CH 4 CELL STRUCTURE AND FUNCTION ACTUAL

Robert Hooke (1665)

English scientist who observed thin slices of cork under a microscope and coined the term 'cell' (from Latin 'cella' meaning small room).

The Three Tenets of Cell Theory

1. All organisms are composed of one or more cells (Schleiden & Schwann). 2. The cell is the basic structural and functional unit of life (Schleiden & Schwann). 3. All cells arise from preexisting cells through cell division (Virchow).

Surface Area to Volume Ratio

Natural physical constraint dictating that smaller cells have a higher surface-to-volume ratio ($\text{SA}:\text{V}$), enabling efficient metabolic exchange of nutrients ($\text{O}_2$) and wastes ($\text{CO}_2$) across the membrane.

Prokaryotic Cell Structure

Simple, small ($0.1\text{--}10\,\mu\text{m}$) cells lacking a membrane-bound nucleus and organelles; contains circular DNA in a nucleoid region, ribosomes, peptidoglycan cell wall, and motility flagella.

Eukaryotic Animal Cell

Complex, compartmentalized eukaryotic cell characterized by a nucleus, endomembrane organelles, centrioles, and lysosomes, lacking a cellulose cell wall and chloroplasts.

Eukaryotic Plant Cell

Eukaryotic cell distinguished by photosynthetic chloroplasts, a rigid extracellular cellulose cell wall, plasmodesmata, and a large central vacuole with tonoplast.

Cytoskeleton

Network of internal protein fibers supporting cell shape; consists of solid helical microfilaments (composed of actin) and hollow microtubules (composed of tubulin).

Centrioles

Microtubule-based organelles occurring in pairs within animal cells that organize spindle fibers during mitosis to separate copies of chromosomes.

The Nucleus

Control center of eukaryotic cells bounded by a double-membraned nuclear envelope with pores; houses the nucleolus (ribosome synthesis) and genetic material in chromatin.

Rough Endoplasmic Reticulum (RER)

Endomembrane system organelle studded with bound ribosomes; synthesizes, modifies, and folds secretory and membrane proteins before packaging them into transport vesicles.

Smooth Endoplasmic Reticulum (SER)

Tubular network lacking ribosomes; functions in lipid synthesis (steroids, phospholipids), carbohydrate metabolism, calcium ion storage in muscle, and liver detoxification.

Ribosomes

Non-membrane-bound complexes of ribosomal RNA (rRNA) and proteins consisting of large and small subunits; carry out cellular protein synthesis in cytosol or bound to RER.

Golgi Apparatus

Stack of flattened membranous sacs (cisternae); receives ER transport vesicles at its cis face, modifies and sorts molecules, and pinches off secretory vesicles from its trans face.

Lysosome

Digestive vesicle formed by the Golgi apparatus packed with hydrolytic enzymes; digests phagocytosed food particles, neutralizes pathogens, and recycles defective organelles.

Central Vacuole

Prominent fluid-filled plant organelle enclosed by the tonoplast; stores water, ions, nutrients, and pigments while exerting turgor pressure to maintain plant cell rigidity.

Mitochondria

Double-membrane organelle found in aerobic eukaryotes; executes cellular respiration, oxidizing glucose to generate energy currency in the form of $\text{ATP}$.

Chloroplast

Double-membrane photosynthetic plastid in plants and algae containing chlorophyll, fluid stroma, and thylakoid membranes organized into grana to synthesize sugars using light.

Endosymbiotic Theory

Evolutionary theory stating that eukaryotic mitochondria and chloroplasts originated when ancestral host cells engulfed independent aerobic and photosynthetic bacteria.

Plasma Membrane

Selectively permeable fluid mosaic lipid bilayer embedded with integral and peripheral proteins, glycoproteins, and cholesterol that regulates substance transport into and out of the cell. ![Membrane structure](https://assets.knowt.com/pdf-flow-prod/f5bbb7a1-1cde-4482-971d-6108e

Cell Theory

A fundamental biological theory stating that: 1. All living organisms are composed of one or more cells. 2. The cell is the basic structural and functional unit of life. 3. All cells arise from preexisting cells through cellular division.

Robert Hooke

English scientist who discovered cells in 1665 while observing a thin slice of cork under a microscope, naming them after the Latin word 'cella' meaning small room.

Anton van Leeuwenhoek

Microbiologist who used a handmade microscope in 1673 to observe pond scum, discovering single-celled organisms he termed 'animalcules', as well as observing blood cells in various animals.

Matthias Schleiden & Theodor Schwann

German scientists who formulated the first two tenets of cell theory; Schleiden concluded in 1838 that all plant parts consist of cells, and Schwann stated in 1839 that all animal tissues consist of cells.

Rudolf Virchow

German physician who concluded in 1858 that cells must arise from preexisting cells, completing the classical cell theory.

Surface Area to Volume Ratio

The relationship that limits cell size; smaller cells possess a higher surface area to volume ratio, facilitating the efficient exchange of nutrients, gases, and wastes across the plasma membrane.

Prokaryotic Cell

A simple, small, unicellular organism lacking a membrane-bound nucleus and membrane-bound organelles, with DNA concentrated in an unbound region termed the nucleoid.

Eukaryotic Cell

A complex cell containing a membrane-bound nucleus housing the cell's genetic material, along with specialized membrane-bound organelles compartmentalizing cellular processes.

Plasma Membrane

A selectively permeable phospholipid bilayer embedded with proteins that encloses the cell, regulating the entry and exit of substances.

Nucleus

The control center of a eukaryotic cell, enclosed by a double-membrane nuclear envelope with pores, containing chromatin and the nucleolus.

Nucleolus

A dense region located inside the nucleus responsible for the production and assembly of ribosomes.

Ribosomes

Complexes composed of ribosomal RNA and proteins that carry out protein synthesis; they can float freely in the cytosol or bind to the rough endoplasmic reticulum.

Rough Endoplasmic Reticulum (RER)

A network of interconnected flattened sacs studded with ribosomes that synthesizes, folds, and modifies secretory proteins and membranes.

Smooth Endoplasmic Reticulum (SER)

A tubular membrane network lacking ribosomes that synthesizes lipids, metabolizes carbohydrates, detoxifies toxins, and stores calcium ions.

Golgi Apparatus

A stack of unconnected flattened membranous sacs called cisternae that modifies, sorts, packages, and ships proteins and lipids received from the endoplasmic reticulum via transport vesicles.

Lysosome

A membrane-bound vesicle containing hydrolytic digestive enzymes produced by the Golgi apparatus that digests macromolecules, cellular debris, and foreign pathogens.

Central Vacuole

A large organelle in plant cells enclosed by the tonoplast that stores water, organic compounds, and wastes, while maintaining cellular turgor pressure.

Mitochondria

Double-membrane organelles present in nearly all eukaryotic cells that perform cellular respiration, converting biochemical energy from glucose into ATP.

Chloroplast

• contains the pigment chlorophyll

• Use light energy to make carbohydrates – photosynthesis

• are found in leaves and other green organs of plants and in algae