Cell structure Flashcards
Which are the Organelles of a cell?
Organelles in Cell
- Cytoskeleton
- Centrosome
- Cilia and flagella
- Ribosome
- Endoplasmic reticulum (ER)
- Golgi complex
- Lysosome
- Peroxisome
- Proteasome
- Mitochondrion
Explain Cytoplasm
Cytoplasm
Description: Cellular contents between the plasma membrane and nucleus, including cytosol and organelles.
Function: Site of all intracellular activities except those occurring in the nucleus.
Explain Cytosol
Cytosol
Description: Composed of water, solutes, suspended particles, lipid droplets, and glycogen granules.
Function: Liquid in which many of the cell’s chemical reactions occur.
Explain Organelles
Organelles
Description: Specialized cellular structures with characteristic shapes and specific functions.
Function: Each organelle has one or more specific functions.
Explain Cytoskeleton.
Cytoskeleton - Organelle
Description: Network composed of three protein filaments:
- microfilaments
- intermediate filaments
- microtubules.
Function: Maintains shape and general organization of cellular contents; responsible for cell movements.
Explain Centrosome
Centrosome - Organelle
Description: Paired centrioles plus pericentriolar material.
Function: Pericentriolar material is organizing center for microtubules and mitotic spindle.
Explain Cilia and flagella
Cilia and flagella - Organelle
Description: Motile cell surface projections with inner core of microtubules.
Function: Cilia move fluids over a cell’s surface; a flagellum moves an entire cell.
Explain Ribosome
Ribosome - Organelle
Description: Composed of two subunits containing ribosomal RNA and proteins; may be free in cytosol or
attached to rough ER.
Function: Protein synthesis.
Explain Endoplasmic Reticulum (ER)
Endoplasmic reticulum (ER) - Organelle
Description: Membranous network of folded membranes Rough ER is studded with ribosomes and is attached to the nuclear membrane; smooth ER lacks ribosomes.
Function: Rough ER is the site of synthesis of glycoproteins and phospholipids; smooth ER is the site of fatty acid and steroid synthesis. Smooth ER also releases glucose into the bloodstream,inactivates or detoxifies drugs and potentially harmful substances, and stores and releases calcium ions for muscle contraction.
Explain Golgi complex
Golgi complex
Description: A stack of 3–20 flattened membranous sacs called cisterns.
Function: Accepts proteins from rough ER; forms glycoproteins and lipoproteins; stores, packages, and exports proteins.
Explain Lysosome
Lysosome - Organelle
Description: Vesicle formed from Golgi complex; contains digestive enzymes.
Function: Fuses with and digests contents of vesicles; digests worn-out organelles (autophagy), entire cells (autolysis), and extracellular materials.
Explain Peroxisome
Peroxisome - Organelle
Description: Vesicle containing oxidative enzymes.
Function: Detoxifies harmful substances, such as hydrogen peroxide and associated free radicals.
Explain Proteasome
Proteasome - Organelle
Description: Tiny barrel-shaped structure that contains proteases, enzymes that cut proteins.
Function: Degrades unneeded, damaged, or faulty proteins by cutting them into small peptides
Explain Mitochondrion
Mitochondrion - Organelle
Description: Consists of outer and inner membranes, cristae, and matrix.
Function: Site of reactions that produce most of a cell’s ATP.
Explain Nucleus
Nucleus
Description: Consists of nuclear envelope with pores, nucleoli, and chromatin (or chromosomes).
Function: Contains genes, which control cellular structure and direct most cellular activities
Explicit Functions:
- Controls cellular structure.
- Directs cellular activities.
- Produces ribosomes in
nucleoli
Describe and explain function of Plasma Membrane
Plasma Membrane
Description: Composed of a lipid bilayer consisting of phospholipids, cholesterol, and glycolipids with various proteins inserted; surrounds cytoplasm.
Function: Protects cellular contents; makes contact with other cells; contains channels, transporters, receptors, enzymes, and cell-identity markers; mediates the entry and exit of substances.
Explain Microfilaments
Microfilaments - Cytoskeleton
The thinnest elements of the cytoskeleton are the microfilaments which are concentrated at the
periphery of a cell and contribute to the cell’s strength and shape.
Microfilaments have two general functions:
providing mechanical support and helping generate
movements. They also anchor the cytoskeleton to integral proteins in the plasma membrane and provide support for microscopic, fingerlike projections of the plasma membrane called
microvilli; micro- small; -villi tufts of hair;
singular is microvillus). Because they greatly increase the surface area of the cell, microvilli are abundant on cells involved in absorption, such as the cells that line the small intestine. Some microfilaments extend beyond the plasma membrane and help cells attach to one another or to extracellular materials. With respect to movement, microfilaments are involved in muscle contraction, cell division, and cell locomotion. Microfilament-assisted movements include the migration of embryonic cells during development, the invasion of tissues by white blood cells to fight infection, and the migration of skin cells during wound healing.
Explain Intermediate filaments
Intermediate filaments - Cytoskeleton
As their name suggests, intermediate filaments are
thicker than microfilaments but thinner than microtubules. They are found in parts of cells subject to
tension (such as stretching), help hold organelles such as the nucleus in place, and help attach cells to one another.
Explain Microtubules
Microtubules - Cytoskeleton
The largest of the cytoskeletal components, microtubules
are long, hollow tubes Microtubules help determine cell shape and function in both the movement of organelles, such as secretory vesicles, within a cell and the migration of chromosomes during cell division. They also are responsible for movements of cilia and flagella.
Name the three main components of a generalized Cell
Three main components of a generalized Cell
- Plasma membrane
- Cytoplasm
- Nucleus
Explain the Transcription Phase in Protein Synthesis
Transcription
During transcription, which occurs in the nucleus, the genetic information in DNA base triplets is copied into a complementary sequence of codons in a strand of RNA. Transcription of DNA is catalyzed by the enzyme RNA polymerase, which must be instructed where to start the transcription process and where to end it. The segment of DNA where RNA polymerase attaches to it is a special sequence of nucleotides called a promoter, located near the beginning of a gene. Three kinds of RNA are made from DNA: mRNA, rRNA & tRNA.
Explain the Translation Process
Translation
Translation is the process in which mRNA associates with ribosomes and directs synthesis of a protein by converting the sequence of nucleotides in mRNA into a specific sequence of amino acids. Translation occurs in the following way :
- An mRNA molecule binds to the small ribosomal subunit, and a special tRNA, called initiator tRNA, binds to the start codon (AUG) on mRNA, where translation begins.
- The large ribosomal subunit attaches to the small subunit, creating a functional ribosome. The initiator tRNA fits into position on the ribosome. One end of a tRNA carries a specific amino acid, and the opposite end consists of a triplet of nucleotides called an anticodon. By pairing between complementary nitrogenous bases, the tRNA anticodon attaches to the mRNA codon. For example, if the mRNA codon is AUG, then a tRNA with the anticodon UAC would attach to it.
- The anticodon of another tRNA with its amino acid attaches to the complementary mRNA codon next to the initiator tRNA.
- A peptide bond is formed between the amino acids carried by the initiator tRNA and the tRNA next to it.
- After the peptide bond forms, the empty tRNA detaches from the ribosome, and the ribosome shifts the mRNA strand by one codon. As the tRNA bearing the newly forming protein shifts, another tRNA with its amino acid binds to a newly exposed codon. Steps 3 through 5 repeat again and again as the protein lengthens.
- Protein synthesis ends when the ribosome reaches a stop codon, at which time the completed protein detaches from the final tRNA. When the tRNA vacates the ribosome, the ribosome splits into its large and small subunits.
Give an overview of the Protein Synthesis
Overview of the Protein Synthesis
