A simple cell with no nucleus, or membrane-bound organelles; divides by binary fission and includes bacteria, both heterotrophic and autotrophic types.
Region of a prokaryotic cell that contains the genetic material.
Complex cell that contains a nucleus, which functions as the control center of the cell, directing DNA replication, transcription, and cell growth. Organisms can be unicellular or multicellular and contain many different membrane-bound organelles.
Eukaryotic structure in which ribosomes are constructed.
smooth endoplasmic reticulum (SER)
Membrane-bound organelle involved in lipid synthesis, detoxification, and carbohydrate metabolism; has no ribosomes on its cytoplasmic surface.
Organelle that modifies proteins, lipids, and other macromolecules by the addition of sugars and other molecules to form glycoproteins. The products are then sent to other parts of the cell.
Protein that has been modified by the addition of a sugar.
Diseases such as Tay-Sachs that are caused by the absence of a particular lysosome hydrolytic enzyme.
A fatal genetic storage disease that renders the body unable to break down a particular type of lipid.
The inner fluid portion of the chloroplast that plays host to the light-independent reactions of photosynthesis.
thylakoid membrane system
Inner membrane that winds through the stroma of a chloroplast. Site of the light-dependent reactions of photosynthesis.
Substances constructed from tubulin; play a lead role in the separation of cells during cell division; are also important components of cilia and flagella.
Substances built from actin that play a major role in muscle contraction.
Substances constructed from a class of proteins called keratins; function as reinforcement for the shape and position of organelles in a cell.
fluid mosaic model
Model that states that the membrane is made of a phospholipid bilayer with proteins of various lengths and sizes, interspersed with cholesterol.
Proteins that are implanted within the bilayer and can extend part way or all the way across the membrane.
Proteins, such as receptor proteins, not implanted in the bilayer, which are often attached to integral proteins of the membrane.
The movement of molecules down their concentration gradients without the use of energy. It is a passive process during which molecules move from a region of higher concentration to a region of lower concentration.
The passive diffusion of water down its concentration gradient across selectively permeable membranes. It will flow from a region with a lower solute concentration (hypotonic) to a region with a higher solute concentration (hypertonic).
The diffusion of particles across a selectively permeable membrane with the assistance of transport proteins that are specific in what they will carry and have a binding site designed for molecules of interest. This process requires no energy.
The movement of a particle across a selectively permeable membrane against its concentration gradient. This movement requires the input of energy, which is why it is termed "active" transport.
A mechanism that actively moves potassium into the cell and sodium out of the cell against their respective concentration gradients to maintain appropriate levels inside the cell.
Process by which substances are brought into cells by enclosure into a membrane-created vesicle that surrounds the substance and escorts it into the cell.
Immune cells (macrophages and neutrophils) that use endocytosis to engulf and eliminate foreign invaders.
Process by which substances are exported out of the cell. A vesicle escorts the substance to the plasma membrane, fuses with the membrane, and ejects its contents out of the cell.