Peroxisomes are small organelles that contain oxidases to oxidize organic substances, including amino acids, fatty acids, and toxic substances like alcohol.
A flagellum generates forward motion along its axis by rapidly wiggling in a wavelike pattern.
Ribosomes are the sites of protein synthesis.
Microfilaments are composed of the proteins actin and myosin. They help generate movement and provide mechanical support, being involved in muscle contraction, cell division, cell locomotion, and anchoring the cytoskeleton to integral proteins in the plasma membrane.
Symporters move two substances in the same direction across the membrane, while antiporters move two substances in opposite directions.
Diffusion
Active process in which a cell expends energy to move a substance across the membrane against its concentration gradient by transmembrane proteins that function as carriers.
Nicotine in cigarette smoke paralyzes the movement of cilia.
Intermediate filaments are cytoskeletal components that are thicker than microfilaments but thinner than microtubules. They are exceptionally strong and found in parts of cells subject to mechanical stress, helping to stabilize the position of organelles like the nucleus and attach cells to one another.
The cytosol is the fluid portion of the cytoplasm that surrounds organelles. It contains water, ions, glucose, amino acids, fatty acids, proteins, lipids, ATP, and waste products.
About 40% of the ATP generated by a typical body cell is expended on primary active transport.
Smoking paralyzes the cilia in the uterine tubes, which impairs the movement of oocytes toward the uterus.
An autophagosome is a vesicle derived from the ER that fuses with a lysosome to recycle cytoplasmic contents.
The three types of protein filaments that make up the cytoskeleton are microfilaments, intermediate filaments, and microtubules.
The cytoskeleton is a network of protein filaments that provides structural support for the cell and its organelles.
The most prevalent primary active transport mechanism expels sodium ions (Na+) from cells and brings potassium ions (K+) in, known as the sodium–potassium pump.
The binding of three Na+ ions in the cytosol to the pump protein triggers the hydrolysis of ATP into ADP and a phosphate group.
Active process in which a substance moves across the membrane against its concentration gradient by pumps (carriers) that use energy supplied by hydrolysis of ATP.
Movement of substances into a cell in vesicles.
Cilia help sweep foreign particles trapped in mucus away from the lungs.
The balance between endocytosis and exocytosis keeps the surface area of a cell’s plasma membrane relatively constant.
Nonpolar, hydrophobic solutes such as oxygen, carbon dioxide, nitrogen gases, fatty acids, steroids, and fat-soluble vitamins; polar molecules such as water, urea, and small alcohols.
The binding of two K+ ions on the outside surface of the pump and the release of the phosphate group cause the pump to return to its original shape, moving the K+ ions into the cell.
It forms the mitotic spindle.
Pseudopods are projections of the plasma membrane and cytoplasm that surround and engulf particles during phagocytosis.
Microvilli are nonmotile, microscopic fingerlike projections of the plasma membrane that greatly increase the surface area of the cell, making them abundant on cells involved in absorption, such as the epithelial cells lining the small intestine.
Autophagy is the process by which a lysosome engulfs and digests a worn-out organelle, recycling its components back into the cytosol.
The two general functions of microfilaments are to help generate movement and provide mechanical support.
Las subunidades de los ribosomas se sintetizan y ensamblan en el nucleolo.
Both endocytosis and exocytosis involve vesicular transport. Endocytosis brings materials into the cell, while exocytosis releases materials from the cell.
Sodium–potassium pumps maintain a low concentration of Na+ in the cytosol by pumping these ions into the extracellular fluid against the Na+ concentration gradient, and move K+ into cells against the K+ concentration gradient.
Passive movement of a substance down its concentration gradient through the lipid bilayer by transmembrane proteins that function as channels or carriers.
Los ribosomas asociados con el retículo endoplásmico sintetizan proteínas destinadas a orgánulos específicos, para inserción en la membrana plasmática o para exportación fuera de la célula.
The two sources of cellular energy used to drive active transport are energy obtained from hydrolysis of ATP (primary active transport) and energy stored in an ionic concentration gradient (secondary active transport).
“Cell drinking”; movement of extracellular fluid into a cell by infolding of plasma membrane to form a vesicle.
Movement of substances out of a cell in secretory vesicles that fuse with the plasma membrane and release their contents into the extracellular fluid.
Vesicles transport a variety of substances from one structure to another within cells.
Lysosomal enzymes released from the head of a sperm cell dissolve the protective coating of the oocyte in a process called the acrosomal reaction.
En las células del hígado, el retículo endoplásmico liso ayuda a liberar glucosa en el torrente sanguíneo y a inactivar o desintoxicar drogas liposolubles o sustancias potencialmente dañinas.
The three general destinations are: transport vesicles to lysosomes, secretory vesicles for exocytosis, and membrane vesicles that merge with the plasma membrane.
Exocytosis is the process of releasing materials from a cell. It is important for secretory cells that release digestive enzymes, hormones, mucus, and neurotransmitters, as well as for the removal of cellular waste.
Passive movement of water molecules across a selectively permeable membrane from an area of higher to lower water concentration until equilibrium is reached.
Coupled active transport of two substances across the membrane using energy supplied by a Na+ or H+ concentration gradient maintained by primary active transport pumps.
They move specific enzymes back toward the entry face and some partially modified proteins toward the exit face.
A highly selective type of endocytosis by which cells take up specific ligands that bind to receptor proteins in the plasma membrane.
The invaginated edges of the membrane around the clathrin-coated pit fuse, and a small piece of the membrane pinches off to form a clathrin-coated vesicle.
The energy from ATP hydrolysis causes the pump protein to change shape, moving the Na+ ions to the outside of the cell.
Antiporters move Na+ (or H+) and another substance in opposite directions across the membrane; symporters move Na+ (or H+) and another substance in the same direction across the membrane.
They are surrounded by a piece of the ER membrane, forming transport vesicles that move toward the entry face of the Golgi complex.
Microtubules are the dominant components of cilia and flagella.
Receptors accumulate in elongated protrusions of the endosome, pinch off to form transport vesicles, and return to the plasma membrane.
Autolysis is the destruction of a cell by its own lysosomal enzymes, occurring in some pathological conditions and after death.
El retículo endoplásmico rugoso produce proteínas secretoras, proteínas de membrana y muchas proteínas de orgánulos.
<p>The smooth endoplasmic reticulum does not have ribosomes on the outer surface of its membrane.</p>
<p>The smooth endoplasmic reticulum synthesizes fatty acids and steroids, such as estrogens and testosterone.</p>
Transcytosis is an active process where vesicles undergo endocytosis on one side of a cell, move across the cell, and then undergo exocytosis on the opposite side. It commonly occurs across the endothelial cells that line blood vessels.
Simple diffusion
Polar or charged solutes such as glucose, fructose, galactose, some vitamins, and ions like K+, Cl−, Na+, and Ca2+.
The only example of a flagellum in the human body is a sperm cell’s tail.
The key difference is that passive processes do not require cellular energy, while active processes do.
Carbohydrates are added to proteins to form glycoproteins, and lipids are added to proteins to form lipoproteins.
Ligand–receptor complexes trigger infolding of a clathrin-coated pit that forms a vesicle containing ligands.
One pair of microtubules in the center is surrounded by nine clusters of two fused microtubules (doublets).
Smooth ER detoxifies certain drugs. Repeated drug use, such as with phenobarbital, increases the amount of smooth ER and its enzymes in liver cells, leading to increased drug tolerance. This means higher doses are needed to achieve the same effect, increasing the risk of overdose and dependence.
The sodium-potassium pump helps maintain normal cell volume by ensuring that cells neither shrink nor swell due to the movement of water by osmosis.
Cholesterol-containing low-density lipoproteins (LDLs), transferrin, some vitamins, antibodies, and certain hormones.
The phagosome fuses with lysosomes, and lysosomal enzymes break down the ingested material.
A cilium or flagellum contains a core of microtubules with one pair in the center surrounded by nine clusters of doublet microtubules.
Lysosomes maintain their acidic interior (pH 5) through active transport pumps that import hydrogen ions (H+).
Another name for the sodium–potassium pump is Na+–K+ ATPase because a part of the pump acts as an ATPase, an enzyme that hydrolyzes ATP.
They are further modified, sorted, and packaged.
Organelles perform specific functions in cellular growth, maintenance, and reproduction.
The centrosome consists of a pair of centrioles and the pericentriolar matrix.
The uncoated vesicle fuses with an endosome, where LDL particles separate from their receptors.
Digitalis slows the action of the sodium-potassium pumps, leading to an accumulation of Na+ inside heart muscle cells, which decreases the Na+ concentration gradient and slows down the Na+-Ca2+ antiporters. This results in more Ca2+ remaining inside heart muscle cells, increasing the force of their contractions and strengthening the heartbeat.
<p>Free ribosomes synthesize proteins that are used in the cytosol.</p>
The two components of cytoplasm are the cytosol and organelles.
Primary active transport is a process where energy derived from the hydrolysis of ATP changes the shape of a carrier protein, which pumps a substance across a plasma membrane against its concentration gradient.
Insulin.
“Cell eating”; movement of a solid particle into a cell after pseudopods engulf it to form a phagosome.
Microtubules help in the movement of chromosomes during cell division.
The cell would likely have a reduced capacity for cell division.
The entry (cis) face of the Golgi complex is a cistern that faces the rough ER and is convex in shape, while the exit (trans) face is a cistern that faces the plasma membrane and is concave in shape. The cisterns between these faces are called medial cisterns.
The clathrin-coated vesicle loses its clathrin coat to become an uncoated vesicle, and clathrin molecules return to the inner surface of the plasma membrane or help form coats on other vesicles.
Rough ER synthesizes glycoproteins and phospholipids that are transferred into cellular organelles, inserted into the plasma membrane, or secreted during exocytosis.
Lysosomes contain digestive enzymes that break down large protein and lipid molecules from LDL particles.
The sources of cellular energy for active transport are ATP and the energy stored in ionic concentration gradients.
They are stored in secretory vesicles, which deliver the proteins to the plasma membrane for exocytosis.
They deliver contents to the plasma membrane for incorporation, adding new segments and modifying the number and distribution of membrane molecules.
Transport vesicles containing LDL particles bud off the endosome and fuse with a lysosome, where digestive enzymes break down the LDL particles.
Na+-Ca2+ antiporters eject calcium ions to maintain low Ca2+ concentration in the cytosol, while Na+-H+ antiporters expel excess H+ to help regulate the cytosol’s pH.
Phagocytes, including macrophages and neutrophils, are capable of carrying out phagocytosis.
Active transport is a process where energy is required for carrier proteins to move solutes across the plasma membrane against a concentration gradient.
Na+, K+, Ca2+, H+, I−, Cl−, and other ions.
They are the organizing centers for the growth of the mitotic spindle and microtubule formation in nondividing cells.
Clathrin attaches to the membrane on its cytoplasmic side, forming a basketlike structure around receptor–ligand complexes, causing the membrane to invaginate.
Smooth ER synthesizes fatty acids and steroids, detoxifies drugs and other harmful substances, removes the phosphate group from glucose-6-phosphate, and stores and releases calcium ions that trigger muscle contraction.
Bulk-phase endocytosis or pinocytosis is a form of endocytosis where tiny droplets of extracellular fluid are taken up without the involvement of receptor proteins.
They release proteins into the lumen of the Golgi complex.
Movement of a substance through a cell as a result of endocytosis on one side and exocytosis on the opposite side.
Symporters move two substances in the same direction across the membrane, while antiporters move two substances in opposite directions.
Phagocytosis is a form of endocytosis where the cell engulfs large solid particles like worn-out cells, bacteria, or viruses.
The vesicle fuses with a lysosome, where enzymes degrade the engulfed solutes, and the resulting smaller molecules are used elsewhere in the cell.
They differ in size, shape, content, and enzymatic activities.
Modifies, sorts, packages, and transports proteins from the rough ER; forms secretory vesicles for exocytosis; forms membrane vesicles for the plasma membrane; forms transport vesicles for other organelles.
Secondary active transport uses the energy stored in a Na+ or H+ concentration gradient to drive other substances across the membrane against their concentration gradients. This process indirectly uses energy obtained from the hydrolysis of ATP.
HIV attaches to the CD4 receptor on helper T cells and enters via receptor-mediated endocytosis.
Receptor-mediated endocytosis, phagocytosis, and bulk-phase endocytosis.
The Golgi complex is an organelle consisting of 3 to 20 cisterns, which are small, flattened membranous sacs with bulging edges. Its primary function is to modify, sort, and package proteins synthesized by ribosomes attached to the rough ER for transport to other regions of the cell.
Different enzymes in the entry, medial, and exit cisterns of the Golgi complex allow each area to modify, sort, and package proteins for transport to their final destinations.
Pus is a mixture of dead neutrophils, macrophages, tissue cells, and fluid in an infected wound.
Phagocytosis helps protect the body from disease by disposing of invading microbes and aged, worn-out cells.
