Lesson 2: Cytoplam and Organelles

Comprehensive vocabulary flashcards detailing cytoplasm compartments, membrane structure, transport mechanisms, organelle functions, and related pathologies.

Cell

The basic functional unit of life, defined as a highly organized and dynamic entity where specific functions are localized within compartments.

Cytoplasm

The region encompassing everything between the plasma membrane and the nucleus, providing the environment where most metabolic activities occur.

Inclusions

Inactive cytoplasmic accumulations of substances such as lipids and glycogen.

Cytosol

The fluid portion of the cytoplasm containing water, ions, and soluble components.

Organelles

Active cellular structures localized in the cytoplasm, such as mitochondria and the rough endoplasmic reticulum, that perform specialized metabolic tasks.

Plasma Membrane

A lipid bilayer approximately $7.5$ to $10\text{ nm}$ thick that separates the cytoplasm from extracellular fluid and regulates the cell's internal environment through selective permeability.

Phospholipids

Amphipathic membrane lipids possessing hydrophilic heads and hydrophobic tails that arrange to form the membrane bilayer.

Cholesterol

Lipid molecules interspersed among phospholipids that function to stabilize membrane fluidity and mechanical properties.

Integral Proteins

Membrane proteins directly incorporated into the lipid bilayer that often span its entire width as transmembrane proteins.

Peripheral Proteins

Proteins bound to the membrane surface via ionic interactions, typically located on the cytoplasmic side.

Glycocalyx

A carbohydrate-rich outer layer formed by carbohydrate chains of glycoproteins and glycolipids projecting from the cell surface, acting as a cellular fingerprint for self-recognition.

Pumps

A class of membrane proteins that move ions such as $\text{Na}^+$ and $\text{K}^+$ across the membrane against concentration gradients.

Channels

Membrane proteins, such as aquaporins, that allow the passive passage of small molecules across the plasma membrane.

Receptors

Membrane proteins that bind specific extracellular ligands to initiate intracellular signaling pathways.

Linkers

Membrane proteins, such as integrins, that physically connect the internal cytoskeleton to the extracellular matrix (ECM).

Simple Diffusion

Passive transport process wherein small, nonpolar molecules such as $\text{O}_2$ and $\text{CO}_2$ pass directly through the lipid bilayer down concentration gradients.

Facilitated Diffusion

Passive transport that relies on carrier proteins or channels to transport larger or polar molecules across the membrane.

Osmosis

The diffusion of water across semipermeable membranes, frequently mediated by specialized channels known as aquaporins.

Active Transport

An energy-dependent transport process wherein transmembrane pumps expend ATP to move solutes against concentration gradients.

$$\text{Na}^+/\text{K}^+\text{ ATPase}$$

A primary active transport pump that consumes one ATP molecule to pump $3\text{ Na}^+$ ions out of the cell and $2\text{ K}^+$ ions into the cell, maintaining resting membrane potential and volume.

Endocytosis

A bulk transport mechanism where the cell membrane internalizes extracellular macromolecules into vesicles.

Exocytosis

A transport process in which intracellular vesicles fuse with the plasma membrane to secrete substances outside the cell.

Phagocytosis

A specific form of endocytosis involved in the cellular uptake or 'eating' of large particles and bacteria.

Pinocytosis

A form of endocytosis characterized by the uptake or 'drinking' of extracellular fluid and dissolved solutes.

Mitochondria

Double-membrane-bound organelles that generate ATP from food through oxidative phosphorylation.

Cristae

Infoldings of the inner mitochondrial membrane that expand surface area for electron transport chain components.

Cytochrome c

A mitochondrial protein released into the cytosol upon outer membrane permeabilization to activate caspases during apoptosis.

Mitochondrial DNA (mtDNA)

Circular, double-stranded genetic material located within the mitochondrial matrix that is inherited maternally.

Matrix Enzymes

Enzymes housed within the mitochondrial matrix that catalyze the citric acid (Krebs) cycle and fatty acid beta-oxidation.

Elementary Particles

ATP synthase complexes situated on mitochondrial cristae that synthesize ATP.

Ribosomes

Non-membrane-bound structures $20\text{ nm}$ in size composed of rRNA and proteins that carry out protein synthesis.

Dyskeratosis Congenita

A rare inherited genetic disorder caused by X-chromosome mutations leading to defective telomere maintenance and abnormal ribosome function, presenting with skin pigmentation, nail dystrophy, and oral leukoplakia.

Rough Endoplasmic Reticulum (RER)

A continuous membrane network of flat sacs called cisternae studded with surface ribosomes, dedicated to synthesizing and processing membrane and secretory proteins.

Cisternae

Flat, connected membrane-bound sacs that make up the structure of the rough endoplasmic reticulum.

Smooth Endoplasmic Reticulum (SER)

A network of tubular membranes devoid of ribosomes that synthesizes lipids and steroid hormones, detoxifies drugs in liver cells, and stores calcium ions.

Golgi Apparatus

An organelle discovered by Camillo Golgi that modifies, sorts, and packages proteins and lipids into vesicles for transport.

Lysosomes

Single membrane-bound organelles formed by the Golgi apparatus containing hydrolytic enzymes and an acidic interior for waste digestion.

Autophagy

The lysosomal degradation process of breaking down worn-out cellular organelles so their molecular components can be recycled.

Vacuoles

Membrane-bound storage spaces surrounded by the tonoplast that maintain water balance, regulate ion levels, and store nutrients or waste.

Tonoplast

The single membrane bounding a vacuole.

Cytoskeleton

A complex network of protein fibers extending throughout the cytoplasm that maintains cell morphology, anchors organelles, and enables cellular division.

Peroxisomes

Organelles containing hydrogen peroxide that execute oxidative reactions to breakdown fatty acids and detoxify harmful products.

Catalase

An enzyme located within peroxisomes that breaks down toxic hydrogen peroxide ($\text{H}_2\text{O}_2$) into non-hazardous products.

Zellweger Syndrome

A rare inherited metabolic condition where peroxisomes fail to form properly, impairing lipid metabolism and producing dysmorphic features similar to Trisomy 21.

Vesicles

Small, lipid bilayer-enclosed membrane sacs that store or transport substances between cellular compartments.

Transport Vesicles

Membrane sacs that shuttle proteins and lipids between organelles, notably between the ER and Golgi apparatus.

Secretory Vesicles

Vesicles originating from the Golgi apparatus that fuse with the plasma membrane to secrete enzymes, hormones, or neurotransmitters.

Lysosomal Vesicles

Vesicles responsible for directing target materials to cellular compartments designated for enzymatic degradation.

Endocytic Vesicles

Vesicles created by invaginations of the plasma membrane to deliver extracellular material into the cell interior.