The Cell Organelles and Their Functions

Vocabulary-style flashcards covering organelles, their structures, functions, and related human diseases.

Plasma membrane

Defines cell boundaries and retains contents; two-layer phospholipid bilayer with proteins, carbohydrates, and cholesterol; proteins are amphipathic and include glycoproteins with oligosaccharides; functions include enzymes, anchors, transport, and receptors; cholesterol helps maintain membrane integrity; part of the fluid mosaic model.

Phospholipid bilayer

Two-layer arrangement where hydrocarbon tails face inward and phosphate-containing heads face outward, forming the basic structure of the plasma membrane.

Membrane proteins

Proteins embedded in the membrane that can act as enzymes, anchors, transporters, or receptors; many are amphipathic.

Glycoproteins

Membrane proteins with carbohydrate chains (oligosaccharides) attached; important for cell recognition and protection.

Cholesterol (in membranes)

Helps maintain membrane structural integrity and modulates fluidity, contributing to the fluid mosaic model.

Fluid mosaic model

describes the plasma membrane as a dynamic environment with lipids 'floating' in a fluid bilayer and proteins embedded throughout.

Nucleus

Information center of the cell; surrounded by a nuclear envelope with pores that regulate transport; contains nucleolus for RNA and ribosome assembly.

Nuclear envelope

Two membranes surrounding the nucleus; continuous with the endoplasmic reticulum.

Nuclear pores

Openings in the nuclear envelope that regulate the flow of macromolecules between the nucleus and cytoplasm.

Pore complex

Protein structure that lines nuclear pores and controls transport of substances.

Nucleolus

Nuclear region where synthesis and assembly of ribosomal RNA and ribosomal subunits occur.

Cytoplasm

Internal cell volume excluding the nucleus; contains organelles and cytosol.

Cytosol

Semifluid part of the cytoplasm in which organelles suspend; site of many cellular activities.

Mitochondrion

Site of aerobic respiration; contains two membranes, cristae, and a matrix; mtDNA; maternal inheritance in humans; number/location correlate with cellular role.

Cristae

Infoldings of the inner mitochondrial membrane that increase surface area for energy production.

Mitochondrial matrix

Semifluid interior of the mitochondrion where many enzymes reside.

mtDNA (mitochondrial DNA)

Circular DNA in mitochondria encoding some RNAs and proteins needed by mitochondria.

Maternal inheritance

Inheritance pattern in which mitochondria are passed from mother to offspring.

Chloroplast

Site of photosynthesis in plants and algae; larger than mitochondria; contains thylakoids and stroma; chloroplast DNA and ribosomes.

Thylakoids

Flattened membrane-bound sacs within chloroplasts where the light-dependent reactions occur.

Stroma

Semifluid matrix inside chloroplast where the Calvin cycle occurs; contains chloroplast ribosomes and DNA.

Chloroplast ribosomes

Ribosomes within chloroplasts (70S-like) that synthesize some chloroplast proteins.

Chloroplast DNA

Circular DNA within chloroplasts encoding some RNAs and proteins.

Endosymbiont theory

Idea that mitochondria and chloroplasts originated as free-living prokaryotes that were taken up by ancestral eukaryotic cells and became organelles.

Endoplasmic reticulum (ER)

A network of membranes throughout the cytoplasm; continuous with the nuclear envelope; can be rough or smooth.

Rough ER

ER surface studded with ribosomes; synthesizes secretory and membrane proteins.

Smooth ER

ER without ribosomes; involved in lipid and steroid synthesis and detoxification.

Golgi complex

Stack of flattened vesicles that processes, packages, and sorts secretory proteins and synthesizes some polysaccharides.

Lysosome

Single-membrane vesicle containing hydrolases for digesting macromolecules; enzymes are synthesized in the rough ER and processed in the Golgi.

Hydrolases

Digestive enzymes contained within lysosomes.

Peroxisome

Single-membrane organelle that generates and degrades hydrogen peroxide; involved in detoxification and fatty acid beta-oxidation; glyoxysomes in plants and photorespiration in leaves.

Glyoxysomes

Peroxisomes in plant fats-storing tissues that convert stored fats into carbohydrates during germination.

Photorespiration

Metabolic pathway prominent in photosynthetic tissue; involves peroxisomes in leaves.

Vacuole

In plants and yeast, a large central vacuole maintains turgor and stores solutes; in animals, vacuoles are smaller and used for storage and transport.

Ribosomes

Not an organelle; ribosomes are universal to cells; eukaryotic ribosomes are 80S in size.

Cytoskeleton

Internal framework that gives the cell shape and organization; essential for movement and division.

Microtubules

Largest cytoskeletal filaments; form axonemes of flagella/cilia and mitotic spindle; involved in intracellular transport.

Microfilaments

Smallest cytoskeletal filaments; role in muscle contraction, cell movement, and cleavage furrow during cytokinesis.

Intermediate filaments

Filaments between microfilaments and microtubules; highly stable; provide mechanical support and resist tension.

Organelles and human diseases

Many diseases arise from organelle malfunctions, including Leigh syndrome, Zellweger syndrome, adrenoleukodystrophy, and lysosomal storage diseases.

Mitochondrial disorders

Disorders due to mutations in mtDNA; often show maternal inheritance and involve many mitochondria per cell.

Peroxisomal disorders

Disorders caused by absence of a single peroxisomal protein; most peroxisomal diseases involve nuclear gene mutations; no peroxisomal DNA.

Zellweger syndrome (ZS)

A peroxisomal disorder resulting from defects in peroxisome biogenesis; example of peroxisomal disease.

NALD (neonatal adrenoleukodystrophy)

A peroxisomal disorder characterized by defects in very-long-chain fatty acid metabolism.

X-ALD (X-linked adrenoleukodystrophy)

A peroxisomal disorder inherited in an X-linked manner; disrupts fatty acid metabolism.

Lysosomal storage diseases

Over 40 inherited diseases caused by accumulation of substances due to deficient lysosomal enzymes (e.g., I-cell disease, Tay-Sachs).

I-cell disease

Lysosomal storage disease due to defect in N-acetylglucosamine phosphotransferase; lysosomal enzymes fail to be properly targeted.

Tay-Sachs disease

Lysosomal storage disease due to deficiency of beta-N-acetylhexosaminidase A; accumulation of GM2 ganglioside in nervous tissue.

GM2 ganglioside

Accumulated lipid in Tay-Sachs disease; toxic buildup in neurons.