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My MCAT Biology > Eukaryotic Cells > Flashcards

Eukaryotic Cells Flashcards

1
Q

Organelles

A

Small structure within a cell that carries out specific cellular functions

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2
Q

Nucleus function and number of membranes surrounding

A

Contain & protects DNA, transcription and partial assembly of ribosomes

2

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3
Q

Mitochondria function and number of membranes surrounding

A

Produce ATP via the Kreb cycle and oxidative phosphorylation

2

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4
Q

Ribosomes function and number of membranes surrounding

A

Synthesize proteins

0

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5
Q

RER function and number of membranes surrounding

A

Location of synthesis/modification of secretory, membrane-bound and organelle proteins

1

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6
Q

SER function and number of membranes surrounding

A

Detoxification and glycogen breakdown in liver; steroid synthesis in gonads

1

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7
Q

Golgi apparatus function and number of membranes surrounding

A

Modification and sorting of proteins, some synthesis

1

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8
Q

Lysosomes function and number of membranes surrounding

A

Contain acid hydrolyses which digest various substances

1

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9
Q

Peroxisomes function and number of membranes surrounding

A

Metabolize lipids and toxins using peroxides (h2o2)

1

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10
Q

The nucleus contains the genome and is surrounded by the

A

Nuclear envelope

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11
Q

Nuclear envelope

A

separates the contents of the nucleus into a distinct compartment, isolated from other organelles and the cytoplasm

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12
Q

In eukaryotes, _____, ____ and ____ occur in the nucleus while ____ occurs in the cytoplasm

A

replication, transcription, and splicing occur in N

translation occurs in C

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13
Q

Genome is so large in humans that it is split into pieces, each a separate linear DNA molecule called

How many are there in humans

A

Chromosomes

23

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14
Q

Since humans and animals are diploid,

A

have 2 copies of each chromosome

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15
Q

Chromosomes have a _____ in the center to ensure that they are properly replicated during cell division… one copy to each daughter cell

A

Centromere

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16
Q

Each chromosome also has special structures at both ends termed ______ which have large numbers of repeats of specific DNA sequence and with the help of a special DNA poly termed _____ , __________ during DNA replication

A

Telomeres

Telomerase, which maintains the ends of linear chromosomes

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17
Q

Locus

A

Specific location on the chromosome where the gene resides allowing gene regulation

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18
Q

Heteochromatin

A

Densely packed chromatin within which genes are inaccessible and turned off

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19
Q

Euchromatin

A

More loosely packed into chromatin and allow genes to be activated

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20
Q

Nuclear matrix/nuclear scaffold

A

Attached to DNA chromosomes and modifies gene expression via access to promoters and enhancers to discrete chromosomal regions known as domains

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21
Q

Nuclear matrix is attached to DNA chromosomes and modifies gene expression via access to promoters and enhancers to discrete chromosomal regions known as ______

A

Domains

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22
Q

Nucleolus

A

Ribosome factory

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23
Q

There is ____ membrane separating the nucleolus from the rest of the nucleus

A

no

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24
Q

The nucleolus consists of

A

loops of DNA, RNA poly, rRNA and protein components of ribosome

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25
Q

The nucleolus is the site of transcription of ___ and ___

A

rRNA and RNA poly I

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26
Q

The ribosome is partially assembled in the nucleolus, the protein components are _____ .

After partial assembly the ribosome is exported from the nucleus, remaining ____ until ______ in the _____ .

This may serve to prevent

A

transported in from the cytoplasm

Inactive until assembly is completed in the cytoplasm

Translation of hnRNA

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27
Q

The nuclear membrane has two two lipid bilayer membranes. The inner nuclear membrane surface faces _____ and the outer surface faces ______

A

Surface of the envelope facing the nuclear interior

Surface faces cytoplasm

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28
Q

The membrane of the ____ is at points continuous with the outer nuclear membrane. This makes the interior of the ____ (____) contiguous with the space between the two nuclear membranes

A

Endoplasmic reticulum

ER (lumen on the ER)

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29
Q

The nuclear envelope has many ______ that allow passage of material into and out of the nucleus

What can pass?

A

Nuclear pores

Small molecules (less than 60kD) and proteins can freely diffuse, but larger proteins cannot pass freely through the pores and are excluded from the nucleus unless they are AA sequence

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30
Q

Nuclear localization sequence

A

AA sequence of a large protein trying to pass through nuclear pores

Translated on cytoplasmic ribosomes and then imported into the nucleus via specific transport mechanisms

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31
Q

In addition to nuclear localization sequences, ___ is transported out of the nucleus by a specific transport mechanism rather than _____

A

RNA

Freely diffusing

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32
Q

Mitochondria are the site of ______

A

Oxidative phosphorylation

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33
Q

Matrix of the mitochondria

A

Bounded by inner and outer membranes and contains pyruvate dehydrogenase and enzymes of the Krebs cycle

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34
Q

Inner membrane of the mitochondria

A

Impermeable to the free diffusion of polar substances, like proteins, and is folded into the matrix in projections called cristae

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35
Q

Inner membrane of the mitochondria is impermeable to the free diffusion of polar substances, like proteins, and is folded into the matrix in projections called

A

Cristae

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36
Q

The outer membrane of the mitochondria is

A

Smooth and contains large pores that allow free passage of small molecules

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37
Q

Space between inner and outer membranes of the mitochondria is called

A

Intermembrane space

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38
Q

ATP produced within mitochondria is

A

Transported out into the cytoplasm to drive a greater variety of cellular processes

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39
Q

Mitochondria process their own genome which is ___ and ____

A

Much smaller than the cellular genome and consists of a single circular DNA molecule that encodes rRNA, tRNA and proteins (of the Electron transport chain/ATP synthase complex)

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40
Q

To explain that mitochondria possess a second system of inheritance, researchers suggest they

A

Originated as an independent unicellular organism living within larger cells

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41
Q

Endosymbiotic theory of mitochondrial evolution

A

To explain that mitochondria possess a second system of inheritance, researchers suggest they originated as an independent unicellular organism living within larger cells

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42
Q

Mitochondria exhibit maternal inheritance meaning

A

The mitochondria are inherited only from the mother, since the egg cytoplasm becomes the zygote cytoplasm

The sperm contributes only genomic (nuclear) DNA

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43
Q

The ER is a large system of folded membrane that accounts for

A

over half of the cell membrane

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44
Q

Rough ER is rough due to

A

Large number of ribosomes bound to its surface

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45
Q

Rough ER is the site of

A

Protein synthesis for proteins targeted to enter the secretory pathway

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46
Q

Smooth ER contains

A

enzymes involved in steroid hormone biosynthesis (gonads) or degradation of environmental toxins (liver)

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47
Q

The rough ER plays a key role in

A

directing protein traffic to different parts of the cell

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48
Q

Proteins translated on the free cytoplasmic ribosomes are headed towards

A

Peroxisomes, mitochondria, nucleus or cytoplasm

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49
Q

Proteins translated on the rough ER are headed towards

A

extracellular environment, plasma membrane, or membrane/interior of Golgi, ER, or lysosomes

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50
Q

Proteins synthesized on the rough Er are transported in vesicles that bud from the ER to the ____, then to the ____ or _____

A

Golgi apparatus

plasma membrane or lysosome

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51
Q

How is it determined which location the protein is translated on?

A

All start in cytoplasm, some have an AA signal sequence at N-terminus that tells them to go to the RER

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52
Q

The AA signal sequence is recognized by

A

Signal recognitions particle (SRP) which binds to the ribosome

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53
Q

The RER has SRP receptors to dock the AA signal sequence bearing protein on the RER membrane. When the protein is translated,

A

the polypeptide is pushed into the ER lumen (signal peptide first)

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54
Q

After translation is complete, the signal peptide is ____ by a ____ in the ____

A

removed by a signal peptidase in the ER lumen

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55
Q

For secreted proteins, once the signal sequence is removed the protein is transported to the

A

Interior of vesicles through the Golgi apparatus to the plasma membrane where it is released by exocytosis into the extracellular environment

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56
Q

Integral membrane proteins have

A

Sections of transmembrane domains that are signal sequences found on interior of protein (not N-terminus)

Not removed after translation

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57
Q

Transmembrane domains

A

hydrophobic AA residues that pass through lipid bilayer membranes

Not removed after translation

Observed on interior of protein

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58
Q

During translation, transmembrane domains are

A

threaded through the ER membrane and the protein is transported in vesicles to the Golgi apparatus and plasma membrane in same manner as a secretory protein

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59
Q

Additional functions of the rough ER include the initial post-translational modification of proteins… some ____ occurs in the rough ER, though it is usually associated with the Golgi apparatus

A

Glycosylation (adding saccharides to proteins)

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60
Q

Also in the ER Lumen to modify proteins post translation, ___ occurs

A

Disulfide bond formation

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61
Q

Default target for proteins going through the secretory path is the

A

Plasma membrane

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62
Q

Targeting signals are needed if a

A

protein going through the secretory path to the plasma membrane needs to be going elsewhere (i.e. the Golgi, ER or lysosome)

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63
Q

Proteins made in the cytoplasm that need to be sent to an organelle that isn’t in the secretory path (nucleus, mitochondria or peroxisomes) require

A

localization signals

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64
Q

Protein final destination: Secretory

Signal Sequence?
Localization Sequence?
Transmembrane Domains?
Targeting Signal?

A

Y
N
N
N

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65
Q

Protein final destination: Plasma membrane

Signal Sequence?
Localization Sequence?
Transmembrane Domains?
Targeting Signal?

A

Y
N
Y
N

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66
Q

Protein final destination: Lysosome

Signal Sequence?
Localization Sequence?
Transmembrane Domains?
Targeting Signal?

A

Y
N
N
Y

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67
Q

Protein final destination: Rough ER

Signal Sequence?
Localization Sequence?
Transmembrane Domains?
Targeting Signal?

A

Y
N
N
Y

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68
Q

Protein final destination: Smooth ER

Signal Sequence?
Localization Sequence?
Transmembrane Domains?
Targeting Signal?

A

Y
N
N
Y

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69
Q

Protein final destination: Golgi apparatus

Signal Sequence?
Localization Sequence?
Transmembrane Domains?
Targeting Signal?

A

Y
N
N
Y

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70
Q

Protein final destination: Cytoplasm

Signal Sequence?
Localization Sequence?
Transmembrane Domains?
Targeting Signal?

A

N
N
N
N

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71
Q

Protein final destination: Nucleus

Signal Sequence?
Localization Sequence?
Transmembrane Domains?
Targeting Signal?

A

N
Y
N
N

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72
Q

NProtein final destination: Mitochondria

Signal Sequence?
Localization Sequence?
Transmembrane Domains?
Targeting Signal?

A

N
Y
N
N

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73
Q

Protein final destination: Peroxisome

Signal Sequence?
Localization Sequence?
Transmembrane Domains?
Targeting Signal?

A

N
Y
N
N

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74
Q

Golgi apparatus functions (3)

A
  1. Modifies proteins made in RER (esp. oligosaccharides)
  2. Sorting and sending proteins to destinations
  3. Synthesizes macromolecules for secretion such as polysaccharides
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75
Q

Vesicle traffic to Golgi is ____

A

Unidirectional

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76
Q

The membrane bound or secreted proteins which are to be sorted/modified enter / exit the Golgi at

A

enter at one defined region and exit at another

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77
Q

Retrograde traffic

A

Opposite of unidirectional traffic occurs when protein escapes rough ER and must be put back by the golgi

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78
Q

Cis stack of golgi

A

Nearest rough ER

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79
Q

Proteins from the Cis stack are modified and transferred to the ___ where they are:

A

Medial stack where they are further modified

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80
Q

After the medial stack modifies the proteins they are sent to the

A

Trans stack where they leave in transport vesicles

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81
Q

The route taken by a protein is determined by its

A

signals within the protein that determine which vesicle a protein is stored into in the trans Golgi

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82
Q

Lysosome function

A

degradation of biological macromolecules by hydrolysis

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83
Q

Lysosome proteins are made in the ___, modified in the ____ and released in their final form in the ____

A

RER

Golgi

Golgi trans

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84
Q

Organelles that are no longer functional

A

can be degraded in the lysosome

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85
Q

Autophagy

A

Organelles that are no longer functional can be degraded in the lysosome.

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86
Q

Phagocytosis

A

Lysosomes degrade large particulate matter engulfed by the cell

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87
Q

Macrophages

A

In immune system engulfs bacteria and viruses

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88
Q

Phagocytic vesicle

A

Particles that are engulfed end up here and then are fused with a lysosome

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89
Q

After hydrolysis, the lysosome releases molecular

A

building blocks for reuse into the cytoplasm

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90
Q

Enzymes responsible for degradation in lysosomes are called

A

Acid hydrolyses

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91
Q

Acid hydrolases

A

Enzymes responsible for degradation in lysosomes only in ACIDIC environment

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92
Q

Acid hydrolyses are used as a safety mechanism. The pH of the lysosome is __ so the ___ because the pH of the cytoplasm is ___.

Therefore If the lysosome ruptures will the cell be damaged?

A

5

acid hydrolyses are in action

7.4

No because the acidic fluid will be diluted and the acid hydrolyses will be inactivated, however if many rupture at once the cell can be destroyed

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93
Q

Peroxisomes function

A

Variety of metabolic tasks

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94
Q

Peroxisomes contains enzymes that produce

A

hydrogen peroxide as byproducts

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95
Q

Peroxisomes are essential for ____

A

lipid breakdown

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96
Q

In the liver, peroxisomes assist with

A

detoxification of drugs and chemicals

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97
Q

H2O2 is a dangerous chemical so how does it exist as a byproduct in the peroxisome?

A

Peroxisomes contain an enzyme catalase which converts it to water and oxygen

Separation this activity into the peroxisomes prevents the cell from getting damaged by peroxides or oxygen radicals

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98
Q

Animals rely on ____ and a ____ to keep their structure and differentiate between the inside and outside of the cell

A

Cell membrane

Cytoskeleton

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99
Q

All membranes of the cell are composed of

A

Lipid bilayer membranes

100
Q

Three most common lipids is eukaryotic membranes

A

(#1 Phospholipids), glycolipids and cholesterol

101
Q

Phospholipids and glycolipids both have two portions that are distinctly

A

Hydrophilic and hydrophobic

102
Q

In water, phospholipids arrange themselves spontaneously into ____ which is

A

lipid bilayer membrane

lowest energy state for the molecules so they can reseal and repair if a small portion is removed

103
Q

The interior of the membrane is very ______, molecules such as ions, carbohydrates, and amino acids are ______ because they are ______ and molecules such as CO2, O2 and steroid hormones are _____ because they are ______

Water passes through the membrane via _____

A

Hydrophobic

I,C,AA: impermeable because they are polar

C,O,SH: permeable because non polar

Specialized protein channels

104
Q

Hydrophobic component of the phospholipid plasma membrane is ____ and hydrophilic component is ____

A

Hydrophobic: tails
Hydrophilic: heads

105
Q

Mitochondrial membrane is different in that it has

A

More proteins than lipids

106
Q

Cell-surface receptors

A

Proteins that bind extracellular signaling molecules such as hormones and relay these signals into the cell

107
Q

Channel proteins

A

Selectively allow ions or molecules to cross the membrane

108
Q

Integral membrane proteins

A

Embedded into the membrane by hydrophobic interactions

109
Q

Transmembrane domains

A

Membrane crossing regions

110
Q

Peripheral membrane proteins

A

Not embedded in the membrane; Stuck into the integral membrane proteins, held by hydrogen bonding and electrostatic interactions

111
Q

Fluid Mosaic Model

A

Lipids and portions making up the membrane are free to move back and forth fluidly, to diffuse laterally but not free to flip-flop

Move in 2D only

112
Q

In the Fluid Mosaic Model, the membrane is not allowed to flip-flop meaning that

A

The membrane is polar because the inside and outside face remain different

113
Q

One exception to the Fluid Mosaic Model

A

Some proteins are held in the cytoskeleton and therefore cannot move in any direction

114
Q

Van der Waals interactions are a good determinant of membrane fluidity

The saturated fatty acids (lacking double bonds) have a very straight structure and are packed tightly in the membrane with: ___ VDW forces & fluidity ___

Unsaturated fatty acids, with one or more double bonds, have a kinked structure and are packed loosely: ____ VDW forces & fluidity ____

A

Saturated is strong and fluidity is low

Unsaturated is weak and fluidity is high

115
Q

____ also plays a key role in maintaining optimal membrane fluidity

A

Cholesterol

116
Q

Passive vs active transport

A

Passive requires no cellular energy and active does require cellular energy

117
Q

Electrolytes

A

Free ions in a solution dissociated from their substance

118
Q

Strong-electrolytes vs weak-electrolytes vs non-electrolytes

A

S: Dissociate completely into solution

W: Some dissociation

N: Covalent bonds that don’t dissociate at all

119
Q

Van’t Hoff Ionizability factor

  • C6H12O2
  • NaCl
  • HNO3
  • CaCl2
A

How many ions a substance prod in solution

  • i=1 because it is non-ionic
  • i=2 because it is ionic
  • i=2 because H and NO3
  • i=3 because it is Ca and Cl, Cl
120
Q

Colligative properties depend on

A

Number of solute particles, not the type or identity of particles

121
Q

Vapor-Pressure

A

Pressure exerted by the gaseous phase of a liquid that evaporated

122
Q

___ IMF, higher VP, ___ evaporation

A

weaker IMF, higher VP, more easy to evaporate

123
Q

Volatile liquids

A

High VP, easy to evaporate, IMF easy to overcome

124
Q

What happens to vapor pressure when a compound is dissolved in solution?

A

The VP goes down because there are more forces to be broken (compound is attracted to solution “anchors”)

Vapor pressure depression

125
Q

Boiling point definition

A

Temp at which the VP is equal to the atmospheric pressure over the solution

126
Q

Adding more solute to a solution ill ___ VP

A

Decrease

127
Q

What happens to boiling point when a compound is dissolved in solution?

A

The BP goes up because more energy is required to break the additional bond to the anchor molecules

128
Q

Boiling point elevation equation

A

Change in BP = k (solution bp elevation constant) x i (ionizability factor) x m (molar concentration)

k for water is 0.5

129
Q

What happens when you add a solute to a liquid and freeze it?

A

Presence of solute will interfere with efficient arrangement of solvent molecules into solid lattice that maximizes IMF

As a result, liquid will be less able to achieve the solid state and will have a lower freezing point

FP GOES DOWN

130
Q

Freezing Point Depression Equation

A

Change in BP = - k (solution bp elevation constant) x i (ionizability factor) x m (molar concentration)

Same as BP elevation but with a minus sign

Water k= 1.9

131
Q

Diffusion

A

Tendency for liquids and gases to fully occupy the available volume

132
Q

If all particles are concentrated in one section we have an orderly arrangement which is

A

Unfavorable acc to the law of entropy

133
Q

A solution will always diffuse

A

Down its gradient from high to low concentration until evenly distributed throughout the available volume and non net movement will continue (back and forth does continue)

134
Q

Osmosis

A

Solvent diffuses rather than a solute

Net movement of water from a region of low solute conc to high solute conc in an effort to dilute the higher conc

135
Q

If sucrose and water are each in one half of a container and allowed to diffuse this process is called: ___ and this will happen:

If there is a semipermeable membrane that allows water but not sucrose then:

Membrane is semipermeable meaning

A

Osmosis

Sucrose and water will move until both sides has equal concentration of both

Diffusion of sucrose between the chambers cannot occur and osmosis draws water into the sucrose chamber to reduce the sucrose concentration as well as the volume in the water chamber (ignoring gravity water will flow in until the concentration of sucrose is even cross the membrane)

Water can cross via osmosis but not most polar molecules

136
Q

Tonicity describes

Isotonic/isoosmotic:
Hypertonic/hyperosmotic:
Hypotonic/hypoosmotic:

A

Osmotic gradients

I: Solute concentration is the same inside and outside
Hyper: More total dissolved solutes than the cell
Hypo: Less total dissolved solute than the cell

137
Q

Osmotic pressure

A

Pressure to stop osmosis from occurring

138
Q

Osmotic pressure equation (van’t Hoff equation)

A

Osmotic pressure (atm) = M (molarity) x i (ioniziabilty factor) x 0.0821 x T (K)

139
Q

Osmotic pressure are affected only by the ___ not the ___

A

Number of particles not the identity

140
Q

Passive transport

A

Any thermodynamically favorable movement of electrons of solute across a membrane

Movement down a gradient no energy required

141
Q

Simple diffusion

A

Without help from a protein solute moves through a membrane

Non-polar, hydrophobic compounds

142
Q

Facilitated diffusion

A

Movement of solute across a membrane when the solute is initially impermeable through the membrane

Only down conc gradient

143
Q

Channel and carrier proteins do which type of diffusion?

Channels and carriers give the membrane its primary function of:

A

Facilitated

Selective permeability to some things despite impermeability to most things

144
Q

Ion channels only allow

A

One type of ion to flow

Highly selective

145
Q

Gated ion channels

A

If the channel is open in response to certain environmental stimuli

146
Q

Voltage-gated channel

A

Opens in response to changes in electrical potential across a membrane

147
Q

Ligand-gated channel

A

Opens in response to binding of a specific molecule

148
Q

Can ion channels move ions against an electrochemical gradient

A

No only facilitated diffusion

149
Q

Carrier proteins: how do they transport molecules across the membrane

A

Bind the molecule and then undergo a conformational change to move it to the other side

150
Q

Uniports

A

Transport only one molecule across the membrane at a time

151
Q

Symports

A

Transport two substances across a membrane in the same direction

152
Q

Antiports

A

Carry two substances in opposite directions

153
Q

Pore

A

Tube through a membrane that is so large it is not selective for any particular molecule, but instead all molecules of a certain size can pass

Sensitive to size and charge

154
Q

Pores are formed by _____

A

Polypeptides known as porins

155
Q

Eukaryotes do not have pores because

A

Pores destroy the barrier function of the membrane, allowing solutes into the cytoplasm to freely diffuse out of the cell

156
Q

Rate of simple diffusion is limited only by the ___ and ___

The rate of facilitated diffusion is limited by ____

A

Surface area of the membrane and the size of the driving force/gradient

Finite number of integral proteins (saturation kinetics)

157
Q

Facilitative diffusion exhibits saturated kinetics meaning when the driving force for facilitated diffusion increases,

A

the rate of diffusion (flux) increases, but only until a certain point when all the transport proteins are saturated and no further increase in flux is possible

158
Q

Active transport

A

Moving molecules across their gradient (conc or charge, etc.)

Requires energy input
Always involves a protein

159
Q

Primary active transport

A

Molecule transport coupled to ATP hydrolysis

160
Q

Secondary active transport

A

ATP is used to create a gradient and then the potential energy of the gradient drives the transport of some other molecule across the membrane which in turn powers secondary active transport

ATP is an indirect here

Uses another molecules diffusion across gradient to power its diffusion

161
Q

Na+/K+ ATPase is a transmembrane protein in all cells of the human body

Activity is to pump: ___ and in the process to ___

A

3 Na+ out and two K+ in

Hydrolysis one ATP

162
Q

Na+ pumped out ____ and K+ pumped in ____ due to ____

A

Na+ stays out (membrane is impermeable)

K+ some goes out some stays in (K+ leak channels)

163
Q

Potassium leak channels

A

K+ flows down its gradient and out of the cell through these channels to help maintain osmotic balance and creates a net negative charge since + is leaving the cell (resting membrane potential)

164
Q

Driving force between secondary active transport of many molecules including sugars and AA

A

Concentration gradient of high Na+ outside the cell established but he Na+/K+ ATPase

165
Q

What would the RMP be in a cell with Na+/K+ ATPase but no K+ leak channels?

A

-10mV determined experimentally because the resting membrane potential is only determined by the electrogenecity of the NaK pump

166
Q

Conc inside and outside the cell for

Na+:
K+:
Cl-:
Ca2+:

A

Na: MORE out
K: MORE in
Cl-: MORE out
Ca2+: MORE out

167
Q

Exocytosis

A

Transporting material outside of the cell via a vesicle in the cytoplasm fuses with the membrane and the contents are expressed into the extracellular space

I.e. hormones, digestive enzymes

168
Q

Endocytosis

A

Materials are taken into the cell by an invagination of a piece of the cell membrane to form a vesicle

Cytoplasm is not allowed to mix with extracellular environment

New vesicle is formed: endosome

169
Q

Endosome

A

New vesicle formed via endocytosis

170
Q

Phagocytosis

A

Cell eating

Nonspecific uptake of large particulate matter into a phagocytic vesicle which will merge with a lysosome

Phagocytosed material will be broken down

NOT INVAGINATION
i.e. macrophages

171
Q

Pinocytosis

A

Cell drinking

Nonspecific uptake of small molecules and extracellular fluids via invagination

172
Q

Receptor-mediated endocytosis

A

Specific

Site is marked by receptors (outside cell) and clathrin coating (inside cell)

173
Q

Clathrin

A

Used to mark sites for receptor-mediated endocytosis

Does not bind to the molecules to undergo uptake but does interact with the cell-surface of receptors

174
Q

Signal Transduction

A

Binding of ligand to receptor initiates a response within the cell

175
Q

Ligand Gated Ion Channels

A

open ion channel after binding a specific NT

176
Q

Catalytic Receptors

A

enzyme active site on cytoplasm side of the membrane

enzyme activity is initiated by a ligand binding to the extracellular receptor surface

177
Q

G-protein Linked Receptor

A

Transmits signal through a second messenger which is a chemical signal that relays instructions from the cell surface to enzymes in the cytoplasm and creates a much larger effect than a receptor alone would

178
Q

Most important second messenger

G-protein is a signaling molecule which binds

A

cAMP

GTP

179
Q

Signal Transduction

A

continuing a signal across a membrane

180
Q

Eukaryote equivalent of the cell wall

A

Cytoskeleton

181
Q

Function of the cytoskeleton:

A

Movement, transport of substances in the cell and structural support

182
Q

Microtubules, intermediate filaments and microfilaments which is thickest/thinnest? What are they all made of?

A

Microfilaments are thinnest
Microtubules are thickest

All made of non-covalently polymerized proteins (massive quaternary structure)

183
Q

Microtubule is a hollow row composed of two globular proteins: alpha-tubulin and beta-tubulin

Once formed, the microtubule can elongate by:

A

Adding ab-tubulin dimers to one end, the other end cannot elongate because it is anchored to the microtubule organizing center (MTOC) near the nucleus

Dynamic and can get longer or shorter by adding tubular monomers to one end

184
Q

Within the MTOC (place the microtubule cannot elongate) is a pair of

A

Centrioles

185
Q

Mitotic Spindle

A

Microtubules radiate out of the centrioles during mitosis (aster)

polar fibers connecting the chromosomes to the aster

186
Q

The centromere of each chromosome contains: A kinetochore

A

Attached to the spindle by tiny microtubules called kinetochore fibers

187
Q

In mitosis the MTOC is essential but the centrioles are not.

What is the two major pieces of evidence for proving this?

A

Plants without centrioles undergo mitosis

Removing centrioles from animal cells and still undergo mitosis

188
Q

In nerve cells, materials are transported from the cell body to the axon terminus on a

A

Microtubule railroad

189
Q

Cilia

A

Small hairs on the cell surface which moves fluids past the cell surface

190
Q

Mucociliary escalator

A

Sweep mucus toward the mouth

191
Q

Flagellum

A

Large tail which moves the cell by wiggling

192
Q

The only cell with a flagellum is the

A

Sperm

193
Q

Cilia and flagellum have the same structure __ + __

Which is:

A

9+2

9 pairs of MT form a ring around two lone MT in the center

194
Q

Each MT in the 9+2 arrangement is bound to its neighbor by a

A

contractile protein called dynein (movement of filament past one another)

195
Q

The cilia or flagella (E only) is bound to the plasma membrane by a

A

basal body which has the same structure as a centriole (9 triplet ring)

196
Q

Microfilaments

A

Rods formed in the cytoplasm from protein “actin”

197
Q

Actin monomers form a chain, and then two chains wrap around each other to dorm a

A

filament

198
Q

MF are dynamic and are responsible for

A

Gross movement of the entire cell such as pinching the cell in division and amoeboid movement

199
Q

Amoeboid movement

A

Changes in the cytoplasmic structure which causes cytoplasm and the rest of the cell to move in one direction

200
Q

Intermediate filament

A

Named for thickness, between MT and MF

Heterogeneous, wide range of polypeptides

Provide cell structure and are more permanent

201
Q

Tight Junctions (aka Occluding Junctions)

A

Cells forming a tight seal preventing items from moving freely between the two cells

A band around the membrane not a spot on it

202
Q

Desmosomes (aka Spot Desmosomes)

A

Held together tightly but do not form a seal

Points not a band

203
Q

Gap junctions

A

Allow ions to flow back and forth between them

204
Q

Apical vs. basolateral surface

?

A

Apical: facing outside

Basolateral surfac: facing inside contents

205
Q

Inside each cell the desmosomes are anchored to the plasma membrane by the protein

A

keratin

206
Q

Gap junctions are large enough to allow flow of:

But too small to allow:

A

Can pass AA, ions and carbs

Not pass organelles and polypeptides

207
Q

Gap junctions in smooth and cardiac muscle allow the membrane to ______

A

depolarize AP to pass directly from one cell to another

208
Q

Cells reproduce themselves by first _____ and then splitting in half

A

Doubling everything in the cytoplasm and genome

209
Q

Synthesis (S) phase

A

When the cell activity replicates its genome

210
Q

M phase

A

Mitosis and cytokinesis

211
Q

Mitosis is

A

partitioning of cellular components into two halves

212
Q

Cytokinesis

A

Physical process of cell division

213
Q

Between M and S phases there are two gap phases:

A

G1 and G2

214
Q

Interphase

A

G1, G2 and S phase

215
Q

The cell spends most of its time in

A

Interphase

Metabolizing and synthesizing materials

216
Q

Some cells become permanently stuck in

A

Interphase

217
Q

More specialized a cell comes, the less likely it is to

A

Come out of interphase and replicate

218
Q

During interphase, the genome is

A

Spread out and DNA is accessible to the enzymes of replication

219
Q

By the end of the S phase the nucleus contains

A

Two copies of the genome (2x the normal amount of DNA)

220
Q

Mitosis is divided into 4 phases:

A

Prophase, metaphase, anaphase and telophase

221
Q

First sign of prophase

A

Genome into densely packed chromosomes instead of diffuse chromatin

Sister chromatids

222
Q

When mitosis Is complete, each new daughter cell will have ___ chromosomes each consisting of a single chromatid, separated from its sister

A

23 homologous pairs of identical chromosomes (23 pairs of pairs)

223
Q

Difference between homologous chromosomes and sister chromatids

A

HC: equal but not identical, not attached
SC: identical, connected at the centromere

224
Q

During prophase what occurs

A

Genome packed into chromosomes, nucleolus disappears, spindle and kinetochore fibers appear and the centriole pairs begin to move to opposite ends of a cell

225
Q

After prophase the cell has

A

2 MTOC’s called asters and the nuclear envelope converts itself into many tiny vesicles

226
Q

Metaphase

A

Chromosomes line up at center of the cell forming the metaphase plate, each member of the chromatid pair is pulled toward the opposite pole of the cell

227
Q

Anaphase

A

Spindle fibers shorten and centromeres of each sister chromatid pair are pulled apart

Cell elongates and cytokinesis beings with cleavage furrow (ring of actin filaments encircle and contract)

228
Q

Cleavage Furrow

A

Ring of actin filament encloses and contracts

229
Q

Telophase

A

Chromosomes de-condense and a nucleolus appears in each daughter cell

Each daughter cell has 2n chromosomes

230
Q

Oncogenes

A

Cells needed for growth and regulation of the cell cycle that have become mutated & can cause cancers

231
Q

Protooncogenes

A

Normal version of the genes that allow for regular growth patterns but can be converted into oncogenes due to mutation or exposure to a mutagen

232
Q

Tumor supressor genes

A

Produce proteins that are the inherent defense system to prevent conversion of cells into cancer

233
Q

2 primary means of cancer protection

A
  1. detect damage to the genome and halt cell growth and division until repair
    2 trigger programmed cell death if the damage is too severe to be repaired
234
Q

Common tumor suppressor gene: ___

Though normally at low levels in the cell, its production is

A

p53

Scaled up when genetic damage occurs or oncogene activity is detected

If repair is too far gone, the p53 will cause the cell to go into apoptosis

235
Q

Apoptosis

A

Allows cell to shrink and die while simultaneously minimizing damage to nearby cells and limiting exposure of cytosolic contents

236
Q

The death of a cell is triggered by

A

internal or external stressors

237
Q

Process of apoptosis

A

Cell shrinks, cytoskeleton dissembles, nuclear envelope breaks down and genome is broken into pieces, phagocytes finish deconstructing and clearing the dead cell

238
Q

Caspases

A

Carries out events of apoptosis

Cleave target proteins

239
Q

Caspases are produced in their

A

Inactive form as procapases

240
Q

Initiator caspases

A

Respond to extra or intra cellular death signals by clustering together to activate one another

241
Q

Effector caspases

A

Are activated in an amplification cascade after the initiation caspases are activated

Responsible for cleaving cellular proteins to trigger apoptosis

242
Q

Senescene

A

Biological aging occurring at both the cellular and organismal level

243
Q

In E, ____ is a measure of cellular age

A

Length of telomeres

244
Q

As cells age, they become prone to

A

apoptosis to remove cells due to age

245
Q

Cumulative effects of senescene lead to aging of entire organism… functioning of the organism is effected to the point at which

A

The body stops working and death occurs

My MCAT Biology (13 decks)

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