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

BIO6: Eukaryotic Cells: Plasma Memberane and Cytoskeleton 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
What are the types of facilitated diffusion?
1. Channel protein | 2. Carrier proteins
26
What are the types of channel proteins?
1. Ion channels | 2. Gated channels
27
What are the types of gated channels and what are their differences?
1. Voltage-gated channel (responds to a change in voltage) | 2. Ligand-gated channel (responds to a neurotransmitter)
28
What is the difference between channel proteins and carrier proteins?
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
29
What are the types of carrier proteins?
1. Uniport (A only) 2. Symport (A and B) 3. Antiport (A for B)
30
What is the difference between facilitated and simple diffusion?
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
31
Active transport
Energy input is required to transport particles against their gradient
32
Primary active transport
Transport of molecule is directly coupled to ATP hydrolysis
33
Secondary active transport
ATP used to build up an electrochemical gadient that can be used as stored potential energy
34
Sodium-potassium pump
Na+/K+ ATPase: actively transports 3 Na+ OUT and 2K+ IN
35
What does the sodium-potassium pump maintain?
Excess in sodium ions outside of the cell and potassium inside the cell
36
How is the membrane potential maintained?
The movement of 3 Na+ OUT and 2K+ IN maintains a negative membrane potential
37
Potassium leak channels
Ion channel that maintains negative membrane potential through loss of positive K+ ions
38
What are the ion concentrations across the membrane?
Higher outside the cell: Na+, Ca2+, Cl- | Higher inside the cell: proteins, K+
39
Exocytosis
Membrane-bound vesicle fuses with plasma membrane, releasing contents (requires energy input)
40
Endocytosis
Substances taken into the cell when the plasma membrane invaginates, vesicle is released in the cell (requires energy input)
41
How are large/polar molecules transported across the cellular membrane?
Exocytosis or endocytosis
42
What are the types of endocytosis?
Phagocytosis and pinocytosis
43
Cell surface receptors
Integral membrane proteins that bind to molecules (e.g. hormones, NT, ligands/solutes) extracellularly to send a signal to the cell
44
What is the function of cell surface receptors?
Cells alter structure and function in response to the signal (physical, chemical, membrane potential, etc.)
45
Signal transduction
Ligand and receptor bind to set off chain of reactions usually involving protein phosphorylation that signals a cell
46
What enzyme is used in the signal transduction pathway?
Protein kinases
47
Protein kinases
Phosphorylation of molecules and/or other proteins during the cascade
48
Secondary messengers
Molecules within the cell in the signal transduction pathway that transduce and amplify the signal
49
What are examples of secondary messangers?
cAMP, cGMP
50
cAMP
adenosine 3',5'-cyclic monophosphate nucleotide that is a key secondary messanger in many signal transduction pathways
51
What are the types of membrane receptors?
1. Ligand-gated ion channel 2. Enzyme-linked receptor 3. G-protein coupled receptor
52
Ligand-gated ion channel
Neurotrasmitter triggers an ion channel to open, ion moves across membrane, cell depolarizes/hyperpolarizes
53
Cell depolarization is what type of response?
More positive, excitatory
54
Cell hyperpolarization is what type of response?
More negative, inhibitory
55
Enzyme-liked receptor
Membrane protein is associated with another enzyme (usually a kinase)
56
G-protein coupled receptor
Signal in environment detected by membrane protein activates a g-protein which activates a signal cascade of secondary messengers
57
Adenylyl cyclase
Makes cAMP from ATP
58
Gap junctions
Pore-like connection between two cells that directly connect their intracellular environments
59
What is the gap junction equivalent in plant cells?
Plasmodesmata
60
Tight junctions
Form an impermeable barrier that prevents substances from passing between the connected cells (e.g. bladder, GI) to seal
61
Desmosome
Connect cells linking cytoskeletons to strengthen tissue (e.g. keratin, cadherin)
62
How do desmosomes function?
Fibers of desmosomes span connected plasma membranes and radiate into the cell connecting the cytoskeletons via intermediate filaments
63
Plasmodesmata
Tunnels passing through adjacent cell walls enabling communication and exchange
64
What are eukaryotic cytoskeleton components?
1. Microtubules 2. Intermediate filaments 3. Microfilaments
65
What are the roles of the cytoskeleton?
1. structural support 2. cell movement 3. transport of vesicles throughout the cell
66
Microfilaments
Polymers of actin protein constantly being polymerized and depolymerized
67
What is the function of microfilaments?
1. Cytokinesis 2. Cell movement 3. Muscle contractions 4. Exocytosis/endcytosis
68
What is the process of muscle contractions?
Actin filaments pulling on myosin heads
69
Intermediate filaments
Polymers of proteins to support overall shape and cell-to-cell adhesion
70
What is the structure of microtubules?
Hollow alpha and beta tubulin dimers
71
What is the function of microtubules?
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
Centrioles
Microtubule fibers (spindle fibers) elongate outward from the centrioles and attach to centromeres
73
Kinetochore
Where the centrioles attach to centromeres
74
What is the structure of centriole?
Hollow ring of 9 microtubule triplets
75
Centrosome
2 centrioles and other associated proteins used in cell division
76
Spindle apparatus
Mitotic spindle of various microtubules and other motor proteins that pulls the homologous chromatids to the opposite ends of the cell
77
What is the structural difference between cilia and flagella?
Cilia are shorter and have many cilia per cell and only one/few flagella
78
What is the ultimate structure of cilia and flagella?
9+2 arrangement of microtubules
79
What domain are eukaryotic cells?
Eukarya

MCAT Content Review (13 decks)

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