Definitions: Cell theory,Cell membrane, prokaryote, eukaryote?

Cell theory:

Okay, most scientific theories have 2 components: The first describes a pattern in the natural world, while the second identifies a mechanism or process that is responsible for creating that pattern. The complete cell theory, then, can be stated as follows: All organisms are made of cells, and all cells come from preexisting cells.

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Cell membrane aka plasma membrane:

A membrane that surrounds a cell, separating it from the external environment and selectively regulating passage of molecules and ions into and out of the cell.

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Prokaryote:

It's a member of the domain Bacteria or Archea; a unicellular organism lacking a nucleus and containing relatively few organelles or cytoskeletal components.

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Eukaryote:

A member of the domain Eukarya; an organism whose cells contain a nucleus, numerous membrane-bound organelles, and an extensive cytoskeleton. It can be unicellular or multicellular.

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Microtubule:

A long, tubular fiber, about 25 nm in diameter, formed by polymerization of tubulin protein dimers; one of the three types of cytoskeletal fibers. It's involved in cell movement and transport of materials within the cell.

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Lysosome:

A small organelle in an animal cell containing acids and enzymes that catalyze hydrolysis reactions and can digest large molecules.

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Lipid bilayer aka phospholipid bilayer:

The basic structural element of all cellular membranes consisting of a two-layer sheet of phospholipid molecules whose hydrophobic tails are oriented toward the inside and hydrophilic heads, toward the outside.

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Endocytosis:

This is a general term for any pinching off the plasma membrane that results in the uptake of material from outside the cell. Includes, for example, phagocytosis, pinocytosis, etc.

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Exocytosis:

Secretion of intracellular molecules (e.g., hormones, collagen), contained within membrane-bounded vesicles, to the outside of the cell by fusion of vesicles to the plasma membrane.

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@Asker: It seems like your learning about cell structure and function. This is really interesting stuff. You should open your book, study and read! I do hope these definitions help you to understand the basics, but there's much more to it.

Send me an email if you need more help or clarification. ;)

Cell Membrane Theory

Cell Theory: ?

Cell Membrane: the outer (thin) layer of a cell in which it allows for particles to pass through needed by the cell

Prokaryote: a plant cell (has a cell wall and NO nuclear membrane)

Eukaryote: animal cell (has NO cell wall and has a membrane bound nucleus)

Microtubule: ?

Lysosome: cells janitors (gets rid of unneeded and unwanted materials)

Vacuole: water sac in the center of all plant cells

Lipid Bilayer: ?

Endocytosis: when materials enter the cell

Exocytosis: when materials exit the cell

Cell Theory:

1. All cells come from preexisting cells

2. cells are the basic unit of life

3. all organisms are made up of cells

Cell membrane:

The semipermeable membrane that encloses the cytoplasm of a cell

Prokaryote:

A cell without a nucleus (like bacteria)

Eukaryote:

A cell with a nucleus (like your own cells)

Microtubule:

They are part of the cell. They provide structural support and aid in cellular locomotion. (flagella are a type of microtubule that moves some cells around.)

Lysosome:

Its another organelle in the cell. It's enclosed in its own membrane (much like mitochondria) and it contains digestive enzymes. (its like the recycling plant of the cell)

Vacuole:

Another organelle. It also has its own membrane. Vacuoles can contain toxic waste, water, or food. (It's the storage unit of the cell.)

Lipid bilayer:

The semipermeable cell membrane is a lipid bilayer. It has two layers, and well, here's a picture:

http://www.cancerquest.org/images/New_Membrane.jpg

Here's more info on bilayers:

http://encyclopedia.thefreedictionary.com/Lipid+bi...

Endocytosis:

A process of cellular ingestion by which the plasma membrane folds inward to bring substances into the cell.

Exocytosis:

It's just the opposite of endocytosis. A process of cellular secretion or excretion in which substances contained in vesicles are discharged from the cell by fusion of the vesicular membrane with the outer cell membrane.

Cell theory: refers to the idea that cells are the basic unit of structure in every living thing.

Cell membrane: a selectively permeable lipid bilayer found in all cells.

Prokaryotes: a group of organisms that lack a cell nucleus or any other membrane-bound organelles.

Eukaryotes: organisms whose cells are organized into complex structures enclosed within membranes.

microtubule: one of the components of the cytoskeleton.

lysosomes: organelles that contain digestive enzymes (acid hydrolases).

vacuole: a membrane-bound organelle which is present in most eukaryotic cells.

lipid bilayer: a membrane made up from lipid molecules (usually phospholipids).

endocytosis: the process by which cells absorb material (molecules such as proteins) from outside the cell by engulfing it with their cell membrane.

exocytosis: the durable process by which a cell directs secretory vesicles out of the cell membrane.

1. cell theory 

–noun a basic tenet of modern biology, first stated by Matthias Schleiden and Theodor Schwann in 1838–39, that cells are the basic units of structure and function in living organisms

2. cell membrane 

–noun Biology. the semipermeable membrane enclosing the cytoplasm of a cell.

3.prokaryote–noun any cellular organism that has no nuclear membrane, no organelles in the cytoplasm except ribosomes, and has its genetic material in the form of single continuous strands forming coils or loops, characteristic of all organisms in the kingdom Monera, as the bacteria and blue-green algae.

4.eukaryote-noun Biology. any organism having as its fundamental structural unit a cell type that contains specialized organelles in the cytoplasm, a membrane-bound nucleus enclosing genetic material organized into chromosomes, and an elaborate system of division by mitosis or meiosis, characteristic of all life forms except bacteria, blue-green algae, and other primitive microorganisms.

5.microtubule-noun Cell Biology. a hollow cylindrical structure in the cytoplasm of most cells, involved in intracellular shape and transport.

6. lysosome–noun Cell Biology. a cell organelle containing enzymes that digest particles and that disintegrate the cell after its death.

7.vacuole–noun Biology. 1. a membrane-bound cavity within a cell, often containing a watery liquid or secretion.2. a minute cavity or vesicle in organic tissue.

8.lipid bilayer-noun the basic structure of a cell membrane consisting of a double layer of phospholipid molecules

9.endocytosis- A process of cellular ingestion by which the plasma membrane folds inward to bring substances into the cell.

10.exocytosis-A process of cellular secretion or excretion in which substances contained in vesicles are discharged from the cell by fusion of the vesicular membrane with the outer cell membrane.

Cell Theory- the basic tenet of modern biology, first stated by Matthias Schleiden and Theodor Schwann in 1838–39, that cells are the basic units of structure and function in living organisms.

Cell Theory2-a theory in biology that includes one or both of the statements that the cell is the fundamental structural and functional unitof living matter and that the organism is composed of autonomous cells with its properties being the sum of those of its cells

(Cell Theory 3-biology) the theory that cells form the fundamental structural and functional units of all living organisms; proposed in 1838 by Matthias Schleiden and by Theodor Schwann

CellMembrane- The semipermeable membrane enclosing the cytoplasm of a cell.

Cell Memebranea thin membrane (a double layer of lipids) enclosing the cytoplasm of a cell; proteins in the membrane control passage of ions (like sodium or potassium or calcium) in and out of the cell; "all cells have a cell membrane"

Prokaryote-any cellular organism that has no nuclear membrane, no organelles in the cytoplasm except ribosomes, and has its genetic material in the form of single continuous strands forming coils or loops, characteristic of all organisms in the kingdom Monera, as the bacteria and blue-green algae.

eukaryote- A single-celled or multicellular organism whose cells contain a distinct membrane-bound nucleus.

theese are the onlyy ones i could find, but try going to www.dictionary.com

Nuclear envelope: membrane that surrounds the nucleus and its lumen is continuous with that of the Rough Endoplasmic Reticulum. Cytoskeleton: The network of microfibrils and microtubules that provide shape for the cell. It is also involved in locomotion via cytoplasmic rolling. Microtubule: Made up of a homodimer called Tubulin. It is involved in various parts of the cell ranging from the Cytoskeleton to Mitosis. It is also the protein that Dyniens and Kenesins use to shuttle vesicles from place to place.

Cell theory********

Cell Theory refers to the idea that cells are the basic unit of structure in every living thing. Development of this theory during the Mid 1600s was made possible by advances in microscopy. This theory is one of the foundations of biology. The theory says that new cells are formed from other existing cells and the cell is a fundamental unit of structure, function and organization in all living organisms.

cell membrane********

The cell membrane (also called the plasma membrane, plasmalemma, or "phospholipid bilayer") is a selectively permeable lipid bilayer found in all cells.[1] It contains a wide variety of biological molecules, primarily proteins and lipids, which are involved in a vast array of cellular processes such as cell adhesion, ion channel conductance and cell signaling. The plasma membrane also serves as the attachment point for both the intracellular cytoskeleton and, if present, the extracellular cell wall.

prokaryote*******

The prokaryotes (pronounced /proʊˈkærioʊts/; singular prokaryote /proʊˈkæriət/) are a group of organisms that lack a cell nucleus (= karyon), or any other membrane-bound organelles. They differ from the eukaryotes, which have a cell nucleus. Most are unicellular, but a few prokaryotes such as myxobacteria have multicellular stages in their life cycles.[1] The word prokaryote comes from the Greek πρό- (pro-) "before" + καρυόν (karyon) "nut or kernel", referring to the cell nucleus, + suffix -ώτης (-ōtēs) (pl. -ώτες (-ōtes)). It is also spelled "procaryote".[2]

The prokaryotes are divided into two domains: the bacteria and the archaea. Archaea were recognized as a domain of life in 1990. These organisms were originally thought to live only in inhospitable conditions such as extremes of temperature, pH, and radiation but have since been found in all types of habitats.

eukaryote********

Animals, plants, fungi, and protists are eukaryotes (IPA: /juːˈkærɪɒt/ or IPA: /-oʊt/), organisms whose cells are organized into complex structures enclosed within membranes. The defining membrane-bound structure that differentiates eukaryotic cells from prokaryotic cells is the nucleus. The presence of a nucleus gives these organisms their name, which comes from the Greek ευ (eu), meaning "good/true," and κάρυον (karyon), "nut." Many eukaryotic cells contain other membrane-bound organelles such as mitochondria, chloroplasts and Golgi bodies.

Cell division in eukaryotes is different from organisms without a nucleus (prokaryotes). It involves separating the duplicated chromosomes, through movements directed by microtubules. There are two types of division processes. In mitosis, one cell divides to produce two genetically-identical cells. In meiosis, which is required in sexual reproduction, one diploid cell (having two instances of each chromosome, one from each parent) undergoes recombination of each pair of parental chromosomes, and then two stages of cell division, resulting in four haploid cells (gametes). Each gamete has just one complement of chromosomes, each a unique mix of the corresponding pair of parental chromosomes.

Eukaryotes appear to be monophyletic, and so make up one of the three domains of life. The two other domains, bacteria and archaea, are prokaryotes, and have none of the above features. But eukaryotes do share some aspects of their biochemistry with archaea, and so are grouped with archaea in the clade Neomura.

microtubule*******

Microtubules are one of the components of the cytoskeleton. They have a diameter of 25 nm and length varying from 200 nanometers to 25 micrometers. Microtubules serve as structural components within cells and are involved in many cellular processes including mitosis, cytokinesis, and vesicular transport.

lysosome****

Lysosomes are organelles that contain digestive enzymes (acid hydrolases). They digest excess or worn-out organelles, food particles, and engulfed viruses or bacteria. The membrane surrounding a lysosome allows the digestive enzymes to work at the 4.5 pH they require. Lysosomes fuse with vacuoles and dispense their enzymes into the vacuoles, digesting their contents. They are created by the addition of hydrolytic enzymes to early endosomes from the Golgi apparatus. The name lysosome derives from the Greek words lysis, which means dissolution or destruction, and soma, which means body. They are frequently nicknamed "suicide-bags" or "suicide-sacs" by cell biologists due to their role in autolysis. Lysosomes were discovered by the Belgian cytologist Christian de Duve in 1949.

The size of lysosomes varies from 0.1–1.2 μm.[1] At pH 4.8, the interior of the lysosomes is more acidic than the cytosol (pH 7.2). The lysosome's single membrane stabilizes the low pH by pumping in protons (H+) from the cytosol via proton pumps and chloride ion channels. The membrane also protects the cytosol, and therefore the rest of the cell, from the degradative enzymes within the lysosome. For this reason

lipid bilayer****

The foundational structure of plasma membranes; it is composed of two layers of phospholipids positioned such that their polar hydrophilic heads face outward and their nonpolar hydrophobic tails are directed inward, blocking entry of water and water-soluble material into the cell.

endocytosis********

A process of cellular ingestion by which the plasma membrane folds inward to bring substances into the cell.

exocytosis*****

A process of cellular secretion or excretion in which substances contained in vesicles are discharged from the cell by fusion of the vesicular membrane with the outer cell membrane.

man, we are learning these is science and it is not fun.how the heck am i supposed to know these, i dont remember, sorry.