Exploring Life, Science, and Cell Structure & Function

Comprehensive vocabulary flashcards generated from lecture notes on biology principles, scientific methodology, cell theory, membrane transport, cell organelles, and cellular energetics.

Biology

The science and study of living organisms and the environments they live in.

Energy

The capacity to do work.

Metabolism

The sum of all the chemical reactions that occur within a cell or organism.

Photosynthesis

A process used by plants, algae, and some bacteria to harvest energy from the sun and convert it into chemical energy, producing sugars as the basis of the food chain.

Homeostasis

The state of maintaining a constant internal environment within narrow physiological values.

Growth

An increase in size and in the overall number of cells within an organism.

Development

All the changes that occur in an organism from fertilization until death, including childhood, adolescence, adulthood, and repair after injury.

DNA (Deoxyribonucleic Acid)

The genetic information of all life containing hereditary information that directs the structure and function of all cells.

Genes

Short segments of DNA that specify traits.

Mutations

Variations in genes that can be beneficial and make an organism better suited for its environment.

Evolution

How a population changes over time.

Natural Selection

The process by which evolution occurs when a new variation allows organisms to capture more resources, enabling those individuals to produce more offspring.

Adaptation

An advantageous variation that becomes present in a larger portion of a population over time.

Prokaryotes

Single-celled organisms, belonging to domains Bacteria and Archaea, that lack a membrane-bound nucleus.

Eukaryotic Cells

Cells that contain a nucleus, found in single-celled or multicellular eukaryotic organisms.

Invertebrates

Animals that lack an internal skeletal support structure, such as vertebrae (e.g., earthworms, insects, and mollusks).

Vertebrates

Animals that have a nerve cord protected by a vertebral column (e.g., fish, reptiles, amphibians, birds, and mammals).

Mammals

Vertebrates characterized by having hair or fur and mammary glands.

Science

A systematic way of knowing about and acquiring knowledge regarding the natural world.

Inductive Reasoning

A process of creative thinking used to combine isolated facts into a cohesive whole.

Deductive Reasoning

Logic that uses "if, then" statements to make testable predictions based on a hypothesis.

Hypothesis

A possible explanation for the observation of a natural event.

Scientific Theory

An accepted explanation for how the world works, supported by experimental evidence (e.g., cell theory).

Law (or Principle)

A scientific explanation or description accepted by an overwhelming majority of scientists (e.g., evolution).

Technology

The application of scientific knowledge to the interests and practical needs of humans.

Climate Change

Changes in the normal cycles of Earth's climate due to human activity, largely stemming from an imbalance in the chemical cycling of carbon.

Global Warming

An increase in global temperatures due to rising concentrations of atmospheric $\text{CO}_2$.

Biodiversity

The total number and relative abundance of species, the variability of their genes, and the different ecosystems in which they live.

Extinction

The complete death of a species.

Emerging Diseases

Relatively new diseases, such as avian influenza ($\text{H5N1}$, $\text{H7N9}$), swine flu ($\text{H1N1}$), SARS, MERS, and COVID-19 caused by SARS-CoV-2.

Reemerging Diseases

Diseases known for some time and considered low risk that reemerge via occasional outbreaks, such as Ebola.

Cell Theory

The fundamental concept that the cell is the basic unit of life, all living things are made up of cells, and new cells arise only from preexisting cells.

Surface-Area-to-Volume Ratio

The quantitative relationship limiting cell size, where smaller cells maintain a larger surface area relative to volume to allow efficient nutrient entry and waste disposal.

Compound Light Microscope

A laboratory instrument that uses glass lenses and light rays to view live or prepared specimens at lower magnification.

Transmission Electron Microscope (TEM)

An electron microscope that uses a stream of electrons to project a high-magnification $2\text{-D}$ image onto a screen; cannot view live specimens.

Scanning Electron Microscope (SEM)

An electron microscope that uses a beam of electrons to magnify surface structures, producing a high-magnification $3\text{-D}$ image; cannot view live specimens.

Plasma Membrane

A selectively permeable phospholipid bilayer with attached and embedded proteins that surrounds the cell and regulates what enters and exits.

Cytoplasm

The semifluid substance inside a cell containing internal compartments called organelles.

Endosymbiosis

The process by which eukaryotic organelles are thought to have developed from early eukaryotes engulfing prokaryotic cells.

Fluid-Mosaic Model

A representation of the plasma membrane where embedded proteins move laterally within a fluid phospholipid bilayer that contains cholesterol, glycoproteins, and glycolipids.

Aquaporins

Specialized channel proteins in the plasma membrane that allow water molecules to cross.

Diffusion

The passive movement of molecules from an area of higher concentration to an area of lower concentration until equilibrium is reached.

Osmosis

The diffusion of water molecules across a selectively permeable membrane from higher water concentration to lower water concentration.

Isotonic Solution

A solution that has the same concentration of impermeable solutes as body cells, resulting in no net change in cell volume.

Hypotonic Solution

A solution containing a lower concentration of solutes than body cells, causing cells to gain water, swell, and potentially burst (lysis).

Hypertonic Solution

A solution containing a higher concentration of solutes than body cells, causing cells to lose water and shrink (crenation).

Facilitated Diffusion

Passive transport of specific molecules across the plasma membrane from higher to lower concentration using a carrier protein.

Active Transport

The energy-requiring (ATP) movement of molecules against their concentration gradient (from lower to higher concentration) via carrier proteins called pumps.

Sodium–Potassium Pump

An active transport carrier protein present in all body cells that pumps sodium ions ($\text{Na}^+$) out of the cell and potassium ions ($\text{K}^+$) into the cell.

Endocytosis

The process of transporting molecules or cells into the cell via the invagination of the plasma membrane to form a vesicle.

Phagocytosis

A specific type of endocytosis where white blood cells engulf foreign pathogens such as bacteria.

Pinocytosis

A type of endocytosis where a cell engulfs fluids containing small dissolved particles.

Receptor-Mediated Endocytosis

A form of endocytosis initiated when target particles bind to specific receptor proteins located in the plasma membrane.

Exocytosis

The cellular transport process of exporting molecules outside the cell by fusing a vesicle with the plasma membrane.

Chromatin

The accessible, uncoiled form of DNA and proteins found within the nucleus during interphase when the cell is not dividing.

Nucleolus

A specialized dark region within the nucleus where ribosomes are synthesized.

Endomembrane System

A collective network of membranous organelles—including the nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, and vesicles—that process, package, and transport cellular materials.

Rough Endoplasmic Reticulum (RER)

A membranous network studded with ribosomes on its cytoplasm-facing surface, specialized for protein synthesis.

Smooth Endoplasmic Reticulum (SER)

A membranous network lacking ribosomes that synthesizes lipid molecules.

Golgi Apparatus

A stack of flattened membranous sacs responsible for modifying, processing, packaging, and secreting proteins and lipids.

Lysosomes

Membranous vesicles created by the Golgi apparatus containing hydrolytic enzymes used to digest macromolecules and cellular debris.

Cytoskeleton

An internal structural network of protein fibers—microtubules, intermediate filaments, and actin filaments—that maintains cell shape and facilitates movement of organelles.

Microtubules

The largest structural protein fibers of the cytoskeleton, organized by centrosomes, which serve as organelle tracks and form the spindle apparatus during cell division.

Actin Filaments

Long, extremely thin cytoskeleton components made of actin protein that participate in structural support and cellular movement.

Intermediate Filaments

Cytoskeletal protein fibers intermediate in size between actin filaments and microtubules.

Extracellular Matrix (ECM)

A protective external meshwork composed of proteins (collagen, elastin, fibronectin) and polysaccharides secreted by animal cells.

Adhesion Junctions

Intercellular junctions that physically attach the cytoskeletons of adjacent cells together.

Tight Junctions

Intercellular connections that form an impermeable barrier between adjacent cells.

Gap Junctions

Intercellular structures formed by the fusion of membrane channels between neighboring cells to allow direct communication and molecule exchange.

Feedback Inhibition

A regulatory mechanism where the final product of a metabolic pathway binds to an early enzyme, slowing reaction rates to prevent overproduction.

Active Site

The specific region of an enzyme where substrate molecules bind to undergo a catalyzed chemical reaction.

Mitochondria

Double-membrane organelles that convert chemical energy stored in glucose into ATP through cellular respiration.

Cellular Respiration

An aerobic metabolic pathway in cells that breaks glucose down into carbon dioxide and water, releasing energy to synthesize $36$ to $38\text{ ATP}$.

Glycolysis

An anaerobic pathway occurring in the cytoplasm that breaks a 6-carbon glucose molecule into two 3-carbon pyruvates, yielding NADH and $2\text{ ATP}$.

Citric Acid Cycle (Krebs Cycle)

A cyclical series of enzymatic reactions in the mitochondrial matrix that processes acetyl CoA, releases $\text{CO}_2$, and generates NADH, $\text{FADH}_2$, and $2\text{ ATP}$.

Electron Transport Chain

A series of carrier proteins embedded in the mitochondrial cristae that pass high-energy electrons down to oxygen (the final acceptor) to form water and generate the bulk of cellular ATP.

Fermentation

An anaerobic metabolic pathway that occurs in the absence of oxygen, yielding $2\text{ ATP}$ per glucose alongside toxic lactate.