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Cell Biology > Cell Biology Exam 3 > Flashcards

Cell Biology Exam 3 Flashcards

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1
Q

What are the three functions of a plasma membrane?

A

Define cellular space and boundaries, Maintain biochemical and electrical differences, Pathway for extracellular communication.

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2
Q

What kinds of membranes can be found in Eukaryotes?

A

Plasma membrane and organelle membrane.

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3
Q

Prokaryotes contain what kind of membrane?

A

Plasma membrane only.

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4
Q

What are the plasma and organelle membranes composed of?

A

Lipid bilayer, Many inserted and surface associated proteins, A few other types of molecules.

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5
Q

Membrane lipids that compose the lipid bilayer are _______ molecules.

A

Amphipathic

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6
Q

What does amphipathic mean?

A

Polar and Non-Polar Bonds

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7
Q

What are the two regions on membrane lipids?

A

Hydrophilic (polar) “head” region and hydrophobic (non-polar) “tail” region.

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8
Q

Why is the shape of membrane lipids unique?

A

Amphipathic regions are on the opposite ends of the molecules.

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9
Q

Membrane lipids spontaneously form _______ in _______ solution.

A

Bilayers; Aqueous

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10
Q

How does the shape of the lipid molecule affect the packing of lipid molecules?

Two bilayer shapes resulting from two ampipathic molecules.

A

One carbon tail causes a sphere shaped molecule due to Vander Waals dimensions. Two carbon tails causes a column shaped molecule due to Vander Waals dimensions.

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11
Q

Regarding the lipid bilayer, is one carbon tails or two carbon tails found in biology?

A

Two carbon tails.

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12
Q

Grouping of two carbon tailed membrane lipids produces a sheet of phospholipid bilayer, which is energetically (favorable/unfavorable) because why? What is the end result?

A

Energetically unfavorable as the hydrophobic edges of the sheet are exposed to water. The sheet folds into a sealed compartment/sphere with water on the inside and the outside of the sphere.

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13
Q

What is the most abundant lipid cell in cell membranes? How many major types?

A

Phospholipids; 4 Major Types

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14
Q

Three out of the four major phospholipids are referred to as __________ and all have _______ as their base.

A

Phosphoglycerides; Glycerol

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15
Q

What are the three movements that characterize the lipid bilayer as “fluid”?

A

Individual lipids diffuse laterally, Rotate rapidly about their axis, Nonpolar tails extremely flexible.

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16
Q

The lipid bilayer is a very (non-mobile/mobile) and (static/dynamic) element.

A

Mobile; Dynamic

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17
Q

What effect does temperature have on the lipid bilayer?

A

An increase in temperature increases the fluidity and movement of the membrane.

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18
Q

What two ways allow cells to maintain constant fluidity independent of temperature?

A

Cis-double bonds in fatty acid tails and addition of other types of molecules.

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19
Q

What does “polyunsaturated” mean?

A

Have multiple “kinks.”

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20
Q

Do saturated hydrocarbon chains or unsaturated hydrocarbon chains have “kinks” in them?

A

Unsaturated Hydrocarbon Chains

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21
Q

Describe the differences between unsaturated and saturated hydrocarbon chains in terms of bonds and hydrogens.

A

Saturated hydrocarbon chains have all single bonded carbons with as many hydrogens as possible. Unsaturated hydrocarbon chains have a cis-double bond, in which two hydrogens are taken off of the same side.

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22
Q

How do cis-double bond tails help maintain a level of fluidity in a cell?

A

Components cannot get as close together due to the “kinks” or cis-double bonds, allowing more movement. The number of lipids with these cis-double bond tails are adjusted to maintain this fluidity despite temperature fluctuations.

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23
Q

The addition of this non-phospholipid amphipathic molecule can affect the fluidity of the lipid bilayer.

A

Cholesterol

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24
Q

What are the two effects cholesterol has on the fluidity of the lipid bilayer?

A

Interacts with phospholipids to increase rigidity between tails near head region while the lower ends of the tails remain flexible. Disrupts attractive interactions between phospholipids to prevent crystallization (freezing).

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25
Q

What type of association holds lipid rafts together?

A

Weak associations/noncovalent bonds.

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26
Q

Describe the association, types of molecules found, and movement of lipid rafts.

A

Weak associations between lipids. Membrane proteins and cholesterol inserted into the raft. Drift as a group through the membrane.

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27
Q

Is the membrane in the lipid raft region thicker or thinner than the rest of the membrane? Why?

A

Thicker. May be a mechanism for holding membrane proteins.

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28
Q

What components are glycolipids composed of?

A

Lipid Molecules + Attached Sugar Molecules.

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29
Q

Where are glycolipids found in the cell?

A

Found only on non-cytoplasmic surfaces (Extracellular and Intraorganelle)

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30
Q

Where will glycolipids NEVER be found?

A

On the outside of organelle or the inside of plasma membrane.

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31
Q

What are the three intentional functions of glycolipids?

A

Protection. Charged glycolipids concentrate ions at cell surfaces. Cell recognition.

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32
Q

What is the unintended function of glycolipids?

A

May allow bacterial toxins to enter cells.

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33
Q

Describe the electrical charge in glycolipids.

A

Carry an electrical charge that is concentrated around transport pumps/proteins on plasma membrane.

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34
Q

_____________ define much of membrane functions.

A

Membrane Proteins

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35
Q

What term refers to the amount and type of protein in any region?

A

Protein Population

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36
Q

How can the protein population of any region of membrane be described?

A

Highly Variable

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37
Q

Membrane proteins also often have ____________ attached to their ____________, similar to _________.

A

Oligosaccharide Chains; Non-Cytosolic Domains; Glycolipids

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38
Q

What are the two mechanisms of association that are discussed regarding the lipid bilayer?

A

Transmembrane and Surface

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39
Q

Is transmembrane association amphipathic or non-amphipathic? Why?

A

Always amphipathic in order to interact with aqueous environment.

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40
Q

T/F: Transmembrane association can be single, multi-pass, or a spanning segment.

A

True

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41
Q

Describe the spanning segment of transmembrane association and its most common location.

A

Often alpha-helix or beta-barrel. More common in prokaryotes as the cell wall makes a larger distance to get through. Despite its larger size compared to the single or multi-pass, it is still highly regulated on what can pass through it.

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42
Q

Surface association is usually _________ and sometimes ________.

A

Cytosolic; Extracellular

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43
Q

What are the four attachment mechanisms of surface association?

A

Alpha-helix associated with lipid bilayer. Covalent attachment via oligosaccharide chain. Covalent attachment to amphipathic tether. Noncovalent attachment to transmembrane protein.

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44
Q

What type of attachment is peripheral?

A

Weak noncovalent surface attachment.

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45
Q

What type of attachment is integral?

A

Transmembrane or covalently attached surface.

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46
Q

T/F: All peripheral proteins are surface, but not all surface proteins are peripheral.

A

True

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47
Q

T/F: All surface proteins are peripheral, but not all peripheral proteins are surface.

A

False

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48
Q

T/F: All transmembrane proteins are integral, but not all integral proteins are transmembrane.

A

True

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49
Q

T/F: All integral proteins are transmembrane, but not all transmembrane proteins are integral.

A

False

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50
Q

T/F: Spectrin has the same qualities of hundreds of other identical membrane proteins.

A

True

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51
Q

What is Spectrin?

A

A membrane protein that is a cytosolic, noncovalently associated red blood cell protein. Dimer.

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52
Q

What is the function of Spectrin?

A

Associates with cytoskeleton and other proteins to form a flexible mesh to maintain cell shape (concave red blood cell).

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53
Q

Is Spectrin a dimer?

A

True

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54
Q

Describe the structure of Spectrin.

A

Strong, flexible, “mesh-like” structure.

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55
Q

What is Glycophorin? What kind of transmembrane association is it?

A

Transmembrane red blood cell protein. Membrane spanning domain (alpha-helix).

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56
Q

Describe the domain of Glycophorin.

A

Extensive, Elaborate, Extracellular

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57
Q

Describe the structure and characteristics of Glycophorin.

A

Composed of 16 oligo chains (around 100 sugars). Hydrophilic and fully charged amino acids and sugars.

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58
Q

What is the function of Glycophorin?

A

“Coats” cell in a water lubricant, well adapted for motility.

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59
Q

Where does Bacteriorhodopsin come from?

A

A bacterial organism.

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60
Q

What is Bacteriorhodopsin?

A

Multi-pass transmembrane protein that functions as a proton pump in archaea.

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61
Q

Bacteriorhodopsin contains which organic molecule? This is a type of what?

A

Retinal; Type of chromophore.

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62
Q

Describe how the structure of Bacteriorhodopsin contributes to its structure.

A

Contains an organic molecule called retinal, which is a type of chromophore. Chromophores respond to photons. Photon contacts and changes the shape of retinal, which causes a cascade of small conformational changes. These conformational changes pump protons out of the cell.

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63
Q

What is significant about the mechanism of Bacteriorhodopsin?

A

Doesn’t rely on a chemical change in cell environment.

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63
Q

What is the effect of conformational changes in Bacteriorhodopsin?

A

Perform mechanical work to pump protons out of the cell.

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64
Q

What happens after Bacteriorhodopsin pumps protons out of the cell?

A

Protons flow back into cell through another transmembrane protein. This protein uses energy from proton flow to produce ATP.

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65
Q

How does Rhodopseudomonas viridis compare to Bacteriorhodopsin?

A

Has the exact same function, just more complex (more subunits) and more efficient.

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66
Q

What is Glycocalyx? What is it attached to?

A

Extracellular surface covered with sugars. Covalently attached to membrane proteins (glycoproteins) and lipids (glycolipids). Many different monosaccharides.

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67
Q

What is the function of Glycocalyx?

A

Protection against mechanical damage and cell recognition.

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68
Q

What two components make up the Electrochemical Gradient in a cell?

A

Electrical Gradient + Chemical Gradient

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69
Q

List the three types of electrochemical gradient in order of increasing permeability.

A

Electrical Opposing Chemical < Chemical Only < Chemical With Electrical

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70
Q

Does the electrical gradient refer to the cell membrane itself or the molecules that move through the cell membrane? What about chemical gradient?

A

Electrical gradient refers to the charge of the cell membrane itself. Chemical gradient refers to the charge of the molecules that pass through the cell membrane.

71
Q

What are the two methods of transport for the movement of large polar molecules or ions?

A

Diffusion-Driven Transport and Active Transport

72
Q

What are the two kinds of Diffusion-Driven Transport? What is the energy source?

A

Passive Diffusion and Assisted Diffusion. The source of energy is gradient.

73
Q

What are the two categories of proteins involved in active transport?

A

Uniporters and Antiporters/Symporters

74
Q

What is the direction of active transport? Does it require energy input?

A

Against the gradient; Yes, it requires energy input.

75
Q

Describe the mechanism of passive diffusion.

A

Highly selective multi-pass transmembrane protein “channels” allow movement down electrochemical gradient.

76
Q

Describe the mechanism of assisted diffusion.

A

Binding of substance to protein channel initiates a conformational change. This conformational change “assists” movement across membrane. Movement is still only down electrochemical gradient.

77
Q

Is active transport against the electrical gradient, chemical gradient, or both?

A

Both

78
Q

What are the three common sources of energy for active transport?

A

Coupled to “downhill” transport of another substance. Coupled to ATP hydrolysis. Coupled to light energy.

79
Q

T/F: All protein channels can be switched between active and inactive conformations.

A

False. Many channels can be, but not all.

80
Q

What controls the switch of protein channels between active and inactive conformations?

A

A variety of ligands or signals.

81
Q

Describe the three types of “gates” that control protein channels.

A

Ligand-gated (neurotransmitter, nucleotide, ion, etc.). Voltage-gated. Mechanically-gated.

82
Q

What is the primary and initial function of the Na+/K+ pump?

A

Maintain osmotic balance across animal cell membranes.

83
Q

What is the mechanism of the Na+/K+ pump? What is the energy source?

A

Pumps 3 Na+ out of the cell and 2 K+ into the cell. ATP driven p-type. Mechanism selected to prevent water from moving into animal cell.

84
Q

Describe the Na+, K+, and Cl- concentrations during the Na+/K+ pump.

A

[Na+] is greater outside the cell because it is being pumped out. [K+] is greater inside the cell because it is being pumped in. [Cl-] is greater outside the cell due to its repulsion of the negative interior.

85
Q

What is “resting” membrane potential? What is the approximate value for most animal cells?

A

The value of electrical force required to balance the chemical force. Value is between -20mV to -200mV.

86
Q

What are K+ “leak” channels?

A

Allows K+ to leak out of the cell down the concentration gradient. Negative charge within cell tends to keep K+ in the cell.

87
Q

What are four examples of electrically excitable cells?

A

Muscle, Nerve, Egg, Endocrine

88
Q

What are the characteristics of electrically excitable cells?

A

Possess voltage-gated cation channels. Able to pass communication signal from one point to another along membrane. Able to transmit signal to membrane of adjacent electrically cell.

89
Q

In electrically excitable cells, what is the form of the signal?

A

Action Potential

90
Q

What is the general idea of the movement of intracellular vesicular traffic in Eukaryotes?

A

Vesicles do not drift, they are carried along cytoskeleton filaments by motor proteins.

91
Q

What are the two origins of vesicular transport?

A

Plasma Membrane and Endoplasmic Reticulum Membrane

92
Q

Vesicular transport involves the movement between ____________ spaces.

A

Topographically Equivalent

93
Q

Where do vesicles originate from?

A

Regions of membrane that acquire sets of protein markers.

94
Q

What are the functions of protein markers in vesicular transport?

A

Concentrate cargo molecules. Develop into a basket-like structure. Bud off as a fully formed vesicle.

95
Q

What results from different combinations of protein markers?

A

A unique protein coat.

96
Q

What are the two main classes of protein coats? Which can be further separated into two subcategories? What are they?

A

Clathrin-Coated and Coatemer-Coated. Coatemer-Coated can be separated into COPI and COPII.

97
Q

What are the four subunits of clathrin-coated vesicles?

A

Clathrin subunits, Adaptin, Cargo receptors, Dynamin

98
Q

What are the steps of clathrin-coated vesicle formation?

A

Protein picks up cargo through high affinity. Conformational change attracts Adaptin and Clathrin and starts the formation of the basket shape. Formation continues until dynamin separates vesicle from source membrane. Results in a fully coated vesicle, in which the vesicle coat disassociates leaving the cargo carried inside the naked transport vesicle.

99
Q

The formation of coatomer coated vesicles involves what?

A

Formation involves coat-recruitment (CR) proteins which are GTPases.

100
Q

For COPII-coated vesicles, what is the CR GTPase involved?

A

SarI

101
Q

What form does cytosolic SarI exist as?

A

GDP-bound form

102
Q

What is the function of Rab GTPases?

A

Ensure specificity between vesicle and target.

103
Q

What conformations do Rab GTPases cycle between?

A

Membrane-bound confirmation (GTP, Active) and cytosolic confirmation (GDP, inactive).

104
Q

Organelle lumens and the extracellular environment are ________ and ________, and are not _______.

A

Biochemically distinct; Topographically equivalent; Continuous

105
Q

What sorting signal, if any, do proteins which are destined to function in the cytosol contain?

A

Contain no sorting signal.

106
Q

What other important conformation does Rab GTPase have besides GDP inactive and GTP active?

A

Confirmation that allows it to bind to Rab Effectors.

107
Q

Where are Rab effectors located? What is their purpose?

A

Located on the target membrane during vesicle transport. Tether specific vesicles near target site. Bound to by Rab GTPase.

108
Q

What is the function of SNARE proteins?

A

Fuse vesicle with target.

109
Q

How many different sets of SNARE proteins are there?

A

20 different sets of SNARE’s. Each associated with different types of vesicle traffic.

110
Q

What does each set of SNARE proteins consist of?

A

A target protein (t-SNARE) and a vesicle protein (v-SNARE).

111
Q

What type of domains do SNARE’s have? How does this contribute to their mechanism?

A

Helical Domains. Spontaneously wrap around each other when brought close together to fuse the vesicle to the target.

112
Q

T/F: Docking and Fusion are two separate processes.

A

True

113
Q

What cellular component facilitates “docking”? How?

A

Rab GTPases by ensuring specificity.

114
Q

What cellular component facilitates “fusion”? How?

A

SNARE’s by pulling the vesicle and target membrane together to force fusion.

115
Q

What are the two vesicular pathways and their direction of movement?

A

Endocytic “brings in” from the plasma membrane to the interior region of the cell. Biosynthetic-secretory/Exocytic “sends out” from the interior region of the cell to the plasma membrane.

116
Q

T/F: Vesicular transport refers to intracellular and extracellular transport.

A

False, majority of the time it only is referring to intracellular.

117
Q

What is the function of an Endocytic Pathway?

A

Takes up molecules from extracellular environment.

118
Q

What is the resulting initial vesicle called in an Endocytic Pathway? What does this mature into?

A

Endosome that matures into Lysosome.

119
Q

Lysosomes contain many types of what?

A

Lysozymes.

120
Q

What is the function of Lysozymes?

A

Digest macromolecules. Resulting catabolic products distributed to the cell.

121
Q

What is the function of the Biosynthetic-Secretory Pathway?

A

Synthesize/modify macromolecules.

122
Q

What are the two pathways within the Biosynthetic-Secretory Pathway?

A

Regulated Pathway and Constitutive Pathway

123
Q

Describe the mechanism of the Regulated Pathway.

A

Stored until needed. Deliver to extracellular environment after receiving signal.

124
Q

Describe the mechanism of the Constitutive Pathway.

A

Continuously delivered to plasma membrane or secreted.

125
Q

The Golgi Apparatus can be compared to what real life object?

A

A moving conveyer belt.

126
Q

What is the structure of the Golgi Apparatus?

A

Organized stacks of disc-like cisternae.

127
Q

What is the function of the Golgi Apparatus?

A

Receives lipids and proteins from the Endoplasmic Reticulum and transports them to various destinations. Often modifies them while en route.

128
Q

When does Vesicular Fusion occur? What happens during this and how does it evolve?

A

Following budding from Endoplasmic Reticulum exit sites. Transport vehicles fuse with one another form tubular clusters.

129
Q

What is the product of vesicular fusion?

A

Tubular Clusters

130
Q

What do vesicular tubular clusters evolve into?

A

Cis face of Golgi

131
Q

How do vesicular tubular clusters travel?

A

Travel along microtubules

132
Q

What is the first step of the retrieval pathway? When does it occur?

A

Transport vesicles “bud off” developing cisternae during the formation of the Golgi.

133
Q

Where do the vesicles travel to in the retrieval pathway?

A

Back to the Endoplasmic Reticulum.

134
Q

What are the two components that are returned in the retrieval pathway?

A

Endoplasmic reticulum proteins that “escaped.” Return proteins involved in original budding and fusion reactions for re-use.

135
Q

What is the coat on the returning vesicle in the retrieval pathway?

A

COPI-Coated, not COPII-Coated.

136
Q

What is the function of lysosomes?

A

Carry out intracellular digestion. Prevents leaked enzymes from digesting cell components.

137
Q

Describe the environment (basic/acidic) of lysosomes.

A

Very acidic environment (pH 4.5-5.0).

138
Q

What pH can lysosomes not function in?

A

pH = 7.2

139
Q

How is the H+ gradient of lysosomes maintained?

A

Maintained by membrane-bound H+ ATPases.

140
Q

What are the two functions of the H+ gradient in lysosomes?

A

Maintains low pH. Provides energy for molecular transport across membrane.

141
Q

What is the step by step of Lysosomal Pathways?

A

trans-Golgi -> vesicles containing enzymes -> early endosomes -> late endosomes -> lysosomes.

142
Q

What occurs during Lysosomal Pathways?

A

Hydrolytic enzymes delivered to lysosomes from trans-Golgi.

143
Q

What is the definition of depolarization?

A

Inside of a cell becomes less negative.

144
Q

What is an action potential initiated by? What does it initiate?

A

Initiated by extracellular stimulus. Initiates a local depolarization.

145
Q

Where does the depolarization event move along in an action potential?

A

Moves along underside of the membrane.

146
Q

What is the definition of an action potential?

A

An electrical signal which has the potential to perform some action.

147
Q

Describe the mechanism in a nerve cell.

A

Extracellular stimulus causes depolarization. Threshold is met. Voltage-gated Na+ channels open. Na+ enters cell (down its gradient). Leads to further depolarization “downstream.” Downstream voltage-gated Na+ channels open.

148
Q

As Eukaryotic cells advanced, what system arose?

A

System of Membranes/Compartmentalization

149
Q

What are the three compartments associated with Eukaryotic compartmentalization?

A

Nucleus, Cytoplasm, and Cytosol

150
Q

The cytoplasm refers to what region?

A

Everything outside of the nucleus.

151
Q

What are the two parts of the cytoplasm? What are their functions?

A

Cytosol (aqueous portion) and organelles (suspended within cytosol).

152
Q

What are the three “jobs” of the cytosol?

A

Molecular suspension. Where most protein synthesis takes place. Most cellular metabolism.

153
Q

T/F: Both eukaryotic and prokaryotic cells can rely on solely diffusion.

A

False, only prokaryotic cells can rely on only diffusion.

154
Q

In order to be considered topographically equivalent, spaces or membranes have two requirements. What are they?

A

Continuous OR Derived from the same source.

155
Q

What is one example of continuous topographically equivalent spaces?

A

Nucleus & Cytosol

156
Q

What are some examples of topographically equivalent components that are derived from the same source?

A

Organelle lumens. Extracellular space. Organelle membranes. Plasma membrane.

157
Q

T/F: Topographically equivalent organelle membranes and lumens that are derived from the same space ARE biochemically equivalent.

A

No, these membranes and spaces that are derived from the same source do not have the same biochemical makeup.

158
Q

What makes the nucleus and the cytosol continuous?

A

Small molecules, such as water or ions, can move freely between the nucleus and the cytosol.

159
Q

T/F: Membranes surrounding cellular components make systems not continuous and therefore not topographically equivalent.

A

True

160
Q

What is protein destination location determined by? Where can this be found?

A

Sorting signals contained within the amino acid sequence.

161
Q

Where is the default location of proteins?

A

Cytosol

162
Q

Which proteins contain no sorting signal?

A

Proteins that function freely in the cytosol.

163
Q

What are the two types of sorting signals?

A

Signal Peptide Sequences and Signal Patches.

164
Q

What are the characteristics of signal peptide sequences?

A

Continuous amino acid sequence (15-60 amino acids long). Tail that gives the “address label” of destination. Often removed upon arrival by signal peptidases.

165
Q

What are the characteristics of signal patches?

A

Specific arrangement of atoms resulting from tertiary structure integral to protein, not removed upon arrival.

166
Q

Transport between the nucleus and the cytosol requires what complex? What is its function and describe how this enables molecules to move through.

A

Nuclear Pore Complex (large assembly of nucleoporin proteins with a variety of shapes and properties). Small water soluble molecules diffuse easily, while proteins require a localization signal.

167
Q

Do proteins and ribosomal subunits remain fully folded or unfold during transport in Nuclear Pore Translocation?

A

They remain fully folded.

168
Q

What protein mediates Nuclear Pore Translocation?

A

Ran-GTPase.

169
Q

Describe the mechanism of Nuclear Pore Translocation.

A

Nuclear Import/Export Receptor Protein recognizes the nuclear or cytosolic localization signal (NLS or CLS) on protein to be transported. Receptor binds to the signal and carries the protein to the destination. Nuclear import receptors recognize families of structurally similar proteins.

170
Q

Ran-GTPase exists as what two forms?

A

GTP-bound or GDP-bound.

171
Q

Of these four options, which two are located only in the cytosol? Which are located in the nucleus?

Ran-GAP. Ran-GEF. Ran-GTP. Ran-GDP.

A

Cytosol - Ran-GAP and Ran-GDP.
Nucleus - Ran-GEF and Ran-GTP.

172
Q

How does the function of Ran-GTP and Ran-GDP change based on the location?

A

When it cycles into the cytosol, it becomes the GDP-form. When it moves into the nucleus, it becomes the GTP-form.

173
Q

Transmembrane transport refers to movement between what types of spaces? What is an example of this type of movement?

A

Non-topographically equivalent spaces. Movement from the cytosol into organelles such as the endoplasmic reticulum, mito, plastids, peroxisomes.

174
Q

What is one required component of Transmembrane Transport? Describe the mechanism using this component.

A

Requires protein translocators, which are transmembrane organelle proteins. The transported protein is unfolded and delivered through this translocator, then refolded upon arrival.

175
Q

What are the two sources of energy for Transmembrane Transport?

A

Whole process uses ATP hydrolysis for energy. Electrical difference between cytosol also helps push proteins through.

Cell Biology (2 decks)

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