Cell Active Organelles (3c)

What is the cytoplasm and what are its three components?

Cytoplasm is all cellular material between the plasma membrane and nucleus. It contains cytosol, inclusions, and organelles.

What are cytosol, inclusions, and organelles?

Cytosol = gel-like solution of water and soluble molecules such as proteins, salts, and sugars. Inclusions = insoluble materials that vary by cell type, such as glycogen granules, pigments, lipid droplets, vacuoles, and crystals. Organelles = specialized structures that perform the cell's metabolic functions.

What are the membranous vs. nonmembranous organelles?

Membranous = mitochondria, endoplasmic reticulum (ER), Golgi apparatus, peroxisomes, and lysosomes. Nonmembranous = ribosomes, cytoskeleton, and centrioles.

Why are membranes around organelles important?

They allow compartmentalization, separating different cellular activities into specialized areas that are crucial for cell function.

What is the main function and structure of mitochondria?

Mitochondria are the cell's "power plants" because they produce most ATP through aerobic (oxygen-requiring) cellular respiration. They have an outer and inner membrane, and the inner membrane folds into cristae.

What are cristae?

Folds of the inner mitochondrial membrane containing membrane proteins involved in cellular respiration.

What makes mitochondria unusual compared with many other organelles?

They contain their own DNA, RNA, and ribosomes. They resemble bacteria and can divide by fission, the same type of division used by bacteria.

What are ribosomes and what are they made of?

Ribosomes are nonmembranous organelles that are the site of protein synthesis. They are made of protein and ribosomal RNA (rRNA).

What is the difference between free and membrane-bound ribosomes?

Free ribosomes float in the cell and make soluble proteins that function in the cytosol or other organelles. Membrane-bound ribosomes attach to the ER and make proteins that will enter membranes or lysosomes or be exported from the cell.

What is the endoplasmic reticulum (ER)?

A series of parallel, interconnected cisterns, which are flattened membranous tubes containing fluid-filled interiors. The ER is continuous with the outer nuclear membrane and has two types: rough ER and smooth ER. (think og the cisterns as rooms that the proteins are edited in)

Why does rough ER look rough and what does it make?

Its external surface is covered with ribosomes. It synthesizes proteins that will be secreted from the cell, many plasma membrane proteins, and phospholipids.

What happens to a protein in the rough ER?

As it is synthesized, the protein enters the cisterns and is modified while moving through them. The final protein is enclosed in a vesicle and sent to the Golgi apparatus for further processing. (think that it enters, makes it ways to cisterns to be edited, then before leaving its shipped in a new dress)

What is smooth ER and what are its major functions?

Smooth ER is a network of looped tubules continuous with rough ER. Its functions include lipid metabolism; cholesterol and steroid hormone synthesis; making lipids for lipoproteins; absorption, synthesis, and transport of fats; detoxification of drugs and pesticides; converting glycogen to free glucose; and storing and releasing calcium.

What is the sarcoplasmic reticulum?

A specialized form of smooth ER found in skeletal and cardiac muscle cells. (SarCoplasMic)

What is the Golgi apparatus and what is its main job?

The Golgi is made of stacked, flattened membranous cistern sacs. It modifies, concentrates, sorts, tags, and packages proteins and lipids received from the rough ER.

What are the three basic steps of Golgi processing?

1) Transport vesicles from the ER fuse with the cis (inner) face. 2) Proteins and lipids are modified, tagged, sorted, and packaged. 3) New transport vesicles pinch off the trans (outer) face and are directed to their destinations.

What is the difference between the cis and trans faces of the Golgi?

The cis (inner) face RECEIVES transport vesicles from the ER. The trans (outer) face SHIPS newly packaged vesicles to their destinations.

What are the three possible pathways for products leaving the Golgi?

A: Secretory vesicles fuse with the plasma membrane and release proteins by exocytosis. B: Vesicles containing lipids or transmembrane proteins fuse with the plasma membrane or an organelle membrane and insert their contents. C: Lysosomes containing digestive enzymes remain inside the cell until needed.

What is the overall pathway of a protein that will be secreted from a cell?

Ribosome on rough ER → protein enters and is modified in rough ER → transport vesicle → cis face of Golgi → modification/sorting/packaging → trans face → secretory vesicle → plasma membrane → exocytosis.

What are peroxisomes and what do they do?

Membranous sacs containing powerful detoxifying substances. They neutralize toxins and free radicals and also help break down and synthesize fatty acids.

How do oxidase and catalase work together in peroxisomes?

Oxidase uses oxygen to convert toxins into hydrogen peroxide (H₂O₂), which is itself toxic. Catalase then converts H₂O₂ into harmless water.

(olly thinks hes helping by combining toxins with 02, catalase fixes it by convering the hydroden peroxide back into regular water)

What are free radicals?

Toxic, highly reactive molecules produced naturally as by-products of cellular metabolism that can damage the cell if they are not detoxified.

What are lysosomes?

Spherical membranous bags containing digestive enzymes called acid hydrolases. They provide a "safe" site for intracellular digestion by isolating potentially harmful digestive enzymes from the rest of the cell.

(lindsey has bags of acid hydrolase, keeps it serpate from harming her things)

What are the major functions of lysosomes?

They digest ingested bacteria, viruses, and toxins; degrade nonfunctional organelles; break down and release glycogen; and help break down and release Ca²⁺ from bone.

What is autolysis?

Self-digestion of a cell caused by intracellular release of lysosomal enzymes when a cell is injured.

What are lysosomal storage diseases, and what is Tay-Sachs disease?

Lysosomal storage diseases occur when lysosomal digestive enzymes are mutated and do not function properly. In Tay-Sachs, a lysosomal enzyme needed to break down glycolipids in brain cells is missing, so glycolipids accumulate and interfere with nervous system function.

What is the endomembrane system and what does it do?

It includes the ER, Golgi apparatus, secretory vesicles, lysosomes, nuclear membrane, and plasma membrane. Together they produce, degrade, store, and export biological molecules and degrade potentially harmful substances.

What is the cytoskeleton and what are its three components?

A network of protein rods throughout the cytosol that acts like the cell's "bones, ligaments, and muscle," providing structure and helping move cell components. Its three components are microfilaments, intermediate filaments, and microtubules.

What are microfilaments?

The thinnest cytoskeletal elements. They are semiflexible strands made of the protein actin and are involved in cell shape, cell movement, endocytosis, and exocytosis.

What is the terminal web of microfilaments?

A dense, cross-linked network of microfilaments attached to the cytoplasmic side of the plasma membrane. It strengthens the cell surface and helps resist compression.

What are intermediate filaments and what do they do?

Tough, insoluble, ropelike protein fibers intermediate in size between microfilaments and microtubules. They consist of four (tetramer) fibrils twisted together and help cells resist pulling forces.

How do intermediate filaments support cells, and what are some specialized names for them?

They attach to desmosome plaques and act like internal guy-wires. They are called neurofilaments in nerve cells and keratin filaments in epithelial cells.

What are microtubules and what are they made of?

The largest cytoskeletal elements. They are hollow tubes made of protein subunits called tubulins and are constantly assembled and disassembled. Most radiate from the centrosome.

What are the major functions of microtubules?

They help determine overall cell shape and organelle distribution, tether organelles in place, provide tracks for intracellular transport, and participate in cell division.

What are motor proteins?

ATP-powered protein complexes involved in movement. They carry organelles and other substances around the cell using microtubules as tracks.

What is the centrosome?

A microtubule-organizing center near the nucleus. It contains a granular matrix and a pair of barrel-shaped centrioles positioned at right angles to each other. Newly assembled microtubules radiate outward from it.

What are the major functions of centrioles?

They help organize microtubules, contribute to cell division, and form the basis of cilia and flagella.

What are the three types of cellular extensions and their general functions?

Cilia and flagella help move the cell or move materials across its surface. Microvilli increase the cell's surface area.

What is the difference between cilia and flagella?

Cilia are short, whiplike extensions found in large numbers that sweep substances such as mucus across a cell surface. Flagella are longer and propel the entire cell, such as the tail of a sperm.

What are basal bodies and what microtubule arrangements are found in cilia/flagella vs. centrioles?

Basal bodies are centrioles that form the base of each cilium or flagellum. Cilia and flagella have a 9 + 2 microtubule pattern, while centrioles have a 9 + 0 pattern.

How do cilia move substances?

Cilia alternate between a power stroke and a recovery stroke. Together, thousands of cilia create a current that moves substances in one direction across the cell surface.

What are microvilli and what do they do?

Minute fingerlike extensions of the plasma membrane found on cells such as intestinal and kidney tubule cells. They increase surface area for absorption and contain a core of actin microfilaments that stiffens them.

What is the nucleus and what is its main function?

The nucleus is the largest organelle and contains the genetic blueprints for synthesis of nearly all cellular proteins. It responds to signals that determine the kinds and amounts of proteins that need to be synthesized.

What do uninucleate, multinucleate, and anucleate mean?

Uninucleate = one nucleus, which describes most cells. Multinucleate = many nuclei, as in skeletal muscle, certain bone cells, and some liver cells. Anucleate = no nucleus, as in red blood cells.

What are the three main structures of the nucleus?

The nuclear envelope, nucleoli, and chromatin.

What is the nuclear envelope?

A double-membrane barrier surrounding the nucleoplasm. Its outer layer is continuous with rough ER and has ribosomes. Its inner layer, the nuclear lamina, is a protein mesh that maintains nuclear shape and provides scaffolding for DNA.

What do nuclear pores do?

They allow substances to move into and out of the nucleus. Nuclear pore complexes guard the pores and regulate transport of specific large molecules.

What are nucleoli and what do they do?

Dark-staining spherical bodies in the nucleus involved in rRNA synthesis and ribosome subunit assembly. They are associated with nucleolar organizer regions containing DNA that codes for rRNA, and there are usually one or two per cell.

What is chromatin made of and how is it organized?

Chromatin consists of about 30% DNA, 60% histone proteins, and 10% RNA. Its fundamental units are nucleosomes, in which DNA is wrapped around histone proteins.

How can histones affect gene expression?

Chemical alterations of histones can affect DNA and therefore help regulate gene expression.

What is the relationship between chromatin and chromosomes?

Chromosomes are condensed chromatin. Chromatin condenses during cell division to help protect the fragile chromatin threads.