Unit 2: Topic 2 - Cell Structure and Function Flashcards
What is the role of the endoplasmic reticulum (ER) in order to support cellular functions?
The endoplasmic reticulum is the transportation system of a eukaryotic cell and is in charge of the production, processing, and transport of both proteins and lipids. The endoplasmic reticulum consists of the smooth ER and the rough ER.
What is the role of the rough endoplasmic reticulum (RER)?
The rough endoplasmic reticulum (RER) is called “rough” because of the many ribosomes attached to the outer surface of the membrane, giving it a rough appearance in electron micrographs. These ribosomes are not permanently attached to the ER but become attached when they begin synthesizing proteins destined for modification within the RER:
* Inside the RER, proteins are chemically modified to induce their three-dimensional functional shape and to chemically “tag” them for delivery to specific cellular destinations.
* The RER participates in transporting these proteins to other locations in the cell. The proteins are transported in vesicles that pinch off from the ER. All secreted proteins pass through the RER.
* Most membrane-bound proteins are made on the RER.
What is the role of the smooth endoplasmic reticulum (SER)?
The SER lacks ribosomes and is more tubular (less like flattened sacs) than the RER. The SER has four important roles:
• It is responsible for the chemical modification of small molecules taken in by the cell that may be toxic to the cell. These modifications make the targeted molecules more polar, so they are more water-soluble and easily removed.
• It is the site for glycogen degradation in animal cells.
• It is the site where lipids and steroids are synthesized.
• It stores calcium ions, which when released trigger a number of cell responses, including muscle contraction.
What is the role of the mitochondria and its double membrane?
The mitochondria is the site of cellular respiration, which is where ATP is synthesized. The mitochondrial double membrane provides compartments for different metabolic reactions that occur during cellular respiration.
What is the role of the lysosomes?
Lysosomes contain hydrolases (digestive enzymes), and they are the sites where macromolecules—proteins, polysaccharides, nucleic acids, and lipids—are hydrolyzed into their monomers. There may be dozens of lysosomes in a single cell.
What is the role of the vacuole?
Vacuoles occur in many eukaryotic cells, particularly those of plants and fungi. There can be one large vacuole or many small ones in a cell. The general function of vacuoles is to be in charge of the storage and release of macromolecules and cellular waste products. Many freshwater protists have contractile vacuoles, whose function is to get rid of the excess water that rushes into the cell. Plant vacuoles have several functions:
• Storage: Like all cells, plant cells produce a variety of toxic by-products and waste products. Plants store many of these in vacuoles. Because they are poisonous or distasteful, these stored materials deter some animals from eating the plants, and may thus contribute to the plants’ defenses and survival.
• Structure: In many plant cells, enormous vacuoles take up more than 90 percent of the cell volume and grow as the cell grows. The presence of dissolved substances in the vacuole causes water to enter it from the cytoplasm (which in turn takes up water from outside the cell), making the vacuole swell like a water-filled balloon. The plant cell wall resists the swelling, causing the cell to stiffen from the increase in water pressure. This pressure is called turgor pressure, and it helps support the plant.
• Reproduction: Some pigments in the petals and fruits of flowering plants are contained in vacuoles. These pigments—the red, purple, and blue anthocyanins—are visual cues that help attract animals, which assist in pollination and seed dispersal.
• Catabolism: In the seeds of some plants, the vacuoles contain enzymes that hydrolyze stored seed proteins into monomers. The developing plant seedling uses these monomers as building blocks and sources of energy.
In what organelle does photosynthesis occur? In what organelle does cellular respiration occur?
Photosynthesis occurs in the chloroplast. Cellular respiration occurs in the mitochondria, aka the “powerhouse of the cell.”
Why is the folding of the inner membrane of the mitochondria important?
The folding of the inner membrane increases the surface area available for mitochondrial/ cellular respiration.
What structures are located in the chloroplast?
The chloroplasts contain the thylakoids and the stroma.
How are the thylakoids organized in the chromosomes?
The thylakoids are a series of internal membranes that look like stacks of flat, hollow discs. Each stack is called a granum (grana, for plural).
What do the thylakoid membranes contain that allow for light energy to be converted into chemical energy?
The thylakoid membranes contain chlorophyll pigments and electron transport proteins that comprise the photosystems.
What photosynthetic reactions occur in the grana of a chloroplast?
The light-dependent reactions, aka the light reactions.
What is the stroma of a chloroplast?
The stroma is the fluid within the inner chloroplast membrane and outside of the thylakoid.
What photosynthetic reactions occur in the stroma of a chloroplast?
The carbon fixation (also known as the “Calvin-Benson cycle” or the “dark reactions”) reactions of photosynthesis occur in the stroma.
What cellular respiration process occurs in the matrix, the gel-like material found in a mitochondria?
The Krebs cycle (citric acid cycle) reactions occur in the matrix of the mitochondria.
