Cell Biology Flashcards

Flashcards for reviewing cell biology concepts.

Cell

Formed by carbon compounds (organic molecules), containing sugars, fatty acids, amino acids, and nucleotides.

Ribosomes

Made of ribonucleic acid and protein, found in eukaryotic and prokaryotic cells, moving along the mRNA sequence codon by codon.

Meiosis

A type of cell division that reduces the number of chromosomes in the parent cell by half and produces four gamete cells.

Interphase

Cell grows, copies chromosomes, and prepares for division.

Growth 1 (G1) phase

Cell synthesizes proteins, enzymes, and structural proteins.

Synthesis (S) phase

The hereditary material is replicated; each chromosome duplicates to become two sister chromatids joined at a centromere.

Growth 2 (G2) stage

Cell prepares for division.

Prophase I

Chromosomes coil up, nuclear membrane disintegrates, centrosomes move apart, and crossing over may occur.

Metaphase I

Bivalents (tetrads) align in the center of the cell and attach to spindle fibers.

Anaphase I

Homologous chromosomes separate.

Telophase I

Nuclear envelope reforms and nucleoli reappear.

Prophase II

Chromosomes coil up, nuclear membrane disintegrates, and centrosomes move apart.

Metaphase II

Spindle fibers form and sister chromatids align to the equator of the cell.

Anaphase II

Sister chromatids separate.

Telophase II & Cytokinesis II

Chromatids reach the poles and uncoil; nuclear membrane reforms, resulting in 4 haploid daughter cells.

Cytokinesis

The physical process of cell division, dividing the cytoplasm of a parental cell into two daughter cells.

Crossing Over

Exchange of genetic material between non-sister chromatids of homologous chromosomes during meiosis.

Golgi apparatus and ER

Key organelles for protein synthesis; the ER modifies and folds proteins, and the Golgi packages them for transport.

Post-translational Modifications

Modifications in the ER including folding, glycosylation, multimeric protein assembly, and proteolytic cleavage.

ER Structure

Located near the nucleus, made of flattened membrane sacs called cisternae with cis and trans faces.

Proteins Transferred from Cytosol to ER

Water-soluble and prospective transmembrane proteins.

Chaperone Proteins

Proteins that fail to fold correctly are retained in the ER by binding to these.

Lumen

The ER interior.

Smooth ER

Lacks ribosomes and is involved in the production of lipoprotein particles, synthesis of steroid hormones, and detox reactions.

Function of Mitochondria

Generation of metabolic energy in eukaryotic cells, converting carbohydrates and fatty acids to ATP via oxidative phosphorylation.

Cyclin-Dependent Kinases (CDKs)

Protein kinases needing a separate subunit (a cyclin) for enzymatic activity, regulating cell division and modulating transcription.

Apoptosis

Programmed cell death for getting rid of unneeded or abnormal cells.

Human Cancer

Causes universal overactivity of cell cycle CDKs, and their inhibition can lead to both cell cycle arrest and apoptosis.

Phosphorylation

The addition of a phosphoryl group to a molecule, regulating protein function and cell signaling by causing conformational changes.

Cytosol

Part of the cytoplasm not contained within intracellular membranes, site of many chemical reactions.

Cell Cycle

The series of events in a cell leading to its division and duplication of its DNA to produce two daughter cells.

Interphase

Cell grows and makes a copy of its DNA.

Mitotic (M) Phase

Cell separates its DNA into two sets and divides its cytoplasm, forming two new cells.

G1 Phase (Interphase)

Cell grows physically larger, copies organelles, and makes molecular building blocks.

S Phase (Interphase)

Cell synthesizes a complete copy of the DNA in its nucleus; also duplicates a microtubule-organizing structure called the centrosome.

G2 Phase (Interphase)

Cell grows more, makes proteins and organelles, and reorganizes its contents in preparation for mitosis.

Interphase

Interphase takes place between one mitotic (M) phase and the next.

M Phase

Cell divides its copied DNA and cytoplasm to make two new cells, involving mitosis and cytokinesis.

Early Prophase

Cell starts to break down some structures and build others up, setting the stage for division of chromosomes.

Late Prophase (Prometaphase)

Mitotic spindle begins to capture and organize the chromosomes.

Anaphase

Sister chromatids separate from each other and are pulled towards opposite ends of the cell.

Telophase

Cell is nearly done dividing, and it starts to re-establish its normal structures as cytokinesis takes place.

Cytokinesis end results

Two new cells, each with a complete set of chromosomes identical to those of the mother cell.

G0 Phase

Cells in this phase are not actively preparing to divide; the cell is in a quiescent (inactive) stage that occurs when cells exit the cell cycle.

Cell-Cycle Control System

Coordinate the steps of the cycle with molecular switches and cyclin-dependent protein kinases (Cdks).

Cell Cycle Checkpoints

Assess DNA integrity at G1, chromosome duplication at G2, and kinetochore attachment at M checkpoint.

Disruption of Cell Cycle Regulation

Can lead to diseases such as cancer, where cells divide without control and accumulate genetic errors.

Mitochondria

Found in plants and animal cells; surrounded by a double membrane; they have a rod-shaped structure, and produce ATP via oxidative phosphorylation.

Extrinsic Pathway of Apoptosis

Occurs outside a cell, triggered by a death ligand binding to a death receptor.

Intrinsic Pathway of Apoptosis

Begins when an injury occurs within the cell and the resulting stress activates the apoptotic pathway.

Mitochondria

Found in eukaryotes cells and are surrounded by a double membrane; site of oxidative phosphorylation, containing internal membranes for ATP production.

MicroRNAs (miRNAs)

Are small noncoding RNAs that play important roles in posttranscriptional gene regulation.

TATA Box

DNA sequence indicating where a genetic sequence can be read and decoded, specifying where transcription begins.

Post-Transcriptional Modifications

Changes that occur to a newly transcribed primary RNA transcript (hnRNA) after transcription has occurred and prior to its translation into a protein product, including phosphorylation and glycosylation.

Protein Glycosylation

Major post-translational modification with significant effects on protein folding, conformation, distribution, stability, and activity.

Cytoskeleton

Helps cells maintain their shape and internal organization and provides mechanical support, built by microtubules, intermediate filaments, and actin filaments.

Microtubules

Non-branching and rigid tubes of polymerized proteins found in cytoplasm, formed by tubulin, and presenting dynamic instability.

Intermediate Filaments

Have a size between microtubules and microfilaments, presenting rope fibers shape thanks to the non-covalent bonds.

Actin Filaments

Made of polymers of actin proteins, essential for cell movement, and shorter and more flexible than microtubules.

Vesicle

Small sac formed by a membrane and filled with liquid, moving substances into or out of the cell.

Microtubule Motor Proteins

Move across the microtubule, transporting cellular cargo within the cell.

Endocytosis

Cells take up fluid, and molecules, by the process of endocytosis, with ingestion being delivered to endosomes.

Pinocytosis

Ingestion of fluid and molecules via small pinocytic vesicles.

Phagocytosis

Ingestion of large particles via large vesicles called phagosomes.

DNA

Provides the genetic blueprint for all proteins in the body, packaged into chromosomes with histones.

Base-Pairing in DNA

Each strand of a DNA double helix contains a nucleotide sequence exactly complementary to the partner’s strand.

Replication Origins

Specific DNA sequences to which initiator proteins attach, breaking Hydrogen bonds to start replication.

Replication Forks

Y-shaped junctions formed at each replication origin, where a replication machine moves along DNA opening the double helix strands.

DNA Polymerase

Adds nucleotides to the 3’ end, growing the new DNA strand, using paternal as a template.

DNA Polymerase Qualities

Catalyzes the reaction of addition of a nucleotide only if the pairing between bases is correct and corrects errors through proofreading.

Primase

Uses RNA as a primer, which base-pairs to the template strand providing a base 3’ end as a starting point for DNA polymerase.

Nuclease

Enzyme that degrades the RNA primer.

Repair Polymerase

DNA polymerase that replaces RNA with DNA.

DNA Ligase

Enzyme that joins the ends of the different DNA fragments.

Transcription

Transfer of genetic instructions in DNA to mRNA in the nucleus.

RNA Polymerase

The enzyme adding ribonucleotides one by one to the growing RNA chain.

Ribosomes

Composed of one large and one small subunit, processing mRNA to produce amino acids using tRNA adaptors.

Translation

Transfer of genetic instructions from mRNA to a specific sequence of amino acid chains to create a protein

RNA Polymerase

Uses ribonucleotides triphosphates as substrates; can start an RNA chain without a primer; mistakes have relatively minor consequences.

Strategies to Repair Double-Strand DNA Breaks

Non homologous end joining and homologous recombination.

Nonhomologous End Joining

Removes nucleotides at the break site and rejoins the ends by DNA ligation.

Homologous Recombination

Flawless repair of the double-strand break, with no loss of genetic information.

Okazaki Fragments

Short sections of DNA formed at the time of discontinuous synthesis of the lagging strand during replication of DNA.

DNA Repair Mechanisms

Damaged DNA is recognized and removed, a repair DNA polymerase fills the gap, and DNA ligase seals the strand.

Mismatch

DNA copying error where a mispaired nucleotide is left behind.

Nucleotide Excision Repair

Repairs DNA damage with bulky lesions by excising and replacing 10 to 30 nucleotides.

Depurination

Loss of purine bases (A, G) in a nucleotide.

Deamination

Loss of amino group from a C to produce U.

UV Radiations

Promote the linkage between 2 adjacent pyrimidine bases.

Point Mutation

Individual nucleotides in the DNA sequence are changed.

Insertion Mutation

One or more nucleotide pairs are inserted into the DNA double helix.

Deletion Mutation

One or more nucleotide pairs are removed from the double helix.

Inversion Mutation

Original nucleotide(a) break and inverted sequence is re-inserted.

Nucleotide

The basic building block of DNA is made up of a sugar, phosphate and base.

Purines

Purine bases that include Adenine and Guanine.

Pyrimidines

Pyrimidine bases that include Cytosine and Thymine.

DNA

Composed of deoxyribonucleic acid and provides the genetic blueprint for all proteins in the body.

RNA

Contain the sugar ribose, uses U instead of T, and are single-stranded.

Messenger RNAs (mRNAs)

Direct the synthesis of proteins.

Ribosomal RNAs (rRNAs)

Form the core of the ribosome’s structure and catalyze protein synthesis.