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Biology > B2.1 Membranes and Membrane Transport > Flashcards

B2.1 Membranes and Membrane Transport Flashcards

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1
Q

Cholesterol is a … (lipid ofc but which charge nature)

A

Amphipathic

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2
Q

Membranes are composed of …………., …………. cores and other (amphipathic/charged) lipids.

A

1) Hydrophobic
2) Non-polar
3) Amphipathic

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3
Q

Membranes are composed of a …………, ……….. exterior.

A

1) Hydrophilic
2) Polar

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4
Q

What type of lipids make up plasma membranes?

A

Phospholipids

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5
Q

Large molecules and hydrophilic particles do not pass easily between the hydrophobic core of the phospholipid bilayer, what does that do?

A

Gives membranes low permeability to these substances, allows them to function as effective barriers between the interior and exterior aqueous solutions.

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6
Q

Low permeability in membranes (form)….what does that do (function)?

A

Makes it possible to maintain differences in concentration across a membrane?

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7
Q

Large molecules such as protein, starch, glycogen, and cellulose, are an example of …… permeability.

A

Low

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8
Q

Polar molecules such as glucose or amino acids are an example of ………. permeability.

A

Low

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9
Q

Ions like Cl, Na, K, or P are an example of ….. permeability.

A

Low

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10
Q

Diffusion

A

The net movement of particles from a region of higher concentration to a region of lower concentration, without requiring energy (passive transport).

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11
Q

Why is diffusion passive?

A

Because it is a natural consequence of the continual random motion of particles in a liquid or gas.

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12
Q

Diffusion does not happen in…(which state of matter)

A

solid

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13
Q

Why can small non-polar molecules diffuse across membranes?

A

Because they can pass between phospholipid bilayers.

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14
Q

The rate of movements of molecules from on EE side of a membrane to another depends on….

A

concentration

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15
Q

The higher the concentration one side of a membrane, the….

A

more molecules move from that side to the other. side per unit time.

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16
Q

What of the direction of movement of molecules in a membrane with equal concentration of small, non-polar molecules on both sides?

A

Both directions

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17
Q

Do molecules with equal rates of movement have a net movement 🤌? If yes/no, why?

A

No, as they cancel out each other.

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18
Q

What are examples of small, non-polar molecules that are transported by simple diffusion?

A

O2 and CO2

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19
Q

Which type of protein structures are usually attached to the basic phospholipid bilayer?

A

Globular

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20
Q

Integral Proteins

A

Proteins that are embedded in the phospholipid bilayer.

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21
Q

Peripheral proteins

A

Proteins that are attached to the surface of the plasma membrane.

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22
Q

Function: two sides of plasma membranes have different functions.
Form?

A

Types of Protein are different in each side

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23
Q

Form: Integral Proteins’ hydrophobic surface
Advantage/function?

A

They are embedded in the bilayer’s hydrophobic hydrocarbon chains core.

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24
Q

How do particles dissolve in water (this lesson wise ya3ny)?

A

They form hydrogen bonds or other intermolecular interactions with water molecules.

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25
Q

What on membrane’s permeability to water?

A

Typically High

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26
Q

What on membranes’ permeability to most solutes?

A

Low

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27
Q

Osmosis

A

The passive movement of water molecules from a region of lower solute concentration to a region of higher solute concentration, across a semi-permeable membrane.

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28
Q

How can the osmosis net movement be explained?

A

Water is attracted to solutes naturally if.

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29
Q

Aquaporins

A

Transmembrane integral proteins with a pore through which only water can only pass through in either direction.

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30
Q

Is osmosis passive or active?

A

Passive

31
Q

Do Aquaporins use energy?

A

no

32
Q

Form: Aquaporins have a narrow part of the pore.
Function?

A

Acts a selectivity filter and prevents other particles such as protons, cl ions, from passing through.

33
Q

Ions like Cl or Na, or polar molecules like gluose pass……

A

at slow rates

34
Q

Facilitated Diffusion

A

The passive movement of particles across a membrane from a higher concentration to a lower concentration via channel proteins.

35
Q

Form: Channel protein’s pore’s narrowest diameter and charges of amino acids lining the pore.
Function/advantage:?

A

Channel proteins are specific to one substance or ion.
Ex: K channel proteins only allow K+ pass through.

36
Q

Active Transport

A

The movement of substances across membranes using energy from ATP.

37
Q

What the net movement of substances in active transport?

A

Against the concentration gradient, from lower to higher concentration.

38
Q

lol

A

Lol

39
Q

How does a particle/molecule enter/exit a cell through active transport?

A

Particle enters from one side of the membrane and binds to a site inside protein pump.
2) ATP causes the pump conformation to change.
3) Particle exits the membrane on the other side.
4) Pump conformation changes without energy.

40
Q

How does a particle/molecule enter/exit a cell through active transport?

A

Particle enters from one side of the membrane and binds to a site inside protein pump.
2) ATP causes the pump conformation to change.
3) Particle exits the membrane on the other side.
4) Pump conformation changes without energy.

41
Q

How is the plasma membrane semi-permeable in simple diffusion?

A

Only small, non-polar (hydrophobic) particles can enter/exit with concentration gradient.

42
Q

How is the membrane selectively permeable in facilitated diffusion?

A

Channel proteins are specific to one type of particle, cells control which particles enter by controlling the types of channels involved, pores of some channel proteins can be closed temporarily.

43
Q

How is the plasma membrane selectively permeable in active transport?

A
  • Pump proteins are specific to particular particles.
  • Pump proteins are asymmetrical to ensure that particles are moved in one direction.
  • Active transport can generate concentration gradients as particles move against them.
44
Q

Glycoproteins

A

Polypeptides with carbohydrate, usually a single sugar, attached.

45
Q

Glycolipids

A

Lipids with carbohydrate, usually a short chain of up to 4 glucose subunits, attached.

46
Q

How are glycoidks positioned in the plasma membrane?

A

The protein/lipid is embedded in the membrane and the hydrophilic carbohydrate part is projecting outwards.

47
Q

What is glyco-(biomolecules) role in cell adhesion?

A

Together they form a carbohydrate-rich layer (glycocalyxes) on the outer face of the plasma membrane of animal cells, the glycocalyxes of adjacent cells can fuse, binding them together and preventing the tissue from falling apart.

48
Q

What is glyco-(biomolecules) role in cell recognition?

A

Differences in types of glycoproteins/lipids within membranes allows cells to recognize other cells, this helps in the development of tissue and organs, and allows the immune system to recognize self and non-self cells.

49
Q

Fluid Mosaic

A

A two-dimensional array of many diverse and small protein subunits.

50
Q

Form: Saturated fatty acids have straight chains.
Property?

A

Allows phospholipids to pack together more tightly, which reduces the fluidity of a membrane and therefore its flexibility and permeability by simple diffusion.

51
Q

Form: Unsaturated fatty acids have one or more kinks in their hydrocarbon chain.
Property?

A

Allows phospholipids to pack together more loosely, making a membrane more flexible, fluid, and permeable.

52
Q

What makes the plasma membrane remain fluid but not too porous?

A

Relative amounts of saturated and unsaturated fatty acids are regulated so that membranes have the ideal properties depending on temperature conditions.
Ex: Antarctic water fish have more unsaturated fatty acids than from warmer waters.

53
Q

Percentage of cholesterol in eukaryote plasma membranes?

A

20%-40%

54
Q

Why are cell membranes called a liquid-ordered phase?

A

They do not correspond to one of the three states of matter, they are packed densely but are free to move laterally.

55
Q

How does cholesterol maintain membrane fluidity?

A

It helps maintain the arrangement of phospholipids at high temperatures so it remains. impermeable to hydrophilic particles like Na or H+, and ensures saturated fatty acid tails don’t solidify and prevents them from becoming stiff at low temperatures.

56
Q

What if a cell membrane is too viscous or inflexible?

A

It would restrict cell movement and make it more likely to burst.

57
Q

What’s the group at the end of a cholesterol molecule?

A

hydrophilic -OH group.

58
Q

Structure of a Vesicle?

A

Small, spherical sac of membrane with a droplet of fluid inside.

59
Q

Examples of intracellular movement using vesicles:

A
  • proteins synthesized by roughER ribos being carried to Golgi apparatus.
  • Proteins carried from golgi apparatus to membrane.
  • Phospholipids and cholesterol synthesized by smooth ER carried to membrane of a growing cell to increase S.A
60
Q

Endocytosis

A

The formation of a vesicle in the cytoplasm by pinching off a piece of plasma membrane.

61
Q

Examples of Endocytosis:

A
  • Feotal cells in the placenta absorb proteins from the mother’s blood.
  • Unicellulars like Amoeba/paramecium absorb large undigested particles.
  • Phagocytic white blood cells absorb pathogens including bacteria and viruses.
62
Q

Exocytosis

A

Fusion of a vesicle with the plasma membrane, expelling its content from the cell.

63
Q

Examples of Exocytosis:

A
  • Gland cells secreting protein
  • Neurons secreting neurotransmitters
  • Unicellular organisms loading excess water into vesicles to expel it.
64
Q

How does active transport take place in synaptic transmission?

A

Gated ion channels that open up for a fraction of a second to allow nerve impulses to pass through.

65
Q

What causes voltages across membranes?

A

Imbalances of negative and positive charges.

66
Q

What does a negative voltage indicate?

A

That the overall balance of charges inside the neuron is less positive than the outside.

67
Q

Outline the voltage changes that occur when a gated ion channel opens and closes:

A

1) Closed at -70 mV (More negative inside)
2) Open at +40 mV (more positive inside)
3) Globular protein ball attached by a polyp chain blocks the pore at +40 than is ejected at -70mV

68
Q

Nerve Impulse

A

A brief movement of Na+ then K+ ions across the membrane of a neuron.

69
Q

CAMS (Cell-to-cell adhesion molecules)

A

Integral membrane proteins that protrude outwards and link adjacent cells in animals.

70
Q

Nicotinic acetylcholine receptors

A

Used at synapses where acetylcholine is the neurotransmitter

71
Q

What happens to the proteins on the postsynaptic membrane with the binding of acetylcholine?

A

It opens when the bind and closes when their not. (I wrote this feeling like i want to throw up and cry)(u from the future: ma7adesh mohtam, love u!!!)

72
Q

Sodium-Glucose cotransporters

A

Membrane proteins that move Na+ and Glucose together into a cell.

73
Q

How does the transport of Na+ and Glucose via Na-Glucose cotransporters work? What do we refer to this as?

A
  • The Na concentration is lower inside so it moves down the CG and releases energy.
  • The energy drives glucose into the cell.
  • This is refered to as indirect active transport ?
74
Q

What are some examples of indirect active transport?

A
  • Reabsorption of glucose filtrate by cells in the wall of the PCTs in the kidney.
  • Absorption of glucose from digested foods by small intestine epithelium.

Biology (20 decks)

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