Molecular and Cellular Behavior

Almost every aspect of biology involves interaction between different components and systems. It starts all the way at the cellular level with the interactions of cell organelles that allow a cell to function and it goes all the way up to the way different ecosystems come together to form complex communities and interactions. It is these interactions that make biological systems complex and how cells are specialized in one animal affects the way that animal interacts with the others around it. These interactions create ever changing and unique properties that make organisms function in the way in which they do so.

A voltage-gated sodium ion channel opens when there is a change in the voltage of the membrane and allows sodium ions to flow across its electrochemical gradient. These voltage-gated channels are made up of amino acids and they aid in generating and moving an action potential down a membrane or axon (Brooker, Robert, 106).

Introduction: Cell membranes contain many different types of molecules which have different roles in the overall structure of the membrane. Phospholipids form a bilayer, which is the basic structure of the membrane. Their non-polar tails form a barrier to most water soluble substances. Membrane proteins serves as channels for transport of metabolites, some act as enzymes or carriers, while some are receptors. Lastly carbohydrate molecules of the membrane are relatively short-chain polysaccharides, which has multiple functions, for example, cell-cell recognition and acting as receptor sites for chemical signals.

* A ) (1) neurotransmitter released (2) diffused across the synaptic cleft to a receptor protein (3) binding of the transmitter opens pores in the ion channels and positive ions move in.

24.Which of the following are common means by which binding of an intercellular chemical messenger with a cell’s receptor brings about an intracellular response?

Voltage-gated ion channels maintain the concentrations of different ions inside and outside of the neuron cell.

Cells likewise speak with each other all the more straightforwardly through the items that they discharge. For example, a neuron cell transfers an electrical heartbeat using neurotransmitters . The neurotransmitters are put away in vesicles and lie beside the cytoplasmic face of the plasma layer. At the point when the proper flag is given, the vesicles holding the neurotransmitters must reach the plasma film and emit their substance into the synaptic intersection, the space between two neurons, for the other neuron to get those neurotransmitters.

Lastly, carrier proteins affect whether a molecule will be able to pass through a biological membrane. Carrier proteins are used if a molecule is too large to pass through channels. If there are many carriers, then not only the process will be quick but it will also allow more molecules to come in.

Four ways that large molecules and substances are transported across a membrane include phagocytosis, pinocytosis, receptor-mediated endocytosis and receptor proteins. During phagocytosis, the cell engulfs a particle by wrapping pseudopodia around the particle and packing the particle within the food vacuole (membranous sac). Once the food vacuole integrates with a lysosome (w/ hydrolytic enzyme), the particle will be digested. The second way is pinocytosis, in which the cell takes in “droplets” of extracellular fluid and packs it into tiny vesicles; after this, the tiny vesicles are then transported into the cell because the molecules dissolved in the droplets are the main factors that the cells need. The third process is known as receptor-mediated endocytosis which the cells takes in large quantities of specific substances of all concentration in the Extracellular (EC) fluid; the membranes of the cell vesicle are embedded with proteins that has certain receptor sites that are exposed to the EC fluid in which ligand binds to. Then, the last step is that the receptor proteins cluster in regions of the membrane known as coated pits which contain fuzzy layer of coat proteins on the exterior; then, each coated pit forms a vesicle which contains the ligand molecules and after the ingested material is released from the vesicle, the vesicles then recycle the receptors to the plasma

Peptides hormones are usually large and hydrophilic charged, and cannot diffuse across a plasma membrane. Therefore the receptors they bind to are on the cell surface. When the peptide hormone binds to the receptor of the cells surface of the target cell it activates the receptor and as a result transmit a signal to the cellular interior. The purpose of this signal can be to turn on a protein kinase that phosphorylates (which is a modification of proteins in which an amino acid residue is phosphorylated) specific proteins and alter their activity however it could also release a second messenger into the cell this cell can be calcium, this amplifies the signal and changes many different cellular

Cell membranes are surrounded by a phospholipid bilayer that provides a semipermeable barrier for cells, separating the cytosol from the extracellular environment. Phospholipids are ampithatic, meaning that they have a hydrophilic head and hydrophobic tail, which causes the heads to face outwards towards the water and the tails inwards, creating the bilayer [figure 1]. Small hydrophobic molecules such as O2 and CO2 and small uncharged polar molecules such as H2O and ethanol can diffuse through this bilayer, however larger molecules and ions cannot, and thus require proteins, which are polymers of amino acids joined together by strong peptide bonds. These proteins feature throughout the membrane, and account for around 50% of its mass [http://www.ncbi.nlm.nih.gov/books/NBK9898/] . Not only are proteins required for transport of molecules through the membrane, but they also transport signals and are necessary for the cell support; throughout this essay I will focus on the pivotal role they play with regards to the transport of these molecules and signals, and what occurs when these functions are inhibited.

Different transducer receptors are activated depending on the perceived form of information. For example, TRPV2 and TRPV1 perceive the sensation of heat and are thus activated by capsaicin, the active ingredient of hot peppers. Once the transducer receptor is activated it leads to a flow of ions through the receptors to generate an action potential. Depolarisation of the membrane potential occurs when sodium and potassium ions flow down their electrochemical gradient resulting in a generator potential. For this to occur, the voltage gated potassium and sodium channels must open. The greater the stimulus, the more the membrane potential is depolarised allowing the threshold of an action potential to be reached. Moreover, the duration of depolarisation depends on how long the stimulus is being applied. Once depolarisation reaches its threshold in the primary afferent fibres an action potential is generated and the neurotransmitters are released in the dorsal horn of the spinal

Selective permeability due to this bilayer and its various proteins regulates what can and cannot enter cells. Some molecules need help to enter the cell, but many enter the cell through passive

The objective of this lab was to learn how to identify diffusion and osmosis, through selectively permeable membranes. Diffusion is the process in which particles move from an area of high concentration to an area of low concentration. When water enters or leaves a cell, it is called osmosis, which is the same process as diffusion, but solely focused on water. Certain membranes allow only particular chemicals to pass. These are called selectively permeable membranes.

Once hormones have been produced by glands, they are distributed through the body via the bloodstream. As hormones travel through the body, they pass through cells or along the plasma membranes of cells until they encounter a receptor for that particular hormone. Hormones can only affect target cells that have the appropriate receptors. This property of hormones is known as specificity. Hormone specificity explains how each hormone can have specific effects in widespread parts of the body.