Structure and Function of Cells and Organelles Essay Example

located in the nucleus, to assemble insulin amino acids into proteins. The nucleus acts as the central control center for the cell, containing DNA that governs all cellular functions and carries the genetic code essential for protein synthesis.
3. Website Image of Structure of a Ribosome - http://publications.nigms.nih.gov

The nucleus, which is surrounded by the nuclear envelope, is a lipid bilayer that contains large pores. This membrane selectively controls the movement of proteins and RNA into and out of the nucleus. It acts as a barrier, separating the contents of the nucleus from the cytoplasm, including DNA. To see an image depicting the structure of the nucleus, you can visit this website: http://www.emc.maricopa.edu.

The endoplasmic reticulum (ER) is responsible for synthesizing proteins and lipids that make up most organelles in cells. It consists of membranes distributed throughout the cell, which can vary in their organization - appearing either loosely or tightly arranged.

The region responsible for insulin production is called the RER, as it is lined with ribosomes. Ribosomes utilize information from nucleic acids in order to create the insulin protein. Once a rough version of the protein is formed, it is transported to the intricate network of membranes within the ER. Within this system, enzymes alter the molecule, dividing it into two peptide chains known as the A and B chain. These chains are then connected by a third chain called the connecting peptide or C peptide (as illustrated below). 5.

Website Image of C peptide chain - http://t0.gstatic.com

The storage form of insulin is known as proinsulin. Proinsulin is transported from the endoplasmic reticulum (ER) to the Golgi in a transport vesicle. The Golgi is composed of stacked,

flattened, hollow membranous sacs. In the Golgi, insulin is prepared for secretion by folding it in a specific way that creates chemical bonds between some of the amino acids. The folded proinsulin is then stored in a small membrane-enclosed sac called a vesicle. The vesicles for secretion are formed by pinching off cavities within the Golgi.

The vesicle's membrane has similarities to the cell membrane. Enzymes play a role in separating the connecting peptide chain from the A and B chains, resulting in C peptide and active insulin. The vesicle then joins with the cell membrane in the golgi to release insulin and C peptide into the bloodstream (as depicted in diagram below: cell transport). The cell membrane possesses partial permeability, allowing specific substances to pass through while blocking others. It exhibits a fluid mosaic structure (shown in image below), composed of a phospholipid bilayer that provides protection for the cell, offers structural support, and regulates movement of molecules into and out of the cell. This bilayer consists of two layers containing fatty acid chains and a phosphate group attached to a glycerol backbone.The lipid bilayer of the cell membrane consists of hydrophilic heads and hydrophobic tails, with the heads oriented towards water and the tails facing away. To enhance stability, proteins and cholesterol molecules are integrated into the membrane. These proteins serve multiple roles including regulating particle movement, functioning as enzymes, and acting as markers that interact with chemicals and molecules inside and outside the cell.Carbohydrates, proteins, and lipids in the cell membrane combine to form glycoproteins and glycolipids. These substances function as receptors for hormones and play a role in cellular recognition.

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contains an illustration of the Fluid Mosaic Model.

There are five methods of cell transport: Diffusion, Osmosis, Facilitated diffusion, Active Transport (which requires energy), and Cytosis (including Endocytosis and Exocytosis). The explanations for each method are as follows:

1. Diffusion: This involves the movement of particles from areas with high concentration to areas with low concentration.

2. Osmosis: It refers to the diffusion of water through a partially permeable membrane.

3. Facilitated Diffusion: In this process, embedded membrane proteins act as channels that enable molecules to diffuse across them.

4. Active Transport: ATP is required for this method to move particles against a concentration gradient across the membrane. Carrier proteins are utilized, and embedded proteins change shape to open or close passages on the membrane.

5.Cytosis: This encompasses both Endocytosis (bringing something into the cell) and Exocytosis (expelling something out of the cell).

Insulin is released from pancreatic cells into the bloodstream through exocytosis. Insulin and C peptide are both found in secretory vesicles within the golgi apparatus and gather in the cytoplasm. When a beta cell is stimulated, the vesicle containing insulin and C peptide merges with the cell membrane, causing insulin to be released from the cell. At the same time, the vesicle membrane becomes part of the cell membrane. This process allows insulin to be discharged into the bloodstream by pancreatic cells, where it crucially regulates blood sugar levels.