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Biology 202 > Chapter 7 > Flashcards

Chapter 7 Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What is the boundary that separates living cells from its surroundings?

A

the plasma membrane

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2
Q

Selective permeability

A

allowing some substances to cross more easily than others

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3
Q

What is fundamental to life?

A

the ability of the cell to discriminate in its chemical exchanges with its environment

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4
Q

What is the most abundant lipid in the plasma membrane?

A

phospholipids

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5
Q

What are amphipathic molecules?

A

containing both hydrophobic and hydrophilic regions

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6
Q

What does the fluid mosaic model state?

A

that a membrane is a fluid structure with a “mosaic” of various proteins embedded in it

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7
Q

Who proposed the sandwich model?

A

Hugh Davson & James Danielli

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8
Q

What did the sandwich model propose? And what was the issue with this proposal?

A

-the phospholipid bilayer lies between 2 layers of globular proteins
-(issue)the placement of membrane proteins, which have hydrophilic and hydrophobic regions

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9
Q

Who proposed that the membrane is a mosaic of proteins dispersed within the bilayer, with only the hydrophilic regions exposed to water?

A

S.J. Singer & G. Nicolson

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10
Q

What is freeze-fracture?

A

a specialized preparation technique that splits a membrane along the middle of the phospholipid bilayer

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11
Q

What are membrane molecules held in place by?

A

weak hydrophobic interactions

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12
Q

How many times per second do adjacent phospholipids switch positions?

A

107

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13
Q

True or False: Flip-flopping across the membrane is not rare

A

False

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14
Q

Membranes rich in unsaturated fatty acids are

A

more fluid than those rich in saturated fatty acids

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15
Q

Cholesterol restrains movement of phospholipids

A

at warm temperatures

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16
Q

Cholesterol maintains fluidity by preventing tight packing

A

at cool temperatures

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17
Q

What occurs as temperatures cool?

A

membranes switch from fluid to a solid state

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18
Q

What do the membranes of fishes living in extreme cold temperatures have?

A

a high proportion of unsaturated hydrocarbon tails, enabling them to stay fluid

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19
Q

What do the membranes of bacteria and archaea living in thermal hot springs and geysers have?

A

unusual lipids that prevent excessive fluidity at such high temperatures

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20
Q

Adaptations to specific environments can be seen in?

A

variations in lipid composition of cell membranes
EXAMPLE: winter wheat increase the percentage of unsaturated phospholipids in their membranes in the autumn to prevent the membranes from solidifying during winter

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21
Q

What are the 2 major populations of membrane proteins?

A

integral and peripheral

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22
Q

What are peripheral proteins?

A

bound to the surface of the membrane

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23
Q

Integral proteins

A

penetrate the hydrophobic core

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24
Q

What are transmembrane proteins?

A

integral proteins that span the membrane

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25
Q

Alpha helices

A

one or more stretches of coiled nonpolar amino acids along the hydrophobic regions of an integral protein

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26
Q

What are the 6 major functions of membrane proteins?

A

-transport of specific solutes into or out of cells
-enzymatic activity, sometimes catalyzing one of a number of steps of metabolic pathway
-signal transduction, relaying hormonal messages to the cell
-cell-cell recognition, allowing other proteins to attach 2 adjacent cells together
-intercellular joining of adjacent cells with gap or tight junctions
-attachment to the cytoskeleton and extracellular matrix, maintaining cell shape and stabilizing the location of certain membrane proteins

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27
Q

What is the name of white blood cells that are am essential part of the human immune system?

A

CD4+ T helper cells

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28
Q

Why are CD4+ T helper cells called helper cells?

A

one of their main roles is to send signals to other types of immune cells

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29
Q

What is CCR5 or CD195?

A

a protein on the surface of white blood cells that is involved in the immune system as it acts as a receptor for chemokines

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30
Q

Cell-cell recognition

A

-recognize each other by binding to surface molecules, often containing carbohydrates, on the extracellular surface of the plasma membrane
-important in the sorting and organizing of cells into tissues and organs during development
-basis for the rejection of foreign cells by the immune system

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31
Q

Membrane carbohydrates may be covalently bonded to both

A

lipids(forming glycolipids) or proteins (forming glycoproteins)

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32
Q

Where do carbohydrates vary among species?

A

on the external side of the plasma membrane

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33
Q

What is an example of variation seen in the carbohydrate part of glycoproteins on the membranes of red blood cells?

A

Blood types (A, B, AB, and O)

34
Q

When is the asymmetrical distribution of proteins, lipids, and associated carbohydrates in the plasma membrane determined?

A

when the membrane is built by the ER and golgi apparatus

35
Q

Which molecules can dissolve in the lipid bilayer and pass through the membrane rapidly?

A

hydrophobic(nonpolar) molecules, such as hydrocarbons and CO2, and O2

36
Q

Which molecules do not cross the membrane easily?

A

polar molecules, such as sugars, and their surrounding shell of water

37
Q

What do transport proteins allow?

A

passage of hydrophilic substances across the membrane

38
Q

Examples of transport proteins

A

channel proteins: have a hydrophilic channel that certain molecules or ions can use as a tunnel
carrier proteins: bind to molecules and change shape to shuttle them across the membrane

39
Q

Aquaporins

A

channel proteins that facilitate the passage of water

40
Q

Diffusion

A

the tendency for molecules to spread out evenly into the available space; may be directional; at dynamic equilibrium(cross the membrane in one direction as in the other)

41
Q

Concentration gradient

A

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

42
Q

True or False: no work must be done to move substances down the concentration gradient

A

True

43
Q

Passive transport

A

the diffusion of a substance across a biological membrane that requires no energy from the cell to make it happen

44
Q

What is osmosis?

A

the diffusion of water across a selectively permeable membrane

45
Q

How does water diffuse?

A

across a membrane from the region of lower solute concentration to the region of higher solute concentration until the solute concentration is equal on both sides

46
Q

Tonicity

A

the ability of a surrounding solution to cause a cell to gain or lose water

47
Q

Isotonic solution

A

solute concentration is the same as that inside the cell; no net water movement across the plasma membrane

48
Q

Hypertonic solution

A

solute concentration is greater than that inside the cell; cell loses water

49
Q

Hypotonic solution

A

solute concentration is less than that inside the cell; cell gains water

50
Q

What helps maintain water balance?

A

cell walls

51
Q

How does a plant cell become turgid(firm)?

A

in a hypotonic solution; swells until the wall opposes uptake

52
Q

How does a plant cell become flaccid(limp)?

A

if it and it’s surroundings are isotonic; no net movement of water into the cell; plant may wilt

53
Q

What causes plasmolysis?

A

plant cells lose water in a hypertonic environment, the membrane pulls away from the wall resulting in plasmolysis

54
Q

Osmoregulation

A

the control of solute concentrations and water balance

55
Q

The protist Paramecium

A

hypertonic to its pond water environment; has a contractile vacuole that acts as a pump

56
Q

Facilitated diffusion

A

-transport proteins speed the passive movement of molecules across the plasma membrane
-channel proteins provide corridors that allow a specific molecule or ion to cross the membrane
-solute moves down concentration gradient & transport requires no energy

57
Q

Channel proteins include

A

aquaporins and ion channels

58
Q

Aquaporins

A

facilitated diffusion of water

59
Q

Ion channels

A

open or close in response to a stimulus

60
Q

Some diseases are caused by malfunctions in specific transport systems, what’s an example of this?

A

the kidney disease cystinuria
-absence of a carrier protein that transports cysteine and other amino acids across the membranes of kidney cells
-painful kidney stones as amino acids accumulate and crystallize in the kidneys

61
Q

Active transport

A

moves substances against their concentration gradient
-requires energy, usually in the form of ATP
-performed by specific proteins embedded in the membranes
-allows cells to maintain concentration gradients that differ from their surroundings - [K+] - high inside the cells and low outside; [Na+] - low inside, high outside

62
Q

Sodium-potassium pump

A

uses between 20 to 40% of the body energy

63
Q

How is voltage created?

A

by differences in the distribution of positive or negative ions across a membrane

64
Q

Membrane potential

A

the voltage difference across a membrane: cytoplasm(-); extracellular(+)

65
Q

Electrochemical gradient

A

two combined forces drive the diffusion of ions across a membrane

66
Q

Chemical force

A

the ion’s concentration gradient

67
Q

Electrical force

A

the effect of the membrane potential on the ion’s movement

68
Q

What is an electrogenic pump?

A

a transport protein that generates voltage across a membrane (sodium-potassium in animal cells)

69
Q

What is the main electrogenic pump of plants, fungi, and bacteria?

A

proton pump

70
Q

What do electrogenic pumps help with?

A

store energy that can be used for cellular work

71
Q

Cotransport

A

occurs when active transport of a solute indirectly drives transport of other solutes
-plants commonly use the gradient of hydrogen ions generated by proton pumps to drive active transport of nutrients into the cell
EXAMPLE: diffusion of H+ into the cell and the transport of sucrose into the cell

72
Q

How do small molecules and water enter or leave the cell?

A

through the lipid bilayer or via transport proteins

73
Q

How do large molecules, such as polysaccharides and proteins cross the membrane?

A

in bulk via vesicles(requires energy)

74
Q

Exocytosis

A

-transport vesicles migrate to the membrane, fuse with it, and release their contents
-many secretory cells use exocytosis to export their products

75
Q

Examples of secretory cells using exocytosis

A

-pancreatic cells: secrete insulin into the blood
-neurons: release neurotransmitters that signal other neurons or muscle cells
-plant cells: delivers proteins and certain carbohydrates from golgi vesicles to the outside of the cell

76
Q

Endocytosis

A

the cell takes in macromolecules by forming vesicles from the plasma membrane; reversal of exocytosis, involving different proteins

77
Q

What are the 3 types of endocytosis?

A

-phagocytosis(“cellular eating”)
-pinocytosis(“cellular drinking”)
-receptor-mediated endocytosis

78
Q

What occurs in phagocytosis?

A

a cell engulfs a particle in a vacuole
-vacuole fuses with a lysosome to digest the particle

79
Q

What occurs during pinocytosis?

A

molecules are taken up when extracellular fluid is “gulped” into tiny vesicles

80
Q

What occurs during receptor-mediated endocytosis?

A

binding of ligands to receptors triggers vesicle formation

81
Q

What is a ligand?

A

any molecules that binds specifically to a receptor site of another molecule

Biology 202 (5 decks)

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