Protoplasm
The living part of the cell. Composed of water, proteins, carbohydrates and electrolytes.
Cytoplasm
Part of the protoplasm that lies outside of the nucleus. Mostly water in which inorganic and organic chemicals are dissolved.
Nucleoplasm
Part of the protoplasm that lies inside the nucleus.
Cytosol
Fluid suspension in the cytoplasm. It contains membrane-enclosed compartments or organelles that perform distinctive functions. Also, contains a system of tubules and filaments.
Cytoskeleton
System of tubules and filaments that maintains the shapes of cells and their ability to move.
Plasma Membrane or Cell Membrane
This is one of the most important parts of the cell. Acts as a semipermeable structure that separates the intracellular and extracellular environments. It controls the transport of materials from the extracellular fluids to the interior of the cell, provi
Lipid Bilayer
Main structural component of the membrane. A bimolecular layer that consists primarily of phospholipids, with glycolipids and cholesterol.
Hydrophilic
Water-soluble
Hydrophobic
Water-insoluble
Integral Proteins
Span the entire lipid bilayer and are essentially part of the membrane. Most of the integral proteins pass directly through the membrane. May also be referred to as transmembrane proteins.
Peripheral Proteins
Bound to one or the other side of the membrane and do not pass into the lipid bilayer.
Glycocalyx or Cell Coat
A fuzzy-looking layer that surrounds the cell surface. Consists of long, complex carbohydrate chains attached to protein molecules that penetrate the outside portion of the membrane. It participates in cell-to-cell recognition and adhesion.
Nucleus
Rounded or elongated structure situated near the center of the cell. It is enclosed in a nuclear envelope and contains chromatin (genetic material). Nucleus can be regarded as the control center for the cell. Contains DNA.
Chromatin
Complex structure of DNA and DNA-associated proteins that disperse in the nuclear matrix.
Ribosomes
Small particles of nucleoproteins (rRNA and proteins) that are held together by a strand of mRNA to form polyribosomes. Free ribosomes are involved in protein synthesis.
Endoplasmic Reticulum (ER)
Extensive system of paired membranes and flat vesicles that connect various parts of the inner cell. Two forms: Rough ER and Smooth ER
Rough ER
Segregates proteins from other components of the cytoplasm and modifies their structure for specific functions.
Smooth ER
Free of ribosomes and is continuous with the rough ER. It does not participate in protein synthesis; instead, its enzymes are involved in the synthesis of lipid molecules, regulation of intracellular calcium, and metabolism and detoxification of certain h
Golgi Apparatus (aka Golgi Complex)
Consists of stacks of thin, flattened vesicles or sacs. Golgi bodies are found near the nucleus and function in association with the ER. Substances produced in the ER are carried to the Golgi complex in small, membrane-covered transport vesicles. The Golg
Lysosomes
Can be viewed as the digestive organelles of the cell. They are small, membrane-enclosed sacs filled with hydrolytic enzymes. They contain acid hydrolases which help to break down all kinds of biomolecules, including proteins, nucleic acids, carbohydrates
Peroxisomes
Smaller than lysosomes, spherical membrane-bound organelles. They contain a special enzyme that degrades peroxides (e.g. hydrogen peroxide). They function to control free radicals. Also contain the enzymes needed for breaking down very long chains of fatt
Proteasomes
Small compartmentalized protein complexes that are responsible for proteolysis of malformed and misfolded proteins.
Mitochondria
Considered the "power house" of the cell because they transform organic compounds into energy that is easily accessible to the cell. They do not make energy, but extract it from organic compounds. It contains enzymes needed for capturing most of the energ
Cytoskeleton
Controls cell shape and movement.
Microtubules
Slender tubular structures composed of globular proteins called tubulin. Dynamic structures that can rapidly disassemble in one location and reassemble in another. Function in development and maintenance of cell form; participation in intracellular transp
Microfilaments
Thin, threadlike cytoplasmic structures. Three classes of microfilaments: thin microfilaments, thick myosin filaments and intermediate filaments.
Energy Metabolism
Refers to the chemical processes involved in converting carbohydrates, fats and proteins from the foods we eat into the energy needed for cell functions. Cells use oxygen to transform the breakdown products of the foods we eat into energy needed for muscl
ATP
Special carrier for chemical energy in all living things. Consists of adenosine, a nitrogenous base; ribose, a five-carbon sugar; and three phosphate groups.
Glycolysis
Occurs in the cytoplasm of the cell. Involves the splitting of the glucose molecule into two molecules of pyruvic acid. There is a net gain of only two molecules of ATP from each glucose. This process in anaerobic and does not require oxygen or produce CO
Citric Acid Cycle (Krebs Cycle)
Under aerobic conditions, both of the pyruvic acid molecules formed by the glycolytic pathway enter the mitochondria, where each combines with acetyl coenzyme to form acetyl-coenzyme A (acetyl-CoA). The formation of acetyl-CoA begins the reactions that oc
Protein Kinases
Enzymes that catalyze the phosphorylation of amino acids in the protein structure.
G-Protein-Linked Receptors
Mediate cellular responses for numerous types of first messengers, including proteins, small peptides, amino acids, and fatty acid derivatives such as the prostaglandins. G-Protein-Linked Receptors are the largest family of cell surface receptors.
Enzyme-Linked Receptors
Transmembrane proteins with their ligand-binding site on the outer surface of the cell membrane. Cytosolic domain either has intrinsic enzyme activity or associates directly with an enzyme. Several classes of enzyme-linked receptors, including one widely
Ion Channel-Linked Receptors
Involved in the rapid synaptic signaling between electrically excitable cells. Many neurotransmitters mediate this type of signaling by transiently opening or closing ion channels formed by integral proteins in the cell membrane. This type of signaling is
Channel Proteins
Have watery spaces all the way through the membrane and allow free movement of water as well as selected ions or molecules.
Membrane Transport Proteins
Bind with molecules or ions and undergo a series of conformational changes to transfer the bound solute across the membrane.
Passive Transport
All channels and many transporters allow solutes to cross the membrane and does not require an input of energy.
Active Transport
Directional and requires an energy source such as ATP.
Endocytosis or Exocytosis
Cell membrane can also engulf substances, forming a membrane-coated vesicle. This vesicle is moved into the cell.
Diffusion
Net movement of a substance from an area of high concentration to an area of low concentration.
Simple Diffusion
Kinetic movement of molecules or ions occurs through a membrane opening or through intermolecular spaces without any interaction with a carrier protein.
Facilitated Diffusion
Occurs down a concentration gradient; it does not require input of metabolic energy. Requires a transport protein.
Leakage Channels
Open even in the unstimulated state.
Gated Channels
Open and close in response to specific stimuli.
Voltage-Gated Channels
Electrically operated channels that open when the membrane potential changes beyond a certain point.
Ligand-Gated Channels
Chemically operated and respond to specific receptor-bound ligands, such as the neurotransmitter acetylcholine.
Mechanically Gated Channels
Open or close in response to such mechanical stimulations as vibrations, tissue stretching, or pressure.
Primary Active Transport
Substances transported by primary active transport are sodium, potassium, calcium, and hydrogen ions.
Secondary Active Transport
Harness the energy derived from the primary active transport of one substance, usually sodium, for the cotransport of a second substance.
Membrane Potentials
Electrical potentials exist across the membranes of most cells in the body. Because these potentials occur at the level of the cell they are called membrane potentials.
2 Main Factors that Alter Membrane Potential
1. The difference in the concentration of ions on the inside and outside of the membrane.
2. Permeability of the membrane to these ions.
Diffusion Potential
Describes the voltage generated by ions that diffuse across the cell membrane.
Equilibrium Potential
No net movement of a particular ion across a membrane because the diffusion potential and electrical focus generated by the movement of the ion are exactly balanced.
Nernst Potential
Magnitude of the equilibrium potential. Determined by the ratio of the concentration of a specific ion on the two sides of the membrane.
Resting Membrane Potential
Represents the period of time when excitable cells, such as nerve fibers, are not transmitting signals.
Tissues
Groups of cells that are closely associated in structure and have common or similar functions.
Cell Differentiation
Formation of different types of cells and the disposition of these cells into tissue types.
Epithelial Tissue
Forms sheets that cover the body's outer surface, line the internal surfaces, and form glandular tissue.
Basement Membrane
Underneath all types of epithelial tissue is an amorphous extracellular layer.
3 General Characteristics of Cells that Make up Epithelium
1. They are characterized by three distinct surfaces: a free surface or apical surface, a lateral surface, and a basal surface.
2. They are closely apposed and joined by cell-to-cell adhesion molecules, which form specialized cell junctions.
3. Their basa
Squamous
Thin and Flat
Cuboidal
Cube Shaped
Columnar
Resembling a column
Simple Epithelium
Single layer of cells, all of which rest on the basement membrane. It is adapted for filtration; it is found lining the blood vessels, lymph nodes, and alveoli of the lungs.
Endothelium
Single layer of squamous epithelium lining the heart and blood vessels.
Mesothelium
Forms the serous membranes that line the pleural, pericardial and peritoneal cavities and covers the organs of these cavities.
Simple Cuboidal Epithelium
Found on the surface of the ovary and in the thyroid.
Simple Columnar Epithelium
Lines the intestines
Stratified Epithelium
Contains more than one layer of cells, with only the deepest layer resting in the basement membrane. it is designed to protect the body surface.
Stratified Squamous Keratinized Epithelium
Makes up the epidermis of the skin. Made up of many layers.
Stratified Squamous Nonkeratinized Epithelium
Found on moist surfaces like the mouth and tongue.
Pseudostratified Epithelium
Type of epithelium in which all of the cells are in contact with the underlying intracellular matrix.
Transitional Epithelium
Stratified epithelium characterized by cells that can change shape and become thinner when the tissue is stretched. Well adapted for lining of organs that are constantly changing their volume, such as the urinary bladder.
Glandular Epithelial Tissue
Formed by cells specialized to produce a fluid secretin. Usually accompanied by the intracellular synthesis of macromolecules. Glandular Epithelial can synthesize, store, and secrete proteins.
Epithelial Cell Renewal
Cells making up the epithelial tissues generally exhibit a high rate of turnover, which is related to their location and function. Rate of cell turnover is characteristic of specific epithelium.
Connective or Supportive Tissue
Most abundant tissue in the body. It connects and binds or supports the various tissues. It is unique in that its cells produce the extracellular matrix that supports and holds tissues together.
Loose Connective Tissue
Also known as areolar tissue. It is soft and pliable. It fills spaces between muscle sheaths, forms a layer that encases blood and lymphatic vessels, and provides support for epithelial tissues and the means by which these tissues are nourished. It is cha
Adipose Tissue
Special form of connective tissue in which adipocytes predominate. These cells store large quantities of triglycerides and are the largest repository of energy in the body. It helps to fill spaces between tissues and helps to keep organs in place.
Reticular and Dense Connective Tissue
Characterized by network of fibers interspersed with macrophages and fibroblasts that synthesize collagen fibers.
Reticular Fibers
Provide the framework for capillaries, nerves, and muscle cells. They also constitute the main supporting elements for the blood-forming tissues and the liver.
Osmosis
Diffusion of water molecules.
Receptor Proteins
Cause the cell to respond by:
- Opening ion channels to let ions in or out.
-Causing a second molecule to be released inside the cell.
-Turning on enzymes inside the cell.
-Stimulating the transcription of genes in the nucleus.
Threshold Potential
More Na+ channels open, Na+ rushes in, making the cell very positive, causing depolarization.
Depolarization
When the cell becomes very positive.
Repolarization
When the cell becomes negative again.