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Bio 5A Lecture > Chapter 7: Membrane Structure And Function > Flashcards

Chapter 7: Membrane Structure And Function Flashcards

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1
Q

Define Selective Permeability

A

A property of biological membranes that allows them to regulate the passage of substances across them.

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2
Q

What is the most abundant lipid in most membranes?

A

Phospholipids

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3
Q

Define Amphipathic

A

Having both a hydrophobic and hydrophilic region.

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4
Q

Define Fluid Mosaic Model

A

The currently accepted model of cell membrane structure, which envisions the membrane as a mosaic of protein molecules drifting laterally in a fluid layer of phospholipids.

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5
Q

What is a membrane primarily held together by?

A

Hydrophobic Interactions

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6
Q

Are hydrophobic interactions stronger or weaker than covalent bonds?

A

Weaker

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7
Q

The temperature at which a membrane solidifies depends on the _____it is made of.

A

Type of Lipids

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8
Q

Membranes are _____ static sheets of molecules locked rigidly in place.

A

Not

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9
Q

What is meant by the fluidity of membranes?

A

Membranes are not static sheets of molecules locked rigidly in place.

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10
Q

What happens with the lipids and proteins in membranes?

A

Most of the lipids and some proteins can shift about sideways- that is, in the plane of the membrane. The sideways movement of phospholipids within the membrane is rapid.

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11
Q

What happens to the fluidity of the membrane with the decrease of temperature?

A

The fluidity of the membrane decreases.

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12
Q

Under what conditions does a membrane continue to keep its fluidity with increasingly lower temperature?

A

As the temperature decreases, the membrane remains fluid to a lower temperature if it is rich with phospholipids with unsaturated carbon tails.

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13
Q

How does Cholesterol affect the fluidity of a membrane at high temperatures?

A

Cholesterol makes the membrane less fluid by restraining phospholipid movement. However, because cholesterol also hinders the close packing of phospholipids, it lowers the temperature required for the membrane to solidify. Thus, cholesterol can be thought of as a fluidity buffer.

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14
Q

Compared to animals, plants have very _____ levels of cholesterol.

A

Low

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15
Q

What does the fluidity of a membrane affect?

A

It affects both its permeability and the ability of membrane proteins to move to where the function is needed.

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16
Q

Are membranes that are extremely fluid optimal for life?

A

No

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17
Q

In what way can a membrane be regarded?

A

A collage of different proteins, often clustered together in groups, embedded in the fluid matrix of the lipid bilayer.

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18
Q

_____ form the main fabric of membrane, but _____ determine most of the membrane’s functions.

A

Phospholipids-Proteins

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19
Q

What are the different types of membrane proteins?

A

Integral-Peripheral. IP

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20
Q

Define Integral Proteins

A

A transmembrane protein with hydrophobic regions that extend into and often completely span the hydrophobic interior of the membrane and with hydrophilic regions in contact with the aqueous solution on one or both sides of the membrane (or the lining channel in the case of a channel protein)

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21
Q

Define Peripheral Proteins

A

A protein loosely bound to the surface of a membrane or to part of an integral protein and not embedded in the lipid bilayer.

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22
Q

What are some functions of membrane proteins?

A

Transport-Enzymatic Activity-Signal Transduction-Cell-Cell Recognition-Intercellular Joining-Attachment to the Cytoskeleton and Extracellular Matrix (ECM). TES-CIE

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23
Q

What does the CD4 protein do?

A

A protein called CD4 on the surface of immune cells helps the HIV infect these cells, leading to AIDS.

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24
Q

Why is cell-cell recognition important?

A

It’s important, for instance, in the sorting of cells into tissues and organs in an animal embryo; furthermore, it is the basis for the rejection of foreign cells by the immune system.

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25
Q

How do cells recognize other cells?

A

By binding to molecules, often containing carbs, on the extracellular surface of the plasma membrane.

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26
Q

Define Glycolipids

A

A lipid with one or more covalently attached carbohydrates.

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27
Q

Define Glycoproteins

A

A protein with one or more covalently attached carbs.

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28
Q

Are membrane carbs primarily bonded to glycolipids or glycoproteins?

A

Glycoproteins

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29
Q

How is the asymmetric arrangement of proteins, lipids, and their associated carbs in the plasma determined?

A

It is determined as the membrane is being built by the endoplasmic reticulum and the Golgi apparatus.

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30
Q

What is the usual movement around membranes?

A

A steady traffic of small molecules and ions move across the plasma membrane in both directions. Sugars, amino acids, and other nutrients enter the cell, and metabolic waste products leave out. The cell takes in O2 for use in cellular respiration and expels CO2. Also, the cell regulates its concentrations of inorganic ions, such as Na, K, Ca, and Cl, by shuttling them one way or the other across the plasma membrane.

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31
Q

Can non-polar molecules dissolve in the lipid bilayer?

A

Yes, and they can cross it easily, without the aid of membrane proteins.

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32
Q

Do polar molecules cross the lipid bilayer quickly?

A

No

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33
Q

Define Transport Proteins

A

A transmembrane protein that helps a certain substance or class of closely related substances to cross the membrane.

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34
Q

What are a subdivision of transport proteins? Define them.

A

Channel Proteins, function in by having a hydrophilic channel that certain molecules or atomic ions use as a tunnel through the membrane.

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35
Q

Define Aquaporins

A

A channel protein in a cellular membrane that specifically facilitates osmosis, the diffusion of free water across the membrane.

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36
Q

Define Carrier Proteins

A

One type of transport proteins. They hold onto their passengers and change shape in a way that shuttles them across the membrane.

37
Q

_____ is diffusion of a substance across a membrane with no energy investment

A

Passive Transport

38
Q

Define Diffusion

A

The random thermal motion of particles of liquids, gases, or solids. In the presence of a concentration or electrochemical gradient, diffusion results in the net movement of a substance from a region where it is more concentrated to a region where it is less concentrated.

39
Q

Define Concentration Gradient

A

A region along which the density of a chemical substance increases or decreases.

40
Q

Each substance diffuses down its _____ concentration gradient.

A

Own

41
Q

Much of the traffic across cell membranes occurs by _____.

A

Diffusion

42
Q

Define Passive Transport

A

The diffusion of a substance across a biological membrane with no expenditure of energy.

43
Q

What does higher free water concentration mean?

A

Lower solute concentration.

44
Q

Define Osmosis

A

The diffusion of free water across a selectively permeable membrane.

45
Q

What must be considered when analyzing a behavior of a cell?

A

Solute Concentration and Membrane Permeability

46
Q

Define Tonicity

A

The ability of a solution surrounding a cell to cause that cell to gain or lose water.

47
Q

Define Isotonic

A

Referring to a solution that, when surrounding a cell, causes no net movement of water into or out of the cell. Water diffuses across the membrane, but at the same rate in both directions.

48
Q

Define Hypertonic

A

Referring to a solution that, when surrounding a cell, will cause the cell to lose water. HYPER-L

49
Q

Define Hypotonic

A

Referring to a solution that, when surrounding a cell, will cause the cell to take up water.

50
Q

In which type of situation does an animal cell fare best in?

A

Isotonic Environment

51
Q

In which situation does a plant cell best thrive in?

A

Plant cell are turgid (firm) and generally healthiest in a hypotonic environment, where the uptake of water is eventually balanced by the wall pushing back on the cell.

52
Q

Define Osmoregulation

A

Regulations of solute concentrations and water balance by a cell or organism.

53
Q

Define Turgid

A

Swollen or distended, as in plant cells. (A walled cell becomes turgid if it has a lower water potential than its surroundings, resulting in entry of water).

54
Q

Define Flaccid

A

Limp. Lacking turgor (stiffness or firmness), as in a plant cell surroundings where there is a tendency for water to leave the cell. (A walled cell becomes flaccid if it has a higher water potential than its surroundings, resulting in the loss of water). FL (Flaccid-Leave the Cell)

55
Q

In what situation is a cell wall not advantageous whatsoever?

A

If the cell is immersed in a hypertonic environment. In this case, a plant cell, like an animal cell, will lose water to its surroundings and shrink.

56
Q

Define Plasmolysis

A

A phenomenon in walled cells in which the cytoplasm shrivels and the plasma membrane pulls away from the cell wall; occurs when the cell loses water to a hypertonic environment.

57
Q

Define Facilitated Diffusion

A

The passage of molecules or ions down their electrochemical gradient across a biological membrane with the assistance of specific transmembrane transport proteins, requiring no energy expenditure.

58
Q

What are the two types of transport proteins?

A

Carrier Proteins and Channel Proteins.

59
Q

What type of transport protein is a Aquaporin?

A

Channel Protein

60
Q

Define Ion Channels

A

A transmembrane protein channel that allows a specific ion to diffuse across the membrane down its concentration or electrochemical gradient.

61
Q

Define Gated Channels

A

A transmembrane protein channel that opens or closes in response to particular stimulus.

62
Q

In which type of transport protein does a shape change happen?

A

Carrier Proteins

63
Q

_____ uses energy to move solutes agains their gradients.

A

Active Transport

64
Q

Is facilitated diffusion a type of active or passive transport?

A

Passive (FP)

65
Q

Define Active Transport

A

The movement of a substance across a cell membrane against its concentration gradient or electrochemical gradient, mediated by specific transport proteins and requiring an expenditure of energy.

66
Q

What types of proteins are involved in Active Transport?

A

Carrier Proteins

67
Q

As in other types of cellular work, _____ supplies the energy for most active transport.

A

ATP Hydrolysis

68
Q

How can ATP power active transport?

A

When its terminal phosphate group is transferred directly to the transport protein, the protein can be induced to change its shape in a manner that translocates a solute bound to the protein across the membrane.

69
Q

Define Sodium-Potassium Pump

A

A transport protein in the plasma membrane of animal cells that actively transports sodium out of the cell and potassium into the cell. SO-PI 3 Sodium ions are out and 2 potassium ions come in.

70
Q

The cytoplasmic side of the membrane is _____ in charge relative to the extracellular side because of _____.

A

Negative; unequal distribution of anions and cations on the two sides.

71
Q

Define Membrane Potential

A

The difference in electrical charge (voltage) across a cell’s plasma membrane due to the differential distribution of ions. Membrane potential affects the activity of excitable cells and the transmembrane movement of all charged substances.

72
Q

Are both carrier proteins and channel proteins used in facilitated diffusion?

A

Yes, they can be used.

73
Q

What are the two forces that can affect the diffusion of ions across a membrane?

A

Chemical Force and Electrical Force

74
Q

Define Electrochemical Gradient

A

The diffusion gradient of an ion, which is affected by both the concentration differences of an ion across a membrane (a chemical force) and the ion’s tendency to move relative to the membrane potential (an electrical force).

75
Q

An ion diffuses not simply down its ______ but, more exactly, down its _____. For example, the concentration of Na+ inside a resting nerve cell is much ______ than outside it.

A

Concentration-Electrochemical-Less

76
Q

Define Electrogenic Pump

A

An active transport protein that generates voltage across a membrane while pumping ions.

77
Q

The _____ appears to be the major electrogenic pump of animal cells.

A

Sodium-Potassium

78
Q

Define Proton Pump

A

An active transport protein in a cell membrane that uses ATP to transport hydrogen ions out of a cell against their concentration gradient, generating a membrane potential in the process. HO

79
Q

Define Cotransport

A

The coupling of the downhill diffusion of one substance to the uphill transport of another against its own concentration gradient.

80
Q

_____ across the plasma membrane occur by exocytosis and endocytosis.

A

Bulk Transport

81
Q

Define Exocystosis

A

The cellular secretion of biological molecules by the fusion of vesicles containing them with the plasma membrane.

82
Q

Define Endocytosis

A

Cellular uptake of biological molecules and particulate matter via formation of vesicles from the plasma membrane.

83
Q

What are the different types of Endocytosis?

A

Phagocytosis (Cellular Eating)-Pinocytosis (Cellular Drinking)- Receptor Mediated Endocytosis PPR

84
Q

Define Phagocytosis

A

A type of endocytosis in which large particulate substances or small organisms are taken up by a cell. It is carried out by some protists and by certain immune cells of animals. PhagoEat

85
Q

In phagocytosis, a cell engulfs a particle by extending _____ around it and packaging it within a membranous sac called a _____.

A

Pseudopodia-Food Vacuole

86
Q

Define Pinocytosis

A

A type of endocytosis in which the cell ingests extracellular fluid and its dissolved solutes. PinoDrink

87
Q

Define Receptor-Mediated Endocytosis

A

The movement of specific molecules into a cell by the unfolding of vesicles containing proteins with receptor sites specific to the molecule being taken in; enables a cell to acquire bulk quantities of specific substances.

88
Q

What molecules pass easily through the bilayer?

A

Gases, hydrophobic molecules, and small polar uncharged molecules can diffuse through phospholipid bilayers.

Bio 5A Lecture (16 decks)

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