Cell Biology: Rough Endoplasmic Reticulum

The primary function of the rER is to synthesize proteins, particularly those destined for secretion outside the cell (e.g., hormones and enzymes) or for incorporation into lysosomes and the cell membrane.

The rER membrane is continuous with the outer membrane of the nuclear envelope. This continuity allows for communication between the perinuclear space (between the nuclear membranes) and the lumen of the rER.

In actively synthesizing cells, the rER cisternae are dilated, indicating high protein production. Conversely, in weakly active cells, the cisternae are flattened and less prominent.

<p>Examples include pancreatic exocrine cells, fibroblasts, and plasma cells. Pancreatic cells synthesize digestive enzymes, fibroblasts produce extracellular matrix proteins, and plasma cells produce antibodies, all requiring extensive protein production and thus high rER abundance.</p> Signup and view all the answers

<p>Membrane proteins are synthesized in the rER and then transported in vesicles to the Golgi apparatus for further processing, including glycosylation. Once mature, they are packaged in secretory vesicles that bud off from the Golgi and fuse with the cell membrane, integrating the protein and lipids into the cell's outer layer.</p> Signup and view all the answers

<p>Ribosomal subunits are formed in the nucleus, where rRNA associates with proteins. These subunits then pass through nuclear pores into the cytoplasm, where they bind to mRNA and tRNA to facilitate protein synthesis. The small subunit decodes the genetic message, while the large subunit catalyzes peptide bond formation.</p> Signup and view all the answers

<p>The two main types are free ribosomes and membrane-bound ribosomes. Free ribosomes are located in the cytoplasm and synthesize proteins destined for the cytoplasm, while membrane-bound ribosomes are attached to the endoplasmic reticulum and produce proteins that will either be secreted from the cell or incorporated into cell membranes.</p> Signup and view all the answers

<p>Free polyribosomes are responsible for synthesizing proteins that remain within the cytoplasm of the cell. Hemoglobin, contractile proteins, and keratin are all found within the cytoplasm and are essential for various cellular functions, including oxygen transport, muscle contraction, and structural support, respectively.</p> Signup and view all the answers

<p>mRNA carries the genetic code from DNA to ribosomes, providing the instructions for building a specific protein. It contains a sequence of codons, each corresponding to a specific amino acid. Ribosomes read this sequence on mRNA and assemble the amino acids in the order dictated by the codons, ultimately forming the protein's primary structure.</p> Signup and view all the answers

<p>The RER is studded with ribosomes that synthesize proteins, many of which are destined for secretion. As these proteins are synthesized, they are translocated into the ER lumen, where they undergo folding and modifications, such as glycosylation, before being packaged into vesicles for transport to the Golgi apparatus and ultimately secretion outside the cell.</p> Signup and view all the answers

<p>Under a scanning electron microscope, ribosomes appear as small, spherical bodies. Their spherical shape distinguishes them from other cellular structures, such as elongated microtubules or flattened membrane sacs, which have different morphology.</p> Signup and view all the answers

<p>Ribosomes contain rRNA, which has a strong affinity for basic dyes. This property enables staining of ribosomes in light microscopy, allowing researchers to visualize them and distinguish them from other cellular components, enhancing the understanding of their distribution and activity within the cell.</p> Signup and view all the answers

<p>Free polyribosomes produce proteins that remain within the cytoplasm, such as hemoglobin for oxygen transport, contractile proteins for muscle contraction, and keratin for structural support. Membrane-bound polyribosomes synthesize proteins destined for secretion, like hormones and enzymes, or for incorporation into cellular membranes, such as lysosomal enzymes and membrane proteins.</p> Signup and view all the answers

<p>Primary lysosomes are organelles filled with hydrolase enzymes, formed by budding off vesicles from the trans-Golgi network.</p> Signup and view all the answers

<p>The silver impregnation technique, specifically Defano staining, is used to visualize the Golgi apparatus.</p> Signup and view all the answers

<p>Mitochondria are known as the energy centers of the cell, creating and storing energy in the form of adenosine triphosphate (ATP).</p> Signup and view all the answers

<p>The inner mitochondrial membrane has folds called cristae that increase its surface area significantly.</p> Signup and view all the answers

<p>Mitochondrial DNA is circular in shape, resembling bacterial DNA, indicating evolutionary similarities.</p> Signup and view all the answers

<p>ATP synthetases, or oxisomes, are multimeric protein complexes found on the surface of the inner mitochondrial membrane.</p> Signup and view all the answers

<p>The Krebs cycle is significant as it metabolizes glucose and fatty acids to produce ATP, essential for cellular functions.</p> Signup and view all the answers

<p>The mitochondrial matrix contains enzymes for the Krebs cycle and oxidative phosphorylation.</p> Signup and view all the answers

<p>Children inherit mitochondrial DNA only from their mother through the cytoplasm of the oocyte.</p> Signup and view all the answers

<p>Cardiolipin makes the inner mitochondrial membrane significantly impermeable to ions, preserving the electrochemical gradient.</p> Signup and view all the answers

<p>Mitochondria synthesize ATP from ADP by using the energy released when protons flow through the oxisome down the electrochemical gradient.</p> Signup and view all the answers

<p>During cell division, each daughter cell receives half of the number of mitochondria from the parent cell.</p> Signup and view all the answers

<p>Skeletal muscles are high-energy consumers, making them particularly sensitive to defects in mitochondrial function.</p> Signup and view all the answers

<p>Lysosomes are responsible for intracellular digestion, breaking down bacteria, viruses, and degenerated organelles.</p> Signup and view all the answers

<p>Clathrin is a crucial protein that plays a major role in the formation of enveloped vesicles.</p> Signup and view all the answers

<p>Peroxisomes primarily break down fatty acids and detoxify harmful substances, including hydrogen peroxide.</p> Signup and view all the answers

<p>Peroxisomes contain oxidative enzymes and catalases, while lysosomes primarily contain hydrolytic enzymes for breaking down macromolecules.</p> Signup and view all the answers

<p>The Periodic Acid-Schiff (PAS) staining method is used to visualize glycogen in hepatocytes.</p> Signup and view all the answers

<p>Both peroxisomes and mitochondria contain enzymes synthesized in free polyribosomes and have the ability to replicate by fission.</p> Signup and view all the answers

<p>Cellular inclusions can include glycogen, fat droplets, and pigments such as melanin.</p> Signup and view all the answers

<p>Primary lysosomes are the initial lysosomal structures that contain digestive enzymes, responsible for breaking down cellular waste and foreign material.</p> Signup and view all the answers

<p>Catalases in peroxisomes break down hydrogen peroxide into water and oxygen, preventing cellular damage.</p> Signup and view all the answers

<p>Peroxisomes typically range from 0.2 to 0.5 µm in diameter.</p> Signup and view all the answers

<p>Autophagia involves the digestion of the cell's own worn-out organelles, while heterophagia refers to the digestion of external substrates that enter the cell.</p> Signup and view all the answers

<p>Fat droplets in adipocytes are formed from the accumulation of triglycerides and cholesterol.</p> Signup and view all the answers

<p>Tertiary lysosomes, or residual bodies, contain undigested materials that remain after enzymatic degradation, indicating a completed digestion process.</p> Signup and view all the answers

<p>Lipofuscin is a pigment that accumulates in long-living cells such as neurons and cardiac muscle cells, indicating the presence of residual bodies and cellular aging.</p> Signup and view all the answers

<p>Electron microscopy reveals the high electron density of lysosomes, helping to distinguish between different types and functions during cellular digestion.</p> Signup and view all the answers

<p>In renal tubule cells, lysosomes digest small proteins absorbed through endocytosis, breaking them down to amino acids for reuse.</p> Signup and view all the answers

<p>Heterolysosomes are involved in the digestion of material that comes into the cell, performing the breakdown of various substrates.</p> Signup and view all the answers

<p>Lysosomes are typically found near Golgi cisternae, where they receive newly formed enzymes meant for digestion.</p> Signup and view all the answers

A type of endoplasmic reticulum that synthesizes proteins for secretion and those that remain in the cell.

The staining property of rER in cells, indicating high RNA content due to proteins being synthesized.

Cells like pancreatic exocrine cells that actively synthesize and secrete proteins.

The process of adding sugar chains to proteins in the Golgi apparatus, often for membrane proteins.

Membrane-bound carriers that transport proteins from the rER to the Golgi apparatus and then to the cell membrane.

The process of creating ribosomes in the nucleolus using rRNA and proteins.

Small and large components of ribosomes formed in the nucleus, essential for protein synthesis.

Individual ribosomes in the cytoplasm that synthesize proteins for use within the cell.

Clusters of ribosomes linked to mRNA, involved in translating the same mRNA into proteins.

Ribosomes attached to the endoplasmic reticulum that synthesize proteins for export or for use in the cell membrane.

Messenger RNA carries the genetic code from DNA to ribosomes for protein synthesis.

The stage in protein synthesis where mRNA is decoded by ribosomes to form polypeptide chains.

A network of membranes involved in synthesis and processing of biomolecules, including proteins.

Enzymes that catalyze the breakdown of compounds by hydrolysis.

Vesicles formed by budding from the trans-Golgi network, containing hydrolase enzymes.

Cell organelle that processes and packages proteins and lipids.

Organelles that produce ATP through metabolism of glucose and fatty acids.

A series of chemical reactions used by all aerobic organisms to generate energy.

Folds in the inner mitochondrial membrane that increase surface area.

Circular DNA found within mitochondria, distinct from nuclear DNA.

Enzymes located in the inner mitochondrial membrane that synthesize ATP.

Membrane organelles that contain oxidative enzymes for breaking down fatty acids and toxins.

Remove hydrogen peroxide, metabolize fatty acids, and protect cells from toxins.

Antioxidant enzymes found in peroxisomes that break down hydrogen peroxide into water and oxygen.

Deposits of cell products like glycogen, fat droplets, and pigments within the cytoplasm.

A polysaccharide stored in liver cells that is a key energy source in metabolism.

Periodic acid-Schiff staining is used to visualize glycogen in tissue samples.

Storage forms of triglycerides and cholesterol found within adipocytes.

Both peroxisomes and mitochondria can grow, replicate by fission, and contain synthesized enzymes.

Formed when primary lysosomes fuse with phagosomes for digestion.

Residual bodies that contain undigested materials.

The process where cells break down their own worn-out organelles.

Digestion of substances that enter the cell from the outside.

A pigment formed by accumulated residual bodies indicating aging.

Lysosomes appear as high electron density structures under TEM.

Cells that ingest small proteins via endocytosis and degrade them in lysosomes.

Mitochondrial DNA is inherited only from the mother.

Mitochondrial membranes are semi-permeable, allowing selective ion passage.

Protons flow down the electrochemical gradient, releasing energy for ATP synthesis.

During cell division, daughter cells receive half the number of mitochondria.

Defects in mitochondria can occur due to mutations in their DNA.

Lysosomes are membrane-bound vesicles containing hydrolytic enzymes for digestion.

Clathrin is a protein that aids in vesicle formation during endocytosis.