Cell Biology: Organelles and Structures

Study Notes

Layers of flattened sacs receive and transmit messages from the ER to secrete and transport proteins

Involved with cellular movement including intracellular transport and cell division

Responsible for cellular respiration, where energy is produced by converting nutrients into ATP

Resides inside of the nucleus; is the site of ribosomal RNA (rRNA) transcription, processing, and assembly

Have a distinct physical structure, including centromeres (the center) and telomeres (the ends)
Centromeres play an important role during cell division, which will be discussed in the next section
Telomeres are located at the ends of chromosomes; they help protect the chromosomes from degradation after every round of cell division

Has a few key differences from mitosis, including the number of daughter cells produced (four cells, which require two rounds of cell division to produce) and the number of chromosomes each daughter cell has
During the first round of division (known as meiosis I), each chromosome replicates its DNA so that sister chromatids are formed
Homologous chromosomes align near the center of the cell and sister chromatids physically swap genetic material (this is called genetic recombination)
The daughter cells after the first round of meiosis are haploid
During the second round of cell division (known as meiosis II), sister chromatids are separated and two additional haploid daughter cells are formed

The ribosome moves along the mRNA adding amino acids to the growing polypeptide chain
When the ribosome reaches a “stop” codon (UAA, UAG, or UGA), the ribosome stops adding any new amino acids, detaches from the mRNA, and the protein is released
The final three-dimensional protein shape is integral to completing a specific structural or functional task

Individuals with blood type AB have both A and B antigens but do not produce antibodies for the ABO system
Individuals who are blood type O have nonspecific antigens and produce both anti-A and anti-B antibodies

The A and B alleles function as dominant alleles
The O allele codes for a nonfunctional antigen protein, which means there is no antigen present on the cell surface of O blood cells
Someone who is a heterozygous AO genotype is phenotypically blood type A, and a genotype of BO is blood type B
The ABO blood system also provides an example of codominance, which is when both alleles are observed in the phenotype