SCIENCEPRESENTATIO

N

CELLS

= structural and functional unit of life

Acknowledgement I'm Priya Mishra of class IX-C would sincerely

like to thanks Mr. S. Mandal our science teacher who has been a contact source of inspiration and guidance throughout this presentation. Mr. S. Mandal acting as guiding spirit behind the completion of this presentation.

With thanks

Priya Mishra

Contents Cell Cell theory Cell organelles and their functions Types of cell

Cell

Cell: A cell is a basic unit of structure and function of life. In other words, cells make up living things and carry out activities that keep a living thing alive. We can find cells almost anywhere on earth e.g.:- In the air, inside us, plants etc.

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What makes a cell? A cell is a living thing. Cells are able to make more cells like

themselves. New cells can only come from existing

cells (cells that are already existing).

Microscope used byRobert Hooke

The cell theory All organisms are made of one or more

cells The cell is the basic unit of all living

things All cells come from pre-existing cells

Cell organelles and their functionsMitochondria It has double membrane organelle central cavity is filled with matrix inner membrane folds known as cristae Functions- generation of ATP “powerhouse of cell” Mitochondria self-replicate increases with need for ATP

Nucleus- The nucleus is the control center of the cell. It is the largest organelle in the cell and it contains the DNA of the cell. The DNA of all cells is made up of chromosomes.

  DNA (Deoxyribonucleic Acid) contains all the information for

cells to live, perform their functions and reproduce. 

Inside the nucleus is another organelle called the nucleolus. The nucleolus is responsible for making ribosome.

The circles on the surface of the nucleus are the nuclear pores. These are where ribosome, and other materials move in and out of the cell.

Plastids- they are of three kinds- 1.chloroplast-helps to make food for the

plant by photosynthesis.

2.chromoplast-gives color to the some parts of plants like flowers

3.leucoplasts-store food

Ribosome- Organelles that help in the synthesis of proteins. Ribosome are made up of two parts, called subunits. 

They get their names from their size. One unit is larger than the other so they are called large and small subunits. 

Both these subunits are necessary for protein synthesis in the cell. When the two units are docked together with a special information unit called messenger RNA, they make proteins. 

Some ribosome are found in the cytoplasm, but most are attached to the endoplasmic reticulum. While attached to the ER, ribosome make proteins that the cell needs and also ones to be exported from the cell for work elsewhere in the body.

Endoplasmic reticulum (ER)- It is a network of membranes throughout the cytoplasm of the cell. There are two types of ER.

When ribosome are attached it is called rough ER and smooth ER when there are no ribosome attached. 

The rough endoplasmic reticulum is where most protein synthesis occurs in the cell. The function of the smooth endoplasmic reticulum is to synthesize lipids in the cell. The smooth ER is also helps in the detoxification of harmful substances in the cell.

Golgi complex- It is organelle in the cell that is responsible for sorting and correctly shipping the proteins produced in the ER. 

Just like our postal packages

which should have a correct shipping address, the proteins produced in the ER, should be correctly sent to their respective address. 

In the cell, shipping and sorting done by the Golgi complex. It is a very important step in protein synthesis.

If the Golgi complex makes a mistake in shipping the proteins to the right address, certain functions in the cell may stop. 

• Lysosomes-• They are Membranous

vesicles and formed in Golgi complex

• They are filled with digestive enzymes and pump in H+ ions until internal pH reaches 5.0

• Functions -• digest foreign substances • autophagy (recycles own

organelles) • Autolysis(Lysosomal

digestion of the cell after death)

Steps in lysomal formation

(1) The ER and Golgi apparatus make a lysosome

(2) (2) The lysosome fuses with a digestive vacuole(3) Activated acid

(3) hydrolases digest the contents

Cilia are thread-like projections of certain cells that beat in a regular fashion to create currents that sweep materials.                                          

• Vacuoles-These are fluid-filled structures used to store different substances and help in osmo-regulation. In animal cells there are often many small vacuoles. Plants have large vacuoles.

Vesicles- This term literally means "small vessel". This organelle helps store and transport products produced by the cell.

The vesicles are the transport and delivery vehicles like our mail and  Federal Express trucks. Some vesicles deliver materials to parts of the cell and others transport materials outside the cell in a process called exocytosis.

Plasma membrane: The plasma membrane surrounds the cell. It regulates the movement of substances in or out of the cell. It is made up of a lipid and protein bi-layer. Think of the membrane as a gatekeeper, it only allows some materials to pass through, but keeps others out.

Cytoplasm: This is a gel-like fluid, that takes up most of the space inside a cell. Cytoplasm kind of looks like jelly.

Types of

cells

Types of cell:- Prokaryotic cells- E.g.:-Bacteria Eukaryotic cells- Unicellular E.g.:-Protists Multi-cellular E.g.:-Fungi, Plants, Animals

Prokaryotic cell

Prokaryotes – the meaning of their name is pro-primitive karyon-nucleus.

They are small in size and they don’t have a properly arranged nucleus.

They have single chromosome. Nucleolus is also absent. Generally they are pathogens. They have circular or coiled DNA

Prokaryotic cell

Eukaryotic cell Eukaryotes – the meaning of their name

is eu- developed karyon-nucleus. It has membrane bound nucleus. It contains many organelles. It has linear DNA. Membrane bound organelles are

present. They have more than 1 chromosome

Eukaryotic cell

Feature Prokaryote Eukaryote

Size Small about 0.5 micrometers

Up to 40 micrometers

Genetic material

Circular DNA (in cytoplasm)

DNA in form of linear chromosomes ( in nucleus)

OrganellesFew present, none membrane bound

Many organelles:• Double membranes e.g.:

nucleus, mitochondria & chloroplasts

• Single membrane e.g.: GA, ER & lysosomes

Cell wallsRigid formed from glycoproteins (mainly murein)

• Fungi: rigid, formed from polysaccharide, chitin.

• Plant: rigid, formed from polysaccharides. E.g.: cellulose.

• Animals no cell wall Ribosome’

s 70s 80s

Differences