Anatomy Chapter 3: Cells

Inclusions

Chemical substances that may or may not be present, depending on cell type. Ex: granules of glycogen (liver and muscle) or pigments (melanin), lipid droplets (fat cells), vacuoles, and crystals

Ligands

Chemical that bind specifically to plasma membrane receptors. Includes most neurotransmitters, hormones, and paracrines.

Free ribosomes

Float freely in the cytoplasm. Make soluble proteins that function in the cytosol.

Inner membrane

Folds inward, forming shelflike cristae that protrude into the matrix; membrane of the mitochondria.

Membrane lipids

Forms the basic "fabric" of the membrane. Constructed largely of phospholipids, with smaller amounts of glycolipids, cholesterol, and areas called lipid rafts.

Plasma membrane

Functions: -Selective controls entry of nutrients and exit of products (semi-permeable) -Maintains ion concentrations -Cell-to-cell communication, adhesion, structural support

Lysosomes

Functions: "demolition crew", Digest ingested bacteria, viruses, and toxins, degrade non-functional organelles, break down and release glycogen, break down bone to release calcium, destroy cells in injured or non-useful tissue (autolysis)

Nucleus

Functions: Control center of the cell, responsible for transmitting genetic information, and provides the instructions for protein synthesis.

Centrosome

Functions: Generates microtubules, organizes mitotic spindle.

Peroxisomes

Functions: detoxify harmful substances using oxygen; then produce and degrade hydrogen peroxide into water and oxygen, neutralize dangerous free radicals, play role in energy metabolism by breaking down and synthesizing fatty acids.

Free radicals

Highly reactive chemicals with unpaired electrons that can scramble the structure of biological molecules.

Centrioles

Small, barrel-shaped organelles oriented at right angles to each other. Consists of a pinwheel array of nine triplets of microtubules. Also form the bases of cilia and flagella.

Plasma membrane

The flexible outer boundary of the cell.

Cristae

The gel-like substance within the mitochondrion.

Cytoplasm

The intracellular fluid packed with organelles, small structures that perform specific cell functions.

Organelles

The metabolic machinery of the cell. Each carries out a specific function for the cell.

Anucleate

Cells cannot reproduce and therefore live in the bloodstream for only 3 to 4 months before they deteriorate.

Basal bodies

Centrioles forming at the bases of cilia and flagella.

Organelles

Small structures that perform specific cell functions.

Centrosome

"Cell center" near nucleus. Granular matrix contains paired centrioles: small tube formed by microtubles.

Cytoplasm

"cell forming material" Located between plasma membrane and nucleus. The site of most cellular activities. Consists of the cytosol, organelles, and inclusions.

Microvilli

"little shaggy hairs" Fingerlike extensions of the plasma membrane. Project from an exposed cell surface. Increase surface area for absorption. Core of actin filaments for stiffening.

Glycocalyx

"sugar covering." Describes the fuzzy, sticky, carbohydrate-rich area at the cell surface. Provides specific biological markers so that cells can recognize each other. Enriched both by glycolipids and by glycoproteins secreted by the cell.

Generalized cell

All cells have the same basic parts and some common functions.

Endoplasmic reticulum

An extensive system of interconnected tubes and parallel membranes enclosing fluid-filled cavities, or cisterns.

Nucleus

An organelle that controls cellular activities; typically lies near the cell's center. "control center"

Desmosomes

Anchoring junctions bind adjacent cells together and help form an internal tension-reducing network of fibers. "rivets" or "spot-welds" that anchor cells together. Link cells together like velcro. Resist being pulled apart. Ex: skin, heart muscle (constantly beating)

Extracellular materials

Any substances contributing to body mass that are found outside the cells. Classes include: body fluids, cellular secretions, extracellular matrix.

Lipid rafts

Areas of saturated phospholipids and cholesterol. Stable rafts may be platforms for certain receptors. 20% of outer membrane surface.

Membrane bound ribosomes

Attached to membranes, forming a complex called the rough endoplasmic reticulum. Synthesize proteins to be incorporated into membranes, lysosomes, or exported from the cell.

Nucleosome

Consist of flattened disc-shaped cores or clusters of 8 histone proteins connected like beads on a string by a DNA molecule.

Golgi apparatus

Consists of stacked and flattened membranous sacs, shaped like hollow dinner plates, associated with swarms of tiny membranous vesicles. The principle "traffic director" for cellular proteins.

Nucleoli

Dark-staining spherical bodies within nucleus. Involved in rRNA synthesis and ribosome subunit assembly. Not membrane bounded. Larger in growing cells making tissue protein. "little nuclei"

Plasma membrane

Defines the extent of a cell. Separates the intracellular fluid within the cells and the extracellular fluid outside cells. Bimoloceular layer of lipids and proteins in a constantly changing fluid mosaic.

Nuclear Envelope

Double-membrane (selectively permeable) barrier separated by fluid-filled space. Outer layer is continuous with the rough ER and studded with ribosomes. Inner lining (nuclear lamina) maintains shape of nucleus and acts as a scaffold to organize DNA in the nucleus.

Microtubules

Dynamic hollow tubes made of spherical protein subunits called tubulins. Most radiate from the centrosome (cell center). Determines the overall shape of the cell and distribution of organelles. Mitochondria, lysosomes are positioned in cell by motor proteins.

Cholesterol

Increases membrane stability and decreases fluidity. Wedges itself between phospholipid tails. Has a polar and nonpolar region. 20% of total membrane lipids.

Nuclear pores

Intricate complex of proteins. Lines each pooe, forming an aqueous transport channel and regulating entry and exit of molecules and large particles into and out of the nucleus. Nuclear envelope is punctuated by these.

Nucleus

Largest single organized cell component. Largest organelle in a cell. Houses DNA which directs protein synthesis and serves as a genetic blueprint for cells. Surrounded by the nuclear membrane. Contains fluid nucleoplasm, nucleoli, and chromatin.

Phospholipids

Lipid bilayer. Phosphate heads are polar and hydrophillic. Fatty acid tails are nonpolar and hydrophobic. Mostly composed of unsaturated fats. 75% of total membrane lipids.

Glycolipids

Lipids with attached polar sugar groups found only on the outer plasma membrane surface. 5% of total membrane lipids.

Golgi apparatus

Major functions: modify, concentrate, and package the proteins and lipids made at the rough ER and destined for export from the cell; tags for delivery.

Mitochondria

Major site of ATP synthesis via cellular respiration. Threadlike or lozenge-shaped membranous organelles. Powerhouse of the cell. Contains own DNA, RNA, and ribosomes. Are able to reproduce themselves. Double membrane structure with shelf-like cristae.

Multinucleate

Many nuclei. Ex: skeletal, muscle cells, bone destruction cells, and some liver cells.

uni

Most cells are ___nucleate

Fluid mosaic model

Phospholipid bilayer with proteins "plugged into" it.

Apoptosis

Programmed cell death.

Integral proteins

Proteins firmly inserted into the lipid bilayer. Most are transmembrane proteins that span the entire membrane and protrude on both sides. May be transport proteins (channels and carriers), enzymes, or receptors for hormones.

Peripheral proteins

Proteins loosely attached to integral proteins (not embedded in the lipid bilayer) Include filaments on intracellular surface and glycoproteins on extracellular surface. Functions: enzymes, motor proteins, cell-to-cell links, provide support of intracellular surface, and form part of glycocalyx.

Anucleate

Red blood cells are ____.

Rough ER

Ribosomes that attach to membranes, forming a complex in the external surface. (External surface studded with ribosomes) Manufactures all secreted proteins (hormones, enzymes), abundant in secretory cells, antibody producing cells, and liver cells. Cell's "membrane factory" where integral proteins and phospholipids that form parts of all cellular membranes are manufactured.

Tight junctions

Series of integral protein molecules in the plasma membrane of adjacent cells fuse together, forming an impermeable junction that encircles the cell. Prevents fluids and most molecules from moving between cells. "6 pack of pop" Ex: stomach, intestinal tract Keeps digestive enzymes and microorganisms in the intestine from seeping into the bloodstream.

Ribosomes

Small, dark-staining granules composed of proteins and a variety of rRNA. Each has two globular subunits that fit together like the body and cap of an acorn. Sites of protein synthesis. Some attached to rough ER and others are scattered freely in the cytoplasm.

Outer membrane

Smooth and featureless membrane of the mitochondria

Flagella

Sperm. (tail) Propels the cell itself. Formed by the centrioles. Substantially longer than cilia.

Lysosomes

Spherical membranous organelles containing activated digestive enzymes. Large and abundant in phagocytes. Can digest almost all kinds of biological molecules and work best in acidic conditions "acid hydrolases"

Peroxisomes

Spherical membranous sacs containing a variety of powerful enzymes, the most important of which are oxidases and catalases. Especially numerous in liver and kidney cells. Form by buddying off of the ER.

Endomembrane System

System with an overall function of producing, storing, and exporting biological molecules along with degrading potentially harmful substances.

Cell

The basic structural and functional unit of living organisms.

Cytoskeleton

The cell's skeleton. Made up of rods running through the cytosol to hold the structure of the cell (microtubules, microfilaments, intermediate filaments). Aids in cellular movement. Fibers absorb water and crosslink to each other. Gives the cytoplasm the consistency of gelatin.

Autolysis

The process by which the cell digests itself when lysosomes rupture. It is the basis for desirable destruction of cells.

Cytosol

The viscous, semitransparent fluid in which the other cytoplasmic elements are suspended. (intracellular fluid) Dissolved in it, which is largely water, high concentrations of solutes (dissolved nutrients, proteins, and waste) and potassium ions.

Chromatin

Threadlike strands composed of DNA (30%), histone proteins (60%), and RNA (10%). Arranged in fundamental units called nucleosomes. Condense into bar-like bodies called chromosomes when the cell starts to divide.

Membrane junctions

Three factors bind cells together: -Adhesive factor of glycocalyx -Tongue-and-groove contours of membrane -Special cell junctions form

Intermediate filaments

Tough, insoluble rope-like protein fibers made up of twisted subunits called twisted tetramer fibrils. Most stable and permanent filaments with high tensile strength. Resists pulling forces on the cell and attach to desmosomes.

Gap junctions

Transmembrane proteins form pores that allow small molecules to pass from cell to cell. Communicating junctions allow ions and small molecules to pass from one cell to the next for intercellular communication. Allow communication between cells and transmit ions and electrical activity.

Smooth ER

Tubules arranged in a looping network. Its enzymes play no role in protein synthesis (lack ribosomes), instead enzymes catalyze reactions. Metabolizes, synthesizes, detoxify, and break down.

Microfilaments

Very thin. Semiflexible strands of spherical protein subunits called actin strands make up a terminal web which attaches to the walls of the plasma membrane. Involved in cell mobility, change in shape, endocytosis, and exocytosis.

Ribosomes, Rough ER, golgi apparatus

What are the three organelles involved in protein synthesis

Cilia

Whiplike, motile cellular extensions on the exposed surface of some cells. Contains microtubules and motor molecules. Moves substances in one direction across cell surfaces. Formed by centrioles.