Cell Structure, Function, and Energetics

Comprehensive vocabulary flashcards covering cell theory, prokaryotic and eukaryotic distinctions, organelle functions, membrane transport, cellular energetics (ATP, photosynthesis, cellular respiration, and fermentation), and Kingdom Protista.

Cell Theory

The foundational biological principle stating that all living organisms are composed of one or more cells, cells are the smallest functional units of life, and all new cells arise from preexisting cells through cell division.

Robert Hooke

The scientist who observed cork tissue under an early microscope and first coined the term "cells" to describe the microscopic box-like structures.

Matthias Schleiden

The scientist who contributed to cell theory by discovering and stating that all plants are composed of cells.

Theodor Schwann

The scientist who contributed to cell theory by identifying that all animals are made up of cells.

Rudolf Virchow

The scientist who established the third tenet of cell theory by determining that all cells arise solely from preexisting cells via cell division.

Prokaryotic Cell

A simple, single-celled organism lacking a nucleus and membrane-bound organelles, containing "naked" circular DNA in a nucleoid region, which first evolved approximately $3.5\text{ billion}$ years ago in domains Bacteria and Archaea.

Eukaryotic Cell

A structurally complex cell containing membrane-bound organelles and linear DNA enclosed in a nucleus, which evolved approximately $2.1\text{ billion}$ years ago and comprises domain Eukarya (kingdoms Protista, Plantae, Fungi, and Animalia).

Total Magnification

The total enlargement of a specimen viewed through a light microscope, calculated by the formula: $\text{Total Magnification} = \text{ocular magnification} \times \text{objective magnification}$.

Plant Cell vs. Animal Cell Structures

Plant cells possess rigid cell walls, chloroplasts, and a large central vacuole, whereas animal cells lack these structures, having instead centrioles, centrosomes, small or absent vacuoles, and an extracellular matrix.

Phospholipid Bilayer

The primary structural component of the plasma membrane, consisting of two layers of phospholipids arranged with hydrophilic heads facing outward and inward toward water, and hydrophobic fatty acid tails pointing inward away from water, embedded with proteins.

Nucleus

The membrane-bound control center of a eukaryotic cell enclosed by a nuclear envelope, which protects chromatin ($\text{DNA}$ and proteins) and directs cellular activities.

Ribosome

A non-membrane-bound cellular structure found suspended in cytoplasm or attached to the rough endoplasmic reticulum in both prokaryotes and eukaryotes that synthesizes proteins using genetic instructions from $\text{DNA}$.

Endoplasmic Reticulum (ER)

An extensive membranous organelle continuous with the nuclear envelope; rough ER is studded with ribosomes and modifies proteins to be secreted via transport vesicles, while smooth ER lacks ribosomes and synthesizes lipids.

Golgi Apparatus

An organelle consisting of flattened membranous sacs that receives, modifies, sorts, and packages cellular products from the endoplasmic reticulum for export or intracellular delivery.

Lysosome

A membrane-bound organelle containing digestive enzymes that breaks down nutrients, cellular waste, foreign debris, and damaged cell components.

Mitochondrion

An organelle enclosed by double membranes with folded inner cristae and a fluid matrix, found in all eukaryotes to conduct cellular respiration and generate energy in the form of $ATP$.

Chloroplast

A double-membraned organelle unique to plants and photosynthetic autotrophs containing thylakoids and stroma, which harvests sunlight energy to synthesize sugars during photosynthesis.

Cytoskeleton

An internal framework of protein fibers and microtubules that maintains cell shape and enables cellular movement, such as the crawling locomotion of an Amoeba.

ATP (Adenosine Triphosphate)

The primary energy currency for cellular work, consisting of adenosine bound to three phosphate groups, which releases usable energy and converts to adenosine diphosphate ($ADP$) and inorganic phosphate ($P$).

Passive Transport

The movement of substances across a biological membrane down their concentration gradient (from high to low concentration) without any expenditure of cellular energy.

Facilitated Transport

The passive transport of specific solutes across a membrane down their concentration gradient assisted by embedded channel or carrier proteins, requiring no energy.

Aquaporin

A specialized membrane channel protein that enables the rapid, facilitated diffusion of water molecules across the plasma membrane.

Osmosis

The passive diffusion of water across a semipermeable membrane from an area of higher water concentration (lower solute concentration) to an area of lower water concentration (higher solute concentration).

Isotonic Solution

A solution in which the solute concentration outside the cell equals that inside the cell, resulting in water moving in and out at equal rates and no change in cell volume.

Hypotonic Solution

A solution with a lower solute concentration compared to the cell interior, causing net water flow into the cell and leading animal cells to swell and plant cells to become firm and healthy.

Hypertonic Solution

A solution with a higher solute concentration compared to the cell interior, causing water to diffuse out of the cell, resulting in cell shrinkage or plant wilting.

Turgor Pressure

Active Transport

The movement of ions or molecules across a plasma membrane against their concentration gradient (from low to high concentration), mediated by transport proteins and requiring energy in the form of $ATP$.

Sodium-Potassium Pump

An active transport protein that hydrolyzes $ATP$ to pump three sodium ions ($3\,Na^+$) out of the cell and two potassium ions ($2\,K^+$) into the cell against their respective concentration gradients.

Endocytosis and Exocytosis

Forms of active transport for bulk materials; endocytosis folds the cell membrane inward to package extracellular substances into vesicles, whereas exocytosis fuses intracellular vesicles with the membrane to release substances outside.

Photosynthesis

The biochemical process occurring in chloroplasts where plants and autotrophs convert light energy into chemical energy, summarized by the equation: $6\,CO_2 + 6\,H_2O \rightarrow C_6H_{12}O_6 + 6\,O_2$.

Light Reactions

The initial stage of photosynthesis taking place in the thylakoids of chloroplasts, where light energy split water ($H_2O$) to release oxygen ($O_2$) while generating $ATP$ and $NADPH$.

Calvin Cycle

The light-independent reactions of photosynthesis occurring in the chloroplast stroma, using $ATP$ and $NADPH$ generated by light reactions to fix carbon dioxide ($CO_2$) into glucose ($C_6H_{12}O_6$).

Chlorophyll

The primary photosynthetic pigment in plants that absorbs violet, blue, and red wavelengths while transmitting and reflecting green light, giving plant leaves their green color.

Stoma (Stomata)

Microscopic openings on the lower leaf epidermis bordered by guard cells that regulate gas exchange ($CO_2$ in, $O_2$ out) and transpiration.

Carbonic Acid ($H_2CO_3$)

An acidic substance produced when carbon dioxide dissolves in water according to the equilibrium reaction: $H_2O + CO_2 \rightleftharpoons H_2CO_3$, lowering the solution's pH.

Cellular Respiration

The aerobic metabolic process occurring primarily in eukaryotic mitochondria that breaks down glucose in the presence of oxygen to produce $ATP$, releasing carbon dioxide ($CO_2$) and water ($H_2O$).

Glycolysis

The first, anaerobic stage of cellular respiration occurring in the cytoplasm, where one 6-carbon glucose molecule is split into two 3-carbon pyruvic acid (pyruvate) molecules with a net yield of $2\,ATP$ and $2\,NADH$.

Krebs Cycle (Citric Acid Cycle)

The second, aerobic stage of cellular respiration located in the mitochondrial matrix that processes pyruvate derivatives, releasing carbon dioxide while generating $ATP$, $NADH$, and other electron carriers.

Electron Transport Chain (ETC)

The final stage of aerobic cellular respiration located on the inner mitochondrial membrane that uses high-energy electrons transferred by $NADH$ to drive the synthesis of large amounts of $ATP$, combining electrons with oxygen and hydrogen to produce water.

Lactic Acid Fermentation

An anaerobic pathway occurring in human muscle tissue during oxygen deprivation that regenerates $NAD^+$ by converting pyruvic acid into lactic acid, yielding $2\,ATP$ through glycolysis and contributing to muscle fatigue.

Alcoholic Fermentation

An anaerobic metabolic process performed by yeasts and certain bacteria that converts pyruvic acid from glycolysis into ethyl alcohol and carbon dioxide ($CO_2$) while recycling $NAD^+$ and producing $2\,ATP$.

Kingdom Protista

A diverse eukaryotic kingdom containing unicellular or simple multicellular organisms that exhibit animal-like (heterotrophic motile), plant-like (photosynthetic autotrophs), or fungus-like characteristics.

anaerobic respiration vs aerobic respiraiton

Anaerobic respiration occurs in the absence of oxygen and includes processes like lactic acid and alcoholic fermentation, producing less energy compared to aerobic respiration, which uses oxygen to fully oxidize glucose into carbon dioxide and water, yielding significantly more ATP.

ATP vs ADP

ATP (adenosine triphosphate) is the primary energy carrier in cells, consisting of adenine, ribose, and three phosphate groups, while ADP (adenosine diphosphate) is a low-energy molecule formed when one phosphate group is removed from ATP.

basics of each stage of Photosynthesis

Photosynthesis consists of two main stages: the light-dependent reactions, which convert light energy into chemical energy (ATP and NADPH) and take place in the thylakoid membranes, and the light-independent reactions (Calvin cycle), which use ATP and NADPH to convert carbon dioxide into glucose in the stroma.

basics of each stage of respiraiton

Respiration involves two main stages: glycolysis, which breaks down glucose into pyruvate in the cytoplasm, and aerobic cellular respiration (or fermentation in anaerobic conditions), which fully oxidizes pyruvate in the mitochondria to produce ATP, carbon dioxide, and water.