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Transcript of Cell Biology
The Big Picture
Fluid environment that contains all the organelles excluding the nucleus. The cytoplasm also contains starch granules, mineral crystals and lipid droplets that remain suspended in the liquid.
Cell organelles that contain RNA and proteins. The ribosomes exist in two places in the cell, either bound to the Endoplasmic Reticulum or floating in the cytosol. Ribosomes, composed of a large and small subunit, are the site of protein synthesis.
Through selective permeability, this layer regulates what enters and leaves the cell often through osmosis and diffusion.
Though often mistaken as being another name for cytoplasm, cytosol is in fact a part of the cytoplasm. Whereas cytoplasm is the name for the organelles and fluid combined. The cytosol is the term referring to only the gel-like fluid in the cytoplasm that holds the organelles in place.
Cytoplasm vs Cytosol
The process of protein synthesis is displayed in the image (above). The mRNA, carries the template for building a specific protein, the tRNA carries the amino acid. The tRNA contains 3 binding sites, the aminoacyl binding site, the peptidyl binding site, and the exit binding site. Once the amino acids are polymerized, the ribosome releases the protein.
The nucleus, found only in eukaryotic cells, contains and protects chromosomes that contain DNA which is the genetic information of the cell. The nucleus also controls the cell's growth and reproduction by mediating the replication of DNA during the cell cycle.
Made up of proteins and nucleic acids, the nucleolus is the site of transcription, where the DNA is transcribed onto mRNA. These mRNA would then leave the nucleoluus and join the ribosomes, which are also made in the nucleolus.
Rough Endoplasmic Reticulum
Referred to as rough because it is studded with ribosomes, the Rough ER takes polypeptides and amino acids from the cytosol and continues protein assembly. The Rough ER will also determine destinations for the proteins.
Smooth Endoplasmic Reticulum
Referred to as smooth, because it is not studded with ribosomes, the Smooth ER is devoted almost exclusively to the formation of lipids (fats) and the metabolism of them. The Smooth ER also has a detoxifying function where it detoxifies organic chemicals into water soluble products.
The Golgi Apparatus, consisting of a stack of 3 to 20 slightly curved flattened saccules, has one side that faces the ER (cis or inner face) and another side that faces the plasma membrane (trans or outer face). The proteins from the Rough ER and lipids leaving the Smooth ER enter the Golgi Apparatus and it sorts and packages these proteins and lipids in vesicles that depart from the trans side, often into the plasma membrane.
Mitochondria are made up of two membranes, each a phospholipid bilayer with embedded proteins. One of the membranes, the outermost, is smooth whereas the inner membrane has folds (cristae). Mitochondria are also semi-autonomous, they can replicate and grow on their own. The main function of mitochondria is to perform a process called oxidative phosphorylation with molecules such as carbohydrates, fats and proteins which thus forms ATP, energy for the cell to use.
Organelles found in virtually all eukaryotic cells, peroxisomes break down long chains of fatty acids through beta-oxidation. The peroxisomes are more likely to be found in liver cells than anywhere else because they have a prominent role in the way organisms digest alcohol and amino acids. Peroxisomes break down complex molecules into smaller molecules and in the process release hydrogen peroxide (H2O2) but the peroxisome will break hydrogen peroxide further and create water (H2O) and Oxygen (O2).
The Cytoskeleton is made up of three kinds of protein filaments: microfilaments, intermediate filaments, and microtubules. The function of the cytoskeleton is to maintain cell shape, provide mechanical strength, separate chromosomes during mitosis and meiosis and assist in intracellular transport of organelles.
There are cells in and on every living thing, including us! There are two main types, Eukaryotic and Prokaryotic. Prokaryotes lack a cell nucleus and and are often unicellular whereas eukaryotes are multi cellular and contain membrane bound organelles and nucleus. Now lets look at a eukaryotic plant cell.
Lysosomes are membrane-enclosed organelles that contain an array of enzymes capable of breaking down intracellular material like proteins, nucleic acids, lipids, and carbohydrates. Lysosomes can vary in size and shape and look like dense spherical vacuoles.
Centrioles are small, cylindrical structures that lie outside the nucleus. During mitosis, the centrioles replicate and produce the spindle fibers that attach to and move the chromosomes during cell division.
Flagella, long flexible oars protruding from the cell, aid in cell movement. Flagella,found in eukaryotic and prokaryotic cells, is also the tail that is attache to sperm.
Cilia, short hairs protruding from the cell, aid in cell movement. Cilia, mostly found in eukaryotic cells, for example can be found in the trachea helping waft mucous up the throat to be swallowed.
Vacuoles are water-filled storage spaces found in cells. They are found in both animal and plant cells but they are also bigger in plant cells. Vacuoles store food, collect waste products, and can help with cell shape and buoyancy.
Found only in plant cells, chloroplasts conduct photosynthesis. Chloroplasts absorb sunlight and use it conjunction with water and carbon dioxide to produce food and energy (ATP) for the plant.