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BIO205 Test 2
Microbiology
60
Biology
Undergraduate 4
05/17/2013

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Term
Carbohydrate layer
Definition
A layer of sugar residues, including the polysaccharide portions of proteoglycans and oligosaccharides attached to protein or lipid molecules, on the outer surface of a cell
Term
Phospholipid
Definition
Type of lipid molecule used to make biological membranes. Generally composed of two fat acids linked through glycerol phosphate to one of a variety of polar groups
Term
Plasma Membrane
Definition
The membrane that surrounds a living cell, involved in cell communication, import and export of molecules and cell growth and motility.
Term
Membrane lipids
Definition
Two very different properties in a single molecule, water loving head, water hating tail
Term
Steroids
Definition
Lipids characterized by a carbon skeleton consisting of four fused rings (EX: Cholesterol)
Term
Lipid Bilayer
Definition
The biomolecular sheet of mainly phospholipid molecules that forms the structural basis for all cell membranes.
Term
Properties of membranes: Fluidity
Definition
Related to the fat acids saturation and sterols presence
Term
Properties of membranes: Polarity
Definition
Different composition in each layer of the membrane
Term
Cholesterol
Definition
Lipid molecule with a characteristic four-ringed steroid structure that is an important component of the plasma membranes of animal cells
Term
Membrane Protein
Definition
A protein associated with a lipid bilayer; can be either integral (transmembrane) or peripheral
Term
Membrane Domain
Definition
Functionally specialized region in a cell membrane characterized by the presence of particular proteins
Term
Membrane Transport Proteins
Definition
Any protein embedded in a membrane that serves as a carrier of ions or small molecules form one side to the other
Term
Transporter
Definition
Membrane protein that transports ions or molecules across a cell membrane
Term
Osmotic Pressure
Definition
Pressure that must be exerted on the low-solute concentration side of a semi-permeable membrane to prevent the flow of water across the membrane as a result of osmosis
Term
Na+ - K+ Pump
Definition
Transmembrane carrier protein, found in the plasma membrane of most animal cells, that pumps Na+ out of and K+ into the cell, using the energy derived from ATP hydrolysis
Term
Voltage-gated channel
Definition
Membrane protein that selectively allows ions such as Na+ (carried by the voltage-gated Na+ channel) to cross a membrane and is opened by changes in membrane potential. Found mainly in electrically excitable cells such as nerve and muscle.
Term
Ligand-gated channel
Definition
An ion channel that opens when it binds a small molecule such as a neurotransmitter
Term
Stress-gated channel
Definition
Membrane protein that allows the selective entry of specific ions into a cell and is opened by mechanical force
Term
Membrane Potential
Definition
A voltage difference across a membrane due to a slight excess of positive ions on one side and excess negative ions on the other
Term
Nernst Equation
Definition
Quantitative expression that relates the equilibrium ratio of concentrations of an ion on either side of a permeable membrane to the voltage difference across the membrane
Term
Action Potential
Definition
Rapid, transient, self-propagating electrical signal in the plasma membrane of a cell such as a neuron or muscle. A nerve impulse.
Term
Nerve Terminal
Definition
The ending of an axon from which signals are sent to adjoining cells, usually at a synapse
Term
Synaptic Vesicles
Definition
Small membrane-enclosed sac filled with neurotransmitter that releases its contents by exocytosis at a synapse
Term
Nucleoside
Definition
A molecule made of a nitrogen-containing ring compound linked to a five carbon sugar, which can be either ribose or deoxyribose
Term
Nucleotide
Definition
Nucleoside with a series of one or more phosphate groups joined by an ester linkage to the sugar moiety
Term
Base Pair
Definition
Two nucleotides in RNA or a DNA molecule that are specifically paired by hydrogen bonds (G with C and A with T or U)
Term
Chromosomes
Definition
Long threadlike structure composed of DNA and associated proteins that carries the genetic information of an organism.
Term
Gene
Definition
Region of DNA that controls a discrete hereditary characteristic of an organism, usually responsible for specifying a single protein or RNA molecule
Term
Telomere
Definition
Structure at the ends of linear chromosomes, associated with a characteristic DNA sequence that is replicated in a special way. Counteracts the tendency of the chromosome otherwise to shorten with each round of replication (Greek: Telo = end)
Term
Centromere
Definition
Constricted region of a mitotic chromosome that holds sister chromatids together; also the site on the DNA where the kinetochore forms and then captures microtubules from the mitotic spindle
Term
Chromatin
Definition
Complex of DNA, histones, and non-histone proteins found in the nucleus of a eukaryotic cell. The material of which chromosomes are made
Term
Euchromatin
Definition
One of the two main states in which chromatin exists within an interphase cell, the other being heterochromatin
Term
Heterochromatin
Definition
Region of a chromosome that remains unusually condensed and transcriptionally inactive during interphase
Term
ATP-dependent Chromatin-remodeling complex
Definition
Enzyme (typically multi-subunit) that uses the energy of ATP hydrolysis to alter histone-DNA interactions in eukaryotic chromosomes
Term
Nucleolus
Definition
Large structure in the nucleus where ribosomal RNA is transcribed and ribosomal subunits are assembled
Term
Replication Origin
Definition
Site on a chromosome at which DNA replication begins
Term
Replication Fork
Definition
Y-shaped region of a replicating DNA molecule at which the two daughter strands are formed and separate.
Term
Okazaki Fragments
Definition
Short length of DNA produced on the lagging strand during DNA replication. Adjacent fragments are rapidly joined together by DNA ligase to form a continuous DNA strand.
Term
Telomerase
Definition
Enzyme that elongates telomeres, the repetitive nucleotide sequences found at the ends of eukaryotic chromosomes
Term
Homologous Recombination
Definition
Genetic exchange between a pair of identical or very similar DNA sequences, typically located on a pair of homologous chromosomes. A similar process is used to repair double-stranded breaks in DNA.
Term
Nonhomologous end-joining
Definition
Mechanism for repairing double-stranded breaks in DNA in which the two broken ends are brought together and rejoined without requiring sequence homology
Term
Transposons
Definition
General name for short segments of DNA that can move from one location to another in the genome. Also known as mobile genetic element.
Term
Mobile genetic element
Definition
Short segment of DNA that can move, sometimes through an RNA intermediate, from one location in a genome to another. They are an important source of genetic information in most genomes
Term
Gene expression
Definition
The process by which a gene makes its effect on a cell or organism by directing the synthesis of a protein or an RNA molecule with a characteristic activity
Term
Messenger RNA (mRNA)
Definition
RNA molecule that specifies the amino acid sequence of a protein. Produced by RNA splicing (in eucaryotes) from a larger RNA molecule made by RNA polymerase as a complimentary copy of DNA.
Term
Reading Frames
Definition
The set of successive triplets in which a string of nucleotides is translated into protein.
Term
Transcription
Definition
A process that uses one strand of DNA as the template to synthesize a complementary RNA sequence, sometimes termed the primary transcript, catalyzed by the enzyme RNA polymerase
Term
General transcription factors
Definition
Proteins that assemble on the promoters of many eukaryotic genes near the start site of transcription and load the RNA polymerase in the correct position
Term
RNA splicing
Definition
Process in which intron sequences are excised from RNA molecules in the nucleus during the formation of messenger RNA
Term
Introns
Definition
Noncoding region of a eukaryotic gene that is transcribed into an RNA molecule but is then excised by RNA splicing to produce mRNA
Term
Exons
Definition
Segment of a eukaryotic gene that is transcribed into RNA and expressed; dictates the amino acid sequence of part of a protein
Term
RNA Processing
Definition
Broad term for the modifications that RNA undergoes as it reaches its mature form. For a Eukaryotic mRNA, processing typically includes capping, splicing, and polyadenylation
Term
Ribozymes
Definition
An RNA molecule possessing catalytic properties
Term
Spliceosome
Definition
Large assembly of RNA and protein molecules that splices Introns out of pre-mRNA in eukaryotic cells
Term
Translation initiation factors
Definition
Protein that promotes the proper association of ribosomes with mRNA and is required for the initiation of protein synthesis
Term
Initiator tRNA
Definition
Special tRNA that initiates ranslation. It always carries the amino acid methionine.
Term
Aminoacyl-tRNA synthetases
Definition
Enzyme that attaches the correct amino acid to a tRNA molecule to form an aminoacyl-tRNA
Term
Anticodon
Definition
Sequence of three nucleotides in a transfer RNA molecule that is complementary to the three-nucleotide codon on a messenger RNA molecule; each anticodon is matched to a specific amino acid covalently attached elsewhere on the transfer RNA molecule
Term
Protease
Definition
Enzyme such as trypsin that degrades proteins by hydrolyzing some of their peptide bonds
Term
Proteasome
Definition
Large protein complex in the cytosol that is responsible for degrading cytosolic proteins that have been marked for destruction by ubiquitylation or by some other means
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