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BIOL 1000 > Membranes and Transport > Flashcards

Membranes and Transport Flashcards

1
Q

What are the functions of the plasma membrane?

A
  1. Barrier to polar molecules, charged molecules, and large molecules
  2. Maintains ion gradients
  3. Involved in signaling
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2
Q

How many layers is the plasma membrane made up of?

A

One phospholipid bilayer

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3
Q

The plasma membrane is amphipathic, what does that mean?

A

Consists of hydrophilic and hydrophobic parts

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4
Q

What is the general structure of a phospholipid?

A

Polar head (glycerol and phosphate)

Non polar tail (fatty acid tails)

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5
Q

What is meant by the asymmetry of membranes? Why is this important?

A

The types of phospholipids differ between the two mono layers

Different phospholipids do different jobs

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6
Q

Name 3 characteristics of membranes?

A

Flexible (change shape)

Repairable (move to reform continuous surface)

Expandable (increases surface area by adding new lipids)

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7
Q

Why is the membrane able to repair, expand, and change shape?

A

Membrane fluidity

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8
Q

How do phospholipids typically move?

A

Constant lateral motion but rarely flip to other side of bilayer

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9
Q

What are some factors that affect membrane fluidity?

A

Ratio of unsaturated vs saturated fatty acids

Chain length of fatty acid tails

Temperature

Cholesterol

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10
Q

What is the difference between saturated and unsaturated fatty acid tails?

A

Saturated are a straight chain with no double bonds

Unsaturated have double bonds which causes a bend

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11
Q

A higher amount of unsaturated fatty acids means?

A

The double bond pushes other phospholipids away making it is less packed and therefore more fluid and permeable

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12
Q

A higher amount of saturated fatty acids means?

A

The phospholipids can pack closely and it’s less fluid and permeable

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13
Q

Something with a higher ratio of unsaturated fats would be what at room temperature?

A

Liquid

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14
Q

Will a bilayer with short and unsaturated tails be more fluid at a higher temperature than a bilayer with long and saturated hydrocarbon tails? Why?

A

Yes

Molecules are already spaced out and the heat will cause them to space out more

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15
Q

Will a bilayer with short and unsaturated tails solidify before a bilayer with long and saturated tails?

A

No

Already closely packed molecules will get closer

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16
Q

If the fatty acid tails are longer than the membrane is? Why?

A

Less fluid

Link together and restrict movement

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17
Q

Why is cholesterol important?

A

Maintains fluidity/permeability at lower and higher temperatures

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18
Q

How does cholesterol help maintain fluidity?

A

At lower temperatures by reducing the packing opportunities

At higher temperatures by acting as a buffer to prevent them from separating too much

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19
Q

What does the mosaic part of the fluid mosaic model mean?

A

Membranes contain many different proteins, carbohydrates, and lipids

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20
Q

What can and cannot diffuse through the membrane?

A

Ions, large molecules, and polar molecules can’t

Small non polar molecule can

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21
Q

What are the types of transport across the membrane?

A

Passive simple diffusion
Passive facilitated difffusion
Osmosis
Active transport

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22
Q

What is simple diffusion? What uses it?

A

Movement of substances from high to low concentrations (increases entropy)

Spontaneous

No transporter or energy required

Small non polar molecules

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23
Q

What is passive facilitated diffusion?

A

Movement from high to low concentration that doesn’t require energy but requires transport protein

24
Q

What types of proteins help with facilitated diffusion?

A

Integral/transmembrane protein

Peripheral protein

25
Q

What are some functions of membrane proteins?

A

Transport

Enzyme activity

Signal transduction

Cell recognition

26
Q

What are integral/transmembrane proteins?

A

Integral are inserted into membrane and are amphipathic, difficult to remove

Transmembrane proteins are the most common integral proteins are they cross the entire membrane once or multiple times

27
Q

Where do the hydrophilic/hydrophobic parts of transmembrane proteins go?

A

Hydrophobic are embedded in the membrane

Hydrophilic are inside or outside the cell

28
Q

What are peripheral proteins?

A

Attached to one hydrophilic side and don’t interact with hydrophobic core

Primarily found on intracellular (cytosolic) side

Attach via non covalent bonds (easy to detach)

29
Q

What are some major proteins involved in facilitated diffusion?

A

Hydrophilic channel proteins

Gated channels

Carrier proteins

30
Q

What are channel proteins? What does the rate of diffusion depend on?

A

Always open (don’t change shape)

Provide easier route across membrane for a specific molecule

Concentration gradient (stronger gradient means faster diffusion) and number of channel proteins (more channels means faster movement)

31
Q

What are gated channels? What does the rate of diffusion depend on?

A

Only open via stimulus (molecules bind to protein which causes shape change to open protein)

Whether it’s open or closed, concentration gradient, number of gated channels

32
Q

What are carrier proteins?

A

Transport specific molecules across the membrane

Molecule attaches to binding site, causes shape change, transporter opens to other side

33
Q

What are lipids?

A

carbon-containing compounds that are nonpolar and hydrophobic

34
Q

What are the three naturally occurring fatty acids in our food?

A

polyunsaturated fatty acids
monounsaturated fatty acids
saturated fatty acids

35
Q

What are steroids?

A

family of lipids that have a four-ring structure ex. estrogen, cholesterol, testosterone

36
Q

What are fats?

A

nonpolar molecules composed of three fatty acids linked to a glycerol (triglycerides/triglycerols)

37
Q

How is glycerol and fatty acids linked?

A

ester linkage

38
Q

What are phospholipids?

A

glycerol that is linked to phosphate and two fatty acid chains

38
Q

What are phospholipids?

A

glycerol that is linked to phosphate and two fatty acid chains

39
Q

What is a lipid micelle?

A

tiny cluster created when the hydrophilic heads of a set of lipids face the water and form hydrogen bonds and the hydrophobic tails interact with each other

40
Q

What is a lipid bilayer?

A

lipid molecules align in paired sheets where the hydrophilic heads face the surrounding and the hydrophobic tails interact with each other

41
Q

What lipids form micelles vs bilayers?

A

micelles: fatty acids or other single amphipathic lipids with single hydrocarbon chains

bilayer: phospholipids which have bulkier two-hydrocarbon tails

42
Q

What does selective permeability mean?

A

some substances cross a membrane easier than others

43
Q

What happens when equilibrium is reached during diffusion?

A

solutes continue to move but at equal rates

44
Q

What is a hypertonic solution? What happens to a vesicle?

A

solution outside the membrane has a higher concentration of solutes than the interior, water will move out of the vesicle causing the vesicle to shrink and the membrane to shrivel

45
Q

What is a hypotonic solution? What happens to a vesicle?

A

solution outside the membrane has a lower concentration of solutes than the interior, water will move into the vesicle causing it to swell or burst

46
Q

What is an isotonic solution? What happens to a vesicle?

A

solute concentrations are equal inside and outside the membrane, does not affect the membranes shape

47
Q

Can proteins be amphipathic? How?

A

yes

amino acids have side chains that can be either nonpolar, polar, or charged

48
Q

What is aquaporin?

A

channel proteins that allow water to cross but nothing else, water can pass without aquaporin but its 10 times faster

49
Q

Which are faster, channel proteins or carrier proteins? Why do they use these then if they are slower?

A

channel proteins because they don’t have to change shape

use carrier proteins b/c of the need for specificity (can transport large molecules and be specific)

50
Q

What is transport against a concentration called?

A

active transport

51
Q

How can transport proteins use ATP?

A

channel proteins can be gated by ATP

pumps are powered by ATP

52
Q

What is a coupled transporter?

A

transmembrane carrier protein that facilitates diffusion of an ion down its gradient and uses the energy from that process to transport some other substance

53
Q

What is a cotransporter/symporter?

A

cotransport protein that allows an ion to diffuse down its gradient, using the energy of that transport a different substance in the same direction against its concentration gradient

54
Q

What is an antiporter?

A

cotransport protein that allows an ion to diffuse down its gradient, using the energy of that transport a different substance in the opposite direction against its concentration gradient

BIOL 1000 (12 decks)

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