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 e.t.c
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).
Oh yeah! Some HISTORY for you
I am sure you are all asking yourselves, “Who was the first person to look at cells.” Well thanks for asking! I will tell you.
In the 1665 there was a man named Robert Hooke. Robert lived in Britain and was a scientist. He was the first person to observe cells.
Robert took a piece bark from an old oak tree and looked at it through a microscope.
Robert Hooke Microscope used by Robert Hooke Modern day microscope
The bark looked like it was made up of many small rooms (kind of like a house with many bedrooms). He named the rooms, or structures, he saw under the microscope cells.
This is how the word cells came to be!! Exciting stuff isn’t it!!
Cork cells under microscope
After the discovery of cell by hooke other people made discoveries about cells. Some of them are :-
Antony van Leeuwenhoek discovered the first living cell(remember the cells that hooke saw were dead ones )by inventing a special microscope in 1674.
Matthias Jakob Schleiden discovered cell wall in plant cell in 1838.
History Continued (getting bored! Don’t worry this the last slide of history )
In 1839 Theodore Schwann observed cell membrane in an animal cell.
Robert brown discovered nucleus in 1831
Purkinje discovered protoplasm in 1839
Rudolph Virchow stated that all cells are formed from pre-existing cells.
Watson and crick discovered DNA.
Schleiden and Schwann proposed the “ CELL THEORY ” (what’s that ? Have patience !)
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
Organelles of Cells and their Basic Functions
It has double membrane organelle
central cavity is filled with matrix
inner membrane folds known as cristae
large surface area for chemical reactions of cellular respiration
generation of ATP
“ powerhouse of cell”
increases with need for ATP
They have circular DNA with 37 genes
only inherited from mother
Cross-section of a mitochondria
Now what is ATP ?
ATP(adenosine triphosphate) is the source of energy for the cells to perform its functions
Nucleus : The nucleus is a structure usually located near the center of the cell. It controls the activities of the cell. The nucleus is a home to the cell’s chromosomes . What are chromosomes you ask?
Chromosomes : They are genetic structures that contain information to make new cells. Basically, the instructions for how to make new cells. They contain DNA responsible for hereditary characters of the cell.
Nucleolus : This structure is found inside the nucleus. It is responsible for making ribosomes. We will get to this term in a bit. Thanks for your patience!
Nucleolus inside a nucleus
Continued Nuclear membrane : This surrounds and protects the nucleus. The nucleus has its own protector. This membrane is double-layered.
Plastids- they are of 3 kinds-
1.chloroplast-helps to make food for the plant by photosynthesis.
2.chromoplast-gives colour to the some parts of plants like flowers
Glyoxysome-breakdown of fatty acids to sugars
Ribosomes -Ribosome turns RNA (Ribonucleic acid) into protein. The ribosome is basically the storage space for energy. in other words it releases and holds in energy for the cell. They are the structural support, and the catalyst for protein synthesis. :)he
Endoplasmic Reticulum-Say it with me “En-do-plas-mic ri-tic-eww-lum.”
Now say it 5 times fast….no just kidding!
it is made up of 2 parts -
1. SER(smooth endoplasmic reticulum)-it helps in lipid synthesis.
2. RER(rough endoplasmic reticulum)- it helps in protein synthesis and sends them to different parts of the cell. It is rough because it has ribosomes attached to its surface.
Golgi Apparatus-delivery system for the cell and also helps in manufacturing of 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
digest foreign substances
autophagy (recycles own organelles)
Autolysis(Lysosomal digestion of the cell after death)
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.
Peroxysomes-help in performing oxidative reactions in a cell.
Centriole- helps in cell division by forming a milotic spindle also know as spindle fiber apparatus. In plants polar caps do the same function.
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
E.g.:-Fungi, Plants, Animals
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
A prokaryotic cell
Greek for “small stick”
Most Abundant organism
Found in all Media
Many are Pathogens
Move by Flagella or by Gliding
Beneficial in Everyday Needs
Bacterial cells Escherichia coli cells
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.
They are animal like and Motile
Feed by Phagocytosis (what's that! Wait for the next slide)
Uses photosynthesis for its nutrients
Some motile, some are not
Phago and pinocytosis
Phagocytosis is the ingestion or eating of large particles by living cells
Pinocytosis is the intake of fluid by the cell also known as cell-drinking.
All come from a common
Thought to be more related to animals than plants
Most are symbiotic
Reproduce sexually or asexually
Many are used in everyday human life
Fly Agaric fungi Yeast cells
The Plant Cell
Has a cell wall made of cellulose
Has a large central vacuole
Contains Chloroplasts which contain Chlorophyll
The cells differentiate in to dermal tissue, vascular tissue, or ground tissue
The three main structures for a plant cell
Cell Wall : This wall provides extra support for the cell and gives it a shape. In other words, if there was no cell wall then the cell would have no shape.
Chloroplasts : These make food for the plant. They are green.
Chlorophyll : This is very important in making the food for the plant. This structure takes in sunlight and makes sugar for the plant to eat and become green.
Cell wall in plant cell Chloroplast Plant cells
Example of Whole Plants
The Animal Cell
Animals are made up of many different types of cells. The structures I am about to tell you about are found in a typical animal cells.
Please note: Not all animal cells contain all the same structures.
Thank you for noting!
Unicellular and Multicellular
Lack a cell wall and chloroplasts.
They have small vacuoles
Appear spherical in shape
Contains a variety of organelles
They cannot produce their own food.
The Exception: Viruses
Latin for “poison”
Does not meet all the criteria of “Life”
Not made up of cells
Contains DNA or RNA, but not usually both
Require a host to replicate
Causes the common cold, the flu, chickenpox, AIDS, bird flu etc.
Some uses e.g. –bacteriophage used to kill bacteria
Structure of a virus Bacteriophage virus attacking a bacterial cell H1N1 virus (influenza)