1.Neeraj spears historic Olympics gold

The 23-year-old javelin thrower becomes the first Indian to win an athletics event at the Games

On an incredible Saturday in Japan, the Land of the Rising Sun, India found its brightest athletics star. Neeraj Chopra’s history-altering effort in the men’s javelin throw at the Tokyo Olympics landed India’s maiden athletics gold at the Games. With his best at 87.58 m, Neeraj soared high.

It was also the nation’s second individual gold at the Olympics, with Neeraj following in the footsteps of shooter Abhinav Bindra, who delivered the shiny metal at the 2008 Beijing edition.

For a nation that made its Olympics debut in 1900, the wait for an athletics gold spilled past a century and two decades before Neeraj offered deliverance.

Incidentally at the Paris Games in 1900, Norman Pritchard won two athletics silvers for India but back then the country was a dominion of Britain.

After that, India basked in the glories that hockey initially offered and lapsed into agony with the near-misses of Milkha Singh, P.T. Usha and Dipa Karmakar, while some in shooting, boxing, weightlifting and tennis offered respite.

Hailing from Haryana, Neeraj, the 23-year-old Subedar with the 4 Rajputana Rifles, has been Mr. Consistent ever since he burst upon the junior scene.

The transition to the senior category was seamless and he excelled at the Commonwealth and Asian Games before finding his Everest moment at Tokyo. He did it with swagger while being conscious of history as he dedicated his medal to the late Milkha Singh.

Punia bags bronze

While Neeraj offered enduring lustre, wrestler Bajrang Punia gleaned a bronze in the 65 kg freestyle segment by defeating Kazakhstan’s Daulet Niyazbekov.

India at Olympics

India first participated at the Olympic Games in 1900, with a lone athlete (Norman Pritchard) winning two medals- both silver- in athletics. The nation first sent a team to the Summer Olympic Games in 1920, and has participated in every Summer Games since then. India has also competed at several Winter Olympic Games beginning in 1964. Indian athletes have won a total of 28 medals so far, all at the Summer Games. For a period of time, India national field hockey team was dominant in Olympic competition, winning eleven medals in twelve Olympics between 1920 and 1980. The run included 8 gold medals total and six successive gold medals from 1928–1956.

The Indian Performance at the Olympics has seen improvement in the past decade,however Rio 2016 was a disappointment considering the hopes the nation had garnered looking at our athlete’s performance in World Cups or Other Top Tier global Tournaments. The Indian Olympic Association sent the nation’s largest ever delegation (a total of 117 athletes; 34 larger than their previous record of 83 athletes in 2012) in Summer Olympic history. India won only two medals with one silver medal in Badminton by P.V. Sindhu and Other by Sakshi malik in wrestling. Most of our athletes at Rio 2016 performed way below their optimal potential and many had near misses too,which can be attributed to nervousness,lack of big stage nerves and inability to acclimatize to foreign weather ( specifically for archery and shooting ). Government of India has constituted a Task Force to prepare a comprehensive action plan for effective participation of Indian sports persons in the next three Olympic games 2020, 2024 and 2028. The Task Force will prepare overall strategy for sports facility, training, selection procedure and other related matters. The Task Force will comprise of members who are in house experts as well as those from outside. Prime Minister Narendra Modi asked states to set up similar panels as “lot more” needs to be done to improve India’s performance in sports.

2.Sunderbans is now drowning in plastic

Unregulated inflow of relief materials has resulted in a new crisis in the fragile ecosystem

Unregulated inflow of relief to the Sunderbans has resulted in a new crisis in the cyclone-battered region: plastic waste. Several NGOs, experts, and even officials of the District Police and the Forest Department have pointed out that the plastic accumulating on the isolated islands of the fragile ecosystem are cause for great concern.

Ecologist Diya Banerjee has been pointing out the issue from as early as June, days after Cyclone Yaas inundated large parts of the Sunderbans in the last week of May 2021.

“What we are seeing is tonnes of plastic in the remote areas of the Sundarbans, like Gosaba, Mousuni, Bali, Patharpratima and Kultali. People residing in these areas are not responsible in any way for the huge plastic waste; it is outsiders who are introducing and bringing a large quantity of plastics, completely oblivious and ignorant to its long-term impact on the region,” Ms. Banerjee said. She added that a local NGO Mahajibon had recovered about 300 kg of plastic waste from the Gosaba block days after Cyclone Yaas.

While it is difficult to estimate the total amount of plastic waste that is arriving in about 50 inhabited islands of the Sunderbans spread across thousands of square kilometres, Sourav Mukherjee of the Kolkata Society for Cultural Heritage has estimated about 56 tonnes of plastic in the Gosaba block alone. “We have calculated the amount on the basis of how much packaged relief material was received by families, how many times, in the past few weeks,” Mr. Mukherjee said.

Long-term impact

Not only conservationists, even police officers have raised concerns over the huge dumping of plastic waste. Arijit Basu, Additional Superintendent of Police, Baruipur Police District of South 24 Parganas, had put up a post on social media a few weeks ago, pointing out that relief workers brought plastic water bottles, which were being disposed everywhere. The police officer urged locals and NGOs to organise cleanliness drives to remove plastic from the Sunderbans.

Tuhin Ghosh, Director of the School of Oceanographic Studies, Jadavpur University, said that plastics would have a long-term ecological impact on the Sundarbans ecosystem.

“The presence of plastic in saline water will increase the toxicity of water gradually and also there will be eutrophication of water. Because of the presence of plastics in the water, there will be an increase in microplastics, which will slowly enter the food system,” Professor Ghosh said.

He said that the Sunderbans were connected to the sea and the increase of plastic in the region could lead to plastic waste entering the ocean.

Sundarbans

• It is a vast contiguous mangrove forest ecosystem in the coastal region of Bay of Bengal spread over India and Bangladesh on the delta (world’s largest) of the Ganges, Brahmaputra and Meghna rivers.
  • It contains the world’s largest mangrove forests.
• Much of the area has long had the status of a forest reserve, but conservation efforts in India were stepped up with the creation of the Sundarbans Tiger Reserve in 1973.
• Sundarbans National Park, established in 1984, constitutes a core region within the tiger reserve; it was designated a UNESCO World Heritage site in 1987.
• Sunderbans was designated as a Biosphere Reserve by UNESCO in 2001.
• Sundarban Wetland, India was recognised as the ‘Wetland of International Importance’ under the Ramsar Convention in January 2019.
• Sunderban National Park is known for its wide range of fauna, including 260 bird species and is home to many rare and globally threatened wildlife species such as the Estuarine Crocodile, Royal Bengal Tiger, Water Monitor Lizard, Gangetic Dolphin and Olive Ridley Turtles.
• The Sunderbans Delta is the only mangrove forest in the world inhabited by tigers.
  • For its preservation, Discovery India and World Wide Fund (WWF) India partnered with the Government of West Bengal and local communities in the Sundarbans in 2019.

Mangroves

• Mangroves are the plant communities occurring in inter-tidal zones along the coasts of tropical and subtropical countries.
• Mangrove forests perform multiple ecological functions such as production of woody trees, provision of habitat, food and spawning grounds for fin-fish and shellfish, provision of habitat for birds and other valuable fauna; protection of coastlines and accretion of sediment to form new land.
• Among the states and Union Territories, West Bengal has the highest percentage of area under total Mangrove cover followed by Gujarat and Andaman and Nicobar Islands.
• The India State of Forest Report gives the data about mangroves and their conditions in the country.

3.Location of Dara Shikoh’s grave still a mystery

The Centre had formed a committee to find the spot in the Humayun’s Tomb complex in 2020

The final resting place of Mughal prince Dara Shikoh remains a mystery, with the Archaeological Survey of India saying it has not located the grave within the Humayun’s Tomb complex over a year after a committee was formed for the job.

In response to a Right to Information query by The Hindu, the ASI on July 28 replied “no” when asked if it had located the grave of Dara Shikoh inside the complex. The government’s quest for locating the grave, which some believe is among the many unmarked graves inside the complex, started in February 2020. Then Culture Minister Prahlad Singh Patel had announced the setting up of a committee to locate the grave.

Dara Shikoh, who was Mughal emperor Shah Jahan’s son and expected heir, was killed on the orders of his brother Aurangzeb in 1659 after losing the war of succession. While there are some mentions of his grave in texts, there has not been a consensus among historians as to where exactly he was laid to rest.

On December 17, 2020, speaking during a ceremony at Rahim’s Tomb, Mr. Patel said the committee had submitted its interim report and that after one more meeting, it would be publicly released. Mr. Patel said it was Dara Shikoh who was responsible for making the Upanishads available to the West as he had them translated. Then, on March 9 this year, Mr. Patel replied to a question in the Rajya Sabha that a committee had been formed to study the tangible and cultural heritage of Dara Shikoh and Rahim Khan-e-Khana. “Tangible remains of Dara Shikoh are expected outcome. Report of the committee is awaited,” his reply stated.

Members of the panel have failed to reach a consensus. One of the members of the committee, retired ASI Additional Director-General B.R. Mani, was of the opinion that there was enough evidence to say that one of the three unmarked cenotaphs in a row marked Dara Shikoh’s resting place. Mr. Mani told The Hindu on Saturday that he had submitted his own opinion to the ASI a few months ago. Interestingly, a South Delhi Municipal Corporation (SDMC) engineer Sanjeev Kumar Singh had claimed that Alamgirnama, the history of Aurangzeb’s reign, said that Dara Shikoh was buried with emperor Akbar’s sons, Daniyal and Murad. Mr. Mani said he agreed.

Some sceptical

Other committee members, however, were sceptical. Former Joint Director-General of ASI R.S. Bisht said “there was no irrefutable evidence” about the location of the grave. He added that Alamgirnama was written by the court historian of Aurangzeb who would have wanted to paint him in a better light. “If he [Aurangzeb] really cared, he wouldn’t have had his brother killed and his body paraded through Delhi,” Mr. Bisht said. He added that there were other ways to honour Dara Shikoh, “a man of letters” who was known for his “tolerance and academic aspects”, like restoring his library and the dargahs of Sufi saints he followed.

A committee member and former ASI Director (Archaeology), Syed Jamal Hassan, said it was difficult to identify the grave as there were no inscriptions, and references did not confirm the site as well. He added that he had submitted his opinion to the ASI, that he disagreed with the SDMC engineer’s claim. He said the three cenotaphs in question were on one platform and looked to be made at the same time.

Humayun’s Tomb:

• About:
  • This tomb, built in 1570, is of particular cultural significance as it was the first garden-tomb on the Indian subcontinent.
    • It inspired several major architectural innovations, culminating in the construction of the Taj Mahal.
  • It was built under the patronage of Humayun’s son, the great Emperor Akbar.
  • It is also called the ‘dormitory of the Mughals’ as in the cells are buried over 150 Mughal family members.
  • It is an example of the charbagh (a four quadrant garden with the four rivers of Quranic paradise represented), with pools joined by channels.
  • The United Nations Educational Scientific and Cultural Organisation (UNESCO) recognized it as a World Heritage Site in 1993.
• Mughal Architecture:
  • About:
    • This is a building style that flourished in northern and central India under the patronage of the Mughal emperors from the mid-16^th to the late 17^th century.
    • The Mughal period marked a striking revival of Islamic architecture in northern India. Under the patronage of the Mughal emperors, Persian, Indian, and various provincial styles were fused to produce works of unusual quality and refinement.
    • It became so widespread especially in north India that these can be seen further in the colonial architecture of Indo-Saracenic style.
  • Important Features:
    • Mixed Architecture: It was a blend of Indian, Persian, and Turkish architectural style.
    • Diversity: Different types of buildings, such as majestic gates (entrances), forts, mausoleums, palaces, mosques, sarais, etc.
    • Building material: Mostly, red sandstone and white marble were used.
    • Speciality: Specific features such as the Charbagh style of the mausoleums, pronounced bulbous domes, slender turrets at the corners, broad gateways, beautiful calligraphy, arabesque, and geometric patterns on pillars and walls, and palace halls supported on pillars.
      • The arches, chhatri, and various styles of domes became hugely popular in the Indo-Islamic architecture and were further developed under the Mughals.
  • Some Examples:
    • Taj Mahal:
      • Built by Shah Jahan between 1632 and 1653, in memory of his wife Mumtaz Mahal.
      • UNESCO recognized the Taj Mahal as a World Heritage Site in 1983. It is located in Agra.
    • Red Fort:
      • Built by Shah Jahan in 1618 when he decided to move the capital from Agra to Delhi. It was the residence of Mughal rulers.
      • UNESCO designated it as the World Heritage Site in 2007.
    • Jama Masjid:
      • Built by Shah Jahan in Delhi. The construction was completed in 1656.
    • Badshahi Mosque:
      • Built during the reign of Aurangazeb. At the time of completion in 1673, it was the largest mosque in the world. It is located in Lahore, capital of the Pakistani province of Punjab.

4.New technique to study ultrasmall particles in cells

The technique exploits the quantum emission properties of erbium-doped nanoparticles

Researchers from IIT Madras and IISER Kolkata have developed a method to detect minute quantities of chemicals in solution. They use a variation of absorption spectroscopy that surpasses the systemic limits imposed by conventional absorption spectroscopy. With this technique, they can, in principle, illuminate the insides of cells and detect minuscule quantities of substances present there. The work was published in Nanoscale.

Spectroscopy, the tool

Absorption spectroscopy is a tool to detect the presence of elements in a medium. Light is shone on the sample, and after it passes through the sample is examined using a spectroscope. Dark lines are seen in the observed spectrum of the light passed through the substance, which correspond to the wavelengths of light absorbed by the intervening substance and are characteristic of the elements present in it. In usual methods, about a cubic centimetre of the sample is needed to do this experiment.In the method developed here, minute amounts of dissolved substances can be detected easily.

Usually in absorption spectroscopy, the principle used is that light because of its wavelike nature, shows diffraction patterns, that is, dark and light fringes, when it scatters off any object. A related concept called the Abbe criterion sets a natural limit on the size of the object being studied. According to this criterion, the size of the observed object has to be at least of the order of the wavelength of the light being shone on it. “If you want to perform absorption spectroscopy using visible light, namely, blue, green and red, the wavelengths [of these colours] are about 400 nm, 500 nm and 600 nm, respectively. the diffraction limit is typically half of that, about 200 nm for the blue light,” explains Basudev Roy, from the Department of Physics of IIT Madras and one of the corresponding authors of the study along with Ayan Banerjee of IISER Kolkata.

In the method used by the researchers here, tiny, nano-sized particles that can absorb light being shone on them and re-emit red, blue and green light were employed. “We use a nanoparticle of sodium yttrium fluoride (a kind of glass) with some dopants, which has the special property that when you excite this with infra-red light at 975 nm, it emits blue, green and red light from the particle itself,” says Dr Roy. These particles were made by M. Gunaseelan at Department of Physics, University of Madras.

Like a bar magnet

The particles emit electric fields that are analogous to how a tiny magnet would give off magnetic lines of force – this is called a dipole, and the particle is like a tiny mobile phone’s antenna. “Our dipole… generates an electromagnetic field depending upon the quantum properties of the erbium dopants in the glass. Our emission pattern is typically limited to a cone of 45 degrees, starting from a diameter of the size of the particle,” he adds.

The absorption leaves a gap in the reflected light, which is what is observed and used to analyse the nature of the absorbing material. Since this works at the level of photons, this surpasses the limit on the size of the substance or sample being studied.

Inside living cells

There are many potential applications. “We are ourselves going to put these particles inside living cells, and the emission can be used as a tiny flash lamp to look for absorption from individual molecules in the close proximity to the particle,” he says. “This is way in which small molecules almost ten-millionth of a mm in diameter can be detected while these pass the emission region of the glass particle… The future is to use it to measure individual molecules, see an absorption spectroscopy of a single DNA or protein molecule.”

Cell

Robert Hooke	Discovered and coined the term cell in 1665
Robert Brown	Discovered Cell Nucleus in 1831
Schleiden and Schwann	Presented The cell theory, that all the plants and animals are composed of cells and that the cell is the basic unit of life. Schleiden (1838) and Schwann (1839).

• With the discovery of the electron microscope in 1940, it was possible to observe and understand the complex structure of the cell and its various organelles.

Cell Organelles

Plasma Membrane or Cell Membrane

• Cell membrane is also called the plasma membrane.
• It can be observed only through an electron microscope.
• Plasma membrane is the outermost covering of the cell that separates the contents of the cell from its external environment.

Endocytosis

• The plasma membrane is flexible and is made up of organic molecules called lipids and proteins.
• The flexibility of the cell membrane also enables the cell to engulf in food and other material from its external environment. Such processes are known as endocytosis (endo → internal; cyto → of a cell). Amoeba acquires its food through such processes.

Diffusion

• Plasma membrane is a selectively permeable membrane [The plasma membrane is porous and allows the movement of substances or materials both inward and outward].
• Some substances like carbon dioxide or oxygen can move across the cell membrane by a process called diffusion [spontaneous movement of a substance from a region of high concentration (hypertonic solution) to a region where its concentration is low (hypotonic solution)].
• Thus, diffusion plays an important role in gaseous exchange between the cells as well as the cell and its external environment.

Osmosis

• Water also obeys the law of diffusion. The movement of water molecules through a selectively permeable membrane is called osmosis.
• Osmosis is the passage of water from a region of high water concentration through a semi-permeable membrane to a region of low water concentration. Thus, osmosis is a special case of diffusion through a selectively permeable membrane.
• Unicellular freshwater organisms and most plant cells tend to gain water through osmosis. Absorption of water by plant roots is also an example of osmosis.
• Thus, diffusion is important in exchange of gases and water in the life of a cell. In additions to this, the cell also obtains nutrition from its environment.
• Different molecules move in and out of the cell through a type of transport requiring use of energy in the form of ATP.

Reverse Osmosis (RO)

• Reverse osmosis (RO) is a water purification technology that uses a semipermeable membrane to remove larger particles from drinking water.
• In reverse osmosis, an applied pressure is used to overcome osmotic pressure.
• Reverse Osmosis is a phenomenon where pure water flows from a dilute solution [hypotonic] through a semi permeable membrane to a higher concentrated solution [hypertonic].
• Semi permeable means that the membrane will allow small molecules and ions to pass through it but acts as a barrier to larger molecules or dissolved substances.

Cell Wall

• Cell wall is absent in animals.
• Plant cells, in addition to the plasma membrane, have another rigid outer covering called the cell wall. The cell wall lies outside the plasma membrane.
• The plant cell wall is mainly composed of cellulose. Cellulose is a complex substance and provides structural strength to plants.

Plasmolysis

• When a living plant cell loses water through osmosis there is shrinkage or contraction of the contents of the cell away from the cell wall. This phenomenon is known as plasmolysis (plasma → fluid; lysis → disintegration, decomposition).
• Only living cells, and not dead cells, are able to absorb water by osmosis. Cell walls permit the cells of plants, fungi and bacteria to withstand very dilute [hypotonic] external media without shrinkage.
• In such media the cells tend to lose water by osmosis. The cell shrinks, building up pressure against the cell wall. The wall exerts an equal pressure against the shrunken cell.
• Cell wall also prevents the bursting of cells when the cells are surrounded by a hypertonic medium (medium of high concentration).
• In such media the cells tend to gain water by osmosis. The cell swells, building up pressure against the cell wall. The wall exerts an equal pressure against the swollen cell.
• Because of their walls, plant cells can withstand much greater changes in the surrounding medium than animal cells.

Cytoplasm

• It is the jelly-like substance present between the cell membrane and the nucleus.
• The cytoplasm is the fluid content inside the plasma membrane.
• It also contains many specialized cell organelles [mitochondria, golgi bodies, ribosomes, etc].
• Each of these organelles performs a specific function for the cell.
• Cell organelles are enclosed by membranes.
• The significance of membranes can be illustrated with the example of viruses.
• Viruses lack any membranes and hence do not show characteristics of life until they enter a living body and use its cell machinery to multiply.

Nucleus

• It is an important component of the living cell.
• It is generally spherical and located in the center of the cell.
• It can be stained and seen easily with the help of a microscope.
• Nucleus is separated from the cytoplasm by a double layered membrane called the nuclear membrane.
• This membrane is also porous and allows the movement of materials between the cytoplasm and the inside of the nucleus [diffusion].
• With a microscope of higher magnification, we can see a smaller spherical body in the nucleus. It is called the nucleolus.
• In addition, nucleus contains thread-like structures called chromosomes. These carry genes and help in inheritance or transfer of characters from the parents to the offspring. The chromosomes can be seen only when the cell divides.
• Gene is a unit of inheritance in living organisms. It controls the transfer of a hereditary characteristic from parents to offspring. This means that your parents pass some of their characteristics on to you.
• Nucleus, in addition to its role in inheritance, acts as control center of the activities of the cell.
• The entire content of a living cell is known as protoplasm [cytoplasm + nucleus]. It includes the cytoplasm and the nucleus. Protoplasm is called the living substance of the cell.
• The nucleus of the bacterial cell is not well organized like the cells of multicellular organisms. There is no nuclear membrane.
• Every cell has a membrane around it to keep its own contents separate from the external environment.
• Large and complex cells, including cells from multicellular organisms, need a lot of chemical activities to support their complicated structure and function.
• To keep these activities of different kinds separate from each other, these cells use membrane-bound little structures (or ‘organelles’) within themselves.

Chromosomes

• The nucleus contains chromosomes, which are visible as rod-shaped structures only when the cell is about to divide.
• Chromosomes contain information for inheritance of features from parents to next generation in the form of DNA (deoxyribo nucleic acid)
• Chromosomes are composed of DNA and Protein.
• DNA molecules contain the information necessary for constructing and organizing cells. Functional segments of dna are called genes.
• In a cell which is not dividing, this dna is present as part of chromatin material. Chromatin material is visible as entangled mass of thread like structures. Whenever the cell is about to divide, the chromatin material gets organised into chromosomes.
• The nucleus plays a central role in cellular reproduction, the process by which a single cell divides and forms two new cells.
• It also plays a crucial part, along with the environment, in determining the way the cell will develop and what form it will exhibit at maturity, by directing the chemical activities of the cell.

Prokaryotic Cells vs. Eukaryotic Cells

• Organisms whose cells lack a nuclear membrane, are called prokaryotes (pro = primitive or primary; karyote ≈karyon = nucleus).
• Organisms with cells having a nuclear membrane are called eukaryotes.
• Prokaryotic cells also lack most of the other cytoplasmic organelles present in eukaryotic cells.
• Many of the functions of such organelles are also performed by poorly organised parts of the cytoplasm.
• The chlorophyll in photosynthetic prokaryotic bacteria is associated with membranous vesicles (bag like structures) but not with plastids as in eukaryotic cells.

Prokaryotes → defined nuclear region, the membrane-bound cell organelles are absent.

Eukaryotic Cells → have nuclear membrane as well as membrane-enclosed organelles.

	Prokaryotes	Eukaryotes
Organisms	Monera: Eubacteria and Archebacteria	Protists, Fungi, Plants and Animals
Meaning of name	Pro = before Karyon = nucleus	Eu = after Karyon = nucleus
Evolution	3.5 billion years ago (older type of cell)	1.5 billion years ago
Uni-/multicellular	Unicellular (less complex)	Multicellular (more complex)
Cell wall	almost all have cell walls (murein)	fungi and plants (cellulose and chitin): none in animals
Organelles	usually none	many different ones with specialized functions
Metabolism	anaerobic and aerobic: diverse	mostly aerobic
Genetic material	single circular double stranded DNA	complex chromosomes usually in pairs; each with a single double stranded DNA molecule and associated proteins contained in a nucleus
Location of genetic information	Nucleoid region	Nucleus
Mode of division	binary fission mostly; budding	mitosis and meiosis using a spindle: followed by cytokinesis

Nucleoid

• In some organisms like bacteria, the nuclear region of the cell may be poorly defined due to the absence of a nuclear membrane. Such an undefined nuclear region containing only nucleic acids is called a

Vacuoles

• Empty structure in the cytoplasm is called vacuole. It could be single and big as in an onion cell (plant cell). Cheek cells (animal cells) have smaller vacuoles.
• Large vacuoles are common in plant cells. Vacuoles in animal cells are much smaller.
• Vacuoles are storage sacs for solid or liquid contents.
• The central vacuole of some plant cells may occupy 50-90% of the cell volume.
• In plant cells vacuoles are full of cell sap and provide turgidity [swollen and distended or congested] and rigidity to the cell.
• Many substances of importance in the life of the plant cell are stored in vacuoles. These include amino acids, sugars, various organic acids and some proteins.
• In single-celled organisms like amoeba, the food vacuole contains the food items that the amoeba has consumed.
• In some unicellular organisms, specialized vacuoles also play important roles in expelling excess water and some wastes from the cell

Endoplasmic Reticulum (ER)

• The endoplasmic reticulum (ER) is a large network of membrane-bound tubes and sheets. It looks like long tubules or round or long bags (vesicles).
• The ER membrane is similar in structure to the plasma membrane.
• There are two types of ER –– rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum (SER).

Rough Endoplasmic Reticulum RER – Ribosomes

• RER looks rough under a microscope because it has particles called ribosomes attached to its surface.
• The ribosomes, which are present in all active cells, are the sites of protein manufacture.
• The manufactured proteins are then sent to various places in the cell depending on need, using the ER.

Smooth Endoplasmic Reticulum SER

• The SER helps in the manufacture of fat molecules, or lipids, important for cell function.

Functions of Endoplasmic Reticulum (ER)

• Some of these proteins and lipids help in building the cell membrane. This process is known as membrane biogenesis.
• Some other proteins and lipids function as enzymes and hormones.
• Although the ER varies greatly in appearance in different cells, it always forms a network system.
• Thus, one function of the ER is to serve as channels for the transport of materials (especially proteins) between various regions of the cytoplasm or between the cytoplasm and the nucleus.
• The ER also functions as a cytoplasmic framework providing a surface for some of the biochemical activities of the cell.
• In the liver cells of the group of animals called vertebrates, SER plays a crucial role in detoxifying many poisons and drugs.

Golgi Apparatus or Golgi Complex

• The golgi apparatus consists of a system of membrane-bound vesicles arranged approximately parallel to each other in stacks called cisterns.
• These membranes often have connections with the membranes of ER and therefore constitute another portion of a complex cellular membrane system.
• The material synthesized near the ER is packaged and dispatched to various targets inside and outside the cell through the golgi apparatus.
• Its functions include the storage, modification and packaging of products in vesicles.
• In some cases, complex sugars may be made from simple sugars in the golgi apparatus.
• The golgi apparatus is also involved in the formation of lysosomes.

Lysosomes

• Lysosomes are a kind of waste disposal system of the cell.
• Lysosomes help to keep the cell clean by digesting any foreign material as well as worn-out cell organelles.
• Foreign materials entering the cell, such as bacteria or food, as well as old organelles end up in the lysosomes, which break them up into small pieces. Lysosomes are able to do this because they contain powerful digestive enzymes capable of breaking down all organic material.
• During the disturbance in cellular metabolism, for example, when the cell gets damaged, lysosomes may burst and the enzymes digest their own cell. Therefore, lysosomes are also known as the ‘suicide bags’ of a cell.
• Structurally, lysosomes are membrane-bound sacs filled with digestive enzymes. These enzymes are made by RER.

Mitochondria

• Mitochondria are known as the powerhouse of the cell.
• The energy required for various chemical activities needed for life is released by mitochondria in the form of ATP (Adenosine Triphosphate) molecules.

[If Mitochondria is the Power Plant. ATP is the Electricity].

• ATP is known as the energy currency of the cell.
• The body uses energy stored in ATP for making new chemical compounds and for mechanical work.
• Mitochondria have two membrane coverings instead of just one.
• The outer membrane is very porous while the inner membrane is deeply folded. These folds create a large surface area for ATP-generating chemical reactions.
• Mitochondria are strange organelles in the sense that they have their own DNA and ribosomes. Therefore, mitochondria are able to make some of their own proteins [ribosomes prepare proteins].

Plastids

• You might have noticed several small colored bodies in the cytoplasm of the cells of Tradescantia leaf. They are scattered in the cytoplasm of the leaf cells. These are called plastids.
• They are of different colours. Some of them contain green pigment called chlorophyll. Green coloured plastids are called chloroplasts. They provide green colour to the leaves.
• Chloroplasts are important for photosynthesis in plants.
• Chloroplasts also contain various yellow or orange pigments in addition to chlorophyll.
• Plastids are present only in plant cells. There are two types of plastids – chromoplasts (coloured plastids) and leucoplasts (white or colourless plastids).
• Leucoplasts are primarily organelles in which materials such as starch, oils and protein granules are stored.
• The internal organization of the plastids consists of numerous membrane layers embedded in a material called the stroma.
• Plastids are similar to mitochondria in external structure. Like the mitochondria, plastids also have their own dna and ribosomes.