[f]WWVzLiBOb25wb2xhciBtb2xlY3VsZXMgKGZhdHMsIG9pbHMsIHN0ZXJvaWQgaG9ybW9uZXMpIGNhbiBmcmVlbHkgcGFzcyB0aHJvdWdoIGEgcGhvc3Bob2xpcGlkIGJpbGF5ZXIu[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 1 is
[c]YWN0aXZlIHRyYW5zcG9ydA==[Qq]
[c]ZmFjaWxpdGF0ZWQgZGlmZnVzaW9u[Qq]
[c]c2ltcGxlIGRp ZmZ1c2lvbg==[Qq]
[f]Tm8uwqBJbiBhY3RpdmUgdHJhbnNwb3J0LCB0aGUgY2VsbCBtb3Zlc8KgbW9sZWN1bGVzIGZyb20gbG93ZXIgdG8gaGlnaGVyIGNvbmNlbnRyYXRpb24uIEluIG51bWJlciAxLMKgwqB0aGUgbW92ZW1lbnQgaXMgZnJvbSBoaWdoZXIgdG8gbG93ZXIu[Qq]
[f]Tm8uIEluIGZhY2lsaXRhdGVkIGRpZmZ1c2lvbiwgbWF0ZXJpYWxzIGFyZcKgYWxsb3dlZCB0byBkaWZmdXNlIGRvd24gdGhlaXIgY29uY2VudHJhdGlvbiBncmFkaWVudHMsIGJ1dCBhIHByb3RlaW4gY2hhbm5lbCBpcyBwcm92aWRlZCBmb3IgdGhlIG1hdGVyaWFscyB0byBwYXNzIHRocm91Z2guIFRoZXJlJiM4MjE3O3Mgbm8gY2hhbm5lbCBpbiBudW1iZXIgMS4=[Qq]
[f]WWVzLiBOdW1iZXIgMSBpcyBzaW1wbGUgZGlmZnVzaW9uIHRocm91Z2ggdGhlIHBob3NwaG9saXBpZCBiaWxheWVyLiBJbiBudW1iZXIgMywgdGhlIG1hdGVyaWFscyBhcmUgbm90IGdvaW5nIHRocm91Z2ggdGhlIHBob3NwaG9saXBpZCBiaWxheWVyLCBidXQgdGhyb3VnaCBhIGNhcnJpZXIgcHJvdGVpbi4=
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 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]YWN0aXZl[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 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]YWN0aXZl[Qq]
[c]dHJhbnNwb3J0[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]-[hangman] [hangman]
[c]cmVjZXB0b3I=[Qq]
[c]bWVkaWF0ZWQ=[Qq]
[c]ZW5kb2N5dG9zaXM=[Qq]
[q][hangman] are channels that allow water to diffuse through the cell membrane.
[c]YXF1YXBvcmlucw==[Qq]
[q]Na+, Cl, Ca++, Cl– or H+ can only pass through membranes through protein channels because they’re
[c]YmlnLg==[Qq]
[f]Tm8gKGJ1dCB0aGlzIGlzIGEgY29tbW9uIG1pc3VuZGVyc3RhbmRpbmcpLiBBbGwgb2YgdGhlc2UgaW9ucyBhcmUsIGNvbXBhcmVkIHRvIG9yZ2FuaWMgbW9sZWN1bGVzIG9yIGV2ZW4gdG8gbW9sZWN1bGVzIGxpa2Ugd2F0ZXIgb3IgY2FyYm9uIGRpb3hpZGUsIHZlcnkgc21hbGwuIEhlcmUmIzgyMTc7cyBhIGhpbnQ6IG5vdGljZSB0aGUgc3VwZXJzY3JpcHRzLg==[Qq]
[c]Y2hhcm dlZC4=[Qq]
[f]RmFudGFzdGljLiBUaGUgaHlkcm9waG9iaWMgbWlkZGxlIG9mIHRoZSBwaG9zcGhvbGlwaWQgYmlsYXllciByZXBlbHMgY2hhcmdlZCBwYXJ0aWNsZXMuIFRoZSBvbmx5IHdheSB0aGV5IGNhbiBwYXNzIHRocm91Z2ggdGhlIG1lbWJyYW5lIGlzIGJ5IGZhY2lsaXRhdGVkIGRpZmZ1c2lvbiB0aHJvdWdoIGEgcHJvdGVpbiBjaGFubmVsLg==[Qq]
[c]cG9sYXIu[Qq]
[f]Tm8sIGJ1dCB5b3UmIzgyMTc7cmUgb24gdGhlIHJpZ2h0IHRyYWNrLiBJbiB0ZXJtcyBvZiBlbGVjdHJvbmVnYXRpdml0eSwgd2hhdCYjODIxNztzIHRoZSBuZXh0IHN0ZXAgdXAgYWZ0ZXIgcG9sYXI/[Qq]
[x]
[restart]
[/qwiz]
What’s next?
Please proceed to this next tutorial: Osmosis and Water Potential