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CELL Topics Cell structure Cell function Cellular organization

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Presentation on theme: "CELL Topics Cell structure Cell function Cellular organization"— Presentation transcript:

1 CELL Topics Cell structure Cell function Cellular organization
Cellular metabolism (by Dr. Amjad Ali Khan)

2 Introduction The cell is the structural and functional basic unit of life. It was discovered by Robert Hooke and is the functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life.

3 Introduction Some organisms, such as most bacteria, are unicellular (consist of a single cell). Other organisms, such as humans, are multicellular. Humans have about 100 trillion or 1014 cells; a typical cell size is 10 µm (micrometer) and a typical cell mass is 1 nanogram.

4 Types of Cells There are two types of cells: prokaryotic and
eukaryotic Prokaryotic cells are usually independent, while eukaryotic cells are often found in multicellular organisms.

5 Prokaryotic Cell The prokaryote cell is simpler, and therefore smaller, than a eukaryote cell, lacking a nucleus and most of the other organelles of eukaryotes. Nuclear material of prokaryotic cell consist of a single chromosome which is in direct contact with cytoplasm. Here the undefined nuclear region in the cytoplasm is called nucleoid.

6 On the outside, flagella and pili may be present
On the outside, flagella and pili may be present. These facilitate the movement and communication between cells. Enclosing the cell is the cell envelope – generally consisting of a cell wall covering a plasma membrane

7 General structure of a Prokaryotic cell

8 Eukaryotic Cell Eukaryotic cells are far more advanced and complex than a Prokaryotic cell. Eukaryotic cell can be as much as 1000 times bigger in size than a prokaryotic cell. eukaryotic cells contain membrane-bound compartments (organelles) in which specific metabolic activities take place.

9 Most important among these is a nucleus, a membrane bound compartment that contains DNA. This nucleus gives the eukaryote its name, which means "true nucleus. There are some differences in the structure and function of animal and plant cells. Though both cells are eukaryotic.

10 In the cytoplasm the eukaryotic cell contains many organelles such as:
Mitochondria Endoplasmic reticulum (rough and smooth) Golgi bodies Lysosomes Peroxisomes Ribosomes Chloroplast (found in plant cells) Vacuole centriole

11 Simple structure of a eukaryotic cell

12 Eukaryotic cell organelles
There are several types of organelles in a cell. Some (such as the nucleus and golg apparatus) are typically solitary, while others (such as mitochondria, peroxisomes and lysosomes) can be numerous (hundreds to thousands). The cytosol is the gelatinous fluid that fills the cell and surrounds the organelles.

13 Nucleus The cell nucleus is the most conspicuous organelle found in a eukaryotic cell. It contains the chromosomes, The nucleus is spherical and separated from the cytoplasm by a double membrane called the nuclear envelope. The nuclear envelope isolates and protects a cell's DNA

14 The nucleolus is a specialized region within the nucleus where ribosome subunits are assembled.
In prokaryotes, DNA processing takes place in the cytoplasm.

15 Mitochondria Mitochondria play a critical role in generating energy in the eukaryotic cell so it is also called “power house of a cell. Mitochondria are self-replicating organelles that occur in various numbers, shapes, and sizes in the cytoplasm of all eukaryotic cells. Mitochondria multiply by splitting in two. Respiration occurs in the cell mitochondria.

16 General structure of Mitochondria

17 Endoplasmic reticulum
The endoplasmic reticulum (ER) is the transport network for molecules targeted for certain modifications and specific destinations. The ER has two forms: the rough ER, which has ribosomes on its surface and secretes proteins into the cytoplasm, and the smooth ER, which lacks them.

18 Endoplasmic Reticulum

19 Golgi apparatus The primary function of the Golgi apparatus is to process and package the macromolecules such as proteins and lipids that are synthesized by the cell. It is particularly important in the processing of proteins for secretion. It consists of -cis and -trans faces

20 Golgi apparatus

21 Ribosomes The ribosome is a large complex of RNA and protein molecules. They each consist of two subunits, and act as an assembly line where RNA from the nucleus is used to synthesize proteins from amino acids.

22 Ribosomes Ribosomes can be found either floating freely or bound to endoplas-mic reticulum in eukaryotes, or the cell membrane in prokaryotes). In prokaryotic cells 70S ribosomes are present while in eukaryotic cells 80S ribosomes are present

23 Lysosomes Lysosomes contain digestive enzymes. They digest excess or worn-out organelles, food particles, and engulfed viruses or bacteria. These organelles (lysosomes and peroxisomes) are often called a "suicide bag" because of their ability to detonate and destroy the cell.

24 Vacuoles Vacuoles store food and waste. Some vacuoles store extra water. The vacuoles of eukaryotic cells are usually larger in those of plants than animals.

25 Centriole In animal cells, centrioles are short cylinders present near the nucleus. There is always one pair of centrioles near the nucleus. Before a cell divides, the centrioles duplicate. During cell division, the pair of centrioles separate so that each cell gets one pair of centrioles.

26 The cytoskeleton Several types of filamentous proteins form a cytoskeleton that helps maintain the cell’s shape and either anchors the organelles or assists their movement. The cytoskeleton includes microtub-ules and actin filaments.

27 MICROTUBULES Microtubules are shaped like thin cylinders and are several times larger than actin filaments. Microtubules are made up of tubulin. Microtubules can assemble and dis-assemble. It is well known that during cell division, microtubules form spindle fibres, which assist the movement of chromosomes

28 Cilia and Flagella Cilia and flagella are projections of cells that can move. Cilia are short (2-10µm) while flagella are longer about 200 µm. Cells that have these organelles are capable of self movement or moving material along the surface of the cell.

29 Cellular metabolism Cellular metabolism includes all the chemical reactions that occur in a cell. Quite often these reactions are organized in a metabolic pathways, which can be shown as: A B C D

30 A B C D The letters A,B,C,D are the reactants and products whereas 1,2,3 are the enzymes which take part in the reactions. Every reaction in a cell requires a specific enzyme

31 Different types of enzymes present in a cell which act on different substrates are:
Substrate Enzyme Lipid lipases Protein protease Urea urease Maltose maltase Lactose lactase

32 General structure of a Plant cell

33 Difference between prokaryotic and eukaryotic cell
Typical organisms bacteria, archaea plants, animals, fungi Size of cell 1 – 10 µm 10 – 100 µm Type of nucleus No real nucleus True nucleus Cell organelles (mitochnodria, chloroplast, ER, golgi bodies, lysosomes etc) Absent present Ribosomes 70S 80S Cell division Binary fission Mitosis and meiosis DNA Circular , in cytoplasm In chromosomes, in nucleus

34 Difference and common between animal cell and plant cell
Structure Animal Cell Plant cell Cell membrane yes Yes nucleus Nucleolus Ribosomes ER Golgi bodies Centrioles No Cell wall Mitochnondria Chloroplast One big vacuole cytoskeleton


36 Cell theory The cell theory, first developed in 1839 by Schleiden and Schwann, states that all organisms are composed of one or more cells, that all cells come from pre-existing cells, that vital functions of an organism occur within cells,

37 Cell theory and that all cells contain the hereditary information necessary for regulating cell functions and for transmitting information to the next generation of cells. The word “Cell” was first coined by Robert Hooke in 1665

38 Thank you

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