Biology 12 Flashcards
(17 cards)
What are Organelles?
specialized subunits within a cell that has a specific function, and it is usually separately enclosed within its own lipid bilayer
What is Rough Endoplasmic Reticulum (RER)?
Rough endoplasmic reticulum appears “pebbled” by electron microscopy due to the presence of numerous ribosomes on its surface. Proteins synthesized on these ribosomes collect in the endoplasmic reticulum for transport throughout the cell.
What is a Ribosome?
a large, complex molecular machine, found within all living cells, that serves as the primary site of biological protein synthesis. Ribosomes link amino acids together in order specified by messenger RNA (mRNA) molecules.
Ribosomes make proteins in a process called translation. You will learn more about translation later in the course. Ribosomes receive their instructions from the nucleus in the form of mRNA. Ribosomes can be found attached to the rough ER or within the cytoplasm, either singly or in groups called polyribosomes (poly means many). Proteins made in ribosomes attached to the rough ER are eventually secreted from the cell or become part of the external surface of the cell. Polyribosomes are strings of ribosomes simultaneously translating regions of the same mRNA strand during protein synthesis.
What is a Centriole?
a cylindrical cell structure composed mainly of a protein called tubulin that is found in most eukaryotic cells.
What are Mitochondria?
rod shaped organelle, located in the cytoplasm; has a smooth outer membrane and a greatly folded inner membrane, power house of the cell, breaks down food and sugars into water, supplies energy, cellular respiration occurs here.
A mitochondrion (plural: mitochondria) is the “powerhouse” of the cell because it has the ability to convert high energy carbohydrates (glucose) and oxygen into low energy carbon dioxide and water. When this occurs, large amounts of energy are released.This process is called cellular respiration.
This energy is stored in the bonds of a molecule called Adenosine Triphosphate (ATP). ATP is like ‘cellular gasoline’. It powers all the processes in cells that require energy. As ATP, the energy is much more available to cells, compared to other energy rich molecules, like carbohydrates (glucose).
What are Lysosomes?
small, round structures that use enzymes to to break down food & waste, rare in plant cells, the “garbage men” (also called cell vesicles) round organelles surrounded by a membrane and containing digestive enzymes. This is where the digestion of cell nutrients takes place.
Lysosomes are vesicles filled with hydrolytic enzymes produced by the Golgi bodies. Lysosomes move throughout the cell and fuse with vacuoles and other structures to help digest food or break down old structures for recycling or removal.
The lysosomes are also related to the processes of autolysis in cells. Autolysis is the process by which a cell self-destructs for the health of the entire organism. This usually occurs in injured cells or dying tissue. Autolysis occurs when a lysosome allows the digestive enzymes to leave through its membranes. The cell then, in effect, digests itself.
What is a Cell membrane?
the first structure you encounter in a plant cell (after cell wall) provides protection, allows things in and out of organism, plant and animal cells.
The cell membrane separates the internal environment of the cell from the external environment. It is selectively permeable, meaning that it regulates the entrance (endocytosis) and exit (exocytosis) of molecules into and out of the cell. Proteins that are packaged and secreted by the Golgi apparatus leave the cell through the cell membrane via transport vesicles. Materials entering the cell are brought in by transport vesicles that are formed by the cell membrane. You will learn more about the cell membrane’s transport processes later in the course.
What is a Vesicle?
vesicles are miniscule membrane-enclosed sacs within the cell organelles of eukaryotic cells. These sacs help transport or absorb proteins, enzymes and other cell necessities.
Vesicles are used to transport materials. Vesicles are often produced by the Golgi bodies when packaging materials for leaving the cell by exocytosis or produced by the cell membrane when importing materials by endocytosis.
What is the Golgi apparatus/body?
The Golgi Apparatus is a flattened, layered, sac-like organelle that looks like a stack of pancakes and is located near the nucleus. It produces the membranes that surround the lysosomes. The Golgi body packages proteins and carbohydrates into membrane-bound vesicles for “export” from the cell.
The Golgi Apparatus is involved in processing, packaging, and secretion. It receives lipid-filled vesicles from the smooth ER and protein-filled vesicles from the rough ER. These molecules then move from the inner face to the outer face of the Golgi apparatus. During this transition, the glycoproteins have their chains modified before they are repackaged and secreted, via vesicles, to become part of the cell membrane or to be exported out of the cell. The Golgi apparatus is also involved in the formation of lysosomes.
Because the Golgi sorts and packages proteins for transport out of cell, they are found in large amounts in cells that are secreting proteins. For example, salivary glands are packed with Golgi, as they secrete the protein enzyme called salivary amylase.
Golgi are distinguished by their ‘stack of pancakes’ arrangement of membranes and budding of vesicles along their margins.
What is Cytoplasm?
region between nucleus and cell membrane, consists of a jellylike substance, contains organelles, transports.
What is the Smooth endoplasmic reticulum (SER)?
The Smooth ER lacks ribosomes, as shown in the diagrams below where there are a lack of dots. It is responsible for the production of lipids, such as steroid hormones, fats and the lipids that make up the cell’s membrane.
What is the Nucleolus?
The prominent structure in the nucleus is the nucleolus. The nucleolus produces ribosomes, which move out of the nucleus and take positions on the rough endoplasmic reticulum where they are critical in protein synthesis.
What is the Nuclear envelope?
This is a membrane that has pores in it for substances such as mRNA to leave the nucleus and for other substances to enter the nucleus.
What is the Nucleus?
The nucleus is the most important organelle in the cell because it stores the genetic material (DNA) as chromosomes. DNA determines the cell’s characteristics and metabolic function.
The nucleus is often referred to as the “control center” of the cell because the DNA controls the cell by controlling protein synthesis. Proteins are important to the cell because they become the main structural parts of the cell and they form enzymes that direct chemical reactions within the cytoplasm and organelles.
The nucleus controls protein synthesis by sending molecular messages called messenger RNA (mRNA) to the ribosomes, where proteins are made. The nucleus converts the DNA code, which is too big to leave the nucleus, into messenger RNA (mRNA) in a process called transcription. mRNA is then “read” at the ribosomes to make structural proteins or enzyme proteins.
What are Vacuoles?
Large, round, water filled sack, stores food, water, and waste, the “refrigerator”.
Vacuoles are large vesicles that are membrane-bound sacs that store water and a variety of other substances such as proteins, sugars, minerals and wastes.
What are Eukaryotes?
Cells that have a nucleus.
What are Prokaryotes?
Cells that do not contain a nucleus.
