• All living things are made up of cells.

• Cells are the basic structural and functional unit of life.

• All cells come from pre-existing cells

CELL

What’s inside a cell?Cells are the building blocks of all living organisms. Individual cells are classified as living things, and there are millions of organisms that are unicellular across the planet.As they are living units, cells consequently need energy, and therefore respire to survive. Parts of the cell, called organelles, work like organs of a body. Energy for the cell to process can be provided by the cell, such as through photosynthesis in plants, or absorbed into the cell through cell membranes and then processed within it by the mitochondrion. Single cells operate like this, and there are billions of unicellular organisms that survive independently or within multicellular organisms. These single cell organisms are generally prokaryotic cells, which are much smaller and have fewer organelles, most importantly lacking a nucleus. Multicellular organisms are primarily made up of eukaryotic cells which are more complex and can therefore specialize so the organism can become more complex. They do this by grouping together to form tissues, which then group to form organs within the organism.

CELL COMPOSITION

• ProtoplasmThe term "protoplasm," from proto, first, and

plasma, formed substance, was coined by the botanist Hugo von Mohl, in 1846, for the "tough, slimy, granular, semi-fluid“

It was used 1839 by Czech physiologist Johannes Evangelista Purkinje (1787-1869) to denote the gelatinous fluid found in living cell. 

Compose of inorganic and organic compounds like carbohydrates, proteins, lipids and nucleic acids

CELL MEMBRANE

• Plasma membrane / plasmolemma• Bi-lipid layer• Semi permeable • Serves as boundary between the outside

environment and the inside environment• Outer membrane of cell that controls movement

in and out of the cell

Fluid Mosaic Model of Cell Membrane-S.J.Singer and Garth Nicolson in 1972

Cell Wall

The cell wall is a tough, flexible but sometimes fairly rigid layer that surrounds sometypes of cells. It is located outside the cell membrane and provides these cells withstructural support and protection, in addition to acting as a filtering mechanism. A majorfunction of the cell wall is to act as a pressure vessel, preventing over-expansion whenwater enters the cell. Cell walls are found in plants, bacteria, fungi,algae, andsome archaea. Animals and protozoa do not have cell walls.

Amorphous, gel sol nature of substance.Allows movement of various substances inside the cytoplasm due to cytoplasmic streaming.In eukaryotic cell, cytoplasm is embedded with many organelles.Transparent ground substance.The cytoplasm has three major elements; the cytosol, organelles and inclusions.It is about 80% water and usually colorless.

The 2 main functions of Nucleus:•Helps in reproduction.•Regulates the chemical activities of cell.

Nuclear Membrane:oDouble membranous cover .oEncloses nucleoplasm (chromatin & Nucleolus).oBears many fine pores called nuclear pore.

Nuclear Pore:oOccupies 10% of total area of nucleus.oPermit the entry and exit of various substances from cytoplasm to nucleoplasm and vice versa.

Chromatin:oEntangled network of thread – DNA & Protein.oIn dividing cells, chromatin fibre is coiled and condensed to form chromosomes-(DNA + Protein) = Histone.

Endoplasmic ReticulumThe endoplasmic reticulum (ER) is a type of organelle in the cells of eukaryotic organisms that forms an interconnected network of flattened, membrane-enclosed sacs or tubes known as cisternae. The membranes of the ER are continuous with the outer membrane of the nuclear envelope. Endoplasmic reticulum occurs in most types of eukaryotic cells, including the most primitive Giardia, but is absent from red blood cells and spermatozoa. There are two types of endoplasmic reticulum, rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum (SER). The outer (cytosolic) face of the rough endoplasmic reticulum is studded with ribosomes that are the sites of protein synthesis.

The rough endoplasmic reticulum is especially prominent in cells such as hepatocytes where active protein synthesis occurs. The smooth endoplasmic reticulum lacks ribosomes and functions in lipid metabolism, carbohydrate metabolism, and detoxification and is especially abundant in mammalian liver and gonad cells. The lacey membranes of the endoplasmic reticulum were first seen in 1945 by Keith R. Porter, Albert Claude, Brody Meskers and Ernest F. Fullam.

Smooth endoplasmic Reticulum

• Branching canal• No ribosomes• Transport for large

molecules• Stores calcium ions in

muscle cells• Found in both animal

and plant cells• Consists of tubules

that are located near the cell periphery.

Rough Endoplasmic Reticulum

• Contains attached ribosomes

• Transport ribosomes• Synthesis, storage and

transfer of proteins• Manufacture of

lysosomal enzymes• Provides skeletal

support to cell

LysosomesDerived from greek word ‘lysis’ means ‘to loosen’ and ‘soma’ means ‘body’.This was discovered by Christian de Duve.They are also called Digestive bags or Suicidal bags.They are single membrane bounded vesicles formed from Golgi bodies.Contains more than 40 enzymes .Clears out foreign bodies/food particles by digesting it.Digests damaged/worn out organelles of their own.Described as ‘stomach of the cell’.The size of lysosomes varies from 0.1–1.2 μm.They are the recycling units of cell.

MITOCHONDRIA The word comes from the greek word ‘mitos’ means ‘thread’ and ‘chondrion’ means ‘granule’.Mitochondria range from 0.5 to 1.0 micrometer in diameter.They are called the ‘Power House of Cell’.They generate ATP-Adenosine Triphosphate.It is the organelle of respiration.Double membrane bounded membrane.The number of mitochondria in a cell varies widely by the organism and tissue type.

PLASTIDS•They are the site for the manufacture and storage of important chemical compounds used by cell.•Present in plant cells and absent in animal cells except Euglena.•Plastids with pigments – Chromoplasts 1. Chloroplasts-Green 2. Chromoplasts-Orange/Yellow•Plastids without pigments- Leucoplasts –storage of reserved food.

GOLGI APPARATUS

Discovered by Camillo Golgi.

After maturity, the organelles divides and forms either vacuole or

lysosomes.

Function: Packaging, modification and dispatching of various

substances.

It forms lysosomes and vacuoles.

In plant cells, they are called dictyosomes.

The Cisternae stack has four functional regions: the cis-golgi,

media-golgi, endo-golgi and trans-golgi network.

VACUOLE

Single membranous sacs meant for storage of solids and liquids.Vacuoles are smaller and few in animal cells and it is large and more in plant cells.Occupies 50%-90% of cell volume.Storage of various substances Provides turgidity and rigidity to cells.They are of 2 types:-1. Food vacuoles-digesting food.2. Contractile vacuoles-storage and release of equess.