Unit 1 - Cell Biology Flashcards

Vocabulary flashcards covering core terms, definitions, key concepts, organelles, processes, and historical figures from Unit 1: Cell Biology.

Cell Theory

The fundamental biological theory stating that all living organisms are composed of cells, cells are the smallest units of life, and cells come only from pre-existing cells through cell division.

Aseptate Fungal Hyphae

Atypical cell structures in fungi that lack internal cross-walls (septa) and contain multiple nuclei within a continuous cytoplasm, challenging the standard cell structure concept.

Magnification

The factor by which a microscope image is enlarged relative to the actual size of the specimen, calculated using the formula $\text{Magnification} = \frac{\text{image size}}{\text{actual size}}$.

Resolution

The clarity of a viewed specimen or the minimum distance between two points at which they can still be distinguished as separate entities under a microscope.

Unicellular Organisms

Single-celled organisms that carry out all seven functions of life (metabolism, response, homeostasis, growth, reproduction, excretion, and nutrition) independently within a single cell.

Differentiation

The developmental process by which unspecialized cells become specialized in structure and function in multicellular organisms.

Gene Expression

The mechanism controlling cell differentiation, where specific genes are switched on (expressed) to determine cell function while other unneeded genes are switched off (unexpressed).

Stem Cells

Undifferentiated cells that have the ability to continuously divide for self-renewal and differentiate into specialized cell types.

Meristems

The actively growing tissue regions at the tips of plant roots and shoots that contain plant stem cells capable of continuous growth and differentiation.

Stargardt's Disease

An inherited genetic disorder caused by a mutation in the $ABCA4$ gene, leading to the degeneration of retinal photoreceptor cells and progressive vision loss; treated using embryonic stem cell therapy.

Parkinson's Disease

A progressive neurodegenerative disorder caused by the gradual death of dopamine-secreting neurons in the midbrain, leading to motor control impairment.

Prokaryotic Cells

Simple, unicellular cells that lack a membrane-bound nucleus and internal membrane-bound organelles.

Nucleoid

The region within the cytoplasm of a prokaryotic cell that contains the cell's naked, circular DNA.

Peptidoglycan

A polymer consisting of sugars and amino acids that forms the cell wall of most bacteria to maintain structural shape and prevent cell lysis.

Pili

Hair-like protein projections on the outer surface of prokaryotic cells that assist in surface attachment and DNA transfer during conjugation.

Plasmids

Small, independent rings of extra-chromosomal DNA found in some prokaryotes that often contain genes providing selective advantages, such as antibiotic resistance.

Binary Fission

A method of asexual reproduction in prokaryotes where a parent cell replicates its DNA and divides into two genetically identical daughter cells.

Eukaryotic Cells

Complex cells that contain a true nucleus enclosing linear DNA, as well as distinct membrane-bound organelles.

Compartmentalization

The organization of the eukaryotic cell interior into distinct, membrane-enclosed spaces, allowing specific cellular processes to occur efficiently under specialized local conditions.

Nucleolus

A dense, non-membrane-bound structure within the eukaryotic nucleus where ribosomes are assembled.

Svedberg Unit ($S$)

A unit of sedimentation rate used to describe ribosome size based on density, mass, and shape during centrifugation (e.g., $70S$ in prokaryotes, $80S$ in eukaryotes).

Rough Endoplasmic Reticulum (rER)

A eukaryotic membrane network covered with ribosomes that synthesizes and transports proteins intended for membranes or exocytosis.

Smooth Endoplasmic Reticulum (sER)

A eukaryotic membrane network lacking ribosomes that functions in lipid synthesis, phospholipid production, and chemical detoxification.

Golgi Apparatus

An organelle composed of flattened membrane sacs (cisternae) that modifies, packages, and sorts proteins received from the rough ER into vesicles for intracellular transport or secretion.

Mitochondria

Double-membrane-bound organelles containing their own circular DNA and $70S$ ribosomes that generate ATP energy through aerobic cellular respiration.

Adenosine Triphosphate (ATP)

A high-energy nucleotide molecule consisting of adenosine and three phosphate groups that acts as the primary chemical energy currency for cellular functions.

Lysosomes

Membrane-bound digestive organelles containing hydrolytic enzymes used to break down cellular waste, damaged organelles, and foreign substances.

Tonoplast

The membrane surrounding the large central vacuole in plant cells that regulates the transport of solutes and water into the cell sap.

Chloroplasts

Double-membrane-bound organelles in plant cells containing chlorophyll, thylakoid membrane stacks (grana), and stroma, serving as the sites of photosynthesis.

Centrioles

Microtubule-based cylindrical structures present in animal cells that assemble into centrosomes and organize spindle fibers during nuclear division.

Endosymbiotic Theory

The evolutionary theory proposed by Lynn Margulis stating that eukaryotic organelles such as mitochondria and chloroplasts originated as free-living prokaryotes that were engulfed by ancestral host cells.

Fluid Mosaic Model

The cell membrane structure model proposed by Singer and Nicolson in 1972 describing a fluid phospholipid bilayer with embedded, laterally moving proteins, lipids, and carbohydrates.

Amphipathic

Describing a molecule that contains both hydrophilic (water-attracting) and hydrophobic (water-repelling) regions, such as phospholipids.

Integral Proteins

Membrane proteins that are permanently embedded within the phospholipid bilayer, often spanning across both layers as transmembrane proteins.

Peripheral Proteins

Proteins temporarily attached to the inner or outer surface of the lipid bilayer, primarily participating in cell signaling and recognition.

Simple Diffusion

The passive net movement of small or non-polar molecules down their concentration gradient directly across the lipid bilayer without requiring energy or transport proteins.

Facilitated Diffusion

The passive transport of large, polar, or charged particles down a concentration gradient across a membrane through specialized channel or carrier proteins.

Osmosis

The passive movement of water molecules across a partially permeable membrane from a region of lower solute concentration (hypotonic) to a higher solute concentration (hypertonic).

Hypertonic Solution

A solution with a higher solute concentration relative to another solution or cell, causing water to leave the cell via osmosis.

Hypotonic Solution

A solution with a lower solute concentration relative to another solution or cell, causing water to enter the cell via osmosis.

Isotonic Solution

A solution having an equal solute concentration relative to the internal environment of a cell, resulting in no net movement of water.

Active Transport

The energy-requiring movement of substances across a cell membrane against their concentration gradient (from low to high concentration) using ATP and membrane pumps.

Sodium-Potassium Pump

A membrane-bound protein pump that hydrolyzes ATP to actively pump 3 $\text{Na}^+$ ions out of the cytoplasm and 2 $\text{K}^+$ ions into the cell.

Endocytosis

An active bulk transport mechanism where the cell membrane invaginates around external material to form an intracellular vesicle.

Phagocytosis

A form of endocytosis ('cell eating') where pseudopodia engulf large solid particles or microorganisms into an intracellular vesicle.

Pinocytosis

A form of endocytosis ('cell drinking') where the cell membrane folds inward to take in fluid droplets and small dissolved solutes.

Exocytosis

An active bulk transport mechanism in which intracellular membrane-bound vesicles fuse with the plasma membrane to secrete substances out of the cell.

Interphase

The active phase of the cell cycle between nuclear divisions, composed of $G_1$ (growth), $S$ (DNA replication), and $G_2$ (preparation for division).

Supercoiling

The process in which linear DNA wraps tightly around histone proteins to condense into distinct chromosomes prior to mitosis.

Mitosis

The division of a eukaryotic nucleus into two genetically identical daughter nuclei, consisting of Prophase, Metaphase, Anaphase, and Telophase.

Cytokinesis

The division of the cell cytoplasm that follows mitosis, occurring via a cleavage furrow in animal cells and a cell plate in plant cells.

Cyclins

A family of regulatory proteins whose concentrations fluctuate throughout the cell cycle, binding to Cyclin-Dependent Kinases (CDKs) to activate key cell cycle transitions.

Metastasis

The process by which malignant tumor cells break away from a primary tumor and travel through blood or lymphatic vessels to form secondary tumors elsewhere in the body.

Carcinogens

Chemicals, radiation, or infectious agents that directly cause cancer by inducing genetic mutations.

Oncogenes

Mutated versions of proto-oncogenes that stimulate excessive cell proliferation and cause tumor development.

Mitotic Index

The ratio of actively dividing cells undergoing mitosis to the total number of cells in a tissue sample, calculated as $\text{Mitotic Index} = \frac{\text{Cells in mitosis}}{\text{Total number of cells}}$.

Meiosis

A specialized reduction division of diploid germ cells involving two successive divisions (Meiosis I and II) to yield four genetically distinct haploid gametes.

Synapsis

The pairing process during Prophase I of meiosis where homologous maternal and paternal chromosomes line up side-by-side to form a bivalent.

Chiasmata

X-shaped points of contact where non-sister chromatids of homologous chromosomes cross over and exchange genetic material during Prophase I of meiosis.

Crossing Over

The exchange of genetic material between non-sister chromatids of a bivalent at chiasmata during Prophase I, producing recombinant chromosomes.

Non-disjunction

The failure of homologous chromosome pairs (in Anaphase I) or sister chromatids (in Anaphase II) to separate during meiosis, resulting in gametes with abnormal chromosome numbers ($n + 1$ or $n - 1$).

Karyogram

A visual photograph or diagram showing the complete chromosome set of an organism, organized into homologous pairs in order of decreasing length.

Trisomy 21

A genetic condition, commonly known as Down syndrome, caused by a non-disjunction event resulting in three copies of chromosome 21 ($47$ chromosomes total per cell).