Cell Organelles to Review
What are polysomes?
They are small particles of nucleoproteins (rRNA and proteins) that are held together by a strand of mRNA to form polyribosomes. they exist as isolated clusters of free ribosomes within the cytoplasm or attached to the membrane of the ER.
What are microfilaments?
Thin, threadlike cytoplasmic structures. They are three classes of them.
What are organelles?
They are embedded in the cytoplasm which function as the organs of the cell. These organelles include the ribosomes, ER, Golgi complex, mitochondria, and lysosomes.
What are secondary lysosomes?
After they fuse with membrane-bound vacuoles that contain material to be digested. Lysosomes break down phagocytosis material by either Heterophagy or Autophagy.
What is primarily lysosomes?
Are membrane bound intracellular organelles that contain a variety of hydrologic enzymes that have not yet entered the digestive process. They received their enzymes as well as their membranes from the Golgi complex. They become secondary lysosomes.
What is jaundice?
Bilirubin is a normal major pigment of bile; it excess accumulation in cells is evidenced clinically by a yellowish discoloration of the skin and sclera.
What is the nucleus?
Centrally located organelle that is surrounded by a double layered membrane Nucleus pierced by pores that allow materials to enter and exit the nucleus. This organelle is where DNA in the form of chromosomes is stored. The nucleus also houses another organelle, the nucleolus. LC The nucleus also is the site for the synthesis of the three types of ribonucleic acid (messenger RNA or mRNA), ribosomal RNA or rRNA), and (transfer RNA or tRNA) that move to the cytoplasm and carry out the actual synthesis of proteins.
What are centrosomes?
In dividing cells, the two cylindrical centrioles are initially found in the vicinity of the Golgi apparatus in a region of the cell.
What is the inner membrane of mitochondria?
Inner membrane that forms shelflike projections called cristae. It contains the respiratory chain enzymes and transport proteins needed for the synthesis of ATP.
Give an example of what Golgi complex synthesizes?
Insulin, is synthesized as a large, inactive proinsulin molecule that is cut apart to produce a smaller, active insulin molecule within the Golgi complex of the beta cells in the pancreas.
What is autophagy?
Involves the segregation and disposal of damaged cellular organelles, such as mitochondria or ER, which the lysosomes must remove if the cell's normal function is to continue.
What is Smooth ER?
Is 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 intracelluar calcium, metabolism, detoxification of certain hormones, and drugs. It is the site of lipid, lipoprotein, and steroid hormone synthesis.
What is another function of Golgi complex?
It can receive proteins and other substances from the cell surface by a retrograde transport mechanism.
What is the mitochondria?
Powerhouse of the cell. These kidney shaped organelles contain a double layered membrane (bi-layer). The inner membrane contains folds called cristae that contain enzymes essential for ATP production (the electron transport chain proteins and the enzyme ATP synthase). The large space enclosed by the inner membrane is known as the matrix. The matrix holds the ribosomes and the mitochondrial DNA known as mtDNA. The matrix is also home to the Kreb's/ Citric acid cycle which generates energy (ATP) through oxidation. Mitochondria are key regulators in programmed cell death known as apoptosis. Mitochondria are literally the "power plants' 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.
What happens to the proteins that are produced by the rough ER?
Proteins produced by the rough ER are usually destined to become components of lysosomes of other organelles, incorporated into cell membranes, or leave the cell as a secretory protein.
What is heterophagy?
Refers to digestion of an exogenous subsistence phagoxyteosed form the cell's external environment.
What does the rRNA do?
Ribosomal, is the site of protein synthesis
What are ribosomes?
Ribosomes are the cellular organelles that carry out protein synthesis and they do this by translating (reading) mRNA (messenger RNA) and using that information to build a sequence of amino acids (a protein). They are found in both prokaryote and eukaryote cells. Ribosomes are divided into 2 subunits a smaller subunit which binds to mRNA and a larger subunit which binds to tRNA (transfer RNA) and amino acids. They are composed of rRNA (Ribosomal RNA) and polypeptide chains. There are two types of ribosomes: "bound" ribosomes are embedded in the RER and synthesize proteins to be inserted into the cell membrane or to be excreted from the cell; "free" ribosomes are loose in the cytoplasm and synthesize proteins to be used in the cytoplasm (e.g., intracellular enzymes for Metabolism).
What are Nucleoli?
Structures composed of regions from five different chromosomes, each with a part of genetic code needed for the synthesis of rRNA.
What is the endoplasmic reticulum?
It is an extensive system of paired membranes and flat vesicles that connect various parts of the inner cell. Between the paired ER membranes is a fluid-filled space called matrix.
What is cytoplasm?
It is part of the distinct regions of protoplasm. The cytoplasm is the liquid OUTSIDE of the nucleus. Although not contributing to the cell's function, pigments may also accumulate in the cytoplasm. Some pigments such as melanin (skin color) are normal constituents of the cell.
What are the key points of functional organization of the cell?
*The nucleus is the control center for the cell. It also contains most of the hereditary material. *The organelles, which are analogous to the organs of the body, are contained in the cytoplasm. They include the mitochondria, which supply the energy needs of the cell;the ribosomes, which synthesize proteins and other materials needed for cell function.
What are the 3 classes of microfilaments?
1. Thin microfilaments, which are equivalent to the thin actin filaments in muscle 2. Intermediate filaments, which are a heterogeneous group of filaments with diameter sizes between those of the thick and thin filaments. 3. Thick myosin filaments, which are present in muscle cells, but may also exists temporarily in other cells.
What are the two membranes of mitochondria composed of?
Outer and inner
What are centrioles?
Centrioles assist in the process of cell division during mitosis or meiosis. They are composed of nine triplets of microtubules arranged in cylinders. During cell division, two centrioles come together to form a centrosome. The microtubules attach to duplicated DNA's chromatids and provide the mechanism to organize chromosomes prior to cell division and allow for separating chromatids (half of a duplicated chromosome) so each newly formed daughter cell has an adequate amount of DNA.
What is the cytoskeleton?
Cytoskeleton is composed of a few different types of protein fiber/ fibrils one type of which are the microfilaments. The cytoskeleton serves a number of functions in the cell. It gives cells shape and keeps intracellular structures (e.g., organelles) anchored and in order. The cytoskeleton is responsible for changes in cell shape, for different forms of cell movement (both of intracellular components, gross cell movement - across surfaces, anchoring of flagella, etc.), as well as for added stability if bell-cell adhesion. Microtubules, Microfilaments, Intermediate filaments, and thick filaments. MOVEMENT OF THE CELL.
What is chromatin?
DNA molecules that are tightly coiled around proteins call histones. Or the term denoting the complex structure of DNA and DNA-associated proteins dispersed in the nuclear matrix.
What is the cell membrane?
Double layer of phospholipids. Phospholipids have polar heads that are "water loving" (hydrophilic) and nonpolar tails that are water hating (hydrophobic). The Cell/ Plasma non-polar hydrophobic tails are directed toward center of the membrane, and the membrane polar hydrophilic heads are directed toward either the ECF or cytoplasm. The plasma membrane serves many functions including: separating ICF from ECF, cell communication, cell recognition, cell adhesion in tissues, barrier and regulatory system for what can and cannot move from ICF to ECF or vice versa, functions as the outer boundary of cells, through which cells interacts with its external environment and many more. The cell membrane is consists of 45-50% of lipids, 45-50% of proteins, and 4-8% of carbohydrates (HS). An important component of cell membrane are the integral membrane proteins whose functions confer many of the overall functions of the membranes as listed above.
What is Rough ER?
It is studded with ribosomes on the side of the membrane that faces the cytoplasm, giving it the capacity to produce proteins.The rough endoplasmic reticulum (RER) is responsible for the synthesis and packaging of protein to be inserted in the cell membrane or to be excreted from the cell. It is called rough because it has ribosomes embedded in its membrane making it appear "lumpy" in microscope images. The ribosomes are the site of protein synthesis. The RER internal chamber is connected to the interior of the nucleus. DM
What is a lysosome?
Lysosomes are vesicle-like organelles that contain digestive enzymes. These enzymes aide in digesting food and can break down the cell when it dies. They also digest excess or worn out organelles, food particles, and engulfed viruses or bacteria. That's why these organelles are sometimes called "suicide sacs" because if the break or misbehave, the freed enzymes can being to digest the cells own structures leading to ell death. It can be viewed as the digestive system of the cell. These small, membrane-enclosed sacs contain powerful hydrologic enzymes. These enzymes can break down excess and worn-out cell parts as well as foreign substances that are taken into the cell. All of the lysosomal enzymes are acid hydro lasers, which mans they require an acidic environment. The lysosomes provide this environment by maintaining a pH of approximately 5 in their interior. The pH of the cytoplasm, which is approximately 7.2 serves to protect other cellular structures from this acidity.
What is cellular respiration?
Mitochondria contain the enzymes needed for capturing most of the Er by in foodstuffs and converting it into cellular energy. This multi step process is often referred to as cellular respiration because it requires oxygen.
What is the intermembrane space?
Narrow space between the outer and inner membranes.
What is the Golgi apparatus (complex)?
The Golgi complex is also known as the Golgi apparatus or the Golgi body. It is Golgi Complex found in most eukaryotic cells. It's main function is to package proteins into membrane-bound vesicles before they are transported through the cytoplasm to bin with the cell membrane and excreted from the cell by exocytosis. The Golgi is involved in lipid transport, lysosome formation, and can also create complex sugars that are stored in secretory vesicles. The Golgi complex is sometimes referred to as the "mail room" of the cell because it sorts proteins made in the RER, packages them into vesicles and inserts a "label" on the vesicle that tells the cell's transport mechanisms what proteins are inside and where they are supposed to go. Another important function of the Golgi complex is the formation of proteoglycans, the main component of the extracellular matrix or the substance between the cells. They help bind cations like: sodium, potassium, and calcium with water, and help molecules move easier through the matrix (KD).
What are microtubules?
The are formed from protein subunits called tubulin. They are long, diff, hollow, cylindrical structures. They are dynamic structures that can rapidly disassemble in one location and reassemble in another.
What is protoplasm/cytosol?
The cytosol is the liquid found in the cell - i.e., the ICF (intracellular fluid) - and is Cytosol/ Protoplasm 70% water. The amount of water in the cytsol determines the turgor pressure of a cell. It surrounds the organelles. Some of the processes that take place here are: Cell metabolism (e.g., Glycolysis); Signaling transduction pathways. Intracellular receptors and transcription factors are also found in the cytosol. Protoplasm is composed of water, proteins, lipids, carbohydrates, and electrolytes. Two distinct regions of protoplasm exist in the cell *The cytoplasm which lies outside the nucleus *The karyoplasm or nucleoplasm, which lies inside the nucleus.
What is a nuclear envelope?
The envelope is a double layered porous membrane that surrounds the nucleus Nuclear envelope It contains large nuclear pores that allow substances such a mRNA to move between the nucleoplasm inside of the nucleus and the cytosol. BC. It surrounds the nucleus formed by two (outer and inner) nuclear membranes containing a perinuclear cistern always space between them.
What is the matrix space?
The large space enclosed by the inner membrane is termed.
What is the matrix?
The matrix connects the space between the two membranes of the nuclear envelope, the cell membrane, and various cytoplasmic organelles. It functions as a tubular communication system for transporting various substances from one part of the cell to another.
What is nucleolus?
The nucleolus is located inside of the nucleus. Its major function is to produce the Nucleolus rRNA which is used to build ribosomes (located in the cytoplasm). CG. Nucleolus is the darkly stained round body in the nucleus. The processing of rRNA and its assembly into ribosomes occurs exclusively in the nucleolus.
Give an example of what the smooth ER does in the body?
The sarcoplasmic reticulum of skeletal and cardiac muscle cells is a form of smooth ER. Calcium ions needed for muscle contraction are stored and released from cisternae of sarcoplasmic reticulum. The smooth ER of the liver is involved in glycogen storage and metabolism of lipid-soluble drugs.
What are proteasomes?
Three major cellular mechanisms are involved in the breakdown of proteins or proteolysis. Proteasomes are basically enzyme complexes involved in degrading proteins, Proteasomes especially those involved in control of the cell cycle and programmed cell death (apoptosis). It is another cytoplasmic degradation mechanism that occurs within and organelle. Proteasomes are small organelles composed of protein complexes that are though to be present in both the cytoplasm and the nucleus. This organelle recognizes misformed and misfolded proteins that have been targeted by degradation, including transcription factors and the cycling that are important in controlling the cell cycle.
What does the tRNA do?
Transports amino acids to the site of protein synthesis for incorporation into the protein being synthesized.
What does mRNA do?
messenger, it copies and carries the DNA instructions for protein synthesis tot he cytoplasm.
What is mtDNA?
mitochondrial DNA. It is double-stranded, circular molecule that encodes the rRNA and tRNA required for intramitochondrial synthesis of the proteins needed for the energy-generating functions of the mitochondria.
What are peroxisomes?
oxidative organelles. Peroxisomes are membrane enclosed organelles nut differ from lysosomes in that they that contain many different enzymes primarily able to oxidize substrates such as fatty acids. This oxidative ability is in some respect similar to that of mitochondria, but peroxisomes do not contain their own genetic material like mitochondria do. They are smaller than lysosomes, spherical membrane-bound organelles contain a special enzyme that degrades peroxide's. Unlike lysosomes, perixomes are not formed by the Golgi complex. Peroxisome are self-replicating like mitochondria and are initially formed by proteins produced by free ribosomes. It's function is to control the free radicals unless degraded, these highly unstable chemical compounds would otherwise damage other cytoplasmic molecules. They also contain the enzymes needed for breaking down very-long-chain fatty acids, which mitochondrial enzymes ineffectively degrade. In liver cells, peroxisome enzymes are involved in the formation of the bile acids.
What are the two forms of ER?
smooth and rough
What is the outer membrane of mitochondria?
that encloses the periphery of the mitochondrion. It contains a large number of transmembrane poring, through which water-soluble molecules may pass. It is relatively permeable to small molecules.
What are free ribosomes?
they are involved in the synthesis of proteins, mainly enzymes that aid in the control of cell function, those attached to the ER translate mRNAs that code for proteins secreted from the cell or stored within the cell (eg granules in WBC).