Human Cell Biology, Molecular Genetics, Homeostasis, and Oncology

Vocabulary flashcards covering human cell structure, organelles, membrane transport, genetics, protein synthesis, homeostasis, feedback mechanisms, and cancer biology based on lecture material.

Chemotherapy Target Cells

Cells targeted by chemotherapy due to their rapid division, including cancer cells, bone marrow cells, hair follicle cells, and epithelial cells lining the stomach and intestine.

$G_0$ Phase ($G\text{-Zero}$)

A quiescent rest phase or extended $G_1$ phase of the cell cycle during which cells do not divide, lasting anywhere from hours to days or years.

Phase I Liver Detoxification

The initial bioactivation process in hepatocytes that packages toxins (such as drugs, pesticides, food additives, and hormones) to prepare them for waste pickup and elimination.

Prophase

The initial stage of mitosis during which chromatin condenses into chromosomes, the nuclear envelope breaks down, centrioles migrate to opposite poles, and spindle fibers grow.

Metaphase

The stage of mitosis where condensed chromosomes line up along the midline of the cell and spindle fibers attach to kinetochores.

Anaphase

The stage of mitosis in which centromeres divide in two and spindle fibers pull sister chromatids to opposite poles of the cell.

Telophase

The final stage of mitosis where chromosomes gather at opposite poles, chromatin decondenses, new nuclear envelopes and nucleoli appear, and the mitotic spindle vanishes.

Cyclins

Regulatory proteins that accumulate during the cell cycle to activate Cyclin-Dependent Kinases (CDKs), driving the cell forward toward the mitotic phase.

Gene

A specific sequence of DNA that contains the genetic instructions for a cell to synthesize a functional molecule or protein.

Alleles

Alternative forms of the same gene situated at corresponding positions on homologous chromosomes.

Transcription

The nuclear process where a segment of DNA is transcribed to synthesize a complementary strand of messenger RNA (mRNA).

Translation

The cytoplasmic process at the ribosome where mRNA codons are decoded by transfer RNA (tRNA) to assemble amino acids into a specific protein chain.

Complementary Base Pairing

The specific hydrogen bonding rule in DNA where Adenine ($\text{A}$) pairs with Thymine ($\text{T}$) and Guanine ($\text{G}$) pairs with Cytosine ($\text{C}$).

Transfer RNA (tRNA)

RNA molecules that deliver specific amino acids to the ribosome by matching their anticodon sequence to complementary codons on mRNA.

Essential Amino Acids

Amino acids that cannot be synthesized by the human body and must be acquired through nutritional intake.

Oncogenes

Activated or mutated forms of proto-oncogenes that accelerate cell growth and division, leading to uncontrolled proliferation.

Tumor Suppressor Genes

Genes (such as BRCA1 and BRCA2) that inhibit excessive cell division and slow cell growth, acting as a brake pedal against cancer development.

$G_1$ Phase

The longest phase of the cell cycle during which the cell is metabolically active, performs its normal functional roles for tissues or organs, and duplicates organelles.

S Phase

The synthesis phase of the cell cycle during which chromatin uncoils and an exact copy of each DNA strand is replicated.

Fluid Mosaic Model

The structural model describing the cell plasma membrane composed of a phospholipid bilayer ($75\%$ phospholipids), cholesterol ($20\%$), glycolipids ($5\%$), and floating proteins.

Glycocalyx

The carbohydrate-rich area on the outer cell membrane made of glycolipids and glycoproteins that aids in cell adhesion and self-recognition.

Simple Diffusion

Passive transport of small non-polar or lipid-soluble molecules moving directly through the phospholipid bilayer down a concentration gradient without energy.

Facilitated Diffusion

Passive movement of large or polar molecules across the plasma membrane from high to low concentration using integral channel or transport proteins.

Active Transport

Energy-requiring movement of substances across a membrane against their concentration gradient from low to high concentration using ATP.

Smooth Endoplasmic Reticulum

A membrane-bound organelle lacking ribosomes that synthesizes lipids and steroids, detoxifies drugs and alcohol, and stores ions.

Rough Endoplasmic Reticulum

A membrane-bound organelle studded with ribosomes involved in modifying proteins synthesized by those ribosomes.

Mitochondria

Double-membrane bound organelles containing inner cristae folds that act as the primary energy producers synthesizing ATP for cellular work.

Lysosomes

Membrane-bound organelles filled with hydrolytic digestive enzymes that break down waste, old cell components, or perform autolysis.

Homeostasis

The self-regulating physiological property of a biological system to maintain a stable internal environment around a normal set point for survival.

Negative Feedback Loop

A homeostatic mechanism that detects a deviation from a set point and initiates a response that reverses or opposes the original stimulus.

Positive Feedback Loop

A physiological mechanism that amplifies a stimulus in the same direction as the initiation event rather than maintaining a stable set point.

Cell Theory

The core tenets stating that all cells come from pre-existing cells, cells are the simplest structural/functional units of life, and body physiology relies on cell activities.