Cell Biology - Cell Organelles

Standardized Test - 2 Syllabus

Cytoplasm

Part of the cell between the nucleus and the cell membrane. Contains cytosol and trophoplasm

Cytosol

Liquid matrix of cytoplasm, excluding organelles. Also called hyaloplasm or ground plasm

Trophoplasm

Part of cytoplasm containing organelles and non-living inclusions

Endomembrane System

System of interconnected membranous organelles: ER, Golgi, lysosomes, vacuoles (coordinated functions)

Endoplasmic Reticulum

Network of tubules and sacs in cytoplasm; RER (with ribosomes) for protein synthesis, SER (no ribosomes) for lipid synthesis & detoxification

Rough Endoplasmic Reticulum

ER with ribosomes attached to its surface; primarily involved in protein synthesis and secretion

Smooth Endoplasmic Reticulum

ER lacking ribosomes; involved in lipid synthesis, glycogen metabolism, and detoxification

Golgi Complex

Stack of flattened sacs (cisternae) for modifying, sorting, and packaging proteins and lipids for secretion or delivery to other organelles. Also called Golgi body or dictyosomes.

Cis face of Golgi

The receiving side of the Golgi apparatus, typically oriented towards the endoplasmic reticulum.

Trans-face of Golgi

The shipping side of the Golgi apparatus, typically oriented towards the cell membrane.

Lysosome

Membrane-bound organelle containing hydrolytic enzymes for intracellular digestion.

Acid Hydrolases

Digestive enzymes found within lysosomes, which function optimally at an acidic pH

Vacuole

Membrane-bound sac in the cytoplasm used for storage (water, nutrients, waste); the large central vacuole in plants also helps maintain turgor.

Tonoplast

The membrane that surrounds the central vacuole in plant cells, regulating transport in and out.

Autophagy

A cellular process where lysosomes digest old or damaged cell organelles.

Mitochondria

Double-membraned organelle responsible for aerobic respiration and ATP production; the "powerhouse of the cell."

Cristae

Infoldings of the inner mitochondrial membrane, increasing surface area for cellular respiration.

Mitochondrial Matrix

The fluid-filled inner compartment of a mitochondrion, containing enzymes, DNA, and ribosomes.

Outer Mitochondrial Membrane

The smooth outer boundary of the mitochondrion.

Inner Mitochondrial Membrane

The inner membrane of the mitochondrion, folded into cristae and containing components of the electron transport system.

Plastids

Double-membraned organelles found in plant cells and euglenoids, involved in pigment storage and/or photosynthesis.

Chloroplast

A type of plastid containing chlorophyll, the primary site of photosynthesis in plant cells.

Thylakoids

Flattened, membrane-bound sacs within the chloroplast stroma, arranged in stacks called grana, where the light-dependent reactions of photosynthesis occur.

Grana

Stacks of thylakoids within a chloroplast.

Stroma

The fluid-filled space within a chloroplast surrounding the grana, where the light-independent reactions (Calvin cycle) of photosynthesis take place.

Chromoplast

A type of plastid containing carotenoid pigments, responsible for yellow, orange, or red colors in plants.

Leucoplast

A colorless type of plastid involved in the storage of starch (amyloplast), oils (elaioplast), or proteins (aleuroplast).

Amyloplast

A type of leucoplast that stores starch, common in storage organs like potato tubers.

Ribosomes

Small, non-membraned organelles responsible for protein synthesis.

80S Ribosomes

Larger ribosomes found in the cytoplasm of eukaryotic cells.

70S Ribosomes

Smaller ribosomes found in prokaryotic cells, as well as in mitochondria and chloroplasts of eukaryotes.

Subunits of Ribosomes

Ribosomes are composed of a large and a small subunit (e.g., 80S = 60S + 40S; 70S = 50S + 30S).

rRNA

Ribosomal RNA, a key component of ribosomes along with proteins.

Polyribosome

A complex of multiple ribosomes attached to a single mRNA molecule, allowing for the efficient synthesis of multiple copies of a protein.

Svedberg Unit (S)

A unit used to measure the sedimentation rate of particles during centrifugation, indirectly indicating size and density.

Semi-autonomous Organelles

Organelles like mitochondria and chloroplasts that have their own DNA and ribosomes, allowing them to synthesize some of their own proteins.

Photosynthesis

The process by which green plants and some other organisms use sunlight to synthesize foods with the help of chlorophyll.

Chlorophyll

The green pigment in chloroplasts that absorbs light energy for photosynthesis.

Carotenoids

Accessory pigments found in chloroplasts and chromoplasts that can absorb light energy and contribute to colors like yellow, orange, and red.

Stroma Lamellae

Membranous tubules that connect the thylakoids of different grana within a chloroplast.

Lumen

The space enclosed by the thylakoid membrane within a chloroplast.

Proplastids

Small, undifferentiated plastids that can develop into chloroplasts, chromoplasts, or leucoplasts.

Cell Sap

The fluid that fills the central vacuole of a plant cell, containing dissolved substances.

Turgidity

The state of being swollen or rigid, typically due to high water content in plant cells, maintained by the central vacuole.

Glycosylation

The process of adding carbohydrate groups to proteins or lipids, often occurring in the Golgi apparatus.

Cytoskeleton

Elaborate network of filamentous proteinaceous structures in the cytoplasm providing mechanical support, motility, and shape maintenance.

Microtubules

Hollow rods about 25 nm in diameter, composed of the protein tubulin; involved in cell shape, movement, and spindle fiber formation during cell division.

Microfilaments

Solid rods about 6-7 nm in diameter, composed of the contractile protein actin; involved in muscle contraction and part of the cytoskeleton base.

Intermediate Filaments

Cytoskeletal filaments with a diameter of 8-12 nm, forming a basket-like structure around the nucleus for support.

Cilia

Short, hair-like outgrowths of the cell membrane that work like oars to move the cell or surrounding fluid.

Flagella

Long, hair-like outgrowths of the cell membrane responsible for cell movement. Eukaryotic flagella have a different structure than prokaryotic flagella.

Axoneme

The core of a cilium or flagellum, containing microtubules running parallel to its length.

9+2 Array

The typical arrangement of microtubules in an axoneme: nine doublets of peripheral microtubules and a pair of centrally located microtubules.

Dynein Arms

Enzymatic protein on the A tubules of peripheral doublets in cilia and flagella, with ATPase activity that provides energy for movement.Radial Spokes

Radial Spokes

Protein structures that connect the central sheath to one tubule of each peripheral doublet in cilia and flagella.

Basal Body

A centriole-like structure from which cilia and flagella emerge.

Centrosome

An organelle in animal cells usually containing two centrioles located at right angles to each other, surrounded by centrosphere.

Centrioles

Cylindrical structures found in the centrosome of animal cells, involved in the initiation of cell division and formation of spindle fibers (9+0 arrangement of triplet fibers).Centrosphere

Centrosphere

The cytoplasm that surrounds the centrioles in a centrosome.

Cartwheel Structure

The characteristic structure of a centriole in cross-section, made up of nine evenly spaced peripheral triplets of tubulin protein linked together, with a central hub and radial spokes.

Dictyosomes

Another name for the Golgi body or Golgi complex, especially referring to the individual stacks of cisternae in plants.

Vesicles

Small, oval, membrane-bound sacs that are one of the components of the endoplasmic reticulum.

Tubules

Irregular, often branched, membrane-bound tubes that are another component of the endoplasmic reticulum.

Luminal Compartment

The space inside the endoplasmic reticulum, enclosed by its membrane, where proteins are folded and modified.

Extra-luminal Compartment

The cytoplasmic space outside the endoplasmic reticulum.

Zone of Exclusion

The area of cytoplasm immediately surrounding the Golgi body that appears to have fewer or no other organelles.

Middle Man of the Cell

An informal term for the Golgi body, referring to its role in modifying, sorting, and packaging macromolecules for transport within or out of the cell.

Reverse Pinocytosis

The process by which vesicles from the Golgi body fuse with the plasma membrane and release their contents outside the cell; also known as exocytosis.

Pinocytosis

A type of endocytosis in which the cell engulfs extracellular fluid containing dissolved molecules; also known as "cell drinking."

Phagocytosis

The process by which a cell engulfs large particles or other cells.

Heterophagy

Intracellular digestion of foreign materials brought into the cell by phagocytosis, carried out by lysosomes.

Autolysis

The self-destruction of a cell by the release of its own lysosomal enzymes; also known as programmed cell death or "suicidal bag" activity.

Osteoclasts

Specialized cells that break down bone tissue, utilizing extracellular digestion via lysosomes.

Contractile Vacuole

A specialized vacuole in some protists, like Amoeba, that pumps excess water out of the cell, playing a role in excretion.

Perimitochondrial Space

The narrow, fluid-filled space between the inner and outer mitochondrial membranes.

Phosphorylation

The addition of a phosphate group to a molecule, particularly in the context of oxidative phosphorylation in the inner mitochondrial membrane to produce ATP.

Electron Transport System

A series of protein complexes embedded in the inner mitochondrial membrane that carry out redox reactions, ultimately leading to the generation of a proton gradient used to produce ATP.

Lycopene

A red pigment found in chromoplasts, responsible for the red color of tomatoes and chillies.

Anthocyanin

A water-soluble pigment found in the cell sap of plant cells, responsible for blue, violet, or red colors (depending on pH).

Anthochlor

A water-soluble pigment found in the cell sap of plant cells, responsible for yellow colors.

Ribonucleic Acid

A nucleic acid present in all living cells, acting as a messenger carrying instructions from DNA for controlling the synthesis of proteins (mRNA), as a structural component of ribosomes (rRNA), and as a regulator of gene expression (tRNA and other types).

Peptidyl Transferase Enzyme

An enzymatic activity residing in the large ribosomal subunit (specifically in the 23S rRNA of prokaryotes and the 28S rRNA of eukaryotes) that catalyzes the formation of peptide bonds during protein synthesis.

Actin

A contractile protein that is the main component of microfilaments in the cytoskeleton and is involved in muscle contraction.

Dynein

An enzymatic protein with ATPase activity found in the arms of the A tubules in the axoneme of cilia and flagella, responsible for their movement.