Lecture 4 summary student voice memo: How Exhaustive Study Guide: Cell Biology, Organelles, and Membrane Dynamics

Vocabulary terms and definitions extracted from lecture notes covering cell structure, organelles, membrane components, and transport mechanisms.

Prokaryotic cells

Cells that lack a membrane-bound nucleus and are structurally simple, metabolically diverse, and generally unicellular.

Eukaryotic cells

Structurally complex cells possessing a membrane-bound nucleus and membrane-bounded organelles, making up animals, plants, fungi, and protists.

Archaea

Unicellular prokaryotes that possess unique membrane-spanning lipids, enabling them to survive in extreme conditions of heat, pH, and salinity.

Bacillus

A rod-shaped bacterium that can occur in pairs or chains.

Coccus

A spherical-shaped bacterium that can occur in pairs, chains, or clusters.

Spirilla

Long bacterial rods twisted into rigid spirals.

Peptidoglycan

The material that forms the cell wall in bacteria, located outside of the plasma membrane.

Capsule

A well-organized gelatinous sheath surrounding the cell wall of some bacteria that is not easily washed off.

Flagellum

A long, thin protein extension used for movement in some bacteria and sperm cells.

Fimbriae

Short appendages on some bacteria that help them attach to appropriate surfaces.

Nucleoid

A region in the cytoplasm of prokaryotes where a single bacterial chromosome is located; it is not surrounded by a membrane.

Thylakoids

Membranes of flattened discs that contain light-sensitive pigments in cyanobacteria.

Cell envelope

The outer structure of a cell that consists of the plasma membrane, cell wall, and glycocalix.

Glycocalyx

A layer of polysaccharides outside the cell wall of some bacteria that aids against drying out, provides immunity resistance, and helps bacteria attach to surfaces.

Polysaccharide

A complex carbohydrate macromolecule composed of repeating monosaccharide units, forming structural components like cellulose in plant cell walls and glycocalix in bacterial cell envelopes.

Cytoplasm

The semi-fluid medium inside a cell composed of water, salts, and dissolved organic molecules.

Plasmids

Extra-chromosomal pieces of circular DNA found in many prokaryotes.

Conjugation pili

Rigid tubular structures used by prokaryotes to pass DNA directly from cell to cell.

Cellulose

The main constituent of the primary cell wall in plant cells.

Lignin

A chemical compound found in the secondary cell walls of plant cells.

Chitin

The structural polysaccharide that composes the cell walls of fungi.

Components of the eukaryotic nucleus

The nuclear envelope (punctuated by nuclear pores), nucleoplasm, chromatin (composed of DNA and proteins), and the nucleolus.

Rough Endoplasmic Reticulum (RER)

A network of folded membranes studded with ribosomes involved in the synthesis, folding, modification, and transport of proteins.

Smooth Endoplasmic Reticulum (SER)

A network of folded membranes lacking ribosomes that synthesizes lipids and carbohydrates and detoxifies chemicals.

Golgi apparatus

A stack of 3 to 20 small membranous sacs that acts as the cell shipping center for processing, packaging, and distributing proteins and lipids.

Lysosomes

Membranous vesicles found only in animal cells that contain hydrolytic digestive enzymes for intracellular digestion and garbage disposal.

Peroxisomes

Membrane-bound vesicles containing specific enzymes like catalase that break down fatty acids and convert produced $H_2O_2$ into water and oxygen.

Mitochondria

Double membrane-bound organelles that perform cellular respiration to produce usable cell energy in the form of ATP.

Chloroplasts

Double membrane-bound organelles in plants and algae that use solar energy to synthesize carbohydrates via photosynthesis.

Photosynthesis chemical equation

The reaction represented by $6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6 + 6O_2$, in which solar energy, carbon dioxide, and water are converted into glucose and oxygen.

Cellular respiration chemical equation

The reaction represented by $C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{ATP}$, which is the reverse of photosynthesis and breaks down carbohydrates to generate ATP energy.

Relationship between photosynthesis and cellular respiration equations

They are exact chemical reverse processes: photosynthesis uses $CO_2$ and $H_2O$ with solar energy to form $C_6H_{12}O_6$ and $O_2$, whereas cellular respiration breaks down $C_6H_{12}O_6$ and $O_2$ to release $CO_2$, $H_2O$, and ATP.

Ultimate source of energy for most cells

Solar energy, which plants, algae, and cyanobacteria capture during photosynthesis to construct carbohydrates.

Stroma

The inner fluid-filled space of a chloroplast bounded by a double membrane, containing circular DNA and ribosomes.

Grana

Structures composed of stacked, coin-like thylakoid sacs within chloroplasts.

Cytoskeleton

An internal framework consisting of actin filaments, intermediate filaments, and microtubules that maintains cell shape and assists in component movement.

Actin filaments

Two long, thin, flexible actin chains twisted in a helix that provide structural support beneath the plasma membrane and interact with myosin for cell movement.

Intermediate filaments

Cytoskeletal structures intermediate in size that support the nuclear envelope and assist in forming cell-to-cell junctions.

Microtubules

Hollow cylinders made of globular tubulin that interact with motor molecules like kinesin and dynein to move organelles and form the spindle apparatus.

Homeostasis

The maintenance of a steady internal environment within a cell or organism.

Hydrophilic

Water-loving properties possessed by the polar heads of plasma membrane phospholipids.

Hydrophobic

Water-fearing properties possessed by the nonpolar tails of plasma membrane phospholipids.

Channel proteins

Membrane proteins that form pores allowing specific molecules or ions to cross the plasma membrane freely down a concentration gradient.

Carrier proteins

Membrane proteins that selectively interact with and combine with a specific molecule or ion to assist its passage across the membrane.

Cell recognition proteins

Glycoproteins (such as MHC proteins) on the cell surface that enable the immune system to distinguish self cells from invading pathogens.

Receptor proteins

Proteins shaped specifically for binding particular molecules, triggering a change in shape that initiates a cellular response.

Enzymatic proteins

Membrane proteins that directly catalyze specific metabolic reactions, such as ATP metabolism.

Aquaporins

Specialized channel proteins that facilitate the rapid passage of water molecules across the plasma membrane.

Diffusion

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

Osmosis

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

Isotonic solution

A solution in which the solute concentration is equal inside and outside the cell, resulting in no net water movement.

Hypotonic solution

A solution with a lower solute concentration than the inside of a cell, causing water to enter the cell.

Hypertonic solution

A solution with a higher solute concentration than the inside of a cell, causing water to leave the cell.

Cytolysis

The swelling and bursting of a cell resulting from excessive water intake in a hypotonic solution.

Crenation

The shriveling of an animal cell caused by water loss in a hypertonic solution.

Plasmolysis

The shrinking of the cytoplasm away from the cell wall in plant cells placed in a hypertonic solution.