SCIENCE HOLIDAY HOMEWORK

NAME – CLASS –

ROLL NO –

DEV YADAVIX “B”

15

TOPIC :- CELL ORGANELLES IN HUMAN

BODY

ENDOPLASMIC RETICULUM1. In the year 1945- The lace like membranes of the endoplasmic

reticulum were first seen in the cytoplasm of chick embryo cells.

2. ER are considered as one of the components of cytoskeleton along with microtubules, microfilaments and intermediate filaments.

3. These are first of all observed by Porter, Claude and Full am in (1945) as a network.

4. The term ”Endoplasmic reticulum” was first used by Porter and Fullman (1952)

Location1. Present in almost all eukaryotic cell.

2. These are found to be absent in mature erythrocytes,ova,embryonic cells and prokaryotes.

3. The ER often occupies most of the cytoplasm.

ENDOPLASMIC RETICULUMAmount

•The ER varies in amount from cell to cell. In spermatocytes, it is represented by a few vacuoles only.

•In the cells of adipose tissue, it is quite simple, having the form of a few tubules.

•The cells that are actively synthesizing proteins, such as liver and pancreatic cells and fibroblast, have abundant ER.

•Endoplasmic reticulum forms 30-60 % of the total membrane in a cell.

PHYSICAL STRUCTURE-The ER is 3-dimensional network of intracellular. It is formed of three types of element: 1-Cisternae 2-Tubules 3-Vesicles

ENDOPLASMIC RETICULUMCisternae-

These are flattened , unbranched, sac-like element.They lie in stacks parallel to one another.They bear ribosomes on the surface that, therefore, appears rough.It contain glycoproteins named ribophorin-I & ribophorin-II that bind the ribosomes.

ENDOPLASMIC RETICULUMTubules-

These are irregular branching element which form a network along with other element.These are often free of ribosomes.Vesicles-These are oval and rounded ,vacuole like element.These are also free of ribosomes.All the element of ER freely communicates with one another, and contain a fluid called endoplasmic matrix, in the ER lumen.These matrix is different from cytoplasmic matrix outside the ERThe ER may pass from one cell to another through the plasmodesmata in the form of desmotubules.

RIBOSOMESWhat is ribosome?

Ribosome - protein synthesizer consisting

of two subunitsLarger one, “50S”, is

upper picture. Smaller is “30S”

(They look the same size here because of space restrictions.)

So what’s the purpose of ribosome?Ribosome basically a protein factory. Subunits each have role in making of proteinsTo understand exactly what each subunit does, it’s necessary to walk through protein synthesis step by step

RIBOSOMES

Protein synthesisProcess starts from DNA through “transcription”“Translation” is where ribosome comes in. Translation occurs when protein formed from code on mRNARibosome carries out the translation of the nucleotide triplets

RIBOSOMES

Protein synthesisChart - visual image of transcription and translation in protein synthesizingDNA and RNA have nucleotides that determine kind of protein3 nucleotides = 1 amino acid of a protein

RIBOSOMES

GOLGI APPARATUSDISCOVERY

Golgi apparatus is named after the scientist who discovered it.

Camillo Golgi was an Italian biologist who discovered this organelle with a light microscope in 1898.

He developed a method that stained it intensely and made possible the demonstration of its occurrence in a wide variety of cell types.

This method is known as Golgi Staining or Golgi Impregnation.

Prof. Camillo

Golgi

GOLGI APPARATUSMORPHOLOGY

The Golgi is composed of stacks of membrane-bound structures known as Cisternae.

A cisterna (plural cisternae) comprises a flattened membrane disk that makes up the Golgi apparatus.

Usually a Golgi has 6-7 cisternae.

Each Golgi stack has a distinct orientation.

A complex network of tubules and vesicles is located at the edges of these cisternae.

GOLGI APPARATUS

CIS-GOLGI

The side faces the Endoplasmic reticulum is Cis Face and is the entry face that receives small membrane vesicles from the ER.Vesicles from the endoplasmic reticulum fuse with the cis-Golgi network and subsequently progress through the stack to the trans-Golgi network.The cis is the site at which transport vesicles bringing newly synthesized products from the endoplasmic reticulum with and add their contents to the Golgi cisternae. A complex network of anatomizing (connecting) membrane tubules attach to and cover cisternae on the cis face and serve as a docking site for transport vesicles. Each region contains different enzymes which selectively modify the contents depending on where they are destined to reside.

GOLGI APPARATUS

TRANS-GOLGI

The side faces the cell membrane is Trans Face and is the exit face where vesicles leave the Golgi and move to their targets, including the exterior of the cell. As the last station of the Golgi complex, the trans-Golgi network (TGN) plays a pivotal role in directing proteins in the secretary pathway to the appropriate cellular destination. Proteins synthesized on membrane-bound ribosomes are transported through the Golgi apparatus and, on reaching the trans-Golgi network, are sorted for delivery to various cellular destinations. Sorting involves the assembly of cytosol-oriented coat structures which preferentially package cargo into vesicular transport intermediates. Protein sorting into different transport vesicles requires specific interactions between sorting motifs on the cargo molecules and vesicle coat components that recognize these motifs.

The Golgi apparatus is integral in modifying, sorting, and packaging macromolecules for cell secretion (exocytosis) or use within the cell.

It primarily modifies proteins delivered from the rough endoplasmic reticulum, then sends the modified macro-molecules to different parts of the cell or outside of the cell.

It is also involved in the transport of lipids around the cell, and the creation of lysosomes.

In this respect it can be thought of as similar to a post office; it packages and labels items which it then sends to different parts of the cell.

FUNCTIONS

GOLGI APPARATUS

The Golgi plays an important role in the synthesis of proteoglycans, which are molecules present in the extracellular matrix of animals.

It is also a major site of carbohydrate synthesis.

A newly characterized protein, GAAP (Golgi anti-apoptotic protein), almost exclusively resides in the Golgi and protects against cell destruction known as apoptosis by an as-yet undefined mechanism.

Sometimes vital proteins needed in the rough endoplasmic reticulum are transported along with the other proteins in the Golgi complex. The Golgi complex has a mechanism for trapping them and sending them back to the rough endoplasmic reticulum.

FUNCTIONS

GOLGI APPARATUS

Mitochondria (singular, mitochondrion) – are typically tubular or rod-shaped organelles found in the cytoplasm of most cells and produces enzymes for the metabolic conversion of food to energy.

Mitochondria are responsible for converting nutrients into the energy-yielding molecule adenosine triphosphate (ATP) to fuel the cell's activities. This function, known as aerobic respiration, is the reason mitochondria are frequently referred to as the powerhouse of the cell. 

MITOCHONDRIA

MITOCHONDRIA

FUNCTION

MITOCHONDRIAEnergy conversion

1. The most prominent roles of mitochondria are to produce the energy currency of the cell, ATP, through respiration, and to regulate cellular metabolism.

2. A dominant role for the mitochondria is the production of ATP, as reflected by the large number of proteins in the inner membrane for this task.

MITOCHONDRIA STRUCTUREA mitochondrion contains outer and inner membranes composed of phospholipid bilayers and proteins. The two membranes have different properties. Because of this double-membrane organization, there are five distinct parts to a mitochondrion. They are:

What are Lysosomes? Created in the ER, or Endoplasmic Reticulum and sent to the Golgi Apparatus. Lysosomes are small organelles filled with digestive enzymes. Located in the cytoplasm (portion of cell outside of the nucleus) of animal eukaryotic cells The “janitors of the cell”

The Job of Lysosomes Responsible for the break down of lipids, carbohydrates, and proteins to be used by the cellAttach and release their enzymes, which break down the complex sugars and proteinsBreak down organelles that are no longer usefulRemove “junk” that may accumulate in the cell (this prevents diseases)

A closer look at Lysosomes!

Interesting FactsThere are over 50 classified diseases due to Lysosomes not functioning properly. To name a few..-Lipidoses-Lysosomal Transport Disease-Glycogen Storage Disease type IIThe word Lysosome comes from two Greek words- Lysis meaning destruction, and Soma meaning body. - Lysosomes contain over 3 dozen different types of enzymes

What are Peroxisomes?Small organelles found in both animal and plant cellsFound in free floating cytoplasm Contain at least 50 enzymes Produce hydrogen peroxide

The Job of PeroxisomesBreaking downEnzymes in peroxisomes break down long chain fatty acids through oxidationProduce a great deal of metabolic energy supplements Abundant in organs such as the liver, where lipids are stored, broken down, and synthesized.

The Job of Peroxisomes cont.Building upProduce chemicals as well as breaking them down Make cholesterol in animal cells and produce bile in liver cellsContain enzymes for making phospholipids

A closer look at Peroxisomes!

A Plastid is a….Major organelle of plant and algal cellsSite of manufacture and storage of important chemical compoundsHas circular, dsDNA copiesReplicates autonomously of the cellThought to have been originated from endosymbiotic bacteria

Plastid genes show maternal inheritance

Derived from proplastids in meristem

Have diverse functionsChloroplasts – green plastids – for photosynthesisChromoplasts – coloured plastids – for pigment synthesis and storageGerontoplasts – control dismantling of photosynthetic apparatus during senescenceLeucoplasts – colourless plastids – monoterpene synthesis

Leucoplasts include amyloplasts (starch), elaioplasts (fats), proteinoplasts (proteins) and tannosomes (tannins)

120-130 plastid genes

Are densely packed and fall into 2 categories:Photosynthesis-related genesGenetic system genes - genes for rRNAs, tRNAs, ribosomal proteins and RNA polymerase subunits

1. Vacuoles are most important in plant cells2. Vacuoles have a similar function in fungal

cells as plant cells3. Contractile vacuoles are found in protists

and are most important in fresh water organisms

4. Vacuoles are important for storage in cells5. Vacuoles collect harmful waste and

dispose of it6. Animal cells have vesicles, not vacuoles

VACUOLES

Structure

Vacuoles are organelles found in cells. They store various substances essential to the life of the cell. They also store waste to later remove from the cell.

VACUOLES

General FunctionVacuoles, like vacuums, remove waste products harmful to the cell. In addition, they store water and essential nutrients for later use. For this reason, they are called “storage bubbles”(source 5) or “storage bins”(source 4).

VACUOLES

The centrosome, also called the "microtubule organizing center", is an area in the cell where microtubles are produced.

Within an animal cell centrosome there is a pair of small organelles, the centrioles, each made up of a ring of nine groups of microtubules. There are three fused microtubules in each group.

The two centrioles are arranged such that one is perpendicular to the other.

During animal cell division, the centrosome divides and the centrioles replicate (make new copies). The result is two centrosomes, each with its own pair of centrioles. The two centrosomes move to opposite ends of the nucleus, and from each centrosome, microtubules grow into a "spindle" which is responsible for separating replicated chromosomes into the two daughter cells.

CENTRESOMES

THANK YOU