Cellular level of organisations.

Hand written note of 1year bpharm and dpharm ch-2 cellular level of organisationCELLULAR LEVEL OF ORGANISATION

• Cell :- cell is basic structural and functional into unit of all organism

- The living organism can be categorised into unicellular or multicellular organism plants and humans etc.

- a body consists of about 100 trillion cells with the size and mass 10 micro metre and one nanogram respectively.

• Cell are of two type 

1. Prokaryotic cells :- they do not have well developed nucleus through they have some other organelles present as in eukaryotic cell.

ex- archaebacteria.

2.Eucaryotic cell :- Hindi sell well developed nucleus and other organelles are present within the cell example plants animal etc.

• Function of the cell :- 

 Different function performed by a cell as follow :-

1. Cell growth and metabolism :- cell growth either by increasing its number or its size.

-- During the metabolism of various anabolic and catabolic process occur.

-- In catabolic process the cell breakdown the complex molecules to produce energy and the energy is then released.

-- In anabolic process the cell utilise energy to synthesise complex molecules and perform other biological function.

2. Cell division :-  it involves the splitting of a single cell i.e mother said split into two daughter cell. Thisthis result is the in the growth of multicellular organism and breeding of a unicellular organism.

-- during the cell division DNA is also synthesized and the process is known as replication.

3.Protein synthesis :- it occurs within the cell by two major step transcription and translation.

4. Molecule transport :-  the cell must be able to acquire nutrients and other molecules to survive.

• STRUCTURE OF THE CELL :-

A cell comprises of the following three basic component :- 

1. Cell membrane ( or plasma membrane )

2. Cytoplasm and 

3. Nucleus 

1. Cell membrane / plasma membrane

✓ The cell membrane is a selectively permeable biological membrane allowing only certain substance to pass through it. ✓it acts as a barrier between the inner and outer surface of the cell.

✓It is also known as plasma membrane or plasmalemma.

✓It compromise mainly of protein and liquid along with other living molecules.

Propertybof cell membrane :-

✓ it got the cell from the external environment.

The cell membrane allow cellular transport ✓between cell

It helped recognising a cell.

✓ the cell membrane divide the cell into smaller sections which having different structure and function.

✓ the plasma membrane of a stable site for the catalyzes and binding of enzyme.

✓it enables motility of the cellular organelles.

Structure of the cell membrane ( fluid mosaic model) :-

-- explain nature and function of cell membrane various models had been proposed in past are :-

1. Danielli and davson model / lamellar theory

2. Unit membrane model

3. Robertson's model

4. Lipid bilayer model

5. Fluid mosaic model ( important)

however out of given models fluid mosaic model is the most accepted one. The fluid mosaic model of plasma membrane was given by SJ singer (university of California) and (GL Nicholson cell institute) in early 1970s.

Function of cell membrane :- 

1. Protection of cell :-   the receptor present on the cell membrane aloud chemical message to pass between sale and system which provide protection to cell.

2. Providing cytoskeleton and mechanical support :-  biological membrane provide a specific shape to the cell.

it provide mechanical support and maintain the membrane potential. Attach protein on cell membrane build the extracellular and intracellular components.

3. Separation from surrounding:-  the cell membrane in an animal cell separate the internal environment from that of the external.

Other organisms include fungi, plant and bacteria consists of an additional layer known as cell.

4.Tissue formation :-   group of single cell attached to the extracellular matrix and form tissue.

5. Contribution to enzyme activity  :- plasma membrane control the activity of enzyme which further participate in metabolism and immune system.

• CYTOPLASM    :- 

√ Cell consist cytoplasm and enclosed within the plasma membrane.

√ The cytoplasm includes various organelles present inside a cell and therefore these organisms are also referred to as cytoplasmic organelles.

Function of cytoplasm :- 

1. Cytoplasm provide the cell site for cell growth and expansion.

2. Cytoplasm provide space for organelles to remain suspend in medium.

3. It also helped in the movement of several element within the cell.

4. cytoplasm has enzyme which help in breaking the large molecules into smaller ones. So other organisms can use them easily.

Cytoplasm divide into three parts :- 

1. Cytosol :- ✓ it refers to the fluid present inside the cell.

✓ majority of cell metabolism take place within the cytosol.

✓ cytosolic proteins perform a significant function in  signal transduction and glycolytic pathway.

✓ cytosolic protein also act as ribosomes and intracellular receptor.

2. Cytoplasmic organelles :-  ✓ cell consists of specialised organelles Golgi bodies Mitochondaria, endoplasmic reticulum, lysosomes  etc.

(i) Mitochondria- ✓ most of the cell contains a double membrane and cell organelles called mitochondria.

✓ it is also known as powerhouse of cell because they generate most of the cells, supply of ATP which is used as a source of chemical energy.

---Mitochondria double membrane and cell organelles having following parts:- 

a. Outer membrane :- this membrane contain transport proteins, this protein are helpful in transporting ions and atom across the organelles.

b. Inner membrane 

c. Mitochondrial matrix 

(ii) Golgi bodies :-  ✓ all the cell contain Golgi bodies however it is larger than those cell.

✓  That facilitate the synthesis and export of protein via endoplasmic reticulum to the Golgi complex.

-- Structure of golgi bodies.

✓ Golgi  body apparatus consists of membrane bound stocks called cisternae.

✓ each cisternae consists of flattened membrane disc that carry Golgi enzymes.

---The cisternae stocks companies of following four functional portion :- 

a). Cis-golgi network.     b)  Medial-Golgi

c). Trans- Golgi                d). Trans-golgi network.

--- Function of golgi bodies :- 

Golgi body perform different functions are:-

a). Modification sorting and packaging :- 

 Golgi body plays an important role in shortening, modification and packaging of substance for use within the cell and cell secretion.

b). Modification of protein 

✓ Protein delivered by rough endoplasmic reticulum are modified by the Golgi apparatus.

✓ it is also take part in lysosomes and transport leopard to the adjoining area of the cell.

c). Formation of spindle :-  

Golgi body d is involved in the formation of of meiotic and mitotic spindle.

d). Excretion of water :- 

This organ is helping in excreting excess amount of water.

(iii). Lysosomes :- 

The word lysosomes derived from Greek "lysis" means "to separate" and "soma" "means body".

Strycture of lysosomes :- 

✓ lysosomes are single membrane cell organelles that are spiracle in shape

✓ These enzymes are best at acidic pH 5 and inactivate at natural PH.

✓ Lysosomes vary in size ranging from 0.1 to 1.2 um.

✓ virus or bacteria damaged organelles and food material present within the cell are digested by lysosomes.

✓ Lysosomes are secretory vesicles formed from the Golgi complex.

Function of lysosomes :- 

✓ Help dissolve blood clots and thrombi.

✓ Cause the sperm to penetrate the ovum.

✓ Restoration of bone.

✓ Lysosomes helps in absorption of water and small molecule in kidney and urinary bladder.

✓ Engulf the damage cellular organelles.

(iv) Endoplasmic reticulum :- 

the endoplasmic reticulum is a complex channel system and closed within the membrane in the form of three-dimensional network.

Structure of endoplasmic reticulum :- 

the lamina and nuclear envelope of the endoplasmic reticulum together extend up to the surface of the cell.

-- Three type of endoplasmic reticulum :- 

a). Rough endoplasmic reticulum (RER):- 

small particle of RNA known as ribosomes are found in close association within the membrane of endoplasmic reticulum which gives the rough appearance of the membrane.

b). Smooth endoplasmic reticulum (SER) :- 

The membrane of SER do not contain ribosomes and help in the metabolism of carbohydrate and lipid.

c). Sacroplasmic Reticulum (SR) :- 

most of the smooth and stated muscle consists of a unique type of smooth ER called sacro plasmic reticulum.

The SER and SR differ in their structure composition.

-- Function of endoplasmic reticulum :- 

✓ endoplasmic reticulum act as a structural framework of the cytoplasm.

✓ It exchange material with the cytosol by active transport osmosis and diffusion.

✓ Protein synthesis by its surface found ribosomes are collected and stored by are RER.

✓ Different metabolic enzyme present in the the the SER.

• NUCLEUS :- 

Nucleus is a spherical organelles that consists of a double layered membrane built up of phospholipid and protein.

✓ nucleus is also known as the control centre of the cell.

✓ in a quiet Excel it is enclosed within the membrane and consists mostly of genetic material of the cell.

Function of Nucleus

most of the physiological activities of cell are controlled the nucleus

✓ specified enzyme attic protein found in the cell.

✓ along with its direct involvement in the  reproduction.

✓ it also functions to encode all the genetic information.

✓ genetic information carries the hereditary characteristics in living organism.

• CELL JUNCTION :- 

Cell junction aur present between self harming tissue.

the junction are present at various points cell to cell contact however their number and significance is more in the epithelial tissue.

their specialised structure and they do not allow the movement of water, solutes and cell from one compartment to body to another.

These are three type of junction :- 

1. Tight or occuluding junction (zonule occudens):- 

✓ tight junctions are found in epithelial tissue.

The surface membrane of adjacent cell are joint and sealed together via these tight junction.

2. Adhering junction :-

✓ As the name suggests the junction from a strong adhesion side between the cell.

✓ These junction player primary role in preventing separation of cell.

✓ these are present in cell epithelial and cardiac muscle tissue.

3. Gap or Nexus Junctions :- 

✓ They involve the adherence of adjoining cell membrane.

✓ In gap junction channel are form to connect the cytoplasm of two cells.

• TRANSPORT ACROSS MEMBRANE :- 

 The selective permeable nature of cell membrane prevent the passage of organication and other intracellular protein outside the cell.

✓ Transport of different structure across the cell membrane depend on their properties like molecular size, lipid solubility, and electronic  charges and transportation protein.

-- substance are transported across the cell membrane mainly by two type of transport :- 

1. Active transport

2. Passive transport

1. Active transport  :- opposite of passive transport active transport may either by bi primary or secondary active transport it is low to higher particle movement.

a). Primary active transport :- 

it involved the transport of substances against the concentration gradient by utilise the energy obtained from ATP.

ex- Na+ k+  Atpasepump

b). Secondary Active Transport :- 

secondary active transport generally occurs secondary to chemical gradient from the Na+k+ atpase pump.

ex- absorption of na+ ions. 

2. Passive  transport :- 

It include passive and facilitated diffusion.

(i) passive diffusion :-   it is characterized by transport of substance against their concentration gradient and electrical gradient.

✓ this type of diffusion is not depend on energy 

example diffusion of water across cell membrane.

(ii) Facilitate Diffusion :- it is characterized by transport of substance along their concentration gradient or electrical gradient.

✓ in this type of transport and it is not dependent one energy

 for example presence of glucose transporter protein help in the transport of glucose in RBC and muscle cell.

✓ it provide facility higher to lower concentration without required of energy so there is no energy requirement.

✓ it is a downhill movement hai to lower particle movement.

• EXOCYTOSIS  :- 

it is a process by which the content of a cell are released outside the cell.

The following mechanism :- 

✓ Biosynthesis in the cell result in the formation of certain product which are enclosed in the membrane vesicles.

✓ The under undigested substance produced within the cytoplasm and main enclosed in the membrane to form vesicles is called exocytic vesicles.

✓ ATP and Ca are generally required for the process example secretion of hormones from cell.

• ENDOCYTOSIS :- 

It is a reverse of exocytosis it includes phagocytosis, phenocytosis 

i) phagocytosis :- in this process foreign substance like bacteria, dead cell etc are surrounded by plasma membrane of the cell to form phagosome.

Phagocytosis referred to cell eating.

ii) pinocytosis :- pinocytosis is a process in which substance are involved by forming vasicles similar to that in phagocytosis. Pinocytosis is referred to cellular drinking.

• CELL DIVISION :- 

The process by which a parent cell divides into two daughter cell is known as cell division.

Cell division is of two types

i)Mitosis.         ii) Meiosis 

i) Mitosis - a type of cell division in which the chromosomes present in the nucleus of a parent cell divides into two identical daughter is termed as mitosis.

✓ in mitosis daughter nuclear is similar to parents cell

✓ it is a continuous process of four face

1. Prophase - this phase of mitosis is characterized by condensation of the chromatin material into chromosomes.

2.Metaphase - in this page chromatics are aligned along the middle of the nucleus of the cell by the spindle fibres and forming a plate like structure known as metaphase plate.

3.Anaphase - in this phase of mitosis it's characterized by division of the centromers.

✓ sister chromatids get separated and move towards the corresponding poles.

✓ now these chromatids are termed as chromosomes.

✓ chromosomes are pulled by the microtubules and forming v shaped.

4. Cytokinosis - This stage is marked by cytoplasmic division such that two identical cell are formed along with the formation of organelles.

• INTRACELLULAR SINGALLING PATHWAY ACTIVATION BY EXTRACELLULAR SIGNALLING MOLECULES.

Various physiological function is a multicellular organisms are basically coordination by the mechanism of intracellular signalling (or intercellular communication).

✓ This type of signalling enable a single cell to affect the behaviour of other cell in a specific way

✓ Intercellular signalling primary users external signals in the form of messengers (sensory signal or hormones).

✓ these external signals are produced by Singh nal producing cells and recognise to target cell.

 

-- There are three spets for intracellular signalling pathways :- 

1. Reception of external signals.

2. Activation and deactivation of signalling transducer.

3. Processing of multiple signals.

Cell division :-