IB Biology: Cell Structure, Specialization, and Body System Integration

Comprehensive vocabulary flashcards covering cell structure, microscopy, stem cells, prokaryotes, eukaryotes, and autonomic/endocrine integration of body systems based on lecture notes.

Cell Theory

The foundational biological principle stating that all living things are composed of cells, cells are the basic units of structure and function, and all cells arise from preexisting cells.

Deductive Reasoning

A logical approach progressing from general premises to specific conclusions, such as using cell theory to deduce that a newly discovered organism consists of one or more cells.

Universal Cellular Structures

The four structural components shared by all cells: a phospholipid plasma membrane, cytoplasm composed mainly of water, $DNA$ as genetic material, and ribosomes for protein synthesis.

Peptidoglycan Cell Wall

The rigid external layer characteristic of prokaryotic cells that provides strength and structural support, preventing the cell from bursting under osmotic pressure.

Nucleoid Region

The non-membrane-bound region in the cytoplasm of a prokaryote containing a single circular chromosome of naked $DNA$ without associated histone proteins.

70S Ribosomes

Smaller ribosomes found in prokaryotic cells that are responsible for protein synthesis.

80S Ribosomes

Larger ribosomes located within eukaryotic cells that carry out protein synthesis.

Pili

Hair-like surface appendages on bacteria (present in Bacillus but absent in Staphylococcus) that allow attachment to surfaces and mediate the exchange of genetic material between cells.

Flagellum (Prokaryotic)

A cellular structure utilized for locomotion, present in certain prokaryotes such as Bacillus but absent in Staphylococcus.

Rough Endoplasmic Reticulum (Rough ER)

A membrane network studded with ribosomes that serves as a site of protein synthesis and transports synthesized proteins toward the Golgi apparatus.

Smooth Endoplasmic Reticulum (Smooth ER)

A membrane network lacking attached ribosomes that is dedicated to lipid synthesis and cellular detoxification.

Golgi Apparatus

A eukaryotic organelle responsible for modifying, sorting, and packaging proteins for export or secretion from the cell.

Lysosome

A specialized membrane-bound vesicle loaded with hydrolytic enzymes designed to digest large biological molecules and cellular waste.

Mitochondrion

A double-membrane eukaryotic organelle responsible for aerobic respiration and the production of $ATP$.

Cytoskeleton

An internal structural framework composed of protein microtubules and microfilaments that maintains cell shape, anchors and moves organelles, and enables nuclear division during mitosis and meiosis.

Centrioles

Paired cellular structures involved in organizing nuclear division (mitosis and meiosis) that are present in animal cells but absent in plant and fungal cells.

Plastids

A family of plant organelles (including chloroplasts, chromoplasts, and amyloplasts) involved in photosynthesis and storage; they are not present in animal or fungal cells.

Aseptate Fungal Hyphae

An atypical eukaryotic structure featuring continuous uninterrupted filamentous cytoplasm with multiple nuclei due to the complete lack of dividing septa.

Phloem Sieve Tube Elements

Specialized eukaryotic transport cells in vascular plants that lack a nucleus at functional maturity to facilitate fluid transport.

Electron Microscopy

A high-power imaging technique providing significantly higher magnification and resolution than light microscopy, allowing visualization of ultrastructures such as ribosomes.

Freeze Fracture

A specialized specimen preparation method where rapidly frozen biological samples are cracked open, allowing researchers to examine the internal arrangement of plasma membranes.

Cryogenic Electron Microscopy (Cryo-EM)

A technique that enables scientists to determine the three-dimensional structures of biomolecules and proteins that do not crystallize readily.

Immunofluorescence

A microscopic detection method that visualizes specific target proteins or antigens in cells by binding antibodies chemically linked to fluorescent dyes.

Magnification Formula

The mathematical formula $\text{Magnification} = \frac{\text{Image length}}{\text{Actual length}}$ ($M = \frac{I}{A}$), which rearranges to find actual specimen length as $\text{Actual length} = \frac{\text{Image length}}{\text{Magnification}}$ ($A = \frac{I}{M}$).

Stem Cell Niche

A microenvironment within an adult body that maintains stem cells in an undifferentiated state or stimulates them to proliferate and differentiate.

Hematopoietic Stem Cells

Multipotent stem cells situated in the bone marrow niche capable of differentiating into all types of blood cells.

Hair Follicle Stem Cell Niche

An adult stem cell niche containing epithelial, melanocyte, and mesenchymal stem cells that self-renew, differentiate, regulate hair growth, and preserve skin homeostasis.

Totipotent Stem Cells

Cells with the capacity to differentiate into any cell type, including both embryonic tissues and extraembryonic structures like the placenta, with the potential to form a complete organism (e.g., zygotes).

Pluripotent Stem Cells

Cells that can differentiate into almost any body cell type derived from embryonic lineages, but cannot independently develop into an embryo or placenta (e.g., embryonic stem cells).

Multipotent Stem Cells

Stem cells that are limited to differentiating into a discrete, related family of specialized cells, typical of adult tissue-specific stem cells.

Morphogens

Signaling chemicals whose concentration gradients regulate gene expression in a controlled manner, directing the differentiation of embryonic stem cells into distinct tissues.

Surface Area-to-Volume Ratio (SA:V)

The mathematical relationship between a cell's surface area (membrane) and volume (cytoplasm); as a cell grows, volume increases faster than surface area, lowering the ratio (e.g., from $6:1$ to $2:1$) and restricting cell size due to metabolic exchange limits.

Gamete Size Specialization

Differences in gamete morphology where human sperm are extremely small ($2\text{ to }3\text{ μm}$) to facilitate rapid mobility toward the ovum, while ova possess the largest volume ($100\text{ μm}$) to house nutrient reserves.

Integration of Body Systems

The physiological coordination of organs and systems via electrical nervous impulses, chemical endocrine signals, and circulatory transport to achieve unified organismal functioning.

Nervous System Signalling

Rapid, short-lived electrical impulses transmitted along specialized neurons targeting highly specific cells or tissues.

Endocrine System Signalling

Slower, longer-lasting communication mediated by chemical messengers (hormones) released by ductless glands into the bloodstream to target distant receptors across the body.

Hypothalamus and Pituitary Coordination

A central endocrine control system where the hypothalamus monitors bodily conditions, produces hormones stored in the posterior pituitary, and secretes regulatory hormones that stimulate release from the anterior pituitary.

Circadian Rhythms

Physical, mental, and behavioral cycles that follow an approximate $24\text{-hour}$ biological cycle in response to environmental cues.

Melatonin

A hormone produced by the pineal gland secreted during darkness that establishes and regulates sleep-wake diurnal cycles.

Epinephrine (Adrenaline)

A hormone produced by the adrenal glands that triggers the fight-or-flight response, priming the body for intense physical exertion and muscle contraction.

Baroreceptors

Stretch-sensitive mechanoreceptors situated in the aorta and carotid arteries that monitor arterial blood pressure and send signals to the medulla oblongata.

Chemoreceptors (Cardiovascular/Respiratory)

Sensory receptors located in the carotid artery and medulla that detect changes in blood chemistry, including levels of carbon dioxide, oxygen, and hydrogen ion concentration ($pH$).

Medullary Heart Rate Regulation

Autonomic reflex control wherein the medulla oblongata sends signals via cardiac nerves to the sinoatrial node (pacemaker) to increase heart rate and stroke volume during exercise, or decrease heart rate at rest.

Feedback Control of Ventilation Rate

The physiological mechanism where elevated cellular respiration raises $CO_2$ and carbonic acid levels, dropping blood $pH$ below normal ($7.38\text{ -- }7.48$), stimulating the medullary respiratory centre to adjust breathing rate and depth.

Autonomic Nervous System

The division of the nervous system responsible for regulating involuntary bodily functions without conscious oversight, including breathing rate, cardiac contractions, and digestion.

Enteric Nervous System (ENS)

A dedicated division of the autonomic nervous system embedded in the digestive tract that governs the involuntary propulsion and coordination of food through peristalsis.

Peristalsis

Coordinated involuntary waves of alternating muscle contraction and relaxation along the digestive tract from the oesophagus to the rectum that propel ingested material forward.

Homeostasis

The universal characteristic of living organisms involving active regulation to maintain physiological internal parameters within narrow, tolerable limits.

Metabolism

The sum total of all interdependent and interacting biochemical reactions occurring within a living organism.

Excretion

The biological process responsible for eliminating metabolic byproducts and chemical wastes from an organism, including removal via urine, sweat, and exhalation.