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quorum sensing
A concentration of signaling molecules that allow bacteria to sense local population density in a process.
biofilm
Slime-enclosed communities of microorganisms.
local signaling
Includes paracrine signaling and synaptic signaling.
long-distance signaling
Refers to endocrine hormonal signaling. Target cell specifically binds hormones, and hormones that travel in the bloodstream.
three stages of cell signaling
Signal reception, signal transduction, cellular response.
three main types of membrane receptors
G protein-coupled receptors, receptor tyrosine kinases, and ion channel receptors.
GPCRs
Cell-surface transmembrane receptors that work with the help of a g protein. They bind the energy-rich GTP and are all very similar in structure. They are widespread and diverse in their functions.
receptor tyrosine kinases
Membrane receptors that catalyze the transfer of phosphate groups from ATP to another protein.
ligand-gated ion channel receptors
Acts as a gate that opens and closes when the receptor changes shape.
intracellular receptors
Found in the cytoplasm; are small or hydrophobic chemical messengers that can readily cross the membrane and activate receptors.
signal transduction pathways
The binding of a signaling molecule to a receptor triggers the first step in a chain of molecular interactions. An activated receptor activates another protein, which activates another.
phosphorylation
Process where protein kinases transfer phosphates from ATP to protein.
dephosphorylation
Process where protein phosphatases rapidly remove the phosphates from proteins.
functions of protein kinases
Transfer phosphates from ATP to protein.
functions of protein phosphates
Rapidly remove the phosphates from proteins.
nuclear and cytoplasmic responses
A signal transduction pathway leads to regulation of one or more cellular activities, with this response occurring either in the nucleus or cytoplasm.
Signaling pathways regulate
the synthesis of enzymes or other proteins, usually turning genes on or off in the nucleus
Final activated molecule in signal transduction pathway may
function as a transcription factor or may regulate the activity of protein rather than their synthesis
four aspects of signal regulation
Amplification of the signal, specificity of the response, overall efficiency of response enhanced by scaffolding proteins, termination of the signal.
scaffolding proteins
Large relay proteins to which several other relay proteins are attached. They can increase the signal transduction efficiency by grouping together different proteins involved in the same pathway.
apoptosis
Components of the cell are chopped up and packaged into vesicles that are digested by scavenger cells. Prevents enzymes from leaking out of a dying cell and damaging neighboring cells.
mitosis
The division of one nucleus into two genetically identical nuclei.
genome
A cell's endowment of DNA, its genetic information.
chromosomes
Each chromosome consists of one long linear DNA molecule associated with many proteins.
chromatin
The entire complex of DNA and proteins that is the building material of chromosomes.
somatic cells
All body cells except the reproductive cells, human 46 chromosomes.
gametes
Reproductive cells, human egg and sperm 23 chromosomes.
sister chromatids
Joined copies of the original chromosome.
cohesins
Protein complexes attached all along the lengths of sister chromatids.
centromere
A region of the chromosomal DNA where the chromatid is attached most closely to its sister chromatid.
cytokinesis
The division of the cytoplasm.
cell cycle
Can be divided into interphase and mitosis.
subphases in interphase
G1, S phase, and G2 phase.
stages in mitosis
Prophase, prometaphase, metaphase, anaphase, telophase.
DNA synthesis
Takes place in the S phase of the cell cycle.
kinetochore
A structure made up of proteins that have assembled on specific section of DNA at each centromere.
parts of spindle
Centrosomes, the spindle microtubule, the asters (radial array of short microtubules, extends from each centrosome).
cytokinesis in animal cells
Cleavage furrow are formed.
cytokinesis in plant cells
Cell plate are formed.
How do prokaryotes reproduce?
Prokaryotes reproduce by binary fission.
What happens to the chromosome during binary fission in prokaryotes?
The chromosome replicates, beginning at the origin of replication.
What do the daughter chromosomes do during prokaryotic binary fission?
The two daughter chromosomes actively move apart.
transformation
Cells that acquire the ability to divide indefinitely.
benign tumor
Abnormal cells that remain only at the original site.
malignant tumor
Invade surrounding tissues and can undergo metastasis, the spread of cancer cells to other parts of the body where they may form additional tumors.
metastasis
The spread of cancer cells to other parts of the body where they may form additional tumors.
histones
The proteins that are responsible for the first level of DNA packing in chromatin.
What are nucleosomes?
The basic units of DNA packing.
What do the 'beads' in nucleosomes refer to?
Histone protein complexes.
What does the 'string' in nucleosomes refer to?
The DNA strand itself.
karyotyping
A test that examines the number and structure of chromosomes in a sample of cells to identify genetic abnormalities.
models for DNA replication
Conservative model, Semiconservative model (proved correct), Dispersive model.
how many origins of replication in PR and EU
Hundreds or thousands in prokaryotes and in eukaryotes.
proteins involved in DNA replication
Helicase, Single-strand binding protein, Topoisomerase, Primase.
helicase
unwinds parental double helix at replication forks
single strand binding protein
Binds to and stabilizes single-stranded DNA until it can be used as a template.
Topoisomerase
relieves overwinding strain ahead of replication forks by breaking, swiveling, and rejoining DNA strands
What is the function of primase?
Synthesizes an RNA primer.
Where does primase synthesize an RNA primer on the leading strand?
At the 5' end.
Where does primase synthesize RNA primers on the lagging strand?
At the 5' end of each Okazaki fragment.
functions of DNA polymerase
Proofread newly made DNA, replacing any incorrect nucleotides.
leading strand
Is elongated continuously in the 5' to 3' direction as the fork progresses.
DNA lagging strand
Synthesized as a series of segments called Okazaki fragments, which are joined together by DNA ligase.
DNA pol III
Using parental DNA as a template, synthesizes new DNA strand by adding nucleotides to an RNA primer or a pre-existing DNA strand
DNA pol I
Removes RNA nucleotides of primer from 5' end and replaces them with DNA nucleotides
DNA ligase
Joins Okazaki fragments of lagging strand; on leading strand, joins 3' end of DNA that replaces primer to rest of leading strand DNA
Why DNA is shortened after each replication?
The ends of linear chromosomes, called telomeres, cannot be fully copied by the DNA polymerase enzyme during replication
telomeres
Special nucleotide sequences at the ends of Eukaryotic chromosomal DNA molecules. Do not prevent the shortening of DNA molecules but do postpone the erosion of genes near the ends of DNA molecules.
where are telomeres active and not active?
active in normal stem cells and cancer cells; normally absent from or at a very low level in somatic cells
oncogenes
Cancer causing genes in some types of viruses.
pro-oncogenes
The corresponding normal cellular genes that are responsible for normal cell growth and division.
ways to turn proto-oncogenes into oncogenes
Movement of DNA within the genome, Amplification of a proto-oncogene, Point mutations in the proto-oncogene or its control elements.
homologous chromosomes
Pair of chromosomes that are similar in length, centromere position, and gene arrangement.
sex chromosomes
Determine the sex of the individual, called X and Y.
autosomes
Remaining 22 pairs of chromosomes.
diploid cell
Two sets of chromosomes.
haploid cell
One set of chromosomes.
What does mitosis do to the number of chromosome sets?
Mitosis conserves the number of chromosome sets.
What type of cells does mitosis produce?
Cells that are genetically identical to the parent cell.
What does meiosis do to the number of chromosome sets?
Meiosis reduces the number of chromosome sets from two (diploid) to one (haploid).
What type of cells does meiosis produce?
Cells that differ genetically from each other and from the parent cell.
independent assortment of homologous chromosomes
Homologous pairs of chromosomes orient randomly at metaphase I of meiosis.
crossing over
By combining DNA inherited from two parents into a single chromosome, crossing over is an important source of genetic variation in sexual life cycles.
How is each pair of chromosomes sorted in independent assortment?
Each pair of chromosomes sorts maternal and paternal homologs into daughter cells independently of other pairs
