Cell membrane

Question 1

Peripheral or extrinsic proteins

Answer 1

proteins that only occur on the outside of the phospholipid bilayer. They do not extend through the membrane. An example is a blood cell using a peripheral protein to connect to the outside tissues to hold it in place

Question 2

Integral or intrinsic proteins

Answer 2

Proteins that go all the way through the membrane, having areas that associate with the hydrophobic end. They can be separated put into four categorized: transport, receptor, marker, and attachment. These proteins act as channels

Question 3

What is important about the hydrophobic region of the phospholipid membrane?

Answer 3

It is selectively permeable for large, charged, and hydrophilic particles/molecules. Hydrophobic particles can get through more easily

Question 4

Simple diffusion

Answer 4

unassisted passage of small, hydrophobic, non-polar molecules from regions of higher concentrations to regions of lower concentrations.

Question 5

What about small molecules? Can they get through?

Answer 5

Yes they can! Even if they are hydrophilic, they can slip between the gaps of the hydrophobic regions and get into the cells like molecules of oxygen. Ants can crawl through a wall in your house because they’re tiny. This is simple diffusion

Question 6

Membrane permeability anaology

Answer 6

different types of passageways exist to get into a cell just like different types of passageways exist to get into your home. For a friend to come into your house, you have to open the door. For a package to come into your house you have to open the door and expend energy to pick it up and carry it in. For a fly to get into your home the window just has to be open.

Question 7

Facilitated diffusion

Answer 7

Is passive transport that uses integral membrane proteins to transport larger, charged, hydrophilic, and polar particles across the concentration gradient. No energy required, still going with concentration gradient high to low

Question 8

Diffusion equilibrium

Answer 8

state where the molecules inside equals the molecules outside, evenly distributed like food dye in water. Once4 an equilibrium has been reached, there will no longer be movement across the membrane

Question 9

What are factors that affect the rate of diffusion? (7)

Answer 9

• Concentration gradient: the bigger the difference, the faster they’ll move
• Temperature: particles are moving faster
• Size of molecules: smaller molecules move faster and collide less
• Viscosity of medium
• Membrane permeability
• Surface area: more surface area means more diffusion. Your lungs have 753 square feet of surface area to diffuse gasses on!
• Distance: square of the distance, diffusion is very slow over long distances

Question 10

What are the two types of proteins for facilitated diffusion?

Answer 10

carrier proteins and channel proteins. Proteins are ‘facilitating’ or helping large particles pass. Ions, glucose, and water require this kind of passive transport

Question 11

Channel proteins

Answer 11

fluid filled tubes that allow only certain things through them like K+. They also have gates on them that only allow these things through at a specific time. Gates include voltage, ligand, and mechanically activated gates or electric signal (concentration of ions changes), chemical signal, or mechanical deformation. Leak channels are also a thing and they contribute to resting membrane potential

Question 12

Carrier proteins

Answer 12

Do no open to both the outside and inside, they are the revolving doors. Binds to a solute which causes it to change shapes. Can be very specific in the solute that they transport. They have a maximum rate of transport and can become saturated.

Question 13

Primary active transport

Answer 13

Uses a carrier protein much like facilitated diffusion only it has an intracellular receptor for ATP so that the molecule can be transported over a higher concentration gradient. Can move one or multiple ions ‘against the grain’ at once. Sodium potassium pump is example.

Question 14

Secondary active transport

Answer 14

like primary active transport only ATP is not directly involved. Uses instead the energy stored in the concentration gradient to move solutes across. Usually uses sodium that has been pumped out of the cell by the primary active transport and is now in higher concentrations, to move to an area of lower concentration along with a solute

Question 15

Bulk transport

Answer 15

when things larger than an ion or molecule needs to be transported over the membrane like when a macrophage engulf a bacteria, this is still active transport that requires ATP

Question 16

Endocytosis

Answer 16

Bulk transport of material INTO cell. Phagocytosis or cell eating is one type which uses a pseudopodia to reach out and grab pathogen. A phagosome is created which then fuses with a lysosome.

• Another type of endocytosis is pinocytosis which is cell drinking. Occurs in most of the cells in our body, the cell creates a pocket of fluid and engulfs anything that may be in it. Intestine and kidney cells use this though its nonspecific, it lets large amounts of a substance in.
• Receptor mediated endocytosis is a more specific mechanism to bring in large quantities of a substance. Requires specific receptors

Question 17

Exocytosis

Answer 17

Cells transporting things OUT of cell. This is how beta cells of the pancreas secrete insulin to the external environment. Secretory vesicles migrate to the plasma membrane, fuse with it, and release the contents of the vesicle outside. Calcium is what is usually used in this process, gated calcium channels

Question 18

Osmosis

Answer 18

passive transport of water through a membrane. In order for osmosis to occur, the membrane must be semi permeable, it has to allow the water molecules through but not the solutes.

Question 19

Osmotic pressure

Answer 19

the pressure that is built up in a closed container because of water moving across a membrane over a concentration gradient.

Question 20

Osmolarity

Answer 20

the moles of PARTICLES per liter. Isosmotic means same concentration as, hypersmotic means more concentrated than, and hyposomtic means less concentrated than.

Question 21

Tonicity

Answer 21

How concentrations affect the body. It means how the solution affects the firmness of the cell membrane. Cells always want to be in an isotonic solution and so they try to even things out either by movement of ions through a permeable membrane of through movement of water through an impermeable membrane.
-The deformation that occurs when water goes in or out of a cell an effect of tonicity