Cellular Level of Organization Flashcards
Cell
Smallest living unit in the body
Plasma membrane
Selectively permeable membrane that controls: Entry of ions and nutrients, elimination of wastes, release of secretions
Extracellular fluid
Watery medium surrounding cells; called interstitial fluid in most tissues
Glycocalyx (carbohydrate shell)
Superficial membrane carbohydrates
Proteoglycans
Carbohydrates with protein attached
Glycoproteins
Protein with carbohydrates attached
Glycolipids
Lipids with carbohydrates attached
Integral proteins
Part of cell membrane; cannot be removed without damaging cell; often span entire cell membrane; can transport water or solutes
Peripheral proteins
Attached to cell membrane surface; removable; fewer than integral proteins
Phospholipid bilayer
Mostly comprised of phospholipid molecules in two layers: hydrophilic heads at membrane surface, hydrophobic tails on the inside; isolates cytoplasm from extracellular fluid; cholesterol important for membrane fluidity
Plasma membrane functions
Physical isolation, regulation of exchange with external environment, sensitivity to environment, structural support
Anchoring proteins
Attach the plasma membrane to other structures and stabilize its position; inside the cell, membrane proteins are bound to the cytoskeleton
Recognition proteins
Detected by cells of the immune system; enzymes in plasma membranes may be integral or peripheral proteins
Receptor proteins
Bind to specific extracellular molecules called ligands
Ligand
Anything from a small ion like calcium, to a relatively large complex hormone
Carrier proteins
Bind solutes and transport them across the plasma membrane
Channels
Integral proteins containing a central pore (channel) that forms a passageway completely across the plasma membrane; the channel permits the passage of water and small solutes that cannot otherwise cross the lipid layers of the plasma membrane
Cytoplasm
Material between cell membrane and nuclear membrane; Colloid containing many proteins
Cytosol
Intracellular fluid
Organelles
Intracellular structures with specific functions
Cytoskeleton
Cellular framework components
Microfilaments
<6 nm in diameter; typically composed of actin; commonly at periphery of cell
Terminal web
Inside plasma membrane of cells forming a layer or lining
Intermediate filaments
7-11 nm in diameter; strongest and most durable cytoskeletal elements
Microtubules
~25 nm in diameter; largest components of cytoskeleton; extend outward from centrosome (near nucleus)
Cantrioles
Cylindrical structures; composed of microtubules (9 groups of triplets); two in each centrosome; control movement of DNA strands during cell division ( cells without centrioles cannot divide: red blood cells, skeletal muscle cells)
Cilia
Long, slender plasma membrane extensions; common in respiratory and reproductive tracts; also composed of microtubules: nine groups of two surrounding a central pair; anchored to cell surface with basal body; beat rhythmically to move fluids or secretions across cell
Ribosomes
Protein synthesis; two subunits (1 large, 1 small) containing special proteins and ribosomal RNA (rRNA): must join before synthesis begins; fixed ribosomes-attached to the endoplasmic reticulum; free ribosomes: throughout cytoplasm, manufactured proteins enter cytosol
Smooth endoplasmic reticulum
Lacks ribosomes; tubular cisternae
Rough endoplasmic reticulum
Has attached (fixed) ribosomes; modification of newly synthesized proteins; export to golgi apparatus
Functions of the smooth endoplasmic reticulum
Synthesis of the phospholipids and cholesterol needed for maintenance and growth of the plasma membrane, ER, nuclear envelope, and golgi apparatus; synthesis of steroid hormones, such as androgens and estrogens (the dominant sex hormones in males and females, respectively) in the reproductive organs; synthesis and storage of glycerides, especially triglycerides, in liver cells and fat cells; synthesis and storage of glycogen in skeletal muscle cells and liver cells
Golgi apparatus
Functions: renews or modifies plasma membrane, modifies or packages secretions for release from cell (exocytosis), packages special enzymes within vesicles for use in cytosol; typically consist of 5-6 flattened discs (cisternae); may be more than one in a cell; situated near nucleus
Membrane renewal vesicles
Add to plasma membrane
Secretory vesicles
Contain products to be discharged from the cell; fuse with plasma membrane and release contents into extracellular environment
Enzymes for cytosol
Contained within lysosomes: isolate damaging chemical reactions
Lysosomes
Isolated intracellular location for toxic chemicals involved in breakdown and recycling of large organic molecules
Lysosome functions
May fuse with another organelle to activate digestive enzymes; may fuse with another vesicle containing fluid or solid extracellular materials; may break down with cell injury or death causing autolysis (enzymes destroy cytoplasm)
Mitochondria
Produce energy (ATP) for cells through the breakdown of carbohydrates (glucose); vary widely in shape and number: red blood cells have none, cardiac muscle cells are 30% mitochondria by volume
Nucleus
Usually largest cellular structure; control center for cellular operations: can direct synthesis of >100,000 different proteins, coded in sequence of nucleotides, determines cells structure/function; usually only one per cell