BIO Chp. 4 - 4.8 - 4.15
Mitochondrion structure
- Outer membrane - Inter-membrane space - Inner Membrane - Mitochondrial Matrix
What is insulin?
- a secretory protein - a hormone produced and secreted by certain cells of the *pancreas* and *transported in the bloodstream*.
Peroxisomes
- are metabolic compartments that *do NOT originate* from the endomembrane system. - In fact, how they are related to other organelles is still unknown. - enzymes in the liver degrade alcohol and other harmful substances.
Lysosomes functions
- digestive functions - recycling centers (Autophagy)
Functions of the smooth ER (x3)
-synthesis of lipids, -store calcium ions needed for muscle contraction, -contain enzymes that assist with detoxification of toxic compounds.
What is the relationship of the Golgi apparatus to the ER in a protein-secreting cell?
The Golgi receives transport vesicles budded from the ER that contain proteins synthesized by bound ribosomes. The Golgi finishes processing the proteins and dispatches transport vesicles to the plasma membrane, where the proteins are secreted.
Is a food vacuole part of the endomembrane system? Explain.
Yes; it forms by pinching in from the plasma membrane, which is part of the endomembrane system.
What is embedded in the thylakoid's membranes? What does it do?
*green chlorophyll* molecules are embedded in thylakoid membranes to *trap solar energy.*
What does "endosymbiosis" mean?
- "to live within" - Mutual relationship (both organisms benefit)
Lysosome
- A digestive organelle in eukaryotic cells; contains *hydrolytic enzymes* that digest engulfed food or damaged organelles - The name lysosome is derived from two Greek words meaning "breakdown body."
Outer membrane
- A mitochondrion is enclosed by two membranes, *each a phospholipid bilayer* with a unique collection of embedded proteins - The outer membrane is the outermost membrane in the mitochondria that protects and holds the form of the organelle.
Glycoprotein
- A protein with one or more short chains attached to it. - When short chains of sugars link to the polypeptide
Transport Vesicle
- A small membranous sac in a eukaryotic cell's cytoplasm carrying molecules produced by the cell. - The vesicle buds from the endoplasmic reticulum or Golgi and eventually fuses with another organelle or the plasma membrane, releasing its contents
Chloroplasts
- An organelle found in nearly all species of plants and all photosynthetic protists that absorbs sunlight and uses it to drive the synthesis of organic compounds (such as glucose) from carbon dioxide and water - Site of photosynthesis
Mitochondria (definition and structure)
- An organelle in eukaryotic cells where cellular respiration occurs. *Enclosed by two membranes*, it is where most of the cell's *ATP* is made. - The "powerhouse" of the cell
Lysosomes as a recycling center
- Cells enclose damaged organelles or small amounts of cytosol in vesicles. A lysosome fuses with such a vesicle and dismantles its contents, *making organic molecules available for reuse.*
Steroid synthesis in the smooth ER Give an example
- Enzymes of the smooth ER are important in the synthesis of lipids, including oils, phospholipids, and steroids. - In vertebrates, for example, *cells rich in smooth ER of the ovaries and testes synthesize the steroid sex hormones*.
Smooth ER in the liver
- Our liver cells also have large amounts of smooth ER, with *enzymes that help process drugs, alcohol, and other potentially harmful substances.* - EX. As liver cells are exposed to such chemicals, the amount of smooth ER and its detoxifying enzymes increases, thereby *increasing the rate of detoxification and thus the body's tolerance to the drugs.* Also, because detoxifying enzymes often cannot distinguish among related chemicals, the growth of smooth ER in response to one drug *can increase the need for higher doses of other drugs.*
Chloroplast structure (x7)
- Outer membrane - inter-membrane space - Inner membrane - - - Stroma - - - Thylakoids (thykaloid membrane) - - - - - Granum - - - - - - - Chlorophyll molecules
Rough ER functions (x2)
- Ribosomes are the site of protein production; here, they make proteins that are "secreted" - or discharged - from the cell - Proteins are then transported to the Golgi Apparatus through transport vesicles - Makes more ER membrane to replace what was lost to the transport vesicle (membrane- making machine)
Inter-membrane space
- The inter-membrane space is the *space between the inner and outer mitochondrial membrane.* - In cellular respiration, hydrogen atoms are pumped across the inner mitochondrial membrane into the inter-membrane space, creating a proton gradient that is responsible for the production of ATP.
Endosymbiont Theory
- The theory that mitochondria and chloroplasts *originated as prokaryotic cells engulfed by an ancestral eukaryotic cell.* The engulfed cell and its host then evolved into a *single organism.* - These prokaryotes may have *gained entry to the larger cell as undigested prey or parasites.*
How might ER products be processed during their transit through the Golgi?
- Various Golgi *enzymes modify* the carbohydrate portions of the glycoproteins made in the ER, *removing some sugars and substituting others*. - *Molecular identification tags*, such as phosphate groups, may be added that help the Golgi sort molecules into different batches for different destinations.
mitochondrial matrix
- contains *mitochondrial DNA and ribosomes*, as well as *enzymes* that catalyze some of the reactions of cellular respiration. - The compartment of the mitochondrion enclosed by the inner membrane and *containing enzymes and substrates* for the citric acid cycle
Thylakoids and what thylakoids stack to form
- flattened tubules - A network of interconnected sacs that is suspended in the stroma. The sacs are often stacked like poker chips or pancakes. - Each stack is called a *granum*
What happens to the finished secretory products? (x3 options)
- move to the plasma membrane for export from the cell. - may become part of the plasma membrane itself - may become part of another organelle, such as a lysosome
Functions of vacuoles
- store materials like water, salts, proteins, and carbohydrates - as a cell ingests food, a *food vacuole* forms - Takes in and releases water
Stroma
- thick fluid that contains DNA, ribsomes, & enzymes inside the inner membrane. - surrounds the thylakoid membrane. - Sugars are made in the stroma by the enzymes of the Calvin cycle.
Central Vacuole
-Water storage -Waste storage -Gives the cell internal support - In a plant cell, central vacuoles help the cell grow in size by *absorbing water and enlarging*. - It also *stockpiles vital chemicals* and may act as a *trash can*, safely storing toxic waste products. •Vacuoles are present in some animal cells, but are much smaller and take on a variety of different roles as compared to plant cells.
Synthesis of insulin
1) As the polypeptide is synthesized by a bound ribosome following the instructions of an mRNA, the polypeptide is threaded into the cavity of the rough ER. 2) As it enters, the new protein folds into its *three-dimensional shape. 3) Short chains of sugars are often linked to the polypeptide, making the molecule a *glycoprotein* (glyco means "sugar"). 4) When the molecule is ready for export from the ER, it is packaged in a *transport vesicle,* a vesicle that moves from one part of the cell to another. 5) This vesicle buds off from the ER membrane and carries the protein to the Golgi apparatus for further processing. 6) From there, a transport vesicle containing the finished molecule makes its way to the plasma membrane and releases its contents from the cell.
Vacuoles in plants and fungi (x3)
1. In the seeds of plants, small vacuoles in storage cells can *hold reserves of proteins.* 2. Vacuoles in flower petals *contain pigments* that attract pollinating insects. 3. Vacuoles may also help protect the plant against herbivores by *storing compounds that are poisonous or unpalatable to animals.* Examples include nicotine, caffeine, and various chemicals we use as pharmaceutical drugs.
4.10 Lysosomes are digestive compartments within a cell
4.10 Lysosomes are digestive compartments within a cell
4.11 Vacuoles function in the general maintenance of the cell
4.11 Vacuoles function in the general maintenance of the cell
4.15 Mitochondria and chloroplasts evolved by endosymbiosis
4.15 Mitochondria and chloroplasts evolved by term-64endosymbiosis
4.8 The endoplasmic reticulum is a biosynthetic workshop
4.8 The endoplasmic reticulum is a biosynthetic workshop
4.9 The Golgi apparatus modifies, sorts, and ships cell products
4.9 The Golgi apparatus modifies, sorts, and ships cell products
How can we hypothesize how the symbiosis was beneficial?
In a world that was becoming increasingly aerobic from the oxygen-generating photosynthesis of prokaryotes, a host would have benefited from an endosymbiont that was able to use oxygen to release large amounts of energy from organic molecules. Over the course of evolution, the host cell and its endosymbiont merged into a single organism—a eukaryotic cell with mitochondria. If one of these cells acquired a photosynthetic prokaryote, the prokaryote could provide the host cell with nourishment. An increasingly interdependent host and endosymbiont, over many generations, could become a eukaryotic cell containing chloroplasts.
Rough ER
That portion of the endoplasmic reticulum with ribosomes attached that *make membrane proteins and secretory proteins*
All eukaryotes have mitochondria, but not all have chloroplasts. What is the evolutionary explanation?
The *first endosymbiosis* would have given rise to eukaryotic cells containing mitochondria. A *second endosymbiotic event* gave rise to cells containing chloroplasts as well as mitochondria.
How are lysosomes formed?
The enzymes and membranes of lysosomes are made by rough ER and processed in the Golgi apparatus.
What enhances the inner membrane's ability to produce ATP?
The folds called "cristae"
Inner membrane
The inner membrane is highly folded and contains many embedded protein molecules that function in ATP synthesis.
Which membrane in a chloroplast appears to be the most extensive? Why might this be so?
The thylakoids are the most extensive. The chlorophyll molecules that trap solar energy are embedded in them.
Who discovered the Golgi apparatus? When and how did he find it?
Using a *light microscope and a staining technique* he developed, Italian scientist *Camillo Golgi* discovered this membranous organelle in *1898.*
Type 1 diabetes
When the cells in the pancreas are destroyed and a lack of insulin disrupts glucose metabolism in the body.
Golgi apparatus = shipping & receiving
•The Golgi apparatus serves as a molecular warehouse and finishing factory for products manufactured by the ER. -Products travel in transport vesicles from the ER to the Golgi apparatus. -One side of the Golgi apparatus functions as a receiving dock for the product and the other as a shipping dock. -Products are modified as they go from one side of the Golgi apparatus to the other and travel in vesicles to other sites.
4.12 A review of the structures involved in manufacturing and breakdown
4.12 A review of the structures involved in manufacturing and breakdown
4.13 Mitochondria harvest chemical energy from food
4.13 Mitochondria harvest chemical energy from food
4.14 Chloroplasts convert solar energy to chemical energy
4.14 Chloroplasts convert solar energy to chemical energy
Mitochondria and chloroplasts arose by . . .
endosymbiosis
Where do most transport vesicles go after leaving the ER?
the Golgi apparatus
Peroxisomes functions
1) Some peroxisomes break down fatty acids to be used as cellular fuel. 2) In your liver, peroxisomes detoxify harmful compounds. - - In these processes, enzymes transfer hydrogen from the compounds to oxygen, producing hydrogen peroxide (H2O2). - - - Other enzymes in the peroxisome convert this toxic by-product to water—another example of the importance of a cell's compartmental structure.
Lysosomes digestive functions (two examples)
1. Many protists engulf food particles into membranous sacs called food vacuoles. Lysosomes fuse with food vacuoles and digest the food. The nutrients are then released into the cytosol. 2. Our white blood cells engulf bacteria and then destroy ("digest") them using lysosomes
What does compartmentalization have to do with lysosomes?
A lysosome provides an acidic environment for its enzymes, *while safely isolating them* from the rest of the cell.
Vacuoles
A membrane-enclosed sac that is part of the endo-membrane system of a eukaryotic cell and has diverse functions in different kinds of cells
What is cellular respiration?
A process that converts the chemical energy of food molecules to the chemical energy of ATP
Golgi apparatus
An organelle in eukaryotic cells consisting of stacks of membranous sacs that modify, store, and ship products of the endoplasmic reticulum
What do you call lysosomes? What does it mean?
Autophagy = act as a recycling center for the cell by surrounding damaged organelles and breaking them down into reusable organic molecules
Smooth ER - storage of calcium ions
EX. In muscle cells, a specialized smooth ER membrane pumps calcium ions into the interior of the ER. When a nerve signal stimulates a muscle cell, calcium ions rush from the smooth ER into the cytosol and *trigger contraction of the cell.*
How is a lysosome like a recycling center?
It breaks down damaged organelles and recycles their molecules.
Compartmentalization
Membrane-bound organelles allow different parts of the cell to perform different functions at the same time
What does the mitochondrion take in and release to make energy?
Mitochondria use CO2 and release C2 in transforming the chemical energy of foods to a form (*ATP*) that can be used for cellular work.
Individual structures of the Golgi and their function
Note that, unlike the ER sacs, the flattened Golgi sacs are not connected. 1) One side of a Golgi stack serves as a receiving dock for transport vesicles produced by the ER. 2) A vesicle fuses with a Golgi sac, adding its membrane and contents to the "receiving" side - called the *cis face* 3) Products of the ER are modified as they progress through the stack - called the *cisternae* 4) The "shipping" side - called the *trans face* - of the Golgi functions as a depot, dispatching its products in vesicles that bud off and travel to other sites.
In terms of evolution, what are mitochondrions most related to? What are three ways that prove this?
Prokaryotes 1. Mitochondria and chloroplasts contain a *single circular DNA molecule,* similar in structure to a prokaryotic chromosome 2. *Ribosomes* more similar to prokaryotic ribosomes than to eukaryotic ones. 3. Both organelles *reproduce* by a splitting process that is similar to some prokaryotes
Two parts of Endoplasmic Reticulum
Rough ER and Smooth ER
Smooth ER
That portion of the endoplasmic reticulum that is free of ribosomes.
Explain why we say that the endoplasmic reticulum is a biosynthetic workshop.
The ER produces a huge variety of molecules, including phospholipids for cell membranes, steroid hormones, and proteins (synthesized by bound ribosomes) for membranes, other organelles, and secretion by the cell.
Golgi function
The Golgi apparatus serves as a *molecular warehouse and processing station* for products manufactured by the ER.
What does the number of Golgi stacks correlate to?
The number of Golgi stacks correlates with *how active the cell is in secreting proteins* Cells can have hundreds of these stacks
Rough ER - membrane-making machine
The rough ER grows in place by adding *membrane proteins* and *phospholipids* to its own membrane. - - Polypeptides - polypeptides that are destined to be membrane proteins *grow from bound ribosomes.* They are inserted into the ER membrane. - - Phospholipids - *made by enzymes* of the rough ER and are inserted into the membrane. Thus, the ER membrane grows, and *portions of it are transferred to other components of the endomembrane system in the form of transport vesicles.*
How do transport vesicles help tie together the endomembrane system?
Transport vesicles move membranes and the substances they enclose between components of the endomembrane system.
lysosomal storage diseases GIVE AN EXAMPLE
When people lack one or more lysosomal enzymes. The lysosomes become *engorged with undigested material*, eventually interfering with cellular function. Ex. *Tay-Sachs disease* - disease due to the loss of function of a single lysosomal enzyme. -Results in lipid accumulation in the brain -Progressively destroys nerve cells -Can cause spasticity (loss of muscle function) and often death in early childhood. Fortunately, lysosomal storage diseases are rare in the general population, as they are often fatal in early childhood.
