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MCAT Content Review > BIO6: Eukaryotic Cells: Plasma Memberane and Cytoskeleton > Flashcards

BIO6: Eukaryotic Cells: Plasma Memberane and Cytoskeleton Flashcards

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MCAT flashcards
1
Q

What is the resting membrane potential of the plasma membrane?

A

neg 70 mV

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2
Q

What is the structure of the plasma membrane?

A

Phospholipid bilayer

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3
Q

What is the structure of a phospholipid bilayer?

A

Double layer of phospholipids (hydrophobic tails inside; hydrophilic heads in cytoplasm and environment)

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4
Q

How is the phospholipid bilayer formed?

A

It is spontaneously formed by free floating phospholipids (-delta G)

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5
Q

What are the components of the plasma membrane?

A
  1. Phospholipids
  2. Glycolipids
  3. Cholesterol
  4. Proteins
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6
Q

What types of proteins exist in the plasma membrane?

A
  1. Peripheral protein
  2. Integral protein
  3. Transmembrane protein
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7
Q

What types of molecules can pass through the plasma membrane?

A

Small non-polar: O2, CO2, steroid hormones

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8
Q

What types of phospholipids characterize a more fluid bilayer?

A

Unsaturated fatty acids (more kinks) and shorter fatty acids (less LDF)

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9
Q

Glycolipid structure

A

Carbohydrate attached to a lipid

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10
Q

Where are glycolipids found?

A

Exterior surface of dukaryotic cell membranes

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11
Q

Function of glycolipids?

A

Cell-cell communication, recognition, binding, interaction

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12
Q

What is the structure of cholesterol?

A

Tetracyclic ring structure

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13
Q

What is the function of cholesterol?

A

Maintains fluidity and firmness of the membrane

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14
Q

What is the difference between integral and transmembrane proteins?

A

Transmembrane proteins connect the cytoplasm to extracellular environment; integral proteins embed into the membrane but do not go through it

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15
Q

Hypotonic

A

Low solute concentration

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16
Q

Hypertonic

A

High solute concentration

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17
Q

What happens when a cell is in a hypotonic solution?

A

Water will osmose in and the cell will burst

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18
Q

What happens when a cell is in a hypertonic solution?

A

The water will osmose out and the cell will shrivel

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19
Q

How does water move in and out of cells?

A

Cell membranes are semi-permeable and water moves through osmosis or can pass through aquaporin proteins

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20
Q

What are the colligative properties?

A 
They describe the solution based on the ratio of solute to solvent particles
Higher solute concentrations lead to;
1. Osmotic pressure increase
2. Boiling point elevation 
3. Vapor pressure lowering
4. Freezing point depression
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21
Q

Passive transport

A

No energy input is required/spontaneous

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22
Q

What are the types of passive transport?

A
  1. Simple diffusion

2. Facilitated diffusion

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23
Q

Simple diffusion

A

Solute particle diffuses across membrane without a helper protein

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24
Q

Facilitated diffusion

A

Molecule requires a helper protein to move down its gradient across the membrane

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25
Q

What are the types of facilitated diffusion?

A
  1. Channel protein

2. Carrier proteins

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26
Q

What are the types of channel proteins?

A
  1. Ion channels

2. Gated channels

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27
Q

What are the types of gated channels and what are their differences?

A
  1. Voltage-gated channel (responds to a change in voltage)

2. Ligand-gated channel (responds to a neurotransmitter)

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28
Q

What is the difference between channel proteins and carrier proteins?

A

Channel proteins are transmembrane proteinsvs. Carrier proteins which bind to molecules that result in a conformational change and the molecule is released on the other side

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29
Q

What are the types of carrier proteins?

A
  1. Uniport (A only)
  2. Symport (A and B)
  3. Antiport (A for B)
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30
Q

What is the difference between facilitated and simple diffusion?

A

The rate of simple diffusion increases linearly as the driving force increases but is limited by surface area
The rate of facilitated diffusion reaches a mx and levels off as tranport proteins are saturated

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31
Q

Active transport

A

Energy input is required to transport particles against their gradient

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32
Q

Primary active transport

A

Transport of molecule is directly coupled to ATP hydrolysis

33
Q

Secondary active transport

A

ATP used to build up an electrochemical gadient that can be used as stored potential energy

34
Q

Sodium-potassium pump

A

Na+/K+ ATPase: actively transports 3 Na+ OUT and 2K+ IN

35
Q

What does the sodium-potassium pump maintain?

A

Excess in sodium ions outside of the cell and potassium inside the cell

36
Q

How is the membrane potential maintained?

A

The movement of 3 Na+ OUT and 2K+ IN maintains a negative membrane potential

37
Q

Potassium leak channels

A

Ion channel that maintains negative membrane potential through loss of positive K+ ions

38
Q

What are the ion concentrations across the membrane?

A

Higher outside the cell: Na+, Ca2+, Cl-

Higher inside the cell: proteins, K+

39
Q

Exocytosis

A

Membrane-bound vesicle fuses with plasma membrane, releasing contents (requires energy input)

40
Q

Endocytosis

A

Substances taken into the cell when the plasma membrane invaginates, vesicle is released in the cell (requires energy input)

41
Q

How are large/polar molecules transported across the cellular membrane?

A

Exocytosis or endocytosis

42
Q

What are the types of endocytosis?

A

Phagocytosis and pinocytosis

43
Q

Cell surface receptors

A

Integral membrane proteins that bind to molecules (e.g. hormones, NT, ligands/solutes) extracellularly to send a signal to the cell

44
Q

What is the function of cell surface receptors?

A

Cells alter structure and function in response to the signal (physical, chemical, membrane potential, etc.)

45
Q

Signal transduction

A

Ligand and receptor bind to set off chain of reactions usually involving protein phosphorylation that signals a cell

46
Q

What enzyme is used in the signal transduction pathway?

A

Protein kinases

47
Q

Protein kinases

A

Phosphorylation of molecules and/or other proteins during the cascade

48
Q

Secondary messengers

A

Molecules within the cell in the signal transduction pathway that transduce and amplify the signal

49
Q

What are examples of secondary messangers?

A

cAMP, cGMP

50
Q

cAMP

A

adenosine 3’,5’-cyclic monophosphate nucleotide that is a key secondary messanger in many signal transduction pathways

51
Q

What are the types of membrane receptors?

A
  1. Ligand-gated ion channel
  2. Enzyme-linked receptor
  3. G-protein coupled receptor
52
Q

Ligand-gated ion channel

A

Neurotrasmitter triggers an ion channel to open, ion moves across membrane, cell depolarizes/hyperpolarizes

53
Q

Cell depolarization is what type of response?

A

More positive, excitatory

54
Q

Cell hyperpolarization is what type of response?

A

More negative, inhibitory

55
Q

Enzyme-liked receptor

A

Membrane protein is associated with another enzyme (usually a kinase)

56
Q

G-protein coupled receptor

A

Signal in environment detected by membrane protein activates a g-protein which activates a signal cascade of secondary messengers

57
Q

Adenylyl cyclase

A

Makes cAMP from ATP

58
Q

Gap junctions

A

Pore-like connection between two cells that directly connect their intracellular environments

59
Q

What is the gap junction equivalent in plant cells?

A

Plasmodesmata

60
Q

Tight junctions

A

Form an impermeable barrier that prevents substances from passing between the connected cells (e.g. bladder, GI) to seal

61
Q

Desmosome

A

Connect cells linking cytoskeletons to strengthen tissue (e.g. keratin, cadherin)

62
Q

How do desmosomes function?

A

Fibers of desmosomes span connected plasma membranes and radiate into the cell connecting the cytoskeletons via intermediate filaments

63
Q

Plasmodesmata

A

Tunnels passing through adjacent cell walls enabling communication and exchange

64
Q

What are eukaryotic cytoskeleton components?

A
  1. Microtubules
  2. Intermediate filaments
  3. Microfilaments
65
Q

What are the roles of the cytoskeleton?

A
  1. structural support
  2. cell movement
  3. transport of vesicles throughout the cell
66
Q

Microfilaments

A

Polymers of actin protein constantly being polymerized and depolymerized

67
Q

What is the function of microfilaments?

A
  1. Cytokinesis
  2. Cell movement
  3. Muscle contractions
  4. Exocytosis/endcytosis
68
Q

What is the process of muscle contractions?

A

Actin filaments pulling on myosin heads

69
Q

Intermediate filaments

A

Polymers of proteins to support overall shape and cell-to-cell adhesion

70
Q

What is the structure of microtubules?

A

Hollow alpha and beta tubulin dimers

71
Q

What is the function of microtubules?

A
  1. Cellular highway to transport vesicles by motor proteins
  2. Mitotic spindle enables separation of sister chromatids/homologous chromosomes
  3. Microtubules organizing center
  4. Cilia and flagella
72
Q

Centrioles

A

Microtubule fibers (spindle fibers) elongate outward from the centrioles and attach to centromeres

73
Q

Kinetochore

A

Where the centrioles attach to centromeres

74
Q

What is the structure of centriole?

A

Hollow ring of 9 microtubule triplets

75
Q

Centrosome

A

2 centrioles and other associated proteins used in cell division

76
Q

Spindle apparatus

A

Mitotic spindle of various microtubules and other motor proteins that pulls the homologous chromatids to the opposite ends of the cell

77
Q

What is the structural difference between cilia and flagella?

A

Cilia are shorter and have many cilia per cell and only one/few flagella

78
Q

What is the ultimate structure of cilia and flagella?

A

9+2 arrangement of microtubules

79
Q

What domain are eukaryotic cells?

A

Eukarya

MCAT Content Review (13 decks)

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