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58 Cards in this Set

  • Front
  • Back

Cell

Smallest structural and functional living unit

Plasma Membrane

Flexible outer boundary of cell; Biomolecular layer of phospholipids, some cholesterol, and variously positioned proteins in a constantly changing fluid mosaic; Plays dynamic role in cellular activity; Separates intracelluar fluid (ICF) from extracellular fluid (ECF)

Cytoplasm

Intracellular fluid containing organelles

Nuclues

Control center of cell

Interstitial Fluid (IF)

Extracellular fluid that surrounds cells

Phospholipids (Cytoplasm)

Most abundant lipid; Phosphate heads are polar and hydrophilic; Fatty acid tails are nonpolar and hydrophobic

Glycolipids (Cytoplasm)

Lipids with polar sugar groups on outer membrane surface

Cholesterol (Cytoplasm)

Increases membrane stability and fluidity

Integral Proteins (Cytoplasm)

Firmly inserted into the membrane (transmembrane)

Peripheral Proteins (Cytoplasm)

Include filaments on intracellular surface and glycoproteins on extracellular surface

Functions of Membrane Proteins

Transport; Receptors for signal transduction; Attachment to cytoskeleton and extracellular matrix; Enzymatic activity; Intercellular joining; Cell to cell recognition

Membrane Junctions

Tight Junction, Desmosomes, Gap Junction

Tight Junction

Impermeable junction prevents molecules from passing through the intercellular space

Desmosomes

Anchoring junctions bind adjacent cells together and help form an internal tension-reducing network of fibers

Gap Junctions

Communicating junctions allow ions and small molecules to pass from one cell to the next for intercellular communication

Membrane Transport Permeability

Plasma membranes are selectively permeable (some molecules easily pass through membrane, others do not)

Membrane Transport: Passive Processes

No cellular energy (ATP) required; Substance moves down concentration gradient; Lipid solubility of substance, appropriately sized channels, and carrier proteins determine whether or not a substance can passively permeate a membrane

Passive Processes: Simple Diffusion

Nonpolar lipid-soluble (hydrophobic) substances diffuse directly through phospholipid bilayer

Passive Processes: Facilitated Diffusion

Certain lipophobic molecules (glucose, amino acids, ions, etc.) use carrier proteins or channel proteins that exhibit specificity, are saturable, and can be regulated in terms of activity/quantity

Carrier Protein Process

Transmembrane integral proteins transport specific polar molecules (sugars and amino acids) and the binding of the agent causes carrier shape change

Channel Protein Process

Aqueous channels formed by transmembrane proteins selectively transport ions or water; Leakage channels are always open; Gated channels are controlled by chemical/electrical signals

Passive Processes: Osmosis

Movement of solvent (water) across selectively permeable membrane; Concentration gradient based on presence of solute, low solute concentration means high water concentration; Water diffuses through plasma membranes through lipid bilayer (nominal) and aquaporins (AQPs)

Membrane Transport: Active Processes

Energy (ATP) required; Substance moves against concentration gradient; Occurs only in living cell membranes; Requires carrier proteins that serve as pumps

Primary Active Transport

Energy from hydrolysis of ATP causes shape change in transport protein so bound solutes (ions) are "pumped" across membrane

Sodium-Potassium Pump (Na+ -K+ ATPase)

Located in all plasma membranes; Involved in primary and secondary active transport; Maintains electrochemical gradients essential for functions of muscle and nerve tissue

Sodium Potassium Pump Process

Cytoplasmic Na+ binds to pump protein; Binding Na+ promotes phosphorylation of protein by ATP; Phosphorylation causes protein shape change, which expels Na+ to the outside; Extracellular K+ binds to pump; K+ binding triggers phosphate release, pump returns to original config.; K+ is released from pump and Na+ sites are ready to bind Na+ again.

Phagocytosis

Pseudopods engulf solids and bring them into cell interior (Macrophages and some white blood cells); Combines with lysosome; Undigested contents remain in vesicle (now a residual body) or are ejected by exocytosis

Fluid-Phase Endocytosis (Pinocytosis)

Plasma membrane infolds, bringing extracellular fluid and solutes into cell interior; Nutrient absorption in small intestine

Exocytosis

Bulk release of substance that is controlled (hormone secretion, neurotransmitter release, mucus secretion, waste ejection, etc.)

Exocytosis Process

Membrane bound vesicle migrates to plasma membrane; Proteins at vesicle surface (v-SNAREs) bind with plasma membrane proteins (t-SNAREs); Vesicle and plasma membrane fuse and a pore opens up; Vesicle contents are released to cell exterior

Membrane Potential

Separation of oppositely charged particles (ions) across a membrane l (potential energy measured as voltage)

Resting Membrane Potential (RMP)

Voltage measured in resting state in all cells; Ranges from –50 to –100 mV in different cells; Results from outward diffusion (mainly K+)

RMP Generation/Maintenance

Na+ -K+ pump continuously ejects Na+ from cell and carries K+ back in; Some K+ continually diffuses down it concentration gradient out of cell through leakage channels; Membrane interior becomes negative (relative to exterior) because of large anions trapped inside cell; Electrochemical gradient begins to attract K+ back into cell; RMP is established at point where the electrical gradient balances the K+ concentration gradient; Steady state it maintained because the rate of active transport is equal to and depends on the rate of Na+diffusion into cell

Cytoplasm

Located between plasma membrane and nucleus

Cytosol

Water with solutes (proteins, salts, sugars, etc._

Cytoplasmic Organelles

Metabolic machinery of cell

Inclusions

Granules of glycogen or pigments, lipid droplets, vacuoles, and crystals

Mitochondria

Double membrane structure with shelf-like crystae; Provide most of cell's ATP via aerobic cellular respiration; Contain own DNA and RNA

Ribosomes

Granules containing protein and RNA; Site of protein synthesis; Free ribosomes synthesize soluble proteins; Membrane-bound ribosomes (on rough ER) synthesize proteins to be incorporated into membranes or exported from the cell

Endoplasmic Reticulum

Interconnected tubes and parallel membranes

Rough ER

external surface has ribosomes; Manufactures secreted proteins and synthesizes membrane integral proteins and phospholipids

Smooth ER

In liver - lipid and cholesterol metabolism, breakdown of glycogen, detoxification of drugs, pesticides, carcinogens; In intestinal cells - absorption, synthesis, and transport of fats; In skeletal and cardiac muscle - storage and release of calcium

Golgi Apparatus

Stacked and flattened membranous sacs; Modifies, concentrates, and packages proteins and lipids; Transport vessels from ER fuse with convex cis face of GA; Proteins then pass through GA to trans face; Secretory vesicles leave trans face of GA stack and move to designated parts of cell

Lysosomes

Spherical membranous bags containing digestive enzymes (acid hydrolases); Digest ingested bacteria, viruses, toxins; Degrade nonfunctional organelles; Break down and release glycogen; Break down bone to release Ca2+; Destroy cells in injured or non-useful tissue (autolysis)

Cytoskeleton

Elaborate series of rods through cytosol

Microtubules (tubulin)

Dynamic hollow tubes that determine overall shape of cell and distribution of organelles

Microfilaments (actin)

Dynamic strands involved in cell motility, change in shape, endocytosis and exocytosis

Intermediate filaments (variety of proteins)

Tough insoluble rope-like protein fibers that resist pulling forces on the cell and attach to desmosomes

Motor Molecules

Protein complexes that function in motility (movement of organelles and contraction); powered by ATP; Facilitate movement of vesicles and organelles along cytoskeleton

Cilia and Flagella

Motile extensions on surfaces of certain cells; Contain microtubules and motor molecules; Cilia moves substances across cell surfaces; Longer flagella propel whole cells (eg. tail of sperm)

Microvilli

Fingerlike extensions of plasma membrane; Increase surface area for absorption; Core of actin filaments for stiffening

Nucleus

Genetic library with blueprints for nearly all cellular proteins; Responds to signals and dictates protein synthesis; Most cells are uninucleate; Red blood cells are anucleate; Skeletal muscle cells, bone destruction cells, and some liver cells are multinucleate

Cell Cycle

Defines changes from formation of the cell until it reproduces; Includes Interphase and Cell Division (Mitotic Phase)

Interphase

Period from cell formation to cell division; Nuclear material called chromatin; Four subphases

G1 (Gap 1)

Vigorous growth and metabolism

G0

Gap phase in cells that permanently cease dividing

S (Synthetic)

DNA Replication

G2 (Gap 2)

Preparation for cell division