cell signaling, regulating mechanism and structure
TRANSCRIPT
CELL SIGNALING, REGULATING MECHANISM AND CYTOPLASM
Cytoplasm
• Consists of 80%-90% water, and salts, organic molecules, enzymes, proteins and nutrients
• Moves cellular materials through a cytoplasmic streaming mechanism
• Maintains shape and consistency of cell
• Storage space for chemical substances
• Good conductor of electricity
Nucleus
• Largest organelle in cell
• Uninucleate, binucleate, multinucleate
• Bounded by nuclear envelope
• Nucleomma Cisterna• Houses the genetic
material
Nucleus
• Regulates metabolic process in cell• Distributes genetic material equally• Site for separation of chromosomes
during cell division
Ribosome• Large and small subunit• Primary site in the process of protein synthesis• Can be found in groups or alone• Attached to Endoplasmic Reticulum
Endoplasmic Reticulum
• Complex internal membrane system
• Flattened sheets, sacs and tubes• Makes proteins and shuttles
cellular products• Involved in metabolism of fats,
production of various materials• Rough ER, smooth ER
Rough ER
• Connects polysaccharide groups to the polypeptide
• Proteins not destined for cytoplasm is synthesized here
Smooth ER
• Involved in synthesis of lipids and hormones
• Storage for calcium ions• Breaks down toxins and drugs in liver
cells
Golgi Apparatus
• Central delivery system of cell• Modify or package proteins and
lipids into vesicles• Transports lipids • Creates lysosomes and
organelles involved in digestion
Lysosome
• Contains powerful degrading enzymes
• Built in the Golgi Apparatus• Breaks down harmful products,
waste, bacteria• Tay-Sachs, Pompe’s diseases are
examples of lysosome malfunction
Peroxisomes
• Oxygen is used to oxidize substances
• Breaks down lipids and detoxifies chemicals
• Self replicates by enlarging then dividing
• Can convert hydrogen peroxide to water
Mitochondria
• Generates ATP• Found near the nucleus • Cristae are formed from folds in the inner
membrane• Have their own DNA• Similar traits with bacteria
Signal Transduction
• Forms of intercellular signaling
Extracellular signal molecules bind to specific receptors
Autocrine Signaling
A way for a cell to alter its own extracellular environment. The cell secretes chemicals outside of its membrane and the presence of those chemicals on the outside modifies the behavior of that same cell. This process is important for growth.
Paracrine Signaling
A way for a cell to affect the behavior of neighboring cells by secreting chemicals into the common intercellular space.
Endocrine Signaling
Utilizes hormones. A cell secretes chemicals into the bloodstream. Those chemicals affect the behavior of distant target cells.
Direct Signaling
A transfer of ions or small molecules from one cell to its neighbor through pores in the membrane. Those pores are called gap junctions. This is the fastest mode of cell-cell communication.
Synaptic Signaling
It is found in the nervous system. It is a highly specific and localized type of paracrine signaling between two nerve cells or between a nerve cell and a muscle cell.
Nitric oxide gas signals by binding directly to an enzyme inside the target cell
Cell Receiving Signals
• Some small molecules are capable of entering the cell through the plasma membrane.
• Some small hormones also enter the cell directly, by passing through the membrane.
There are three types of cell surface receptors:
M) Signaling via G protein linked receptorsadenylylG protein
bg areceptor
membranecytosol
extracellularspace
cyclase
GDPligand
GTP
ATPcAMP
Pi
Some G proteins regulate the production of cAMP
What is the cAMP?
Some G proteins activate the inositol phospholipid signaling pathway byactivating phospholipase C-b
Ion Channel Receptors
• When a signaling molecule binds to an ion channel on the outside of the cell, this triggers the change of the conformation of the protein and the channel opens, allowing the ions to move in or out of the cell following their electrical gradients
Transmembrane Receptors
• Transmembrane proteins include G protein-linked receptors and they are seven-pass trans membrane proteins. This means that the polypeptide chain traverses the membrane seven times.
Triggered Chemical Reactions
• the movement and binding of the G-protein
• transformation of GTP into GDP • activation of second messengers
Ca2+ functions as an intracellular second messenger
• Three main types of Ca2+ channels that mediate Ca2+ signaling:
1. Voltage dependent Ca2+ channels in the plasma membrane
2. IP3-gated Ca2+-release channels
3. Ryanodine receptors
The concentration of Ca2+ in the cytosol is kept low in resting cells
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