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(Biology 211) Cellular Biology > Chapter 5 - Structure And Function Of Plasma Membranes > Flashcards

Chapter 5 - Structure And Function Of Plasma Membranes Flashcards

1
Q

What are on plasma membranes that allow for cell to cell communication and connections?

A

Surface markers

-these allow for the immune system to determine self from non self for example autoimmune disease’s

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2
Q

How does the plasma membrane transmit information?

A

It allows proteins to transmit complex signals from extracellular input receivers to intracellular processing activators such as hormones and growth factors

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3
Q

What bad things can happen to plasma membranes if other pathogens take them over?

A

They can be hijacked or mutated leading to disease states

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4
Q

When was the plasma membrane (PM) identified? And when were the chemical components determined?

A

Identified in 1890s and determined its chemical components in 1915

-initially various theories proposed a sandwich like structure of proteins and lipids

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5
Q

Singer and Garth theorized what in 1972?

A

The fluid mosaic model

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6
Q

The fluid mosaic model states what?

A

The model is that of a semiliquid phospholipid bilayer with cholesterol, proteins, and carbohydrates floating in and around the bilayer

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7
Q

What are phospholipids composed of?

A

A phosphate head, a glycerol, and two fatty acid tails

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8
Q

What is in between the phospholipids in the PM that stabilize them?

A

Cholesterol

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9
Q

A typical human cell is composed of what percentage of the 3 main macromolecules? (By mass)

A

50 percent protein, 40 percent lipid, and 10 percent carbs (by mass)

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10
Q

Percentage of macromolecule makeup of cells can vary. Explain the differences between myelin sheaths of nerve tissue and the inner mitochondrial membrane

A

Myelin sheaths of nerve tissue is mostly lipids and some protein and even fewer carbs while the inner mitochondrial membrane is mostly proteins and some lipids with virtually no carbs

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11
Q

Where is the only place carbohydrates can be found on the PM and in what form?

A

They can only be found on the PMs external surface in the form of glycoproteins or glycolipids

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12
Q

The interactions between the nonpolar fatty acid tails interacting with one another and the polar phosphate head of phospholipids effectively seperates what?

A

The serious solution inside the cell (cytoplasm) from the cells exterior (interstitial fluid)

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13
Q

The polar heads of phospholipids can form what bonds with other molecules (especially water)?

A

Hydrogen bonds

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14
Q

Phospholipids are known to spontaneously form what shapes and structures?

A

Spheres and bilayers

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15
Q

What are integral proteins

A

Those that are embedded into the phospholipids Hydrophobic region

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16
Q

How many a-a do single pass integral proteins usually have?

A

20-25

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17
Q

Some integral proteins extend through both layers and some only one layer of the PM, those that are large can have up to how many protein segements?

A

12, which are extensively folded and embedded in the PM

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18
Q

Integral proteins have hydrophobic and hydrophilic regions where?

A

The hydrophobic region is at the center and mildly hydrophilic regions at their peripheries that contact the cytoplasm or the extracellular fluid

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19
Q

Pertaining to the secondary protein structure how many conformations can integral proteins have?

A

They can have one or more alpha helixes or multiple beta sheets

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20
Q

Where are peripheral proteins found?

A

Only on the PM’s exterior or interior surfaces and can be attached to the phospholipid bilayer or to integral proteins

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21
Q

What can peripheral proteins be? What types of proteins?

A

Enzymes, structural components, or receptors (often referred to as cell-specific proteins)

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22
Q

Where are carbohydrates found on the PM? And in what form?

A

Only on the PM’s outer surface and are either in the form of glycoproteins or glycolipids

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23
Q

The carbohydrate components can be straight or branched on the PM and are usually how many monosaccharides pollysaccharides?

A

2-60

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24
Q

The carbohydrate components on the PM are vital for what?

A

Cell recognition, which is especially important in immunity including allowing cells to differentiate self from non self

-viruses and other antigens are identified by these components of the PM on immune cells, viruses are experts at changing their glycolipid and glycoprotein surfaces

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25
Q

What is the term used to describe the PM’s carbohydrate components?

A

Glycocalyx

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26
Q

The glycocalyx has to do what with polarity and what?

A

It is highly hydrophilic (polar) attracting water to these cells outer surfaces

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27
Q

Describe the plasma membrane’s fluidity and how it withstands punctures?

A

The lipid and protein components of the PM float in the bilayer however the PM is rather rigid, and has the property of allowing a very fine needle to penetrate it and withdraw without bursting the cell

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28
Q

How does the fatty acids chemical composition on the phospholipid tails make the plasma membrane more rigid?

A

The fatty acid risks are fully saturated and therefore are very straight and rigid, if they were unsaturated it would contain double bonds which would bend the fatty acids and have less rigidity

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29
Q

Some species have cells with more unsaturated fatty acids, this allows them to live in environments that are what?

A

Cold, helps them to remain flexible in cold temeratures

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30
Q

Plasma membranes have what type of permeability?

A

They are selectively permeable

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31
Q

Most plasma membrane transport is what type?

A

Passive transport

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32
Q

How do materials move through a concentration gradient?

A

ALWAYS down a concentration gradient (under normal conditions)

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33
Q

What is the main difference between passive and active transport?

A

Passive transport requires no energy (ATP) while active transport does not

E.g. for active transport is the sodium potassium pump

-most of a cells energy is used in this process

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34
Q

In terms of polarity what passes through the PM easily? And what does not?

A

Non-polar and lipid soluble materials with low molecular weight can pass through the bilayers hydrophobic core easily, polar substances cannot pass through the PM’s lipid core

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35
Q

What types of vitamins, drugs, molecules, and common molecules can pass right through the PM? List a few

A

Vitamins A,D,E,K along with fat soluble drugs, hormones, oxygen, and carbon dioxide all pass through the PM by simple diffusion

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36
Q

Even though polar substances do not pass through the PM’s lipid core it connects easily to what?

A

The cells exterior

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37
Q

What types of molecules and atoms cannot pass through the lipid core?

A

Ions, along with sugars and amino acids

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38
Q

Instead what do these ions, sugars, and amino acids need to get into the PM?

A

They need help from protein channels to get through

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39
Q

What type of process is diffusion in terms of energy?

A

A passive process, expends no energy

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40
Q

In diffusion how do substances move in the gradient?

A

It moves from high to low concentration (down a concentration gradient)

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41
Q

What type of energy are concentration gradients? When is the concentration gradient eliminated?

A

Potential energy, it is eliminated when it reaches equilibrium

42
Q

Is a concentration gradient just in PM’s?

A

No it is everywhere, for example air or in aqueous solutions

-in aqueous solutions substances will diffuse according to their own concentration gradients

43
Q

Moleculed always move in a random manner, List all the main factors that affect diffusion

A

-The extent of the concentration gradient (how strong it is)

-heavier molecules diffuse more slowly down a concentration gradient

-increased temperature increases the rate of diffusion

-Increased solvent density decrease rate of diffusion

-Lipid solubility, lipid soluble molecules move easily and quickly through the PM

-the greater the distance the molecules must diffuse the rate of diffusion slows (why cells are so small)

44
Q

Molecules move into available space until it is evenly distributed, what is this state called?

A

Dynamic equilibrium, as it gets closer to this state the rate of diffusion will slow

45
Q

Materials diffuse more slowly through cytoplasm than through more watery solutions, what can dehydration cause cellularly ?

A

Dehydration leads to loss of cell function because molecules take too long to get to where they need to go (dysfunction)

46
Q

What is filtration?

A

A form of diffusion through a membrane

47
Q

How does pressure play a role in diffusion?

A

Pressure enhanced diffusion through a membrane, important where blood pressure facilitates the movement of solutes through cells in the capillaries and in the kidneys

48
Q

What is facilitated transport?

A

A diffusion with the help of proteins in the PM

49
Q

What does facilitates transport need? How much energy is needed in this process?

A

There must be a concentration gradient for this to occur, no energy is expended in this process

50
Q

Are materials that are transported in facilitated diffusion polar or nonpolar?

A

Polar

51
Q

How does the process of facilitated transport work? What 2 ways can it work?

A

Materials interact with receptors in the PM’s surface then are passed to specific integral proteins which can be channels through the Phospholipid bilayer or are carriers which bind to the substance aiding its pass through the PM

52
Q

Integral proteins are called what?

A

Called transport proteins, and are channels or carriers which are both transmembrane proteins

53
Q

Channel proteins openings are composed of what domains?

A

Hydrophilic domains providing a hydrated opening through the PM’s layers

54
Q

Are channel proteins always open?

A

It depends, channel proteins can be open at all times, or they can be gated; for example sodium and potassium are always open in some cells and gated in others

55
Q

Gated channels can be controlled by what?

A

Electrical impulses or certain molecules (Ligands), which differ in the interior and the exterior side of the PM

Ex.) nerve and muscle cells

56
Q

Carrier proteins do what?

A

These integral transmembrane proteins bind to the molecules being transported and the shape of the carrier changes to push it into the cell

57
Q

The number of carrier proteins is often limited, what does this mean when comparing it to channels?

A

They are a lot slower because they have a transport maximum

-this occurs in the kidney tubules where glucose reaches its transport maximum if too much glucose enters the tubules as seen in diabetics

58
Q

What is osmosis?

A

The movement of water through a selectively permeable membrane down the waters concentration gradient

(Water moves from high water concentration to low water concentration)

59
Q

In osmosis other than water what can pass through the membrane?

A

Nothing, only water can

60
Q

In osmosis what is the relationship between where solutes are and water and how it flows in the concentration gradient?

A

Water moves through aquaporins from lower solute concentration (high water concentration) to through the membrane to high solute concentration (low water concentration)

61
Q

What type of pressure can stop the flow of water in osmosis before the concentration gradient is gone?

A

Hydrostatic pressure, which is water pressure

62
Q

What type of pressure can stop the flow of water in osmosis before the concentration gradient has reached equilibrium?

A

Hydrostatic pressure, which is water pressure

63
Q

What is tonicity?

A

It’s how the extracellular solution changed the volume of a cell due to osmosis

64
Q

What is osmolarity and what does it effect?

A

The measure of solute
concentration which affects tonicity

65
Q

High vs low osmolarity what does it contain water and solutes wise?

A

Low osmolarity has low solutes and high water while high osmolarity has high solutes low water

66
Q

Water always moves what way in osmolarity?

A

Low osmolarity to high osmolarity

67
Q

What way does water move in cells that are in a hypotonic solution?

A

Move into cells

68
Q

Water will flow down its concentration gradient from more water concentration outside of the cell to less water concentration inside the cell for that in a hypotonic solution. What happens inside the cell?

A

The cell will build with pressure as water moves in and increases the volume of the cell

69
Q

Cells in a hypertonic solution will have water move where?

A

Out of the cell

Opposite of hypotonic, effects will be loss of volume and pressure

70
Q

In terms of tonicity what state is ideal for cells? And describe it

A

Isotonic, its osmolarity is the same on the inside and outside of cell

-there is no net movement of water

71
Q

If hypertonic or hypotonic conditions persist in cells what can happen? For example describe the RBC example for both those conditions

A

Cell function will be compromised and the cells may be destroyed

-in the sample of red blood cells they will burst (lyse) under hypotonic conditions, in hypertonic conditions it will shrink (crenate) which also leads to cell death

72
Q

How come plants, fungi, bacteria, and some protists are able to prevent lysis in a hypotonic solution?

A

Because they have a rigid cell wall that maintains its shape

73
Q

What type of environment is freshwater? In terms of tonicity.

A

Hypotonic environment

74
Q

Plant cells are always slightly what in terms of tonicity?

A

Hypertonic

75
Q

What happens to plant cells under low water conditions?

A

Water will leave the cell as the ECF becomes hypertonic, this causes the plasma membrane to detach form the cell wall (plasmolysis) and causes the plant to wilt

76
Q

Most marine invertebrates are what in terms of tonicity towards their environment?

A

Isotonic

77
Q

What type of tonic environment do freshwater fish live in and what does this mean for water intake?

A

They live in a hypotonic environment, therefore they do not need to drink water and must excrete a lot of dilute urine to rid themselves of excess water

(Water comes in naturally)

78
Q

Marine fish live in a what type of environment and what does that mean for water retention?

A

They live in hypertonic environments and must drink water to prevent dehydration via osmosis therefore they excrete little urine that is very concentrated

79
Q

How do protistsa such as paramecium and amoeba expel water that enters via osmosis? What type of environment do they live in?

A

By contractile vacuoles

-live in hypotonic environments

80
Q

How do vertebrates morgue and monitor blood osmolarity?

A

Kidneys osmoregulage and the brain (hypothalamus) monitors blood osmolarity and releases a hormone (ADH) that slows water loss via the urine

81
Q

Most animal blood has high albumen concentrations which does what? Where is albumen made?

A

Made in the liver and controls blood cell and tissue osmotic pressure

82
Q

What type of transport requires energy expenditure?

A

Active transport

83
Q

What does a substance do that requires energy in active transport?

A

It moves against its concentration gradient

84
Q

Primary active transport results in what?

A

The interior of cells being high in potassium ions and the outside of the PM having a high concentration of sodium ions

85
Q

Potassium ions move through channels that are always open and bring what do the interior surface of the PM? What does this cause?

A

They bring negatively charged proteins to the interior surface of the PM, this results in a negatively charged interior surface while the outer surface of the PM is positvely charged
(Electrochemical gradient)
-proteins accumulate in the cytoplasm due to this

86
Q

Active transport mechanisms are also called…

A

Pumps

87
Q

What do pumps work to do?

A

Push molecules against their concentration gradient

-cells expend considerable amounts of energy on this

88
Q

What are the three types of protein lumps that facilitate movement across the PM?

A

1) Uniporter proteins - carry one specific ion or molecule e.g. hydrogen ATPase

2) Symporter proteins - carry two different ions or molecules across the PM in the same direction e.g. glucose/sodium protein carriers

3) Antiporter proteins - carry two different ions but in opposite directions e.g. potassium/sodium ATPase

89
Q

Do the three carrier proteins for active transport need energy?

A

It depends, some do some don’t

90
Q

What is primary active transport also called?

A

The sodium-potassium pump (sodium/potassium ATPase)

91
Q

The active transport of sodium and potassium ions allows for secondary active transport and the establishment of what?

A

The electrochemical gradient

-glucose movement and nerve and muscle impulses run on this along with many other examples in your body

92
Q

The sodium-potassium ATPase is what type of carrier protein?

A

Antiporter

93
Q

Go through the entire process of the sodium-potassium ATPase and how it works, be specific

A

1) the enzyme opens to the inside and binds to three sodium ions
2) ATP is hydrolyzed (energy used)
3) the enzyme changes shape and opens to the interior, its affinity for sodium decreases and the sodium is released to the outside
4) the enzyme now has a greater affinity for potassium ions and two of them attach to the enzyme and ADP detached from the enzyme
5) the enzyme repositions itself opening the cells interior
6) the enzyme (carrier protein) now has decreased affinity for potassium and the two ions move into the cytoplasm

94
Q

What does sodium-potassium ATPase result in?

A

More sodium on the outside surface and more potassium on the inside surface of the PM

95
Q

What type of pump is the sodium-potassium pump?

A

An electrogenic pump

96
Q

What does the secondary active transport mechanism do?

A

Uses the sodium concentration gradient to symport sodium and other molecules into cells

-amino acids and glucose enter cells this way too

97
Q

What is endocytosis and how does it work?

A

The process of having something enter a cell
-it works by having the cells PM invaginate forming a pocket around the cell or particles it wants to take in, the pocket pinches off and now contains the cell or particle in a vacuole or vesicle

98
Q

How does phagocytosis work? Explain the macrophage for example (WBC)

A

It takes in large particles for example WBC’s engulf a microbe, Calthrin is a protein that helps attach the microbe to the membrane, the newly formed compartment is called a endoscope and can not merge with a lysosome for digestion

99
Q

What is pinocytosis?

A

The intake of aqueous solutions and the resulting vesicles are much smaller than in phagocytosis

100
Q

Other calthrin-like receptors are found in some specific binding in certain cells called what? For example how does it work in the process of removing LDL’s, what happens when they are not there for this case?

A

Called receptor-mediated endocytosis for example in removing LDL’s from the blood for use in cells but can results in hypercholesterolemia if they are missing

101
Q

What is exocytosis?

A

The process of expelling material from a cell

-waste materials are expelled this way as well as neurotransmitters in the synaptic cleft of nerve and muscle cells

(Biology 211) Cellular Biology (12 decks)

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