Cellular Transport and DNA Replication

These flashcards cover key concepts about cellular transport, DNA replication, and associated enzymes and processes.

ATP-dependent transporters

Transporters that catalyze the movement of substances using energy from ATP.

ApoE

An ABC transporter associated with Alzheimer's Disease.

MDR (multidrug resistance)

An ABC transporter associated with xenobiotics and drug resistance.

CFTR

An ABC transporter associated with Cl- ion channels and cystic fibrosis.

Fe2+

An ion that has a strong tendency to bind to O2 and is chelated by a tetra-pyrrole ring.

heme

Ferroprotoporphyrin is also known as heme.

myoglobin

Single polypeptide that serves for O2 storage.

hyperbolic

Type of binding curve exhibited by myoglobin.

hemoglobin

Tetrameric protein that is responsible for O2 transport.

sigmoidal

Type of binding curve exhibited by hemoglobin.

weak

In low pO2 conditions, binding strength of oxygen is characterized as weak.

allosteric

O2 binding occurs at the allosteric site.

cooperative

Conformational changes in hemoglobin due to the 'allosteric switch' refer to cooperative binding.

decreases

The accumulation of CO2 leads to a decrease in pH.

deoxy

Form of hemoglobin that is tense with low affinity for O2.

oxy

Form of hemoglobin that is relaxed with high affinity for O2.

BPG

Binding of bisphosphoglycerate decreases the affinity of hemoglobin for O2.

deoxy

Form of hemoglobin that is stabilized by BPG.

lower

The fetus has lower BPG affinity to have higher O2 affinity than the mother.

deoxy

Sickle cell hemoglobin refers to aggregation of the deoxy form.

DNA polymerase

Enzyme that binds nucleotides via phosphodiester bonds.

fork

DNA synthesis occurs at the replication fork.

topoisomerase

Enzyme that relaxes supercoiling and breaks DNA strands.

helicase

Enzyme that unwinds the DNA helix.

SSB proteins

Single-strand binding proteins that enhance template exposure, increasing fidelity.

primase

Enzyme that places RNA primers during DNA replication.

DNA

RNA primers must be replaced by DNA.

clamps

Proteins that assist DNA polymerase in extending from existing primers.

pol I

Form of DNA polymerase essential to the lagging strand, replacing RNA primers with DNA.

pol III

Form of DNA polymerase that cannot remove base pairs.

ligase

Enzyme that seals the Okazaki fragments together.

termination

Termination of DNA replication requires the TUS (termination utilization substance).

fidelity

Accuracy in DNA replication is increased by the primer through cooperative pairing.

telomeres

Extensions of chromosomes needed because DNA pol I cannot synthesize the 5' end of the lagging strand.

aphidicolin

An antiviral/antimitotic that blocks early S phase of the cell cycle.

topoisomerase inhibitors

Quinolone antibiotics, chemotherapy, and camptothecin are all considered topoisomerase inhibitors.

licensing

Positive control factors of DNA replication that accumulate during G1 and coat DNA with MCM proteins.

geminin

Negative controls of DNA replication that prevent MCM protein assembly on newly synthesized DNA.

depurination

Hydrolysis of DNA that occurs between a purine and deoxyribose sugar.

deamination

Hydrolysis of DNA that results from the loss of an amino group.

transition

Mispairing that results from replacement of a purine with a purine or a pyrimidine with a pyrimidine.

transversion

Mispairing that results from replacement of a purine with a pyrimidine or vice versa.

3' to 5'

Correcting mistakes in DNA replication via proofreading occurs through 3' to 5' exonuclease activity.

endonucleases

Enzymes that cleave double-stranded DNA at specific sequences to distinguish self from foreign DNA.

BER (base excision repair)

DNA repair that occurs when glycosylases recognize distortions and cleave the N-glycosidic bond.

replicase

Enzyme found in retroviruses that copies RNA.

reverse transcriptase

Enzyme found in retroviruses that makes a DNA copy of itself to insert into a host.

GP120

The activation process that results in unfolding of GP41.

GP41

Protein that refolds at the membrane to pull viruses into the cell.

integrase

Enzyme that cleaves the 3' end of viral DNA for entry into the host.

nucleoside

Analogue reverse transcriptase inhibitor that causes chain termination when incorporated into viral DNA.

non-nucleoside

Analogue reverse transcriptase inhibitor that distorts the binding potential of reverse transcriptase.

TATA box

Promoter region where initiation of transcription begins.

backtracking

Process of proofreading in which RNA polymerase moves in reverse after elongation.

operon

Contains regulatory genes, operator, and structural genes that include a repressor and inducer.

inducer

Presence of an inducer inactivates the repressor, allowing gene transcription to proceed.

methylation

Process that causes gene expression to continue.

acceptor stem

The part of tRNA found at its top that attaches to the amino acid during 'charging'.

codon

Triple base sequence that corresponds to an amino acid.

AUG

The start codon in protein synthesis.

shine-delgarno

Sequence on RNA that aligns the ribosome for efficient and accurate attachment.

ribosomes

Universally catalyze protein synthesis by aligning mRNA and tRNA.

A site

The site of the ribosome where incoming amino acids bind.

P site

The site on the ribosome that extends the peptide chain.

E site

The exit site of the ribosome that allows tRNA to leave.

peptidyltransferase

Enzyme that forms peptide bonds during translation elongation.