Untitled Flashcard Set

Overview of Cellular Biology

Both prokaryotes and eukaryotes share fundamental cellular components: plasma membrane, cytosol, ribosomes, and chromosomes, which are essential for cellular function.
Prokaryotes lack membrane-bound organelles and have a nucleoid region where their DNA is located, while eukaryotes possess organelles such as the nucleus, endoplasmic reticulum, and mitochondria.
Eukaryotic cells have a defined nucleus that houses DNA, organized into chromosomes, while prokaryotic DNA is circular and not enclosed.
The endomembrane system in eukaryotes includes structures like the rough and smooth ER, Golgi apparatus, and lysosomes, which are absent in prokaryotes.
Understanding the differences in cellular structure is crucial for grasping processes like protein synthesis and cellular metabolism.
Watching educational resources, such as the 'Inner Life of a Cell' movie, can enhance comprehension of cellular processes.

Plasma Membrane: Acts as a barrier and regulates the movement of substances in and out of the cell.
Cytosol: The fluid component of the cytoplasm where metabolic reactions occur.
Ribosomes: Sites of protein synthesis, translating mRNA into polypeptides.
Chromosomes: Structures that carry genetic information; understanding their organization is key to studying gene expression.

DNA is composed of nucleotides, which include purines (adenine, guanine) and pyrimidines (cytosine, thymine).
The antiparallel nature of DNA strands means one strand runs 5' to 3' while the other runs 3' to 5', allowing for complementary base pairing (A-T, C-G) with hydrogen bonds (2 for A-T, 3 for C-G).
The template strand is the one used for transcription; it is identified by its orientation and the presence of a promoter region.
The end result of gene expression is the synthesis of proteins, which are crucial for cellular function and structure.

Transcription involves three phases: initiation (RNA polymerase binds to the promoter), elongation (RNA strand is synthesized), and termination (RNA polymerase reaches a terminator sequence).
Eukaryotic transcription includes post-transcriptional modifications like 5' capping and polyadenylation, which protect mRNA and facilitate translation.
The spliceosome, composed of snRNA and proteins, removes introns and connects exons, allowing for the production of mature mRNA.
Translation occurs in ribosomes, which have three sites: A (aminoacyl), P (peptidyl), and E (exit), facilitating the assembly of amino acids into polypeptides.

Gene expression is regulated at multiple levels: transcriptional (initiation of transcription), post-transcriptional (mRNA processing), translational (initiation of translation), and post-translational (modifications after translation).
The lac operon is a classic example of gene regulation in prokaryotes, demonstrating how the presence of lactose induces gene expression.
Tumor suppressor genes prevent uncontrolled cell growth, while oncogenes promote it; mutations in these genes can lead to cancer.
Cancer cells often outcompete normal cells due to rapid division and evasion of apoptosis, resulting from genetic mutations.

Mutations can lead to various outcomes, including silent, missense, and nonsense mutations, which can affect protein function.
Understanding the implications of mutations is crucial for fields like genetics and cancer research, as they can lead to diseases.
The proteasome plays a role in degrading unneeded proteins, thus regulating protein levels and function within the cell.

DNA replication is semiconservative, meaning each new DNA molecule consists of one old and one new strand, ensuring genetic fidelity.
Key enzymes include DNA polymerase (synthesizes new DNA), helicase (unwinds DNA), and primase (creates RNA primers).
Differences in replication between prokaryotes (binary fission) and eukaryotes (mitosis) highlight the complexity of eukaryotic cell division.

The cell cycle consists of phases: G1, S (synthesis), G2, and M (mitosis), with checkpoints to ensure proper division.
Cyclins and cyclin-dependent kinases (CDKs) regulate the cell cycle, ensuring cells only proceed to the next phase when conditions are favorable.
PMAT (Prophase, Metaphase, Anaphase, Telophase) describes the stages of mitosis, while interphase (G1, S, G2) is often overlooked in this acronym.