cell signaling, regulating mechanism and structure

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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