Cell Cycle - Protein Synthesis Flashcards
What is a cell?
The smallest functional unit of a living organism
Why are cells so small?
To maximize surface-to-volume ratio
What is the structure of a plasma membrane and what is its function?
Two layers of phospholipids create a selective-permeable barrier that creates the shape of a cell and allows for cell reception.
Contains junctions for molecular transport, intercellular joints, and adhesion
Alright, let’s do this one last time, what are the organelles of a cell?
Cytoplasm - Cytosol + Organelles in it
Cytoskeleton - Microfilaments, Intermediate Fillaments, Microtubules
*Centrosome - Cell center, centrioles
Membranous Organelles
Mitochondria - tHe pOwErHoUsE oF tHe
Ribosomes - Protein synthesis
Endoplasmy Reticktiboom - Makes proteins if rough
Golgi Complex - Packs molecules for storage on cisternae or transport in secretory vesicles
Nucleus - Holds all the DNA
*Only in cells that divide
What is chromatin? What’s it made out of?
What is the difference between euchromatin and heterochromatin?
Loose, unwound DNA (when it is compacted we call it a chromosome)
It is made out of histones, which form spooks for strands of DNA (when combined it is called a nucleosome)
Euchromatin - Active during transcription
Heterochromatin - Inactive part of cell
What is the difference between a gene, a genome, and a proteome?
Gene - A segment of DNA coding for an RNA segment
Genome - All the genes in an individual or species
Proteome - All the proteins produced by a gene (greater than the number of genes)
What is a codon?
A sequence of three nucleotides on mRNA coding for a specific amino acid
There are 64 codons in all for the 20 amino acids
AUG - start codon, methionine
UUA, UAG, UGA - stop codons
True or False: Codons are universal to all organisms
True. The mRNA for insulin can be inserted into e. coli to make it produce insulin
What are the stages of transcription?
RNA polymerase initiates transcription buy binding to transcription factor and unwinding DNA
Initiation - Transcription factors bind to promoter region and turn gene on
Elongation - Nucleotides are added from 5’ to 3’ by RNA Polymerase, forming a temporary Hydrogen bond with the DNA template
Termination - The termination sequence of codons causes transcription to end and this pre-RNA dissociates from DNA and becomes mRNA, tRNA, or rRNA
Init 4 Long Term
What are the post-transcriptional modifications for RNA and what are their functions?
mRNA - Messenger, carries codes message from DNA to a ribosome
rRNA - Ribsosom, reads the mRNA
tRNA - Transfers correct amino acids for poly peptide synthesis
What is the difference between an exon and an intron?
An exon is the region being coded, the intron is the inactive region
Where does Translation happen and what are the key components?
In cytoplams of cell: mRNA binds to rRNA at A (amino-acyl) building site and is read by rRNA, then goes P (peptidyl) building site and lastly the E (exit) site
The APE in the cytoplasm reads, then builds a ladder to exit
What are the post-translational modifications that can happen to proteins?
The start methionine is removed by anino peptidaze
The protein undergoes folding, joining,or cleaving into smaller fragments
Carbohydrates or lipids are added (chenjcal modification)
What happens to proteins after they are synthesized?
They are modified as they pass through the lumen of the EndoRetic
They move to the golgi apparatus and are placed in cisternae
Secretory vesicles bud off cisternae and move out of the cell
What is the structure of a DNA molecule?
A nucleotide base pair attatched to a sugar (ribsose) attached to a phosphate group on the 5’ end and a hydroxyl group on its 3’ end that runs antiparallel to a mirror in a helix
When does DNA replicate, what kind of process is this?
Before a cell divides an exact copy of the DNA strand is made. This process is semiconservative, meaning two parent strands serve as template for two new half-strands
What are the steps in DNA replication and what enzymes are responsible for each step?
Begins at Origin if Replication
Strands separate forming “replication bubbles” with “replication forks” at each end
Helicase - unwinds and unzips at the forks
Topiosomerase - relieves the torque from the unwinding DNA
Primase - make an RNA primer for complimentary nucleotide bades
Polymerase III - Elongates the new strands by adding nucleotides to the 3’ end
Polymerase I - Proofreads nucleotides as it replaces RNA primers with them
Leading Strand - elongates toward fork
Lagging Strand - elongates away in discontinuous Okazaki fragments
Ligase - Joins the Okazaki fragments into a single strand
What is the direction of synthesis in replication?
5’ to 3’
What is mitosis? When does it happen?
Cell division
Cells divide to grow, to reproduce, to repair damaged cells, to replace dead cells
What is the difference between homologous chromosomes, autosomes, and sex chromosomes?
Sex chromosomes are the XY
Autosomes are the other 22 pairs
Homologous means the pairs are matching
What is a karyotype?
An orderly arrangement of chromosomes based on their shapes (useful for determining abnormalities)
What is the difference between a diploid and a haploid?
Haploid - n, Diploid - 2n, where n is the number of chromosomes. Diploids always come in homologous pairs
What are sister chromatids?
A duplicated chromosome creates two exact replicas, called sister chromatids, that connect at a centromere
What are the phases of a cell cycle and what happens during each phase?
Interphase - The cell is carrying out its functions (most of the lifetime)
Subdivide this into G1, S, G2*
Mitosis -Division
Prophase - Chromatin condenses into chromosomes, centrioles migrate to opposite poles of cell, the nuclear membrane breaks down, and mitotic spindles form
Metaphase - Sister chromatids align in the center of the cell (the mitotic spindle)
Anaphase - Mitotic spindles shorten, pulling chromosomes to opposite poles and creating daughters
Telophase - Chromosomes uncoil to chromatin, the spindle breaks down, the membrane reforms
*G is for Growth, cells that don’t divide have G0
What are cyclins?
The proteins that promote the different phases of a cell
What is cytokinesis?
The cleavage furrow dividing cytoplasm
What is a tumor cell?
Cell regulation fails and the cells divide uncontrollably, resulting in abnormal masses called tumors
What is the difference between a benign and a malignant tumor?
Benign - Does not invade adjacent tissues (but can still cause pressure, obstruction)
Malignant - Invades adjacent tissues
What is it called when a cell breaks away from the primary tumor and travels to other areas of the body?
Metastisizing
What is the difference between a normal cell and a cancer cell?
Normal: Stops dividing after a certain #
Responds to contact inhibition
Cells are differentiated (specific shape/function)
Undergo apoptosis if cell is damaged
Cancer: Divides indefinitely
Pile up on one another
Non-differentiates
Large, abnormal nuclei and/or chromosome numbers
What does TSG P53 do?
Tumor-suppressor genes, halt division if cell is damaged. If cell is reparable it is repaired, if too far gone it starts apoptosis
P53 mutations are common to 50% of all cancers
What is apoptosis?
Cell death/suicide
What is a telomere and what is its function?
Non-coding regions of DNA that are lost every time a cell divides, they are protective
Germinal and cancer cells divide indefinitely and do not age because they have the enzyme telomerase, which replaces the nucleotides not duplicated by DNA Polymerase
What is a mutation?
A change in the sequence of bases in a gene, caused by a mistake during replication
What is a mutagen?
Any factor in the environment that increases the chances of a mutation
What is the difference between a germinal and a somatic mutation?
Germinal - Occurs in gametes (ova and sperm), the mutations are passed on
Somatic - The mutation stays in the host
What are the different kinds of mutations?
Point - Substitution, change in a single nucleotide
Silent - A nucleotide changes but the protein does not
Frameshift (insertion or deletion) - a nucleotide is removed or added, shifting all the codons
What happens during most mutations (not silent)
The wrong protein is made, causing death or a new gene
