Chap 4 PT 4 Flashcards
(ER) Endoplasmic Reticulum
Extensive interconnected membrane network
Extends from nuclear envelope outward
Varies in shape, but one continuous lumen (“lumen”=internal tubing)
Composes about 50% of membrane within cell!
With ribosomes—rough ER
Without ribosomes—smooth ER
Rough ER 1:
Ribosomes produce proteins
Rough ER (2)
Proteins transported out in enclosed membrane sacs
(Transport vesicles)
Smooth ER
metabolic processes vary by cell
Synthesis, transport, and storage of lipids
Carbohydrate metabolism
Ion storage
Detoxification of drugs and poisons
Abundant in
Liver, testes
Golgi Apparatus
Composed of cisternae, elongated saclike membranous structures Modification, packaging, and sorting of proteins
Formation of secretory vesicles
Some vesicles become part of plasma membrane
Others release contents outside cell (secretions)
Lysosomes
Small, membranous sacs formed by Golgi
Contain digestive enzymes
For removal of unneeded substances
For digesting contents of endocytosed vesicles (phagocytosis
Peroxisomes
Membrane-enclosed sacs, smaller than lysosomes, formed from rough ER
Role in chemical digestion
Beta oxidation
Lipid synthesis
Endomembrane System
Extensive array of membrane-bound structures
Includes Smooth and Rough ER, Golgi apparatus, vesicles, lysosomes, peroxisomes
Includes plasma membrane and nuclear envelope
Connected directly or through vesicles moving between them
Provides means of producing and transporting substances within cells
Mitochondria
Oblong organelles with double membrane
Aerobic cellular respiration
Complete digestion of fuel molecules to synthesize ATP
“Powerhouses” of cell
Ribosomes produce proteins
Protein and RNA arranged into large and small subunit
Made within nucleolus and assembled in cytoplasm
Bound ribosomes
attached to outside of Rough ER
synthesize proteins for export, to become part of plasma membrane, or serve as enzymes in lysosomes
Free ribosomes
suspended within cytosol
All other proteins within cell synthesized here
Cytoskeleton
Plays roles in
Intracellular support
Organization of organelles
Cell division
Movement of materials
Extends throughout interior of cell
Includes microfilaments, intermediate filaments, microtubules
Microfilaments
Smallest components of cytoskeleton
Form interlacing network on cytoplasmic side of membrane to
Help maintain cell shape
Form internal support of cell membrane and extensions called microvilli
Separate two cells during cytokinesis
Microtubules
Largest components of cytoskeleton
May be elongated or shortened as needed
Maintain cell shape
Organize and move organelles
Form components of cilia and flagella
Participate in transport of vesicles (endocytosis, exocytosis)
Move and separate chromosomes during cell division
Intermediate filaments
Intermediate-sized components of cytoskeleton
More rigid than microfilaments
Support cells structurally, Stabilize cell junctions
Centrosome
Pair of centrioles
Surrounded by protein
Primary function: organizes microtubules within cytoskeleton
Functions in cellular division
Proteasomes
Protein-digesting organelles
Proteins that are damaged, misfolded, or no-longer-needed are marked with ubiquitin tag for disposal
Cilia
Contain both microtubule proteins and cytoplasm
Enclosed in plasma membrane
Usually found on exposed surfaces of specific cells
Beating moves fluid across cell surface, creates current
Flagella
Similar to cilia in structure, but longer
Propels cell. In humans, only example is sperm cell
Microvilli
Microscopic extensions of plasma membrane. (Absorption)
Smaller than cilia
More densely packed, lack powered movement
Supported by microfilaments
Tight junctions
Prevent substances from passing between cells
Requires materials to move through, rather than between cells
Desmosomes
Provides integrity to cells exposed to stress
Mechanical reinforcement
E.g., external layer of skin
Gap junctions
Form tiny, fluid-filled tunnels between cells
direct passageway for substances to travel between cells
E.g., flow of ions between cells in cardiac muscle
