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MCAT biology Flashcards

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1
Q

What are the three physiological rooles of lipids?

A
  • Triglycerides store energy
  • Phospholipids constitute barrier between intra and extracellular environment
  • Cholesterol is the building block for hydrophobic steroid hormones
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2
Q

Why are fats more efficient energy storage molecules than carbohydrates?

A
  • Packing: Their hydrophobicity allows fats to pack together much more closely than carbohydrates
  • Energy content: Fat molecules store much more energy than carbohydrates. More energy carbon-for-carbon than a carbohydrate
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3
Q

The lipid bilayer of phospholipids are stabilized by ___

A

van der Waals forces between the long tails

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4
Q

What are the structural determinants of lipid membrane fluidity?

A
  • Degree of saturation
  • Tail length
  • amount of cholesterol
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5
Q

___is a triterpene and important in the synthesis and manufacturing of steroids, also a component of ear wax

A

Squalene, made of six isoprene units

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6
Q

What are the three reasons that phosphate anhydride bonds store so much energy?

A
  • When phosphates link, their negative charegs repel each other strongly
  • Orthophosphate has more resonance forms and thus a lower free energy than linked phosphates
  • Orthophosphate has a more favorable interaction with water than linked phosphates
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7
Q

Two phosphates are linked by a high-energy bond called a ___

A

anhydride linkage forming pyrophosphate

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8
Q

What type of glycosidic linkages can mammals digest?

A

Mammals generally can difest alpha glycosidic linkages, but generally not B linkages

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9
Q

Nucleotides in the DNA chain are covalently linked by ___

A

phosphodiester bonds between the 3’ group of one deoxyribose and the 5’ phosphate group of the next deoxyribose

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10
Q

Centromeres are made of ____ and ___

A

heterochromatin and repetitive DNA sequences

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11
Q

___is a region of a chromosome that spindle fibers attach to during cell division

A

Centromeres

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12
Q

Spindle fibers attach to the centromere via ___ a multiprotein complex that acts as an anchor attachment site for spindle fibers

A

kinetochores

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13
Q

A single piece of double-stranded DNA; part of the genome of an organism. In prokaryotes it is circular and eukaryotes it is linear

A

chromosomes

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14
Q

What is the purpose of DNA gyrase?

A

DNA gyrase is used in prokaryotes to break and tist the two sides of the circular prokaryotic DNA, this aids in packing prokaryotic DNA and making it more sturdy

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15
Q

__are variations in a single nucleotide from one person’s DNA gene sequence to another’s. These minor mutations can produce changes in phenotype

A

Single nucleotide polymorphisms

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16
Q

___are regions of the genome where short sequences of nucleotides are repeated one after the other anywhere from 3 to 100 times

A

Tandem repeats

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17
Q

The enzymatic process of reading a strand of DNA to produce a complementary strand of RNA

A

Transcription

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18
Q

A structure made of two protein subunits, this is the site of protein synthesis (translation) in a cell

A

Ribosomes

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19
Q

What is the thermodynamic driving force for the polymerization and addition of nucleotides to new daughter DNA strands

A

The removal and hydrolysis of pyrophosphate (P2O7^4-)

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20
Q

___is repsonsible for super fast, super accurate elongation of the leading strand, NO KNOWN function in repair. Considered a replicative enzyme

A

DNA polymerase 3

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21
Q

___starts adding nucleotides at the RNA primer, it can only add 15-20 base pairs per second. It also removes the RNA primer and is very important in excision repair

A

DNA polymerase 1

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22
Q

During translation, the next codon to be translated is expose in the ___site

A

A site, since this is where the next amino acid to be added must bind

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23
Q

___is complementary to the pyrimidine-rich region on the samll subunit, helps position initiation machinery on the transcript for prokaryotes

A

Shile-Dalgarno sequence

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24
Q

What are differences between prokaryotic and eukaryotic translation?

A
  • the ribosome is larger (80s) and has different components than the prokaryotic ribosome
  • mRNA must be processed before it can be translated (spliced, with cap and tail added)
  • N terminal amino acid is different (Met instead of fMet)
  • mRNA must be transported from nucleus to cytoplasm to be translated, not simultaneous
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25
Q

Are the newly formed polypeptide chains emerging from a polyribosome in a eukaryote all the same?

A

UES, eukaryotic mRNA is monocistronic. In prokaryotes, different polypeptides may be translated from a single piece of mRNA

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26
Q

What two process may occur simultaneously on the same RNA molecule in a eukaryotic cell?

A

Transcription and splicing

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27
Q

___is the principle site of regulation of gene expression in both Eukaryotes and Prokaryotes

A

Transcripion

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28
Q

What are the two ways that DNA methylation turns off Eukaryotic gene expression?

A
  • physically blocks the gene from transcriptional proteins
  • Certain proteins bind methylated CpG groups and recruit chromatin remodeling proteins that change the winding of DNA around histones
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29
Q

Silencing of a certain gene involves ___,___and___

A
  • DNA methylation
  • Histone modification
  • binding of long ncRNA’s
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30
Q

In humans, X-inactivation occurs early in development, at the ___

A

blastocyst stage

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31
Q

What is the primary method of regulation of gene expression in Prokaryotes?

A

Regulation of transcription

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32
Q

The ___is an inducible

A

Lac operon

-Catabolic enzymes whose transcription can be stimulated by the abundance of a substrate are called inducible enzymes

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33
Q

The ___is repressible

A

trp operon is repressible

-Anabolic enzymes whose transcription is inhibited in the presence of excess amounts of products are repressible

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34
Q

What are the two components found in all operons

A
  • coding sequence for enzymes

- upstream regulatory sequence or control site

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35
Q

What are the 4 regions of the lac operon?

A
  • P site: the promoter site on DNA to which RNA polymerase binds to initiate transcription of Y,Z, and A genes
  • O region: the operator site to which the Lac repressor binds
  • Z genes: codes for the enzyme B-galactosidase
  • Y gene: code for permease, a protein which transports lactose into the cell
  • A gene: codes for transacetylase, an enzyme which transfers an acetyl group from acetyl-CoA to B-galactosides (not required for lactose metabolism)
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36
Q

What does the P region of the lac operon do?

A

P region is the promoter site on DNA to which RNA polyermase binds to initiate transcription of Y,Z, and A genes

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37
Q

What does the O region of the lac operon do?

A

The operator site to which the Lac repressor binds

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38
Q

What does the Z gene of the lac operon do?

A

The z gene codes for enzyme B-galactosidase, which cleaves lactose into glucose and galactose

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39
Q

What does the Y gene of the lac operon do?

A

Codes for permease, a protein which transports lactose into the cell

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40
Q

What are two genes that code for important proteins in the regulation of the lac operon?

A
  • Crp gene: located at a distant site, this gene codes for a catabolic activator protein (CAP)
  • I gene: located at a distant site, this gene codes for the Lac repressor protein
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41
Q

The ___gene codes for the lac repressor gene

A

I gene

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42
Q

The __lcodes for the catabolic activator protein (CAP) involved in the lac operon

A

Crp gene

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43
Q

If the operator is mutated so that the lac repressor can no longer bind, what effect will this have on transcription?

A

If the repressor cannot bind to the operator, RNA polymerase will transcribe all the genes on the operon continuously

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44
Q

___is a highly conserved DNA recognition sequence for the TBP, binding of TBP to this region initiates transcription complex assembly at the promoter in Eukaryotes

A

TATA box

TBP is tata box binding protein

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45
Q

IF a mutation in a eukaryotic fat cell reduces the level of several proteins related to fat metabolism, does this mean the proteins are encoded by the same mRNA?

A

No it does not. Eukaryotic mRNA is monocistronic. More likely number of genes located throughout the genome have regulatory sequences that bind the same specific transcription factors. This is the means used by eukaryotes to achieve coordinate expression of genes.

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46
Q

PRoteins that bind to enhancer sequences in eukaryotes to increase transcription

A

Activator proteins

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47
Q

A sequence of three nucleotides found in the antiocodon loop of tRNA, that is complementary to a specific codon in mRNA. The codon to which the anticodon is complementary specifies the amino acid that is carried by that tRNA

A

anticodon

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48
Q

Aminoacyl-tRNA site; the site on a ribosome where a new amino acid is added to a growing peptide

A

A site

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49
Q

A structure near the middle of eukaryotic chromosomes to which the fibers of the mitotic spindle attach during cell division

A

Centromere

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50
Q

A family of proteins that assists in the folding of other proteins

A

Chaperones

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51
Q

Structural variations in the genome that lead to different copies of certain sections of the DNA, due to duplication of those sections or deletions of those sections

A

copy-number variation

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52
Q

this is the enzyme that replicates DNA. Eukaryotes and prokaryotes have different versions of this enzyme

A

DNA polymerase

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53
Q

Stop codons and the poly-A-tail are found “__”

A

downstream toward the 3’ end

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54
Q

Proteins that assist with peptide bond formation during eukaryotic translation

A

Elongation factors

55
Q

Changes in gene expression that are not due to mutations, but are long-term and heritable (DNA methylation, chromatin remodeling, and RNA interference)

A

Epigenetics

56
Q

A nucleotide sequence in RNA that contains protein-coding information

A

Exon

57
Q

A mutation casued by an insertion or deletion of base pairs in a gene sequence in DNA suh that the reading frame of the gene (and thus the amino acid seuqence of the protein) is altered

A

frameshift mutation

58
Q

An enzyme that unwinds the double helix of DNA and separates the DNA strands in preparation for DNA replication

A

Helicase

59
Q

A gene appearing in a single copy in diploid organisms (ex: X-linked genes in human males)

A

Hemizygous gene

60
Q

Hetereogenous nuclear RNA; the primary transcript made in eukaryotes before splicing

A

hnRNA

61
Q

Physical change to a gene on DNA, such as methylation or histone binding, that renders it inactive, so that only one allele of the gene is expressed

A

Imprinting

62
Q

A system where the expression of those genes is stimulated by an abundance of substrate

A

Inducible system

63
Q

Eukaryotic proteins that assemble in a complex to begin translation

A

Initiation factors

64
Q

A nucleotide sequence that intervenes between protein-coding sequences. In DNA, these intervening sequences typically contain regulatory sequences, however in RNA they are simple spliced out to form the mature (translated) transcript

A

Introns

65
Q

Multiprotein complexes that attach the spindle fibers to the centromere of a chromosome

A

Kinetochore

66
Q

A set of genes for the enzymes necessary to import and digest lactose, under the control of a single promoter, whose expression is stimulated by lactose it is INDUCIBLE SYSTEM

A

lac operon

67
Q

An enzyme that connects two fragments of DNA to make a single fragment. This enzyme is used during DNA replication and is also used in recombinant DNA research

A

ligase

68
Q

A point mutation in which a codon that specifies an amino acid is mutated into a codon that specifies a different amino acid

A

Missense mutation

69
Q

mRNA that codes for a single type of protein, such is found in eukaryotic cells

A

monocistronic mRNA

70
Q

The monitoring of mRNA transcripts to eliminate those that are defective

A

mRNA surveillance

71
Q

A structure composed of a ribose molecule linked to one of the aromatic bases.

A

nucleoside

72
Q

A structure composed of two coils of DNA wrapped around an octet of histone proteins. It is the primary form of packaging of eukaryotic DNA

A

Nucleosome

73
Q

Small fragments of DNA produced in the lagging strand during DNA replication, joined later by DNA ligase to form a complete strand

A

Okazaki fragments

74
Q

A specific DNA nucleotide sequence where transcriptional regulatory proteins can bind

A

Operator

75
Q

A nucleotide sequence on DNA that contains three elements:

  • coding sequence for one or more enzymes
  • coding sequence for regulatory protein
  • upstream regulatroy sequences where the regulator protein can bind
A

Operon

76
Q

The speicifc location on a DNA strand where replication begins. Prokaryotes typically have a single origin of replication, while eukaryotes have several per chromosome

A

Origin of replication

77
Q

The enzymatic activity of the ribosome that catalyzes the formation of a peptide bond between amino acids. It is thought that the rRNA of the ribosome possesses the peptidyl transferase activity

A

Peptidyl transferase

78
Q

A type of mutation in DNA where a single base is substituted for another

A

Point mutation

79
Q

A string of several hundred adenine nucleotides added to the 3’ end of Eukaryotic mRNA

A

Poly-A-tail

80
Q

An RNA polymerase that creates a primer (made of RNA) to initiate DNA replication. DNA poly binds to the primer and elongates it

A

Primase

81
Q

The sequence of nucleotides on a chromosome that activates RNA polymerase so that transcription can take place.

A

Promoter

82
Q

Peptidyl-tRNA site, the site on a ribosome where the growing peptide (Attached to a tRNA) is found during translation

A

P site

83
Q

A cytoplasmic protein that binds to a stop codon when it appears in the A_site of the ribosome. Release factors modify the peptidyl transferase activity of the ribosome, such that a water molecule is added to the end of the completed protein. This releases the finished protein from the final tRNA, and allows the ribosome subunits and mRNA to dossociate

A

Release factor

84
Q

The site where the parental DNA double helix unwinds during replication

A

Replication fork

85
Q

Multiple sites of replication found on large, linear eukaryotic chromosomes

A

Replication bubbles

86
Q

A system (set of genes) where the expression of those genes is inhibited by the gene product (trp operon)

A

Repressible system

87
Q

A regulatory protein that binds DNa at a specific nucleotide sequence to prevent transcription of downstream genes

A

Repressor

88
Q

A structure made of two protein subunits and rRNA; this is the site of protein synthesis (translation) in a cell.

A

Ribosome

89
Q

Small noncoding RNA’s that bind to mRNAs these double stranded RNAs are then degraded and gene expression is reduced

A

RNA interference (RNAi)

90
Q

An enzyme that transcribes RNA. Prokaryotes have a single one while eukaryotes have 3

A

RNA polymerase

91
Q

What are the functions of RNA polymerase 1 in EUaryotes

A

Transcribes rRNA

92
Q

What is the function of RNA polymerase 2 in Eukaryotes

A

transcribes mRNA

93
Q

The prokaryotic ribosome-binding site on mRNA, found 10 nucleotides 5’ to the start codon

A

Shine Dalgarno sequence

94
Q

A group of three nucleotides that does not specify a particular amino acid, but instead serves to notify the ribosome that the protein being translated is complete. The codons are UAA, UGA, and UAG, also known as NONSENSE CODONS

A

stop codon

95
Q

Regions of the genome where short sequences of nucleotides are repeated one after another, anywhere from three to 100 times

A

Tandem repeats

96
Q

An enzyme that cuts one or both strands of DNA to relieve the excess tension caused by the unwinding of the helix by helicase during replication

A

Topoisomerase

97
Q

A point mutation in which a pyrimidine is substituted for a purine or vice versa

A

Transversion mutation

98
Q

The type of RNA that carries amino acids from the cytoplasm to the ribosome for incorporation into a growing protein

A

tRNA

99
Q

The attachment of an amino acid to a tRNA requires TWO HIGH ENERGY PHOSPHATE BONDS

A

tRNA loading

100
Q

A set of genes for the enzymes necessary to synthesize tryptophan under the control of a single promoter, the expression of which is inhibited by the presence of tryptophan

A

trp operon

101
Q

Enzymes that degrade various macromolecules and that require an acidic pH to function properly, these enzymes are found inside of lysosomes of cells

A

Acid hydrolases

102
Q

A contractile protein. In skeletal and cardia muscle it polymerizes to form the thin filaments. IT is involved in many contractile activites, such as cytokinesis, pseudopod formation, and muscle contraction.

A

Actin

103
Q

A carrier protein that transports two molecules across the plasma membrane in opposite directions.

A

Antiport

104
Q

An integral membrane protein that undergoes a conformational change to move a molecule from one side of the membrane to another.

A

Carrier protein

105
Q

A family of proteases that carry out the events of apoptosis

A

Caspases

106
Q

The primary enzyme in peroxisomes

A

Catalase

107
Q

This enzyme catalyzes the hydrolysis of hydrogen peroxide into water and oxygen

A

Catalase

108
Q

An integral membran protein that binds extracellular signaling molecules, such as hormones and peptides

A

Cell surface receptor

109
Q

A structure composed of a ring of nine microtubule triplets, found in pairs at the microtubule organizing center

A

Centriole

110
Q

The__duplicates during cell division and serves as the organizing center for the mitotic spindle

A

Centriole

111
Q

A fibrous protein found on the intracellular side of the plasma membrane that helps to invaginate the membrane.

A

Clathrin

112
Q

Properties that depend on the number of solute particles in a solution rather than on the type of particles

A

Colligative properties

113
Q

What are some colligative properties?

A
  • boiling point elevation
  • freezing point depression
  • vapor pressure depression
114
Q

A general cell junction used primarily for adhesion

A

Desmosome

115
Q

A contractile protein connecting microtubules in the “9+2” arrangement of cilia and eukaryotic flagella

A

Dynein

116
Q

A junction formed between cells, consisting of a protein channel called a connexon on each of the two cells, that connect to form a single channel between the cytoplasms of both cells.

A

Gap junctions

117
Q

__allow small molecules to flow between the cell and are important in cell-to-cell communication

A

Gap junctions

118
Q

A membrane lipid consisting of a glycerol molecule esterified to two fatty acid chains and a sugar molecule

A

Glycolipid

119
Q

A stack of membranes found near the rough ER in eukaryotic cells that is involved in the secretory pathway.

A

Golgi apparatus

120
Q

The__is involved in protein glycosylation (and other protein modifications) as well as sorting and packaging proteins

A

Golgi apparatus

121
Q

A protein embedded in the lipid bilayer a cell. These are typically cell surface receptors, channels, or pumps

A

Integral membrane protein

122
Q

Cytoskeletal filaments with a diameter in between that of the microtubule and the microfilament. __are composed of many different proteins and tend to play structural roles in cells

A

Intermediate filaments

123
Q

A protein channel in a cell plasma membrane that is specific for a particular ion, such as Na+ or K+.

A

Ion channel

124
Q

The double lipid bilayer that surrounds the DNA in eukaryotic cells

A

Nuclear envelope

125
Q

A protein channel in the nuclear envelope that allows the free passage of molecules smaller than 60 kD

A

Nuclear pore

126
Q

Small organelles that contain hydrogen peroxide produced as a byproduct of lipid metabolism. __convert hydrogen peroxide to water and oxygen by way of the enzyme catalase

A

Peroxisomes

127
Q

__consists of a glycerol molecule esterified to two fatty acid chains and a phosphate group

A

Phospholipids

128
Q

A pathway through a plasma membrane that restricts passage based only on the size of the molecule

A

Pore

129
Q

A highly specific cellular uptake mechanism. The molecule to be taken up must bind to a cell surface receptor found in a clathrin-coated pit

A

Receptor-mediated endocytosis

130
Q

The resting membrane potential is approximately __

A

-70 mV with respect to the otuside of the cell

131
Q

A large system of folded membranes within a eukaryotic cell that has ribosomes bound to it, giving it a rough appearance. These ribosomes synthesize proteins that will ultimately be secreted from the cell, incorporated into the plasma membrane, or transportd to the golgi apparatus or lysosome

A

Rough endoplasmic reticulum

132
Q

Active transport that relies on an established concentration gradient, typically set up by a primary active transporter. relies on ATP indirectly

A

Secondary active transport

133
Q

A network of membranes inside the eukaryotic cells involved in lipid synthesis (steroids in gonads), detoxification (in liver cells), and/or Ca2+ storage (muscle cells)

A

Smooth endoplasmic reticulum

MCAT (45 decks)

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