Cell - Basic Structure, Organelles and Overview

The basic of Cell for students.
created and upload by Saikat Roy.
Radiation therapist, Tata Medical Center.

1. The Human Cell Saikat Roy

2. The  cell  was first  discovered  and named by Robert Hooke in 1665. The dead  cell  walls of plant  cells  (cork)  Sir Robert Hooke Microscope used  by Robert Hooke The father of modern cell Theory is  Robert Hooke . Saikat Roy

3. Modern Cell Theory All known living things are made up of cells. The cell is structural & functional unit of all living things. All cells come from pre-existing cells by division. (Spontaneous Generation does not occur). Cells contains hereditary information which is passed from cell to cell during cell division. All cells are basically the same in chemical composition. All energy flow (metabolism & biochemistry) of life occurs within cells. Cytology is a branch of science concerned with a study of cells  Saikat Roy

4. we can divide the cell in to four principal parts Plasma membrane It is the outer lining, limiting membrane separating the cell internal parts from extra cellular materials & external environment.  Cytoplasm Cytoplasm is the substance that surrounds organelles and is located between the nucleus and plasma membrane  Organelles  These are permanent structures with characteristic morphology that are highly specialized in specific cellular activity.  Inclusions  They are the secretions and storage products of cells.  Extra cellular materials are also referred to as the matrix, which are substances external to the cell surface. Saikat Roy

5. Plasma membrane is a thin outer membrane, which maintains the integrity of the cell. It keeps the cell and its contents separate and distinct from the surrounding. Functions:  Separate the cytoplasm inside a cell from extra cellular fluid.  Separate cell from one another.  Provide an abundant surface on which chemical reaction can occur.  Regulate the passage of materials in to and out of cells. It also let some things in and keeps others out. The quality selective permeability  Specification: It is a double layered. Measuring about 4.5 nm. Made of phospholipids, cholesterol, glyco -lipid, & carbohydrate (oligosaccharides). Plasma Membrane Saikat Roy

6. Cytoplasm is a matrix or ground substance in which various cellular components are found.  It is thick semi transparent , elastic fluid containing suspended particles and a series of minute tubules and filaments that form cytoskeleton. Water constitutes 75-90% of the cytoplasm. It also contains solid components, proteins, carbohydrates, lipids and inorganic substances.  Cytoplasm Cell membrane Cytoplasm Saikat Roy

7. Organelles Nucleus Oval in shape and is the largest structure in the cell. Contain the hereditary factor in the cell.  Hence it controls cell activity & structure Nuclear membrane: The nucleus separated from other cell structure by double membrane called nuclear membrane.  Pores over the nuclear membrane allow the nucleus to communicate with the cytoplasm.  Nucleoplasm: In the nucleus a jelly like fluid that fill the nucleus is karylymph ( neucleoplasm ), which contain the genetic material called chromosome.  Nucleolus: Nucleus also contain dark, somewhat spherical, non-membrane bound mass called nucleolus. It contains DNA, RNA and protein, which assist in the construction of ribosome Most cell contain single nucleus but some like matured Red Blood cell do not contain. However Muscle cell contain several nucleuses.

8. Organelles Ribosome Tiny granules, composed of Ribosomal RNA (rRNA). They are site of protein synthesis Together with a structure known as messenger RNA (a type of nucleic acid) ribosomes form a structure known as a polyribosome which is important in protein synthesis. Diagram of several ribosomes joined together on a strand of mRNA to form a polyribosome. Saikat Roy

9. Organelles Endoplasmic Reticulum The ER has a double membrane consisting of a network of hollow tubes, flattened sheets, and round sacs. These flattened, hollow folds and sacs are called cisternae. The ER is located in the cytoplasm and is connected to the nuclear envelope. Smooth Endoplasmic Reticulum : does not have any ribosomes attached. It is involved in the synthesis of lipids, including oils, phospholipids and steroids. It is also responsible for metabolism of carbohydrates, regulation of calcium concentration and detoxification of drugs. Rough ER : is covered with ribosomes giving the endoplasmic reticulum its rough appearance. It is responsible for protein synthesis and plays a role in membrane production. The folds present in the membrane increase the surface area allowing more ribosomes to be present on the ER, thereby allowing greater protein production. Saikat Roy

10. Organelles Golgi Complex Near to the nucleus. It consist 4-8 membranous sacs. It process, sort, pack & deliver protein to various parts of the cell.  Saikat Roy

11. Organelles Mitochondrion a small, spherical, rod shaped or filamentous structure. This organelle generates the cell's supply of chemical energy by releasing energy stored in molecules from food and using it to produce ATP (adenosine triphosphate) Each mitochondria posses two membrane, one is smooth (upper) membrane and the other is arrangedwith series of folds called cristae. The central cavity of a mitochondrion enclosed by the inner membrane is the matrix Saikat Roy

12. Organelles Lysosomes They are formed from Golgi complexes & have single membrane. They contain powerful digestive (hydrolytic  enzyme) capable of breaking down many kinds of molecules. The lysosomal enzyme believed to be synthesized in the granular endoplasmic reticulum and Golgi complex.  Saikat Roy

13. Organelles Centrosome A dense area of cytoplasm generally spherical and located near the nucleus it contain centrioles. It also contains DNA that controls their replication. Centrosmes are made of microtubules, which seam drinking straws. They are Involved in the movement of chromosome during cell division.   Two centrioles arranged perpendicular to each other are referred to as a centrosome. Microscopic view of centrosome Saikat Roy

14. Organelles Cyto Skeleton The cytoplasm has a complex internal structure consisting of a series of exceedingly small microfilaments, microtubule & intermediate filaments together referred to as the cyto -skeleton. Saikat Roy

15. Organelles Cilia/flagella Made of microtubules. When they are beating forms rhythmic movement. They are found in female reproductive organ and upper respiratory tube.   Saikat Roy

16. Organelles Cilia/flagella Made of microtubules. When they are beating forms rhythmic movement. They are found in female reproductive organ and upper respiratory tube.   Saikat Roy

17. Complete Diagram of Human Cell Saikat Roy