The Nucleus and Ribosome 4.5 - 4.6/ The Endomembrane System 4.7-4.12 Expectations
The structures and functions of lysosomes.
A lysosome is a membrane enclosed sac of enzymes of digestion. They are only found in animals cells, and are located throughout the cytoplasm. The enzymes and membranes of the lysosomes are made through rough ER and processed in the Ga. They provide an acidic environment for their enzymes, and have several kinds of digestive functions. Lysosomes fuse with food vacuoles to digest food. Lysosomes are also recycling centers; cells take in damaged organelles in their membrane sacs, and the lysosome fuses with it the vesicle surrounding the organelle, and breaks it down and takes out the organic molecules that can be reused. Diseases like Tay-Sachs disease can form if people's cells don't have enough lysosomal enzymes.
Describe the endomembrane system, including smooth and rough endoplasmic reticulum, Golgi apparatus, lysosomes, vacuoles, and peroxisomes.
An endomembrane is a network of membranes inside and surrounding a eukaryotic cell, all related by physical contact or the transfer of vesicles (sacs made of membrane).
The structures and functions of peroxisomes.
Peroxisomes are like metabolic compartments, however they do not come from the endomembrane system. Some peroxisomes break down fatty acids for fuel, or some like in the liver detoxify poisonous compounds. Hydrogen peroxide is produced in this process.
Describe the functions of ribosomes. Explain why some ribosomes are free in the fluid of the cytoplasm while others are bound to the endoplasmic reticulum or nuclear envelope.
Ribosomes are machines that carry out the commands of the nucleus boss. Ribosomes use instructions from the nucleus in the form of messenger RNA (mRNA) to build proteins. The way this happens is the nucleotide sequence of an mRNA molecule is translated into the amino acid sequence of a polypeptide. Cells that make many proteins have a lot of ribosomes, like pancreas cells that make many digestive enzymes. Free and bound ribosomes are structurally the same, and also can move around and are able to function in either location. Most proteins that are made on free ribosomes function in the cytosol - enzymes that catalyze early steps of sugar breakdown for cellular respiration. Bound ribosomes make proteins that will be inserted into membranes, exported from the cell, or packaged in certain organelles.
The structures and functions of the Golgi apparatus.
The Golgi apparatus (Ga) is a stack of flattened sacs that aren't connected that is located next to the ER. The number of Ga depends on the how much protein the cell secretes. Ga is like packaging a shipping service for products manufactured in ER. Molecules start in the receiving side of the Ga, and then they travel through, being processed by enzymes by substituting sugars and phosphate groups (ID tags). Finally, the finished secretory products are packaged and either transported to other cells or other organelles within the cell.
The structures and functions of smooth and rough endoplasmic reticulum.
The largest part of the endomembrane system is the endoplasmic reticulum, an long network of flattened sacs and tubes. The tubes and sacs of the ER are not in the cytosol. The ER is one of the major manufacturing parts in the cell, with two different types. The smooth ER is smooth since it doesn't have any ribosomes attached to it. The rough ER is rough since it is studded with ribosomes. Smooth ER is important in the synthesis of lipids (especially phospholipids), oils, and steroids. For example, in vertebrate's sex cells, like the ovaries and the testes, there is lots of smooth ER to allow for the steroid synthesis needed to occur. It is also used in liver cells along with enzymes to detoxify harmful substance like drugs or alcohol. The growth of the amount of Smooth ER increases as the liver is exposed to more of these substances, resulting in a need of higher dosage in order to achieve the goal of the substance (drunk or high). Lastly, Smooth ER stores calcium ions, used in muscles to allow them to contract. Rough ER helps to transfer newly synthesized proteins and is found in places where protein is secreted, like muscles. They help to package secretory proteins and sometimes in the process link chains of sugars to the protein, making it a glycoprotein. It also makes membranes for the cell. Then the vesicles carries the protein to the Golgi apparatus.
Describe the structure and functions of the nucleus and nucleolus. Explain how DNA is packaged inside of the nucleus.
The nucleus is like the boss of the cell, decides when to produce new cells, changes cell when put in different environment, and gives the orders. Inside of the nucleus is the cell's genetic code, in the DNA (which is involved with many proteins and organized into chromosomes). When a cell is not dividing, chromosomes take form as chromatin, a very extended form of chromosomes. The nucleolus is a structure inside of the nucleus where ribosomal RNA (rRNA) is produced, based off of instructions from the DNA. Once it is made, rRNA works with proteins that are brought in from the cytoplasm to create subunits of ribosomes. After they have been made, these subunits exit the nucleus and head to the cytoplasm, where they will join to form functional ribosomes.
The structures and functions of vacuoles.
Vacuoles are large vesicles that have many functions. Contractile vacuoles have little ends thats that collect water and the center "hub" expels it outside. Some vacuoles in plants have digestive functions, and others contain pigments to attract insects to pollinate their petals. Others plants also may have poisonous substances in their vacuoles for protections. The central vacuole of plants helps the cell to grow by absorbing water. It also stores vital compounds and waste/toxic molecules.
